[PATCH v9 0/6] Implement qspinlock/pv-qspinlock on ppc

[PATCH v9 0/6] Implement qspinlock/pv-qspinlock on ppc

[Pan Xinhui]

Hi All,
  this is the fairlock patchset. You can apply them and build successfully.
patches are based on linux-next
  qspinlock can avoid waiter starved issue. It has about the same speed in
single-thread and it can be much faster in high contention situations
especially when the spinlock is embedded within the data structure to be
protected.

v8 -> v9:
	mv qspinlocm config entry to platforms/kconfig
	fix comments and remove unnecessary codes, thanks boqun reviewing.
v7 -> v8:
	add one patch to drop a function call under native qspinlock unlock.
	Enabling qspinlock or not is a complier option now.
	rebase onto linux-next(4.9-rc7)
v6 -> v7:
	rebase onto 4.8-rc4
v1 -> v6:
	too many details. snip. 

some benchmark result below

perf bench
these numbers are ops per sec, So the higher the better.
*******************************************
on pSeries with 32 vcpus, 32Gb memory, pHyp.
------------------------------------------------------------------------------------
	test case		| pv-qspinlock  |  qspinlock 	| current-spinlock
------------------------------------------------------------------------------------
futex hash			| 618572	| 552332	| 553788
futex lock-pi			| 364		| 364		| 364
sched pipe			| 78984		| 76060		| 81454
------------------------------------------------------------------------------------

unix bench:
these numbers are scores, So the higher the better.
************************************************
on PowerNV with 16 cores(cpus) (smt off), 32Gb memory:
-------------
pv-qspinlock and qspinlock have very similar results because pv-qspinlock use native version
which is only having one callback overhead
------------------------------------------------------------------------------------
	test case		| pv-qspinlock and qspinlock | current-spinlock
------------------------------------------------------------------------------------
Execl Throughput                               761.1             761.4
File Copy 1024 bufsize 2000 maxblocks         1259.8            1286.6
File Copy 256 bufsize 500 maxblocks            782.2             790.3
File Copy 4096 bufsize 8000 maxblocks         2741.5            2817.4
Pipe Throughput                               1063.2            1036.7
Pipe-based Context Switching                   284.7             281.1
Process Creation                               679.6             649.1
Shell Scripts (1 concurrent)                  1933.2            1922.9
Shell Scripts (8 concurrent)                  5003.3            4899.8
System Call Overhead                           900.6             896.8
                                             ==========================
System Benchmarks Index Score                 1139.3 	 	 1133.0
--------------------------------------------------------------------------- ---------

*******************************************
on pSeries with 32 vcpus, 32Gb memory, pHyp.
------------------------------------------------------------------------------------
	test case		|	pv-qspinlock |	qspinlock | current-spinlock
------------------------------------------------------------------------------------
Execl Throughput                             877.1         891.2         872.8
File Copy 1024 bufsize 2000 maxblocks       1390.4        1399.2        1395.0
File Copy 256 bufsize 500 maxblocks          882.4         889.5         881.8
File Copy 4096 bufsize 8000 maxblocks       3112.3        3113.4        3121.7
Pipe Throughput                             1095.8        1162.6        1158.5
Pipe-based Context Switching                 194.9         192.7         200.7
Process Creation                             518.4         526.4         509.1
Shell Scripts (1 concurrent)                1401.9        1413.9        1402.2
Shell Scripts (8 concurrent)                3215.6        3246.6        3229.1
System Call Overhead                         833.2         892.4         888.1
                                          ====================================
System Benchmarks Index Score               1033.7        1052.5        1047.8
------------------------------------------------------------------------------------

******************************************
on pSeries with 32 vcpus, 16Gb memory, KVM.
------------------------------------------------------------------------------------
	test case		|	pv-qspinlock |	qspinlock | current-spinlock
------------------------------------------------------------------------------------
Execl Throughput                             497.4        518.7         497.8
File Copy 1024 bufsize 2000 maxblocks       1368.8       1390.1        1343.3
File Copy 256 bufsize 500 maxblocks          857.7        859.8         831.4
File Copy 4096 bufsize 8000 maxblocks       2851.7       2838.1        2785.5
Pipe Throughput                             1221.9       1265.3        1250.4
Pipe-based Context Switching                 529.8        578.1         564.2
Process Creation                             408.4        421.6         287.6
Shell Scripts (1 concurrent)                1201.8       1215.3        1185.8
Shell Scripts (8 concurrent)                3758.4       3799.3        3878.9
System Call Overhead                        1008.3       1122.6        1134.2
                                          =====================================
System Benchmarks Index Score               1072.0       1108.9        1050.6
------------------------------------------------------------------------------------



