[PATCH 00/14] sched: SCHED_DEADLINE v8

[PATCH 00/14] sched: SCHED_DEADLINE v8

[Juri Lelli]

Hello everyone,

here we go with a new version of the SCHED_DEADLINE patchset (v8). I know that
it has been a while since I released last version [1], but I thought not to
spam the mailing list with simple updates. Well... this IS basically an update
to 3.12-rc5, but it comes right before the next Kernel Summit and Real Time
Linux Workshop and, since I'll be present at both events, it is probably time
to fire-up the discussion again.

Moreover, interesting news:

 - a better mechanism for coordinating mutually exclusive access to critical
   sections is coming soon (we wrote a paper about it for RTLWS15 [2]);
 - the patchset is now available in the 3.4 and 3.10 Yocto kernels [3] (thanks
   a lot for this to Bruce Ashfield and Insop Song); even though it is hard to
   say how many new users we got with this, we can say that having
   SCHED_DEADLINE in Yocto provides availabily to OSVs like Wind River and
   others;
 - a european project has started (JUNIPER [4]) for which we will provide
   kernel level support based on this patchset (and we will soon have a real
   use case for it! yayyy! :)).

The development is taking place at:
   https://github.com/jlelli/sched-deadline

branch: sched-dl-V8 (this patchset on top of tip/master).

Check the repositories frequently if you're interested, and feel free to
e-mail me for any issue you run into.

Test applications:
  https://github.com/gbagnoli/rt-app 
  https://github.com/jlelli/schedtool-dl

Development mailing list: linux-dl; you can subscribe from here:
http://feanor.sssup.it/mailman/listinfo/linux-dl
or via e-mail (send a message to linux-dl-request@retis.sssup.it with
just the word `help' as subject or in the body to receive info).

The code was being jointly developed by ReTiS Lab (http://retis.sssup.it)
and Evidence S.r.l (http://www.evidence.eu.com) in the context of the ACTORS
EU-funded project (http://www.actors-project.eu) and the S(o)OS EU-funded
project (http://www.soos-project.eu/). Development is now supported by the
JUNIPER EU-funded project [4].

As usual, any kind of feedback is welcome and appreciated.

Thanks in advice and regards,

 - Juri

[1] http://lwn.net/Articles/376502, http://lwn.net/Articles/353797,
    http://lwn.net/Articles/412410, http://lwn.net/Articles/490944,
    http://lwn.net/Articles/498472, http://lwn.net/Articles/521091,
    http://lwn.net/Articles/537388

[2] https://www.osadl.org/?id=1743

[3] https://www.yoctoproject.org/

[4] http://www.juniper-project.org/page/overview

Dario Faggioli (9):
  sched: add sched_class->task_dead.
  sched: add extended scheduling interface.
  sched: SCHED_DEADLINE structures & implementation.
  sched: SCHED_DEADLINE avg_update accounting.
  sched: add schedstats for -deadline tasks.
  sched: add latency tracing for -deadline tasks.
  sched: drafted deadline inheritance logic.
  sched: add bandwidth management for sched_dl.
  sched: add sched_dl documentation.

Harald Gustafsson (1):
  sched: add period support for -deadline tasks.

Juri Lelli (3):
  sched: SCHED_DEADLINE SMP-related data structures & logic.
  sched: make dl_bw a sub-quota of rt_bw
  sched: speed up -dl pushes with a push-heap.

Peter Zijlstra (1):
  rtmutex: turn the plist into an rb-tree.

 Documentation/scheduler/sched-deadline.txt |  196 ++++
 arch/arm/include/asm/unistd.h              |    2 +-
 arch/arm/include/uapi/asm/unistd.h         |    3 +
 arch/arm/kernel/calls.S                    |    3 +
 arch/x86/syscalls/syscall_32.tbl           |    3 +
 arch/x86/syscalls/syscall_64.tbl           |    3 +
 include/linux/init_task.h                  |   10 +
 include/linux/rtmutex.h                    |   18 +-
 include/linux/sched.h                      |  122 +-
 include/linux/sched/deadline.h             |   24 +
 include/linux/sched/rt.h                   |    3 +-
 include/linux/sched/sysctl.h               |   11 +
 include/linux/syscalls.h                   |    7 +
 include/uapi/linux/sched.h                 |    1 +
 kernel/fork.c                              |    8 +-
 kernel/futex.c                             |    2 +
 kernel/hrtimer.c                           |    3 +-
 kernel/rtmutex-debug.c                     |    8 +-
 kernel/rtmutex.c                           |  164 ++-
 kernel/rtmutex_common.h                    |   22 +-
 kernel/sched/Makefile                      |    4 +-
 kernel/sched/core.c                        |  660 ++++++++++-
 kernel/sched/cpudeadline.c                 |  216 ++++
 kernel/sched/cpudeadline.h                 |   33 +
 kernel/sched/deadline.c                    | 1658 ++++++++++++++++++++++++++++
 kernel/sched/debug.c                       |   46 +
 kernel/sched/rt.c                          |    2 +-
 kernel/sched/sched.h                       |  150 +++
 kernel/sched/stop_task.c                   |    2 +-
 kernel/sysctl.c                            |    7 +
 kernel/trace/trace_sched_wakeup.c          |   45 +-
 kernel/trace/trace_selftest.c              |   28 +-
 32 files changed, 3343 insertions(+), 121 deletions(-)
 create mode 100644 Documentation/scheduler/sched-deadline.txt
 create mode 100644 include/linux/sched/deadline.h
 create mode 100644 kernel/sched/cpudeadline.c
 create mode 100644 kernel/sched/cpudeadline.h
 create mode 100644 kernel/sched/deadline.c

-- 
1.7.9.5

[PATCH 01/14] sched: add sched_class->task_dead.

[Juri Lelli]

From: Dario Faggioli <raistlin@linux.it>

Add a new function to the scheduling class interface. It is called
at the end of a context switch, if the prev task is in TASK_DEAD state.

It might be useful for the scheduling classes that want to be notified
when one of their task dies, e.g. to perform some cleanup actions.

Signed-off-by: Dario Faggioli <raistlin@linux.it>
Signed-off-by: Juri Lelli <juri.lelli@gmail.com>
---
 kernel/sched/core.c  |    3 +++
 kernel/sched/sched.h |    1 +
 2 files changed, 4 insertions(+)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 5ac63c9..850a02c 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1890,6 +1890,9 @@ static void finish_task_switch(struct rq *rq, struct task_struct *prev)
 	if (mm)
 		mmdrop(mm);
 	if (unlikely(prev_state == TASK_DEAD)) {
+		if (prev->sched_class->task_dead)
+			prev->sched_class->task_dead(prev);
+
 		/*
 		 * Remove function-return probe instances associated with this
 		 * task and put them back on the free list.
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index b3c5653..64eda5c 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -992,6 +992,7 @@ struct sched_class {
 	void (*set_curr_task) (struct rq *rq);
 	void (*task_tick) (struct rq *rq, struct task_struct *p, int queued);
 	void (*task_fork) (struct task_struct *p);
+	void (*task_dead) (struct task_struct *p);
 
 	void (*switched_from) (struct rq *this_rq, struct task_struct *task);
 	void (*switched_to) (struct rq *this_rq, struct task_struct *task);
-- 
1.7.9.5

[PATCH 02/14] sched: add extended scheduling interface.

[Juri Lelli]

From: Dario Faggioli <raistlin@linux.it>

Add the interface bits needed for supporting scheduling algorithms
with extended parameters (e.g., SCHED_DEADLINE).

In general, it makes possible to specify a periodic/sporadic task,
that executes for a given amount of runtime at each instance, and is
scheduled according to the urgency of their own timing constraints,
i.e.:
 - a (maximum/typical) instance execution time,
 - a minimum interval between consecutive instances,
 - a time constraint by which each instance must be completed.

Thus, both the data structure that holds the scheduling parameters of
the tasks and the system calls dealing with it must be extended.
Unfortunately, modifying the existing struct sched_param would break
the ABI and result in potentially serious compatibility issues with
legacy binaries.

For these reasons, this patch:
 - defines the new struct sched_param2, containing all the fields
   that are necessary for specifying a task in the computational
   model described above;
 - defines and implements the new scheduling related syscalls that
   manipulate it, i.e., sched_setscheduler2(), sched_setparam2()
   and sched_getparam2().

Syscalls are introduced for x86 (32 and 64 bits) and ARM only, as a
proof of concept and for developing and testing purposes. Making them
available on other architectures is straightforward.

Since no "user" for these new parameters is introduced in this patch,
the implementation of the new system calls is just identical to their
already existing counterpart. Future patches that implement scheduling
policies able to exploit the new data structure must also take care of
modifying the *2() calls accordingly with their own purposes.

Signed-off-by: Dario Faggioli <raistlin@linux.it>
Signed-off-by: Juri Lelli <juri.lelli@gmail.com>
---
 arch/arm/include/asm/unistd.h      |    2 +-
 arch/arm/include/uapi/asm/unistd.h |    3 +
 arch/arm/kernel/calls.S            |    3 +
 arch/x86/syscalls/syscall_32.tbl   |    3 +
 arch/x86/syscalls/syscall_64.tbl   |    3 +
 include/linux/sched.h              |   50 ++++++++++++++++
 include/linux/syscalls.h           |    7 +++
 kernel/sched/core.c                |  110 +++++++++++++++++++++++++++++++++++-
 8 files changed, 177 insertions(+), 4 deletions(-)

diff --git a/arch/arm/include/asm/unistd.h b/arch/arm/include/asm/unistd.h
index 141baa3..5f260fd 100644
--- a/arch/arm/include/asm/unistd.h
+++ b/arch/arm/include/asm/unistd.h
@@ -15,7 +15,7 @@
 
 #include <uapi/asm/unistd.h>
 
-#define __NR_syscalls  (380)
+#define __NR_syscalls  (383)
 #define __ARM_NR_cmpxchg		(__ARM_NR_BASE+0x00fff0)
 
 #define __ARCH_WANT_STAT64
diff --git a/arch/arm/include/uapi/asm/unistd.h b/arch/arm/include/uapi/asm/unistd.h
index af33b44..6a4985e 100644
--- a/arch/arm/include/uapi/asm/unistd.h
+++ b/arch/arm/include/uapi/asm/unistd.h
@@ -406,6 +406,9 @@
 #define __NR_process_vm_writev		(__NR_SYSCALL_BASE+377)
 #define __NR_kcmp			(__NR_SYSCALL_BASE+378)
 #define __NR_finit_module		(__NR_SYSCALL_BASE+379)
+#define __NR_sched_setscheduler2	(__NR_SYSCALL_BASE+380)
+#define __NR_sched_setparam2		(__NR_SYSCALL_BASE+381)
+#define __NR_sched_getparam2		(__NR_SYSCALL_BASE+382)
 
 /*
  * This may need to be greater than __NR_last_syscall+1 in order to
diff --git a/arch/arm/kernel/calls.S b/arch/arm/kernel/calls.S
index c6ca7e3..0fb1ef7 100644
--- a/arch/arm/kernel/calls.S
+++ b/arch/arm/kernel/calls.S
@@ -389,6 +389,9 @@
 		CALL(sys_process_vm_writev)
 		CALL(sys_kcmp)
 		CALL(sys_finit_module)
+/* 380 */	CALL(sys_sched_setscheduler2)
+		CALL(sys_sched_setparam2)
+		CALL(sys_sched_getparam2)
 #ifndef syscalls_counted
 .equ syscalls_padding, ((NR_syscalls + 3) & ~3) - NR_syscalls
 #define syscalls_counted
diff --git a/arch/x86/syscalls/syscall_32.tbl b/arch/x86/syscalls/syscall_32.tbl
index aabfb83..dfce815 100644
--- a/arch/x86/syscalls/syscall_32.tbl
+++ b/arch/x86/syscalls/syscall_32.tbl
@@ -357,3 +357,6 @@
 348	i386	process_vm_writev	sys_process_vm_writev		compat_sys_process_vm_writev
 349	i386	kcmp			sys_kcmp
 350	i386	finit_module		sys_finit_module
+351	i386	sched_setparam2		sys_sched_setparam2
+352	i386	sched_getparam2		sys_sched_getparam2
+353	i386	sched_setscheduler2	sys_sched_setscheduler2
diff --git a/arch/x86/syscalls/syscall_64.tbl b/arch/x86/syscalls/syscall_64.tbl
index 38ae65d..1849a70 100644
--- a/arch/x86/syscalls/syscall_64.tbl
+++ b/arch/x86/syscalls/syscall_64.tbl
@@ -320,6 +320,9 @@
 311	64	process_vm_writev	sys_process_vm_writev
 312	common	kcmp			sys_kcmp
 313	common	finit_module		sys_finit_module
+314	common	sched_setparam2		sys_sched_setparam2
+315	common	sched_getparam2		sys_sched_getparam2
+316	common	sched_setscheduler2	sys_sched_setscheduler2
 
 #
 # x32-specific system call numbers start at 512 to avoid cache impact
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 6682da3..6cc7193 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -55,6 +55,54 @@ struct sched_param {
 
 #include <asm/processor.h>
 
+/*
+ * Extended scheduling parameters data structure.
+ *
+ * This is needed because the original struct sched_param can not be
+ * altered without introducing ABI issues with legacy applications
+ * (e.g., in sched_getparam()).
+ *
+ * However, the possibility of specifying more than just a priority for
+ * the tasks may be useful for a wide variety of application fields, e.g.,
+ * multimedia, streaming, automation and control, and many others.
+ *
+ * This variant (sched_param2) is meant at describing a so-called
+ * sporadic time-constrained task. In such model a task is specified by:
+ *  - the activation period or minimum instance inter-arrival time;
+ *  - the maximum (or average, depending on the actual scheduling
+ *    discipline) computation time of all instances, a.k.a. runtime;
+ *  - the deadline (relative to the actual activation time) of each
+ *    instance.
+ * Very briefly, a periodic (sporadic) task asks for the execution of
+ * some specific computation --which is typically called an instance--
+ * (at most) every period. Moreover, each instance typically lasts no more
+ * than the runtime and must be completed by time instant t equal to
+ * the instance activation time + the deadline.
+ *
+ * This is reflected by the actual fields of the sched_param2 structure:
+ *
+ *  @sched_priority     task's priority (might still be useful)
+ *  @sched_deadline     representative of the task's deadline
+ *  @sched_runtime      representative of the task's runtime
+ *  @sched_period       representative of the task's period
+ *  @sched_flags        for customizing the scheduler behaviour
+ *
+ * Given this task model, there are a multiplicity of scheduling algorithms
+ * and policies, that can be used to ensure all the tasks will make their
+ * timing constraints.
+ *
+ * @__unused		padding to allow future expansion without ABI issues
+ */
+struct sched_param2 {
+	int sched_priority;
+	unsigned int sched_flags;
+	u64 sched_runtime;
+	u64 sched_deadline;
+	u64 sched_period;
+
+	u64 __unused[12];
+};
+
 struct exec_domain;
 struct futex_pi_state;
 struct robust_list_head;
@@ -1896,6 +1944,8 @@ extern int sched_setscheduler(struct task_struct *, int,
 			      const struct sched_param *);
 extern int sched_setscheduler_nocheck(struct task_struct *, int,
 				      const struct sched_param *);
+extern int sched_setscheduler2(struct task_struct *, int,
+				 const struct sched_param2 *);
 extern struct task_struct *idle_task(int cpu);
 /**
  * is_idle_task - is the specified task an idle task?
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 7fac04e..170ac59 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -38,6 +38,7 @@ struct rlimit;
 struct rlimit64;
 struct rusage;
 struct sched_param;
+struct sched_param2;
 struct sel_arg_struct;
 struct semaphore;
 struct sembuf;
@@ -277,11 +278,17 @@ asmlinkage long sys_clock_nanosleep(clockid_t which_clock, int flags,
 asmlinkage long sys_nice(int increment);
 asmlinkage long sys_sched_setscheduler(pid_t pid, int policy,
 					struct sched_param __user *param);
+asmlinkage long sys_sched_setscheduler2(pid_t pid, int policy,
+					struct sched_param2 __user *param);
 asmlinkage long sys_sched_setparam(pid_t pid,
 					struct sched_param __user *param);
+asmlinkage long sys_sched_setparam2(pid_t pid,
+					struct sched_param2 __user *param);
 asmlinkage long sys_sched_getscheduler(pid_t pid);
 asmlinkage long sys_sched_getparam(pid_t pid,
 					struct sched_param __user *param);
+asmlinkage long sys_sched_getparam2(pid_t pid,
+					struct sched_param2 __user *param);
 asmlinkage long sys_sched_setaffinity(pid_t pid, unsigned int len,
 					unsigned long __user *user_mask_ptr);
 asmlinkage long sys_sched_getaffinity(pid_t pid, unsigned int len,
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 850a02c..4fcbf13 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3285,7 +3285,8 @@ static bool check_same_owner(struct task_struct *p)
 }
 
 static int __sched_setscheduler(struct task_struct *p, int policy,
-				const struct sched_param *param, bool user)
+				const struct sched_param2 *param,
+				bool user)
 {
 	int retval, oldprio, oldpolicy = -1, on_rq, running;
 	unsigned long flags;
@@ -3450,10 +3451,20 @@ recheck:
 int sched_setscheduler(struct task_struct *p, int policy,
 		       const struct sched_param *param)
 {
-	return __sched_setscheduler(p, policy, param, true);
+	struct sched_param2 param2 = {
+		.sched_priority = param->sched_priority
+	};
+	return __sched_setscheduler(p, policy, &param2, true);
 }
 EXPORT_SYMBOL_GPL(sched_setscheduler);
 
+int sched_setscheduler2(struct task_struct *p, int policy,
+			  const struct sched_param2 *param2)
+{
+	return __sched_setscheduler(p, policy, param2, true);
+}
+EXPORT_SYMBOL_GPL(sched_setscheduler2);
+
 /**
  * sched_setscheduler_nocheck - change the scheduling policy and/or RT priority of a thread from kernelspace.
  * @p: the task in question.
@@ -3470,7 +3481,10 @@ EXPORT_SYMBOL_GPL(sched_setscheduler);
 int sched_setscheduler_nocheck(struct task_struct *p, int policy,
 			       const struct sched_param *param)
 {
-	return __sched_setscheduler(p, policy, param, false);
+	struct sched_param2 param2 = {
+		.sched_priority = param->sched_priority
+	};
+	return __sched_setscheduler(p, policy, &param2, false);
 }
 
 static int
@@ -3495,6 +3509,31 @@ do_sched_setscheduler(pid_t pid, int policy, struct sched_param __user *param)
 	return retval;
 }
 
+static int
+do_sched_setscheduler2(pid_t pid, int policy,
+			 struct sched_param2 __user *param2)
+{
+	struct sched_param2 lparam2;
+	struct task_struct *p;
+	int retval;
+
+	if (!param2 || pid < 0)
+		return -EINVAL;
+
+	memset(&lparam2, 0, sizeof(struct sched_param2));
+	if (copy_from_user(&lparam2, param2, sizeof(struct sched_param2)))
+		return -EFAULT;
+
+	rcu_read_lock();
+	retval = -ESRCH;
+	p = find_process_by_pid(pid);
+	if (p != NULL)
+		retval = sched_setscheduler2(p, policy, &lparam2);
+	rcu_read_unlock();
+
+	return retval;
+}
+
 /**
  * sys_sched_setscheduler - set/change the scheduler policy and RT priority
  * @pid: the pid in question.
@@ -3514,6 +3553,21 @@ SYSCALL_DEFINE3(sched_setscheduler, pid_t, pid, int, policy,
 }
 
 /**
+ * sys_sched_setscheduler2 - same as above, but with extended sched_param
+ * @pid: the pid in question.
+ * @policy: new policy (could use extended sched_param).
+ * @param: structure containg the extended parameters.
+ */
+SYSCALL_DEFINE3(sched_setscheduler2, pid_t, pid, int, policy,
+		struct sched_param2 __user *, param2)
+{
+	if (policy < 0)
+		return -EINVAL;
+
+	return do_sched_setscheduler2(pid, policy, param2);
+}
+
+/**
  * sys_sched_setparam - set/change the RT priority of a thread
  * @pid: the pid in question.
  * @param: structure containing the new RT priority.
@@ -3526,6 +3580,17 @@ SYSCALL_DEFINE2(sched_setparam, pid_t, pid, struct sched_param __user *, param)
 }
 
 /**
+ * sys_sched_setparam2 - same as above, but with extended sched_param
+ * @pid: the pid in question.
+ * @param2: structure containing the extended parameters.
+ */
+SYSCALL_DEFINE2(sched_setparam2, pid_t, pid,
+		struct sched_param2 __user *, param2)
+{
+	return do_sched_setscheduler2(pid, -1, param2);
+}
+
+/**
  * sys_sched_getscheduler - get the policy (scheduling class) of a thread
  * @pid: the pid in question.
  *
@@ -3595,6 +3660,45 @@ out_unlock:
 	return retval;
 }
 
+/**
+ * sys_sched_getparam2 - same as above, but with extended sched_param
+ * @pid: the pid in question.
+ * @param2: structure containing the extended parameters.
+ */
+SYSCALL_DEFINE2(sched_getparam2, pid_t, pid,
+		struct sched_param2 __user *, param2)
+{
+	struct sched_param2 lp;
+	struct task_struct *p;
+	int retval;
+
+	if (!param2 || pid < 0)
+		return -EINVAL;
+
+	rcu_read_lock();
+	p = find_process_by_pid(pid);
+	retval = -ESRCH;
+	if (!p)
+		goto out_unlock;
+
+	retval = security_task_getscheduler(p);
+	if (retval)
+		goto out_unlock;
+
+	lp.sched_priority = p->rt_priority;
+	rcu_read_unlock();
+
+	retval = copy_to_user(param2, &lp,
+			sizeof(struct sched_param2)) ? -EFAULT : 0;
+
+	return retval;
+
+out_unlock:
+	rcu_read_unlock();
+	return retval;
+
+}
+
 long sched_setaffinity(pid_t pid, const struct cpumask *in_mask)
 {
 	cpumask_var_t cpus_allowed, new_mask;
-- 
1.7.9.5

[PATCH 03/14] sched: SCHED_DEADLINE structures & implementation.

[Juri Lelli]

From: Dario Faggioli <raistlin@linux.it>

Introduces the data structures, constants and symbols needed for
SCHED_DEADLINE implementation.

Core data structure of SCHED_DEADLINE are defined, along with their
initializers. Hooks for checking if a task belong to the new policy
are also added where they are needed.

Adds a scheduling class, in sched/dl.c and a new policy called
SCHED_DEADLINE. It is an implementation of the Earliest Deadline
First (EDF) scheduling algorithm, augmented with a mechanism (called
Constant Bandwidth Server, CBS) that makes it possible to isolate
the behaviour of tasks between each other.

The typical -deadline task will be made up of a computation phase
(instance) which is activated on a periodic or sporadic fashion. The
expected (maximum) duration of such computation is called the task's
runtime; the time interval by which each instance need to be completed
is called the task's relative deadline. The task's absolute deadline
is dynamically calculated as the time instant a task (better, an
instance) activates plus the relative deadline.

The EDF algorithms selects the task with the smallest absolute
deadline as the one to be executed first, while the CBS ensures each
task to run for at most its runtime every (relative) deadline
length time interval, avoiding any interference between different
tasks (bandwidth isolation).
Thanks to this feature, also tasks that do not strictly comply with
the computational model sketched above can effectively use the new
policy.

To summarize, this patch:
 - introduces the data structures, constants and symbols needed;
 - implements the core logic of the scheduling algorithm in the new
   scheduling class file;
 - provides all the glue code between the new scheduling class and
   the core scheduler and refines the interactions between sched/dl
   and the other existing scheduling classes.

Signed-off-by: Dario Faggioli <raistlin@linux.it>
Signed-off-by: Michael Trimarchi <michael@amarulasolutions.com>
Signed-off-by: Fabio Checconi <fchecconi@gmail.com>
Signed-off-by: Juri Lelli <juri.lelli@gmail.com>
---
 arch/arm/include/asm/unistd.h  |    2 +-
 include/linux/sched.h          |   47 ++-
 include/linux/sched/deadline.h |   24 ++
 include/linux/sched/rt.h       |    2 +-
 include/uapi/linux/sched.h     |    1 +
 kernel/fork.c                  |    4 +-
 kernel/hrtimer.c               |    3 +-
 kernel/sched/Makefile          |    2 +-
 kernel/sched/core.c            |  111 ++++++-
 kernel/sched/deadline.c        |  692 ++++++++++++++++++++++++++++++++++++++++
 kernel/sched/sched.h           |   28 ++
 kernel/sched/stop_task.c       |    2 +-
 12 files changed, 895 insertions(+), 23 deletions(-)
 create mode 100644 include/linux/sched/deadline.h
 create mode 100644 kernel/sched/deadline.c

diff --git a/arch/arm/include/asm/unistd.h b/arch/arm/include/asm/unistd.h
index 5f260fd..acabef1 100644
--- a/arch/arm/include/asm/unistd.h
+++ b/arch/arm/include/asm/unistd.h
@@ -15,7 +15,7 @@
 
 #include <uapi/asm/unistd.h>
 
-#define __NR_syscalls  (383)
+#define __NR_syscalls  (384)
 #define __ARM_NR_cmpxchg		(__ARM_NR_BASE+0x00fff0)
 
 #define __ARCH_WANT_STAT64
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 6cc7193..7370f3e 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -92,6 +92,10 @@ struct sched_param {
  * timing constraints.
  *
  * @__unused		padding to allow future expansion without ABI issues
+ *
+ * As of now, the SCHED_DEADLINE policy (sched_dl scheduling class) is the
+ * only user of this new interface. More information about the algorithm
+ * available in the scheduling class file or in Documentation/.
  */
 struct sched_param2 {
 	int sched_priority;
@@ -1054,6 +1058,46 @@ struct sched_rt_entity {
 #endif
 };
 
+struct sched_dl_entity {
+	struct rb_node	rb_node;
+	int nr_cpus_allowed;
+
+	/*
+	 * Original scheduling parameters. Copied here from sched_param2
+	 * during sched_setscheduler2(), they will remain the same until
+	 * the next sched_setscheduler2().
+	 */
+	u64 dl_runtime;		/* maximum runtime for each instance	*/
+	u64 dl_deadline;	/* relative deadline of each instance	*/
+
+	/*
+	 * Actual scheduling parameters. Initialized with the values above,
+	 * they are continously updated during task execution. Note that
+	 * the remaining runtime could be < 0 in case we are in overrun.
+	 */
+	s64 runtime;		/* remaining runtime for this instance	*/
+	u64 deadline;		/* absolute deadline for this instance	*/
+	unsigned int flags;	/* specifying the scheduler behaviour	*/
+
+	/*
+	 * Some bool flags:
+	 *
+	 * @dl_throttled tells if we exhausted the runtime. If so, the
+	 * task has to wait for a replenishment to be performed at the
+	 * next firing of dl_timer.
+	 *
+	 * @dl_new tells if a new instance arrived. If so we must
+	 * start executing it with full runtime and reset its absolute
+	 * deadline;
+	 */
+	int dl_throttled, dl_new;
+
+	/*
+	 * Bandwidth enforcement timer. Each -deadline task has its
+	 * own bandwidth to be enforced, thus we need one timer per task.
+	 */
+	struct hrtimer dl_timer;
+};
 
 struct rcu_node;
 
@@ -1088,6 +1132,7 @@ struct task_struct {
 #ifdef CONFIG_CGROUP_SCHED
 	struct task_group *sched_task_group;
 #endif
+	struct sched_dl_entity dl;
 
 #ifdef CONFIG_PREEMPT_NOTIFIERS
 	/* list of struct preempt_notifier: */
@@ -2025,7 +2070,7 @@ extern void wake_up_new_task(struct task_struct *tsk);
 #else
  static inline void kick_process(struct task_struct *tsk) { }
 #endif
-extern void sched_fork(struct task_struct *p);
+extern int sched_fork(struct task_struct *p);
 extern void sched_dead(struct task_struct *p);
 
 extern void proc_caches_init(void);
diff --git a/include/linux/sched/deadline.h b/include/linux/sched/deadline.h
new file mode 100644
index 0000000..9d303b8
--- /dev/null
+++ b/include/linux/sched/deadline.h
@@ -0,0 +1,24 @@
+#ifndef _SCHED_DEADLINE_H
+#define _SCHED_DEADLINE_H
+
+/*
+ * SCHED_DEADLINE tasks has negative priorities, reflecting
+ * the fact that any of them has higher prio than RT and
+ * NORMAL/BATCH tasks.
+ */
+
+#define MAX_DL_PRIO		0
+
+static inline int dl_prio(int prio)
+{
+	if (unlikely(prio < MAX_DL_PRIO))
+		return 1;
+	return 0;
+}
+
+static inline int dl_task(struct task_struct *p)
+{
+	return dl_prio(p->prio);
+}
+
+#endif /* _SCHED_DEADLINE_H */
diff --git a/include/linux/sched/rt.h b/include/linux/sched/rt.h
index 440434d..a157797 100644
--- a/include/linux/sched/rt.h
+++ b/include/linux/sched/rt.h
@@ -22,7 +22,7 @@
 
 static inline int rt_prio(int prio)
 {
-	if (unlikely(prio < MAX_RT_PRIO))
+	if ((unsigned)prio < MAX_RT_PRIO)
 		return 1;
 	return 0;
 }
diff --git a/include/uapi/linux/sched.h b/include/uapi/linux/sched.h
index 5a0f945..2d5e49a 100644
--- a/include/uapi/linux/sched.h
+++ b/include/uapi/linux/sched.h
@@ -39,6 +39,7 @@
 #define SCHED_BATCH		3
 /* SCHED_ISO: reserved but not implemented yet */
 #define SCHED_IDLE		5
+#define SCHED_DEADLINE		6
 /* Can be ORed in to make sure the process is reverted back to SCHED_NORMAL on fork */
 #define SCHED_RESET_ON_FORK     0x40000000
 
diff --git a/kernel/fork.c b/kernel/fork.c
index 086fe73..55fc95f 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1313,7 +1313,9 @@ static struct task_struct *copy_process(unsigned long clone_flags,
 #endif
 
 	/* Perform scheduler related setup. Assign this task to a CPU. */
-	sched_fork(p);
+	retval = sched_fork(p);
+	if (retval)
+		goto bad_fork_cleanup_policy;
 
 	retval = perf_event_init_task(p);
 	if (retval)
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index 383319b..0909436 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -46,6 +46,7 @@
 #include <linux/sched.h>
 #include <linux/sched/sysctl.h>
 #include <linux/sched/rt.h>
+#include <linux/sched/deadline.h>
 #include <linux/timer.h>
 #include <linux/freezer.h>
 
@@ -1610,7 +1611,7 @@ long hrtimer_nanosleep(struct timespec *rqtp, struct timespec __user *rmtp,
 	unsigned long slack;
 
 	slack = current->timer_slack_ns;
-	if (rt_task(current))
+	if (dl_task(current) || rt_task(current))
 		slack = 0;
 
 	hrtimer_init_on_stack(&t.timer, clockid, mode);
diff --git a/kernel/sched/Makefile b/kernel/sched/Makefile
index 54adcf3..d77282f 100644
--- a/kernel/sched/Makefile
+++ b/kernel/sched/Makefile
@@ -11,7 +11,7 @@ ifneq ($(CONFIG_SCHED_OMIT_FRAME_POINTER),y)
 CFLAGS_core.o := $(PROFILING) -fno-omit-frame-pointer
 endif
 
-obj-y += core.o proc.o clock.o cputime.o idle_task.o fair.o rt.o stop_task.o
+obj-y += core.o proc.o clock.o cputime.o idle_task.o fair.o rt.o deadline.o stop_task.o
 obj-$(CONFIG_SMP) += cpupri.o
 obj-$(CONFIG_SCHED_AUTOGROUP) += auto_group.o
 obj-$(CONFIG_SCHEDSTATS) += stats.o
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 4fcbf13..cfe15bfc 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -903,7 +903,9 @@ static inline int normal_prio(struct task_struct *p)
 {
 	int prio;
 
-	if (task_has_rt_policy(p))
+	if (task_has_dl_policy(p))
+		prio = MAX_DL_PRIO-1;
+	else if (task_has_rt_policy(p))
 		prio = MAX_RT_PRIO-1 - p->rt_priority;
 	else
 		prio = __normal_prio(p);
@@ -1611,6 +1613,12 @@ static void __sched_fork(struct task_struct *p)
 	memset(&p->se.statistics, 0, sizeof(p->se.statistics));
 #endif
 
+	RB_CLEAR_NODE(&p->dl.rb_node);
+	hrtimer_init(&p->dl.dl_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+	p->dl.dl_runtime = p->dl.runtime = 0;
+	p->dl.dl_deadline = p->dl.deadline = 0;
+	p->dl.flags = 0;
+
 	INIT_LIST_HEAD(&p->rt.run_list);
 
 #ifdef CONFIG_PREEMPT_NOTIFIERS
@@ -1654,7 +1662,7 @@ void set_numabalancing_state(bool enabled)
 /*
  * fork()/clone()-time setup:
  */
-void sched_fork(struct task_struct *p)
+int sched_fork(struct task_struct *p)
 {
 	unsigned long flags;
 	int cpu = get_cpu();
@@ -1676,7 +1684,7 @@ void sched_fork(struct task_struct *p)
 	 * Revert to default priority/policy on fork if requested.
 	 */
 	if (unlikely(p->sched_reset_on_fork)) {
-		if (task_has_rt_policy(p)) {
+		if (task_has_dl_policy(p) || task_has_rt_policy(p)) {
 			p->policy = SCHED_NORMAL;
 			p->static_prio = NICE_TO_PRIO(0);
 			p->rt_priority = 0;
@@ -1693,8 +1701,14 @@ void sched_fork(struct task_struct *p)
 		p->sched_reset_on_fork = 0;
 	}
 
-	if (!rt_prio(p->prio))
+	if (dl_prio(p->prio)) {
+		put_cpu();
+		return -EAGAIN;
+	} else if (rt_prio(p->prio)) {
+		p->sched_class = &rt_sched_class;
+	} else {
 		p->sched_class = &fair_sched_class;
+	}
 
 	if (p->sched_class->task_fork)
 		p->sched_class->task_fork(p);
@@ -1726,6 +1740,7 @@ void sched_fork(struct task_struct *p)
 #endif
 
 	put_cpu();
+	return 0;
 }
 
 /*
@@ -3029,7 +3044,7 @@ void rt_mutex_setprio(struct task_struct *p, int prio)
 	struct rq *rq;
 	const struct sched_class *prev_class;
 
-	BUG_ON(prio < 0 || prio > MAX_PRIO);
+	BUG_ON(prio > MAX_PRIO);
 
 	rq = __task_rq_lock(p);
 
@@ -3061,7 +3076,9 @@ void rt_mutex_setprio(struct task_struct *p, int prio)
 	if (running)
 		p->sched_class->put_prev_task(rq, p);
 
-	if (rt_prio(prio))
+	if (dl_prio(prio))
+		p->sched_class = &dl_sched_class;
+	else if (rt_prio(prio))
 		p->sched_class = &rt_sched_class;
 	else
 		p->sched_class = &fair_sched_class;
@@ -3095,9 +3112,9 @@ void set_user_nice(struct task_struct *p, long nice)
 	 * The RT priorities are set via sched_setscheduler(), but we still
 	 * allow the 'normal' nice value to be set - but as expected
 	 * it wont have any effect on scheduling until the task is
-	 * SCHED_FIFO/SCHED_RR:
+	 * SCHED_DEADLINE, SCHED_FIFO or SCHED_RR:
 	 */
-	if (task_has_rt_policy(p)) {
+	if (task_has_dl_policy(p) || task_has_rt_policy(p)) {
 		p->static_prio = NICE_TO_PRIO(nice);
 		goto out_unlock;
 	}
@@ -3261,7 +3278,9 @@ __setscheduler(struct rq *rq, struct task_struct *p, int policy, int prio)
 	p->normal_prio = normal_prio(p);
 	/* we are holding p->pi_lock already */
 	p->prio = rt_mutex_getprio(p);
-	if (rt_prio(p->prio))
+	if (dl_prio(p->prio))
+		p->sched_class = &dl_sched_class;
+	else if (rt_prio(p->prio))
 		p->sched_class = &rt_sched_class;
 	else
 		p->sched_class = &fair_sched_class;
@@ -3269,6 +3288,50 @@ __setscheduler(struct rq *rq, struct task_struct *p, int policy, int prio)
 }
 
 /*
+ * This function initializes the sched_dl_entity of a newly becoming
+ * SCHED_DEADLINE task.
+ *
+ * Only the static values are considered here, the actual runtime and the
+ * absolute deadline will be properly calculated when the task is enqueued
+ * for the first time with its new policy.
+ */
+static void
+__setparam_dl(struct task_struct *p, const struct sched_param2 *param2)
+{
+	struct sched_dl_entity *dl_se = &p->dl;
+
+	init_dl_task_timer(dl_se);
+	dl_se->dl_runtime = param2->sched_runtime;
+	dl_se->dl_deadline = param2->sched_deadline;
+	dl_se->flags = param2->sched_flags;
+	dl_se->dl_throttled = 0;
+	dl_se->dl_new = 1;
+}
+
+static void
+__getparam_dl(struct task_struct *p, struct sched_param2 *param2)
+{
+	struct sched_dl_entity *dl_se = &p->dl;
+
+	param2->sched_priority = p->rt_priority;
+	param2->sched_runtime = dl_se->dl_runtime;
+	param2->sched_deadline = dl_se->dl_deadline;
+	param2->sched_flags = dl_se->flags;
+}
+
+/*
+ * This function validates the new parameters of a -deadline task.
+ * We ask for the deadline not being zero, and greater or equal
+ * than the runtime.
+ */
+static bool
+__checkparam_dl(const struct sched_param2 *prm)
+{
+	return prm && (&prm->sched_deadline) != 0 &&
+	       (s64)(&prm->sched_deadline - &prm->sched_runtime) >= 0;
+}
+
+/*
  * check the target process has a UID that matches the current process's
  */
 static bool check_same_owner(struct task_struct *p)
@@ -3305,7 +3368,8 @@ recheck:
 		reset_on_fork = !!(policy & SCHED_RESET_ON_FORK);
 		policy &= ~SCHED_RESET_ON_FORK;
 
-		if (policy != SCHED_FIFO && policy != SCHED_RR &&
+		if (policy != SCHED_DEADLINE &&
+				policy != SCHED_FIFO && policy != SCHED_RR &&
 				policy != SCHED_NORMAL && policy != SCHED_BATCH &&
 				policy != SCHED_IDLE)
 			return -EINVAL;
@@ -3320,7 +3384,8 @@ recheck:
 	    (p->mm && param->sched_priority > MAX_USER_RT_PRIO-1) ||
 	    (!p->mm && param->sched_priority > MAX_RT_PRIO-1))
 		return -EINVAL;
-	if (rt_policy(policy) != (param->sched_priority != 0))
+	if ((dl_policy(policy) && !__checkparam_dl(param)) ||
+	    (rt_policy(policy) != (param->sched_priority != 0)))
 		return -EINVAL;
 
