* [PATCH 00/14] sched: SCHED_DEADLINE v7
@ 2013-02-11 18:50 Juri Lelli
2013-02-11 18:50 ` [PATCH 01/14] sched: add sched_class->task_dead Juri Lelli
` (13 more replies)
0 siblings, 14 replies; 19+ messages in thread
From: Juri Lelli @ 2013-02-11 18:50 UTC (permalink / raw)
To: peterz, tglx
Cc: mingo, rostedt, oleg, fweisbec, darren, johan.eker, p.faure,
linux-kernel, claudio, michael, fchecconi, tommaso.cucinotta,
juri.lelli, nicola.manica, luca.abeni, dhaval.giani, hgu1972,
paulmck, raistlin, insop.song, liming.wang, jkacur,
harald.gustafsson, vincent.guittot
Hello everyone,
several changes, some bugfixes and a major testing effort bring me to
release a new version of the SCHED_DEADLINE patchset (v7). In addition,
given the fact that the project has been around for quite some time with
always a positive feedback from the community and since we have reached
a stable and tested set of functionalities, I think it is time to remove
the RFC tag. However, I consider this as another intermediate release as
I would like even more testing from the community itself and I'm also
working to ship a motivating use case with next releases. I had many
interactions with users, especially from industry, after past releases.
Some of them seem to confirm their interest proposing enhancements and
modifications (e.g., http://bit.ly/XVQWrb); some others are willing to
collaborate directly. This makes me confident that such a use case is
on the way.
If you missed the whole story[1], this patchset introduces a new deadline
based real-time task scheduling policy --called SCHED_DEADLINE-- with
bandwidth isolation (aka "resource reservation") capabilities. It supports
global/clustered multiprocessor scheduling through dynamic task migrations.
>From the previous releases[1]:
- rebase on top of 3.8-rc7;
- comments and fixes coming from the reviews we got have been considered
and applied;
- u128 support has been removed and internal math has been restricted
to microseconds resolution (to avoid overflows);
- dl.c, cpudl.{c,h} renamed as deadline.c, cpudeadline.{c,h};
- documentation fixed and extended (how to pin -dl tasks to CPUs via
cpusets example added).
The development is taking place at:
https://github.com/jlelli/sched-deadline
Main branches:
- sched-dl-V7: this patchset on top of tip/master.
- mainline-dl: tracking tip/master (raw commits);
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). It is now supported by
the S(o)OS EU-funded project (http://www.soos-project.eu/).
It has also some users, both in academic and applied research. We got
positive feedbacks from Ericsson, Wind River, Porto (ISEP), Trento,
Lund and Malardalen universities.
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
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 | 195 ++++
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 | 152 ++-
include/linux/syscalls.h | 7 +
include/uapi/linux/sched.h | 1 +
kernel/fork.c | 8 +-
kernel/futex.c | 2 +
kernel/hrtimer.c | 2 +-
kernel/rtmutex-debug.c | 8 +-
kernel/rtmutex.c | 163 ++-
kernel/rtmutex_common.h | 22 +-
kernel/sched/Makefile | 4 +-
kernel/sched/core.c | 657 ++++++++++-
kernel/sched/cpudeadline.c | 208 ++++
kernel/sched/cpudeadline.h | 33 +
kernel/sched/deadline.c | 1658 ++++++++++++++++++++++++++++
kernel/sched/debug.c | 46 +
kernel/sched/rt.c | 2 +-
kernel/sched/sched.h | 146 +++
kernel/sched/stop_task.c | 2 +-
kernel/sysctl.c | 7 +
kernel/trace/trace_sched_wakeup.c | 44 +-
kernel/trace/trace_selftest.c | 28 +-
29 files changed, 3317 insertions(+), 120 deletions(-)
create mode 100644 Documentation/scheduler/sched-deadline.txt
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
^ permalink raw reply [flat|nested] 19+ messages in thread
* [PATCH 01/14] sched: add sched_class->task_dead.
2013-02-11 18:50 [PATCH 00/14] sched: SCHED_DEADLINE v7 Juri Lelli
@ 2013-02-11 18:50 ` Juri Lelli
2013-02-11 18:50 ` [PATCH 02/14] sched: add extended scheduling interface Juri Lelli
` (12 subsequent siblings)
13 siblings, 0 replies; 19+ messages in thread
From: Juri Lelli @ 2013-02-11 18:50 UTC (permalink / raw)
To: peterz, tglx
Cc: mingo, rostedt, oleg, fweisbec, darren, johan.eker, p.faure,
linux-kernel, claudio, michael, fchecconi, tommaso.cucinotta,
juri.lelli, nicola.manica, luca.abeni, dhaval.giani, hgu1972,
paulmck, raistlin, insop.song, liming.wang, jkacur,
harald.gustafsson, vincent.guittot
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>
---
include/linux/sched.h | 1 +
kernel/sched/core.c | 3 +++
2 files changed, 4 insertions(+)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index d211247..640c741 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1104,6 +1104,7 @@ 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);
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 26058d0..7e99105 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1843,6 +1843,9 @@ 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.
--
1.7.9.5
^ permalink raw reply related [flat|nested] 19+ messages in thread
* [PATCH 02/14] sched: add extended scheduling interface.