Pan Xinhui (6):
  powerpc/qspinlock: powerpc support qspinlock
  powerpc: platforms/Kconfig: Add qspinlock build config
  powerpc: lib/locks.c: Add cpu yield/wake helper function
  powerpc/pv-qspinlock: powerpc support pv-qspinlock
  powerpc: pSeries: Add pv-qspinlock build config/make
  powerpc/pv-qspinlock: Optimise native unlock path

 arch/powerpc/include/asm/qspinlock.h               |  93 ++++++++++++
 arch/powerpc/include/asm/qspinlock_paravirt.h      |  52 +++++++
 .../powerpc/include/asm/qspinlock_paravirt_types.h |  13 ++
 arch/powerpc/include/asm/spinlock.h                |  35 +++--
 arch/powerpc/include/asm/spinlock_types.h          |   4 +
 arch/powerpc/kernel/Makefile                       |   1 +
 arch/powerpc/kernel/paravirt.c                     | 157 +++++++++++++++++++++
 arch/powerpc/lib/locks.c                           | 123 ++++++++++++++++
 arch/powerpc/platforms/Kconfig                     |   9 ++
 arch/powerpc/platforms/pseries/Kconfig             |   8 ++
 arch/powerpc/platforms/pseries/setup.c             |   5 +
 11 files changed, 487 insertions(+), 13 deletions(-)
 create mode 100644 arch/powerpc/include/asm/qspinlock.h
 create mode 100644 arch/powerpc/include/asm/qspinlock_paravirt.h
 create mode 100644 arch/powerpc/include/asm/qspinlock_paravirt_types.h
 create mode 100644 arch/powerpc/kernel/paravirt.c

-- 
2.4.11

[PATCH v9 1/6] powerpc/qspinlock: powerpc support qspinlock

[Pan Xinhui]

This patch add basic code to enable qspinlock on powerpc. qspinlock is
one kind of fairlock implementation. And seen some performance improvement
under some scenarios.

queued_spin_unlock() release the lock by just one write of NULL to the
::locked field which sits at different places in the two endianness
system.

We override some arch_spin_XXX as powerpc has io_sync stuff which makes
sure the io operations are protected by the lock correctly.

There is another special case, see commit
2c610022711 ("locking/qspinlock: Fix spin_unlock_wait() some more")

Signed-off-by: Pan Xinhui <xinhui.pan@linux.vnet.ibm.com>
---
 arch/powerpc/include/asm/qspinlock.h      | 66 +++++++++++++++++++++++++++++++
 arch/powerpc/include/asm/spinlock.h       | 31 +++++++++------
 arch/powerpc/include/asm/spinlock_types.h |  4 ++
 arch/powerpc/lib/locks.c                  | 62 +++++++++++++++++++++++++++++
 4 files changed, 150 insertions(+), 13 deletions(-)
 create mode 100644 arch/powerpc/include/asm/qspinlock.h

diff --git a/arch/powerpc/include/asm/qspinlock.h b/arch/powerpc/include/asm/qspinlock.h
new file mode 100644
index 0000000..4c89256
--- /dev/null
+++ b/arch/powerpc/include/asm/qspinlock.h
@@ -0,0 +1,66 @@
+#ifndef _ASM_POWERPC_QSPINLOCK_H
+#define _ASM_POWERPC_QSPINLOCK_H
+
+#include <asm-generic/qspinlock_types.h>
+
+#define SPIN_THRESHOLD (1 << 15)
+#define queued_spin_unlock queued_spin_unlock
+#define queued_spin_is_locked queued_spin_is_locked
+#define queued_spin_unlock_wait queued_spin_unlock_wait
+
+extern void queued_spin_unlock_wait(struct qspinlock *lock);
+
+static inline u8 *__qspinlock_lock_byte(struct qspinlock *lock)
+{
+	return (u8 *)lock + 3 * IS_BUILTIN(CONFIG_CPU_BIG_ENDIAN);
+}
+
+static inline void queued_spin_unlock(struct qspinlock *lock)
+{
+	/* release semantics is required */
+	smp_store_release(__qspinlock_lock_byte(lock), 0);
+}
+
+static inline int queued_spin_is_locked(struct qspinlock *lock)
+{
+	smp_mb();
+	return atomic_read(&lock->val);
+}
+
+#include <asm-generic/qspinlock.h>
+
+/* we need override it as ppc has io_sync stuff */
+#undef arch_spin_trylock
+#undef arch_spin_lock
+#undef arch_spin_lock_flags
+#undef arch_spin_unlock
+#define arch_spin_trylock arch_spin_trylock
+#define arch_spin_lock arch_spin_lock
+#define arch_spin_lock_flags arch_spin_lock_flags
+#define arch_spin_unlock arch_spin_unlock
+
+static inline int arch_spin_trylock(arch_spinlock_t *lock)
+{
+	CLEAR_IO_SYNC;
+	return queued_spin_trylock(lock);
+}
+
+static inline void arch_spin_lock(arch_spinlock_t *lock)
+{
+	CLEAR_IO_SYNC;
+	queued_spin_lock(lock);
+}
+
+static inline
+void arch_spin_lock_flags(arch_spinlock_t *lock, unsigned long flags)
+{
+	CLEAR_IO_SYNC;
+	queued_spin_lock(lock);
+}
+
+static inline void arch_spin_unlock(arch_spinlock_t *lock)
+{
+	SYNC_IO;
+	queued_spin_unlock(lock);
+}
+#endif /* _ASM_POWERPC_QSPINLOCK_H */
diff --git a/arch/powerpc/include/asm/spinlock.h b/arch/powerpc/include/asm/spinlock.h
index 8c1b913..954099e 100644
--- a/arch/powerpc/include/asm/spinlock.h
+++ b/arch/powerpc/include/asm/spinlock.h
@@ -60,6 +60,23 @@ static inline bool vcpu_is_preempted(int cpu)
 }
 #endif
 