 	/*
@@ -3386,7 +3451,8 @@ recheck:
 	 * If not changing anything there's no need to proceed further:
 	 */
 	if (unlikely(policy == p->policy && (!rt_policy(policy) ||
-			param->sched_priority == p->rt_priority))) {
+			param->sched_priority == p->rt_priority) &&
+			!dl_policy(policy))) {
 		task_rq_unlock(rq, p, &flags);
 		return 0;
 	}
@@ -3423,7 +3489,11 @@ recheck:
 
 	oldprio = p->prio;
 	prev_class = p->sched_class;
-	__setscheduler(rq, p, policy, param->sched_priority);
+	if (dl_policy(policy)) {
+		__setparam_dl(p, param);
+		__setscheduler(rq, p, policy, param->sched_priority);
+	} else
+		__setscheduler(rq, p, policy, param->sched_priority);
 
 	if (running)
 		p->sched_class->set_curr_task(rq);
@@ -3527,8 +3597,11 @@ do_sched_setscheduler2(pid_t pid, int policy,
 	rcu_read_lock();
 	retval = -ESRCH;
 	p = find_process_by_pid(pid);
-	if (p != NULL)
+	if (p != NULL) {
+		if (dl_policy(policy))
+			lparam2.sched_priority = 0;
 		retval = sched_setscheduler2(p, policy, &lparam2);
+	}
 	rcu_read_unlock();
 
 	return retval;
@@ -3685,7 +3758,10 @@ SYSCALL_DEFINE2(sched_getparam2, pid_t, pid,
 	if (retval)
 		goto out_unlock;
 
-	lp.sched_priority = p->rt_priority;
+	if (task_has_dl_policy(p))
+		__getparam_dl(p, &lp);
+	else
+		lp.sched_priority = p->rt_priority;
 	rcu_read_unlock();
 
 	retval = copy_to_user(param2, &lp,
@@ -4120,6 +4196,7 @@ SYSCALL_DEFINE1(sched_get_priority_max, int, policy)
 	case SCHED_RR:
 		ret = MAX_USER_RT_PRIO-1;
 		break;
+	case SCHED_DEADLINE:
 	case SCHED_NORMAL:
 	case SCHED_BATCH:
 	case SCHED_IDLE:
@@ -4146,6 +4223,7 @@ SYSCALL_DEFINE1(sched_get_priority_min, int, policy)
 	case SCHED_RR:
 		ret = 1;
 		break;
+	case SCHED_DEADLINE:
 	case SCHED_NORMAL:
 	case SCHED_BATCH:
 	case SCHED_IDLE:
@@ -6563,6 +6641,7 @@ void __init sched_init(void)
 		rq->calc_load_update = jiffies + LOAD_FREQ;
 		init_cfs_rq(&rq->cfs);
 		init_rt_rq(&rq->rt, rq);
+		init_dl_rq(&rq->dl, rq);
 #ifdef CONFIG_FAIR_GROUP_SCHED
 		root_task_group.shares = ROOT_TASK_GROUP_LOAD;
 		INIT_LIST_HEAD(&rq->leaf_cfs_rq_list);
@@ -6746,7 +6825,7 @@ void normalize_rt_tasks(void)
 		p->se.statistics.block_start	= 0;
 #endif
 
-		if (!rt_task(p)) {
+		if (!dl_task(p) && !rt_task(p)) {
 			/*
 			 * Renice negative nice level userspace
 			 * tasks back to 0:
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
new file mode 100644
index 0000000..b1982a7
--- /dev/null
+++ b/kernel/sched/deadline.c
@@ -0,0 +1,692 @@
+/*
+ * Deadline Scheduling Class (SCHED_DEADLINE)
+ *
+ * Earliest Deadline First (EDF) + Constant Bandwidth Server (CBS).
+ *
+ * Tasks that periodically executes their instances for less than their
+ * runtime won't miss any of their deadlines.
+ * Tasks that are not periodic or sporadic or that tries to execute more
+ * than their reserved bandwidth will be slowed down (and may potentially
+ * miss some of their deadlines), and won't affect any other task.
+ *
+ * Copyright (C) 2012 Dario Faggioli <raistlin@linux.it>,
+ *                    Michael Trimarchi <michael@amarulasolutions.com>,
+ *                    Fabio Checconi <fchecconi@gmail.com>
+ */
+#include "sched.h"
+
+static inline int dl_time_before(u64 a, u64 b)
+{
+	return (s64)(a - b) < 0;
+}
+
+static inline struct task_struct *dl_task_of(struct sched_dl_entity *dl_se)
+{
+	return container_of(dl_se, struct task_struct, dl);
+}
+
+static inline struct rq *rq_of_dl_rq(struct dl_rq *dl_rq)
+{
+	return container_of(dl_rq, struct rq, dl);
+}
+
+static inline struct dl_rq *dl_rq_of_se(struct sched_dl_entity *dl_se)
+{
+	struct task_struct *p = dl_task_of(dl_se);
+	struct rq *rq = task_rq(p);
+
+	return &rq->dl;
+}
+
+static inline int on_dl_rq(struct sched_dl_entity *dl_se)
+{
+	return !RB_EMPTY_NODE(&dl_se->rb_node);
+}
+
+static inline int is_leftmost(struct task_struct *p, struct dl_rq *dl_rq)
+{
+	struct sched_dl_entity *dl_se = &p->dl;
+
+	return dl_rq->rb_leftmost == &dl_se->rb_node;
+}
+
+void init_dl_rq(struct dl_rq *dl_rq, struct rq *rq)
+{
+	dl_rq->rb_root = RB_ROOT;
+}
+
+static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags);
+static void __dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags);
+static void check_preempt_curr_dl(struct rq *rq, struct task_struct *p,
+				  int flags);
+
+/*
+ * We are being explicitly informed that a new instance is starting,
+ * and this means that:
+ *  - the absolute deadline of the entity has to be placed at
+ *    current time + relative deadline;
+ *  - the runtime of the entity has to be set to the maximum value.
+ *
+ * The capability of specifying such event is useful whenever a -deadline
+ * entity wants to (try to!) synchronize its behaviour with the scheduler's
+ * one, and to (try to!) reconcile itself with its own scheduling
+ * parameters.
+ */
+static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se)
+{
+	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
+	struct rq *rq = rq_of_dl_rq(dl_rq);
+
+	WARN_ON(!dl_se->dl_new || dl_se->dl_throttled);
+
+	/*
+	 * We use the regular wall clock time to set deadlines in the
+	 * future; in fact, we must consider execution overheads (time
+	 * spent on hardirq context, etc.).
+	 */
+	dl_se->deadline = rq->clock + dl_se->dl_deadline;
+	dl_se->runtime = dl_se->dl_runtime;
+	dl_se->dl_new = 0;
+}
+
+/*
+ * Pure Earliest Deadline First (EDF) scheduling does not deal with the
+ * possibility of a entity lasting more than what it declared, and thus
+ * exhausting its runtime.
+ *
+ * Here we are interested in making runtime overrun possible, but we do
+ * not want a entity which is misbehaving to affect the scheduling of all
+ * other entities.
+ * Therefore, a budgeting strategy called Constant Bandwidth Server (CBS)
+ * is used, in order to confine each entity within its own bandwidth.
+ *
+ * This function deals exactly with that, and ensures that when the runtime
+ * of a entity is replenished, its deadline is also postponed. That ensures
+ * the overrunning entity can't interfere with other entity in the system and
+ * can't make them miss their deadlines. Reasons why this kind of overruns
+ * could happen are, typically, a entity voluntarily trying to overcome its
+ * runtime, or it just underestimated it during sched_setscheduler_ex().
+ */
+static void replenish_dl_entity(struct sched_dl_entity *dl_se)
+{
+	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
+	struct rq *rq = rq_of_dl_rq(dl_rq);
+
+	/*
+	 * We keep moving the deadline away until we get some
+	 * available runtime for the entity. This ensures correct
+	 * handling of situations where the runtime overrun is
+	 * arbitrary large.
+	 */
+	while (dl_se->runtime <= 0) {
+		dl_se->deadline += dl_se->dl_deadline;
+		dl_se->runtime += dl_se->dl_runtime;
+	}
+
+	/*
+	 * At this point, the deadline really should be "in
+	 * the future" with respect to rq->clock. If it's
+	 * not, we are, for some reason, lagging too much!
+	 * Anyway, after having warn userspace abut that,
+	 * we still try to keep the things running by
+	 * resetting the deadline and the budget of the
+	 * entity.
+	 */
+	if (dl_time_before(dl_se->deadline, rq->clock)) {
+		static bool lag_once = false;
+
+		if (!lag_once) {
+			lag_once = true;
+			printk_sched("sched: DL replenish lagged to much\n");
+		}
+		dl_se->deadline = rq->clock + dl_se->dl_deadline;
+		dl_se->runtime = dl_se->dl_runtime;
+	}
+}
+
+/*
+ * Here we check if --at time t-- an entity (which is probably being
+ * [re]activated or, in general, enqueued) can use its remaining runtime
+ * and its current deadline _without_ exceeding the bandwidth it is
+ * assigned (function returns true if it can't). We are in fact applying
+ * one of the CBS rules: when a task wakes up, if the residual runtime
+ * over residual deadline fits within the allocated bandwidth, then we
+ * can keep the current (absolute) deadline and residual budget without
+ * disrupting the schedulability of the system. Otherwise, we should
+ * refill the runtime and set the deadline a period in the future,
+ * because keeping the current (absolute) deadline of the task would
+ * result in breaking guarantees promised to other tasks.
+ *
+ * This function returns true if:
+ *
+ *   runtime / (deadline - t) > dl_runtime / dl_deadline ,
+ *
+ * IOW we can't recycle current parameters.
+ */
+static bool dl_entity_overflow(struct sched_dl_entity *dl_se, u64 t)
+{
+	u64 left, right;
+
+	/*
+	 * left and right are the two sides of the equation above,
+	 * after a bit of shuffling to use multiplications instead
+	 * of divisions.
+	 *
+	 * Note that none of the time values involved in the two
+	 * multiplications are absolute: dl_deadline and dl_runtime
+	 * are the relative deadline and the maximum runtime of each
+	 * instance, runtime is the runtime left for the last instance
+	 * and (deadline - t), since t is rq->clock, is the time left
+	 * to the (absolute) deadline. Even if overflowing the u64 type
+	 * is very unlikely to occur in both cases, here we scale down
+	 * as we want to avoid that risk at all. Scaling down by 10
+	 * means that we reduce granularity to 1us. We are fine with it,
+	 * since this is only a true/false check and, anyway, thinking
+	 * of anything below microseconds resolution is actually fiction
+	 * (but still we want to give the user that illusion >;).
+	 */
+	left = (dl_se->dl_deadline >> 10) * (dl_se->runtime >> 10);
+	right = ((dl_se->deadline - t) >> 10) * (dl_se->dl_runtime >> 10);
+
+	return dl_time_before(right, left);
+}
+
+/*
+ * When a -deadline entity is queued back on the runqueue, its runtime and
+ * deadline might need updating.
+ *
+ * The policy here is that we update the deadline of the entity only if:
+ *  - the current deadline is in the past,
+ *  - using the remaining runtime with the current deadline would make
+ *    the entity exceed its bandwidth.
+ */
+static void update_dl_entity(struct sched_dl_entity *dl_se)
+{
+	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
+	struct rq *rq = rq_of_dl_rq(dl_rq);
+
+	/*
+	 * The arrival of a new instance needs special treatment, i.e.,
+	 * the actual scheduling parameters have to be "renewed".
+	 */
+	if (dl_se->dl_new) {
+		setup_new_dl_entity(dl_se);
+		return;
+	}
+
+	if (dl_time_before(dl_se->deadline, rq->clock) ||
+	    dl_entity_overflow(dl_se, rq->clock)) {
+		dl_se->deadline = rq->clock + dl_se->dl_deadline;
+		dl_se->runtime = dl_se->dl_runtime;
+	}
+}
+
+/*
+ * If the entity depleted all its runtime, and if we want it to sleep
+ * while waiting for some new execution time to become available, we
+ * set the bandwidth enforcement timer to the replenishment instant
+ * and try to activate it.
+ *
+ * Notice that it is important for the caller to know if the timer
+ * actually started or not (i.e., the replenishment instant is in
+ * the future or in the past).
+ */
+static int start_dl_timer(struct sched_dl_entity *dl_se)
+{
+	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
+	struct rq *rq = rq_of_dl_rq(dl_rq);
+	ktime_t now, act;
+	ktime_t soft, hard;
+	unsigned long range;
+	s64 delta;
+
+	/*
+	 * We want the timer to fire at the deadline, but considering
+	 * that it is actually coming from rq->clock and not from
+	 * hrtimer's time base reading.
+	 */
+	act = ns_to_ktime(dl_se->deadline);
+	now = hrtimer_cb_get_time(&dl_se->dl_timer);
+	delta = ktime_to_ns(now) - rq->clock;
+	act = ktime_add_ns(act, delta);
+
+	/*
+	 * If the expiry time already passed, e.g., because the value
+	 * chosen as the deadline is too small, don't even try to
+	 * start the timer in the past!
+	 */
+	if (ktime_us_delta(act, now) < 0)
+		return 0;
+
+	hrtimer_set_expires(&dl_se->dl_timer, act);
+
+	soft = hrtimer_get_softexpires(&dl_se->dl_timer);
+	hard = hrtimer_get_expires(&dl_se->dl_timer);
+	range = ktime_to_ns(ktime_sub(hard, soft));
+	__hrtimer_start_range_ns(&dl_se->dl_timer, soft,
+				 range, HRTIMER_MODE_ABS, 0);
+
+	return hrtimer_active(&dl_se->dl_timer);
+}
+
+/*
+ * This is the bandwidth enforcement timer callback. If here, we know
+ * a task is not on its dl_rq, since the fact that the timer was running
+ * means the task is throttled and needs a runtime replenishment.
+ *
+ * However, what we actually do depends on the fact the task is active,
+ * (it is on its rq) or has been removed from there by a call to
+ * dequeue_task_dl(). In the former case we must issue the runtime
+ * replenishment and add the task back to the dl_rq; in the latter, we just
+ * do nothing but clearing dl_throttled, so that runtime and deadline
+ * updating (and the queueing back to dl_rq) will be done by the
+ * next call to enqueue_task_dl().
+ */
+static enum hrtimer_restart dl_task_timer(struct hrtimer *timer)
+{
+	struct sched_dl_entity *dl_se = container_of(timer,
+						     struct sched_dl_entity,
+						     dl_timer);
+	struct task_struct *p = dl_task_of(dl_se);
+	struct rq *rq = task_rq(p);
+	raw_spin_lock(&rq->lock);
+
+	/*
+	 * We need to take care of a possible races here. In fact, the
+	 * task might have changed its scheduling policy to something
+	 * different from SCHED_DEADLINE or changed its reservation
+	 * parameters (through sched_setscheduler()).
+	 */
+	if (!dl_task(p) || dl_se->dl_new)
+		goto unlock;
+
+	dl_se->dl_throttled = 0;
+	if (p->on_rq) {
+		enqueue_task_dl(rq, p, ENQUEUE_REPLENISH);
+		if (task_has_dl_policy(rq->curr))
+			check_preempt_curr_dl(rq, p, 0);
+		else
+			resched_task(rq->curr);
+	}
+unlock:
+	raw_spin_unlock(&rq->lock);
+
+	return HRTIMER_NORESTART;
+}
+
+void init_dl_task_timer(struct sched_dl_entity *dl_se)
+{
+	struct hrtimer *timer = &dl_se->dl_timer;
+
+	if (hrtimer_active(timer)) {
+		hrtimer_try_to_cancel(timer);
+		return;
+	}
+
+	hrtimer_init(timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+	timer->function = dl_task_timer;
+}
+
+static
+int dl_runtime_exceeded(struct rq *rq, struct sched_dl_entity *dl_se)
+{
+	int dmiss = dl_time_before(dl_se->deadline, rq->clock);
+	int rorun = dl_se->runtime <= 0;
+
+	if (!rorun && !dmiss)
+		return 0;
+
+	/*
+	 * If we are beyond our current deadline and we are still
+	 * executing, then we have already used some of the runtime of
+	 * the next instance. Thus, if we do not account that, we are
+	 * stealing bandwidth from the system at each deadline miss!
+	 */
+	if (dmiss) {
+		dl_se->runtime = rorun ? dl_se->runtime : 0;
+		dl_se->runtime -= rq->clock - dl_se->deadline;
+	}
+
+	return 1;
+}
+
+/*
+ * Update the current task's runtime statistics (provided it is still
+ * a -deadline task and has not been removed from the dl_rq).
+ */
+static void update_curr_dl(struct rq *rq)
+{
+	struct task_struct *curr = rq->curr;
+	struct sched_dl_entity *dl_se = &curr->dl;
+	u64 delta_exec;
+
+	if (!dl_task(curr) || !on_dl_rq(dl_se))
+		return;
+
+	/*
+	 * Consumed budget is computed considering the time as
+	 * observed by schedulable tasks (excluding time spent
+	 * in hardirq context, etc.)
+	 */
+	delta_exec = rq->clock_task - curr->se.exec_start;
+	if (unlikely((s64)delta_exec < 0))
+		delta_exec = 0;
+
+	schedstat_set(curr->se.statistics.exec_max,
+		      max(curr->se.statistics.exec_max, delta_exec));
+
+	curr->se.sum_exec_runtime += delta_exec;
+	account_group_exec_runtime(curr, delta_exec);
+
+	curr->se.exec_start = rq->clock_task;
+	cpuacct_charge(curr, delta_exec);
+
+	dl_se->runtime -= delta_exec;
+	if (dl_runtime_exceeded(rq, dl_se)) {
+		__dequeue_task_dl(rq, curr, 0);
+		if (likely(start_dl_timer(dl_se)))
+			dl_se->dl_throttled = 1;
+		else
+			enqueue_task_dl(rq, curr, ENQUEUE_REPLENISH);
+
+		if (!is_leftmost(curr, &rq->dl))
+			resched_task(curr);
+	}
+}
+
+static void __enqueue_dl_entity(struct sched_dl_entity *dl_se)
+{
+	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
+	struct rb_node **link = &dl_rq->rb_root.rb_node;
+	struct rb_node *parent = NULL;
+	struct sched_dl_entity *entry;
+	int leftmost = 1;
+
+	BUG_ON(!RB_EMPTY_NODE(&dl_se->rb_node));
+
+	while (*link) {
+		parent = *link;
+		entry = rb_entry(parent, struct sched_dl_entity, rb_node);
+		if (dl_time_before(dl_se->deadline, entry->deadline))
+			link = &parent->rb_left;
+		else {
+			link = &parent->rb_right;
+			leftmost = 0;
+		}
+	}
+
+	if (leftmost)
+		dl_rq->rb_leftmost = &dl_se->rb_node;
+
+	rb_link_node(&dl_se->rb_node, parent, link);
+	rb_insert_color(&dl_se->rb_node, &dl_rq->rb_root);
+
+	dl_rq->dl_nr_running++;
+}
+
+static void __dequeue_dl_entity(struct sched_dl_entity *dl_se)
+{
+	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
+
+	if (RB_EMPTY_NODE(&dl_se->rb_node))
+		return;
+
+	if (dl_rq->rb_leftmost == &dl_se->rb_node) {
+		struct rb_node *next_node;
+
+		next_node = rb_next(&dl_se->rb_node);
+		dl_rq->rb_leftmost = next_node;
+	}
+
+	rb_erase(&dl_se->rb_node, &dl_rq->rb_root);
+	RB_CLEAR_NODE(&dl_se->rb_node);
+
+	dl_rq->dl_nr_running--;
+}
+
+static void
+enqueue_dl_entity(struct sched_dl_entity *dl_se, int flags)
+{
+	BUG_ON(on_dl_rq(dl_se));
+
+	/*
+	 * If this is a wakeup or a new instance, the scheduling
+	 * parameters of the task might need updating. Otherwise,
+	 * we want a replenishment of its runtime.
+	 */
+	if (!dl_se->dl_new && flags & ENQUEUE_REPLENISH)
+		replenish_dl_entity(dl_se);
+	else
+		update_dl_entity(dl_se);
+
+	__enqueue_dl_entity(dl_se);
+}
+
+static void dequeue_dl_entity(struct sched_dl_entity *dl_se)
+{
+	__dequeue_dl_entity(dl_se);
+}
+
+static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags)
+{
+	/*
+	 * If p is throttled, we do nothing. In fact, if it exhausted
+	 * its budget it needs a replenishment and, since it now is on
+	 * its rq, the bandwidth timer callback (which clearly has not
+	 * run yet) will take care of this.
+	 */
+	if (p->dl.dl_throttled)
+		return;
+
+	enqueue_dl_entity(&p->dl, flags);
+	inc_nr_running(rq);
+}
+
+static void __dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags)
+{
+	dequeue_dl_entity(&p->dl);
+}
+
+static void dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags)
+{
+	update_curr_dl(rq);
+	__dequeue_task_dl(rq, p, flags);
+
+	dec_nr_running(rq);
+}
+
+/*
+ * Yield task semantic for -deadline tasks is:
+ *
+ *   get off from the CPU until our next instance, with
+ *   a new runtime.
+ */
+static void yield_task_dl(struct rq *rq)
+{
+	struct task_struct *p = rq->curr;
+
+	/*
+	 * We make the task go to sleep until its current deadline by
+	 * forcing its runtime to zero. This way, update_curr_dl() stops
+	 * it and the bandwidth timer will wake it up and will give it
+	 * new scheduling parameters (thanks to dl_new=1).
+	 */
+	if (p->dl.runtime > 0) {
+		rq->curr->dl.dl_new = 1;
+		p->dl.runtime = 0;
+	}
+	update_curr_dl(rq);
+}
+
+/*
+ * Only called when both the current and waking task are -deadline
+ * tasks.
+ */
+static void check_preempt_curr_dl(struct rq *rq, struct task_struct *p,
+				  int flags)
+{
+	if (dl_time_before(p->dl.deadline, rq->curr->dl.deadline))
+		resched_task(rq->curr);
+}
+
+#ifdef CONFIG_SCHED_HRTICK
+static void start_hrtick_dl(struct rq *rq, struct task_struct *p)
+{
+	s64 delta = p->dl.dl_runtime - p->dl.runtime;
+
+	if (delta > 10000)
+		hrtick_start(rq, p->dl.runtime);
+}
+#else
+static void start_hrtick_dl(struct rq *rq, struct task_struct *p)
+{
+}
+#endif
+
+static struct sched_dl_entity *pick_next_dl_entity(struct rq *rq,
+						   struct dl_rq *dl_rq)
+{
+	struct rb_node *left = dl_rq->rb_leftmost;
+
+	if (!left)
+		return NULL;
+
+	return rb_entry(left, struct sched_dl_entity, rb_node);
+}
+
+struct task_struct *pick_next_task_dl(struct rq *rq)
+{
+	struct sched_dl_entity *dl_se;
+	struct task_struct *p;
+	struct dl_rq *dl_rq;
+
+	dl_rq = &rq->dl;
+
+	if (unlikely(!dl_rq->dl_nr_running))
+		return NULL;
+
+	dl_se = pick_next_dl_entity(rq, dl_rq);
+	BUG_ON(!dl_se);
+
+	p = dl_task_of(dl_se);
+	p->se.exec_start = rq->clock;
+#ifdef CONFIG_SCHED_HRTICK
+	if (hrtick_enabled(rq))
+		start_hrtick_dl(rq, p);
+#endif
+	return p;
+}
+
+static void put_prev_task_dl(struct rq *rq, struct task_struct *p)
+{
+	update_curr_dl(rq);
+}
+
+static void task_tick_dl(struct rq *rq, struct task_struct *p, int queued)
+{
+	update_curr_dl(rq);
+
+#ifdef CONFIG_SCHED_HRTICK
+	if (hrtick_enabled(rq) && queued && p->dl.runtime > 0)
+		start_hrtick_dl(rq, p);
+#endif
+}
+
+static void task_fork_dl(struct task_struct *p)
+{
+	/*
+	 * SCHED_DEADLINE tasks cannot fork and this is achieved through
+	 * sched_fork()
+	 */
+}
+
+static void task_dead_dl(struct task_struct *p)
+{
+	struct hrtimer *timer = &p->dl.dl_timer;
+
+	if (hrtimer_active(timer))
+		hrtimer_try_to_cancel(timer);
+}
+
+static void set_curr_task_dl(struct rq *rq)
+{
+	struct task_struct *p = rq->curr;
+
+	p->se.exec_start = rq->clock;
+}
+
+static void switched_from_dl(struct rq *rq, struct task_struct *p)
+{
+	if (hrtimer_active(&p->dl.dl_timer))
+		hrtimer_try_to_cancel(&p->dl.dl_timer);
+}
+
+static void switched_to_dl(struct rq *rq, struct task_struct *p)
+{
+	/*
+	 * If p is throttled, don't consider the possibility
+	 * of preempting rq->curr, the check will be done right
+	 * after its runtime will get replenished.
+	 */
+	if (unlikely(p->dl.dl_throttled))
+		return;
+
+	if (!p->on_rq || rq->curr != p) {
+		if (task_has_dl_policy(rq->curr))
+			check_preempt_curr_dl(rq, p, 0);
+		else
+			resched_task(rq->curr);
+	}
+}
+
+static void prio_changed_dl(struct rq *rq, struct task_struct *p,
+			    int oldprio)
+{
+	switched_to_dl(rq, p);
+}
+
+#ifdef CONFIG_SMP
+static int
+select_task_rq_dl(struct task_struct *p, int sd_flag, int flags)
+{
+	return task_cpu(p);
+}
+
+static void set_cpus_allowed_dl(struct task_struct *p,
+				const struct cpumask *new_mask)
+{
+	int weight = cpumask_weight(new_mask);
+
+	BUG_ON(!dl_task(p));
+
+	cpumask_copy(&p->cpus_allowed, new_mask);
+	p->dl.nr_cpus_allowed = weight;
+}
+#endif
+
+const struct sched_class dl_sched_class = {
+	.next			= &rt_sched_class,
+	.enqueue_task		= enqueue_task_dl,
+	.dequeue_task		= dequeue_task_dl,
+	.yield_task		= yield_task_dl,
+
+	.check_preempt_curr	= check_preempt_curr_dl,
+
+	.pick_next_task		= pick_next_task_dl,
+	.put_prev_task		= put_prev_task_dl,
+
+#ifdef CONFIG_SMP
+	.select_task_rq		= select_task_rq_dl,
+
+	.set_cpus_allowed       = set_cpus_allowed_dl,
+#endif
+
+	.set_curr_task		= set_curr_task_dl,
+	.task_tick		= task_tick_dl,
+	.task_fork              = task_fork_dl,
+	.task_dead		= task_dead_dl,
+
+	.prio_changed           = prio_changed_dl,
+	.switched_from		= switched_from_dl,
+	.switched_to		= switched_to_dl,
+};
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 64eda5c..ba97476 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -2,6 +2,7 @@
 #include <linux/sched.h>
 #include <linux/sched/sysctl.h>
 #include <linux/sched/rt.h>
+#include <linux/sched/deadline.h>
 #include <linux/mutex.h>
 #include <linux/spinlock.h>
 #include <linux/stop_machine.h>
@@ -87,11 +88,23 @@ static inline int rt_policy(int policy)
 	return 0;
 }
 
+static inline int dl_policy(int policy)
+{
+	if (unlikely(policy == SCHED_DEADLINE))
+		return 1;
+	return 0;
+}
+
 static inline int task_has_rt_policy(struct task_struct *p)
 {
 	return rt_policy(p->policy);
 }
 
+static inline int task_has_dl_policy(struct task_struct *p)
+{
+	return dl_policy(p->policy);
+}
+
 /*
  * This is the priority-queue data structure of the RT scheduling class:
  */
@@ -363,6 +376,15 @@ struct rt_rq {
 #endif
 };
 
+/* Deadline class' related fields in a runqueue */
+struct dl_rq {
+	/* runqueue is an rbtree, ordered by deadline */
+	struct rb_root rb_root;
+	struct rb_node *rb_leftmost;
+
+	unsigned long dl_nr_running;
+};
+
 #ifdef CONFIG_SMP
 
 /*
@@ -427,6 +449,7 @@ struct rq {
 
 	struct cfs_rq cfs;
 	struct rt_rq rt;
+	struct dl_rq dl;
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
 	/* list of leaf cfs_rq on this cpu: */
@@ -957,6 +980,7 @@ static const u32 prio_to_wmult[40] = {
 #else
 #define ENQUEUE_WAKING		0
 #endif
+#define ENQUEUE_REPLENISH	8
 
 #define DEQUEUE_SLEEP		1
 
@@ -1012,6 +1036,7 @@ struct sched_class {
    for (class = sched_class_highest; class; class = class->next)
 
 extern const struct sched_class stop_sched_class;
+extern const struct sched_class dl_sched_class;
 extern const struct sched_class rt_sched_class;
 extern const struct sched_class fair_sched_class;
 extern const struct sched_class idle_sched_class;
@@ -1047,6 +1072,8 @@ extern void resched_cpu(int cpu);
 extern struct rt_bandwidth def_rt_bandwidth;
 extern void init_rt_bandwidth(struct rt_bandwidth *rt_b, u64 period, u64 runtime);
 
+extern void init_dl_task_timer(struct sched_dl_entity *dl_se);
+
 extern void update_idle_cpu_load(struct rq *this_rq);
 
 extern void init_task_runnable_average(struct task_struct *p);
@@ -1305,6 +1332,7 @@ extern void print_rt_stats(struct seq_file *m, int cpu);
 
 extern void init_cfs_rq(struct cfs_rq *cfs_rq);
 extern void init_rt_rq(struct rt_rq *rt_rq, struct rq *rq);
+extern void init_dl_rq(struct dl_rq *rt_rq, struct rq *rq);
 
 extern void account_cfs_bandwidth_used(int enabled, int was_enabled);
 
diff --git a/kernel/sched/stop_task.c b/kernel/sched/stop_task.c
index e08fbee..a5cef17 100644
--- a/kernel/sched/stop_task.c
+++ b/kernel/sched/stop_task.c
@@ -103,7 +103,7 @@ get_rr_interval_stop(struct rq *rq, struct task_struct *task)
  * Simple, special scheduling class for the per-CPU stop tasks:
  */
 const struct sched_class stop_sched_class = {
-	.next			= &rt_sched_class,
+	.next			= &dl_sched_class,
 
 	.enqueue_task		= enqueue_task_stop,
 	.dequeue_task		= dequeue_task_stop,
-- 
1.7.9.5

[PATCH 04/14] sched: SCHED_DEADLINE SMP-related data structures & logic.

[Juri Lelli]

Introduces data structures relevant for implementing dynamic
migration of -deadline tasks and the logic for checking if
runqueues are overloaded with -deadline tasks and for choosing
where a task should migrate, when it is the case.

Adds also dynamic migrations to SCHED_DEADLINE, so that tasks can
be moved among CPUs when necessary. It is also possible to bind a
task to a (set of) CPU(s), thus restricting its capability of
migrating, or forbidding migrations at all.

The very same approach used in sched_rt is utilised:
 - -deadline tasks are kept into CPU-specific runqueues,
 - -deadline tasks are migrated among runqueues to achieve the
   following:
    * on an M-CPU system the M earliest deadline ready tasks
      are always running;
    * affinity/cpusets settings of all the -deadline tasks is
      always respected.

Therefore, this very special form of "load balancing" is done with
an active method, i.e., the scheduler pushes or pulls tasks between
runqueues when they are woken up and/or (de)scheduled.
IOW, every time a preemption occurs, the descheduled task might be sent
to some other CPU (depending on its deadline) to continue executing
(push). On the other hand, every time a CPU becomes idle, it might pull
the second earliest deadline ready task from some other CPU.

To enforce this, a pull operation is always attempted before taking any
scheduling decision (pre_schedule()), as well as a push one after each
scheduling decision (post_schedule()). In addition, when a task arrives
or wakes up, the best CPU where to resume it is selected taking into
account its affinity mask, the system topology, but also its deadline.
E.g., from the scheduling point of view, the best CPU where to wake
up (and also where to push) a task is the one which is running the task
with the latest deadline among the M executing ones.

In order to facilitate these decisions, per-runqueue "caching" of the
deadlines of the currently running and of the first ready task is used.
Queued but not running tasks are also parked in another rb-tree to
speed-up pushes.

Signed-off-by: Juri Lelli <juri.lelli@gmail.com>
Signed-off-by: Dario Faggioli <raistlin@linux.it>
---
 include/linux/sched.h   |    2 +-
 kernel/sched/core.c     |   10 +-
 kernel/sched/deadline.c |  943 +++++++++++++++++++++++++++++++++++++++++++++--
 kernel/sched/rt.c       |    2 +-
 kernel/sched/sched.h    |   34 ++
 5 files changed, 960 insertions(+), 31 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 7370f3e..b071ca2 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1060,7 +1060,6 @@ struct sched_rt_entity {
 
 struct sched_dl_entity {
 	struct rb_node	rb_node;
-	int nr_cpus_allowed;
 
 	/*
 	 * Original scheduling parameters. Copied here from sched_param2
@@ -1175,6 +1174,7 @@ struct task_struct {
 	struct list_head tasks;
 #ifdef CONFIG_SMP
 	struct plist_node pushable_tasks;
+	struct rb_node pushable_dl_tasks;
 #endif
 
 	struct mm_struct *mm, *active_mm;
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index cfe15bfc..aa02240 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1737,6 +1737,7 @@ int sched_fork(struct task_struct *p)
 #endif
 #ifdef CONFIG_SMP
 	plist_node_init(&p->pushable_tasks, MAX_PRIO);
+	RB_CLEAR_NODE(&p->pushable_dl_tasks);
 #endif
 
 	put_cpu();
@@ -4418,6 +4419,7 @@ void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask)
 
 	cpumask_copy(&p->cpus_allowed, new_mask);
 	p->nr_cpus_allowed = cpumask_weight(new_mask);
+	p->nr_cpus_allowed = cpumask_weight(new_mask);
 }
 
 /*
@@ -5148,6 +5150,7 @@ static void free_rootdomain(struct rcu_head *rcu)
 	struct root_domain *rd = container_of(rcu, struct root_domain, rcu);
 
 	cpupri_cleanup(&rd->cpupri);
+	free_cpumask_var(rd->dlo_mask);
 	free_cpumask_var(rd->rto_mask);
 	free_cpumask_var(rd->online);
 	free_cpumask_var(rd->span);
@@ -5199,8 +5202,10 @@ static int init_rootdomain(struct root_domain *rd)
 		goto out;
 	if (!alloc_cpumask_var(&rd->online, GFP_KERNEL))
 		goto free_span;
-	if (!alloc_cpumask_var(&rd->rto_mask, GFP_KERNEL))
+	if (!alloc_cpumask_var(&rd->dlo_mask, GFP_KERNEL))
 		goto free_online;
+	if (!alloc_cpumask_var(&rd->rto_mask, GFP_KERNEL))
+		goto free_dlo_mask;
 
 	if (cpupri_init(&rd->cpupri) != 0)
 		goto free_rto_mask;
@@ -5208,6 +5213,8 @@ static int init_rootdomain(struct root_domain *rd)
 
 free_rto_mask:
 	free_cpumask_var(rd->rto_mask);
+free_dlo_mask:
+	free_cpumask_var(rd->dlo_mask);
 free_online:
 	free_cpumask_var(rd->online);
 free_span:
@@ -6542,6 +6549,7 @@ void __init sched_init_smp(void)
 	free_cpumask_var(non_isolated_cpus);
 
 	init_sched_rt_class();
+	init_sched_dl_class();
 }
 #else
 void __init sched_init_smp(void)
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index b1982a7..223cc3e 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -10,6 +10,7 @@
  * miss some of their deadlines), and won't affect any other task.
  *
  * Copyright (C) 2012 Dario Faggioli <raistlin@linux.it>,
+ *                    Juri Lelli <juri.lelli@gmail.com>,
  *                    Michael Trimarchi <michael@amarulasolutions.com>,
  *                    Fabio Checconi <fchecconi@gmail.com>
  */
@@ -20,6 +21,15 @@ static inline int dl_time_before(u64 a, u64 b)
 	return (s64)(a - b) < 0;
 }
 
+/*
+ * Tells if entity @a should preempt entity @b.
+ */
+static inline
+int dl_entity_preempt(struct sched_dl_entity *a, struct sched_dl_entity *b)
+{
+	return dl_time_before(a->deadline, b->deadline);
+}
+
 static inline struct task_struct *dl_task_of(struct sched_dl_entity *dl_se)
 {
 	return container_of(dl_se, struct task_struct, dl);
@@ -53,8 +63,166 @@ static inline int is_leftmost(struct task_struct *p, struct dl_rq *dl_rq)
 void init_dl_rq(struct dl_rq *dl_rq, struct rq *rq)
 {
 	dl_rq->rb_root = RB_ROOT;
+
+#ifdef CONFIG_SMP
+	/* zero means no -deadline tasks */
+	dl_rq->earliest_dl.curr = dl_rq->earliest_dl.next = 0;
+
+	dl_rq->dl_nr_migratory = 0;
+	dl_rq->overloaded = 0;
+	dl_rq->pushable_dl_tasks_root = RB_ROOT;
+#endif
+}
+
+#ifdef CONFIG_SMP
+
+static inline int dl_overloaded(struct rq *rq)
+{
+	return atomic_read(&rq->rd->dlo_count);
+}
+
+static inline void dl_set_overload(struct rq *rq)
+{
+	if (!rq->online)
+		return;
+
+	cpumask_set_cpu(rq->cpu, rq->rd->dlo_mask);
+	/*
+	 * Must be visible before the overload count is
+	 * set (as in sched_rt.c).
+	 */
+	wmb();
+	atomic_inc(&rq->rd->dlo_count);
+}
+
+static inline void dl_clear_overload(struct rq *rq)
+{
+	if (!rq->online)
+		return;
+
+	atomic_dec(&rq->rd->dlo_count);
+	cpumask_clear_cpu(rq->cpu, rq->rd->dlo_mask);
+}
+
+static void update_dl_migration(struct dl_rq *dl_rq)
+{
+	if (dl_rq->dl_nr_migratory && dl_rq->dl_nr_total > 1) {
+		if (!dl_rq->overloaded) {
+			dl_set_overload(rq_of_dl_rq(dl_rq));
+			dl_rq->overloaded = 1;
+		}
+	} else if (dl_rq->overloaded) {
+		dl_clear_overload(rq_of_dl_rq(dl_rq));
+		dl_rq->overloaded = 0;
+	}
+}
+
+static void inc_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
+{
+	struct task_struct *p = dl_task_of(dl_se);
+	dl_rq = &rq_of_dl_rq(dl_rq)->dl;
+
+	dl_rq->dl_nr_total++;
+	if (p->nr_cpus_allowed > 1)
+		dl_rq->dl_nr_migratory++;
+
+	update_dl_migration(dl_rq);
+}
+
+static void dec_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
+{
+	struct task_struct *p = dl_task_of(dl_se);
+	dl_rq = &rq_of_dl_rq(dl_rq)->dl;
+
+	dl_rq->dl_nr_total--;
+	if (p->nr_cpus_allowed > 1)
+		dl_rq->dl_nr_migratory--;
+
+	update_dl_migration(dl_rq);
+}
+
+/*
+ * The list of pushable -deadline task is not a plist, like in
+ * sched_rt.c, it is an rb-tree with tasks ordered by deadline.
+ */
+static void enqueue_pushable_dl_task(struct rq *rq, struct task_struct *p)
+{
+	struct dl_rq *dl_rq = &rq->dl;
+	struct rb_node **link = &dl_rq->pushable_dl_tasks_root.rb_node;
+	struct rb_node *parent = NULL;
+	struct task_struct *entry;
+	int leftmost = 1;
+
+	BUG_ON(!RB_EMPTY_NODE(&p->pushable_dl_tasks));
+
+	while (*link) {
+		parent = *link;
+		entry = rb_entry(parent, struct task_struct,
+				 pushable_dl_tasks);
+		if (dl_entity_preempt(&p->dl, &entry->dl))
+			link = &parent->rb_left;
+		else {
+			link = &parent->rb_right;
+			leftmost = 0;
+		}
+	}
+
+	if (leftmost)
+		dl_rq->pushable_dl_tasks_leftmost = &p->pushable_dl_tasks;
+
+	rb_link_node(&p->pushable_dl_tasks, parent, link);
+	rb_insert_color(&p->pushable_dl_tasks, &dl_rq->pushable_dl_tasks_root);
+}
+
+static void dequeue_pushable_dl_task(struct rq *rq, struct task_struct *p)
+{
+	struct dl_rq *dl_rq = &rq->dl;
+
+	if (RB_EMPTY_NODE(&p->pushable_dl_tasks))
+		return;
+
+	if (dl_rq->pushable_dl_tasks_leftmost == &p->pushable_dl_tasks) {
+		struct rb_node *next_node;
+
+		next_node = rb_next(&p->pushable_dl_tasks);
+		dl_rq->pushable_dl_tasks_leftmost = next_node;
+	}
+
+	rb_erase(&p->pushable_dl_tasks, &dl_rq->pushable_dl_tasks_root);
+	RB_CLEAR_NODE(&p->pushable_dl_tasks);
+}
+
+static inline int has_pushable_dl_tasks(struct rq *rq)
+{
+	return !RB_EMPTY_ROOT(&rq->dl.pushable_dl_tasks_root);
+}
+
+static int push_dl_task(struct rq *rq);
+
+#else
+
+static inline
+void enqueue_pushable_dl_task(struct rq *rq, struct task_struct *p)
+{
+}
+
+static inline
+void dequeue_pushable_dl_task(struct rq *rq, struct task_struct *p)
+{
+}
+
+static inline
+void inc_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
+{
+}
+
+static inline
+void dec_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
+{
 }
 
