redonkable
/
alistair23-linux
1
0
Fork 0
Code Releases Activity

sched/core: Move task_rq_lock() out of line 

Its a rather large function, inline doesn't seems to make much sense:

 $ size defconfig-build/kernel/sched/core.o{.orig,}
    text    data     bss     dec     hex filename
   56533   21037    2320   79890   13812 defconfig-build/kernel/sched/core.o.orig
   55733   21037    2320   79090   134f2 defconfig-build/kernel/sched/core.o

The 'perf bench sched messaging' micro-benchmark shows a visible improvement
of 4-5%:

  $ for i in /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor ; do echo performance > $i ; done
  $ perf stat --null --repeat 25 -- perf bench sched messaging -g 40 -l 5000

  pre:
       4.582798193 seconds time elapsed          ( +-  1.41% )
       4.733374877 seconds time elapsed          ( +-  2.10% )
       4.560955136 seconds time elapsed          ( +-  1.43% )
       4.631062303 seconds time elapsed          ( +-  1.40% )

  post:
       4.364765213 seconds time elapsed          ( +-  0.91% )
       4.454442734 seconds time elapsed          ( +-  1.18% )
       4.448893817 seconds time elapsed          ( +-  1.41% )
       4.424346872 seconds time elapsed          ( +-  0.97% )

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
hifive-unleashed-5.1
Peter Zijlstra 2016-04-28 16:16:33 +02:00 committed by Ingo Molnar
parent 64b7aad579
commit 3e71a462dd
2 changed files with 69 additions and 63 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

65
kernel/sched/core.c
View File

@ -170,6 +170,71 @@ static struct rq *this_rq_lock(void)
return rq;
}
/*
* __task_rq_lock - lock the rq @p resides on.
*/
struct rq *__task_rq_lock(struct task_struct *p)
__acquires(rq->lock)
{
struct rq *rq;
lockdep_assert_held(&p->pi_lock);
for (;;) {
rq = task_rq(p);
raw_spin_lock(&rq->lock);
if (likely(rq == task_rq(p) && !task_on_rq_migrating(p))) {
lockdep_pin_lock(&rq->lock);
return rq;
}
raw_spin_unlock(&rq->lock);
while (unlikely(task_on_rq_migrating(p)))
cpu_relax();
}
}
/*
* task_rq_lock - lock p->pi_lock and lock the rq @p resides on.
*/
struct rq *task_rq_lock(struct task_struct *p, unsigned long *flags)
__acquires(p->pi_lock)
__acquires(rq->lock)
{
struct rq *rq;
for (;;) {
raw_spin_lock_irqsave(&p->pi_lock, *flags);
rq = task_rq(p);
raw_spin_lock(&rq->lock);
/*
* move_queued_task() task_rq_lock()
*
* ACQUIRE (rq->lock)
* [S] ->on_rq = MIGRATING [L] rq = task_rq()
* WMB (__set_task_cpu()) ACQUIRE (rq->lock);
* [S] ->cpu = new_cpu [L] task_rq()
* [L] ->on_rq
* RELEASE (rq->lock)
*
* If we observe the old cpu in task_rq_lock, the acquire of
* the old rq->lock will fully serialize against the stores.
*
* If we observe the new cpu in task_rq_lock, the acquire will
* pair with the WMB to ensure we must then also see migrating.
*/
if (likely(rq == task_rq(p) && !task_on_rq_migrating(p))) {
lockdep_pin_lock(&rq->lock);
return rq;
}
raw_spin_unlock(&rq->lock);
raw_spin_unlock_irqrestore(&p->pi_lock, *flags);
while (unlikely(task_on_rq_migrating(p)))
cpu_relax();
}
}
#ifdef CONFIG_SCHED_HRTICK
/*
* Use HR-timers to deliver accurate preemption points.

67
kernel/sched/sched.h
View File

@ -1451,70 +1451,11 @@ static inline void sched_rt_avg_update(struct rq *rq, u64 rt_delta) { }
static inline void sched_avg_update(struct rq *rq) { }
#endif
/*
* __task_rq_lock - lock the rq @p resides on.
*/
static inline struct rq *__task_rq_lock(struct task_struct *p)
__acquires(rq->lock)
{
struct rq *rq;
lockdep_assert_held(&p->pi_lock);
for (;;) {
rq = task_rq(p);
raw_spin_lock(&rq->lock);
if (likely(rq == task_rq(p) && !task_on_rq_migrating(p))) {
lockdep_pin_lock(&rq->lock);
return rq;
}
raw_spin_unlock(&rq->lock);
while (unlikely(task_on_rq_migrating(p)))
cpu_relax();
}
}
/*
* task_rq_lock - lock p->pi_lock and lock the rq @p resides on.
*/
static inline struct rq *task_rq_lock(struct task_struct *p, unsigned long *flags)
struct rq *__task_rq_lock(struct task_struct *p)
__acquires(rq->lock);
struct rq *task_rq_lock(struct task_struct *p, unsigned long *flags)
__acquires(p->pi_lock)
__acquires(rq->lock)
{
struct rq *rq;
for (;;) {
raw_spin_lock_irqsave(&p->pi_lock, *flags);
rq = task_rq(p);
raw_spin_lock(&rq->lock);
/*
* move_queued_task() task_rq_lock()
*
* ACQUIRE (rq->lock)
* [S] ->on_rq = MIGRATING [L] rq = task_rq()
* WMB (__set_task_cpu()) ACQUIRE (rq->lock);
* [S] ->cpu = new_cpu [L] task_rq()
* [L] ->on_rq
* RELEASE (rq->lock)
*
* If we observe the old cpu in task_rq_lock, the acquire of
* the old rq->lock will fully serialize against the stores.
*
* If we observe the new cpu in task_rq_lock, the acquire will
* pair with the WMB to ensure we must then also see migrating.
*/
if (likely(rq == task_rq(p) && !task_on_rq_migrating(p))) {
lockdep_pin_lock(&rq->lock);
return rq;
}
raw_spin_unlock(&rq->lock);
raw_spin_unlock_irqrestore(&p->pi_lock, *flags);
while (unlikely(task_on_rq_migrating(p)))
cpu_relax();
}
}
__acquires(rq->lock);
static inline void __task_rq_unlock(struct rq *rq)
__releases(rq->lock)