2013-02-11 18:50 [PATCH 00/14] sched: SCHED_DEADLINE v7 Juri Lelli
2013-02-11 18:50 ` [PATCH 01/14] sched: add sched_class->task_dead Juri Lelli
@ 2013-02-11 18:50 ` Juri Lelli
2013-02-11 18:50 ` [PATCH 03/14] sched: SCHED_DEADLINE structures & implementation Juri Lelli
` (11 subsequent siblings)
13 siblings, 0 replies; 19+ messages in thread
From: Juri Lelli @ 2013-02-11 18:50 UTC (permalink / raw)
To: peterz, tglx
Cc: mingo, rostedt, oleg, fweisbec, darren, johan.eker, p.faure,
linux-kernel, claudio, michael, fchecconi, tommaso.cucinotta,
juri.lelli, nicola.manica, luca.abeni, dhaval.giani, hgu1972,
paulmck, raistlin, insop.song, liming.wang, jkacur,
harald.gustafsson, vincent.guittot
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 21a2700..8e2ebbe 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 4da7cde..4135470 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)
/* 378 for kcmp */
#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 a4fda4e..510a536 100644
--- a/arch/arm/kernel/calls.S
+++ b/arch/arm/kernel/calls.S
@@ -389,6 +389,9 @@
CALL(sys_process_vm_writev)
CALL(sys_ni_syscall) /* reserved for 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 28e3fa9..f9b0c72 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 dc97328..b3fac25 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 640c741..d779ecf 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -54,6 +54,54 @@ 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;
@@ -2136,6 +2184,8 @@ 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 45e2db2..f215161 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;
@@ -334,11 +335,17 @@ 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 7e99105..589ac5e 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3776,7 +3776,8 @@ 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;
@@ -3939,10 +3940,20 @@ 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, ¶m2, 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.
@@ -3957,7 +3968,10 @@ 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, ¶m2, false);
}
static int
@@ -3982,6 +3996,31 @@ 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.
@@ -3999,6 +4038,21 @@ 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.
@@ -4009,6 +4063,17 @@ 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.
*/
@@ -4072,6 +4137,45 @@ 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
^ permalink raw reply related [flat|nested] 19+ messages in thread
* [PATCH 03/14] sched: SCHED_DEADLINE structures & implementation.
2013-02-11 18:50 [PATCH 00/14] sched: SCHED_DEADLINE v7 Juri Lelli
2013-02-11 18:50 ` [PATCH 01/14] sched: add sched_class->task_dead Juri Lelli
2013-02-11 18:50 ` [PATCH 02/14] sched: add extended scheduling interface Juri Lelli
@ 2013-02-11 18:50 ` Juri Lelli
2013-02-11 18:50 ` [PATCH 04/14] sched: SCHED_DEADLINE SMP-related data structures & logic Juri Lelli
` (10 subsequent siblings)
13 siblings, 0 replies; 19+ messages in thread
From: Juri Lelli @ 2013-02-11 18:50 UTC (permalink / raw)
To: peterz, tglx
Cc: mingo, rostedt, oleg, fweisbec, darren, johan.eker, p.faure,
linux-kernel, claudio, michael, fchecconi, tommaso.cucinotta,
juri.lelli, nicola.manica, luca.abeni, dhaval.giani, hgu1972,
paulmck, raistlin, insop.song, liming.wang, jkacur,
harald.gustafsson, vincent.guittot
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 | 69 +++-
include/uapi/linux/sched.h | 1 +
kernel/fork.c | 4 +-
kernel/hrtimer.c | 2 +-
kernel/sched/Makefile | 2 +-
kernel/sched/core.c | 111 ++++++-
kernel/sched/deadline.c | 692 +++++++++++++++++++++++++++++++++++++++++
kernel/sched/sched.h | 26 ++
kernel/sched/stop_task.c | 2 +-
10 files changed, 888 insertions(+), 23 deletions(-)
create mode 100644 kernel/sched/deadline.c
diff --git a/arch/arm/include/asm/unistd.h b/arch/arm/include/asm/unistd.h
index 8e2ebbe..16f45f6 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 d779ecf..22bb2cf 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -91,6 +91,10 @@ 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;
@@ -1117,6 +1121,7 @@ struct sched_domain;
#else
#define ENQUEUE_WAKING 0
#endif
+#define ENQUEUE_REPLENISH 8
#define DEQUEUE_SLEEP 1
@@ -1269,6 +1274,47 @@ 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;
+};
+
/*
* default timeslice is 100 msecs (used only for SCHED_RR tasks).
* Timeslices get refilled after they expire.
@@ -1305,6 +1351,7 @@ 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: */
@@ -1682,6 +1729,10 @@ static inline void set_numabalancing_state(bool enabled)
* user-space. This allows kernel threads to set their
* priority to a value higher than any user task. Note:
* MAX_RT_PRIO must not be smaller than MAX_USER_RT_PRIO.
+ *
+ * SCHED_DEADLINE tasks has negative priorities, reflecting
+ * the fact that any of them has higher prio than RT and
+ * NORMAL/BATCH tasks.