+#if defined(CONFIG_PPC_SPLPAR)
+/* We only yield to the hypervisor if we are in shared processor mode */
+#define SHARED_PROCESSOR (lppaca_shared_proc(local_paca->lppaca_ptr))
+extern void __spin_yield(arch_spinlock_t *lock);
+extern void __rw_yield(arch_rwlock_t *lock);
+#else /* SPLPAR */
+#define __spin_yield(x)        barrier()
+#define __rw_yield(x)  barrier()
+#define SHARED_PROCESSOR       0
+#endif
+
+#ifdef CONFIG_QUEUED_SPINLOCKS
+#include <asm/qspinlock.h>
+#else
+
+#define arch_spin_relax(lock)  __spin_yield(lock)
+
 static __always_inline int arch_spin_value_unlocked(arch_spinlock_t lock)
 {
 	return lock.slock == 0;
@@ -114,18 +131,6 @@ static inline int arch_spin_trylock(arch_spinlock_t *lock)
  * held.  Conveniently, we have a word in the paca that holds this
  * value.
  */
-
-#if defined(CONFIG_PPC_SPLPAR)
-/* We only yield to the hypervisor if we are in shared processor mode */
-#define SHARED_PROCESSOR (lppaca_shared_proc(local_paca->lppaca_ptr))
-extern void __spin_yield(arch_spinlock_t *lock);
-extern void __rw_yield(arch_rwlock_t *lock);
-#else /* SPLPAR */
-#define __spin_yield(x)	barrier()
-#define __rw_yield(x)	barrier()
-#define SHARED_PROCESSOR	0
-#endif
-
 static inline void arch_spin_lock(arch_spinlock_t *lock)
 {
 	CLEAR_IO_SYNC;
@@ -203,6 +208,7 @@ static inline void arch_spin_unlock_wait(arch_spinlock_t *lock)
 	smp_mb();
 }
 
+#endif /* !CONFIG_QUEUED_SPINLOCKS */
 /*
  * Read-write spinlocks, allowing multiple readers
  * but only one writer.
@@ -338,7 +344,6 @@ static inline void arch_write_unlock(arch_rwlock_t *rw)
 #define arch_read_lock_flags(lock, flags) arch_read_lock(lock)
 #define arch_write_lock_flags(lock, flags) arch_write_lock(lock)
 
-#define arch_spin_relax(lock)	__spin_yield(lock)
 #define arch_read_relax(lock)	__rw_yield(lock)
 #define arch_write_relax(lock)	__rw_yield(lock)
 
diff --git a/arch/powerpc/include/asm/spinlock_types.h b/arch/powerpc/include/asm/spinlock_types.h
index 2351adc..bd7144e 100644
--- a/arch/powerpc/include/asm/spinlock_types.h
+++ b/arch/powerpc/include/asm/spinlock_types.h
@@ -5,11 +5,15 @@
 # error "please don't include this file directly"
 #endif
 
+#ifdef CONFIG_QUEUED_SPINLOCKS
+#include <asm-generic/qspinlock_types.h>
+#else
 typedef struct {
 	volatile unsigned int slock;
 } arch_spinlock_t;
 
 #define __ARCH_SPIN_LOCK_UNLOCKED	{ 0 }
+#endif
 
 typedef struct {
 	volatile signed int lock;
diff --git a/arch/powerpc/lib/locks.c b/arch/powerpc/lib/locks.c
index b7b1237..8f6dbb0 100644
--- a/arch/powerpc/lib/locks.c
+++ b/arch/powerpc/lib/locks.c
@@ -23,6 +23,7 @@
 #include <asm/hvcall.h>
 #include <asm/smp.h>
 
+#ifndef CONFIG_QUEUED_SPINLOCKS
 void __spin_yield(arch_spinlock_t *lock)
 {
 	unsigned int lock_value, holder_cpu, yield_count;
@@ -42,6 +43,7 @@ void __spin_yield(arch_spinlock_t *lock)
 		get_hard_smp_processor_id(holder_cpu), yield_count);
 }
 EXPORT_SYMBOL_GPL(__spin_yield);
+#endif
 