+#endif /* CONFIG_SMP */
+
 static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags);
 static void __dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags);
 static void check_preempt_curr_dl(struct rq *rq, struct task_struct *p,
@@ -307,6 +475,14 @@ static enum hrtimer_restart dl_task_timer(struct hrtimer *timer)
 			check_preempt_curr_dl(rq, p, 0);
 		else
 			resched_task(rq->curr);
+#ifdef CONFIG_SMP
+		/*
+		 * Queueing this task back might have overloaded rq,
+		 * check if we need to kick someone away.
+		 */
+		if (has_pushable_dl_tasks(rq))
+			push_dl_task(rq);
+#endif
 	}
 unlock:
 	raw_spin_unlock(&rq->lock);
@@ -394,6 +570,100 @@ static void update_curr_dl(struct rq *rq)
 	}
 }
 
+#ifdef CONFIG_SMP
+
+static struct task_struct *pick_next_earliest_dl_task(struct rq *rq, int cpu);
+
+static inline u64 next_deadline(struct rq *rq)
+{
+	struct task_struct *next = pick_next_earliest_dl_task(rq, rq->cpu);
+
+	if (next && dl_prio(next->prio))
+		return next->dl.deadline;
+	else
+		return 0;
+}
+
+static void inc_dl_deadline(struct dl_rq *dl_rq, u64 deadline)
+{
+	struct rq *rq = rq_of_dl_rq(dl_rq);
+
+	if (dl_rq->earliest_dl.curr == 0 ||
+	    dl_time_before(deadline, dl_rq->earliest_dl.curr)) {
+		/*
+		 * If the dl_rq had no -deadline tasks, or if the new task
+		 * has shorter deadline than the current one on dl_rq, we
+		 * know that the previous earliest becomes our next earliest,
+		 * as the new task becomes the earliest itself.
+		 */
+		dl_rq->earliest_dl.next = dl_rq->earliest_dl.curr;
+		dl_rq->earliest_dl.curr = deadline;
+	} else if (dl_rq->earliest_dl.next == 0 ||
+		   dl_time_before(deadline, dl_rq->earliest_dl.next)) {
+		/*
+		 * On the other hand, if the new -deadline task has a
+		 * a later deadline than the earliest one on dl_rq, but
+		 * it is earlier than the next (if any), we must
+		 * recompute the next-earliest.
+		 */
+		dl_rq->earliest_dl.next = next_deadline(rq);
+	}
+}
+
+static void dec_dl_deadline(struct dl_rq *dl_rq, u64 deadline)
+{
+	struct rq *rq = rq_of_dl_rq(dl_rq);
+
+	/*
+	 * Since we may have removed our earliest (and/or next earliest)
+	 * task we must recompute them.
+	 */
+	if (!dl_rq->dl_nr_running) {
+		dl_rq->earliest_dl.curr = 0;
+		dl_rq->earliest_dl.next = 0;
+	} else {
+		struct rb_node *leftmost = dl_rq->rb_leftmost;
+		struct sched_dl_entity *entry;
+
+		entry = rb_entry(leftmost, struct sched_dl_entity, rb_node);
+		dl_rq->earliest_dl.curr = entry->deadline;
+		dl_rq->earliest_dl.next = next_deadline(rq);
+	}
+}
+
+#else
+
+static inline void inc_dl_deadline(struct dl_rq *dl_rq, u64 deadline) {}
+static inline void dec_dl_deadline(struct dl_rq *dl_rq, u64 deadline) {}
+
+#endif /* CONFIG_SMP */
+
+static inline
+void inc_dl_tasks(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
+{
+	int prio = dl_task_of(dl_se)->prio;
+	u64 deadline = dl_se->deadline;
+
+	WARN_ON(!dl_prio(prio));
+	dl_rq->dl_nr_running++;
+
+	inc_dl_deadline(dl_rq, deadline);
+	inc_dl_migration(dl_se, dl_rq);
+}
+
+static inline
+void dec_dl_tasks(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
+{
+	int prio = dl_task_of(dl_se)->prio;
+
+	WARN_ON(!dl_prio(prio));
+	WARN_ON(!dl_rq->dl_nr_running);
+	dl_rq->dl_nr_running--;
+
+	dec_dl_deadline(dl_rq, dl_se->deadline);
+	dec_dl_migration(dl_se, dl_rq);
+}
+
 static void __enqueue_dl_entity(struct sched_dl_entity *dl_se)
 {
 	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
@@ -421,7 +691,7 @@ static void __enqueue_dl_entity(struct sched_dl_entity *dl_se)
 	rb_link_node(&dl_se->rb_node, parent, link);
 	rb_insert_color(&dl_se->rb_node, &dl_rq->rb_root);
 
-	dl_rq->dl_nr_running++;
+	inc_dl_tasks(dl_se, dl_rq);
 }
 
 static void __dequeue_dl_entity(struct sched_dl_entity *dl_se)
@@ -441,7 +711,7 @@ static void __dequeue_dl_entity(struct sched_dl_entity *dl_se)
 	rb_erase(&dl_se->rb_node, &dl_rq->rb_root);
 	RB_CLEAR_NODE(&dl_se->rb_node);
 
-	dl_rq->dl_nr_running--;
+	dec_dl_tasks(dl_se, dl_rq);
 }
 
 static void
@@ -479,12 +749,17 @@ static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags)
 		return;
 
 	enqueue_dl_entity(&p->dl, flags);
+
+	if (!task_current(rq, p) && p->nr_cpus_allowed > 1)
+		enqueue_pushable_dl_task(rq, p);
+
 	inc_nr_running(rq);
 }
 
 static void __dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags)
 {
 	dequeue_dl_entity(&p->dl);
+	dequeue_pushable_dl_task(rq, p);
 }
 
 static void dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags)
@@ -518,6 +793,77 @@ static void yield_task_dl(struct rq *rq)
 	update_curr_dl(rq);
 }
 
+#ifdef CONFIG_SMP
+
+static int find_later_rq(struct task_struct *task);
+static int latest_cpu_find(struct cpumask *span,
+			   struct task_struct *task,
+			   struct cpumask *later_mask);
+
+static int
+select_task_rq_dl(struct task_struct *p, int sd_flag, int flags)
+{
+	struct task_struct *curr;
+	struct rq *rq;
+	int cpu;
+
+	cpu = task_cpu(p);
+
+	if (sd_flag != SD_BALANCE_WAKE && sd_flag != SD_BALANCE_FORK)
+		goto out;
+
+	rq = cpu_rq(cpu);
+
+	rcu_read_lock();
+	curr = ACCESS_ONCE(rq->curr); /* unlocked access */
+
+	/*
+	 * If we are dealing with a -deadline task, we must
+	 * decide where to wake it up.
+	 * If it has a later deadline and the current task
+	 * on this rq can't move (provided the waking task
+	 * can!) we prefer to send it somewhere else. On the
+	 * other hand, if it has a shorter deadline, we
+	 * try to make it stay here, it might be important.
+	 */
+	if (unlikely(dl_task(curr)) &&
+	    (curr->nr_cpus_allowed < 2 ||
+	     !dl_entity_preempt(&p->dl, &curr->dl)) &&
+	    (p->nr_cpus_allowed > 1)) {
+		int target = find_later_rq(p);
+
+		if (target != -1)
+			cpu = target;
+	}
+	rcu_read_unlock();
+
+out:
+	return cpu;
+}
+
+static void check_preempt_equal_dl(struct rq *rq, struct task_struct *p)
+{
+	/*
+	 * Current can't be migrated, useless to reschedule,
+	 * let's hope p can move out.
+	 */
+	if (rq->curr->nr_cpus_allowed == 1 ||
+	    latest_cpu_find(rq->rd->span, rq->curr, NULL) == -1)
+		return;
+
+	/*
+	 * p is migratable, so let's not schedule it and
+	 * see if it is pushed or pulled somewhere else.
+	 */
+	if (p->nr_cpus_allowed != 1 &&
+	    latest_cpu_find(rq->rd->span, p, NULL) != -1)
+		return;
+
+	resched_task(rq->curr);
+}
+
+#endif /* CONFIG_SMP */
+
 /*
  * Only called when both the current and waking task are -deadline
  * tasks.
@@ -525,8 +871,20 @@ static void yield_task_dl(struct rq *rq)
 static void check_preempt_curr_dl(struct rq *rq, struct task_struct *p,
 				  int flags)
 {
-	if (dl_time_before(p->dl.deadline, rq->curr->dl.deadline))
+	if (dl_entity_preempt(&p->dl, &rq->curr->dl)) {
 		resched_task(rq->curr);
+		return;
+	}
+
+#ifdef CONFIG_SMP
+	/*
+	 * In the unlikely case current and p have the same deadline
+	 * let us try to decide what's the best thing to do...
+	 */
+	if ((s64)(p->dl.deadline - rq->curr->dl.deadline) == 0 &&
+	    !need_resched())
+		check_preempt_equal_dl(rq, p);
+#endif /* CONFIG_SMP */
 }
 
 #ifdef CONFIG_SCHED_HRTICK
@@ -569,17 +927,30 @@ struct task_struct *pick_next_task_dl(struct rq *rq)
 	BUG_ON(!dl_se);
 
 	p = dl_task_of(dl_se);
-	p->se.exec_start = rq->clock;
+	p->se.exec_start = rq->clock_task;
+
+	/* Running task will never be pushed. */
+	if (p)
+		dequeue_pushable_dl_task(rq, p);
+
 #ifdef CONFIG_SCHED_HRTICK
 	if (hrtick_enabled(rq))
 		start_hrtick_dl(rq, p);
 #endif
+
+#ifdef CONFIG_SMP
+	rq->post_schedule = has_pushable_dl_tasks(rq);
+#endif /* CONFIG_SMP */
+
 	return p;
 }
 
 static void put_prev_task_dl(struct rq *rq, struct task_struct *p)
 {
 	update_curr_dl(rq);
+
+	if (on_dl_rq(&p->dl) && p->nr_cpus_allowed > 1)
+		enqueue_pushable_dl_task(rq, p);
 }
 
 static void task_tick_dl(struct rq *rq, struct task_struct *p, int queued)
@@ -612,17 +983,512 @@ static void set_curr_task_dl(struct rq *rq)
 {
 	struct task_struct *p = rq->curr;
 
-	p->se.exec_start = rq->clock;
+	p->se.exec_start = rq->clock_task;
+
+	/* You can't push away the running task */
+	dequeue_pushable_dl_task(rq, p);
+}
+
+#ifdef CONFIG_SMP
+
+/* Only try algorithms three times */
+#define DL_MAX_TRIES 3
+
+static int pick_dl_task(struct rq *rq, struct task_struct *p, int cpu)
+{
+	if (!task_running(rq, p) &&
+	    (cpu < 0 || cpumask_test_cpu(cpu, &p->cpus_allowed)) &&
+	    (p->nr_cpus_allowed > 1))
+		return 1;
+
+	return 0;
 }
 
+/* Returns the second earliest -deadline task, NULL otherwise */
+static struct task_struct *pick_next_earliest_dl_task(struct rq *rq, int cpu)
+{
+	struct rb_node *next_node = rq->dl.rb_leftmost;
+	struct sched_dl_entity *dl_se;
+	struct task_struct *p = NULL;
+
+next_node:
+	next_node = rb_next(next_node);
+	if (next_node) {
+		dl_se = rb_entry(next_node, struct sched_dl_entity, rb_node);
+		p = dl_task_of(dl_se);
+
+		if (pick_dl_task(rq, p, cpu))
+			return p;
+
+		goto next_node;
+	}
+
+	return NULL;
+}
+
+static int latest_cpu_find(struct cpumask *span,
+			   struct task_struct *task,
+			   struct cpumask *later_mask)
+{
+	const struct sched_dl_entity *dl_se = &task->dl;
+	int cpu, found = -1, best = 0;
+	u64 max_dl = 0;
+
+	for_each_cpu(cpu, span) {
+		struct rq *rq = cpu_rq(cpu);
+		struct dl_rq *dl_rq = &rq->dl;
+
+		if (cpumask_test_cpu(cpu, &task->cpus_allowed) &&
+		    (!dl_rq->dl_nr_running || dl_time_before(dl_se->deadline,
+		     dl_rq->earliest_dl.curr))) {
+			if (later_mask)
+				cpumask_set_cpu(cpu, later_mask);
+			if (!best && !dl_rq->dl_nr_running) {
+				best = 1;
+				found = cpu;
+			} else if (!best &&
+				   dl_time_before(max_dl,
+						  dl_rq->earliest_dl.curr)) {
+				max_dl = dl_rq->earliest_dl.curr;
+				found = cpu;
+			}
+		} else if (later_mask)
+			cpumask_clear_cpu(cpu, later_mask);
+	}
+
+	return found;
+}
+
+static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask_dl);
+
+static int find_later_rq(struct task_struct *task)
+{
+	struct sched_domain *sd;
+	struct cpumask *later_mask = __get_cpu_var(local_cpu_mask_dl);
+	int this_cpu = smp_processor_id();
+	int best_cpu, cpu = task_cpu(task);
+
+	/* Make sure the mask is initialized first */
+	if (unlikely(!later_mask))
+		return -1;
+
+	if (task->nr_cpus_allowed == 1)
+		return -1;
+
+	best_cpu = latest_cpu_find(task_rq(task)->rd->span, task, later_mask);
+	if (best_cpu == -1)
+		return -1;
+
+	/*
+	 * If we are here, some target has been found,
+	 * the most suitable of which is cached in best_cpu.
+	 * This is, among the runqueues where the current tasks
+	 * have later deadlines than the task's one, the rq
+	 * with the latest possible one.
+	 *
+	 * Now we check how well this matches with task's
+	 * affinity and system topology.
+	 *
+	 * The last cpu where the task run is our first
+	 * guess, since it is most likely cache-hot there.
+	 */
+	if (cpumask_test_cpu(cpu, later_mask))
+		return cpu;
+	/*
+	 * Check if this_cpu is to be skipped (i.e., it is
+	 * not in the mask) or not.
+	 */
+	if (!cpumask_test_cpu(this_cpu, later_mask))
+		this_cpu = -1;
+
+	rcu_read_lock();
+	for_each_domain(cpu, sd) {
+		if (sd->flags & SD_WAKE_AFFINE) {
+
+			/*
+			 * If possible, preempting this_cpu is
+			 * cheaper than migrating.
+			 */
+			if (this_cpu != -1 &&
+			    cpumask_test_cpu(this_cpu, sched_domain_span(sd))) {
+				rcu_read_unlock();
+				return this_cpu;
+			}
+
+			/*
+			 * Last chance: if best_cpu is valid and is
+			 * in the mask, that becomes our choice.
+			 */
+			if (best_cpu < nr_cpu_ids &&
+			    cpumask_test_cpu(best_cpu, sched_domain_span(sd))) {
+				rcu_read_unlock();
+				return best_cpu;
+			}
+		}
+	}
+	rcu_read_unlock();
+
+	/*
+	 * At this point, all our guesses failed, we just return
+	 * 'something', and let the caller sort the things out.
+	 */
+	if (this_cpu != -1)
+		return this_cpu;
+
+	cpu = cpumask_any(later_mask);
+	if (cpu < nr_cpu_ids)
+		return cpu;
+
+	return -1;
+}
+
+/* Locks the rq it finds */
+static struct rq *find_lock_later_rq(struct task_struct *task, struct rq *rq)
+{
+	struct rq *later_rq = NULL;
+	int tries;
+	int cpu;
+
+	for (tries = 0; tries < DL_MAX_TRIES; tries++) {
+		cpu = find_later_rq(task);
+
+		if ((cpu == -1) || (cpu == rq->cpu))
+			break;
+
+		later_rq = cpu_rq(cpu);
+
+		/* Retry if something changed. */
+		if (double_lock_balance(rq, later_rq)) {
+			if (unlikely(task_rq(task) != rq ||
+				     !cpumask_test_cpu(later_rq->cpu,
+				                       &task->cpus_allowed) ||
+				     task_running(rq, task) || !task->on_rq)) {
+				double_unlock_balance(rq, later_rq);
+				later_rq = NULL;
+				break;
+			}
+		}
+
+		/*
+		 * If the rq we found has no -deadline task, or
+		 * its earliest one has a later deadline than our
+		 * task, the rq is a good one.
+		 */
+		if (!later_rq->dl.dl_nr_running ||
+		    dl_time_before(task->dl.deadline,
+				   later_rq->dl.earliest_dl.curr))
+			break;
+
+		/* Otherwise we try again. */
+		double_unlock_balance(rq, later_rq);
+		later_rq = NULL;
+	}
+
+	return later_rq;
+}
+
+static struct task_struct *pick_next_pushable_dl_task(struct rq *rq)
+{
+	struct task_struct *p;
+
+	if (!has_pushable_dl_tasks(rq))
+		return NULL;
+
+	p = rb_entry(rq->dl.pushable_dl_tasks_leftmost,
+		     struct task_struct, pushable_dl_tasks);
+
+	BUG_ON(rq->cpu != task_cpu(p));
+	BUG_ON(task_current(rq, p));
+	BUG_ON(p->nr_cpus_allowed <= 1);
+
+	BUG_ON(!p->se.on_rq);
+	BUG_ON(!dl_task(p));
+
+	return p;
+}
+
+/*
+ * See if the non running -deadline tasks on this rq
+ * can be sent to some other CPU where they can preempt
+ * and start executing.
+ */
+static int push_dl_task(struct rq *rq)
+{
+	struct task_struct *next_task;
+	struct rq *later_rq;
+
+	if (!rq->dl.overloaded)
+		return 0;
+
+	next_task = pick_next_pushable_dl_task(rq);
+	if (!next_task)
+		return 0;
+
+retry:
+	if (unlikely(next_task == rq->curr)) {
+		WARN_ON(1);
+		return 0;
+	}
+
+	/*
+	 * If next_task preempts rq->curr, and rq->curr
+	 * can move away, it makes sense to just reschedule
+	 * without going further in pushing next_task.
+	 */
+	if (dl_task(rq->curr) &&
+	    dl_time_before(next_task->dl.deadline, rq->curr->dl.deadline) &&
+	    rq->curr->nr_cpus_allowed > 1) {
+		resched_task(rq->curr);
+		return 0;
+	}
+
+	/* We might release rq lock */
+	get_task_struct(next_task);
+
+	/* Will lock the rq it'll find */
+	later_rq = find_lock_later_rq(next_task, rq);
+	if (!later_rq) {
+		struct task_struct *task;
+
+		/*
+		 * We must check all this again, since
+		 * find_lock_later_rq releases rq->lock and it is
+		 * then possible that next_task has migrated.
+		 */
+		task = pick_next_pushable_dl_task(rq);
+		if (task_cpu(next_task) == rq->cpu && task == next_task) {
+			/*
+			 * The task is still there. We don't try
+			 * again, some other cpu will pull it when ready.
+			 */
+			dequeue_pushable_dl_task(rq, next_task);
+			goto out;
+		}
+
+		if (!task)
+			/* No more tasks */
+			goto out;
+
+		put_task_struct(next_task);
+		next_task = task;
+		goto retry;
+	}
+
+	deactivate_task(rq, next_task, 0);
+	set_task_cpu(next_task, later_rq->cpu);
+	activate_task(later_rq, next_task, 0);
+
+	resched_task(later_rq->curr);
+
+	double_unlock_balance(rq, later_rq);
+
+out:
+	put_task_struct(next_task);
+
+	return 1;
+}
+
+static void push_dl_tasks(struct rq *rq)
+{
+	/* Terminates as it moves a -deadline task */
+	while (push_dl_task(rq))
+		;
+}
+
+static int pull_dl_task(struct rq *this_rq)
+{
+	int this_cpu = this_rq->cpu, ret = 0, cpu;
+	struct task_struct *p;
+	struct rq *src_rq;
+	u64 dmin = LONG_MAX;
+
+	if (likely(!dl_overloaded(this_rq)))
+		return 0;
+
+	for_each_cpu(cpu, this_rq->rd->dlo_mask) {
+		if (this_cpu == cpu)
+			continue;
+
+		src_rq = cpu_rq(cpu);
+
+		/*
+		 * It looks racy, abd it is! However, as in sched_rt.c,
+		 * we are fine with this.
+		 */
+		if (this_rq->dl.dl_nr_running &&
+		    dl_time_before(this_rq->dl.earliest_dl.curr,
+				   src_rq->dl.earliest_dl.next))
+			continue;
+
+		/* Might drop this_rq->lock */
+		double_lock_balance(this_rq, src_rq);
+
+		/*
+		 * If there are no more pullable tasks on the
+		 * rq, we're done with it.
+		 */
+		if (src_rq->dl.dl_nr_running <= 1)
+			goto skip;
+
+		p = pick_next_earliest_dl_task(src_rq, this_cpu);
+
+		/*
+		 * We found a task to be pulled if:
+		 *  - it preempts our current (if there's one),
+		 *  - it will preempt the last one we pulled (if any).
+		 */
+		if (p && dl_time_before(p->dl.deadline, dmin) &&
+		    (!this_rq->dl.dl_nr_running ||
+		     dl_time_before(p->dl.deadline,
+				    this_rq->dl.earliest_dl.curr))) {
+			WARN_ON(p == src_rq->curr);
+			WARN_ON(!p->se.on_rq);
+
+			/*
+			 * Then we pull iff p has actually an earlier
+			 * deadline than the current task of its runqueue.
+			 */
+			if (dl_time_before(p->dl.deadline,
+					   src_rq->curr->dl.deadline))
+				goto skip;
+
+			ret = 1;
+
+			deactivate_task(src_rq, p, 0);
+			set_task_cpu(p, this_cpu);
+			activate_task(this_rq, p, 0);
+			dmin = p->dl.deadline;
+
+			/* Is there any other task even earlier? */
+		}
+skip:
+		double_unlock_balance(this_rq, src_rq);
+	}
+
+	return ret;
+}
+
+static void pre_schedule_dl(struct rq *rq, struct task_struct *prev)
+{
+	/* Try to pull other tasks here */
+	if (dl_task(prev))
+		pull_dl_task(rq);
+}
+
+static void post_schedule_dl(struct rq *rq)
+{
+	push_dl_tasks(rq);
+}
+
+/*
+ * Since the task is not running and a reschedule is not going to happen
+ * anytime soon on its runqueue, we try pushing it away now.
+ */
+static void task_woken_dl(struct rq *rq, struct task_struct *p)
+{
+	if (!task_running(rq, p) &&
+	    !test_tsk_need_resched(rq->curr) &&
+	    has_pushable_dl_tasks(rq) &&
+	    p->nr_cpus_allowed > 1 &&
+	    dl_task(rq->curr) &&
+	    (rq->curr->nr_cpus_allowed < 2 ||
+	     dl_entity_preempt(&rq->curr->dl, &p->dl))) {
+		push_dl_tasks(rq);
+	}
+}
+
+static void set_cpus_allowed_dl(struct task_struct *p,
+				const struct cpumask *new_mask)
+{
+	struct rq *rq;
+	int weight;
+
+	BUG_ON(!dl_task(p));
+
+	/*
+	 * Update only if the task is actually running (i.e.,
+	 * it is on the rq AND it is not throttled).
+	 */
+	if (!on_dl_rq(&p->dl))
+		return;
+
+	weight = cpumask_weight(new_mask);
+
+	/*
+	 * Only update if the process changes its state from whether it
+	 * can migrate or not.
+	 */
+	if ((p->nr_cpus_allowed > 1) == (weight > 1))
+		return;
+
+	rq = task_rq(p);
+
+	/*
+	 * The process used to be able to migrate OR it can now migrate
+	 */
+	if (weight <= 1) {
+		if (!task_current(rq, p))
+			dequeue_pushable_dl_task(rq, p);
+		BUG_ON(!rq->dl.dl_nr_migratory);
+		rq->dl.dl_nr_migratory--;
+	} else {
+		if (!task_current(rq, p))
+			enqueue_pushable_dl_task(rq, p);
+		rq->dl.dl_nr_migratory++;
+	}
+	
+	update_dl_migration(&rq->dl);
+}
+
+/* Assumes rq->lock is held */
+static void rq_online_dl(struct rq *rq)
+{
+	if (rq->dl.overloaded)
+		dl_set_overload(rq);
+}
+
+/* Assumes rq->lock is held */
+static void rq_offline_dl(struct rq *rq)
+{
+	if (rq->dl.overloaded)
+		dl_clear_overload(rq);
+}
+
+void init_sched_dl_class(void)
+{
+	unsigned int i;
+
+	for_each_possible_cpu(i)
+		zalloc_cpumask_var_node(&per_cpu(local_cpu_mask_dl, i),
+					GFP_KERNEL, cpu_to_node(i));
+}
+
+#endif /* CONFIG_SMP */
+
 static void switched_from_dl(struct rq *rq, struct task_struct *p)
 {
-	if (hrtimer_active(&p->dl.dl_timer))
+	if (hrtimer_active(&p->dl.dl_timer) && !dl_policy(p->policy))
 		hrtimer_try_to_cancel(&p->dl.dl_timer);
+
+#ifdef CONFIG_SMP
+	/*
+	 * Since this might be the only -deadline task on the rq,
+	 * this is the right place to try to pull some other one
+	 * from an overloaded cpu, if any.
+	 */
+	if (!rq->dl.dl_nr_running)
+		pull_dl_task(rq);
+#endif
 }
 
+/*
+ * When switching to -deadline, we may overload the rq, then
+ * we try to push someone off, if possible.
+ */
 static void switched_to_dl(struct rq *rq, struct task_struct *p)
 {
+	int check_resched = 1;
+
 	/*
 	 * If p is throttled, don't consider the possibility
 	 * of preempting rq->curr, the check will be done right
@@ -632,37 +1498,53 @@ static void switched_to_dl(struct rq *rq, struct task_struct *p)
 		return;
 
 	if (!p->on_rq || rq->curr != p) {
-		if (task_has_dl_policy(rq->curr))
+#ifdef CONFIG_SMP
+		if (rq->dl.overloaded && push_dl_task(rq) && rq != task_rq(p))
+			/* Only reschedule if pushing failed */
+			check_resched = 0;
+#endif /* CONFIG_SMP */
+		if (check_resched && task_has_dl_policy(rq->curr))
 			check_preempt_curr_dl(rq, p, 0);
-		else
-			resched_task(rq->curr);
 	}
 }
 
+/*
+ * If the scheduling parameters of a -deadline task changed,
+ * a push or pull operation might be needed.
+ */
 static void prio_changed_dl(struct rq *rq, struct task_struct *p,
 			    int oldprio)
 {
-	switched_to_dl(rq, p);
-}
-
+	if (p->on_rq || rq->curr == p) {
 #ifdef CONFIG_SMP
-static int
-select_task_rq_dl(struct task_struct *p, int sd_flag, int flags)
-{
-	return task_cpu(p);
-}
-
-static void set_cpus_allowed_dl(struct task_struct *p,
-				const struct cpumask *new_mask)
-{
-	int weight = cpumask_weight(new_mask);
-
-	BUG_ON(!dl_task(p));
-
-	cpumask_copy(&p->cpus_allowed, new_mask);
-	p->dl.nr_cpus_allowed = weight;
+		/*
+		 * This might be too much, but unfortunately
+		 * we don't have the old deadline value, and
+		 * we can't argue if the task is increasing
+		 * or lowering its prio, so...
+		 */
+		if (!rq->dl.overloaded)
+			pull_dl_task(rq);
+
+		/*
+		 * If we now have a earlier deadline task than p,
+		 * then reschedule, provided p is still on this
+		 * runqueue.
+		 */
+		if (dl_time_before(rq->dl.earliest_dl.curr, p->dl.deadline) &&
+		    rq->curr == p)
+			resched_task(p);
+#else
+		/*
+		 * Again, we don't know if p has a earlier
+		 * or later deadline, so let's blindly set a
+		 * (maybe not needed) rescheduling point.
+		 */
+		resched_task(p);
+#endif /* CONFIG_SMP */
+	} else
+		switched_to_dl(rq, p);
 }
-#endif
 
 const struct sched_class dl_sched_class = {
 	.next			= &rt_sched_class,
@@ -679,6 +1561,11 @@ const struct sched_class dl_sched_class = {
 	.select_task_rq		= select_task_rq_dl,
 
 	.set_cpus_allowed       = set_cpus_allowed_dl,
+	.rq_online              = rq_online_dl,
+	.rq_offline             = rq_offline_dl,
+	.pre_schedule		= pre_schedule_dl,
+	.post_schedule		= post_schedule_dl,
+	.task_woken		= task_woken_dl,
 #endif
 
 	.set_curr_task		= set_curr_task_dl,
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 01970c8..f7c4881 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -1720,7 +1720,7 @@ static void task_woken_rt(struct rq *rq, struct task_struct *p)
 	    !test_tsk_need_resched(rq->curr) &&
 	    has_pushable_tasks(rq) &&
 	    p->nr_cpus_allowed > 1 &&
-	    rt_task(rq->curr) &&
+	    (dl_task(rq->curr) || rt_task(rq->curr)) &&
 	    (rq->curr->nr_cpus_allowed < 2 ||
 	     rq->curr->prio <= p->prio))
 		push_rt_tasks(rq);
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index ba97476..70d0030 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -383,6 +383,31 @@ struct dl_rq {
 	struct rb_node *rb_leftmost;
 
 	unsigned long dl_nr_running;
+
+#ifdef CONFIG_SMP
+	/*
+	 * Deadline values of the currently executing and the
+	 * earliest ready task on this rq. Caching these facilitates
+	 * the decision wether or not a ready but not running task
+	 * should migrate somewhere else.
+	 */
+	struct {
+		u64 curr;
+		u64 next;
+	} earliest_dl;
+
+	unsigned long dl_nr_migratory;
+	unsigned long dl_nr_total;
+	int overloaded;
+
+	/*
+	 * Tasks on this rq that can be pushed away. They are kept in
+	 * an rb-tree, ordered by tasks' deadlines, with caching
+	 * of the leftmost (earliest deadline) element.
+	 */
+	struct rb_root pushable_dl_tasks_root;
+	struct rb_node *pushable_dl_tasks_leftmost;
+#endif
 };
 
 #ifdef CONFIG_SMP
@@ -403,6 +428,13 @@ struct root_domain {
 	cpumask_var_t online;
 
 	/*
+	 * The bit corresponding to a CPU gets set here if such CPU has more
+	 * than one runnable -deadline task (as it is below for RT tasks).
+	 */
+	cpumask_var_t dlo_mask;
+	atomic_t dlo_count;
+
+	/*
 	 * The "RT overload" flag: it gets set if a CPU has more than
 	 * one runnable RT task.
 	 */
@@ -1063,6 +1095,8 @@ static inline void idle_balance(int cpu, struct rq *rq)
 extern void sysrq_sched_debug_show(void);
 extern void sched_init_granularity(void);
 extern void update_max_interval(void);
+
+extern void init_sched_dl_class(void);
 extern void init_sched_rt_class(void);
 extern void init_sched_fair_class(void);
 
-- 
1.7.9.5

[PATCH 05/14] sched: SCHED_DEADLINE avg_update accounting.

[Juri Lelli]

From: Dario Faggioli <raistlin@linux.it>

Make the core scheduler and load balancer aware of the load
produced by -deadline tasks, by updating the moving average
like for sched_rt.

Signed-off-by: Dario Faggioli <raistlin@linux.it>
Signed-off-by: Juri Lelli <juri.lelli@gmail.com>
---
 kernel/sched/deadline.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 223cc3e..d3334fc 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -557,6 +557,8 @@ static void update_curr_dl(struct rq *rq)
 	curr->se.exec_start = rq->clock_task;
 	cpuacct_charge(curr, delta_exec);
 
+	sched_rt_avg_update(rq, delta_exec);
+
 	dl_se->runtime -= delta_exec;
 	if (dl_runtime_exceeded(rq, dl_se)) {
 		__dequeue_task_dl(rq, curr, 0);
-- 
1.7.9.5

[PATCH 06/14] sched: add period support for -deadline tasks.

[Juri Lelli]

From: Harald Gustafsson <harald.gustafsson@ericsson.com>

Make it possible to specify a period (different or equal than
deadline) for -deadline tasks.

Signed-off-by: Harald Gustafsson <harald.gustafsson@ericsson.com>
Signed-off-by: Dario Faggioli <raistlin@linux.it>
Signed-off-by: Juri Lelli <juri.lelli@gmail.com>
---
 include/linux/sched.h   |    1 +
 kernel/sched/core.c     |   15 ++++++++++++---
 kernel/sched/deadline.c |   10 +++++++---
 3 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index b071ca2..424f64a 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1068,6 +1068,7 @@ struct sched_dl_entity {
 	 */
 	u64 dl_runtime;		/* maximum runtime for each instance	*/
 	u64 dl_deadline;	/* relative deadline of each instance	*/
+	u64 dl_period;		/* separation of two instances (period) */
 
 	/*
 	 * Actual scheduling parameters. Initialized with the values above,
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index aa02240..2ec8a93 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1617,6 +1617,7 @@ static void __sched_fork(struct task_struct *p)
 	hrtimer_init(&p->dl.dl_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 	p->dl.dl_runtime = p->dl.runtime = 0;
 	p->dl.dl_deadline = p->dl.deadline = 0;
+	p->dl.dl_period = 0;
 	p->dl.flags = 0;
 
 	INIT_LIST_HEAD(&p->rt.run_list);
@@ -3304,6 +3305,10 @@ __setparam_dl(struct task_struct *p, const struct sched_param2 *param2)
 	init_dl_task_timer(dl_se);
 	dl_se->dl_runtime = param2->sched_runtime;
 	dl_se->dl_deadline = param2->sched_deadline;
+	if (param2->sched_period != 0)
+		dl_se->dl_period = param2->sched_period;
+	else
+		dl_se->dl_period = dl_se->dl_deadline;
 	dl_se->flags = param2->sched_flags;
 	dl_se->dl_throttled = 0;
 	dl_se->dl_new = 1;
@@ -3317,19 +3322,23 @@ __getparam_dl(struct task_struct *p, struct sched_param2 *param2)
 	param2->sched_priority = p->rt_priority;
 	param2->sched_runtime = dl_se->dl_runtime;
 	param2->sched_deadline = dl_se->dl_deadline;
+	param2->sched_period = dl_se->dl_period;
 	param2->sched_flags = dl_se->flags;
 }
 
 /*
  * This function validates the new parameters of a -deadline task.
  * We ask for the deadline not being zero, and greater or equal
- * than the runtime.
+ * than the runtime, as well as the period of being zero or
+ * greater than deadline.
  */
 static bool
 __checkparam_dl(const struct sched_param2 *prm)
 {
-	return prm && (&prm->sched_deadline) != 0 &&
-	       (s64)(&prm->sched_deadline - &prm->sched_runtime) >= 0;
+	return prm && prm->sched_deadline != 0 &&
+	       (prm->sched_period == 0 ||
+		(s64)(prm->sched_period - prm->sched_deadline) >= 0) &&
+	       (s64)(prm->sched_deadline - prm->sched_runtime) >= 0;
 }
 
 /*
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index d3334fc..92546f3 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -287,7 +287,7 @@ static void replenish_dl_entity(struct sched_dl_entity *dl_se)
 	 * arbitrary large.
 	 */
 	while (dl_se->runtime <= 0) {
-		dl_se->deadline += dl_se->dl_deadline;
+		dl_se->deadline += dl_se->dl_period;
 		dl_se->runtime += dl_se->dl_runtime;
 	}
 
@@ -327,9 +327,13 @@ static void replenish_dl_entity(struct sched_dl_entity *dl_se)
  *
  * This function returns true if:
  *
- *   runtime / (deadline - t) > dl_runtime / dl_deadline ,
+ *   runtime / (deadline - t) > dl_runtime / dl_period ,
  *
  * IOW we can't recycle current parameters.
+ *
+ * Notice that the bandwidth check is done against the period. For
+ * task with deadline equal to period this is the same of using
+ * dl_deadline instead of dl_period in the equation above.
  */
 static bool dl_entity_overflow(struct sched_dl_entity *dl_se, u64 t)
 {
@@ -353,7 +357,7 @@ static bool dl_entity_overflow(struct sched_dl_entity *dl_se, u64 t)
 	 * of anything below microseconds resolution is actually fiction
 	 * (but still we want to give the user that illusion >;).
 	 */
-	left = (dl_se->dl_deadline >> 10) * (dl_se->runtime >> 10);
+	left = (dl_se->dl_period >> 10) * (dl_se->runtime >> 10);
 	right = ((dl_se->deadline - t) >> 10) * (dl_se->dl_runtime >> 10);
 
 	return dl_time_before(right, left);
-- 
1.7.9.5

[PATCH 07/14] sched: add schedstats for -deadline tasks.

[Juri Lelli]

From: Dario Faggioli <raistlin@linux.it>

Add some typical sched-debug output to dl_rq(s) and some
schedstats to -deadline tasks.