*/
#define MAX_USER_RT_PRIO 100
@@ -1690,9 +1741,23 @@ static inline void set_numabalancing_state(bool enabled)
#define MAX_PRIO (MAX_RT_PRIO + 40)
#define DEFAULT_PRIO (MAX_RT_PRIO + 20)
+#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);
+}
+
static inline int rt_prio(int prio)
{
- if (unlikely(prio < MAX_RT_PRIO))
+ if ((unsigned)prio < MAX_RT_PRIO)
return 1;
return 0;
}
@@ -2265,7 +2330,7 @@ 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/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 c535f33..e84562d 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1296,7 +1296,9 @@ 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 6db7a5e..3700ba5 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -1586,7 +1586,7 @@ 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 f06d249..56200e6 100644
--- a/kernel/sched/Makefile
+++ b/kernel/sched/Makefile
@@ -11,7 +11,7 @@ ifneq ($(CONFIG_SCHED_OMIT_FRAME_POINTER),y)
CFLAGS_core.o := $(PROFILING) -fno-omit-frame-pointer
endif
-obj-y += core.o clock.o cputime.o idle_task.o fair.o rt.o stop_task.o
+obj-y += core.o clock.o cputime.o idle_task.o fair.o rt.o deadline.o stop_task.o
obj-$(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 589ac5e..9da6008 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -858,7 +858,9 @@ 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);
@@ -1564,6 +1566,12 @@ 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
@@ -1607,7 +1615,7 @@ 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();
@@ -1629,7 +1637,7 @@ 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;
@@ -1646,8 +1654,14 @@ 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);
@@ -1679,6 +1693,7 @@ void sched_fork(struct task_struct *p)
#endif
put_cpu();
+ return 0;
}
/*
@@ -3528,7 +3543,7 @@ 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);
@@ -3560,7 +3575,9 @@ 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;
@@ -3594,9 +3611,9 @@ 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;
}
@@ -3752,7 +3769,9 @@ __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;
@@ -3760,6 +3779,50 @@ __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)
@@ -3796,7 +3859,8 @@ 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;
@@ -3811,7 +3875,8 @@ 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;
/*
@@ -3877,7 +3942,8 @@ 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;
}
@@ -3914,7 +3980,11 @@ 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);
@@ -4014,8 +4084,11 @@ 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;
@@ -4162,7 +4235,10 @@ 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,
@@ -4573,6 +4649,7 @@ 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:
@@ -4598,6 +4675,7 @@ 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:
@@ -7000,6 +7078,7 @@ 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);
@@ -7180,7 +7259,7 @@ 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 fc88644..435005c 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -50,11 +50,23 @@ 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:
*/
@@ -322,6 +334,15 @@ 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
/*
@@ -383,6 +404,7 @@ 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: */
@@ -868,6 +890,7 @@ enum cpuacct_stat_index {
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;
@@ -900,6 +923,8 @@ 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);
#ifdef CONFIG_CGROUP_CPUACCT
@@ -1178,6 +1203,7 @@ 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 da5eb5b..da80047 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
^ permalink raw reply related [flat|nested] 19+ messages in thread
* [PATCH 04/14] sched: SCHED_DEADLINE SMP-related data structures & logic.
2013-02-11 18:50 [PATCH 00/14] sched: SCHED_DEADLINE v7 Juri Lelli
` (2 preceding siblings ...)
2013-02-11 18:50 ` [PATCH 03/14] sched: SCHED_DEADLINE structures & implementation Juri Lelli
@ 2013-02-11 18:50 ` Juri Lelli
2013-02-11 18:50 ` [PATCH 05/14] sched: SCHED_DEADLINE avg_update accounting Juri Lelli
` (9 subsequent siblings)
13 siblings, 0 replies; 19+ messages in thread
From: Juri Lelli @ 2013-02-11 18:50 UTC (permalink / raw)
To: peterz, tglx
Cc: mingo, rostedt, oleg, fweisbec, darren, johan.eker, p.faure,
linux-kernel, claudio, michael, fchecconi, tommaso.cucinotta,
juri.lelli, nicola.manica, luca.abeni, dhaval.giani, hgu1972,
paulmck, raistlin, insop.song, liming.wang, jkacur,
harald.gustafsson, vincent.guittot
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 | 33 ++
5 files changed, 959 insertions(+), 31 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 22bb2cf..ff12481 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1276,7 +1276,6 @@ 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
@@ -1394,6 +1393,7 @@ 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 9da6008..d19235f 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1690,6 +1690,7 @@ 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();
@@ -4865,6 +4866,7 @@ 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);
}
/*
@@ -5592,6 +5594,7 @@ 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);
@@ -5643,8 +5646,10 @@ 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;
@@ -5652,6 +5657,8 @@ 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:
@@ -6977,6 +6984,7 @@ 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 4f02b28..fead07c 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -1809,7 +1809,7 @@ 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 435005c..95ded83 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -341,6 +341,31 @@ 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
@@ -361,6 +386,13 @@ 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.
*/
@@ -914,6 +946,7 @@ extern void sched_init_granularity(void);
extern void update_max_interval(void);
extern void update_group_power(struct sched_domain *sd, int cpu);
extern int update_runtime(struct notifier_block *nfb, unsigned long action, void *hcpu);
+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
^ permalink raw reply related [flat|nested] 19+ messages in thread
* [PATCH 05/14] sched: SCHED_DEADLINE avg_update accounting.
2013-02-11 18:50 [PATCH 00/14] sched: SCHED_DEADLINE v7 Juri Lelli
` (3 preceding siblings ...)
2013-02-11 18:50 ` [PATCH 04/14] sched: SCHED_DEADLINE SMP-related data structures & logic Juri Lelli
@ 2013-02-11 18:50 ` Juri Lelli
2013-02-11 18:50 ` [PATCH 06/14] sched: add period support for -deadline tasks Juri Lelli
` (8 subsequent siblings)
13 siblings, 0 replies; 19+ messages in thread
From: Juri Lelli @ 2013-02-11 18:50 UTC (permalink / raw)
To: peterz, tglx
Cc: mingo, rostedt, oleg, fweisbec, darren, johan.eker, p.faure,
linux-kernel, claudio, michael, fchecconi, tommaso.cucinotta,
juri.lelli, nicola.manica, luca.abeni, dhaval.giani, hgu1972,
paulmck, raistlin, insop.song, liming.wang, jkacur,
harald.gustafsson, vincent.guittot
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
^ permalink raw reply related [flat|nested] 19+ messages in thread
* [PATCH 06/14] sched: add period support for -deadline tasks.
2013-02-11 18:50 [PATCH 00/14] sched: SCHED_DEADLINE v7 Juri Lelli
` (4 preceding siblings ...)