 /*
  * Waiting for a read lock or a write lock on a rwlock...
@@ -68,3 +70,63 @@ void __rw_yield(arch_rwlock_t *rw)
 		get_hard_smp_processor_id(holder_cpu), yield_count);
 }
 #endif
+
+#ifdef CONFIG_QUEUED_SPINLOCKS
+/*
+ * This forbid we load an old value in another LL/SC. Because the SC here force
+ * another LL/SC repeat. So we guarantee all loads in another LL and SC will
+ * read correct value.
+ */
+static inline u32 atomic_read_sync(atomic_t *v)
+{
+	u32 val;
+
+	__asm__ __volatile__(
+"1:	" PPC_LWARX(%0, 0, %2, 0) "\n"
+"	stwcx. %0, 0, %2\n"
+"	bne- 1b\n"
+	: "=&r" (val), "+m" (*v)
+	: "r" (v)
+	: "cr0", "xer");
+
+	return val;
+}
+
+void queued_spin_unlock_wait(struct qspinlock *lock)
+{
+
+	u32 val;
+
+	smp_mb();
+
+	/*
+	 * copied from generic queue_spin_unlock_wait with little modification
+	 */
+	for (;;) {
+		/* need _sync, as we might race with another LL/SC in lock()*/
+		val = atomic_read_sync(&lock->val);
+
+		if (!val) /* not locked, we're done */
+			goto done;
+
+		if (val & _Q_LOCKED_MASK) /* locked, go wait for unlock */
+			break;
+
+		/* not locked, but pending, wait until we observe the lock */
+		cpu_relax();
+	}
+
+	/*
+	 * any unlock is good.
+	 * And _sync() is not needed here, because once we got here, we must
+	 * already read the ->val as LOCKED via a _sync(). Combining the
+	 * smp_mb() before, we guarantee that all the memory accesses before
+	 * unlock_wait() must be observed by the next lock critical section.
+	 */
+	while (atomic_read(&lock->val) & _Q_LOCKED_MASK)
+		cpu_relax();
+done:
+	smp_mb();
+}
+EXPORT_SYMBOL(queued_spin_unlock_wait);
+#endif
-- 
2.4.11

[PATCH v9 2/6] powerpc: platforms/Kconfig: Add qspinlock build config

[Pan Xinhui]

pSeries/powerNV will use qspinlock from now on.

Signed-off-by: Pan Xinhui <xinhui.pan@linux.vnet.ibm.com>
---
 arch/powerpc/platforms/Kconfig | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/arch/powerpc/platforms/Kconfig b/arch/powerpc/platforms/Kconfig
index fbdae83..3559bbf 100644
--- a/arch/powerpc/platforms/Kconfig
+++ b/arch/powerpc/platforms/Kconfig
@@ -20,6 +20,15 @@ source "arch/powerpc/platforms/44x/Kconfig"
 source "arch/powerpc/platforms/40x/Kconfig"
 source "arch/powerpc/platforms/amigaone/Kconfig"
 
+config ARCH_USE_QUEUED_SPINLOCKS
+        depends on PPC_PSERIES || PPC_POWERNV
+        bool "Enable qspinlock"
+        default y
+        help
+	  Enabling this option will let kernel use qspinlock which is a kind of
+	  fairlock.  It has shown a good performance improvement on x86 and also
+	  ppc especially in high contention cases.
+
 config KVM_GUEST
 	bool "KVM Guest support"
 	default n
-- 
2.4.11

[PATCH v9 3/6] powerpc: lib/locks.c: Add cpu yield/wake helper function

[Pan Xinhui]

Add two corresponding helper functions to support pv-qspinlock.

For normal use, __spin_yield_cpu will confer current vcpu slices to the
target vcpu(say, a lock holder). If target vcpu is not specified or it
is in running state, such conferging to lpar happens or not depends.

Because hcall itself will introduce latency and a little overhead. And we
do NOT want to suffer any latency on some cases, e.g. in interrupt handler.
The second parameter *confer* can indicate such case.

__spin_wake_cpu is simpiler, it will wake up one vcpu regardless of its
current vcpu state.

Signed-off-by: Pan Xinhui <xinhui.pan@linux.vnet.ibm.com>
---
 arch/powerpc/include/asm/spinlock.h |  4 +++
 arch/powerpc/lib/locks.c            | 57 +++++++++++++++++++++++++++++++++++++
 2 files changed, 61 insertions(+)

diff --git a/arch/powerpc/include/asm/spinlock.h b/arch/powerpc/include/asm/spinlock.h
index 954099e..6426bd5 100644
--- a/arch/powerpc/include/asm/spinlock.h
+++ b/arch/powerpc/include/asm/spinlock.h
@@ -64,9 +64,13 @@ static inline bool vcpu_is_preempted(int cpu)
 /* We only yield to the hypervisor if we are in shared processor mode */
 #define SHARED_PROCESSOR (lppaca_shared_proc(local_paca->lppaca_ptr))
 extern void __spin_yield(arch_spinlock_t *lock);
+extern void __spin_yield_cpu(int cpu, int confer);
+extern void __spin_wake_cpu(int cpu);
 extern void __rw_yield(arch_rwlock_t *lock);
 #else /* SPLPAR */
 #define __spin_yield(x)        barrier()
+#define __spin_yield_cpu(x, y) barrier()
+#define __spin_wake_cpu(x) barrier()
 #define __rw_yield(x)  barrier()
 #define SHARED_PROCESSOR       0
 #endif
diff --git a/arch/powerpc/lib/locks.c b/arch/powerpc/lib/locks.c
index 8f6dbb0..dff0bfa 100644
--- a/arch/powerpc/lib/locks.c
+++ b/arch/powerpc/lib/locks.c
@@ -23,6 +23,63 @@
 #include <asm/hvcall.h>
 #include <asm/smp.h>
 