Signed-off-by: Dario Faggioli <raistlin@linux.it>
Signed-off-by: Juri Lelli <juri.lelli@gmail.com>
---
 include/linux/sched.h   |   13 +++++++++++++
 kernel/sched/deadline.c |   45 +++++++++++++++++++++++++++++++++++++++++++++
 kernel/sched/debug.c    |   46 ++++++++++++++++++++++++++++++++++++++++++++++
 kernel/sched/sched.h    |    9 ++++++++-
 4 files changed, 112 insertions(+), 1 deletion(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 424f64a..c8bfabc 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1058,6 +1058,15 @@ struct sched_rt_entity {
 #endif
 };
 
+#ifdef CONFIG_SCHEDSTATS
+struct sched_stats_dl {
+	u64			last_dmiss;
+	u64			last_rorun;
+	u64			dmiss_max;
+	u64			rorun_max;
+};
+#endif
+
 struct sched_dl_entity {
 	struct rb_node	rb_node;
 
@@ -1097,6 +1106,10 @@ struct sched_dl_entity {
 	 * own bandwidth to be enforced, thus we need one timer per task.
 	 */
 	struct hrtimer dl_timer;
+
+#ifdef CONFIG_SCHEDSTATS
+	struct sched_stats_dl stats;
+#endif
 };
 
 struct rcu_node;
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 92546f3..c2381f3 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -517,6 +517,25 @@ int dl_runtime_exceeded(struct rq *rq, struct sched_dl_entity *dl_se)
 		return 0;
 
 	/*
+	 * Record statistics about last and maximum deadline
+	 * misses and runtime overruns.
+	 */
+	if (dmiss) {
+		u64 damount = rq->clock - dl_se->deadline;
+
+		schedstat_set(dl_se->stats.last_dmiss, damount);
+		schedstat_set(dl_se->stats.dmiss_max,
+			      max(dl_se->stats.dmiss_max, damount));
+	}
+	if (rorun) {
+		u64 ramount = -dl_se->runtime;
+
+		schedstat_set(dl_se->stats.last_rorun, ramount);
+		schedstat_set(dl_se->stats.rorun_max,
+			      max(dl_se->stats.rorun_max, ramount));
+	}
+
+	/*
 	 * If we are beyond our current deadline and we are still
 	 * executing, then we have already used some of the runtime of
 	 * the next instance. Thus, if we do not account that, we are
@@ -556,6 +575,7 @@ static void update_curr_dl(struct rq *rq)
 		      max(curr->se.statistics.exec_max, delta_exec));
 
 	curr->se.sum_exec_runtime += delta_exec;
+	schedstat_add(&rq->dl, exec_clock, delta_exec);
 	account_group_exec_runtime(curr, delta_exec);
 
 	curr->se.exec_start = rq->clock_task;
@@ -907,6 +927,18 @@ static void start_hrtick_dl(struct rq *rq, struct task_struct *p)
 }
 #endif
 
+#ifdef CONFIG_SCHED_DEBUG
+struct sched_dl_entity *__pick_dl_last_entity(struct dl_rq *dl_rq)
+{
+	struct rb_node *last = rb_last(&dl_rq->rb_root);
+
+	if (!last)
+		return NULL;
+
+	return rb_entry(last, struct sched_dl_entity, rb_node);
+}
+#endif /* CONFIG_SCHED_DEBUG */
+
 static struct sched_dl_entity *pick_next_dl_entity(struct rq *rq,
 						   struct dl_rq *dl_rq)
 {
@@ -1583,3 +1615,16 @@ const struct sched_class dl_sched_class = {
 	.switched_from		= switched_from_dl,
 	.switched_to		= switched_to_dl,
 };
+
+#ifdef CONFIG_SCHED_DEBUG
+extern void print_dl_rq(struct seq_file *m, int cpu, struct dl_rq *dl_rq);
+
+void print_dl_stats(struct seq_file *m, int cpu)
+{
+	struct dl_rq *dl_rq = &cpu_rq(cpu)->dl;
+
+	rcu_read_lock();
+	print_dl_rq(m, cpu, dl_rq);
+	rcu_read_unlock();
+}
+#endif /* CONFIG_SCHED_DEBUG */
diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index 1965599..811b025 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -253,6 +253,45 @@ void print_rt_rq(struct seq_file *m, int cpu, struct rt_rq *rt_rq)
 #undef P
 }
 
+extern struct sched_dl_entity *__pick_dl_last_entity(struct dl_rq *dl_rq);
+extern void print_dl_stats(struct seq_file *m, int cpu);
+
+void print_dl_rq(struct seq_file *m, int cpu, struct dl_rq *dl_rq)
+{
+	s64 min_deadline = -1, max_deadline = -1;
+	struct rq *rq = cpu_rq(cpu);
+	struct sched_dl_entity *last;
+	unsigned long flags;
+
+	SEQ_printf(m, "\ndl_rq[%d]:\n", cpu);
+
+	raw_spin_lock_irqsave(&rq->lock, flags);
+	if (dl_rq->rb_leftmost)
+		min_deadline = (rb_entry(dl_rq->rb_leftmost,
+					 struct sched_dl_entity,
+					 rb_node))->deadline;
+	last = __pick_dl_last_entity(dl_rq);
+	if (last)
+		max_deadline = last->deadline;
+	raw_spin_unlock_irqrestore(&rq->lock, flags);
+
+#define P(x) \
+	SEQ_printf(m, "  .%-30s: %Ld\n", #x, (long long)(dl_rq->x))
+#define __PN(x) \
+	SEQ_printf(m, "  .%-30s: %Ld.%06ld\n", #x, SPLIT_NS(x))
+#define PN(x) \
+	SEQ_printf(m, "  .%-30s: %Ld.%06ld\n", #x, SPLIT_NS(dl_rq->x))
+
+	P(dl_nr_running);
+	PN(exec_clock);
+	__PN(min_deadline);
+	__PN(max_deadline);
+
+#undef PN
+#undef __PN
+#undef P
+}
+
 extern __read_mostly int sched_clock_running;
 
 static void print_cpu(struct seq_file *m, int cpu)
@@ -320,6 +359,7 @@ do {									\
 	spin_lock_irqsave(&sched_debug_lock, flags);
 	print_cfs_stats(m, cpu);
 	print_rt_stats(m, cpu);
+	print_dl_stats(m, cpu);
 
 	rcu_read_lock();
 	print_rq(m, rq, cpu);
@@ -540,6 +580,12 @@ void proc_sched_show_task(struct task_struct *p, struct seq_file *m)
 	P(se.statistics.nr_wakeups_affine_attempts);
 	P(se.statistics.nr_wakeups_passive);
 	P(se.statistics.nr_wakeups_idle);
+	if (dl_task(p)) {
+		PN(dl.stats.last_dmiss);
+		PN(dl.stats.dmiss_max);
+		PN(dl.stats.last_rorun);
+		PN(dl.stats.rorun_max);
+	}
 
 	{
 		u64 avg_atom, avg_per_cpu;
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 70d0030..b04aeed 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -384,6 +384,8 @@ struct dl_rq {
 
 	unsigned long dl_nr_running;
 
+	u64 exec_clock;
+
 #ifdef CONFIG_SMP
 	/*
 	 * Deadline values of the currently executing and the
@@ -410,6 +412,11 @@ struct dl_rq {
 #endif
 };
 
+#ifdef CONFIG_SCHED_DEBUG
+struct sched_dl_entity *__pick_dl_last_entity(struct dl_rq *dl_rq);
+void print_dl_stats(struct seq_file *m, int cpu);
+#endif
+
 #ifdef CONFIG_SMP
 
 /*
@@ -1366,7 +1373,7 @@ extern void print_rt_stats(struct seq_file *m, int cpu);
 
 extern void init_cfs_rq(struct cfs_rq *cfs_rq);
 extern void init_rt_rq(struct rt_rq *rt_rq, struct rq *rq);
-extern void init_dl_rq(struct dl_rq *rt_rq, struct rq *rq);
+extern void init_dl_rq(struct dl_rq *dl_rq, struct rq *rq);
 
 extern void account_cfs_bandwidth_used(int enabled, int was_enabled);
 
-- 
1.7.9.5

[PATCH 08/14] sched: add latency tracing for -deadline tasks.

[Juri Lelli]

From: Dario Faggioli <raistlin@linux.it>

It is very likely that systems that wants/needs to use the new
SCHED_DEADLINE policy also want to have the scheduling latency of
the -deadline tasks under control.

For this reason a new version of the scheduling wakeup latency,
called "wakeup_dl", is introduced.

As a consequence of applying this patch there will be three wakeup
latency tracer:
 * "wakeup", that deals with all tasks in the system;
 * "wakeup_rt", that deals with -rt and -deadline tasks only;
 * "wakeup_dl", that deals with -deadline tasks only.

Signed-off-by: Dario Faggioli <raistlin@linux.it>
Signed-off-by: Juri Lelli <juri.lelli@gmail.com>
---
 kernel/trace/trace_sched_wakeup.c |   44 +++++++++++++++++++++++++++++++++----
 kernel/trace/trace_selftest.c     |   28 +++++++++++++----------
 2 files changed, 57 insertions(+), 15 deletions(-)

diff --git a/kernel/trace/trace_sched_wakeup.c b/kernel/trace/trace_sched_wakeup.c
index fee77e1..1457fb1 100644
--- a/kernel/trace/trace_sched_wakeup.c
+++ b/kernel/trace/trace_sched_wakeup.c
@@ -27,6 +27,7 @@ static int			wakeup_cpu;
 static int			wakeup_current_cpu;
 static unsigned			wakeup_prio = -1;
 static int			wakeup_rt;
+static int			wakeup_dl;
 
 static arch_spinlock_t wakeup_lock =
 	(arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
@@ -472,9 +473,17 @@ probe_wakeup(void *ignore, struct task_struct *p, int success)
 	tracing_record_cmdline(p);
 	tracing_record_cmdline(current);
 
-	if ((wakeup_rt && !rt_task(p)) ||
-			p->prio >= wakeup_prio ||
-			p->prio >= current->prio)
+	/*
+	 * Semantic is like this:
+	 *  - wakeup tracer handles all tasks in the system, independently
+	 *    from their scheduling class;
+	 *  - wakeup_rt tracer handles tasks belonging to sched_dl and
+	 *    sched_rt class;
+	 *  - wakeup_dl handles tasks belonging to sched_dl class only.
+	 */
+	if ((wakeup_dl && !dl_task(p)) ||
+	    (wakeup_rt && !dl_task(p) && !rt_task(p)) ||
+	    (p->prio >= wakeup_prio || p->prio >= current->prio))
 		return;
 
 	pc = preempt_count();
@@ -486,7 +495,7 @@ probe_wakeup(void *ignore, struct task_struct *p, int success)
 	arch_spin_lock(&wakeup_lock);
 
 	/* check for races. */
-	if (!tracer_enabled || p->prio >= wakeup_prio)
+	if (!tracer_enabled || (!dl_task(p) && p->prio >= wakeup_prio))
 		goto out_locked;
 
 	/* reset the trace */
@@ -597,16 +606,25 @@ static int __wakeup_tracer_init(struct trace_array *tr)
 
 static int wakeup_tracer_init(struct trace_array *tr)
 {
+	wakeup_dl = 0;
 	wakeup_rt = 0;
 	return __wakeup_tracer_init(tr);
 }
 
 static int wakeup_rt_tracer_init(struct trace_array *tr)
 {
+	wakeup_dl = 0;
 	wakeup_rt = 1;
 	return __wakeup_tracer_init(tr);
 }
 
+static int wakeup_dl_tracer_init(struct trace_array *tr)
+{
+	wakeup_dl = 1;
+	wakeup_rt = 0;
+	return __wakeup_tracer_init(tr);
+}
+
 static void wakeup_tracer_reset(struct trace_array *tr)
 {
 	int lat_flag = save_flags & TRACE_ITER_LATENCY_FMT;
@@ -674,6 +692,20 @@ static struct tracer wakeup_rt_tracer __read_mostly =
 	.use_max_tr	= true,
 };
 
+static struct tracer wakeup_dl_tracer __read_mostly =
+{
+	.name		= "wakeup_dl",
+	.init		= wakeup_dl_tracer_init,
+	.reset		= wakeup_tracer_reset,
+	.start		= wakeup_tracer_start,
+	.stop		= wakeup_tracer_stop,
+	.wait_pipe	= poll_wait_pipe,
+	.print_max	= 1,
+#ifdef CONFIG_FTRACE_SELFTEST
+	.selftest    = trace_selftest_startup_wakeup,
+#endif
+};
+
 __init static int init_wakeup_tracer(void)
 {
 	int ret;
@@ -686,6 +718,10 @@ __init static int init_wakeup_tracer(void)
 	if (ret)
 		return ret;
 
+	ret = register_tracer(&wakeup_dl_tracer);
+	if (ret)
+		return ret;
+
 	return 0;
 }
 core_initcall(init_wakeup_tracer);
diff --git a/kernel/trace/trace_selftest.c b/kernel/trace/trace_selftest.c
index a7329b7..f76f8d6 100644
--- a/kernel/trace/trace_selftest.c
+++ b/kernel/trace/trace_selftest.c
@@ -1022,11 +1022,17 @@ trace_selftest_startup_nop(struct tracer *trace, struct trace_array *tr)
 #ifdef CONFIG_SCHED_TRACER
 static int trace_wakeup_test_thread(void *data)
 {
-	/* Make this a RT thread, doesn't need to be too high */
-	static const struct sched_param param = { .sched_priority = 5 };
+	/* Make this a -deadline thread */
+	struct sched_param2 paramx = {
+		.sched_priority = 0,
+		.sched_runtime = 100000ULL,
+		.sched_deadline = 10000000ULL,
+		.sched_period = 10000000ULL
+		.sched_flags = 0
+	};
 	struct completion *x = data;
 
-	sched_setscheduler(current, SCHED_FIFO, &param);
+	sched_setscheduler2(current, SCHED_DEADLINE, &paramx);
 
 	/* Make it know we have a new prio */
 	complete(x);
@@ -1040,8 +1046,8 @@ static int trace_wakeup_test_thread(void *data)
 	/* we are awake, now wait to disappear */
 	while (!kthread_should_stop()) {
 		/*
-		 * This is an RT task, do short sleeps to let
-		 * others run.
+		 * This will likely be the system top priority
+		 * task, do short sleeps to let others run.
 		 */
 		msleep(100);
 	}
@@ -1054,21 +1060,21 @@ trace_selftest_startup_wakeup(struct tracer *trace, struct trace_array *tr)
 {
 	unsigned long save_max = tracing_max_latency;
 	struct task_struct *p;
-	struct completion isrt;
+	struct completion is_ready;
 	unsigned long count;
 	int ret;
 
-	init_completion(&isrt);
+	init_completion(&is_ready);
 
-	/* create a high prio thread */
-	p = kthread_run(trace_wakeup_test_thread, &isrt, "ftrace-test");
+	/* create a -deadline thread */
+	p = kthread_run(trace_wakeup_test_thread, &is_ready, "ftrace-test");
 	if (IS_ERR(p)) {
 		printk(KERN_CONT "Failed to create ftrace wakeup test thread ");
 		return -1;
 	}
 
-	/* make sure the thread is running at an RT prio */
-	wait_for_completion(&isrt);
+	/* make sure the thread is running at -deadline policy */
+	wait_for_completion(&is_ready);
 
 	/* start the tracing */
 	ret = tracer_init(trace, tr);
-- 
1.7.9.5

[PATCH 09/14] rtmutex: turn the plist into an rb-tree.

[Juri Lelli]

From: Peter Zijlstra <peterz@infradead.org>

Turn the pi-chains from plist to rb-tree, in the rt_mutex code,
and provide a proper comparison function for -deadline and
-priority tasks.

This is done mainly because:
 - classical prio field of the plist is just an int, which might
   not be enough for representing a deadline;
 - manipulating such a list would become O(nr_deadline_tasks),
   which might be to much, as the number of -deadline task increases.

Therefore, an rb-tree is used, and tasks are queued in it according
to the following logic:
 - among two -priority (i.e., SCHED_BATCH/OTHER/RR/FIFO) tasks, the
   one with the higher (lower, actually!) prio wins;
 - among a -priority and a -deadline task, the latter always wins;
 - among two -deadline tasks, the one with the earliest deadline
   wins.

Queueing and dequeueing functions are changed accordingly, for both
the list of a task's pi-waiters and the list of tasks blocked on
a pi-lock.

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Dario Faggioli <raistlin@linux.it>
Signed-off-by: Juri Lelli <juri.lelli@gmail.com>
---
 include/linux/init_task.h |   10 +++
 include/linux/rtmutex.h   |   18 ++----
 include/linux/sched.h     |    4 +-
 kernel/fork.c             |    3 +-
 kernel/futex.c            |    2 +
 kernel/rtmutex-debug.c    |    8 +--
 kernel/rtmutex.c          |  152 ++++++++++++++++++++++++++++++++++++---------
 kernel/rtmutex_common.h   |   22 +++----
 kernel/sched/core.c       |    4 --
 9 files changed, 157 insertions(+), 66 deletions(-)

diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index 5cd0f09..69b97ea 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -11,6 +11,7 @@
 #include <linux/user_namespace.h>
 #include <linux/securebits.h>
 #include <linux/seqlock.h>
+#include <linux/rbtree.h>
 #include <net/net_namespace.h>
 #include <linux/sched/rt.h>
 
@@ -154,6 +155,14 @@ extern struct task_group root_task_group;
 
 #define INIT_TASK_COMM "swapper"
 
+#ifdef CONFIG_RT_MUTEXES
+# define INIT_RT_MUTEXES(tsk)						\
+	.pi_waiters = RB_ROOT,						\
+	.pi_waiters_leftmost = NULL,
+#else
+# define INIT_RT_MUTEXES(tsk)
+#endif
+
 /*
  *  INIT_TASK is used to set up the first task table, touch at
  * your own risk!. Base=0, limit=0x1fffff (=2MB)
@@ -221,6 +230,7 @@ extern struct task_group root_task_group;
 	INIT_TRACE_RECURSION						\
 	INIT_TASK_RCU_PREEMPT(tsk)					\
 	INIT_CPUSET_SEQ							\
+	INIT_RT_MUTEXES(tsk)						\
 	INIT_VTIME(tsk)							\
 }
 
diff --git a/include/linux/rtmutex.h b/include/linux/rtmutex.h
index de17134..3aed8d7 100644
--- a/include/linux/rtmutex.h
+++ b/include/linux/rtmutex.h
@@ -13,7 +13,7 @@
 #define __LINUX_RT_MUTEX_H
 
 #include <linux/linkage.h>
-#include <linux/plist.h>
+#include <linux/rbtree.h>
 #include <linux/spinlock_types.h>
 
 extern int max_lock_depth; /* for sysctl */
@@ -22,12 +22,14 @@ extern int max_lock_depth; /* for sysctl */
  * The rt_mutex structure
  *
  * @wait_lock:	spinlock to protect the structure
- * @wait_list:	pilist head to enqueue waiters in priority order
+ * @waiters:	rbtree root to enqueue waiters in priority order
+ * @waiters_leftmost: top waiter
  * @owner:	the mutex owner
  */
 struct rt_mutex {
 	raw_spinlock_t		wait_lock;
-	struct plist_head	wait_list;
+	struct rb_root          waiters;
+	struct rb_node          *waiters_leftmost;
 	struct task_struct	*owner;
 #ifdef CONFIG_DEBUG_RT_MUTEXES
 	int			save_state;
@@ -66,7 +68,7 @@ struct hrtimer_sleeper;
 
 #define __RT_MUTEX_INITIALIZER(mutexname) \
 	{ .wait_lock = __RAW_SPIN_LOCK_UNLOCKED(mutexname.wait_lock) \
-	, .wait_list = PLIST_HEAD_INIT(mutexname.wait_list) \
+	, .waiters = RB_ROOT \
 	, .owner = NULL \
 	__DEBUG_RT_MUTEX_INITIALIZER(mutexname)}
 
@@ -98,12 +100,4 @@ extern int rt_mutex_trylock(struct rt_mutex *lock);
 
 extern void rt_mutex_unlock(struct rt_mutex *lock);
 
-#ifdef CONFIG_RT_MUTEXES
-# define INIT_RT_MUTEXES(tsk)						\
-	.pi_waiters	= PLIST_HEAD_INIT(tsk.pi_waiters),	\
-	INIT_RT_MUTEX_DEBUG(tsk)
-#else
-# define INIT_RT_MUTEXES(tsk)
-#endif
-
 #endif
diff --git a/include/linux/sched.h b/include/linux/sched.h
index c8bfabc..2fbb50a 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -16,6 +16,7 @@ struct sched_param {
 #include <linux/types.h>
 #include <linux/timex.h>
 #include <linux/jiffies.h>
+#include <linux/plist.h>
 #include <linux/rbtree.h>
 #include <linux/thread_info.h>
 #include <linux/cpumask.h>
@@ -1340,7 +1341,8 @@ struct task_struct {
 
 #ifdef CONFIG_RT_MUTEXES
 	/* PI waiters blocked on a rt_mutex held by this task */
-	struct plist_head pi_waiters;
+	struct rb_root pi_waiters;
+	struct rb_node *pi_waiters_leftmost;
 	/* Deadlock detection and priority inheritance handling */
 	struct rt_mutex_waiter *pi_blocked_on;
 #endif
diff --git a/kernel/fork.c b/kernel/fork.c
index 55fc95f..aa6e18d 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1089,7 +1089,8 @@ static void rt_mutex_init_task(struct task_struct *p)
 {
 	raw_spin_lock_init(&p->pi_lock);
 #ifdef CONFIG_RT_MUTEXES
-	plist_head_init(&p->pi_waiters);
+	p->pi_waiters = RB_ROOT;
+	p->pi_waiters_leftmost = NULL;
 	p->pi_blocked_on = NULL;
 #endif
 }
diff --git a/kernel/futex.c b/kernel/futex.c
index c3a1a55..ff7141e 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -2315,6 +2315,8 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags,
 	 * code while we sleep on uaddr.
 	 */
 	debug_rt_mutex_init_waiter(&rt_waiter);
+	RB_CLEAR_NODE(&rt_waiter.pi_tree_entry);
+	RB_CLEAR_NODE(&rt_waiter.tree_entry);
 	rt_waiter.task = NULL;
 
 	ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2, VERIFY_WRITE);
diff --git a/kernel/rtmutex-debug.c b/kernel/rtmutex-debug.c
index 13b243a..49b2ed3 100644
--- a/kernel/rtmutex-debug.c
+++ b/kernel/rtmutex-debug.c
@@ -24,7 +24,7 @@
 #include <linux/kallsyms.h>
 #include <linux/syscalls.h>
 #include <linux/interrupt.h>
-#include <linux/plist.h>
+#include <linux/rbtree.h>
 #include <linux/fs.h>
 #include <linux/debug_locks.h>
 
@@ -57,7 +57,7 @@ static void printk_lock(struct rt_mutex *lock, int print_owner)
 
 void rt_mutex_debug_task_free(struct task_struct *task)
 {
-	DEBUG_LOCKS_WARN_ON(!plist_head_empty(&task->pi_waiters));
+	DEBUG_LOCKS_WARN_ON(!RB_EMPTY_ROOT(&task->pi_waiters));
 	DEBUG_LOCKS_WARN_ON(task->pi_blocked_on);
 }
 
@@ -154,16 +154,12 @@ void debug_rt_mutex_proxy_unlock(struct rt_mutex *lock)
 void debug_rt_mutex_init_waiter(struct rt_mutex_waiter *waiter)
 {
 	memset(waiter, 0x11, sizeof(*waiter));
-	plist_node_init(&waiter->list_entry, MAX_PRIO);
-	plist_node_init(&waiter->pi_list_entry, MAX_PRIO);
 	waiter->deadlock_task_pid = NULL;
 }
 
 void debug_rt_mutex_free_waiter(struct rt_mutex_waiter *waiter)
 {
 	put_pid(waiter->deadlock_task_pid);
-	DEBUG_LOCKS_WARN_ON(!plist_node_empty(&waiter->list_entry));
-	DEBUG_LOCKS_WARN_ON(!plist_node_empty(&waiter->pi_list_entry));
 	memset(waiter, 0x22, sizeof(*waiter));
 }
 
diff --git a/kernel/rtmutex.c b/kernel/rtmutex.c
index 0dd6aec..4ea7eaa 100644
--- a/kernel/rtmutex.c
+++ b/kernel/rtmutex.c
@@ -91,10 +91,104 @@ static inline void mark_rt_mutex_waiters(struct rt_mutex *lock)
 }
 #endif
 
+static inline int
+rt_mutex_waiter_less(struct rt_mutex_waiter *left,
+		     struct rt_mutex_waiter *right)
+{
+	if (left->task->prio < right->task->prio)
+		return 1;
+
+	/*
+	 * If both tasks are dl_task(), we check their deadlines.
+	 */
+	if (dl_prio(left->task->prio) && dl_prio(right->task->prio))
+		return (left->task->dl.deadline < right->task->dl.deadline);
+
+	return 0;
+}
+
+static void
+rt_mutex_enqueue(struct rt_mutex *lock, struct rt_mutex_waiter *waiter)
+{
+	struct rb_node **link = &lock->waiters.rb_node;
+	struct rb_node *parent = NULL;
+	struct rt_mutex_waiter *entry;
+	int leftmost = 1;
+
+	while (*link) {
+		parent = *link;
+		entry = rb_entry(parent, struct rt_mutex_waiter, tree_entry);
+		if (rt_mutex_waiter_less(waiter, entry)) {
+			link = &parent->rb_left;
+		} else {
+			link = &parent->rb_right;
+			leftmost = 0;
+		}
+	}
+
+	if (leftmost)
+		lock->waiters_leftmost = &waiter->tree_entry;
+
+	rb_link_node(&waiter->tree_entry, parent, link);
+	rb_insert_color(&waiter->tree_entry, &lock->waiters);
+}
+
+static void
+rt_mutex_dequeue(struct rt_mutex *lock, struct rt_mutex_waiter *waiter)
+{
+	if (RB_EMPTY_NODE(&waiter->tree_entry))
+		return;
+
+	if (lock->waiters_leftmost == &waiter->tree_entry)
+		lock->waiters_leftmost = rb_next(&waiter->tree_entry);
+
+	rb_erase(&waiter->tree_entry, &lock->waiters);
+	RB_CLEAR_NODE(&waiter->tree_entry);
+}
+
+static void
+rt_mutex_enqueue_pi(struct task_struct *task, struct rt_mutex_waiter *waiter)
+{
+	struct rb_node **link = &task->pi_waiters.rb_node;
+	struct rb_node *parent = NULL;
+	struct rt_mutex_waiter *entry;
+	int leftmost = 1;
+
+	while (*link) {
+		parent = *link;
+		entry = rb_entry(parent, struct rt_mutex_waiter, pi_tree_entry);
+		if (rt_mutex_waiter_less(waiter, entry)) {
+			link = &parent->rb_left;
+		} else {
+			link = &parent->rb_right;
+			leftmost = 0;
+		}
+	}
+
+	if (leftmost)
+		task->pi_waiters_leftmost = &waiter->pi_tree_entry;
+
+	rb_link_node(&waiter->pi_tree_entry, parent, link);
+	rb_insert_color(&waiter->pi_tree_entry, &task->pi_waiters);
+}
+
+static void
+rt_mutex_dequeue_pi(struct task_struct *task, struct rt_mutex_waiter *waiter)
+{
+	if (RB_EMPTY_NODE(&waiter->pi_tree_entry))
+		return;
+
+	if (task->pi_waiters_leftmost == &waiter->pi_tree_entry)
+		task->pi_waiters_leftmost = rb_next(&waiter->pi_tree_entry);
+
+	rb_erase(&waiter->pi_tree_entry, &task->pi_waiters);
+	RB_CLEAR_NODE(&waiter->pi_tree_entry);
+}
+
 /*
- * Calculate task priority from the waiter list priority
+ * Calculate task priority from the waiter tree priority
  *
- * Return task->normal_prio when the waiter list is empty or when
+ * Return task->normal_prio when the waiter tree is empty or when
  * the waiter is not allowed to do priority boosting
  */
 int rt_mutex_getprio(struct task_struct *task)
@@ -102,7 +196,7 @@ int rt_mutex_getprio(struct task_struct *task)
 	if (likely(!task_has_pi_waiters(task)))
 		return task->normal_prio;
 
-	return min(task_top_pi_waiter(task)->pi_list_entry.prio,
+	return min(task_top_pi_waiter(task)->task->prio,
 		   task->normal_prio);
 }
 
@@ -233,7 +327,7 @@ static int rt_mutex_adjust_prio_chain(struct task_struct *task,
 	 * When deadlock detection is off then we check, if further
 	 * priority adjustment is necessary.
 	 */
-	if (!detect_deadlock && waiter->list_entry.prio == task->prio)
+	if (!detect_deadlock && waiter->task->prio == task->prio)
 		goto out_unlock_pi;
 
 	lock = waiter->lock;
@@ -254,9 +348,9 @@ static int rt_mutex_adjust_prio_chain(struct task_struct *task,
 	top_waiter = rt_mutex_top_waiter(lock);
 
 	/* Requeue the waiter */
-	plist_del(&waiter->list_entry, &lock->wait_list);
-	waiter->list_entry.prio = task->prio;
-	plist_add(&waiter->list_entry, &lock->wait_list);
+	rt_mutex_dequeue(lock, waiter);
+	waiter->task->prio = task->prio;
+	rt_mutex_enqueue(lock, waiter);
 
 	/* Release the task */
 	raw_spin_unlock_irqrestore(&task->pi_lock, flags);
@@ -280,17 +374,15 @@ static int rt_mutex_adjust_prio_chain(struct task_struct *task,
 
 	if (waiter == rt_mutex_top_waiter(lock)) {
 		/* Boost the owner */
-		plist_del(&top_waiter->pi_list_entry, &task->pi_waiters);
-		waiter->pi_list_entry.prio = waiter->list_entry.prio;
-		plist_add(&waiter->pi_list_entry, &task->pi_waiters);
+		rt_mutex_dequeue_pi(task, top_waiter);
+		rt_mutex_enqueue_pi(task, waiter);
 		__rt_mutex_adjust_prio(task);
 
 	} else if (top_waiter == waiter) {
 		/* Deboost the owner */
-		plist_del(&waiter->pi_list_entry, &task->pi_waiters);
+		rt_mutex_dequeue_pi(task, waiter);
 		waiter = rt_mutex_top_waiter(lock);
-		waiter->pi_list_entry.prio = waiter->list_entry.prio;
-		plist_add(&waiter->pi_list_entry, &task->pi_waiters);
+		rt_mutex_enqueue_pi(task, waiter);
 		__rt_mutex_adjust_prio(task);
 	}
 
@@ -355,7 +447,7 @@ static int try_to_take_rt_mutex(struct rt_mutex *lock, struct task_struct *task,
 	 * 3) it is top waiter
 	 */
 	if (rt_mutex_has_waiters(lock)) {
-		if (task->prio >= rt_mutex_top_waiter(lock)->list_entry.prio) {
+		if (task->prio >= rt_mutex_top_waiter(lock)->task->prio) {
 			if (!waiter || waiter != rt_mutex_top_waiter(lock))
 				return 0;
 		}
@@ -369,7 +461,7 @@ static int try_to_take_rt_mutex(struct rt_mutex *lock, struct task_struct *task,
 
 		/* remove the queued waiter. */
 		if (waiter) {
-			plist_del(&waiter->list_entry, &lock->wait_list);
+			rt_mutex_dequeue(lock, waiter);
 			task->pi_blocked_on = NULL;
 		}
 
@@ -379,8 +471,7 @@ static int try_to_take_rt_mutex(struct rt_mutex *lock, struct task_struct *task,
 		 */
 		if (rt_mutex_has_waiters(lock)) {
 			top = rt_mutex_top_waiter(lock);
-			top->pi_list_entry.prio = top->list_entry.prio;
-			plist_add(&top->pi_list_entry, &task->pi_waiters);
+			rt_mutex_enqueue_pi(task, top);
 		}
 		raw_spin_unlock_irqrestore(&task->pi_lock, flags);
 	}
@@ -416,13 +507,11 @@ static int task_blocks_on_rt_mutex(struct rt_mutex *lock,
 	__rt_mutex_adjust_prio(task);
 	waiter->task = task;
 	waiter->lock = lock;
-	plist_node_init(&waiter->list_entry, task->prio);
-	plist_node_init(&waiter->pi_list_entry, task->prio);
-
+	
 	/* Get the top priority waiter on the lock */
 	if (rt_mutex_has_waiters(lock))
 		top_waiter = rt_mutex_top_waiter(lock);
-	plist_add(&waiter->list_entry, &lock->wait_list);
+	rt_mutex_enqueue(lock, waiter);
 
 	task->pi_blocked_on = waiter;
 
@@ -433,8 +522,8 @@ static int task_blocks_on_rt_mutex(struct rt_mutex *lock,
 
 	if (waiter == rt_mutex_top_waiter(lock)) {
 		raw_spin_lock_irqsave(&owner->pi_lock, flags);
-		plist_del(&top_waiter->pi_list_entry, &owner->pi_waiters);
-		plist_add(&waiter->pi_list_entry, &owner->pi_waiters);
+		rt_mutex_dequeue_pi(owner, top_waiter);
+		rt_mutex_enqueue_pi(owner, waiter);
 
 		__rt_mutex_adjust_prio(owner);
 		if (owner->pi_blocked_on)
@@ -486,7 +575,7 @@ static void wakeup_next_waiter(struct rt_mutex *lock)
 	 * boosted mode and go back to normal after releasing
 	 * lock->wait_lock.
 	 */
-	plist_del(&waiter->pi_list_entry, &current->pi_waiters);
+	rt_mutex_dequeue_pi(current, waiter);
 
 	rt_mutex_set_owner(lock, NULL);
 
@@ -510,7 +599,7 @@ static void remove_waiter(struct rt_mutex *lock,
 	int chain_walk = 0;
 
 	raw_spin_lock_irqsave(&current->pi_lock, flags);
-	plist_del(&waiter->list_entry, &lock->wait_list);
+	rt_mutex_dequeue(lock, waiter);
 	current->pi_blocked_on = NULL;
 	raw_spin_unlock_irqrestore(&current->pi_lock, flags);
 
@@ -521,13 +610,13 @@ static void remove_waiter(struct rt_mutex *lock,
 
 		raw_spin_lock_irqsave(&owner->pi_lock, flags);
 
-		plist_del(&waiter->pi_list_entry, &owner->pi_waiters);
+		rt_mutex_dequeue_pi(owner, waiter);
 
 		if (rt_mutex_has_waiters(lock)) {
 			struct rt_mutex_waiter *next;
 
 			next = rt_mutex_top_waiter(lock);
-			plist_add(&next->pi_list_entry, &owner->pi_waiters);
+			rt_mutex_enqueue_pi(owner, next);
 		}
 		__rt_mutex_adjust_prio(owner);
 
@@ -537,8 +626,6 @@ static void remove_waiter(struct rt_mutex *lock,
 		raw_spin_unlock_irqrestore(&owner->pi_lock, flags);
 	}
 
-	WARN_ON(!plist_node_empty(&waiter->pi_list_entry));
-
 	if (!chain_walk)
 		return;
 
@@ -565,7 +652,7 @@ void rt_mutex_adjust_pi(struct task_struct *task)
 	raw_spin_lock_irqsave(&task->pi_lock, flags);
 
 	waiter = task->pi_blocked_on;
-	if (!waiter || waiter->list_entry.prio == task->prio) {
+	if (!waiter || waiter->task->prio == task->prio) {
 		raw_spin_unlock_irqrestore(&task->pi_lock, flags);
 		return;
 	}
@@ -638,6 +725,8 @@ rt_mutex_slowlock(struct rt_mutex *lock, int state,
 	int ret = 0;
 
 	debug_rt_mutex_init_waiter(&waiter);
+	RB_CLEAR_NODE(&waiter.pi_tree_entry);
+	RB_CLEAR_NODE(&waiter.tree_entry);
 
 	raw_spin_lock(&lock->wait_lock);
 
@@ -904,7 +993,8 @@ void __rt_mutex_init(struct rt_mutex *lock, const char *name)
 {
 	lock->owner = NULL;
 	raw_spin_lock_init(&lock->wait_lock);
-	plist_head_init(&lock->wait_list);
+	lock->waiters = RB_ROOT;
+	lock->waiters_leftmost = NULL;
 
 	debug_rt_mutex_init(lock, name);
 }
diff --git a/kernel/rtmutex_common.h b/kernel/rtmutex_common.h
index 53a66c8..b65442f 100644
--- a/kernel/rtmutex_common.h
+++ b/kernel/rtmutex_common.h
@@ -40,13 +40,13 @@ extern void schedule_rt_mutex_test(struct rt_mutex *lock);
  * This is the control structure for tasks blocked on a rt_mutex,
  * which is allocated on the kernel stack on of the blocked task.
  *
- * @list_entry:		pi node to enqueue into the mutex waiters list
- * @pi_list_entry:	pi node to enqueue into the mutex owner waiters list
+ * @tree_entry:		pi node to enqueue into the mutex waiters tree
+ * @pi_tree_entry:	pi node to enqueue into the mutex owner waiters tree
  * @task:		task reference to the blocked task
  */
 struct rt_mutex_waiter {
-	struct plist_node	list_entry;
-	struct plist_node	pi_list_entry;
+	struct rb_node          tree_entry;
+	struct rb_node          pi_tree_entry;
 	struct task_struct	*task;
 	struct rt_mutex		*lock;
 #ifdef CONFIG_DEBUG_RT_MUTEXES
@@ -57,11 +57,11 @@ struct rt_mutex_waiter {
 };
 
 /*
- * Various helpers to access the waiters-plist:
+ * Various helpers to access the waiters-tree:
  */
 static inline int rt_mutex_has_waiters(struct rt_mutex *lock)
 {
-	return !plist_head_empty(&lock->wait_list);
+	return !RB_EMPTY_ROOT(&lock->waiters);
 }
 
 static inline struct rt_mutex_waiter *
@@ -69,8 +69,8 @@ rt_mutex_top_waiter(struct rt_mutex *lock)
 {
 	struct rt_mutex_waiter *w;
 
-	w = plist_first_entry(&lock->wait_list, struct rt_mutex_waiter,
-			       list_entry);
+	w = rb_entry(lock->waiters_leftmost, struct rt_mutex_waiter,
+		     tree_entry);
 	BUG_ON(w->lock != lock);
 
 	return w;
@@ -78,14 +78,14 @@ rt_mutex_top_waiter(struct rt_mutex *lock)
 
 static inline int task_has_pi_waiters(struct task_struct *p)
 {
-	return !plist_head_empty(&p->pi_waiters);
+	return !RB_EMPTY_ROOT(&p->pi_waiters);
 }
 
 static inline struct rt_mutex_waiter *
 task_top_pi_waiter(struct task_struct *p)
 {
-	return plist_first_entry(&p->pi_waiters, struct rt_mutex_waiter,
-				  pi_list_entry);
+	return rb_entry(p->pi_waiters_leftmost, struct rt_mutex_waiter,
+			pi_tree_entry);
 }
 
 /*
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 2ec8a93..3925282 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6729,10 +6729,6 @@ void __init sched_init(void)
 	INIT_HLIST_HEAD(&init_task.preempt_notifiers);
 #endif
 
-#ifdef CONFIG_RT_MUTEXES
-	plist_head_init(&init_task.pi_waiters);
-#endif
-
 	/*
 	 * The boot idle thread does lazy MMU switching as well:
 	 */
-- 
1.7.9.5

[PATCH 10/14] sched: drafted deadline inheritance logic.

[Juri Lelli]

From: Dario Faggioli <raistlin@linux.it>

Some method to deal with rt-mutexes and make sched_dl interact with
the current PI-coded is needed, raising all but trivial issues, that
needs (according to us) to be solved with some restructuring of
the pi-code (i.e., going toward a proxy execution-ish implementation).

This is under development, in the meanwhile, as a temporary solution,
what this commits does is:
 - ensure a pi-lock owner with waiters is never throttled down. Instead,
   when it runs out of runtime, it immediately gets replenished and it's
   deadline is postponed;
 - the scheduling parameters (relative deadline and default runtime)
   used for that replenishments --during the whole period it holds the
   pi-lock-- are the ones of the waiting task with earliest deadline.