2013-02-11 18:50 ` [PATCH 05/14] sched: SCHED_DEADLINE avg_update accounting Juri Lelli
@ 2013-02-11 18:50 ` Juri Lelli
2013-02-11 18:50 ` [PATCH 07/14] sched: add schedstats " Juri Lelli
` (7 subsequent siblings)
13 siblings, 0 replies; 19+ messages in thread
From: Juri Lelli @ 2013-02-11 18:50 UTC (permalink / raw)
To: peterz, tglx
Cc: mingo, rostedt, oleg, fweisbec, darren, johan.eker, p.faure,
linux-kernel, claudio, michael, fchecconi, tommaso.cucinotta,
juri.lelli, nicola.manica, luca.abeni, dhaval.giani, hgu1972,
paulmck, raistlin, insop.song, liming.wang, jkacur,
harald.gustafsson, vincent.guittot
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 ff12481..4bfda68 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1284,6 +1284,7 @@ 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 d19235f..17a60e4 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1570,6 +1570,7 @@ 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);
@@ -3795,6 +3796,10 @@ __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;
@@ -3808,19 +3813,23 @@ __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
^ permalink raw reply related [flat|nested] 19+ messages in thread
* [PATCH 07/14] sched: add schedstats for -deadline tasks.
2013-02-11 18:50 [PATCH 00/14] sched: SCHED_DEADLINE v7 Juri Lelli
` (5 preceding siblings ...)
2013-02-11 18:50 ` [PATCH 06/14] sched: add period support for -deadline tasks Juri Lelli
@ 2013-02-11 18:50 ` Juri Lelli
2013-02-11 18:50 ` [PATCH 08/14] sched: add latency tracing " Juri Lelli
` (6 subsequent siblings)
13 siblings, 0 replies; 19+ messages in thread
From: Juri Lelli @ 2013-02-11 18:50 UTC (permalink / raw)
To: peterz, tglx
Cc: mingo, rostedt, oleg, fweisbec, darren, johan.eker, p.faure,
linux-kernel, claudio, michael, fchecconi, tommaso.cucinotta,
juri.lelli, nicola.manica, luca.abeni, dhaval.giani, hgu1972,
paulmck, raistlin, insop.song, liming.wang, jkacur,
harald.gustafsson, vincent.guittot
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 4bfda68..d4f8f9e 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1274,6 +1274,15 @@ 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;
@@ -1313,6 +1322,10 @@ 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
};
/*
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 7ae4c4c..487d8df 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -258,6 +258,45 @@ 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)
@@ -325,6 +364,7 @@ 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);
@@ -476,6 +516,12 @@ 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 95ded83..5364c3e 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -342,6 +342,8 @@ struct dl_rq {
unsigned long dl_nr_running;
+ u64 exec_clock;
+
#ifdef CONFIG_SMP
/*
* Deadline values of the currently executing and the
@@ -368,6 +370,11 @@ 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
/*
@@ -1236,7 +1243,7 @@ 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
^ permalink raw reply related [flat|nested] 19+ messages in thread
* [PATCH 08/14] sched: add latency tracing for -deadline tasks.
2013-02-11 18:50 [PATCH 00/14] sched: SCHED_DEADLINE v7 Juri Lelli
` (6 preceding siblings ...)
2013-02-11 18:50 ` [PATCH 07/14] sched: add schedstats " Juri Lelli
@ 2013-02-11 18:50 ` Juri Lelli
2013-02-11 18:50 ` [PATCH 09/14] rtmutex: turn the plist into an rb-tree Juri Lelli
` (5 subsequent siblings)
13 siblings, 0 replies; 19+ messages in thread
From: Juri Lelli @ 2013-02-11 18:50 UTC (permalink / raw)
To: peterz, tglx
Cc: mingo, rostedt, oleg, fweisbec, darren, johan.eker, p.faure,
linux-kernel, claudio, michael, fchecconi, tommaso.cucinotta,
juri.lelli, nicola.manica, luca.abeni, dhaval.giani, hgu1972,
paulmck, raistlin, insop.song, liming.wang, jkacur,
harald.gustafsson, vincent.guittot
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 9fe45fc..0a63eab 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;
@@ -429,9 +430,17 @@ 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();
@@ -443,7 +452,7 @@ 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 */
@@ -551,16 +560,25 @@ 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)
{
stop_wakeup_tracer(tr);
@@ -623,6 +641,20 @@ 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;
@@ -635,6 +667,10 @@ __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 4762316..c15c445 100644
--- a/kernel/trace/trace_selftest.c
+++ b/kernel/trace/trace_selftest.c
@@ -1016,11 +1016,17 @@ 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, ¶m);
+ sched_setscheduler2(current, SCHED_DEADLINE, ¶mx);
/* Make it know we have a new prio */
complete(x);
@@ -1034,8 +1040,8 @@ 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);
}
@@ -1048,21 +1054,21 @@ 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
^ permalink raw reply related [flat|nested] 19+ messages in thread
* [PATCH 09/14] rtmutex: turn the plist into an rb-tree.
2013-02-11 18:50 [PATCH 00/14] sched: SCHED_DEADLINE v7 Juri Lelli
` (7 preceding siblings ...)