+/*
+ * confer our slices to a specified cpu and return. If it is in running state
+ * or cpu is -1, then we will check confer. If confer is NULL, we will return
+ * otherwise we confer our slices to lpar.
+ */
+void __spin_yield_cpu(int cpu, int confer)
+{
+	unsigned int yield_count;
+
+	if (cpu == -1)
+		goto yield_to_lpar;
+
+	BUG_ON(cpu >= nr_cpu_ids);
+	yield_count = be32_to_cpu(lppaca_of(cpu).yield_count);
+
+	/* if cpu is running, confer slices to lpar conditionally*/
+	if ((yield_count & 1) == 0)
+		goto yield_to_lpar;
+
+	plpar_hcall_norets(H_CONFER,
+		get_hard_smp_processor_id(cpu), yield_count);
+	return;
+
+yield_to_lpar:
+	if (confer)
+		plpar_hcall_norets(H_CONFER, -1, 0);
+}
+EXPORT_SYMBOL_GPL(__spin_yield_cpu);
+
+void __spin_wake_cpu(int cpu)
+{
+	BUG_ON(cpu >= nr_cpu_ids);
+	/*
+	 * NOTE: we should always do this hcall regardless of
+	 * the yield_count of the holder_cpu.
+	 * as thers might be a case like below;
+	 *	CPU 1			CPU 2
+	 *				yielded = true
+	 * if (yielded)
+	 *	__spin_wake_cpu()
+	 *				__spin_yield_cpu()
+	 *
+	 * So we might lose a wake if we check the yield_count and
+	 * return directly if the holder_cpu is running.
+	 * IOW. do NOT code like below.
+	 *	yield_count = be32_to_cpu(lppaca_of(cpu).yield_count);
+	 *	if ((yield_count & 1) == 0)
+	 *		return;
+	 *
+	 * a PROD hcall marks the target_cpu proded, which cause the next cede
+	 * or confer called on the target_cpu invalid.
+	 */
+	plpar_hcall_norets(H_PROD,
+		get_hard_smp_processor_id(cpu));
+}
+EXPORT_SYMBOL_GPL(__spin_wake_cpu);
+
 #ifndef CONFIG_QUEUED_SPINLOCKS
 void __spin_yield(arch_spinlock_t *lock)
 {
-- 
2.4.11

[PATCH v9 4/6] powerpc/pv-qspinlock: powerpc support pv-qspinlock

[Pan Xinhui]

The default pv-qspinlock uses qspinlock(native version of pv-qspinlock).
pv_lock initialization should be done in bootstage with irq disabled.
And if we run as a guest with powerKVM/pHyp shared_processor mode,
restore pv_lock_ops callbacks to pv-qspinlock(pv version) which makes
full use of virtualization.

There is a hash table, we store cpu number into it and the key is lock.
So everytime pv_wait can know who is the lock holder by searching the
lock. Also store the lock in a per_cpu struct, and remove it when we own
the lock. Then pv_wait can know which lock we are spinning on. But the
cpu in the hash table might not be the correct lock holder, as for
performace issue, we does not take care of hash conflict.

Also introduce spin_lock_holder, which tells who owns the lock now.
currently the only user is spin_unlock_wait.

Signed-off-by: Pan Xinhui <xinhui.pan@linux.vnet.ibm.com>
---
 arch/powerpc/include/asm/qspinlock.h               |  29 +++-
 arch/powerpc/include/asm/qspinlock_paravirt.h      |  36 +++++
 .../powerpc/include/asm/qspinlock_paravirt_types.h |  13 ++
 arch/powerpc/kernel/paravirt.c                     | 153 +++++++++++++++++++++
 arch/powerpc/lib/locks.c                           |   8 +-
 arch/powerpc/platforms/pseries/setup.c             |   5 +
 6 files changed, 241 insertions(+), 3 deletions(-)
 create mode 100644 arch/powerpc/include/asm/qspinlock_paravirt.h
 create mode 100644 arch/powerpc/include/asm/qspinlock_paravirt_types.h
 create mode 100644 arch/powerpc/kernel/paravirt.c

diff --git a/arch/powerpc/include/asm/qspinlock.h b/arch/powerpc/include/asm/qspinlock.h
index 4c89256..8fd6349 100644
--- a/arch/powerpc/include/asm/qspinlock.h
+++ b/arch/powerpc/include/asm/qspinlock.h
@@ -15,7 +15,7 @@ static inline u8 *__qspinlock_lock_byte(struct qspinlock *lock)
 	return (u8 *)lock + 3 * IS_BUILTIN(CONFIG_CPU_BIG_ENDIAN);
 }
 
-static inline void queued_spin_unlock(struct qspinlock *lock)
+static inline void native_queued_spin_unlock(struct qspinlock *lock)
 {
 	/* release semantics is required */
 	smp_store_release(__qspinlock_lock_byte(lock), 0);
@@ -27,6 +27,33 @@ static inline int queued_spin_is_locked(struct qspinlock *lock)
 	return atomic_read(&lock->val);
 }
 