Acting this way, we provide some kind of boosting to the lock-owner,
still by using the existing (actually, slightly modified by the previous
commit) pi-architecture.

We would stress the fact that this is only a surely needed, all but
clean solution to the problem. In the end it's only a way to re-start
discussion within the community. So, as always, comments, ideas, rants,
etc.. are welcome! :-)

Signed-off-by: Dario Faggioli <raistlin@linux.it>
Signed-off-by: Juri Lelli <juri.lelli@gmail.com>
---
 include/linux/sched.h    |    8 +++-
 include/linux/sched/rt.h |    1 +
 kernel/fork.c            |    1 +
 kernel/rtmutex.c         |   13 ++++++-
 kernel/sched/core.c      |   36 +++++++++++++++---
 kernel/sched/deadline.c  |   91 +++++++++++++++++++++++++++-------------------
 kernel/sched/sched.h     |   14 +++++++
 7 files changed, 117 insertions(+), 47 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 2fbb50a..17da410 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1099,8 +1099,12 @@ struct sched_dl_entity {
 	 * @dl_new tells if a new instance arrived. If so we must
 	 * start executing it with full runtime and reset its absolute
 	 * deadline;
+	 *
+	 * @dl_boosted tells if we are boosted due to DI. If so we are
+	 * outside bandwidth enforcement mechanism (but only until we
+	 * exit the critical section).
 	 */
-	int dl_throttled, dl_new;
+	int dl_throttled, dl_new, dl_boosted;
 
 	/*
 	 * Bandwidth enforcement timer. Each -deadline task has its
@@ -1345,6 +1349,8 @@ struct task_struct {
 	struct rb_node *pi_waiters_leftmost;
 	/* Deadlock detection and priority inheritance handling */
 	struct rt_mutex_waiter *pi_blocked_on;
+	/* Top pi_waiters task */
+	struct task_struct *pi_top_task;
 #endif
 
 #ifdef CONFIG_DEBUG_MUTEXES
diff --git a/include/linux/sched/rt.h b/include/linux/sched/rt.h
index a157797..1fa88a2c 100644
--- a/include/linux/sched/rt.h
+++ b/include/linux/sched/rt.h
@@ -35,6 +35,7 @@ static inline int rt_task(struct task_struct *p)
 #ifdef CONFIG_RT_MUTEXES
 extern int rt_mutex_getprio(struct task_struct *p);
 extern void rt_mutex_setprio(struct task_struct *p, int prio);
+extern struct task_struct *rt_mutex_get_top_task(struct task_struct *task);
 extern void rt_mutex_adjust_pi(struct task_struct *p);
 static inline bool tsk_is_pi_blocked(struct task_struct *tsk)
 {
diff --git a/kernel/fork.c b/kernel/fork.c
index aa6e18d..7247105 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1092,6 +1092,7 @@ static void rt_mutex_init_task(struct task_struct *p)
 	p->pi_waiters = RB_ROOT;
 	p->pi_waiters_leftmost = NULL;
 	p->pi_blocked_on = NULL;
+	p->pi_top_task = NULL;
 #endif
 }
 
diff --git a/kernel/rtmutex.c b/kernel/rtmutex.c
index 4ea7eaa..cb5f950 100644
--- a/kernel/rtmutex.c
+++ b/kernel/rtmutex.c
@@ -200,6 +200,14 @@ int rt_mutex_getprio(struct task_struct *task)
 		   task->normal_prio);
 }
 
+struct task_struct *rt_mutex_get_top_task(struct task_struct *task)
+{
+	if (likely(!task_has_pi_waiters(task)))
+		return NULL;
+
+	return task_top_pi_waiter(task)->task;
+}
+
 /*
  * Adjust the priority of a task, after its pi_waiters got modified.
  *
@@ -209,7 +217,7 @@ static void __rt_mutex_adjust_prio(struct task_struct *task)
 {
 	int prio = rt_mutex_getprio(task);
 
-	if (task->prio != prio)
+	if (task->prio != prio || dl_prio(prio))
 		rt_mutex_setprio(task, prio);
 }
 
@@ -652,7 +660,8 @@ void rt_mutex_adjust_pi(struct task_struct *task)
 	raw_spin_lock_irqsave(&task->pi_lock, flags);
 
 	waiter = task->pi_blocked_on;
-	if (!waiter || waiter->task->prio == task->prio) {
+	if (!waiter || (waiter->task->prio == task->prio &&
+			!dl_prio(task->prio))) {
 		raw_spin_unlock_irqrestore(&task->pi_lock, flags);
 		return;
 	}
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 3925282..f9e7906 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -951,7 +951,7 @@ static inline void check_class_changed(struct rq *rq, struct task_struct *p,
 		if (prev_class->switched_from)
 			prev_class->switched_from(rq, p);
 		p->sched_class->switched_to(rq, p);
-	} else if (oldprio != p->prio)
+	} else if (oldprio != p->prio || dl_task(p))
 		p->sched_class->prio_changed(rq, p, oldprio);
 }
 
@@ -3042,7 +3042,7 @@ EXPORT_SYMBOL(sleep_on_timeout);
  */
 void rt_mutex_setprio(struct task_struct *p, int prio)
 {
-	int oldprio, on_rq, running;
+	int oldprio, on_rq, running, enqueue_flag = 0;
 	struct rq *rq;
 	const struct sched_class *prev_class;
 
@@ -3069,6 +3069,7 @@ void rt_mutex_setprio(struct task_struct *p, int prio)
 	}
 
 	trace_sched_pi_setprio(p, prio);
+	p->pi_top_task = rt_mutex_get_top_task(p);
 	oldprio = p->prio;
 	prev_class = p->sched_class;
 	on_rq = p->on_rq;
@@ -3078,19 +3079,42 @@ void rt_mutex_setprio(struct task_struct *p, int prio)
 	if (running)
 		p->sched_class->put_prev_task(rq, p);
 
-	if (dl_prio(prio))
+	/*
+	 * Boosting condition are:
+	 * 1. -rt task is running and holds mutex A
+	 *      --> -dl task blocks on mutex A
+	 *
+	 * 2. -dl task is running and holds mutex A
+	 *      --> -dl task blocks on mutex A and could preempt the
+	 *          running task
+	 */
+	if (dl_prio(prio)) {
+		if (!dl_prio(p->normal_prio) || (p->pi_top_task &&
+			dl_entity_preempt(&p->pi_top_task->dl, &p->dl))) {
+			p->dl.dl_boosted = 1;
+			p->dl.dl_throttled = 0;
+			enqueue_flag = ENQUEUE_REPLENISH;
+		} else
+			p->dl.dl_boosted = 0;
 		p->sched_class = &dl_sched_class;
-	else if (rt_prio(prio))
+	} else if (rt_prio(prio)) {
+		if (dl_prio(oldprio))
+			p->dl.dl_boosted = 0;
+		if (oldprio < prio)
+			enqueue_flag = ENQUEUE_HEAD;
 		p->sched_class = &rt_sched_class;
-	else
+	} else {
+		if (dl_prio(oldprio))
+			p->dl.dl_boosted = 0;
 		p->sched_class = &fair_sched_class;
+	}
 
 	p->prio = prio;
 
 	if (running)
 		p->sched_class->set_curr_task(rq);
 	if (on_rq)
-		enqueue_task(rq, p, oldprio < prio ? ENQUEUE_HEAD : 0);
+		enqueue_task(rq, p, enqueue_flag);
 
 	check_class_changed(rq, p, prev_class, oldprio);
 out_unlock:
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index c2381f3..aded515 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -16,20 +16,6 @@
  */
 #include "sched.h"
 
-static inline int dl_time_before(u64 a, u64 b)
-{
-	return (s64)(a - b) < 0;
-}
-
-/*
- * Tells if entity @a should preempt entity @b.
- */
-static inline
-int dl_entity_preempt(struct sched_dl_entity *a, struct sched_dl_entity *b)
-{
-	return dl_time_before(a->deadline, b->deadline);
-}
-
 static inline struct task_struct *dl_task_of(struct sched_dl_entity *dl_se)
 {
 	return container_of(dl_se, struct task_struct, dl);
@@ -240,7 +226,8 @@ static void check_preempt_curr_dl(struct rq *rq, struct task_struct *p,
  * one, and to (try to!) reconcile itself with its own scheduling
  * parameters.
  */
-static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se)
+static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se,
+				       struct sched_dl_entity *pi_se)
 {
 	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
 	struct rq *rq = rq_of_dl_rq(dl_rq);
@@ -252,8 +239,8 @@ static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se)
 	 * future; in fact, we must consider execution overheads (time
 	 * spent on hardirq context, etc.).
 	 */
-	dl_se->deadline = rq->clock + dl_se->dl_deadline;
-	dl_se->runtime = dl_se->dl_runtime;
+	dl_se->deadline = rq->clock + pi_se->dl_deadline;
+	dl_se->runtime = pi_se->dl_runtime;
 	dl_se->dl_new = 0;
 }
 
@@ -275,11 +262,23 @@ static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se)
  * could happen are, typically, a entity voluntarily trying to overcome its
  * runtime, or it just underestimated it during sched_setscheduler_ex().
  */
-static void replenish_dl_entity(struct sched_dl_entity *dl_se)
+static void replenish_dl_entity(struct sched_dl_entity *dl_se,
+				struct sched_dl_entity *pi_se)
 {
 	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
 	struct rq *rq = rq_of_dl_rq(dl_rq);
 
+	BUG_ON(pi_se->dl_runtime <= 0);
+
+	/*
+	 * This could be the case for a !-dl task that is boosted.
+	 * Just go with full inherited parameters.
+	 */
+	if (dl_se->dl_deadline == 0) {
+		dl_se->deadline = rq->clock + pi_se->dl_deadline;
+		dl_se->runtime = pi_se->dl_runtime;
+	}
+
 	/*
 	 * We keep moving the deadline away until we get some
 	 * available runtime for the entity. This ensures correct
@@ -287,8 +286,8 @@ static void replenish_dl_entity(struct sched_dl_entity *dl_se)
 	 * arbitrary large.
 	 */
 	while (dl_se->runtime <= 0) {
-		dl_se->deadline += dl_se->dl_period;
-		dl_se->runtime += dl_se->dl_runtime;
+		dl_se->deadline += pi_se->dl_period;
+		dl_se->runtime += pi_se->dl_runtime;
 	}
 
 	/*
@@ -307,8 +306,8 @@ static void replenish_dl_entity(struct sched_dl_entity *dl_se)
 			lag_once = true;
 			printk_sched("sched: DL replenish lagged to much\n");
 		}
-		dl_se->deadline = rq->clock + dl_se->dl_deadline;
-		dl_se->runtime = dl_se->dl_runtime;
+		dl_se->deadline = rq->clock + pi_se->dl_deadline;
+		dl_se->runtime = pi_se->dl_runtime;
 	}
 }
 
@@ -335,7 +334,8 @@ static void replenish_dl_entity(struct sched_dl_entity *dl_se)
  * task with deadline equal to period this is the same of using
  * dl_deadline instead of dl_period in the equation above.
  */
-static bool dl_entity_overflow(struct sched_dl_entity *dl_se, u64 t)
+static bool dl_entity_overflow(struct sched_dl_entity *dl_se,
+			       struct sched_dl_entity *pi_se, u64 t)
 {
 	u64 left, right;
 
@@ -357,8 +357,8 @@ static bool dl_entity_overflow(struct sched_dl_entity *dl_se, u64 t)
 	 * of anything below microseconds resolution is actually fiction
 	 * (but still we want to give the user that illusion >;).
 	 */
-	left = (dl_se->dl_period >> 10) * (dl_se->runtime >> 10);
-	right = ((dl_se->deadline - t) >> 10) * (dl_se->dl_runtime >> 10);
+	left = (pi_se->dl_period >> 10) * (dl_se->runtime >> 10);
+	right = ((dl_se->deadline - t) >> 10) * (pi_se->dl_runtime >> 10);
 
 	return dl_time_before(right, left);
 }
@@ -372,7 +372,8 @@ static bool dl_entity_overflow(struct sched_dl_entity *dl_se, u64 t)
  *  - using the remaining runtime with the current deadline would make
  *    the entity exceed its bandwidth.
  */
-static void update_dl_entity(struct sched_dl_entity *dl_se)
+static void update_dl_entity(struct sched_dl_entity *dl_se,
+			     struct sched_dl_entity *pi_se)
 {
 	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
 	struct rq *rq = rq_of_dl_rq(dl_rq);
@@ -382,14 +383,14 @@ static void update_dl_entity(struct sched_dl_entity *dl_se)
 	 * the actual scheduling parameters have to be "renewed".
 	 */
 	if (dl_se->dl_new) {
-		setup_new_dl_entity(dl_se);
+		setup_new_dl_entity(dl_se, pi_se);
 		return;
 	}
 
 	if (dl_time_before(dl_se->deadline, rq->clock) ||
-	    dl_entity_overflow(dl_se, rq->clock)) {
-		dl_se->deadline = rq->clock + dl_se->dl_deadline;
-		dl_se->runtime = dl_se->dl_runtime;
+	    dl_entity_overflow(dl_se, pi_se, rq->clock)) {
+		dl_se->deadline = rq->clock + pi_se->dl_deadline;
+		dl_se->runtime = pi_se->dl_runtime;
 	}
 }
 
@@ -403,7 +404,7 @@ static void update_dl_entity(struct sched_dl_entity *dl_se)
  * actually started or not (i.e., the replenishment instant is in
  * the future or in the past).
  */
-static int start_dl_timer(struct sched_dl_entity *dl_se)
+static int start_dl_timer(struct sched_dl_entity *dl_se, bool boosted)
 {
 	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
 	struct rq *rq = rq_of_dl_rq(dl_rq);
@@ -412,6 +413,8 @@ static int start_dl_timer(struct sched_dl_entity *dl_se)
 	unsigned long range;
 	s64 delta;
 
+	if (boosted)
+		return 0;
 	/*
 	 * We want the timer to fire at the deadline, but considering
 	 * that it is actually coming from rq->clock and not from
@@ -586,7 +589,7 @@ static void update_curr_dl(struct rq *rq)
 	dl_se->runtime -= delta_exec;
 	if (dl_runtime_exceeded(rq, dl_se)) {
 		__dequeue_task_dl(rq, curr, 0);
-		if (likely(start_dl_timer(dl_se)))
+		if (likely(start_dl_timer(dl_se, curr->dl.dl_boosted)))
 			dl_se->dl_throttled = 1;
 		else
 			enqueue_task_dl(rq, curr, ENQUEUE_REPLENISH);
@@ -741,7 +744,8 @@ static void __dequeue_dl_entity(struct sched_dl_entity *dl_se)
 }
 
 static void
-enqueue_dl_entity(struct sched_dl_entity *dl_se, int flags)
+enqueue_dl_entity(struct sched_dl_entity *dl_se,
+		  struct sched_dl_entity *pi_se, int flags)
 {
 	BUG_ON(on_dl_rq(dl_se));
 
@@ -751,9 +755,9 @@ enqueue_dl_entity(struct sched_dl_entity *dl_se, int flags)
 	 * we want a replenishment of its runtime.
 	 */
 	if (!dl_se->dl_new && flags & ENQUEUE_REPLENISH)
-		replenish_dl_entity(dl_se);
+		replenish_dl_entity(dl_se, pi_se);
 	else
-		update_dl_entity(dl_se);
+		update_dl_entity(dl_se, pi_se);
 
 	__enqueue_dl_entity(dl_se);
 }
@@ -765,6 +769,18 @@ static void dequeue_dl_entity(struct sched_dl_entity *dl_se)
 
 static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags)
 {
+	struct task_struct *pi_task = p->pi_top_task;
+	struct sched_dl_entity *pi_se = &p->dl;
+
+	/*
+	 * Use the scheduling parameters of the top pi-waiter
+	 * task if we have one and its (relative) deadline is
+	 * smaller than our one... OTW we keep our runtime and
+	 * deadline.
+	 */
+	if (pi_task && p->dl.dl_boosted && dl_prio(pi_task->normal_prio))
+		pi_se = &pi_task->dl;
+
 	/*
 	 * If p is throttled, we do nothing. In fact, if it exhausted
 	 * its budget it needs a replenishment and, since it now is on
@@ -774,7 +790,7 @@ static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags)
 	if (p->dl.dl_throttled)
 		return;
 
-	enqueue_dl_entity(&p->dl, flags);
+	enqueue_dl_entity(&p->dl, pi_se, flags);
 
 	if (!task_current(rq, p) && p->nr_cpus_allowed > 1)
 		enqueue_pushable_dl_task(rq, p);
@@ -1013,8 +1029,7 @@ static void task_dead_dl(struct task_struct *p)
 {
 	struct hrtimer *timer = &p->dl.dl_timer;
 
-	if (hrtimer_active(timer))
-		hrtimer_try_to_cancel(timer);
+	hrtimer_cancel(timer);
 }
 
 static void set_curr_task_dl(struct rq *rq)
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index b04aeed..4da50db 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -105,6 +105,20 @@ static inline int task_has_dl_policy(struct task_struct *p)
 	return dl_policy(p->policy);
 }
 
+static inline int dl_time_before(u64 a, u64 b)
+{
+	return (s64)(a - b) < 0;
+}
+
+/*
+ * Tells if entity @a should preempt entity @b.
+ */
+static inline
+int dl_entity_preempt(struct sched_dl_entity *a, struct sched_dl_entity *b)
+{
+	return dl_time_before(a->deadline, b->deadline);
+}
+
 /*
  * This is the priority-queue data structure of the RT scheduling class:
  */
-- 
1.7.9.5

[PATCH 11/14] sched: add bandwidth management for sched_dl.

[Juri Lelli]

From: Dario Faggioli <raistlin@linux.it>

In order of -deadline scheduling to be effective and useful, it is
important that some method of having the allocation of the available
CPU bandwidth to tasks and task groups under control.
This is usually called "admission control" and if it is not performed
at all, no guarantee can be given on the actual scheduling of the
-deadline tasks.

Since when RT-throttling has been introduced each task group have a
bandwidth associated to itself, calculated as a certain amount of
runtime over a period. Moreover, to make it possible to manipulate
such bandwidth, readable/writable controls have been added to both
procfs (for system wide settings) and cgroupfs (for per-group
settings).
Therefore, the same interface is being used for controlling the
bandwidth distrubution to -deadline tasks and task groups, i.e.,
new controls but with similar names, equivalent meaning and with
the same usage paradigm are added.

However, more discussion is needed in order to figure out how
we want to manage SCHED_DEADLINE bandwidth at the task group level.
Therefore, this patch adds a less sophisticated, but actually
very sensible, mechanism to ensure that a certain utilization
cap is not overcome per each root_domain (the single rq for !SMP
configurations).

Another main difference between deadline bandwidth management and
RT-throttling is that -deadline tasks have bandwidth on their own
(while -rt ones doesn't!), and thus we don't need an higher level
throttling mechanism to enforce the desired bandwidth.

This patch, therefore:
 - adds system wide deadline bandwidth management by means of:
    * /proc/sys/kernel/sched_dl_runtime_us,
    * /proc/sys/kernel/sched_dl_period_us,
   that determine (i.e., runtime / period) the total bandwidth
   available on each CPU of each root_domain for -deadline tasks;
 - couples the RT and deadline bandwidth management, i.e., enforces
   that the sum of how much bandwidth is being devoted to -rt
   -deadline tasks to stay below 100%.

This means that, for a root_domain comprising M CPUs, -deadline tasks
can be created until the sum of their bandwidths stay below:

    M * (sched_dl_runtime_us / sched_dl_period_us)

It is also possible to disable this bandwidth management logic, and
be thus free of oversubscribing the system up to any arbitrary level.

Signed-off-by: Dario Faggioli <raistlin@linux.it>
Signed-off-by: Juri Lelli <juri.lelli@gmail.com>
---
 include/linux/sched.h             |    1 +
 include/linux/sched/sysctl.h      |   13 ++
 kernel/rtmutex.c                  |    1 +
 kernel/sched/core.c               |  431 ++++++++++++++++++++++++++++++++++---
 kernel/sched/deadline.c           |   50 ++++-
 kernel/sched/sched.h              |   74 ++++++-
 kernel/sysctl.c                   |   14 ++
 kernel/trace/trace_sched_wakeup.c |    1 +
 8 files changed, 551 insertions(+), 34 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 17da410..de29080 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1079,6 +1079,7 @@ struct sched_dl_entity {
 	u64 dl_runtime;		/* maximum runtime for each instance	*/
 	u64 dl_deadline;	/* relative deadline of each instance	*/
 	u64 dl_period;		/* separation of two instances (period) */
+	u64 dl_bw;		/* dl_runtime / dl_deadline		*/
 
 	/*
 	 * Actual scheduling parameters. Initialized with the values above,
diff --git a/include/linux/sched/sysctl.h b/include/linux/sched/sysctl.h
index bf8086b..33fbf32 100644
--- a/include/linux/sched/sysctl.h
+++ b/include/linux/sched/sysctl.h
@@ -83,6 +83,15 @@ static inline unsigned int get_sysctl_timer_migration(void)
 extern unsigned int sysctl_sched_rt_period;
 extern int sysctl_sched_rt_runtime;
 
+/*
+ *  control SCHED_DEADLINE reservations:
+ *
+ *  /proc/sys/kernel/sched_dl_period_us
+ *  /proc/sys/kernel/sched_dl_runtime_us
+ */
+extern unsigned int sysctl_sched_dl_period;
+extern int sysctl_sched_dl_runtime;
+
 #ifdef CONFIG_CFS_BANDWIDTH
 extern unsigned int sysctl_sched_cfs_bandwidth_slice;
 #endif
@@ -101,4 +110,8 @@ extern int sched_rt_handler(struct ctl_table *table, int write,
 		void __user *buffer, size_t *lenp,
 		loff_t *ppos);
 
+int sched_dl_handler(struct ctl_table *table, int write,
+		void __user *buffer, size_t *lenp,
+		loff_t *ppos);
+
 #endif /* _SCHED_SYSCTL_H */
diff --git a/kernel/rtmutex.c b/kernel/rtmutex.c
index cb5f950..f7f667e 100644
--- a/kernel/rtmutex.c
+++ b/kernel/rtmutex.c
@@ -14,6 +14,7 @@
 #include <linux/export.h>
 #include <linux/sched.h>
 #include <linux/sched/rt.h>
+#include <linux/sched/deadline.h>
 #include <linux/timer.h>
 
 #include "rtmutex_common.h"
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index f9e7906..ee0ba8b 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -296,6 +296,15 @@ __read_mostly int scheduler_running;
  */
 int sysctl_sched_rt_runtime = 950000;
 
+/*
+ * Maximum bandwidth available for all -deadline tasks and groups
+ * (if group scheduling is configured) on each CPU.
+ *
+ * default: 5%
+ */
+unsigned int sysctl_sched_dl_period = 1000000;
+int sysctl_sched_dl_runtime = 50000;
+
 
 
 /*
@@ -1745,6 +1754,96 @@ int sched_fork(struct task_struct *p)
 	return 0;
 }
 
+unsigned long to_ratio(u64 period, u64 runtime)
+{
+	if (runtime == RUNTIME_INF)
+		return 1ULL << 20;
+
+	/*
+	 * Doing this here saves a lot of checks in all
+	 * the calling paths, and returning zero seems
+	 * safe for them anyway.
+	 */
+	if (period == 0)
+		return 0;
+
+	return div64_u64(runtime << 20, period);
+}
+
+static inline
+void __dl_clear(struct dl_bw *dl_b, u64 tsk_bw)
+{
+	dl_b->total_bw -= tsk_bw;
+}
+
+static inline
+void __dl_add(struct dl_bw *dl_b, u64 tsk_bw)
+{
+	dl_b->total_bw += tsk_bw;
+}
+
+static inline
+bool __dl_overflow(struct dl_bw *dl_b, int cpus, u64 old_bw, u64 new_bw)
+{
+	return dl_b->bw != -1 &&
+	       dl_b->bw * cpus < dl_b->total_bw - old_bw + new_bw;
+}
+
+/*
+ * We must be sure that accepting a new task (or allowing changing the
+ * parameters of an existing one) is consistent with the bandwidth
+ * constraints. If yes, this function also accordingly updates the currently
+ * allocated bandwidth to reflect the new situation.
+ *
+ * This function is called while holding p's rq->lock.
+ */
+static int dl_overflow(struct task_struct *p, int policy,
+		       const struct sched_param2 *param2)
+{
+#ifdef CONFIG_SMP
+	struct dl_bw *dl_b = &task_rq(p)->rd->dl_bw;
+#else
+	struct dl_bw *dl_b = &task_rq(p)->dl.dl_bw;
+#endif
+	u64 period = param2->sched_period;
+	u64 runtime = param2->sched_runtime;
+	u64 new_bw = dl_policy(policy) ? to_ratio(period, runtime) : 0;
+#ifdef CONFIG_SMP
+	int cpus = cpumask_weight(task_rq(p)->rd->span);
+#else
+	int cpus = 1;
+#endif
+	int err = -1;
+
+	if (new_bw == p->dl.dl_bw)
+		return 0;
+
+	/*
+	 * Either if a task, enters, leave, or stays -deadline but changes
+	 * its parameters, we may need to update accordingly the total
+	 * allocated bandwidth of the container.
+	 */
+	raw_spin_lock(&dl_b->lock);
+	if (dl_policy(policy) && !task_has_dl_policy(p) &&
+	    !__dl_overflow(dl_b, cpus, 0, new_bw)) {
+		__dl_add(dl_b, new_bw);
+		err = 0;
+	} else if (dl_policy(policy) && task_has_dl_policy(p) &&
+		   !__dl_overflow(dl_b, cpus, p->dl.dl_bw, new_bw)) {
+		__dl_clear(dl_b, p->dl.dl_bw);
+		__dl_add(dl_b, new_bw);
+		err = 0;
+	} else if (!dl_policy(policy) && task_has_dl_policy(p)) {
+		__dl_clear(dl_b, p->dl.dl_bw);
+		err = 0;
+	}
+	raw_spin_unlock(&dl_b->lock);
+
+	return err;
+}
+
+extern void init_dl_bw(struct dl_bw *dl_b);
+
 /*
  * wake_up_new_task - wake up a newly created task for the first time.
  *
@@ -3333,6 +3432,7 @@ __setparam_dl(struct task_struct *p, const struct sched_param2 *param2)
 		dl_se->dl_period = param2->sched_period;
 	else
 		dl_se->dl_period = dl_se->dl_deadline;
+	dl_se->dl_bw = to_ratio(dl_se->dl_period, dl_se->dl_runtime);
 	dl_se->flags = param2->sched_flags;
 	dl_se->dl_throttled = 0;
 	dl_se->dl_new = 1;
@@ -3354,15 +3454,18 @@ __getparam_dl(struct task_struct *p, struct sched_param2 *param2)
  * This function validates the new parameters of a -deadline task.
  * We ask for the deadline not being zero, and greater or equal
  * than the runtime, as well as the period of being zero or
- * greater than deadline.
+ * greater than deadline. Furthermore, we have to be sure that
+ * user parameters are above the internal resolution (1us); we
+ * check sched_runtime only since it is always the smaller one.
  */
 static bool
 __checkparam_dl(const struct sched_param2 *prm)
 {
 	return prm && prm->sched_deadline != 0 &&
 	       (prm->sched_period == 0 ||
-		(s64)(prm->sched_period - prm->sched_deadline) >= 0) &&
-	       (s64)(prm->sched_deadline - prm->sched_runtime) >= 0;
+	       (s64)(prm->sched_period - prm->sched_deadline) >= 0) &&
+	       (s64)(prm->sched_deadline - prm->sched_runtime) >= 0 &&
+	       prm->sched_runtime >= (2 << (DL_SCALE - 1));
 }
 
 /*
@@ -3491,8 +3594,8 @@ recheck:
 		return 0;
 	}
 
-#ifdef CONFIG_RT_GROUP_SCHED
 	if (user) {
+#ifdef CONFIG_RT_GROUP_SCHED
 		/*
 		 * Do not allow realtime tasks into groups that have no runtime
 		 * assigned.
@@ -3503,8 +3606,34 @@ recheck:
 			task_rq_unlock(rq, p, &flags);
 			return -EPERM;
 		}
-	}
 #endif
+#ifdef CONFIG_SMP
+		if (dl_bandwidth_enabled() && dl_policy(policy)) {
+			cpumask_t *span = rq->rd->span;
+			cpumask_t act_affinity;
+
+			/*
+			 * cpus_allowed mask is statically initialized with
+			 * CPU_MASK_ALL, span is instead dynamic. Here we
+			 * compute the "dynamic" affinity of a task.
+			 */
+			cpumask_and(&act_affinity, &p->cpus_allowed,
+				    cpu_active_mask);
+
+			/*
+			 * Don't allow tasks with an affinity mask smaller than
+			 * the entire root_domain to become SCHED_DEADLINE. We
+			 * will also fail if there's no bandwidth available.
+			 */
+			if (!cpumask_equal(&act_affinity, span) ||
+			    		   rq->rd->dl_bw.bw == 0) {
+				__task_rq_unlock(rq);
+				raw_spin_unlock_irqrestore(&p->pi_lock, flags);
+				return -EPERM;
+			}
+		}
+#endif
+	}
 
 	/* recheck policy now with rq lock held */
 	if (unlikely(oldpolicy != -1 && oldpolicy != p->policy)) {
@@ -3512,6 +3641,19 @@ recheck:
 		task_rq_unlock(rq, p, &flags);
 		goto recheck;
 	}
+
+	/*
+	 * If setscheduling to SCHED_DEADLINE (or changing the parameters
+	 * of a SCHED_DEADLINE task) we need to check if enough bandwidth
+	 * is available.
+	 */
+	if ((dl_policy(policy) || dl_task(p)) &&
+	    dl_overflow(p, policy, param)) {
+		__task_rq_unlock(rq);
+		raw_spin_unlock_irqrestore(&p->pi_lock, flags);
+		return -EBUSY;
+	}
+
 	on_rq = p->on_rq;
 	running = task_current(rq, p);
 	if (on_rq)
@@ -3855,6 +3997,24 @@ long sched_setaffinity(pid_t pid, const struct cpumask *in_mask)
 	if (retval)
 		goto out_unlock;
 
+	/*
+	 * Since bandwidth control happens on root_domain basis,
+	 * if admission test is enabled, we only admit -deadline
+	 * tasks allowed to run on all the CPUs in the task's
+	 * root_domain.
+	 */
+#ifdef CONFIG_SMP
+	if (task_has_dl_policy(p)) {
+		const struct cpumask *span = task_rq(p)->rd->span;
+
+		if (dl_bandwidth_enabled() &&
+		    !cpumask_equal(in_mask, span)) {
+			retval = -EBUSY;
+			goto out_unlock;
+		}
+	}
+#endif
+
 	cpuset_cpus_allowed(p, cpus_allowed);
 	cpumask_and(new_mask, in_mask, cpus_allowed);
 again:
@@ -4518,6 +4678,42 @@ out:
 EXPORT_SYMBOL_GPL(set_cpus_allowed_ptr);
 
 /*
+ * When dealing with a -deadline task, we have to check if moving it to
+ * a new CPU is possible or not. In fact, this is only true iff there
+ * is enough bandwidth available on such CPU, otherwise we want the
+ * whole migration progedure to fail over.
+ */
+static inline
+bool set_task_cpu_dl(struct task_struct *p, unsigned int cpu)
+{
+	struct dl_bw *dl_b = &task_rq(p)->rd->dl_bw;
+	struct dl_bw *cpu_b = &cpu_rq(cpu)->rd->dl_bw;
+	int ret = 1;
+	u64 bw;
+
+	if (dl_b == cpu_b)
+		return 1;
+
+	raw_spin_lock(&dl_b->lock);
+	raw_spin_lock(&cpu_b->lock);
+
+	bw = cpu_b->bw * cpumask_weight(cpu_rq(cpu)->rd->span);
+	if (dl_bandwidth_enabled() &&
+	    bw < cpu_b->total_bw + p->dl.dl_bw) {
+		ret = 0;
+		goto unlock;
+	}
+	dl_b->total_bw -= p->dl.dl_bw;
+	cpu_b->total_bw += p->dl.dl_bw;
+
+unlock:
+	raw_spin_unlock(&cpu_b->lock);
+	raw_spin_unlock(&dl_b->lock);
+
+	return ret;
+}
+
+/*
  * Move (not current) task off this cpu, onto dest cpu. We're doing
  * this because either it can't run here any more (set_cpus_allowed()
  * away from this CPU, or CPU going down), or because we're
@@ -4549,6 +4745,13 @@ static int __migrate_task(struct task_struct *p, int src_cpu, int dest_cpu)
 		goto fail;
 
 	/*
+	 * If p is -deadline, proceed only if there is enough
+	 * bandwidth available on dest_cpu
+	 */
+	if (unlikely(dl_task(p)) && !set_task_cpu_dl(p, dest_cpu))
+		goto fail;
+
+	/*
 	 * If we're not on a rq, the next wake-up will ensure we're
 	 * placed properly.
 	 */
@@ -5240,6 +5443,8 @@ static int init_rootdomain(struct root_domain *rd)
 	if (!alloc_cpumask_var(&rd->rto_mask, GFP_KERNEL))
 		goto free_dlo_mask;
 
+	init_dl_bw(&rd->dl_bw);
+
 	if (cpupri_init(&rd->cpupri) != 0)
 		goto free_rto_mask;
 	return 0;
@@ -6658,6 +6863,8 @@ void __init sched_init(void)
 
 	init_rt_bandwidth(&def_rt_bandwidth,
 			global_rt_period(), global_rt_runtime());
+	init_dl_bandwidth(&def_dl_bandwidth,
+			global_dl_period(), global_dl_runtime());
 
 #ifdef CONFIG_RT_GROUP_SCHED
 	init_rt_bandwidth(&root_task_group.rt_bandwidth,
@@ -7057,16 +7264,6 @@ void sched_move_task(struct task_struct *tsk)
 }
 #endif /* CONFIG_CGROUP_SCHED */
 
-#if defined(CONFIG_RT_GROUP_SCHED) || defined(CONFIG_CFS_BANDWIDTH)
-static unsigned long to_ratio(u64 period, u64 runtime)
-{
-	if (runtime == RUNTIME_INF)
-		return 1ULL << 20;
-
-	return div64_u64(runtime << 20, period);
-}
-#endif
-
 #ifdef CONFIG_RT_GROUP_SCHED
 /*
  * Ensure that the real time constraints are schedulable.
@@ -7240,10 +7437,48 @@ static long sched_group_rt_period(struct task_group *tg)
 	do_div(rt_period_us, NSEC_PER_USEC);
 	return rt_period_us;
 }
+#endif /* CONFIG_RT_GROUP_SCHED */
+
+/*
+ * Coupling of -rt and -deadline bandwidth.
+ *
+ * Here we check if the new -rt bandwidth value is consistent
+ * with the system settings for the bandwidth available
+ * to -deadline tasks.
+ *
+ * IOW, we want to enforce that
+ *
+ *   rt_bandwidth + dl_bandwidth <= 100%
+ *
+ * is always true.
+ */
+static bool __sched_rt_dl_global_constraints(u64 rt_bw)
+{
+	unsigned long flags;
+	u64 dl_bw;
+	bool ret;
+
+	raw_spin_lock_irqsave(&def_dl_bandwidth.dl_runtime_lock, flags);
+	if (global_rt_runtime() == RUNTIME_INF ||
+	    global_dl_runtime() == RUNTIME_INF) {
+		ret = true;
+		goto unlock;
+	}
+
+	dl_bw = to_ratio(def_dl_bandwidth.dl_period,
+			 def_dl_bandwidth.dl_runtime);
+
+	ret = rt_bw + dl_bw <= to_ratio(RUNTIME_INF, RUNTIME_INF);
+unlock:
+	raw_spin_unlock_irqrestore(&def_dl_bandwidth.dl_runtime_lock, flags);
+
+	return ret;
+}
 
+#ifdef CONFIG_RT_GROUP_SCHED
 static int sched_rt_global_constraints(void)
 {
-	u64 runtime, period;
+	u64 runtime, period, bw;
 	int ret = 0;
 
 	if (sysctl_sched_rt_period <= 0)
@@ -7258,6 +7493,10 @@ static int sched_rt_global_constraints(void)
 	if (runtime > period && runtime != RUNTIME_INF)
 		return -EINVAL;
 
+	bw = to_ratio(period, runtime);
+	if (!__sched_rt_dl_global_constraints(bw))
+		return -EINVAL;
+
 	mutex_lock(&rt_constraints_mutex);
 	read_lock(&tasklist_lock);
 	ret = __rt_schedulable(NULL, 0, 0);
@@ -7280,19 +7519,19 @@ static int sched_rt_can_attach(struct task_group *tg, struct task_struct *tsk)
 static int sched_rt_global_constraints(void)
 {
 	unsigned long flags;
-	int i;
+	int i, ret = 0;
+	u64 bw;
 
 	if (sysctl_sched_rt_period <= 0)
 		return -EINVAL;
 
-	/*
-	 * There's always some RT tasks in the root group
-	 * -- migration, kstopmachine etc..
-	 */
-	if (sysctl_sched_rt_runtime == 0)
-		return -EBUSY;
-
 	raw_spin_lock_irqsave(&def_rt_bandwidth.rt_runtime_lock, flags);
+	bw = to_ratio(global_rt_period(), global_rt_runtime());
+	if (!__sched_rt_dl_global_constraints(bw)) {
+		ret = -EINVAL;
+		goto unlock;
+	}
+
 	for_each_possible_cpu(i) {
 		struct rt_rq *rt_rq = &cpu_rq(i)->rt;
 
@@ -7300,12 +7539,96 @@ static int sched_rt_global_constraints(void)
 		rt_rq->rt_runtime = global_rt_runtime();
 		raw_spin_unlock(&rt_rq->rt_runtime_lock);
 	}
+unlock:
 	raw_spin_unlock_irqrestore(&def_rt_bandwidth.rt_runtime_lock, flags);
 
-	return 0;
+	return ret;
 }
 #endif /* CONFIG_RT_GROUP_SCHED */
 
+/*
+ * Coupling of -dl and -rt bandwidth.
+ *
+ * Here we check, while setting the system wide bandwidth available
+ * for -dl tasks and groups, if the new values are consistent with
+ * the system settings for the bandwidth available to -rt entities.
+ *
+ * IOW, we want to enforce that
+ *
+ *   rt_bandwidth + dl_bandwidth <= 100%
+ *
+ * is always true.
+ */
+static bool __sched_dl_rt_global_constraints(u64 dl_bw)
+{
+	u64 rt_bw;
+	bool ret;
+
+	raw_spin_lock(&def_rt_bandwidth.rt_runtime_lock);
+	if (global_dl_runtime() == RUNTIME_INF ||
+	    global_rt_runtime() == RUNTIME_INF) {
+		ret = true;
+		goto unlock;
+	}
+
+	rt_bw = to_ratio(ktime_to_ns(def_rt_bandwidth.rt_period),
+			 def_rt_bandwidth.rt_runtime);
+
+	ret = rt_bw + dl_bw <= to_ratio(RUNTIME_INF, RUNTIME_INF);
+unlock:
+	raw_spin_unlock(&def_rt_bandwidth.rt_runtime_lock);
+
+	return ret;
+}
+
+static bool __sched_dl_global_constraints(u64 runtime, u64 period)
+{
+	if (!period || (runtime != RUNTIME_INF && runtime > period))
+		return -EINVAL;
+
+	return 0;
+}
+
+static int sched_dl_global_constraints(void)
+{
+	u64 runtime = global_dl_runtime();
+	u64 period = global_dl_period();
+	u64 new_bw = to_ratio(period, runtime);
+	int ret, i;
+
+	ret = __sched_dl_global_constraints(runtime, period);
+	if (ret)
+		return ret;
+
+	if (!__sched_dl_rt_global_constraints(new_bw))
+		return -EINVAL;
+
+	/*
+	 * Here we want to check the bandwidth not being set to some
+	 * value smaller than the currently allocated bandwidth in
+	 * any of the root_domains.
+	 *
+	 * FIXME: Cycling on all the CPUs is overdoing, but simpler than
+	 * cycling on root_domains... Discussion on different/better
+	 * solutions is welcome!
+	 */
+	for_each_possible_cpu(i) {
+#ifdef CONFIG_SMP
+		struct dl_bw *dl_b = &cpu_rq(i)->rd->dl_bw;
+#else
+		struct dl_bw *dl_b = &cpu_rq(i)->dl.dl_bw;
+#endif
+		raw_spin_lock(&dl_b->lock);
+		if (new_bw < dl_b->total_bw) {
+			raw_spin_unlock(&dl_b->lock);
+			return -EBUSY;
+		}
+		raw_spin_unlock(&dl_b->lock);
+	}
+
+	return 0;
+}
+
 int sched_rr_handler(struct ctl_table *table, int write,
 		void __user *buffer, size_t *lenp,
 		loff_t *ppos)
@@ -7355,6 +7678,64 @@ int sched_rt_handler(struct ctl_table *table, int write,
 	return ret;
 }
 