2013-02-11 18:50 ` [PATCH 08/14] sched: add latency tracing " Juri Lelli
@ 2013-02-11 18:50 ` Juri Lelli
2013-02-11 18:50 ` [PATCH 10/14] sched: drafted deadline inheritance logic Juri Lelli
` (4 subsequent siblings)
13 siblings, 0 replies; 19+ messages in thread
From: Juri Lelli @ 2013-02-11 18:50 UTC (permalink / raw)
To: peterz, tglx
Cc: mingo, rostedt, oleg, fweisbec, darren, johan.eker, p.faure,
linux-kernel, claudio, michael, fchecconi, tommaso.cucinotta,
juri.lelli, nicola.manica, luca.abeni, dhaval.giani, hgu1972,
paulmck, raistlin, insop.song, liming.wang, jkacur,
harald.gustafsson, vincent.guittot
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 6d087c5..7d2634b 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -10,6 +10,7 @@
#include <linux/pid_namespace.h>
#include <linux/user_namespace.h>
#include <linux/securebits.h>
+#include <linux/rbtree.h>
#include <net/net_namespace.h>
#ifdef CONFIG_SMP
@@ -143,6 +144,14 @@ 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)
@@ -210,6 +219,7 @@ extern struct task_group root_task_group;
INIT_TRACE_RECURSION \
INIT_TASK_RCU_PREEMPT(tsk) \
INIT_CPUSET_SEQ \
+ INIT_RT_MUTEXES(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 d4f8f9e..132db70 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>
@@ -1548,7 +1549,8 @@ 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 e84562d..4d31e6a 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1095,7 +1095,8 @@ 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 19eb089..16ea62d 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -2312,6 +2312,8 @@ 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 16502d3..41c18f5 100644
--- a/kernel/rtmutex-debug.c
+++ b/kernel/rtmutex-debug.c
@@ -23,7 +23,7 @@
#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>
@@ -56,7 +56,7 @@ 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);
}
@@ -153,16 +153,12 @@ 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 a242e69..227deb4 100644
--- a/kernel/rtmutex.c
+++ b/kernel/rtmutex.c
@@ -90,10 +90,104 @@ 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)
@@ -101,7 +195,7 @@ 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);
}
@@ -219,7 +313,7 @@ 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;
@@ -240,9 +334,9 @@ 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);
@@ -266,17 +360,15 @@ 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);
}
@@ -341,7 +433,7 @@ 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;
}
@@ -355,7 +447,7 @@ 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;
}
@@ -365,8 +457,7 @@ 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);
}
@@ -402,13 +493,11 @@ 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;
@@ -419,8 +508,8 @@ 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)
@@ -472,7 +561,7 @@ 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, ¤t->pi_waiters);
+ rt_mutex_dequeue_pi(current, waiter);
rt_mutex_set_owner(lock, NULL);
@@ -496,7 +585,7 @@ static void remove_waiter(struct rt_mutex *lock,
int chain_walk = 0;
raw_spin_lock_irqsave(¤t->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(¤t->pi_lock, flags);
@@ -507,13 +596,13 @@ 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);
@@ -523,8 +612,6 @@ 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;
@@ -551,7 +638,7 @@ 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;
}
@@ -624,6 +711,8 @@ 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);
@@ -890,7 +979,8 @@ 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 17a60e4..92f962d 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7163,10 +7163,6 @@ 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
^ permalink raw reply related [flat|nested] 19+ messages in thread
* [PATCH 10/14] sched: drafted deadline inheritance logic.
2013-02-11 18:50 [PATCH 00/14] sched: SCHED_DEADLINE v7 Juri Lelli
` (8 preceding siblings ...)
2013-02-11 18:50 ` [PATCH 09/14] rtmutex: turn the plist into an rb-tree Juri Lelli
@ 2013-02-11 18:50 ` Juri Lelli
2013-02-11 18:50 ` [PATCH 11/14] sched: add bandwidth management for sched_dl Juri Lelli
` (3 subsequent siblings)
13 siblings, 0 replies; 19+ messages in thread
From: Juri Lelli @ 2013-02-11 18:50 UTC (permalink / raw)
To: peterz, tglx
Cc: mingo, rostedt, oleg, fweisbec, darren, johan.eker, p.faure,
linux-kernel, claudio, michael, fchecconi, tommaso.cucinotta,
juri.lelli, nicola.manica, luca.abeni, dhaval.giani, hgu1972,
paulmck, raistlin, insop.song, liming.wang, jkacur,
harald.gustafsson, vincent.guittot
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 | 9 ++++-
kernel/fork.c | 1 +
kernel/rtmutex.c | 13 +++++--
kernel/sched/core.c | 34 +++++++++++++++---
kernel/sched/deadline.c | 91 +++++++++++++++++++++++++++--------------------
kernel/sched/sched.h | 14 ++++++++
6 files changed, 116 insertions(+), 46 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 132db70..dc3254e 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1315,8 +1315,12 @@ 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
@@ -1553,6 +1557,8 @@ 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
@@ -2237,6 +2243,7 @@ extern unsigned int sysctl_sched_cfs_bandwidth_slice;
#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 4d31e6a..2ed79ea 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1098,6 +1098,7 @@ 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 227deb4..b42aae1 100644
--- a/kernel/rtmutex.c
+++ b/kernel/rtmutex.c
@@ -199,6 +199,14 @@ 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.
*
@@ -208,7 +216,7 @@ 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);
}
@@ -638,7 +646,8 @@ 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 92f962d..e9c76d9 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3541,7 +3541,7 @@ 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;
@@ -3568,6 +3568,7 @@ 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;
@@ -3577,19 +3578,42 @@ 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 5364c3e..f704c39 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -67,6 +67,20 @@ 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
^ permalink raw reply related [flat|nested] 19+ messages in thread
* [PATCH 11/14] sched: add bandwidth management for sched_dl.
2013-02-11 18:50 [PATCH 00/14] sched: SCHED_DEADLINE v7 Juri Lelli
` (9 preceding siblings ...)