+#ifdef CONFIG_PARAVIRT_SPINLOCKS
+#include <asm/qspinlock_paravirt.h>
+/*
+ * try to know who is the lock holder, however it is not always true
+ * Return:
+ * -1, we did not know the lock holder.
+ * other value, likely is the lock holder.
+ */
+extern int spin_lock_holder(void *lock);
+
+static inline void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val)
+{
+	pv_queued_spin_lock(lock, val);
+}
+
+static inline void queued_spin_unlock(struct qspinlock *lock)
+{
+	pv_queued_spin_unlock(lock);
+}
+#else
+#define spin_lock_holder(l) (-1)
+static inline void queued_spin_unlock(struct qspinlock *lock)
+{
+	native_queued_spin_unlock(lock);
+}
+#endif
+
 #include <asm-generic/qspinlock.h>
 
 /* we need override it as ppc has io_sync stuff */
diff --git a/arch/powerpc/include/asm/qspinlock_paravirt.h b/arch/powerpc/include/asm/qspinlock_paravirt.h
new file mode 100644
index 0000000..d87cda0
--- /dev/null
+++ b/arch/powerpc/include/asm/qspinlock_paravirt.h
@@ -0,0 +1,36 @@
+#ifndef CONFIG_PARAVIRT_SPINLOCKS
+#error "do not include this file"
+#endif
+
+#ifndef _ASM_QSPINLOCK_PARAVIRT_H
+#define _ASM_QSPINLOCK_PARAVIRT_H
+
+#include  <asm/qspinlock_paravirt_types.h>
+
+extern void pv_lock_init(void);
+extern void native_queued_spin_lock_slowpath(struct qspinlock *lock, u32 val);
+extern void __pv_init_lock_hash(void);
+extern void __pv_queued_spin_lock_slowpath(struct qspinlock *lock, u32 val);
+extern void __pv_queued_spin_unlock(struct qspinlock *lock);
+
+static inline void pv_queued_spin_lock(struct qspinlock *lock, u32 val)
+{
+	pv_lock_op.lock(lock, val);
+}
+
+static inline void pv_queued_spin_unlock(struct qspinlock *lock)
+{
+	pv_lock_op.unlock(lock);
+}
+
+static inline void pv_wait(u8 *ptr, u8 val)
+{
+	pv_lock_op.wait(ptr, val);
+}
+
+static inline void pv_kick(int cpu)
+{
+	pv_lock_op.kick(cpu);
+}
+
+#endif
diff --git a/arch/powerpc/include/asm/qspinlock_paravirt_types.h b/arch/powerpc/include/asm/qspinlock_paravirt_types.h
new file mode 100644
index 0000000..83611ed
--- /dev/null
+++ b/arch/powerpc/include/asm/qspinlock_paravirt_types.h
@@ -0,0 +1,13 @@
+#ifndef _ASM_QSPINLOCK_PARAVIRT_TYPES_H
+#define _ASM_QSPINLOCK_PARAVIRT_TYPES_H
+
+struct pv_lock_ops {
+	void (*lock)(struct qspinlock *lock, u32 val);
+	void (*unlock)(struct qspinlock *lock);
+	void (*wait)(u8 *ptr, u8 val);
+	void (*kick)(int cpu);
+};
+
+extern struct pv_lock_ops pv_lock_op;
+
+#endif
diff --git a/arch/powerpc/kernel/paravirt.c b/arch/powerpc/kernel/paravirt.c
new file mode 100644
index 0000000..e697b17
--- /dev/null
+++ b/arch/powerpc/kernel/paravirt.c
@@ -0,0 +1,153 @@
+/*
+ * 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; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#include <linux/spinlock.h>
+#include <linux/smp.h>
+#include <linux/hash.h>
+#include <linux/bootmem.h>
+
+/* +2 here is to make sure there is not many conflict*/
+#define NUM_LOCK_CPU_ENTRY_SHIFT (order_base_2(NR_CPUS) + 2)
+#define NUM_LOCK_CPU_ENTRY (1 << NUM_LOCK_CPU_ENTRY_SHIFT)
+/* we can only spin on 4 locks at same time on same cpu*/
+#define NUM_LOCKS_PER_CPU 4
+
+static u16 *hash_lock_cpu_ptr;
+
+struct locks_on_cpu {
+	void *l[NUM_LOCKS_PER_CPU];
+	int count;
+};
+
+static DEFINE_PER_CPU(struct locks_on_cpu, node);
+
+static u16 *hash(void *l)
+{
+	int val = hash_ptr(l, NUM_LOCK_CPU_ENTRY_SHIFT);
+
+	return &hash_lock_cpu_ptr[val];
+}
+
+static void __init init_hash(void)
+{
+	int size = NUM_LOCK_CPU_ENTRY * sizeof(*hash_lock_cpu_ptr);