+int sched_dl_handler(struct ctl_table *table, int write,
+		void __user *buffer, size_t *lenp,
+		loff_t *ppos)
+{
+	int ret;
+	int old_period, old_runtime;
+	static DEFINE_MUTEX(mutex);
+	unsigned long flags;
+
+	mutex_lock(&mutex);
+	old_period = sysctl_sched_dl_period;
+	old_runtime = sysctl_sched_dl_runtime;
+
+	ret = proc_dointvec(table, write, buffer, lenp, ppos);
+
+	if (!ret && write) {
+		raw_spin_lock_irqsave(&def_dl_bandwidth.dl_runtime_lock,
+				      flags);
+
+		ret = sched_dl_global_constraints();
+		if (ret) {
+			sysctl_sched_dl_period = old_period;
+			sysctl_sched_dl_runtime = old_runtime;
+		} else {
+			u64 new_bw;
+			int i;
+
+			def_dl_bandwidth.dl_period = global_dl_period();
+			def_dl_bandwidth.dl_runtime = global_dl_runtime();
+			if (global_dl_runtime() == RUNTIME_INF)
+				new_bw = -1;
+			else
+				new_bw = to_ratio(global_dl_period(),
+						  global_dl_runtime());
+			/*
+			 * FIXME: As above...
+			 */
+			for_each_possible_cpu(i) {
+#ifdef CONFIG_SMP
+				struct dl_bw *dl_b = &cpu_rq(i)->rd->dl_bw;
+#else
+				struct dl_bw *dl_b = &cpu_rq(i)->dl.dl_bw;
+#endif
+
+				raw_spin_lock(&dl_b->lock);
+				dl_b->bw = new_bw;
+				raw_spin_unlock(&dl_b->lock);
+			}
+		}
+
+		raw_spin_unlock_irqrestore(&def_dl_bandwidth.dl_runtime_lock,
+					   flags);
+	}
+	mutex_unlock(&mutex);
+
+	return ret;
+}
+
 #ifdef CONFIG_CGROUP_SCHED
 
 static inline struct task_group *css_tg(struct cgroup_subsys_state *css)
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index aded515..35d7c2d 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -16,6 +16,8 @@
  */
 #include "sched.h"
 
+struct dl_bandwidth def_dl_bandwidth;
+
 static inline struct task_struct *dl_task_of(struct sched_dl_entity *dl_se)
 {
 	return container_of(dl_se, struct task_struct, dl);
@@ -46,6 +48,27 @@ static inline int is_leftmost(struct task_struct *p, struct dl_rq *dl_rq)
 	return dl_rq->rb_leftmost == &dl_se->rb_node;
 }
 
+void init_dl_bandwidth(struct dl_bandwidth *dl_b, u64 period, u64 runtime)
+{
+	raw_spin_lock_init(&dl_b->dl_runtime_lock);
+	dl_b->dl_period = period;
+	dl_b->dl_runtime = runtime;
+}
+
+extern unsigned long to_ratio(u64 period, u64 runtime);
+
+void init_dl_bw(struct dl_bw *dl_b)
+{
+	raw_spin_lock_init(&dl_b->lock);
+	raw_spin_lock(&def_dl_bandwidth.dl_runtime_lock);
+	if (global_dl_runtime() == RUNTIME_INF)
+		dl_b->bw = -1;
+	else
+		dl_b->bw = to_ratio(global_dl_period(), global_dl_runtime());
+	raw_spin_unlock(&def_dl_bandwidth.dl_runtime_lock);
+	dl_b->total_bw = 0;
+}
+
 void init_dl_rq(struct dl_rq *dl_rq, struct rq *rq)
 {
 	dl_rq->rb_root = RB_ROOT;
@@ -57,6 +80,8 @@ void init_dl_rq(struct dl_rq *dl_rq, struct rq *rq)
 	dl_rq->dl_nr_migratory = 0;
 	dl_rq->overloaded = 0;
 	dl_rq->pushable_dl_tasks_root = RB_ROOT;
+#else
+	init_dl_bw(&dl_rq->dl_bw);
 #endif
 }
 
@@ -357,8 +382,9 @@ static bool dl_entity_overflow(struct sched_dl_entity *dl_se,
 	 * of anything below microseconds resolution is actually fiction
 	 * (but still we want to give the user that illusion >;).
 	 */
-	left = (pi_se->dl_period >> 10) * (dl_se->runtime >> 10);
-	right = ((dl_se->deadline - t) >> 10) * (pi_se->dl_runtime >> 10);
+	left = (pi_se->dl_period >> DL_SCALE) * (dl_se->runtime >> DL_SCALE);
+	right = ((dl_se->deadline - t) >> DL_SCALE) *
+		(pi_se->dl_runtime >> DL_SCALE);
 
 	return dl_time_before(right, left);
 }
@@ -923,8 +949,8 @@ static void check_preempt_curr_dl(struct rq *rq, struct task_struct *p,
 	 * In the unlikely case current and p have the same deadline
 	 * let us try to decide what's the best thing to do...
 	 */
-	if ((s64)(p->dl.deadline - rq->curr->dl.deadline) == 0 &&
-	    !need_resched())
+	if ((p->dl.deadline == rq->curr->dl.deadline) &&
+	    !test_tsk_need_resched(rq->curr))
 		check_preempt_equal_dl(rq, p);
 #endif /* CONFIG_SMP */
 }
@@ -1028,6 +1054,18 @@ static void task_fork_dl(struct task_struct *p)
 static void task_dead_dl(struct task_struct *p)
 {
 	struct hrtimer *timer = &p->dl.dl_timer;
+#ifdef CONFIG_SMP
+	struct dl_bw *dl_b = &task_rq(p)->rd->dl_bw;
+#else
+	struct dl_bw *dl_b = &task_rq(p)->dl.dl_bw;
+#endif
+
+	/*
+	 * Since we are TASK_DEAD we won't slip out of the domain!
+	 */
+	raw_spin_lock_irq(&dl_b->lock);
+	dl_b->total_bw -= p->dl.dl_bw;
+	raw_spin_unlock_irq(&dl_b->lock);
 
 	hrtimer_cancel(timer);
 }
@@ -1254,7 +1292,7 @@ static struct task_struct *pick_next_pushable_dl_task(struct rq *rq)
 	BUG_ON(task_current(rq, p));
 	BUG_ON(p->nr_cpus_allowed <= 1);
 
-	BUG_ON(!p->se.on_rq);
+	BUG_ON(!p->on_rq);
 	BUG_ON(!dl_task(p));
 
 	return p;
@@ -1395,7 +1433,7 @@ static int pull_dl_task(struct rq *this_rq)
 		     dl_time_before(p->dl.deadline,
 				    this_rq->dl.earliest_dl.curr))) {
 			WARN_ON(p == src_rq->curr);
-			WARN_ON(!p->se.on_rq);
+			WARN_ON(!p->on_rq);
 
 			/*
 			 * Then we pull iff p has actually an earlier
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 4da50db..08931a6 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -81,6 +81,13 @@ extern void update_cpu_load_active(struct rq *this_rq);
  */
 #define RUNTIME_INF	((u64)~0ULL)
 
+/*
+ * Single value that decides SCHED_DEADLINE internal math precision.
+ * 10 -> just above 1us
+ * 9  -> just above 0.5us
+ */
+#define DL_SCALE (10)
+
 static inline int rt_policy(int policy)
 {
 	if (policy == SCHED_FIFO || policy == SCHED_RR)
@@ -105,7 +112,7 @@ static inline int task_has_dl_policy(struct task_struct *p)
 	return dl_policy(p->policy);
 }
 
-static inline int dl_time_before(u64 a, u64 b)
+static inline bool dl_time_before(u64 a, u64 b)
 {
 	return (s64)(a - b) < 0;
 }
@@ -113,8 +120,8 @@ static inline int dl_time_before(u64 a, u64 b)
 /*
  * Tells if entity @a should preempt entity @b.
  */
-static inline
-int dl_entity_preempt(struct sched_dl_entity *a, struct sched_dl_entity *b)
+static inline bool
+dl_entity_preempt(struct sched_dl_entity *a, struct sched_dl_entity *b)
 {
 	return dl_time_before(a->deadline, b->deadline);
 }
@@ -134,6 +141,48 @@ struct rt_bandwidth {
 	u64			rt_runtime;
 	struct hrtimer		rt_period_timer;
 };
+/*
+ * To keep the bandwidth of -deadline tasks and groups under control
+ * we need some place where:
+ *  - store the maximum -deadline bandwidth of the system (the group);
+ *  - cache the fraction of that bandwidth that is currently allocated.
+ *
+ * This is all done in the data structure below. It is similar to the
+ * one used for RT-throttling (rt_bandwidth), with the main difference
+ * that, since here we are only interested in admission control, we
+ * do not decrease any runtime while the group "executes", neither we
+ * need a timer to replenish it.
+ *
+ * With respect to SMP, the bandwidth is given on a per-CPU basis,
+ * meaning that:
+ *  - dl_bw (< 100%) is the bandwidth of the system (group) on each CPU;
+ *  - dl_total_bw array contains, in the i-eth element, the currently
+ *    allocated bandwidth on the i-eth CPU.
+ * Moreover, groups consume bandwidth on each CPU, while tasks only
+ * consume bandwidth on the CPU they're running on.
+ * Finally, dl_total_bw_cpu is used to cache the index of dl_total_bw
+ * that will be shown the next time the proc or cgroup controls will
+ * be red. It on its turn can be changed by writing on its own
+ * control.
+ */
+struct dl_bandwidth {
+	raw_spinlock_t dl_runtime_lock;
+	u64 dl_runtime;
+	u64 dl_period;
+};
+
+static inline int dl_bandwidth_enabled(void)
+{
+	return sysctl_sched_dl_runtime >= 0;
+}
+
+struct dl_bw {
+	raw_spinlock_t lock;
+	u64 bw, total_bw;
+};
+
+static inline u64 global_dl_period(void);
+static inline u64 global_dl_runtime(void);
 
 extern struct mutex sched_domains_mutex;
 
@@ -423,6 +472,8 @@ struct dl_rq {
 	 */
 	struct rb_root pushable_dl_tasks_root;
 	struct rb_node *pushable_dl_tasks_leftmost;
+#else
+	struct dl_bw dl_bw;
 #endif
 };
 
@@ -454,6 +505,7 @@ struct root_domain {
 	 */
 	cpumask_var_t dlo_mask;
 	atomic_t dlo_count;
+	struct dl_bw dl_bw;
 
 	/*
 	 * The "RT overload" flag: it gets set if a CPU has more than
@@ -872,7 +924,18 @@ static inline u64 global_rt_runtime(void)
 	return (u64)sysctl_sched_rt_runtime * NSEC_PER_USEC;
 }
 
+static inline u64 global_dl_period(void)
+{
+	return (u64)sysctl_sched_dl_period * NSEC_PER_USEC;
+}
+
+static inline u64 global_dl_runtime(void)
+{
+	if (sysctl_sched_dl_runtime < 0)
+		return RUNTIME_INF;
 
+	return (u64)sysctl_sched_dl_runtime * NSEC_PER_USEC;
+}
 
 static inline int task_current(struct rq *rq, struct task_struct *p)
 {
@@ -1120,6 +1183,7 @@ extern void update_max_interval(void);
 extern void init_sched_dl_class(void);
 extern void init_sched_rt_class(void);
 extern void init_sched_fair_class(void);
+extern void init_sched_dl_class(void);
 
 extern void resched_task(struct task_struct *p);
 extern void resched_cpu(int cpu);
@@ -1127,8 +1191,12 @@ extern void resched_cpu(int cpu);
 extern struct rt_bandwidth def_rt_bandwidth;
 extern void init_rt_bandwidth(struct rt_bandwidth *rt_b, u64 period, u64 runtime);
 
+extern struct dl_bandwidth def_dl_bandwidth;
+extern void init_dl_bandwidth(struct dl_bandwidth *dl_b, u64 period, u64 runtime);
 extern void init_dl_task_timer(struct sched_dl_entity *dl_se);
 
+unsigned long to_ratio(u64 period, u64 runtime);
+
 extern void update_idle_cpu_load(struct rq *this_rq);
 
 extern void init_task_runnable_average(struct task_struct *p);
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index b2f06f3..f0cf6d6 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -414,6 +414,20 @@ static struct ctl_table kern_table[] = {
 		.mode		= 0644,
 		.proc_handler	= sched_rr_handler,
 	},
+	{
+		.procname	= "sched_dl_period_us",
+		.data		= &sysctl_sched_dl_period,
+		.maxlen		= sizeof(unsigned int),
+		.mode		= 0644,
+		.proc_handler	= sched_dl_handler,
+	},
+	{
+		.procname	= "sched_dl_runtime_us",
+		.data		= &sysctl_sched_dl_runtime,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= sched_dl_handler,
+	},
 #ifdef CONFIG_SCHED_AUTOGROUP
 	{
 		.procname	= "sched_autogroup_enabled",
diff --git a/kernel/trace/trace_sched_wakeup.c b/kernel/trace/trace_sched_wakeup.c
index 1457fb1..b5a9f02 100644
--- a/kernel/trace/trace_sched_wakeup.c
+++ b/kernel/trace/trace_sched_wakeup.c
@@ -16,6 +16,7 @@
 #include <linux/uaccess.h>
 #include <linux/ftrace.h>
 #include <linux/sched/rt.h>
+#include <linux/sched/deadline.h>
 #include <trace/events/sched.h>
 #include "trace.h"
 
-- 
1.7.9.5

[PATCH 12/14] sched: make dl_bw a sub-quota of rt_bw

[Juri Lelli]

Change real-time bandwidth management as to make dl_bw a sub-quota
of rt_bw. This patch leaves rt_bw at its default value and sets
dl_bw at 40% of rt_bw. It also remove sched_dl_period_us control
knob using sched_rt_period_us as common period for both rt_bw and
dl_bw.

Checks are made when the user tries to change dl_bw sub-quota as to
not fall below what currently used. Since dl_bw now depends upon
rt_bw, similar checks are performed when the users modifies rt_bw
and dl_bw is changed accordingly. Setting rt_bw sysctl variable to
-1 (actually disabling rt throttling) disables dl_bw checks as well.

Signed-off-by: Juri Lelli <juri.lelli@gmail.com>
---
 include/linux/sched/sysctl.h |    2 -
 kernel/sched/core.c          |  285 ++++++++++++++++++++----------------------
 kernel/sched/deadline.c      |    5 +-
 kernel/sched/sched.h         |   24 ++--
 kernel/sysctl.c              |    7 --
 5 files changed, 147 insertions(+), 176 deletions(-)

diff --git a/include/linux/sched/sysctl.h b/include/linux/sched/sysctl.h
index 33fbf32..444a257 100644
--- a/include/linux/sched/sysctl.h
+++ b/include/linux/sched/sysctl.h
@@ -86,10 +86,8 @@ extern int sysctl_sched_rt_runtime;
 /*
  *  control SCHED_DEADLINE reservations:
  *
- *  /proc/sys/kernel/sched_dl_period_us
  *  /proc/sys/kernel/sched_dl_runtime_us
  */
-extern unsigned int sysctl_sched_dl_period;
 extern int sysctl_sched_dl_runtime;
 
 #ifdef CONFIG_CFS_BANDWIDTH
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index ee0ba8b..ddc1f49 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -297,13 +297,12 @@ __read_mostly int scheduler_running;
 int sysctl_sched_rt_runtime = 950000;
 
 /*
- * Maximum bandwidth available for all -deadline tasks and groups
- * (if group scheduling is configured) on each CPU.
+ * Sub-quota or rt bandwidth available for all -deadline tasks
+ * on each CPU.
  *
- * default: 5%
+ * default: 40%
  */
-unsigned int sysctl_sched_dl_period = 1000000;
-int sysctl_sched_dl_runtime = 50000;
+int sysctl_sched_dl_runtime = 400000;
 
 
 
@@ -6816,6 +6815,8 @@ LIST_HEAD(task_groups);
 
 DECLARE_PER_CPU(cpumask_var_t, load_balance_mask);
 
+static u64 actual_dl_runtime(void);
+
 void __init sched_init(void)
 {
 	int i, j;
@@ -6863,8 +6864,7 @@ void __init sched_init(void)
 
 	init_rt_bandwidth(&def_rt_bandwidth,
 			global_rt_period(), global_rt_runtime());
-	init_dl_bandwidth(&def_dl_bandwidth,
-			global_dl_period(), global_dl_runtime());
+	init_dl_bandwidth(&def_dl_bandwidth, actual_dl_runtime());
 
 #ifdef CONFIG_RT_GROUP_SCHED
 	init_rt_bandwidth(&root_task_group.rt_bandwidth,
@@ -7264,6 +7264,93 @@ void sched_move_task(struct task_struct *tsk)
 }
 #endif /* CONFIG_CGROUP_SCHED */
 
+static u64 actual_dl_runtime(void)
+{
+	u64 dl_runtime = global_dl_runtime();
+	u64 rt_runtime = global_rt_runtime();
+	u64 period = global_rt_period();
+
+	/*
+	 * We want to calculate the sub-quota of rt_bw actually available
+	 * for -dl tasks. It is a percentage of percentage. By default 95%
+	 * of system bandwidth is allocate to -rt tasks; among this, a 40%
+	 * quota is reserved for -dl tasks. To have the actual quota a simple
+	 * multiplication is needed: .95 * .40 = .38 (38% of system bandwidth
+	 * for deadline tasks).
+	 * What follows is basically the same, but using unsigned integers.
+	 *
+	 *                   dl_runtime   rt_runtime
+	 * actual_runtime =  ---------- * ---------- * period
+	 *                     period       period
+	 */
+	if (dl_runtime == RUNTIME_INF)
+		return RUNTIME_INF;
+
+	return div64_u64 (dl_runtime * rt_runtime, period);
+}
+
+static int check_dl_bw(void)
+{
+	int i;
+	u64 period = global_rt_period();
+	u64 dl_actual_runtime = def_dl_bandwidth.dl_runtime;
+	u64 new_bw = to_ratio(period, dl_actual_runtime);
+
+	/*
+	 * Here we want to check the bandwidth not being set to some
+	 * value smaller than the currently allocated bandwidth in
+	 * any of the root_domains.
+	 *
+	 * FIXME: Cycling on all the CPUs is overdoing, but simpler than
+	 * cycling on root_domains... Discussion on different/better
+	 * solutions is welcome!
+	 */
+	for_each_possible_cpu(i) {
+#ifdef CONFIG_SMP
+		struct dl_bw *dl_b = &cpu_rq(i)->rd->dl_bw;
+#else
+		struct dl_bw *dl_b = &cpu_rq(i)->dl.dl_bw;
+#endif
+		raw_spin_lock(&dl_b->lock);
+		if (new_bw < dl_b->total_bw) {
+			raw_spin_unlock(&dl_b->lock);
+			return -EBUSY;
+		}
+		raw_spin_unlock(&dl_b->lock);
+	}
+
+	return 0;
+}
+
+static void update_dl_bw(void)
+{
+	u64 new_bw;
+	int i;
+
+	def_dl_bandwidth.dl_runtime = actual_dl_runtime();
+	if (def_dl_bandwidth.dl_runtime == RUNTIME_INF ||
+	    global_rt_runtime() == RUNTIME_INF)
+		new_bw = -1;
+	else {
+		new_bw = to_ratio(global_rt_period(),
+				  def_dl_bandwidth.dl_runtime);
+	}
+	/*
+	 * FIXME: As above...
+	 */
+	for_each_possible_cpu(i) {
+#ifdef CONFIG_SMP
+		struct dl_bw *dl_b = &cpu_rq(i)->rd->dl_bw;
+#else
+		struct dl_bw *dl_b = &cpu_rq(i)->dl.dl_bw;
+#endif
+
+		raw_spin_lock(&dl_b->lock);
+		dl_b->bw = new_bw;
+		raw_spin_unlock(&dl_b->lock);
+	}
+}
+
 #ifdef CONFIG_RT_GROUP_SCHED
 /*
  * Ensure that the real time constraints are schedulable.
@@ -7437,48 +7524,10 @@ static long sched_group_rt_period(struct task_group *tg)
 	do_div(rt_period_us, NSEC_PER_USEC);
 	return rt_period_us;
 }
-#endif /* CONFIG_RT_GROUP_SCHED */
 
-/*
- * Coupling of -rt and -deadline bandwidth.
- *
- * Here we check if the new -rt bandwidth value is consistent
- * with the system settings for the bandwidth available
- * to -deadline tasks.
- *
- * IOW, we want to enforce that
- *
- *   rt_bandwidth + dl_bandwidth <= 100%
- *
- * is always true.
- */
-static bool __sched_rt_dl_global_constraints(u64 rt_bw)
-{
-	unsigned long flags;
-	u64 dl_bw;
-	bool ret;
-
-	raw_spin_lock_irqsave(&def_dl_bandwidth.dl_runtime_lock, flags);
-	if (global_rt_runtime() == RUNTIME_INF ||
-	    global_dl_runtime() == RUNTIME_INF) {
-		ret = true;
-		goto unlock;
-	}
-
-	dl_bw = to_ratio(def_dl_bandwidth.dl_period,
-			 def_dl_bandwidth.dl_runtime);
-
-	ret = rt_bw + dl_bw <= to_ratio(RUNTIME_INF, RUNTIME_INF);
-unlock:
-	raw_spin_unlock_irqrestore(&def_dl_bandwidth.dl_runtime_lock, flags);
-
-	return ret;
-}
-
-#ifdef CONFIG_RT_GROUP_SCHED
 static int sched_rt_global_constraints(void)
 {
-	u64 runtime, period, bw;
+	u64 runtime, period;
 	int ret = 0;
 
 	if (sysctl_sched_rt_period <= 0)
@@ -7493,9 +7542,13 @@ static int sched_rt_global_constraints(void)
 	if (runtime > period && runtime != RUNTIME_INF)
 		return -EINVAL;
 
-	bw = to_ratio(period, runtime);
-	if (!__sched_rt_dl_global_constraints(bw))
-		return -EINVAL;
+	/*
+	 * Check if changing rt_bw could have negative effects
+	 * on dl_bw
+	 */
+	ret = check_dl_bw();
+	if (ret)
+		return ret;
 
 	mutex_lock(&rt_constraints_mutex);
 	read_lock(&tasklist_lock);
@@ -7519,18 +7572,27 @@ static int sched_rt_can_attach(struct task_group *tg, struct task_struct *tsk)
 static int sched_rt_global_constraints(void)
 {
 	unsigned long flags;
-	int i, ret = 0;
-	u64 bw;
+	int i, ret;
 
 	if (sysctl_sched_rt_period <= 0)
 		return -EINVAL;
 
+	/*
+	 * There's always some RT tasks in the root group
+	 * -- migration, kstopmachine etc..
+	 */
+	if (sysctl_sched_rt_runtime == 0)
+		return -EBUSY;
+
+	/*
+	 * Check if changing rt_bw could have negative effects
+	 * on dl_bw
+	 */
+	ret = check_dl_bw();
+	if (ret)
+		return ret;
+
 	raw_spin_lock_irqsave(&def_rt_bandwidth.rt_runtime_lock, flags);
-	bw = to_ratio(global_rt_period(), global_rt_runtime());
-	if (!__sched_rt_dl_global_constraints(bw)) {
-		ret = -EINVAL;
-		goto unlock;
-	}
 
 	for_each_possible_cpu(i) {
 		struct rt_rq *rt_rq = &cpu_rq(i)->rt;
@@ -7539,48 +7601,12 @@ static int sched_rt_global_constraints(void)
 		rt_rq->rt_runtime = global_rt_runtime();
 		raw_spin_unlock(&rt_rq->rt_runtime_lock);
 	}
-unlock:
 	raw_spin_unlock_irqrestore(&def_rt_bandwidth.rt_runtime_lock, flags);
 
-	return ret;
+	return 0;
 }
 #endif /* CONFIG_RT_GROUP_SCHED */
 
-/*
- * Coupling of -dl and -rt bandwidth.
- *
- * Here we check, while setting the system wide bandwidth available
- * for -dl tasks and groups, if the new values are consistent with
- * the system settings for the bandwidth available to -rt entities.
- *
- * IOW, we want to enforce that
- *
- *   rt_bandwidth + dl_bandwidth <= 100%
- *
- * is always true.
- */
-static bool __sched_dl_rt_global_constraints(u64 dl_bw)
-{
-	u64 rt_bw;
-	bool ret;
-
-	raw_spin_lock(&def_rt_bandwidth.rt_runtime_lock);
-	if (global_dl_runtime() == RUNTIME_INF ||
-	    global_rt_runtime() == RUNTIME_INF) {
-		ret = true;
-		goto unlock;
-	}
-
-	rt_bw = to_ratio(ktime_to_ns(def_rt_bandwidth.rt_period),
-			 def_rt_bandwidth.rt_runtime);
-
-	ret = rt_bw + dl_bw <= to_ratio(RUNTIME_INF, RUNTIME_INF);
-unlock:
-	raw_spin_unlock(&def_rt_bandwidth.rt_runtime_lock);
-
-	return ret;
-}
-
 static bool __sched_dl_global_constraints(u64 runtime, u64 period)
 {
 	if (!period || (runtime != RUNTIME_INF && runtime > period))
@@ -7591,40 +7617,17 @@ static bool __sched_dl_global_constraints(u64 runtime, u64 period)
 
 static int sched_dl_global_constraints(void)
 {
-	u64 runtime = global_dl_runtime();
-	u64 period = global_dl_period();
-	u64 new_bw = to_ratio(period, runtime);
-	int ret, i;
+	u64 period = global_rt_period();
+	u64 dl_actual_runtime = def_dl_bandwidth.dl_runtime;
+	int ret;
 
-	ret = __sched_dl_global_constraints(runtime, period);
+	ret = __sched_dl_global_constraints(dl_actual_runtime, period);
 	if (ret)
 		return ret;
 
-	if (!__sched_dl_rt_global_constraints(new_bw))
-		return -EINVAL;
-
-	/*
-	 * Here we want to check the bandwidth not being set to some
-	 * value smaller than the currently allocated bandwidth in
-	 * any of the root_domains.
-	 *
-	 * FIXME: Cycling on all the CPUs is overdoing, but simpler than
-	 * cycling on root_domains... Discussion on different/better
-	 * solutions is welcome!
-	 */
-	for_each_possible_cpu(i) {
-#ifdef CONFIG_SMP
-		struct dl_bw *dl_b = &cpu_rq(i)->rd->dl_bw;
-#else
-		struct dl_bw *dl_b = &cpu_rq(i)->dl.dl_bw;
-#endif
-		raw_spin_lock(&dl_b->lock);
-		if (new_bw < dl_b->total_bw) {
-			raw_spin_unlock(&dl_b->lock);
-			return -EBUSY;
-		}
-		raw_spin_unlock(&dl_b->lock);
-	}
+	ret = check_dl_bw();
+	if (ret)
+		return ret;
 
 	return 0;
 }
@@ -7655,6 +7658,7 @@ int sched_rt_handler(struct ctl_table *table, int write,
 	int ret;
 	int old_period, old_runtime;
 	static DEFINE_MUTEX(mutex);
+	unsigned long flags;
 
 	mutex_lock(&mutex);
 	old_period = sysctl_sched_rt_period;
@@ -7664,6 +7668,8 @@ int sched_rt_handler(struct ctl_table *table, int write,
 
 	if (!ret && write) {
 		ret = sched_rt_global_constraints();
+		raw_spin_lock_irqsave(&def_dl_bandwidth.dl_runtime_lock,
+				      flags);
 		if (ret) {
 			sysctl_sched_rt_period = old_period;
 			sysctl_sched_rt_runtime = old_runtime;
@@ -7671,7 +7677,11 @@ int sched_rt_handler(struct ctl_table *table, int write,
 			def_rt_bandwidth.rt_runtime = global_rt_runtime();
 			def_rt_bandwidth.rt_period =
 				ns_to_ktime(global_rt_period());
+
+			update_dl_bw();
 		}
+		raw_spin_unlock_irqrestore(&def_dl_bandwidth.dl_runtime_lock,
+					   flags);
 	}
 	mutex_unlock(&mutex);
 
@@ -7683,12 +7693,11 @@ int sched_dl_handler(struct ctl_table *table, int write,
 		loff_t *ppos)
 {
 	int ret;
-	int old_period, old_runtime;
+	int old_runtime;
 	static DEFINE_MUTEX(mutex);
 	unsigned long flags;
 
 	mutex_lock(&mutex);
-	old_period = sysctl_sched_dl_period;
 	old_runtime = sysctl_sched_dl_runtime;
 
 	ret = proc_dointvec(table, write, buffer, lenp, ppos);
@@ -7699,33 +7708,9 @@ int sched_dl_handler(struct ctl_table *table, int write,
 
 		ret = sched_dl_global_constraints();
 		if (ret) {
-			sysctl_sched_dl_period = old_period;
 			sysctl_sched_dl_runtime = old_runtime;
 		} else {
-			u64 new_bw;
-			int i;
-
-			def_dl_bandwidth.dl_period = global_dl_period();
-			def_dl_bandwidth.dl_runtime = global_dl_runtime();
-			if (global_dl_runtime() == RUNTIME_INF)
-				new_bw = -1;
-			else
-				new_bw = to_ratio(global_dl_period(),
-						  global_dl_runtime());
-			/*
-			 * FIXME: As above...
-			 */
-			for_each_possible_cpu(i) {
-#ifdef CONFIG_SMP
-				struct dl_bw *dl_b = &cpu_rq(i)->rd->dl_bw;
-#else
-				struct dl_bw *dl_b = &cpu_rq(i)->dl.dl_bw;
-#endif
-
-				raw_spin_lock(&dl_b->lock);
-				dl_b->bw = new_bw;
-				raw_spin_unlock(&dl_b->lock);
-			}
+			update_dl_bw();
 		}
 
 		raw_spin_unlock_irqrestore(&def_dl_bandwidth.dl_runtime_lock,
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 35d7c2d..ca20110 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -48,10 +48,9 @@ static inline int is_leftmost(struct task_struct *p, struct dl_rq *dl_rq)
 	return dl_rq->rb_leftmost == &dl_se->rb_node;
 }
 
-void init_dl_bandwidth(struct dl_bandwidth *dl_b, u64 period, u64 runtime)
+void init_dl_bandwidth(struct dl_bandwidth *dl_b, u64 runtime)
 {
 	raw_spin_lock_init(&dl_b->dl_runtime_lock);
-	dl_b->dl_period = period;
 	dl_b->dl_runtime = runtime;
 }
 
@@ -64,7 +63,7 @@ void init_dl_bw(struct dl_bw *dl_b)
 	if (global_dl_runtime() == RUNTIME_INF)
 		dl_b->bw = -1;
 	else
-		dl_b->bw = to_ratio(global_dl_period(), global_dl_runtime());
+		dl_b->bw = to_ratio(global_rt_period(), global_dl_runtime());
 	raw_spin_unlock(&def_dl_bandwidth.dl_runtime_lock);
 	dl_b->total_bw = 0;
 }
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 08931a6..bf4acf8 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -142,20 +142,20 @@ struct rt_bandwidth {
 	struct hrtimer		rt_period_timer;
 };
 /*
- * To keep the bandwidth of -deadline tasks and groups under control
- * we need some place where:
- *  - store the maximum -deadline bandwidth of the system (the group);
+ * To keep the bandwidth of -deadline tasks under control we need some
+ * place where:
+ *  - store the maximum -deadline bandwidth of the system;
  *  - cache the fraction of that bandwidth that is currently allocated.
  *
  * This is all done in the data structure below. It is similar to the
  * one used for RT-throttling (rt_bandwidth), with the main difference
  * that, since here we are only interested in admission control, we
- * do not decrease any runtime while the group "executes", neither we
+ * do not decrease any runtime while the task "executes", neither we
  * need a timer to replenish it.
  *
  * With respect to SMP, the bandwidth is given on a per-CPU basis,
  * meaning that:
- *  - dl_bw (< 100%) is the bandwidth of the system (group) on each CPU;
+ *  - dl_bw (< 100%) is the bandwidth of the system on each CPU;
  *  - dl_total_bw array contains, in the i-eth element, the currently
  *    allocated bandwidth on the i-eth CPU.
  * Moreover, groups consume bandwidth on each CPU, while tasks only
@@ -168,7 +168,6 @@ struct rt_bandwidth {
 struct dl_bandwidth {
 	raw_spinlock_t dl_runtime_lock;
 	u64 dl_runtime;
-	u64 dl_period;
 };
 
 static inline int dl_bandwidth_enabled(void)
@@ -178,10 +177,12 @@ static inline int dl_bandwidth_enabled(void)
 
 struct dl_bw {
 	raw_spinlock_t lock;
-	u64 bw, total_bw;
+	/* default value */
+	u64 bw;
+	/* allocated */
+	u64 total_bw;
 };
 
-static inline u64 global_dl_period(void);
 static inline u64 global_dl_runtime(void);
 
 extern struct mutex sched_domains_mutex;
@@ -924,11 +925,6 @@ static inline u64 global_rt_runtime(void)
 	return (u64)sysctl_sched_rt_runtime * NSEC_PER_USEC;
 }
 
-static inline u64 global_dl_period(void)
-{
-	return (u64)sysctl_sched_dl_period * NSEC_PER_USEC;
-}
-
 static inline u64 global_dl_runtime(void)
 {
 	if (sysctl_sched_dl_runtime < 0)
@@ -1192,7 +1188,7 @@ extern struct rt_bandwidth def_rt_bandwidth;
 extern void init_rt_bandwidth(struct rt_bandwidth *rt_b, u64 period, u64 runtime);
 
 extern struct dl_bandwidth def_dl_bandwidth;
-extern void init_dl_bandwidth(struct dl_bandwidth *dl_b, u64 period, u64 runtime);
+extern void init_dl_bandwidth(struct dl_bandwidth *dl_b, u64 runtime);
 extern void init_dl_task_timer(struct sched_dl_entity *dl_se);
 
 unsigned long to_ratio(u64 period, u64 runtime);
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index f0cf6d6..8159e7e 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -415,13 +415,6 @@ static struct ctl_table kern_table[] = {
 		.proc_handler	= sched_rr_handler,
 	},
 	{
-		.procname	= "sched_dl_period_us",
-		.data		= &sysctl_sched_dl_period,
-		.maxlen		= sizeof(unsigned int),
-		.mode		= 0644,
-		.proc_handler	= sched_dl_handler,
-	},
-	{
 		.procname	= "sched_dl_runtime_us",
 		.data		= &sysctl_sched_dl_runtime,
 		.maxlen		= sizeof(int),
-- 
1.7.9.5

[PATCH 13/14] sched: speed up -dl pushes with a push-heap.

[Juri Lelli]

Data from tests confirmed that the original active load balancing
logic didn't scale neither in the number of CPU nor in the number of
tasks (as sched_rt does).

Here we provide a global data structure to keep track of deadlines
of the running tasks in the system. The structure is composed by
a bitmask showing the free CPUs and a max-heap, needed when the system
is heavily loaded.

The implementation and concurrent access scheme are kept simple by
design. However, our measurements show that we can compete with sched_rt
on large multi-CPUs machines [1].

Only the push path is addressed, the extension to use this structure
also for pull decisions is straightforward. However, we are currently
evaluating different (in order to decrease/avoid contention) data
structures to solve possibly both problems. We are also going to re-run
tests considering recent changes inside cpupri [2].