2013-02-11 18:50 ` [PATCH 10/14] sched: drafted deadline inheritance logic Juri Lelli
@ 2013-02-11 18:50 ` Juri Lelli
2013-02-11 18:50 ` [PATCH 12/14] sched: make dl_bw a sub-quota of rt_bw Juri Lelli
` (2 subsequent siblings)
13 siblings, 0 replies; 19+ messages in thread
From: Juri Lelli @ 2013-02-11 18:50 UTC (permalink / raw)
To: peterz, tglx
Cc: mingo, rostedt, oleg, fweisbec, darren, johan.eker, p.faure,
linux-kernel, claudio, michael, fchecconi, tommaso.cucinotta,
juri.lelli, nicola.manica, luca.abeni, dhaval.giani, hgu1972,
paulmck, raistlin, insop.song, liming.wang, jkacur,
harald.gustafsson, vincent.guittot
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 | 8 +
kernel/sched/core.c | 431 ++++++++++++++++++++++++++++++++++++++++++++---
kernel/sched/deadline.c | 50 +++++-
kernel/sched/sched.h | 74 +++++++-
kernel/sysctl.c | 14 ++
5 files changed, 543 insertions(+), 34 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index dc3254e..f88abef 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1295,6 +1295,7 @@ 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,
@@ -2218,6 +2219,13 @@ int sched_rt_handler(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp,
loff_t *ppos);
+extern unsigned int sysctl_sched_dl_period;
+extern int sysctl_sched_dl_runtime;
+
+int sched_dl_handler(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp,
+ loff_t *ppos);
+
#ifdef CONFIG_SCHED_AUTOGROUP
extern unsigned int sysctl_sched_autogroup_enabled;
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index e9c76d9..7fbcf72 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;
+
/*
@@ -1698,6 +1707,96 @@ 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.
*
@@ -3824,6 +3923,7 @@ __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;
@@ -3845,15 +3945,18 @@ __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));
}
/*
@@ -3982,8 +4085,8 @@ 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.
@@ -3994,8 +4097,34 @@ 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)) {
@@ -4003,6 +4132,19 @@ 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)
@@ -4328,6 +4470,24 @@ 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:
@@ -4970,6 +5130,42 @@ 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
@@ -5001,6 +5197,13 @@ 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.
*/
@@ -5684,6 +5887,8 @@ 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;
@@ -7089,6 +7294,8 @@ 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,
@@ -7482,16 +7689,6 @@ 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.
@@ -7665,10 +7862,48 @@ 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)
@@ -7683,6 +7918,10 @@ 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);
@@ -7705,19 +7944,19 @@ 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;
@@ -7725,12 +7964,96 @@ 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_rt_handler(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp,
loff_t *ppos)
@@ -7761,6 +8084,64 @@ 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
/* return corresponding task_group object of a cgroup */
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 f704c39..0bf10e8 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -43,6 +43,13 @@ extern __read_mostly int scheduler_running;
*/
#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)
@@ -67,7 +74,7 @@ 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;
}
@@ -75,8 +82,8 @@ 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);
}
@@ -96,6 +103,48 @@ 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;
@@ -381,6 +430,8 @@ struct dl_rq {
*/
struct rb_root pushable_dl_tasks_root;
struct rb_node *pushable_dl_tasks_leftmost;
+#else
+ struct dl_bw dl_bw;
#endif
};
@@ -412,6 +463,7 @@ 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
@@ -763,7 +815,18 @@ 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)
{
@@ -970,6 +1033,7 @@ extern int update_runtime(struct notifier_block *nfb, unsigned long action, 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);
@@ -977,8 +1041,12 @@ 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);
#ifdef CONFIG_CGROUP_CPUACCT
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index c88878d..a387047 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -403,6 +403,20 @@ static struct ctl_table kern_table[] = {
.mode = 0644,
.proc_handler = sched_rt_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",
--
1.7.9.5
^ permalink raw reply related [flat|nested] 19+ messages in thread
* [PATCH 12/14] sched: make dl_bw a sub-quota of rt_bw
2013-02-11 18:50 [PATCH 00/14] sched: SCHED_DEADLINE v7 Juri Lelli
` (10 preceding siblings ...)
2013-02-11 18:50 ` [PATCH 11/14] sched: add bandwidth management for sched_dl Juri Lelli
@ 2013-02-11 18:50 ` Juri Lelli
2013-02-11 18:50 ` [PATCH 13/14] sched: speed up -dl pushes with a push-heap Juri Lelli
2013-02-11 18:50 ` [PATCH 14/14] sched: add sched_dl documentation Juri Lelli
13 siblings, 0 replies; 19+ messages in thread
From: Juri Lelli @ 2013-02-11 18:50 UTC (permalink / raw)
To: peterz, tglx
Cc: mingo, rostedt, oleg, fweisbec, darren, johan.eker, p.faure,
linux-kernel, claudio, michael, fchecconi, tommaso.cucinotta,
juri.lelli, nicola.manica, luca.abeni, dhaval.giani, hgu1972,
paulmck, raistlin, insop.song, liming.wang, jkacur,
harald.gustafsson, vincent.guittot
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.h | 1 -
kernel/sched/core.c | 282 ++++++++++++++++++++++-------------------------
kernel/sched/deadline.c | 3 +-
kernel/sched/sched.h | 22 ++--
kernel/sysctl.c | 7 --
5 files changed, 143 insertions(+), 172 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index f88abef..66cf7f3 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2219,7 +2219,6 @@ int sched_rt_handler(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp,
loff_t *ppos);
-extern unsigned int sysctl_sched_dl_period;
extern int sysctl_sched_dl_runtime;
int sched_dl_handler(struct ctl_table *table, int write,
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 7fbcf72..8628438 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;
@@ -7295,7 +7294,7 @@ 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());
+ global_rt_period(), global_dl_runtime());
#ifdef CONFIG_RT_GROUP_SCHED
init_rt_bandwidth(&root_task_group.rt_bandwidth,
@@ -7689,6 +7688,93 @@ 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 = actual_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 = global_dl_runtime();
+ if (global_dl_runtime() == RUNTIME_INF ||
+ global_rt_runtime() == RUNTIME_INF)
+ new_bw = -1;
+ else {
+ new_bw = to_ratio(global_rt_period(),
+ actual_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.