+
+	hash_lock_cpu_ptr = memblock_virt_alloc(size, 0);
+	memset(hash_lock_cpu_ptr, 0, size);
+}
+
+#define lock_get_holder(l)	\
+		((int)(*hash(l) - 1))
+
+#define lock_set_holder(l)	\
+		(*hash(l) = raw_smp_processor_id() + 1)
+
+int spin_lock_holder(void *lock)
+{
+	/* we might run on PowerNV, which has no hash table ptr*/
+	if (hash_lock_cpu_ptr)
+		return lock_get_holder(lock);
+	return -1;
+}
+EXPORT_SYMBOL(spin_lock_holder);
+
+static void *this_cpu_lock(void)
+{
+	struct locks_on_cpu *this_node = this_cpu_ptr(&node);
+	int i = this_node->count - 1;
+
+	return this_node->l[i];
+}
+
+static void cpu_save_lock(void *l)
+{
+	struct locks_on_cpu *this_node = this_cpu_ptr(&node);
+	int i = this_node->count++;
+
+	this_node->l[i] = l;
+}
+
+static void cpu_remove_lock(void *l)
+{
+	__this_cpu_dec(node.count);
+}
+
+static void __native_queued_spin_unlock(struct qspinlock *lock)
+{
+	native_queued_spin_unlock(lock);
+}
+
+static void __pv_lock(struct qspinlock *lock, u32 val)
+{
+	/*
+	 * save the lock we are spinning on
+	 * pv_wait need know this lock
+	 */
+	cpu_save_lock(lock);
+
+	__pv_queued_spin_lock_slowpath(lock, val);
+
+	/* as we win the lock, remove it*/
+	cpu_remove_lock(lock);
+
+	/*
+	 * let other spinner know who is the lock holder
+	 * we does not need to unset lock holder in unlock()
+	 */
+	lock_set_holder(lock);
+}
+
+static void __pv_wait(u8 *ptr, u8 val)
+{
+	void *l = this_cpu_lock();
+	int cpu;
+	int always_confer = !in_interrupt();
+
+	while (READ_ONCE(*ptr) == val) {
+		HMT_low();
+		/*
+		 * the lock might be unlocked once and locked again
+		 */
+		cpu = lock_get_holder(l);
+
+		/*
+		 * the default behavior of __spin_yield_cpu is yielding
+		 * our cpu slices to target vcpu or lpar(pHyp or KVM).
+		 * consider the latency of hcall itself and the priority of
+		 * current task, we can do a optimisation.
+		 * IOW, if we are in interrupt, and the target vcpu is running
+		 * we do not yield ourself to lpar.
+		 */
+		__spin_yield_cpu(cpu, always_confer);
+	}
+	HMT_medium();
+}
+
+static void __pv_kick(int cpu)
+{
+	__spin_wake_cpu(cpu);
+}
+
+struct pv_lock_ops pv_lock_op = {
+	.lock = native_queued_spin_lock_slowpath,
+	.unlock = __native_queued_spin_unlock,
+	.wait = NULL,
+	.kick = NULL,
+};
+EXPORT_SYMBOL(pv_lock_op);
+
+void __init pv_lock_init(void)
+{
+	if (SHARED_PROCESSOR) {
+		init_hash();
+		__pv_init_lock_hash();
+		pv_lock_op.lock = __pv_lock;
+		pv_lock_op.unlock = __pv_queued_spin_unlock;
+		pv_lock_op.wait = __pv_wait;
+		pv_lock_op.kick = __pv_kick;
+	}
+}
diff --git a/arch/powerpc/lib/locks.c b/arch/powerpc/lib/locks.c
index dff0bfa..b50c16a 100644
--- a/arch/powerpc/lib/locks.c
+++ b/arch/powerpc/lib/locks.c
@@ -180,8 +180,12 @@ void queued_spin_unlock_wait(struct qspinlock *lock)
 	 * smp_mb() before, we guarantee that all the memory accesses before
 	 * unlock_wait() must be observed by the next lock critical section.
 	 */
-	while (atomic_read(&lock->val) & _Q_LOCKED_MASK)
-		cpu_relax();
+	while (atomic_read(&lock->val) & _Q_LOCKED_MASK) {
+		HMT_low();
+		if (SHARED_PROCESSOR)
+			__spin_yield_cpu(spin_lock_holder(lock), 0);
+	}
+	HMT_medium();
 done:
 	smp_mb();
 }
diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c
index 97aa3f3..ca61ead 100644
--- a/arch/powerpc/platforms/pseries/setup.c
+++ b/arch/powerpc/platforms/pseries/setup.c
@@ -487,6 +487,11 @@ static void __init pSeries_setup_arch(void)
 	}
 