[1] http://retis.sssup.it/~jlelli/papers/Ospert11Lelli.pdf
[2] http://www.spinics.net/lists/linux-rt-users/msg06778.html

Signed-off-by: Juri Lelli <juri.lelli@gmail.com>
---
 kernel/sched/Makefile      |    2 +-
 kernel/sched/core.c        |    3 +
 kernel/sched/cpudeadline.c |  216 ++++++++++++++++++++++++++++++++++++++++++++
 kernel/sched/cpudeadline.h |   33 +++++++
 kernel/sched/deadline.c    |   53 +++--------
 kernel/sched/sched.h       |    2 +
 6 files changed, 269 insertions(+), 40 deletions(-)
 create mode 100644 kernel/sched/cpudeadline.c
 create mode 100644 kernel/sched/cpudeadline.h

diff --git a/kernel/sched/Makefile b/kernel/sched/Makefile
index d77282f..ba43447 100644
--- a/kernel/sched/Makefile
+++ b/kernel/sched/Makefile
@@ -12,7 +12,7 @@ CFLAGS_core.o := $(PROFILING) -fno-omit-frame-pointer
 endif
 
 obj-y += core.o proc.o clock.o cputime.o idle_task.o fair.o rt.o deadline.o stop_task.o
-obj-$(CONFIG_SMP) += cpupri.o
+obj-$(CONFIG_SMP) += cpupri.o cpudeadline.o
 obj-$(CONFIG_SCHED_AUTOGROUP) += auto_group.o
 obj-$(CONFIG_SCHEDSTATS) += stats.o
 obj-$(CONFIG_SCHED_DEBUG) += debug.o
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index ddc1f49..49aa0ff 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5385,6 +5385,7 @@ static void free_rootdomain(struct rcu_head *rcu)
 	struct root_domain *rd = container_of(rcu, struct root_domain, rcu);
 
 	cpupri_cleanup(&rd->cpupri);
+	cpudl_cleanup(&rd->cpudl);
 	free_cpumask_var(rd->dlo_mask);
 	free_cpumask_var(rd->rto_mask);
 	free_cpumask_var(rd->online);
@@ -5443,6 +5444,8 @@ static int init_rootdomain(struct root_domain *rd)
 		goto free_dlo_mask;
 
 	init_dl_bw(&rd->dl_bw);
+	if (cpudl_init(&rd->cpudl) != 0)
+		goto free_dlo_mask;
 
 	if (cpupri_init(&rd->cpupri) != 0)
 		goto free_rto_mask;
diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c
new file mode 100644
index 0000000..13a31a9
--- /dev/null
+++ b/kernel/sched/cpudeadline.c
@@ -0,0 +1,216 @@
+/*
+ *  kernel/sched/cpudl.c
+ *
+ *  Global CPU deadline management
+ *
+ *  Author: Juri Lelli <j.lelli@sssup.it>
+ *
+ *  This program is free software; you can redistribute it and/or
+ *  modify it under the terms of the GNU General Public License
+ *  as published by the Free Software Foundation; version 2
+ *  of the License.
+ */
+
+#include <linux/gfp.h>
+#include <linux/kernel.h>
+#include "cpudeadline.h"
+
+static inline int parent(int i)
+{
+	return (i - 1) >> 1;
+}
+
+static inline int left_child(int i)
+{
+	return (i << 1) + 1;
+}
+
+static inline int right_child(int i)
+{
+	return (i << 1) + 2;
+}
+
+static inline int dl_time_before(u64 a, u64 b)
+{
+	return (s64)(a - b) < 0;
+}
+
+void cpudl_exchange(struct cpudl *cp, int a, int b)
+{
+	int cpu_a = cp->elements[a].cpu, cpu_b = cp->elements[b].cpu;
+
+	swap(cp->elements[a], cp->elements[b]);
+	swap(cp->cpu_to_idx[cpu_a], cp->cpu_to_idx[cpu_b]);
+}
+
+void cpudl_heapify(struct cpudl *cp, int idx)
+{
+	int l, r, largest;
+
+	/* adapted from lib/prio_heap.c */
+	while(1) {
+		l = left_child(idx);
+		r = right_child(idx);
+		largest = idx;
+
+		if ((l < cp->size) && dl_time_before(cp->elements[idx].dl,
+							cp->elements[l].dl))
+			largest = l;
+		if ((r < cp->size) && dl_time_before(cp->elements[largest].dl,
+							cp->elements[r].dl))
+			largest = r;
+		if (largest == idx)
+			break;
+
+		/* Push idx down the heap one level and bump one up */
+		cpudl_exchange(cp, largest, idx);
+		idx = largest;
+	}
+}
+
+void cpudl_change_key(struct cpudl *cp, int idx, u64 new_dl)
+{
+	WARN_ON(idx > num_present_cpus() || idx == IDX_INVALID);
+
+	if (dl_time_before(new_dl, cp->elements[idx].dl)) {
+		cp->elements[idx].dl = new_dl;
+		cpudl_heapify(cp, idx);
+	} else {
+		cp->elements[idx].dl = new_dl;
+		while (idx > 0 && dl_time_before(cp->elements[parent(idx)].dl,
+					cp->elements[idx].dl)) {
+			cpudl_exchange(cp, idx, parent(idx));
+			idx = parent(idx);
+		}
+	}
+}
+
+static inline int cpudl_maximum(struct cpudl *cp)
+{
+	return cp->elements[0].cpu;
+}
+
+/*
+ * cpudl_find - find the best (later-dl) CPU in the system
+ * @cp: the cpudl max-heap context
+ * @p: the task
+ * @later_mask: a mask to fill in with the selected CPUs (or NULL)
+ *
+ * Returns: int - best CPU (heap maximum if suitable)
+ */
+int cpudl_find(struct cpudl *cp, struct task_struct *p,
+	       struct cpumask *later_mask)
+{
+	int best_cpu = -1;
+	const struct sched_dl_entity *dl_se = &p->dl;
+
+	if (later_mask && cpumask_and(later_mask, cp->free_cpus,
+			&p->cpus_allowed) && cpumask_and(later_mask,
+			later_mask, cpu_active_mask)) {
+		best_cpu = cpumask_any(later_mask);
+		goto out;
+	} else if (cpumask_test_cpu(cpudl_maximum(cp), &p->cpus_allowed) &&
+			dl_time_before(dl_se->deadline, cp->elements[0].dl)) {
+		best_cpu = cpudl_maximum(cp);
+		if (later_mask)
+			cpumask_set_cpu(best_cpu, later_mask);
+	}
+
+out:
+	WARN_ON(best_cpu > num_present_cpus() && best_cpu != -1);
+
+	return best_cpu;
+}
+
+/*
+ * cpudl_set - update the cpudl max-heap
+ * @cp: the cpudl max-heap context
+ * @cpu: the target cpu
+ * @dl: the new earliest deadline for this cpu
+ *
+ * Notes: assumes cpu_rq(cpu)->lock is locked
+ *
+ * Returns: (void)
+ */
+void cpudl_set(struct cpudl *cp, int cpu, u64 dl, int is_valid)
+{
+	int old_idx, new_cpu;
+	unsigned long flags;
+
+	WARN_ON(cpu > num_present_cpus());
+
+	raw_spin_lock_irqsave(&cp->lock, flags);
+	old_idx = cp->cpu_to_idx[cpu];
+	if (!is_valid) {
+		/* remove item */
+		if (old_idx == IDX_INVALID) {
+			/* 
+			 * Nothing to remove if old_idx was invalid.
+			 * This could happen if a rq_offline_dl is
+			 * called for a CPU without -dl tasks running.
+			 */
+			goto out;
+		}
+		new_cpu = cp->elements[cp->size - 1].cpu;
+		cp->elements[old_idx].dl = cp->elements[cp->size - 1].dl;
+		cp->elements[old_idx].cpu = new_cpu;
+		cp->size--;
+		cp->cpu_to_idx[new_cpu] = old_idx;
+		cp->cpu_to_idx[cpu] = IDX_INVALID;
+		while (old_idx > 0 && dl_time_before(
+				cp->elements[parent(old_idx)].dl,
+				cp->elements[old_idx].dl)) {
+			cpudl_exchange(cp, old_idx, parent(old_idx));
+			old_idx = parent(old_idx);
+		}
+		cpumask_set_cpu(cpu, cp->free_cpus);
+                cpudl_heapify(cp, old_idx);
+
+		goto out;
+	}
+
+	if (old_idx == IDX_INVALID) {
+		cp->size++;
+		cp->elements[cp->size - 1].dl = 0;
+		cp->elements[cp->size - 1].cpu = cpu;
+		cp->cpu_to_idx[cpu] = cp->size - 1;
+		cpudl_change_key(cp, cp->size - 1, dl);
+		cpumask_clear_cpu(cpu, cp->free_cpus);
+	} else {
+		cpudl_change_key(cp, old_idx, dl);
+	}
+
+out:
+	raw_spin_unlock_irqrestore(&cp->lock, flags);
+}
+
+/*
+ * cpudl_init - initialize the cpudl structure
+ * @cp: the cpudl max-heap context
+ */
+int cpudl_init(struct cpudl *cp)
+{
+	int i;
+
+	memset(cp, 0, sizeof(*cp));
+	raw_spin_lock_init(&cp->lock);
+	cp->size = 0;
+	for (i = 0; i < NR_CPUS; i++)
+		cp->cpu_to_idx[i] = IDX_INVALID;
+	if (!alloc_cpumask_var(&cp->free_cpus, GFP_KERNEL))
+		return -ENOMEM;
+	cpumask_setall(cp->free_cpus);
+
+	return 0;
+}
+
+/*
+ * cpudl_cleanup - clean up the cpudl structure
+ * @cp: the cpudl max-heap context
+ */
+void cpudl_cleanup(struct cpudl *cp)
+{
+	/*
+	 * nothing to do for the moment
+	 */
+}
diff --git a/kernel/sched/cpudeadline.h b/kernel/sched/cpudeadline.h
new file mode 100644
index 0000000..a202789
--- /dev/null
+++ b/kernel/sched/cpudeadline.h
@@ -0,0 +1,33 @@
+#ifndef _LINUX_CPUDL_H
+#define _LINUX_CPUDL_H
+
+#include <linux/sched.h>
+
+#define IDX_INVALID     -1
+
+struct array_item {
+	u64 dl;
+	int cpu;
+};
+
+struct cpudl {
+	raw_spinlock_t lock;
+	int size;
+	int cpu_to_idx[NR_CPUS];
+	struct array_item elements[NR_CPUS];
+	cpumask_var_t free_cpus;
+};
+
+
+#ifdef CONFIG_SMP
+int cpudl_find(struct cpudl *cp, struct task_struct *p,
+	       struct cpumask *later_mask);
+void cpudl_set(struct cpudl *cp, int cpu, u64 dl, int is_valid);
+int cpudl_init(struct cpudl *cp);
+void cpudl_cleanup(struct cpudl *cp);
+#else
+#define cpudl_set(cp, cpu, dl) do { } while (0)
+#define cpudl_init() do { } while (0)
+#endif /* CONFIG_SMP */
+
+#endif /* _LINUX_CPUDL_H */
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index ca20110..1499381 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -16,6 +16,8 @@
  */
 #include "sched.h"
 
+#include <linux/slab.h>
+
 struct dl_bandwidth def_dl_bandwidth;
 
 static inline struct task_struct *dl_task_of(struct sched_dl_entity *dl_se)
@@ -652,6 +654,7 @@ static void inc_dl_deadline(struct dl_rq *dl_rq, u64 deadline)
 		 */
 		dl_rq->earliest_dl.next = dl_rq->earliest_dl.curr;
 		dl_rq->earliest_dl.curr = deadline;
+		cpudl_set(&rq->rd->cpudl, rq->cpu, deadline, 1);
 	} else if (dl_rq->earliest_dl.next == 0 ||
 		   dl_time_before(deadline, dl_rq->earliest_dl.next)) {
 		/*
@@ -675,6 +678,7 @@ static void dec_dl_deadline(struct dl_rq *dl_rq, u64 deadline)
 	if (!dl_rq->dl_nr_running) {
 		dl_rq->earliest_dl.curr = 0;
 		dl_rq->earliest_dl.next = 0;
+		cpudl_set(&rq->rd->cpudl, rq->cpu, 0, 0);
 	} else {
 		struct rb_node *leftmost = dl_rq->rb_leftmost;
 		struct sched_dl_entity *entry;
@@ -682,6 +686,7 @@ static void dec_dl_deadline(struct dl_rq *dl_rq, u64 deadline)
 		entry = rb_entry(leftmost, struct sched_dl_entity, rb_node);
 		dl_rq->earliest_dl.curr = entry->deadline;
 		dl_rq->earliest_dl.next = next_deadline(rq);
+		cpudl_set(&rq->rd->cpudl, rq->cpu, entry->deadline, 1);
 	}
 }
 
@@ -863,9 +868,6 @@ static void yield_task_dl(struct rq *rq)
 #ifdef CONFIG_SMP
 
 static int find_later_rq(struct task_struct *task);
-static int latest_cpu_find(struct cpumask *span,
-			   struct task_struct *task,
-			   struct cpumask *later_mask);
 
 static int
 select_task_rq_dl(struct task_struct *p, int sd_flag, int flags)
@@ -915,7 +917,7 @@ static void check_preempt_equal_dl(struct rq *rq, struct task_struct *p)
 	 * let's hope p can move out.
 	 */
 	if (rq->curr->nr_cpus_allowed == 1 ||
-	    latest_cpu_find(rq->rd->span, rq->curr, NULL) == -1)
+	    cpudl_find(&rq->rd->cpudl, rq->curr, NULL) == -1)
 		return;
 
 	/*
@@ -923,7 +925,7 @@ static void check_preempt_equal_dl(struct rq *rq, struct task_struct *p)
 	 * see if it is pushed or pulled somewhere else.
 	 */
 	if (p->nr_cpus_allowed != 1 &&
-	    latest_cpu_find(rq->rd->span, p, NULL) != -1)
+	    cpudl_find(&rq->rd->cpudl, p, NULL) != -1)
 		return;
 
 	resched_task(rq->curr);
@@ -1116,39 +1118,6 @@ next_node:
 	return NULL;
 }
 
-static int latest_cpu_find(struct cpumask *span,
-			   struct task_struct *task,
-			   struct cpumask *later_mask)
-{
-	const struct sched_dl_entity *dl_se = &task->dl;
-	int cpu, found = -1, best = 0;
-	u64 max_dl = 0;
-
-	for_each_cpu(cpu, span) {
-		struct rq *rq = cpu_rq(cpu);
-		struct dl_rq *dl_rq = &rq->dl;
-
-		if (cpumask_test_cpu(cpu, &task->cpus_allowed) &&
-		    (!dl_rq->dl_nr_running || dl_time_before(dl_se->deadline,
-		     dl_rq->earliest_dl.curr))) {
-			if (later_mask)
-				cpumask_set_cpu(cpu, later_mask);
-			if (!best && !dl_rq->dl_nr_running) {
-				best = 1;
-				found = cpu;
-			} else if (!best &&
-				   dl_time_before(max_dl,
-						  dl_rq->earliest_dl.curr)) {
-				max_dl = dl_rq->earliest_dl.curr;
-				found = cpu;
-			}
-		} else if (later_mask)
-			cpumask_clear_cpu(cpu, later_mask);
-	}
-
-	return found;
-}
-
 static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask_dl);
 
 static int find_later_rq(struct task_struct *task)
@@ -1165,7 +1134,8 @@ static int find_later_rq(struct task_struct *task)
 	if (task->nr_cpus_allowed == 1)
 		return -1;
 
-	best_cpu = latest_cpu_find(task_rq(task)->rd->span, task, later_mask);
+	best_cpu = cpudl_find(&task_rq(task)->rd->cpudl,
+			task, later_mask);
 	if (best_cpu == -1)
 		return -1;
 
@@ -1535,6 +1505,9 @@ static void rq_online_dl(struct rq *rq)
 {
 	if (rq->dl.overloaded)
 		dl_set_overload(rq);
+
+	if (rq->dl.dl_nr_running > 0)
+		cpudl_set(&rq->rd->cpudl, rq->cpu, rq->dl.earliest_dl.curr, 1);
 }
 
 /* Assumes rq->lock is held */
@@ -1542,6 +1515,8 @@ static void rq_offline_dl(struct rq *rq)
 {
 	if (rq->dl.overloaded)
 		dl_clear_overload(rq);
+
+	cpudl_set(&rq->rd->cpudl, rq->cpu, 0, 0);
 }
 
 void init_sched_dl_class(void)
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index bf4acf8..596e290 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -9,6 +9,7 @@
 #include <linux/tick.h>
 
 #include "cpupri.h"
+#include "cpudeadline.h"
 #include "cpuacct.h"
 
 struct rq;
@@ -507,6 +508,7 @@ struct root_domain {
 	cpumask_var_t dlo_mask;
 	atomic_t dlo_count;
 	struct dl_bw dl_bw;
+	struct cpudl cpudl;
 
 	/*
 	 * The "RT overload" flag: it gets set if a CPU has more than
-- 
1.7.9.5

[PATCH 14/14] sched: add sched_dl documentation.

[Juri Lelli]

From: Dario Faggioli <raistlin@linux.it>

Add in Documentation/scheduler/ some hints about the design
choices, the usage and the future possible developments of the
sched_dl scheduling class and of the SCHED_DEADLINE policy.

Signed-off-by: Dario Faggioli <raistlin@linux.it>
Signed-off-by: Juri Lelli <juri.lelli@gmail.com>
---
 Documentation/scheduler/sched-deadline.txt |  196 ++++++++++++++++++++++++++++
 kernel/sched/deadline.c                    |    3 +-
 2 files changed, 198 insertions(+), 1 deletion(-)
 create mode 100644 Documentation/scheduler/sched-deadline.txt

diff --git a/Documentation/scheduler/sched-deadline.txt b/Documentation/scheduler/sched-deadline.txt
new file mode 100644
index 0000000..4d1ed52
--- /dev/null
+++ b/Documentation/scheduler/sched-deadline.txt
@@ -0,0 +1,196 @@
+			  Deadline Task Scheduling
+			  ------------------------
+
+CONTENTS
+========
+
+0. WARNING
+1. Overview
+2. Task scheduling
+2. The Interface
+3. Bandwidth management
+  3.1 System-wide settings
+  3.2 Task interface
+  3.4 Default behavior
+4. Tasks CPU affinity
+  4.1 SCHED_DEADLINE and cpusets HOWTO
+5. Future plans
+
+
+0. WARNING
+==========
+
+ Fiddling with these settings can result in an unpredictable or even unstable
+ system behavior. As for -rt (group) scheduling, it is assumed that root users
+ know what they're doing.
+
+
+1. Overview
+===========
+
+ The SCHED_DEADLINE policy contained inside the sched_dl scheduling class is
+ basically an implementation of the Earliest Deadline First (EDF) scheduling
+ algorithm, augmented with a mechanism (called Constant Bandwidth Server, CBS)
+ that makes it possible to isolate the behavior of tasks between each other.
+
+
+2. Task scheduling
+==================
+
+ The typical -deadline task is composed of a computation phase (instance)
+ which is activated on a periodic or sporadic fashion. The expected (maximum)
+ duration of such computation is called the task's runtime; the time interval
+ by which each instance needs to be completed is called the task's relative
+ deadline. The task's absolute deadline is dynamically calculated as the
+ time instant a task (or, more properly) activates plus the relative
+ deadline.
+
+ The EDF[1] algorithm selects the task with the smallest absolute deadline as
+ the one to be executed first, while the CBS[2,3] ensures that each task runs
+ for at most its runtime every period, avoiding any interference between
+ different tasks (bandwidth isolation).
+ Thanks to this feature, also tasks that do not strictly comply with the
+ computational model described above can effectively use the new policy.
+ IOW, there are no limitations on what kind of task can exploit this new
+ scheduling discipline, even if it must be said that it is particularly
+ suited for periodic or sporadic tasks that need guarantees on their
+ timing behavior, e.g., multimedia, streaming, control applications, etc.
+
+ References:
+  1 - C. L. Liu and J. W. Layland. Scheduling algorithms for multiprogram-
+      ming in a hard-real-time environment. Journal of the Association for
+      Computing Machinery, 20(1), 1973.
+  2 - L. Abeni , G. Buttazzo. Integrating Multimedia Applications in Hard
+      Real-Time Systems. Proceedings of the 19th IEEE Real-time Systems
+      Symposium, 1998. http://retis.sssup.it/~giorgio/paps/1998/rtss98-cbs.pdf
+  3 - L. Abeni. Server Mechanisms for Multimedia Applications. ReTiS Lab
+      Technical Report. http://xoomer.virgilio.it/lucabe72/pubs/tr-98-01.ps
+
+3. Bandwidth management
+=======================
+
+ In order for the -deadline scheduling to be effective and useful, it is
+ important to have some method to keep the allocation of the available CPU
+ bandwidth to the tasks under control.
+ This is usually called "admission control" and if it is not performed at all,
+ no guarantee can be given on the actual scheduling of the -deadline tasks.
+
+ Since when RT-throttling has been introduced each task group has a bandwidth
+ associated, calculated as a certain amount of runtime over a period.
+ Moreover, to make it possible to manipulate such bandwidth, readable/writable
+ controls have been added to both procfs (for system wide settings) and cgroupfs
+ (for per-group settings).
+ Therefore, the same interface is being used for controlling the bandwidth
+ distrubution to -deadline tasks and task groups, i.e., new controls but with
+ similar names, equivalent meaning and with the same usage paradigm are added.
+
+ However, more discussion is needed in order to figure out how we want to manage
+ SCHED_DEADLINE bandwidth at the task group level. Therefore, SCHED_DEADLINE
+ uses (for now) a less sophisticated, but actually very sensible, mechanism to
+ ensure that a certain utilization cap is not overcome per each root_domain.
+
+ Another main difference between deadline bandwidth management and RT-throttling
+ is that -deadline tasks have bandwidth on their own (while -rt ones don't!),
+ and thus we don't need an higher level throttling mechanism to enforce the
+ desired bandwidth.
+
+3.1 System wide settings
+------------------------
+
+ The system wide settings are configured under the /proc virtual file system.
+
+ The control knob that is added to the /proc virtual file system is
+ /proc/sys/kernel/sched_dl_runtime_us. It accepts (if written) and provides (if
+ read) the new runtime for each CPU in each root_domain. The period control knob
+ is instead shared with -rt settings (/proc/sys/kernel/sched_rt_period_us). 
+
+ The CPU bandwidth available to -deadline tasks is actually a sub-quota of
+ the -rt bandwidth. By default 95% of system bandwidth is allocate to -rt tasks;
+ among this, a 40% quota is reserved for -dl tasks. To have the actual quota a
+ simple multiplication is needed: .95 * .40 = .38 (38% of system bandwidth for
+ deadline tasks).
+
+ This means that, for a root_domain comprising M CPUs, -deadline tasks
+ can be created until the sum of their bandwidths stay below:
+
+   M * (sched_dl_runtime_us * rt_bw)
+
+ It is also possible to disable this bandwidth management logic, and
+ be thus free of oversubscribing the system up to any arbitrary level.
+ This is done by writing -1 in /proc/sys/kernel/sched_dl_runtime_us or
+ in /proc/sys/kernel/sched_rt_runtime_us.
+
+
+3.2 Task interface
+------------------
+
+ Specifying a periodic/sporadic task that executes for a given amount of
+ runtime at each instance, and that is scheduled according to the urgency of
+ its own timing constraints needs, in general, a way of declaring:
+  - a (maximum/typical) instance execution time,
+  - a minimum interval between consecutive instances,
+  - a time constraint by which each instance must be completed.
+
+ Therefore:
+  * a new struct sched_param2, containing all the necessary fields is
+    provided;
+  * the new scheduling related syscalls that manipulate it, i.e.,
+    sched_setscheduler2(), sched_setparam2() and sched_getparam2()
+    are implemented.
+
+
+3.3 Default behavior
+---------------------
+
+The default value for SCHED_DEADLINE bandwidth is to have dl_runtime equal to
+40000. Being rt_period equal to 1000000, by default, it means that -deadline
+tasks can use at most 40%, multiplied by the number of CPUs that compose the
+root_domain, for each root_domain.
+
+A -deadline task cannot fork.
+
+4. Tasks CPU affinity
+=====================
+
+-deadline tasks cannot have an affinity mask smaller that the entire
+root_domain they are created on. However, affinities can be specified
+through the cpuset facility (Documentation/cgroups/cpusets.txt).
+
+4.1 SCHED_DEADLINE and cpusets HOWTO
+------------------------------------
+
+An example of a simple configuration (pin a -deadline task to CPU0)
+follows (rt-app is used to create a -deadline task).
+
+mkdir /dev/cpuset
+mount -t cgroup -o cpuset cpuset /dev/cpuset
+cd /dev/cpuset
+mkdir cpu0
+echo 0 > cpu0/cpuset.cpus
+echo 0 > cpu0/cpuset.mems
+echo 1 > cpuset.cpu_exclusive
+echo 0 > cpuset.sched_load_balance
+echo 1 > cpu0/cpuset.cpu_exclusive
+echo 1 > cpu0/cpuset.mem_exclusive
+echo $$ > cpu0/tasks
+rt-app -t 100000:10000:d:0 -D5 (it is now actually superfluous to specify
+task affinity)
+
+5. Future plans
+===============
+
+Still missing:
+
+ - refinements to deadline inheritance, especially regarding the possibility
+   of retaining bandwidth isolation among non-interacting tasks. This is
+   being studied from both theoretical and practical point of views, and
+   hopefully we should be able to produce some demonstrative code soon;
+ - (c)group based bandwidth management, and maybe scheduling;
+ - access control for non-root users (and related security concerns to
+   address), which is the best way to allow unprivileged use of the mechanisms
+   and how to prevent non-root users "cheat" the system?
+
+As already discussed, we are planning also to merge this work with the EDF
+throttling patches [https://lkml.org/lkml/2010/2/23/239] but we still are in
+the preliminary phases of the merge and we really seek feedback that would
+help us decide on the direction it should take.
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 1499381..00b550b 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -348,7 +348,8 @@ static void replenish_dl_entity(struct sched_dl_entity *dl_se,
  * disrupting the schedulability of the system. Otherwise, we should
  * refill the runtime and set the deadline a period in the future,
  * because keeping the current (absolute) deadline of the task would
- * result in breaking guarantees promised to other tasks.
+ * result in breaking guarantees promised to other tasks (refer to
+ * Documentation/scheduler/sched-deadline.txt for more informations).
  *
  * This function returns true if:
  *
-- 
1.7.9.5

Re: [PATCH 00/14] sched: SCHED_DEADLINE v8

[Juri Lelli]

Ok,

I forgot a space after the last Cc with git send-mail, sorry about that. Here
the Cc list is right.

Thanks,

- Juri

On 10/14/2013 12:43 PM, Juri Lelli wrote:
> Hello everyone,
> 
> here we go with a new version of the SCHED_DEADLINE patchset (v8). I know that
> it has been a while since I released last version [1], but I thought not to
> spam the mailing list with simple updates. Well... this IS basically an update
> to 3.12-rc5, but it comes right before the next Kernel Summit and Real Time
> Linux Workshop and, since I'll be present at both events, it is probably time
> to fire-up the discussion again.
> 
> Moreover, interesting news:
> 
>  - a better mechanism for coordinating mutually exclusive access to critical
>    sections is coming soon (we wrote a paper about it for RTLWS15 [2]);
>  - the patchset is now available in the 3.4 and 3.10 Yocto kernels [3] (thanks
>    a lot for this to Bruce Ashfield and Insop Song); even though it is hard to
>    say how many new users we got with this, we can say that having
>    SCHED_DEADLINE in Yocto provides availabily to OSVs like Wind River and
>    others;
>  - a european project has started (JUNIPER [4]) for which we will provide
>    kernel level support based on this patchset (and we will soon have a real
>    use case for it! yayyy! :)).
> 
> The development is taking place at:
>    https://github.com/jlelli/sched-deadline
> 
> branch: sched-dl-V8 (this patchset on top of tip/master).
> 
> Check the repositories frequently if you're interested, and feel free to
> e-mail me for any issue you run into.
> 
> Test applications:
>   https://github.com/gbagnoli/rt-app 
>   https://github.com/jlelli/schedtool-dl
> 
> Development mailing list: linux-dl; you can subscribe from here:
> http://feanor.sssup.it/mailman/listinfo/linux-dl
> or via e-mail (send a message to linux-dl-request@retis.sssup.it with
> just the word `help' as subject or in the body to receive info).
> 
> The code was being jointly developed by ReTiS Lab (http://retis.sssup.it)
> and Evidence S.r.l (http://www.evidence.eu.com) in the context of the ACTORS
> EU-funded project (http://www.actors-project.eu) and the S(o)OS EU-funded
> project (http://www.soos-project.eu/). Development is now supported by the
> JUNIPER EU-funded project [4].
> 
> As usual, any kind of feedback is welcome and appreciated.
> 
> Thanks in advice and regards,
> 
>  - Juri
> 
> [1] http://lwn.net/Articles/376502, http://lwn.net/Articles/353797,
>     http://lwn.net/Articles/412410, http://lwn.net/Articles/490944,
>     http://lwn.net/Articles/498472, http://lwn.net/Articles/521091,
>     http://lwn.net/Articles/537388
> 
> [2] https://www.osadl.org/?id=1743
> 
> [3] https://www.yoctoproject.org/
> 
> [4] http://www.juniper-project.org/page/overview
> 
> Dario Faggioli (9):
>   sched: add sched_class->task_dead.
>   sched: add extended scheduling interface.
>   sched: SCHED_DEADLINE structures & implementation.
>   sched: SCHED_DEADLINE avg_update accounting.
>   sched: add schedstats for -deadline tasks.
>   sched: add latency tracing for -deadline tasks.
>   sched: drafted deadline inheritance logic.
>   sched: add bandwidth management for sched_dl.
>   sched: add sched_dl documentation.
> 
> Harald Gustafsson (1):
>   sched: add period support for -deadline tasks.
> 
> Juri Lelli (3):
>   sched: SCHED_DEADLINE SMP-related data structures & logic.
>   sched: make dl_bw a sub-quota of rt_bw
>   sched: speed up -dl pushes with a push-heap.
> 
> Peter Zijlstra (1):
>   rtmutex: turn the plist into an rb-tree.
> 
>  Documentation/scheduler/sched-deadline.txt |  196 ++++
>  arch/arm/include/asm/unistd.h              |    2 +-
>  arch/arm/include/uapi/asm/unistd.h         |    3 +
>  arch/arm/kernel/calls.S                    |    3 +
>  arch/x86/syscalls/syscall_32.tbl           |    3 +
>  arch/x86/syscalls/syscall_64.tbl           |    3 +
>  include/linux/init_task.h                  |   10 +
>  include/linux/rtmutex.h                    |   18 +-
>  include/linux/sched.h                      |  122 +-
>  include/linux/sched/deadline.h             |   24 +
>  include/linux/sched/rt.h                   |    3 +-
>  include/linux/sched/sysctl.h               |   11 +
>  include/linux/syscalls.h                   |    7 +
>  include/uapi/linux/sched.h                 |    1 +
>  kernel/fork.c                              |    8 +-
>  kernel/futex.c                             |    2 +
>  kernel/hrtimer.c                           |    3 +-
>  kernel/rtmutex-debug.c                     |    8 +-
>  kernel/rtmutex.c                           |  164 ++-
>  kernel/rtmutex_common.h                    |   22 +-
>  kernel/sched/Makefile                      |    4 +-
>  kernel/sched/core.c                        |  660 ++++++++++-
>  kernel/sched/cpudeadline.c                 |  216 ++++
>  kernel/sched/cpudeadline.h                 |   33 +
>  kernel/sched/deadline.c                    | 1658 ++++++++++++++++++++++++++++
>  kernel/sched/debug.c                       |   46 +
>  kernel/sched/rt.c                          |    2 +-
>  kernel/sched/sched.h                       |  150 +++
>  kernel/sched/stop_task.c                   |    2 +-
>  kernel/sysctl.c                            |    7 +
>  kernel/trace/trace_sched_wakeup.c          |   45 +-
>  kernel/trace/trace_selftest.c              |   28 +-
>  32 files changed, 3343 insertions(+), 121 deletions(-)
>  create mode 100644 Documentation/scheduler/sched-deadline.txt
>  create mode 100644 include/linux/sched/deadline.h
>  create mode 100644 kernel/sched/cpudeadline.c
>  create mode 100644 kernel/sched/cpudeadline.h
>  create mode 100644 kernel/sched/deadline.c
> 

Re: [PATCH 03/14] sched: SCHED_DEADLINE structures & implementation.

[Peter Zijlstra]

On Mon, Oct 14, 2013 at 12:43:35PM +0200, Juri Lelli wrote:
> +struct sched_dl_entity {
> +	struct rb_node	rb_node;
> +	int nr_cpus_allowed;
> +

Please see:

29baa7478ba4 sched: Move nr_cpus_allowed out of 'struct sched_rt_entity'

Re: [PATCH 03/14] sched: SCHED_DEADLINE structures & implementation.

[Peter Zijlstra]

On Mon, Oct 14, 2013 at 12:43:35PM +0200, Juri Lelli wrote:
> @@ -1693,8 +1701,14 @@ void sched_fork(struct task_struct *p)
>  		p->sched_reset_on_fork = 0;
>  	}
>  
> -	if (!rt_prio(p->prio))
> +	if (dl_prio(p->prio)) {
> +		put_cpu();
> +		return -EAGAIN;

Is this really the error we want to return on fork()?

EAGAIN to me indicates a spurious error and we should try again later;
however as it obvious from the code above; we'll always fail, there's no
point in trying again later.

I would think something like EINVAL; even though there are no arguments
to fork(); would me a better option.

Then again; I really don't care too much; anybody any preferences?

Re: [PATCH 03/14] sched: SCHED_DEADLINE structures & implementation.

[Peter Zijlstra]

On Mon, Oct 14, 2013 at 12:43:35PM +0200, Juri Lelli wrote:
> +/*
> + * We are being explicitly informed that a new instance is starting,
> + * and this means that:
> + *  - the absolute deadline of the entity has to be placed at
> + *    current time + relative deadline;
> + *  - the runtime of the entity has to be set to the maximum value.
> + *
> + * The capability of specifying such event is useful whenever a -deadline
> + * entity wants to (try to!) synchronize its behaviour with the scheduler's
> + * one, and to (try to!) reconcile itself with its own scheduling
> + * parameters.
> + */
> +static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se)
> +{
> +	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
> +	struct rq *rq = rq_of_dl_rq(dl_rq);
> +
> +	WARN_ON(!dl_se->dl_new || dl_se->dl_throttled);
> +
> +	/*
> +	 * We use the regular wall clock time to set deadlines in the
> +	 * future; in fact, we must consider execution overheads (time
> +	 * spent on hardirq context, etc.).
> +	 */
> +	dl_se->deadline = rq->clock + dl_se->dl_deadline;
> +	dl_se->runtime = dl_se->dl_runtime;
> +	dl_se->dl_new = 0;
> +}

78becc270975 sched: Use an accessor to read the rq clock

wants you to use rq_clock(rq) there I think.

Re: [PATCH 03/14] sched: SCHED_DEADLINE structures & implementation.

[Peter Zijlstra]

On Mon, Oct 14, 2013 at 12:43:35PM +0200, Juri Lelli wrote:
> +static void replenish_dl_entity(struct sched_dl_entity *dl_se)
> +{
> +	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
> +	struct rq *rq = rq_of_dl_rq(dl_rq);
> +
> +	/*
> +	 * We keep moving the deadline away until we get some
> +	 * available runtime for the entity. This ensures correct
> +	 * handling of situations where the runtime overrun is
> +	 * arbitrary large.
> +	 */
> +	while (dl_se->runtime <= 0) {
> +		dl_se->deadline += dl_se->dl_deadline;
> +		dl_se->runtime += dl_se->dl_runtime;
> +	}

Are we sure GCC won't be 'smart' and bite us; that is do we need
something like:

  asm("" : "+rm" (dl_se->runtime));

in there? See:

0d98bb2656e9 sched: Prevent compiler from optimising the sched_avg_update() loop

Re: [PATCH 03/14] sched: SCHED_DEADLINE structures & implementation.

[Peter Zijlstra]

On Mon, Oct 14, 2013 at 12:43:35PM +0200, Juri Lelli wrote:
> +static void update_curr_dl(struct rq *rq)
> +{
> +	struct task_struct *curr = rq->curr;
> +	struct sched_dl_entity *dl_se = &curr->dl;
> +	u64 delta_exec;
> +
> +	if (!dl_task(curr) || !on_dl_rq(dl_se))
> +		return;
> +
> +	/*
> +	 * Consumed budget is computed considering the time as
> +	 * observed by schedulable tasks (excluding time spent
> +	 * in hardirq context, etc.)
> +	 */
> +	delta_exec = rq->clock_task - curr->se.exec_start;

Oh, cute.. So we compute deadlines from rq->clock but compute runtime
from rq->clock_task.

So won't that give funny results in that clock_task is generally slower
than clock; so people get more 'time'.

Maybe there's some illumination on this point further on; I'll continue
reading.

Re: [PATCH 03/14] sched: SCHED_DEADLINE structures & implementation.

[Peter Zijlstra]

On Mon, Oct 14, 2013 at 12:43:35PM +0200, Juri Lelli wrote:
> +/*
> + * Yield task semantic for -deadline tasks is:
> + *
> + *   get off from the CPU until our next instance, with
> + *   a new runtime.
> + */

Could you amend that comment with a reason for why this is so? I have
vague recollections of a discussion on this subject but can't recall. It
seems like a useful thing to have.

Re: [PATCH 03/14] sched: SCHED_DEADLINE structures & implementation.

[Peter Zijlstra]

On Mon, Oct 14, 2013 at 12:43:35PM +0200, Juri Lelli wrote:
> +static void set_cpus_allowed_dl(struct task_struct *p,
> +				const struct cpumask *new_mask)
> +{
> +	int weight = cpumask_weight(new_mask);
> +
> +	BUG_ON(!dl_task(p));
> +
> +	cpumask_copy(&p->cpus_allowed, new_mask);
> +	p->dl.nr_cpus_allowed = weight;
> +}

This seems identical so the default in do_set_cpus_allowed(); can we
leave this function out and use the default?

Re: [PATCH 04/14] sched: SCHED_DEADLINE SMP-related data structures & logic.

[Peter Zijlstra]

On Mon, Oct 14, 2013 at 12:43:36PM +0200, Juri Lelli wrote:
> +static inline void dl_set_overload(struct rq *rq)
> +{
> +	if (!rq->online)
> +		return;
> +
> +	cpumask_set_cpu(rq->cpu, rq->rd->dlo_mask);
> +	/*
> +	 * Must be visible before the overload count is
> +	 * set (as in sched_rt.c).
> +	 */
> +	wmb();
> +	atomic_inc(&rq->rd->dlo_count);
> +}

Please, make that smp_wmb() and modify the comment to point to the
matching barrier ; I couldn't find one! Which suggests something is
amiss.

Ideally we'd have something like smp_wmb__after_set_bit() but alas.

Re: [PATCH 06/14] sched: add period support for -deadline tasks.

[Peter Zijlstra]

On Mon, Oct 14, 2013 at 12:43:38PM +0200, Juri Lelli wrote:
> From: Harald Gustafsson <harald.gustafsson@ericsson.com>
> 
> Make it possible to specify a period (different or equal than
> deadline) for -deadline tasks.

Could we add a little blurb here as to why we'd want this?

(I think I do, and I certainly know where to find the answer, but its
better to have a more complete changelog).

Re: [PATCH 07/14] sched: add schedstats for -deadline tasks.

[Peter Zijlstra]

On Mon, Oct 14, 2013 at 12:43:39PM +0200, Juri Lelli wrote:
> From: Dario Faggioli <raistlin@linux.it>
> 
> Add some typical sched-debug output to dl_rq(s) and some
> schedstats to -deadline tasks.

Could you perhaps add a bit to the changelog explaining what kind of
problems this patch helped (or could help) to find?

Re: [PATCH 00/14] sched: SCHED_DEADLINE v8

[Peter Zijlstra]

On Mon, Oct 14, 2013 at 12:43:32PM +0200, Juri Lelli wrote:
> Hello everyone,
> 
> here we go with a new version of the SCHED_DEADLINE patchset (v8). I know that
> it has been a while since I released last version [1], but I thought not to
> spam the mailing list with simple updates. Well... this IS basically an update
> to 3.12-rc5, but it comes right before the next Kernel Summit and Real Time
> Linux Workshop and, since I'll be present at both events, it is probably time
> to fire-up the discussion again.

So I feel we should just merge this stuff already; the only 'issue' I
have is the cgroup abi muck. We clearly need a bit more discussion on
what/how we want things there but there are no easy answers :/ So I'd
say lets try this and see where we'll find ourselves.

Steve; could you go over the SMP push/pull bits as they're modeled after
the stuff you did for FIFO.

Re: [PATCH 00/14] sched: SCHED_DEADLINE v8

[Ingo Molnar]

* Peter Zijlstra <peterz@infradead.org> wrote:

> On Mon, Oct 14, 2013 at 12:43:32PM +0200, Juri Lelli wrote:
> > Hello everyone,
> > 
> > here we go with a new version of the SCHED_DEADLINE patchset (v8). I know that
> > it has been a while since I released last version [1], but I thought not to
> > spam the mailing list with simple updates. Well... this IS basically an update
> > to 3.12-rc5, but it comes right before the next Kernel Summit and Real Time
> > Linux Workshop and, since I'll be present at both events, it is probably time
> > to fire-up the discussion again.
> 
> So I feel we should just merge this stuff already; [...]

Fully agreed - this has been going on for a long time and the patch-set 
has settled down nicely.

> [...] the only 'issue' I have is the cgroup abi muck. We clearly need a 
> bit more discussion on what/how we want things there but there are no 
> easy answers :/ So I'd say lets try this and see where we'll find 
> ourselves.

I'd suggest we leave out the cgroup ABI muck from the first round of 
upstream merge - do it in a second round, that will give it more 
attention.

Thanks,

	Ingo

Re: [PATCH 03/14] sched: SCHED_DEADLINE structures & implementation.