@@ -7862,48 +7948,10 @@ 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)
@@ -7918,9 +7966,13 @@ 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);
@@ -7944,18 +7996,27 @@ 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;
@@ -7964,48 +8025,12 @@ 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))
@@ -8016,40 +8041,17 @@ 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 = actual_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;
}
@@ -8061,6 +8063,7 @@ 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;
@@ -8070,6 +8073,8 @@ 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;
@@ -8077,7 +8082,11 @@ 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);
@@ -8089,12 +8098,11 @@ 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);
@@ -8105,33 +8113,9 @@ 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..c71e5ff 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -51,7 +51,6 @@ static inline int is_leftmost(struct task_struct *p, struct dl_rq *dl_rq)
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;
}
@@ -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 0bf10e8..7de601d 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -104,20 +104,20 @@ 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
@@ -130,7 +130,6 @@ 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)
@@ -140,10 +139,12 @@ 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;
@@ -815,11 +816,6 @@ 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)
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index a387047..287c09b 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -404,13 +404,6 @@ static struct ctl_table kern_table[] = {
.proc_handler = sched_rt_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
^ permalink raw reply related [flat|nested] 19+ messages in thread
* [PATCH 13/14] sched: speed up -dl pushes with a push-heap.
2013-02-11 18:50 [PATCH 00/14] sched: SCHED_DEADLINE v7 Juri Lelli
` (11 preceding siblings ...)
2013-02-11 18:50 ` [PATCH 12/14] sched: make dl_bw a sub-quota of rt_bw Juri Lelli
@ 2013-02-11 18:50 ` Juri Lelli
2013-02-11 18:50 ` [PATCH 14/14] sched: add sched_dl documentation Juri Lelli
13 siblings, 0 replies; 19+ messages in thread
From: Juri Lelli @ 2013-02-11 18:50 UTC (permalink / raw)
To: peterz, tglx
Cc: mingo, rostedt, oleg, fweisbec, darren, johan.eker, p.faure,
linux-kernel, claudio, michael, fchecconi, tommaso.cucinotta,
juri.lelli, nicola.manica, luca.abeni, dhaval.giani, hgu1972,
paulmck, raistlin, insop.song, liming.wang, jkacur,
harald.gustafsson, vincent.guittot
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 | 208 ++++++++++++++++++++++++++++++++++++++++++++
kernel/sched/cpudeadline.h | 33 +++++++
kernel/sched/deadline.c | 53 +++--------
kernel/sched/sched.h | 2 +
6 files changed, 261 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 56200e6..84a25cd 100644
--- a/kernel/sched/Makefile
+++ b/kernel/sched/Makefile
@@ -12,7 +12,7 @@ CFLAGS_core.o := $(PROFILING) -fno-omit-frame-pointer
endif
obj-y += core.o clock.o cputime.o idle_task.o fair.o rt.o deadline.o stop_task.o
-obj-$(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 8628438..fcea3dd 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5829,6 +5829,7 @@ 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);
@@ -5887,6 +5888,8 @@ 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..cf90153
--- /dev/null
+++ b/kernel/sched/cpudeadline.c
@@ -0,0 +1,208 @@
+/*
+ * 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 != -1);
+
+ 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 */
+ 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 c71e5ff..0ece746 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 7de601d..b15679c 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -5,6 +5,7 @@
#include <linux/stop_machine.h>
#include "cpupri.h"
+#include "cpudeadline.h"
extern __read_mostly int scheduler_running;
@@ -465,6 +466,7 @@ 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
^ permalink raw reply related [flat|nested] 19+ messages in thread
* [PATCH 14/14] sched: add sched_dl documentation.
2013-02-11 18:50 [PATCH 00/14] sched: SCHED_DEADLINE v7 Juri Lelli
` (12 preceding siblings ...)
2013-02-11 18:50 ` [PATCH 13/14] sched: speed up -dl pushes with a push-heap Juri Lelli
@ 2013-02-11 18:50 ` Juri Lelli
13 siblings, 0 replies; 19+ messages in thread
From: Juri Lelli @ 2013-02-11 18:50 UTC (permalink / raw)
To: peterz, tglx
Cc: mingo, rostedt, oleg, fweisbec, darren, johan.eker, p.faure,
linux-kernel, claudio, michael, fchecconi, tommaso.cucinotta,
juri.lelli, nicola.manica, luca.abeni, dhaval.giani, hgu1972,
paulmck, raistlin, insop.song, liming.wang, jkacur,
harald.gustafsson, vincent.guittot
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 | 195 ++++++++++++++++++++++++++++
kernel/sched/deadline.c | 3 +-
2 files changed, 197 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..9ba02631
--- /dev/null
+++ b/Documentation/scheduler/sched-deadline.txt
@@ -0,0 +1,195 @@
+ 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 / sched_rt_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.
+ This is done by writing -1 in /proc/sys/kernel/sched_dl_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 0ece746..e7a1d34 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
^ permalink raw reply related [flat|nested] 19+ messages in thread
* Re: [PATCH 14/14] sched: add sched_dl documentation.
