diff options
| author | Peter Zijlstra <a.p.zijlstra@chello.nl> | 2009-07-10 16:57:57 +0400 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-07-11 01:24:05 +0400 |
| commit | d86ee4809d0329d4aa0d0f2c76c2295a16862799 (patch) | |
| tree | 32b3eaf766c1127ef2298c2e48b5441b7cf9b843 | |
| parent | c99e6efe1ba04561e7d93a81f0be07e37427e835 (diff) | |
| download | linux-d86ee4809d0329d4aa0d0f2c76c2295a16862799.tar.xz | |
sched: optimize cond_resched()
Optimize cond_resched() by removing one conditional.
Currently cond_resched() checks system_state ==
SYSTEM_RUNNING in order to avoid scheduling before the
scheduler is running.
We can however, as per suggestion of Matt, use
PREEMPT_ACTIVE to accomplish that very same.
Suggested-by: Matt Mackall <mpm@selenic.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Matt Mackall <mpm@selenic.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | include/linux/sched.h | 5 | ||||
| -rw-r--r-- | kernel/sched.c | 14 |
2 files changed, 13 insertions, 6 deletions
diff --git a/include/linux/sched.h b/include/linux/sched.h index 2a99f1c15cf8..16a982e389fb 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -501,8 +501,11 @@ struct task_cputime { /* * Disable preemption until the scheduler is running. * Reset by start_kernel()->sched_init()->init_idle(). + * + * We include PREEMPT_ACTIVE to avoid cond_resched() from working + * before the scheduler is active -- see should_resched(). */ -#define INIT_PREEMPT_COUNT (1) +#define INIT_PREEMPT_COUNT (1 + PREEMPT_ACTIVE) /** * struct thread_group_cputimer - thread group interval timer counts diff --git a/kernel/sched.c b/kernel/sched.c index 7c9098d186e6..01f55ada3598 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -6541,6 +6541,11 @@ SYSCALL_DEFINE0(sched_yield) return 0; } +static inline int should_resched(void) +{ + return need_resched() && !(preempt_count() & PREEMPT_ACTIVE); +} + static void __cond_resched(void) { #ifdef CONFIG_DEBUG_SPINLOCK_SLEEP @@ -6560,8 +6565,7 @@ static void __cond_resched(void) int __sched _cond_resched(void) { - if (need_resched() && !(preempt_count() & PREEMPT_ACTIVE) && - system_state == SYSTEM_RUNNING) { + if (should_resched()) { __cond_resched(); return 1; } @@ -6579,12 +6583,12 @@ EXPORT_SYMBOL(_cond_resched); */ int cond_resched_lock(spinlock_t *lock) { - int resched = need_resched() && system_state == SYSTEM_RUNNING; + int resched = should_resched(); int ret = 0; if (spin_needbreak(lock) || resched) { spin_unlock(lock); - if (resched && need_resched()) + if (resched) __cond_resched(); else cpu_relax(); @@ -6599,7 +6603,7 @@ int __sched cond_resched_softirq(void) { BUG_ON(!in_softirq()); - if (need_resched() && system_state == SYSTEM_RUNNING) { + if (should_resched()) { local_bh_enable(); __cond_resched(); local_bh_disable(); |