[Juri Lelli]

On 10/14/2013 01:10 PM, Peter Zijlstra wrote:
> On Mon, Oct 14, 2013 at 12:43:35PM +0200, Juri Lelli wrote:
>> +struct sched_dl_entity {
>> +	struct rb_node	rb_node;
>> +	int nr_cpus_allowed;
>> +
> 
> Please see:
> 
> 29baa7478ba4 sched: Move nr_cpus_allowed out of 'struct sched_rt_entity'
> 
> 

Yes, I already considered and used that. But, it is slipped into next patch :\.
I'll bring the change to this patch.

Thanks,

- Juri

Re: [PATCH 00/14] sched: SCHED_DEADLINE v8

[Peter Zijlstra]

On Mon, Oct 14, 2013 at 02:38:55PM +0200, Ingo Molnar wrote:
> > [...] the only 'issue' I have is the cgroup abi muck. We clearly need a 
> > bit more discussion on what/how we want things there but there are no 
> > easy answers :/ So I'd say lets try this and see where we'll find 
> > ourselves.
> 
> I'd suggest we leave out the cgroup ABI muck from the first round of 
> upstream merge - do it in a second round, that will give it more 
> attention.

I'm afraid that'd give rise to some very weird situations for people
using cgroups :/

Re: [PATCH 00/14] sched: SCHED_DEADLINE v8

[Ingo Molnar]

* Peter Zijlstra <peterz@infradead.org> wrote:

> On Mon, Oct 14, 2013 at 02:38:55PM +0200, Ingo Molnar wrote:
>
> > > [...] the only 'issue' I have is the cgroup abi muck. We clearly 
> > > need a bit more discussion on what/how we want things there but 
> > > there are no easy answers :/ So I'd say lets try this and see where 
> > > we'll find ourselves.
> > 
> > I'd suggest we leave out the cgroup ABI muck from the first round of 
> > upstream merge - do it in a second round, that will give it more 
> > attention.
> 
> I'm afraid that'd give rise to some very weird situations for people 
> using cgroups :/

Why? One solution would be to just not offer bandwidth management 
initially - but use some sane default.

Yes, this doesn't offer "true" deadline scheduling yet, but would allow us 
to move most of the code upstream, without any ABI changes initially 
(other than adding the SCHED_DEADLINE policy and such).

Thanks,

	Ingo

Re: [PATCH 00/14] sched: SCHED_DEADLINE v8

[Peter Zijlstra]

On Mon, Oct 14, 2013 at 03:36:38PM +0200, Ingo Molnar wrote:
> 
> * Peter Zijlstra <peterz@infradead.org> wrote:
> 
> > On Mon, Oct 14, 2013 at 02:38:55PM +0200, Ingo Molnar wrote:
> >
> > > > [...] the only 'issue' I have is the cgroup abi muck. We clearly 
> > > > need a bit more discussion on what/how we want things there but 
> > > > there are no easy answers :/ So I'd say lets try this and see where 
> > > > we'll find ourselves.
> > > 
> > > I'd suggest we leave out the cgroup ABI muck from the first round of 
> > > upstream merge - do it in a second round, that will give it more 
> > > attention.
> > 
> > I'm afraid that'd give rise to some very weird situations for people 
> > using cgroups :/
> 
> Why? One solution would be to just not offer bandwidth management 
> initially - but use some sane default.
> 
> Yes, this doesn't offer "true" deadline scheduling yet, but would allow us 
> to move most of the code upstream, without any ABI changes initially 
> (other than adding the SCHED_DEADLINE policy and such).

I suppose we could keep the global sysctl thingies but indeed ignore all
the cgroup limits for now. That would allow some admission control but
leaves out the hairiest part.

Re: [PATCH 03/14] sched: SCHED_DEADLINE structures & implementation.

[Peter Zijlstra]

On Mon, Oct 14, 2013 at 03:05:56PM +0200, Juri Lelli wrote:
> Yes, I already considered and used that. But, it is slipped into next patch :\.
> I'll bring the change to this patch.

Ah yes, the wandering hunks problem. I'm only too familiar with it :-(

Re: [PATCH 12/14] sched: make dl_bw a sub-quota of rt_bw

[Ingo Molnar]

* Juri Lelli <juri.lelli@gmail.com> wrote:

> +#ifdef CONFIG_SMP
> +		struct dl_bw *dl_b = &cpu_rq(i)->rd->dl_bw;
> +#else
> +		struct dl_bw *dl_b = &cpu_rq(i)->dl.dl_bw;
> +#endif

> +#ifdef CONFIG_SMP
> +		struct dl_bw *dl_b = &cpu_rq(i)->rd->dl_bw;
> +#else
> +		struct dl_bw *dl_b = &cpu_rq(i)->dl.dl_bw;
> +#endif

Btw., this kind of SMP/UP assymetry pattern really sucks. Why not make UP 
use the SMP data structure, even if it's degenerate?

Thanks,

	Ingo

Re: [PATCH 03/14] sched: SCHED_DEADLINE structures & implementation.

[Juri Lelli]

On 10/14/2013 01:24 PM, Peter Zijlstra wrote:
> On Mon, Oct 14, 2013 at 12:43:35PM +0200, Juri Lelli wrote:
>> +/*
>> + * We are being explicitly informed that a new instance is starting,
>> + * and this means that:
>> + *  - the absolute deadline of the entity has to be placed at
>> + *    current time + relative deadline;
>> + *  - the runtime of the entity has to be set to the maximum value.
>> + *
>> + * The capability of specifying such event is useful whenever a -deadline
>> + * entity wants to (try to!) synchronize its behaviour with the scheduler's
>> + * one, and to (try to!) reconcile itself with its own scheduling
>> + * parameters.
>> + */
>> +static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se)
>> +{
>> +	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
>> +	struct rq *rq = rq_of_dl_rq(dl_rq);
>> +
>> +	WARN_ON(!dl_se->dl_new || dl_se->dl_throttled);
>> +
>> +	/*
>> +	 * We use the regular wall clock time to set deadlines in the
>> +	 * future; in fact, we must consider execution overheads (time
>> +	 * spent on hardirq context, etc.).
>> +	 */
>> +	dl_se->deadline = rq->clock + dl_se->dl_deadline;
>> +	dl_se->runtime = dl_se->dl_runtime;
>> +	dl_se->dl_new = 0;
>> +}
> 
> 78becc270975 sched: Use an accessor to read the rq clock
> 
> wants you to use rq_clock(rq) there I think.
> 
> 

Modified here and below.

Thanks,

- Juri

Re: [PATCH 03/14] sched: SCHED_DEADLINE structures & implementation.

[Juri Lelli]

On 10/14/2013 01:33 PM, Peter Zijlstra wrote:
> On Mon, Oct 14, 2013 at 12:43:35PM +0200, Juri Lelli wrote:
>> +static void replenish_dl_entity(struct sched_dl_entity *dl_se)
>> +{
>> +	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
>> +	struct rq *rq = rq_of_dl_rq(dl_rq);
>> +
>> +	/*
>> +	 * We keep moving the deadline away until we get some
>> +	 * available runtime for the entity. This ensures correct
>> +	 * handling of situations where the runtime overrun is
>> +	 * arbitrary large.
>> +	 */
>> +	while (dl_se->runtime <= 0) {
>> +		dl_se->deadline += dl_se->dl_deadline;
>> +		dl_se->runtime += dl_se->dl_runtime;
>> +	}
> 
> Are we sure GCC won't be 'smart' and bite us; that is do we need
> something like:
> 
>   asm("" : "+rm" (dl_se->runtime));
> 
> in there? See:
> 
> 0d98bb2656e9 sched: Prevent compiler from optimising the sched_avg_update() loop
> 

When disassembled everything seems fine, at least for x86 and ARM. Do I add the
fake data hazard anyway?

Thanks,

- Juri

Re: [PATCH 03/14] sched: SCHED_DEADLINE structures & implementation.

[Peter Zijlstra]

On Mon, Oct 14, 2013 at 06:16:50PM +0200, Juri Lelli wrote:
> 
> When disassembled everything seems fine, at least for x86 and ARM. Do I add the
> fake data hazard anyway?

nah, lets add it when we find it's needed.

Re: [PATCH 03/14] sched: SCHED_DEADLINE structures & implementation.

[Juri Lelli]

On 10/14/2013 01:44 PM, Peter Zijlstra wrote:
> On Mon, Oct 14, 2013 at 12:43:35PM +0200, Juri Lelli wrote:
>> +static void update_curr_dl(struct rq *rq)
>> +{
>> +	struct task_struct *curr = rq->curr;
>> +	struct sched_dl_entity *dl_se = &curr->dl;
>> +	u64 delta_exec;
>> +
>> +	if (!dl_task(curr) || !on_dl_rq(dl_se))
>> +		return;
>> +
>> +	/*
>> +	 * Consumed budget is computed considering the time as
>> +	 * observed by schedulable tasks (excluding time spent
>> +	 * in hardirq context, etc.)
>> +	 */
>> +	delta_exec = rq->clock_task - curr->se.exec_start;
> 
> Oh, cute.. So we compute deadlines from rq->clock but compute runtime
> from rq->clock_task.
> 
> So won't that give funny results in that clock_task is generally slower
> than clock; so people get more 'time'.
> 
> Maybe there's some illumination on this point further on; I'll continue
> reading.
> 

We discussed on this point in the past...

On 04/23/2012 12:31 PM, Peter Zijlstra wrote:> On Fri, 2012-04-06 at 09:14
+0200, Juri Lelli wrote:
>> +       dl_se->deadline = rq->clock + dl_se->dl_deadline;
>
> You might want to use rq->clock_task, this clock excludes times spend in
> hardirq context and steal-time (when paravirt).
>
> Then again, it might not want to use that.. but its something you might
> want to consider and make explicit by means of a comment.
>

On 04/24/2012 08:29 AM, Dario Faggioli wrote:> On Tue, 2012-04-24 at 00:25
+0100, Tommaso Cucinotta wrote:
>>> The idea is that ->clock_task gives the time as observed by schedulable
>>> tasks and excludes other muck.
>>
>> so clock_task might be better to compute the consumed budget at task
>> deschedule, but for setting deadlines one period ahead in the future
>> guess the regular wall-time rq->clock is the one to be used?
>>
> Yep, that was the idea, unless my recollection has completely gone
> flaky! :-P
>
> Perhaps adding a comment saying right this thing above, as Peter
> suggested?

And we kind of agreed on the current use of the different clocks. Do you think
we have to reason (test) more about this? Or do we live with that and see if
something strange happens? (I actually didn't see anything suspiciuos in my
use of the patchset).

Thanks,

- Juri

Re: [PATCH 03/14] sched: SCHED_DEADLINE structures & implementation.

[Peter Zijlstra]

On Mon, Oct 14, 2013 at 06:58:51PM +0200, Juri Lelli wrote:
> On 10/14/2013 01:44 PM, Peter Zijlstra wrote:
> > On Mon, Oct 14, 2013 at 12:43:35PM +0200, Juri Lelli wrote:
> We discussed on this point in the past...

Ah, completely forgot about that; please update the comment that we
indeed use different clocks for deadline and runtime and that the full
ramifications need further study; but that deadline needs hard walltime
and clock_task is more natural for runtime.

Re: [PATCH 03/14] sched: SCHED_DEADLINE structures & implementation.

[Juri Lelli]

On 10/14/2013 01:49 PM, Peter Zijlstra wrote:
> On Mon, Oct 14, 2013 at 12:43:35PM +0200, Juri Lelli wrote:
>> +/*
>> + * Yield task semantic for -deadline tasks is:
>> + *
>> + *   get off from the CPU until our next instance, with
>> + *   a new runtime.
>> + */
> 
> Could you amend that comment with a reason for why this is so? I have
> vague recollections of a discussion on this subject but can't recall. It
> seems like a useful thing to have.
> 

I think discussion happened before I started maintaining the patchset, but I'm
quite sure this would be helpful for bandwidth reclaiming mechanisms.
Basically, if I'm able to report that I didn't use all the budget of my current
instance, I could donate that remaining budget to other task instances.
Bandwidth reclaiming is another nice thing to have, and we actually have some
ideas on how to implement it (TODO list always grows :)).

I'll amend the comment saying that this function is of little use now, but will
be helpful in the future.

Thanks,

- Juri

Re: [PATCH 03/14] sched: SCHED_DEADLINE structures & implementation.

[Juri Lelli]

On 10/14/2013 07:34 PM, Peter Zijlstra wrote:
> On Mon, Oct 14, 2013 at 06:58:51PM +0200, Juri Lelli wrote:
>> On 10/14/2013 01:44 PM, Peter Zijlstra wrote:
>>> On Mon, Oct 14, 2013 at 12:43:35PM +0200, Juri Lelli wrote:
>> We discussed on this point in the past...
> 
> Ah, completely forgot about that; please update the comment that we
> indeed use different clocks for deadline and runtime and that the full
> ramifications need further study; but that deadline needs hard walltime
> and clock_task is more natural for runtime.
> 

Ok, done.

Thanks,

- Juri

Re: [PATCH 03/14] sched: SCHED_DEADLINE structures & implementation.

[Juri Lelli]

On 10/14/2013 01:51 PM, Peter Zijlstra wrote:
> On Mon, Oct 14, 2013 at 12:43:35PM +0200, Juri Lelli wrote:
>> +static void set_cpus_allowed_dl(struct task_struct *p,
>> +				const struct cpumask *new_mask)
>> +{
>> +	int weight = cpumask_weight(new_mask);
>> +
>> +	BUG_ON(!dl_task(p));
>> +
>> +	cpumask_copy(&p->cpus_allowed, new_mask);
>> +	p->dl.nr_cpus_allowed = weight;
>> +}
> 
> This seems identical so the default in do_set_cpus_allowed(); can we
> leave this function out and use the default?
> 

Another thing that is changed completely in next patch. Anyway, I removed it
from here too.

Thanks,

- Juri

Re: [PATCH 06/14] sched: add period support for -deadline tasks.

[Juri Lelli]

On 10/14/2013 02:07 PM, Peter Zijlstra wrote:
> On Mon, Oct 14, 2013 at 12:43:38PM +0200, Juri Lelli wrote:
>> From: Harald Gustafsson <harald.gustafsson@ericsson.com>
>>
>> Make it possible to specify a period (different or equal than
>> deadline) for -deadline tasks.
> 
> Could we add a little blurb here as to why we'd want this?
> 
> (I think I do, and I certainly know where to find the answer, but its
> better to have a more complete changelog).
> 

Yes, I could amend the commit message in something like this:

Make it possible to specify a period (different or equal than deadline) for
-deadline tasks. Relative deadlines (D_i) are used on task arrivals to generate
new scheduling (absolute) deadlines as "d = t + D_i", and periods (P_i) to
postpone the scheduling deadlines as "d = d + P_i" when the budget is zero.
This is in general useful to model (and schedule) tasks that have slow
activation rates (long periods), but have to be scheduled soon once activated
(short deadlines).

What do you think?

Thanks,

- Juri

Re: [PATCH 06/14] sched: add period support for -deadline tasks.

[Peter Zijlstra]

On Tue, Oct 15, 2013 at 10:23:19AM +0200, Juri Lelli wrote:
> On 10/14/2013 02:07 PM, Peter Zijlstra wrote:
> > On Mon, Oct 14, 2013 at 12:43:38PM +0200, Juri Lelli wrote:
> >> From: Harald Gustafsson <harald.gustafsson@ericsson.com>
> >>
> >> Make it possible to specify a period (different or equal than
> >> deadline) for -deadline tasks.
> > 
> > Could we add a little blurb here as to why we'd want this?
> > 
> > (I think I do, and I certainly know where to find the answer, but its
> > better to have a more complete changelog).
> > 
> 
> Yes, I could amend the commit message in something like this:
> 
> Make it possible to specify a period (different or equal than deadline) for
> -deadline tasks. Relative deadlines (D_i) are used on task arrivals to generate
> new scheduling (absolute) deadlines as "d = t + D_i", and periods (P_i) to
> postpone the scheduling deadlines as "d = d + P_i" when the budget is zero.
> This is in general useful to model (and schedule) tasks that have slow
> activation rates (long periods), but have to be scheduled soon once activated
> (short deadlines).
> 
> What do you think?

Yes that's much better. Thanks!

Re: [PATCH 07/14] sched: add schedstats for -deadline tasks.

[Juri Lelli]

On 10/14/2013 02:08 PM, Peter Zijlstra wrote:
> On Mon, Oct 14, 2013 at 12:43:39PM +0200, Juri Lelli wrote:
>> From: Dario Faggioli <raistlin@linux.it>
>>
>> Add some typical sched-debug output to dl_rq(s) and some
>> schedstats to -deadline tasks.
> 
> Could you perhaps add a bit to the changelog explaining what kind of
> problems this patch helped (or could help) to find?
> 

Expanded in this:

Add some typical sched-debug output to dl_rq(s) and some
schedstats to -deadline tasks. This helps spotting problems
with queue and dequeue operations (incorrect ordering) and
gives hints about system status (one can have an idea if the
system is overloaded, if tasks are missing their deadlines
and the entity of such anomalies).

Thanks,

- Juri

Re: [PATCH 04/14] sched: SCHED_DEADLINE SMP-related data structures & logic.

[Juri Lelli]

On 10/14/2013 02:03 PM, Peter Zijlstra wrote:
> On Mon, Oct 14, 2013 at 12:43:36PM +0200, Juri Lelli wrote:
>> +static inline void dl_set_overload(struct rq *rq)
>> +{
>> +	if (!rq->online)
>> +		return;
>> +
>> +	cpumask_set_cpu(rq->cpu, rq->rd->dlo_mask);
>> +	/*
>> +	 * Must be visible before the overload count is
>> +	 * set (as in sched_rt.c).
>> +	 */
>> +	wmb();
>> +	atomic_inc(&rq->rd->dlo_count);
>> +}
> 
> Please, make that smp_wmb() and modify the comment to point to the
> matching barrier ; I couldn't find one! Which suggests something is
> amiss.
> 
> Ideally we'd have something like smp_wmb__after_set_bit() but alas.
> 

The only user of this function is pull_dl_task (that tries to pull only if at
least one runqueue of the root_domain is overloaded). Surely makes sense to
ensure that changes in the dlo_mask have to be visible before we check if we
should look at that mask. Am I right if I say that the matching barrier is
constituted by the spin_lock on this_rq acquired by schedule() before calling
pre_schedule()?

Same thing in rt_set_overload(), do we need to modify the comment also there?

Thanks,

- Juri

Re: [PATCH 12/14] sched: make dl_bw a sub-quota of rt_bw

[Juri Lelli]

On 10/14/2013 04:06 PM, Ingo Molnar wrote:
> 
> * Juri Lelli <juri.lelli@gmail.com> wrote:
> 
>> +#ifdef CONFIG_SMP
>> +		struct dl_bw *dl_b = &cpu_rq(i)->rd->dl_bw;
>> +#else
>> +		struct dl_bw *dl_b = &cpu_rq(i)->dl.dl_bw;
>> +#endif
> 
>> +#ifdef CONFIG_SMP
>> +		struct dl_bw *dl_b = &cpu_rq(i)->rd->dl_bw;
>> +#else
>> +		struct dl_bw *dl_b = &cpu_rq(i)->dl.dl_bw;
>> +#endif
> 
> Btw., this kind of SMP/UP assymetry pattern really sucks. Why not make UP 
> use the SMP data structure, even if it's degenerate?
> 

Yes, I don't like it either, but that comes from the fact that it seemed to me
that, semantically, bandwidth for -deadline tasks has to be associated to the
single runqueue in UP and to the root_domain for SMP. In UP root_domain is
compiled out, so I'm not sure to understand what you suggest. I could probably
let dl_bw live on runqueues with the assumption that all the runqueues from the
same root_domain have the same dl_bw, that represents the dl_bw of the
root_domain. But I don't like this replication either :(.

Thanks,

- Juri

Re: [PATCH 12/14] sched: make dl_bw a sub-quota of rt_bw

[Peter Zijlstra]

On Tue, Oct 15, 2013 at 12:00:20PM +0200, Juri Lelli wrote:
> On 10/14/2013 04:06 PM, Ingo Molnar wrote:
> > 
> > * Juri Lelli <juri.lelli@gmail.com> wrote:
> > 
> >> +#ifdef CONFIG_SMP
> >> +		struct dl_bw *dl_b = &cpu_rq(i)->rd->dl_bw;
> >> +#else
> >> +		struct dl_bw *dl_b = &cpu_rq(i)->dl.dl_bw;
> >> +#endif
> > 
> >> +#ifdef CONFIG_SMP
> >> +		struct dl_bw *dl_b = &cpu_rq(i)->rd->dl_bw;
> >> +#else
> >> +		struct dl_bw *dl_b = &cpu_rq(i)->dl.dl_bw;
> >> +#endif
> > 
> > Btw., this kind of SMP/UP assymetry pattern really sucks. Why not make UP 
> > use the SMP data structure, even if it's degenerate?
> > 
> 
> Yes, I don't like it either, but that comes from the fact that it seemed to me
> that, semantically, bandwidth for -deadline tasks has to be associated to the
> single runqueue in UP and to the root_domain for SMP. In UP root_domain is
> compiled out, so I'm not sure to understand what you suggest. I could probably
> let dl_bw live on runqueues with the assumption that all the runqueues from the
> same root_domain have the same dl_bw, that represents the dl_bw of the
> root_domain. But I don't like this replication either :(.

#ifdef CONFIG_SMP

static inline struct dl_bw *dl_bw_of(int i)
{
	return &cpu_rq(i)->rd->dl_bw;
}

#else

static inline struct dl_bw *dl_bw_of(int i)
{
	return &cpu_rq(i)->dl.dl_bw;
}

#endif

?

Re: [PATCH 04/14] sched: SCHED_DEADLINE SMP-related data structures & logic.

[Peter Zijlstra]

On Tue, Oct 15, 2013 at 11:36:17AM +0200, Juri Lelli wrote:
> On 10/14/2013 02:03 PM, Peter Zijlstra wrote:
> > On Mon, Oct 14, 2013 at 12:43:36PM +0200, Juri Lelli wrote:
> >> +static inline void dl_set_overload(struct rq *rq)
> >> +{
> >> +	if (!rq->online)
> >> +		return;
> >> +
> >> +	cpumask_set_cpu(rq->cpu, rq->rd->dlo_mask);
> >> +	/*
> >> +	 * Must be visible before the overload count is
> >> +	 * set (as in sched_rt.c).
> >> +	 */
> >> +	wmb();
> >> +	atomic_inc(&rq->rd->dlo_count);
> >> +}
> > 
> > Please, make that smp_wmb() and modify the comment to point to the
> > matching barrier ; I couldn't find one! Which suggests something is
> > amiss.
> > 
> > Ideally we'd have something like smp_wmb__after_set_bit() but alas.
> > 
> 
> The only user of this function is pull_dl_task (that tries to pull only if at
> least one runqueue of the root_domain is overloaded). Surely makes sense to
> ensure that changes in the dlo_mask have to be visible before we check if we
> should look at that mask. Am I right if I say that the matching barrier is
> constituted by the spin_lock on this_rq acquired by schedule() before calling
> pre_schedule()?
> 
> Same thing in rt_set_overload(), do we need to modify the comment also there?

So I haven't looked at the dl code, but for the RT code the below is
required.

Without that smp_rmb() in there we could actually miss seeing the
rto_mask bit.

---
 kernel/sched/rt.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index e9304cdc26fe..a848f526b941 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -246,8 +246,10 @@ static inline void rt_set_overload(struct rq *rq)
 	 * if we should look at the mask. It would be a shame
 	 * if we looked at the mask, but the mask was not
 	 * updated yet.
+	 *
+	 * Matched by the barrier in pull_rt_task().
 	 */
-	wmb();
+	smp_wmb();
 	atomic_inc(&rq->rd->rto_count);
 }
 
@@ -1626,6 +1628,12 @@ static int pull_rt_task(struct rq *this_rq)
 	if (likely(!rt_overloaded(this_rq)))
 		return 0;
 
+	/*
+	 * Match the barrier from rt_set_overloaded; this guarantees that if we
+	 * see overloaded we must also see the rto_mask bit.
+	 */
+	smp_rmb();
+
 	for_each_cpu(cpu, this_rq->rd->rto_mask) {
 		if (this_cpu == cpu)
 			continue;

Re: [PATCH 12/14] sched: make dl_bw a sub-quota of rt_bw

[Juri Lelli]

On 10/15/2013 12:26 PM, Peter Zijlstra wrote:
> On Tue, Oct 15, 2013 at 12:00:20PM +0200, Juri Lelli wrote:
>> On 10/14/2013 04:06 PM, Ingo Molnar wrote:
>>>
>>> * Juri Lelli <juri.lelli@gmail.com> wrote:
>>>
>>>> +#ifdef CONFIG_SMP
>>>> +		struct dl_bw *dl_b = &cpu_rq(i)->rd->dl_bw;
>>>> +#else
>>>> +		struct dl_bw *dl_b = &cpu_rq(i)->dl.dl_bw;
>>>> +#endif
>>>
>>>> +#ifdef CONFIG_SMP
>>>> +		struct dl_bw *dl_b = &cpu_rq(i)->rd->dl_bw;
>>>> +#else
>>>> +		struct dl_bw *dl_b = &cpu_rq(i)->dl.dl_bw;
>>>> +#endif
>>>
>>> Btw., this kind of SMP/UP assymetry pattern really sucks. Why not make UP 
>>> use the SMP data structure, even if it's degenerate?
>>>
>>
>> Yes, I don't like it either, but that comes from the fact that it seemed to me
>> that, semantically, bandwidth for -deadline tasks has to be associated to the
>> single runqueue in UP and to the root_domain for SMP. In UP root_domain is
>> compiled out, so I'm not sure to understand what you suggest. I could probably
>> let dl_bw live on runqueues with the assumption that all the runqueues from the
>> same root_domain have the same dl_bw, that represents the dl_bw of the
>> root_domain. But I don't like this replication either :(.
> 
> #ifdef CONFIG_SMP
> 
> static inline struct dl_bw *dl_bw_of(int i)
> {
> 	return &cpu_rq(i)->rd->dl_bw;
> }
> 
> #else
> 
> static inline struct dl_bw *dl_bw_of(int i)
> {
> 	return &cpu_rq(i)->dl.dl_bw;
> }
> 
> #endif
> 
> ?
> 

Yes, way better.

Thanks,

- Juri

Re: [PATCH 04/14] sched: SCHED_DEADLINE SMP-related data structures & logic.

[Juri Lelli]

On 10/15/2013 12:35 PM, Peter Zijlstra wrote:
> On Tue, Oct 15, 2013 at 11:36:17AM +0200, Juri Lelli wrote:
>> On 10/14/2013 02:03 PM, Peter Zijlstra wrote:
>>> On Mon, Oct 14, 2013 at 12:43:36PM +0200, Juri Lelli wrote:
>>>> +static inline void dl_set_overload(struct rq *rq)
>>>> +{
>>>> +	if (!rq->online)
>>>> +		return;
>>>> +
>>>> +	cpumask_set_cpu(rq->cpu, rq->rd->dlo_mask);
>>>> +	/*
>>>> +	 * Must be visible before the overload count is
>>>> +	 * set (as in sched_rt.c).
>>>> +	 */
>>>> +	wmb();
>>>> +	atomic_inc(&rq->rd->dlo_count);
>>>> +}
>>>
>>> Please, make that smp_wmb() and modify the comment to point to the
>>> matching barrier ; I couldn't find one! Which suggests something is
>>> amiss.
>>>
>>> Ideally we'd have something like smp_wmb__after_set_bit() but alas.
>>>
>>
>> The only user of this function is pull_dl_task (that tries to pull only if at
>> least one runqueue of the root_domain is overloaded). Surely makes sense to
>> ensure that changes in the dlo_mask have to be visible before we check if we
>> should look at that mask. Am I right if I say that the matching barrier is
>> constituted by the spin_lock on this_rq acquired by schedule() before calling
>> pre_schedule()?
>>
>> Same thing in rt_set_overload(), do we need to modify the comment also there?
> 
> So I haven't looked at the dl code, but for the RT code the below is
> required.
> 

Same thing for dl code.

Thanks,

- Juri

> Without that smp_rmb() in there we could actually miss seeing the
> rto_mask bit.
> 
> ---
>  kernel/sched/rt.c | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
> index e9304cdc26fe..a848f526b941 100644
> --- a/kernel/sched/rt.c
> +++ b/kernel/sched/rt.c
> @@ -246,8 +246,10 @@ static inline void rt_set_overload(struct rq *rq)
>  	 * if we should look at the mask. It would be a shame
>  	 * if we looked at the mask, but the mask was not
>  	 * updated yet.
> +	 *
> +	 * Matched by the barrier in pull_rt_task().
>  	 */
> -	wmb();
> +	smp_wmb();
>  	atomic_inc(&rq->rd->rto_count);
>  }
>  
> @@ -1626,6 +1628,12 @@ static int pull_rt_task(struct rq *this_rq)
>  	if (likely(!rt_overloaded(this_rq)))
>  		return 0;
>  
> +	/*
> +	 * Match the barrier from rt_set_overloaded; this guarantees that if we
> +	 * see overloaded we must also see the rto_mask bit.
> +	 */
> +	smp_rmb();
> +
>  	for_each_cpu(cpu, this_rq->rd->rto_mask) {
>  		if (this_cpu == cpu)
>  			continue;
> 

Re: [PATCH 12/14] sched: make dl_bw a sub-quota of rt_bw

[Ingo Molnar]

* Peter Zijlstra <peterz@infradead.org> wrote:

> On Tue, Oct 15, 2013 at 12:00:20PM +0200, Juri Lelli wrote:
> > On 10/14/2013 04:06 PM, Ingo Molnar wrote:
> > > 
> > > * Juri Lelli <juri.lelli@gmail.com> wrote:
> > > 
> > >> +#ifdef CONFIG_SMP
> > >> +		struct dl_bw *dl_b = &cpu_rq(i)->rd->dl_bw;
> > >> +#else
> > >> +		struct dl_bw *dl_b = &cpu_rq(i)->dl.dl_bw;
> > >> +#endif
> > > 
> > >> +#ifdef CONFIG_SMP
> > >> +		struct dl_bw *dl_b = &cpu_rq(i)->rd->dl_bw;
> > >> +#else
> > >> +		struct dl_bw *dl_b = &cpu_rq(i)->dl.dl_bw;
> > >> +#endif
> > > 
> > > Btw., this kind of SMP/UP assymetry pattern really sucks. Why not make UP 
> > > use the SMP data structure, even if it's degenerate?
> > > 
> > 
> > Yes, I don't like it either, but that comes from the fact that it seemed to me
> > that, semantically, bandwidth for -deadline tasks has to be associated to the
> > single runqueue in UP and to the root_domain for SMP. In UP root_domain is
> > compiled out, so I'm not sure to understand what you suggest. I could probably
> > let dl_bw live on runqueues with the assumption that all the runqueues from the
> > same root_domain have the same dl_bw, that represents the dl_bw of the
> > root_domain. But I don't like this replication either :(.
> 
> #ifdef CONFIG_SMP
> 
> static inline struct dl_bw *dl_bw_of(int i)
> {
> 	return &cpu_rq(i)->rd->dl_bw;
> }
> 
> #else
> 
> static inline struct dl_bw *dl_bw_of(int i)
> {
> 	return &cpu_rq(i)->dl.dl_bw;
> }
> 
> #endif
> 
> ?

Really, please make it _symmetric_ ...

Single core systems are becoming a historic curiosity, should we should 
justify every piece of extra complexity we add for them.

So I'd rather see obvious SMP code where the UP case works fine too, and 
_then_ maybe check a separate patch that adds the UP optimization, with 
(object size) numbers proving that it's worth it, etc.

Thanks,

	Ingo

Re: [PATCH 12/14] sched: make dl_bw a sub-quota of rt_bw

[Peter Zijlstra]

On Tue, Oct 15, 2013 at 02:25:22PM +0200, Ingo Molnar wrote:
> Really, please make it _symmetric_ ...
> 
> Single core systems are becoming a historic curiosity, should we should 
> justify every piece of extra complexity we add for them.
> 
> So I'd rather see obvious SMP code where the UP case works fine too, and 
> _then_ maybe check a separate patch that adds the UP optimization, with 
> (object size) numbers proving that it's worth it, etc.

That's a slightly larger task than it appears; the core scheduler code
they rely on with smp doesn't exist on up.

We can do this but we need to do it scheduler wide.

Re: [PATCH 12/14] sched: make dl_bw a sub-quota of rt_bw

[Ingo Molnar]

* Peter Zijlstra <peterz@infradead.org> wrote:

> On Tue, Oct 15, 2013 at 02:25:22PM +0200, Ingo Molnar wrote:
> >
> > Really, please make it _symmetric_ ...
> > 
> > Single core systems are becoming a historic curiosity, should we 
> > should justify every piece of extra complexity we add for them.
> > 
> > So I'd rather see obvious SMP code where the UP case works fine too, 
> > and _then_ maybe check a separate patch that adds the UP optimization, 
> > with (object size) numbers proving that it's worth it, etc.
> 
> That's a slightly larger task than it appears; the core scheduler code 
> they rely on with smp doesn't exist on up.
> 
> We can do this but we need to do it scheduler wide.

The scheduler has over 800 #ifdefs or similar preprocessor directives:

  comet:~/tip> git grep '^#' kernel/sched/ | grep -v include | wc -l
  855

I'd like to see this simplified a bit, _especially_ before we add new 
complexity ...

Thanks,

	Ingo

Re: [PATCH 12/14] sched: make dl_bw a sub-quota of rt_bw

[Peter Zijlstra]

On Tue, Oct 15, 2013 at 03:11:33PM +0200, Ingo Molnar wrote:
> The scheduler has over 800 #ifdefs or similar preprocessor directives:
> 
>   comet:~/tip> git grep '^#' kernel/sched/ | grep -v include | wc -l
>   855
> 
> I'd like to see this simplified a bit, _especially_ before we add new 
> complexity ...

I agree; however I also think its unfair to pile this on Juri. Esp the
avenue pushed here, which will increase UP text and (runtime) data
sizes, to which I think some people will still object.

There's this entire 'maker' community (aka. internet of things) now
using very small Linux devices. Think Raspberry-Pi, Intel Quark (however much
I hate Intel for shipping a new 32bit device) etc.

These people are wanting to run Linux on these tiny devices, with tiny
memories etc; we shouldn't make their life harder than it already is.

Also; you didn't object about the 29 new #ifdefs currently in
tip.

How about we use some of the 'quality' conference time in EDI to do some
big code shuffles to get rid of some of them. I'm sure we can reduce the
number of ifdeffery by simply merging various similar blocks and maybe
write a few extra helper functions.

This is how kernel/sched/ got created in the first place; as a means to
keep the fingers busy at a conference ;-)

Re: [PATCH 12/14] sched: make dl_bw a sub-quota of rt_bw

[Ingo Molnar]

* Peter Zijlstra <peterz@infradead.org> wrote:

> On Tue, Oct 15, 2013 at 03:11:33PM +0200, Ingo Molnar wrote:
> > The scheduler has over 800 #ifdefs or similar preprocessor directives:
> > 
> >   comet:~/tip> git grep '^#' kernel/sched/ | grep -v include | wc -l
> >   855
> > 
> > I'd like to see this simplified a bit, _especially_ before we add new 
> > complexity ...
> 
> I agree; however I also think its unfair to pile this on Juri.

Well, it's that particular ugly #ifdef that caught my eye.

> [...] Esp the avenue pushed here, which will increase UP text and 
> (runtime) data sizes, to which I think some people will still object.
> 
> There's this entire 'maker' community (aka. internet of things) now 
> using very small Linux devices. Think Raspberry-Pi, Intel Quark (however 
> much I hate Intel for shipping a new 32bit device) etc.
> 
> These people are wanting to run Linux on these tiny devices, with tiny 
> memories etc; we shouldn't make their life harder than it already is.
> 
> Also; you didn't object about the 29 new #ifdefs currently in tip.

It was the straw that broke the camel's back.

> How about we use some of the 'quality' conference time in EDI to do some 
> big code shuffles to get rid of some of them. I'm sure we can reduce the 
> number of ifdeffery by simply merging various similar blocks and maybe 
> write a few extra helper functions.
> 
> This is how kernel/sched/ got created in the first place; as a means to 
> keep the fingers busy at a conference ;-)

LOL, agreed, we can try that ;-)

Also, we can certainly merge SCHED_DEADLINE first, as long as there's a 
hard feature stop afterwards and as long as cleanups will eventually 
arrive.

Thanks,

	Ingo

[tip:sched/core] sched/rt: Add missing rmb()

[tip-bot for Peter Zijlstra]

Commit-ID:  7c3f2ab7b844f1a859afbc3d41925e8a0faba5fa
Gitweb:     http://git.kernel.org/tip/7c3f2ab7b844f1a859afbc3d41925e8a0faba5fa
Author:     Peter Zijlstra <peterz@infradead.org>
AuthorDate: Tue, 15 Oct 2013 12:35:07 +0200
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 16 Oct 2013 14:22:13 +0200

sched/rt: Add missing rmb()

While discussing the proposed SCHED_DEADLINE patches which in parts
mimic the existing FIFO code it was noticed that the wmb in
rt_set_overloaded() didn't have a matching barrier.

The only site using rt_overloaded() to test the rto_count is
pull_rt_task() and we should issue a matching rmb before then assuming
there's an rto_mask bit set.

Without that smp_rmb() in there we could actually miss seeing the
rto_mask bit.

Also, change to using smp_[wr]mb(), even though this is SMP only code;
memory barriers without smp_ always make me think they're against
hardware of some sort.

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: vincent.guittot@linaro.org
Cc: luca.abeni@unitn.it
Cc: bruce.ashfield@windriver.com
Cc: dhaval.giani@gmail.com
Cc: rostedt@goodmis.org
Cc: hgu1972@gmail.com
Cc: oleg@redhat.com
Cc: fweisbec@gmail.com
Cc: darren@dvhart.com
Cc: johan.eker@ericsson.com
Cc: p.faure@akatech.ch
Cc: paulmck@linux.vnet.ibm.com
Cc: raistlin@linux.it
Cc: claudio@evidence.eu.com
Cc: insop.song@gmail.com
Cc: michael@amarulasolutions.com
Cc: liming.wang@windriver.com
Cc: fchecconi@gmail.com
Cc: jkacur@redhat.com
Cc: tommaso.cucinotta@sssup.it
Cc: Juri Lelli <juri.lelli@gmail.com>
Cc: harald.gustafsson@ericsson.com
Cc: nicola.manica@disi.unitn.it
Cc: tglx@linutronix.de
Link: http://lkml.kernel.org/r/20131015103507.GF10651@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 kernel/sched/rt.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index e9304cd..a848f52 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -246,8 +246,10 @@ static inline void rt_set_overload(struct rq *rq)
 	 * if we should look at the mask. It would be a shame
 	 * if we looked at the mask, but the mask was not
 	 * updated yet.
+	 *
+	 * Matched by the barrier in pull_rt_task().
 	 */
-	wmb();
+	smp_wmb();
 	atomic_inc(&rq->rd->rto_count);
 }
 
@@ -1626,6 +1628,12 @@ static int pull_rt_task(struct rq *this_rq)
 	if (likely(!rt_overloaded(this_rq)))
 		return 0;
 
+	/*
+	 * Match the barrier from rt_set_overloaded; this guarantees that if we
+	 * see overloaded we must also see the rto_mask bit.
+	 */
+	smp_rmb();
+
 	for_each_cpu(cpu, this_rq->rd->rto_mask) {
 		if (this_cpu == cpu)
 			continue;