2013-11-07 16:44 ` Randy Dunlap
@ 2013-11-08 9:25 ` Juri Lelli
0 siblings, 0 replies; 19+ messages in thread
From: Juri Lelli @ 2013-11-08 9:25 UTC (permalink / raw)
To: Randy Dunlap, peterz, tglx
Cc: mingo, rostedt, oleg, fweisbec, darren, johan.eker, p.faure,
linux-kernel, claudio, michael, fchecconi, tommaso.cucinotta,
nicola.manica, luca.abeni, dhaval.giani, hgu1972, paulmck,
raistlin, insop.song, liming.wang, jkacur, harald.gustafsson,
vincent.guittot, bruce.ashfield
Hi,
On 11/07/2013 05:44 PM, Randy Dunlap wrote:
> Hi,
>
> Just a few minor edits...
>
Thanks!
Best,
- Juri
> On 11/07/13 05:47, Juri Lelli wrote:
>> 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
>
> s/among/within/
>
>> + 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:
>
> while stays
>
>> +
>> + 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
>
> With rt_period equal to 1000000,
>
>> +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
>
> points of view,
>
>> + 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.
>
>
^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: [PATCH 14/14] sched: add sched_dl documentation.
2013-11-07 13:47 Juri Lelli
@ 2013-11-07 16:44 ` Randy Dunlap
2013-11-08 9:25 ` Juri Lelli
0 siblings, 1 reply; 19+ messages in thread
From: Randy Dunlap @ 2013-11-07 16:44 UTC (permalink / raw)
To: Juri Lelli, peterz, tglx
Cc: mingo, rostedt, oleg, fweisbec, darren, johan.eker, p.faure,
linux-kernel, claudio, michael, fchecconi, tommaso.cucinotta,
nicola.manica, luca.abeni, dhaval.giani, hgu1972, paulmck,
raistlin, insop.song, liming.wang, jkacur, harald.gustafsson,
vincent.guittot, bruce.ashfield
Hi,
Just a few minor edits...
On 11/07/13 05:47, Juri Lelli wrote:
> 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
s/among/within/
> + 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:
while stays
> +
> + 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
With rt_period equal to 1000000,
> +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
points of view,
> + 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.
--
~Randy
^ permalink raw reply [flat|nested] 19+ messages in thread
* [PATCH 14/14] sched: add sched_dl documentation.
@ 2013-11-07 13:47 Juri Lelli
2013-11-07 16:44 ` Randy Dunlap
0 siblings, 1 reply; 19+ messages in thread
From: Juri Lelli @ 2013-11-07 13:47 UTC (permalink / raw)
To: peterz, tglx
Cc: mingo, rostedt, oleg, fweisbec, darren, johan.eker, p.faure,
linux-kernel, claudio, michael, fchecconi, tommaso.cucinotta,
juri.lelli, nicola.manica, luca.abeni, dhaval.giani, hgu1972,
paulmck, raistlin, insop.song, liming.wang, jkacur,
harald.gustafsson, vincent.guittot, bruce.ashfield
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 9c1fd55..2e762b5 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -350,7 +350,8 @@ 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
^ permalink raw reply related [flat|nested] 19+ messages in thread
* [PATCH 14/14] sched: add sched_dl documentation.
2013-10-14 10:43 [PATCH 00/14] sched: SCHED_DEADLINE v8 Juri Lelli
@ 2013-10-14 10:43 ` Juri Lelli
0 siblings, 0 replies; 19+ messages in thread
From: Juri Lelli @ 2013-10-14 10:43 UTC (permalink / raw)
To: peterz, tglx
Cc: mingo, rostedt, oleg, fweisbec, darren, johan.eker, p.faure,
linux-kernel, claudio, michael, fchecconi, tommaso.cucinotta,
juri.lelli, nicola.manica, luca.abeni, dhaval.giani, hgu1972,
paulmck, raistlin, insop.song, liming.wang, jkacur,
harald.gustafsson, vincent.guittot, bruce.ashfield
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
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2013-02-11 18:50 [PATCH 00/14] sched: SCHED_DEADLINE v7 Juri Lelli
2013-02-11 18:50 ` [PATCH 01/14] sched: add sched_class->task_dead Juri Lelli
2013-02-11 18:50 ` [PATCH 02/14] sched: add extended scheduling interface Juri Lelli
2013-02-11 18:50 ` [PATCH 03/14] sched: SCHED_DEADLINE structures & implementation Juri Lelli
2013-02-11 18:50 ` [PATCH 04/14] sched: SCHED_DEADLINE SMP-related data structures & logic Juri Lelli
2013-02-11 18:50 ` [PATCH 05/14] sched: SCHED_DEADLINE avg_update accounting Juri Lelli
2013-02-11 18:50 ` [PATCH 06/14] sched: add period support for -deadline tasks Juri Lelli
2013-02-11 18:50 ` [PATCH 07/14] sched: add schedstats " Juri Lelli
2013-02-11 18:50 ` [PATCH 08/14] sched: add latency tracing " Juri Lelli
2013-02-11 18:50 ` [PATCH 09/14] rtmutex: turn the plist into an rb-tree Juri Lelli
2013-02-11 18:50 ` [PATCH 10/14] sched: drafted deadline inheritance logic Juri Lelli
2013-02-11 18:50 ` [PATCH 11/14] sched: add bandwidth management for sched_dl Juri Lelli
2013-02-11 18:50 ` [PATCH 12/14] sched: make dl_bw a sub-quota of rt_bw Juri Lelli
2013-02-11 18:50 ` [PATCH 13/14] sched: speed up -dl pushes with a push-heap Juri Lelli
2013-02-11 18:50 ` [PATCH 14/14] sched: add sched_dl documentation Juri Lelli
2013-10-14 10:43 [PATCH 00/14] sched: SCHED_DEADLINE v8 Juri Lelli
2013-10-14 10:43 ` [PATCH 14/14] sched: add sched_dl documentation Juri Lelli
2013-11-07 13:47 Juri Lelli
2013-11-07 16:44 ` Randy Dunlap
2013-11-08 9:25 ` Juri Lelli
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