 	ppc_md.pcibios_root_bridge_prepare = pseries_root_bridge_prepare;
+
+#ifdef CONFIG_PARAVIRT_SPINLOCKS
+	pv_lock_init();
+#endif
+
 }
 
 static int __init pSeries_init_panel(void)
-- 
2.4.11

[PATCH v9 5/6] powerpc: pSeries: Add pv-qspinlock build config/make

[Pan Xinhui]

pSeries run as a guest and might need pv-qspinlock.

Signed-off-by: Pan Xinhui <xinhui.pan@linux.vnet.ibm.com>
---
 arch/powerpc/kernel/Makefile           | 1 +
 arch/powerpc/platforms/pseries/Kconfig | 8 ++++++++
 2 files changed, 9 insertions(+)

diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
index 1925341..4780415 100644
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -53,6 +53,7 @@ obj-$(CONFIG_PPC_970_NAP)	+= idle_power4.o
 obj-$(CONFIG_PPC_P7_NAP)	+= idle_book3s.o
 procfs-y			:= proc_powerpc.o
 obj-$(CONFIG_PROC_FS)		+= $(procfs-y)
+obj-$(CONFIG_PARAVIRT_SPINLOCKS)	+= paravirt.o
 rtaspci-$(CONFIG_PPC64)-$(CONFIG_PCI)	:= rtas_pci.o
 obj-$(CONFIG_PPC_RTAS)		+= rtas.o rtas-rtc.o $(rtaspci-y-y)
 obj-$(CONFIG_PPC_RTAS_DAEMON)	+= rtasd.o
diff --git a/arch/powerpc/platforms/pseries/Kconfig b/arch/powerpc/platforms/pseries/Kconfig
index bec90fb..c9cc064 100644
--- a/arch/powerpc/platforms/pseries/Kconfig
+++ b/arch/powerpc/platforms/pseries/Kconfig
@@ -33,6 +33,14 @@ config PPC_SPLPAR
 	  processors, that is, which share physical processors between
 	  two or more partitions.
 
+config PARAVIRT_SPINLOCKS
+       bool "Paravirtialization support for qspinlock"
+       depends on PPC_SPLPAR && QUEUED_SPINLOCKS
+       default y
+       help
+         If kernel need run as a guest then enable this option.
+         Generally it can let kernel have a better performace.
+
 config DTL
 	bool "Dispatch Trace Log"
 	depends on PPC_SPLPAR && DEBUG_FS
-- 
2.4.11

[PATCH v9 6/6] powerpc/pv-qspinlock: Optimise native unlock path

[Pan Xinhui]

Avoid a function call under native version of qspinlock. On powerNV,
bafore applying this patch, every unlock is expensive. This small
optimizes enhance the performance.

We use static_key with jump_lable which removes unnecessary loads of
lppaca and its stuff.

Signed-off-by: Pan Xinhui <xinhui.pan@linux.vnet.ibm.com>
---
 arch/powerpc/include/asm/qspinlock_paravirt.h | 18 +++++++++++++++++-
 arch/powerpc/kernel/paravirt.c                |  4 ++++
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/include/asm/qspinlock_paravirt.h b/arch/powerpc/include/asm/qspinlock_paravirt.h
index d87cda0..8d39446 100644
--- a/arch/powerpc/include/asm/qspinlock_paravirt.h
+++ b/arch/powerpc/include/asm/qspinlock_paravirt.h
@@ -6,12 +6,14 @@
 #define _ASM_QSPINLOCK_PARAVIRT_H
 
 #include  <asm/qspinlock_paravirt_types.h>
+#include  <linux/jump_label.h>
 
 extern void pv_lock_init(void);
 extern void native_queued_spin_lock_slowpath(struct qspinlock *lock, u32 val);
 extern void __pv_init_lock_hash(void);
 extern void __pv_queued_spin_lock_slowpath(struct qspinlock *lock, u32 val);
 extern void __pv_queued_spin_unlock(struct qspinlock *lock);
+extern struct static_key_true sharedprocessor_key;
 
 static inline void pv_queued_spin_lock(struct qspinlock *lock, u32 val)
 {
@@ -20,7 +22,21 @@ static inline void pv_queued_spin_lock(struct qspinlock *lock, u32 val)
 
 static inline void pv_queued_spin_unlock(struct qspinlock *lock)
 {
-	pv_lock_op.unlock(lock);
+	/*
+	 * on powerNV and pSeries with jump_label, code will be
+	 *	PowerNV:		pSeries:
+	 *	nop;			b 2f;
+	 *	native unlock		2:
+	 *				pv unlock;
+	 * In this way, we can do unlock quick in native case.
+	 *
+	 * IF jump_label is not enabled, we fall back into
+	 * if condition, IOW, ld && cmp && bne.
+	 */
+	if (static_branch_likely(&sharedprocessor_key))
+		native_queued_spin_unlock(lock);
+	else
+		pv_lock_op.unlock(lock);
 }
 
 static inline void pv_wait(u8 *ptr, u8 val)
diff --git a/arch/powerpc/kernel/paravirt.c b/arch/powerpc/kernel/paravirt.c
index e697b17..a0a000e 100644
--- a/arch/powerpc/kernel/paravirt.c
+++ b/arch/powerpc/kernel/paravirt.c
@@ -140,6 +140,9 @@ struct pv_lock_ops pv_lock_op = {
 };
 EXPORT_SYMBOL(pv_lock_op);
 
+struct static_key_true sharedprocessor_key = STATIC_KEY_TRUE_INIT;
+EXPORT_SYMBOL(sharedprocessor_key);
+
 void __init pv_lock_init(void)
 {
 	if (SHARED_PROCESSOR) {
@@ -149,5 +152,6 @@ void __init pv_lock_init(void)
 		pv_lock_op.unlock = __pv_queued_spin_unlock;
 		pv_lock_op.wait = __pv_wait;
 		pv_lock_op.kick = __pv_kick;
+		static_branch_disable(&sharedprocessor_key);
 	}
 }
-- 
2.4.11