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authorIngo Molnar <mingo@kernel.org>2013-08-14 17:58:56 +0200
committerIngo Molnar <mingo@kernel.org>2013-08-14 17:58:56 +0200
commit6f1d657668ac3041b65265d3653d7e9172a0d603 (patch)
tree6e837c683783708637cc4caf9de759166c7469b7 /kernel/sched
parentd4e4ab86bcba5a72779c43dc1459f71fea3d89c8 (diff)
parentd13508f9440e46dccac6a2dd48d51a73b2207482 (diff)
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Merge branch 'timers/nohz-v3' of git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks into timers/nohz
Pull nohz improvements from Frederic Weisbecker: " It mostly contains fixes and full dynticks off-case optimizations. I believe that distros want to enable this feature so it seems important to optimize the case where the "nohz_full=" parameter is empty. ie: I'm trying to remove any performance regression that comes with NO_HZ_FULL=y when the feature is not used. This patchset improves the current situation a lot (off-case appears to be around 11% faster with hackbench, although I guess it may vary depending on the configuration but it should be significantly faster in any case) now there is still some work to do: I can still observe a remaining loss of 1.6% throughput seen with hackbench compared to CONFIG_NO_HZ_FULL=n. " Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/sched')
-rw-r--r--kernel/sched/core.c4
-rw-r--r--kernel/sched/cputime.c53
2 files changed, 17 insertions, 40 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index b7c32cb..3fb7ace 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2510,13 +2510,11 @@ void __sched schedule_preempt_disabled(void)
*/
asmlinkage void __sched notrace preempt_schedule(void)
{
- struct thread_info *ti = current_thread_info();
-
/*
* If there is a non-zero preempt_count or interrupts are disabled,
* we do not want to preempt the current task. Just return..
*/
- if (likely(ti->preempt_count || irqs_disabled()))
+ if (likely(!preemptible()))
return;
do {
diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
index a7959e0..c1d7493 100644
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -378,11 +378,8 @@ static inline void irqtime_account_process_tick(struct task_struct *p, int user_
#ifdef CONFIG_VIRT_CPU_ACCOUNTING
#ifndef __ARCH_HAS_VTIME_TASK_SWITCH
-void vtime_task_switch(struct task_struct *prev)
+void vtime_common_task_switch(struct task_struct *prev)
{
- if (!vtime_accounting_enabled())
- return;
-
if (is_idle_task(prev))
vtime_account_idle(prev);
else
@@ -404,11 +401,8 @@ void vtime_task_switch(struct task_struct *prev)
* vtime_account().
*/
#ifndef __ARCH_HAS_VTIME_ACCOUNT
-void vtime_account_irq_enter(struct task_struct *tsk)
+void vtime_common_account_irq_enter(struct task_struct *tsk)
{
- if (!vtime_accounting_enabled())
- return;
-
if (!in_interrupt()) {
/*
* If we interrupted user, context_tracking_in_user()
@@ -428,7 +422,7 @@ void vtime_account_irq_enter(struct task_struct *tsk)
}
vtime_account_system(tsk);
}
-EXPORT_SYMBOL_GPL(vtime_account_irq_enter);
+EXPORT_SYMBOL_GPL(vtime_common_account_irq_enter);
#endif /* __ARCH_HAS_VTIME_ACCOUNT */
#endif /* CONFIG_VIRT_CPU_ACCOUNTING */
@@ -559,12 +553,6 @@ static void cputime_adjust(struct task_cputime *curr,
{
cputime_t rtime, stime, utime, total;
- if (vtime_accounting_enabled()) {
- *ut = curr->utime;
- *st = curr->stime;
- return;
- }
-
stime = curr->stime;
total = stime + curr->utime;
@@ -664,23 +652,17 @@ static void __vtime_account_system(struct task_struct *tsk)
void vtime_account_system(struct task_struct *tsk)
{
- if (!vtime_accounting_enabled())
- return;
-
write_seqlock(&tsk->vtime_seqlock);
__vtime_account_system(tsk);
write_sequnlock(&tsk->vtime_seqlock);
}
-void vtime_account_irq_exit(struct task_struct *tsk)
+void vtime_gen_account_irq_exit(struct task_struct *tsk)
{
- if (!vtime_accounting_enabled())
- return;
-
write_seqlock(&tsk->vtime_seqlock);
+ __vtime_account_system(tsk);
if (context_tracking_in_user())
tsk->vtime_snap_whence = VTIME_USER;
- __vtime_account_system(tsk);
write_sequnlock(&tsk->vtime_seqlock);
}
@@ -688,12 +670,8 @@ void vtime_account_user(struct task_struct *tsk)
{
cputime_t delta_cpu;
- if (!vtime_accounting_enabled())
- return;
-
- delta_cpu = get_vtime_delta(tsk);
-
write_seqlock(&tsk->vtime_seqlock);
+ delta_cpu = get_vtime_delta(tsk);
tsk->vtime_snap_whence = VTIME_SYS;
account_user_time(tsk, delta_cpu, cputime_to_scaled(delta_cpu));
write_sequnlock(&tsk->vtime_seqlock);
@@ -701,22 +679,27 @@ void vtime_account_user(struct task_struct *tsk)
void vtime_user_enter(struct task_struct *tsk)
{
- if (!vtime_accounting_enabled())
- return;
-
write_seqlock(&tsk->vtime_seqlock);
- tsk->vtime_snap_whence = VTIME_USER;
__vtime_account_system(tsk);
+ tsk->vtime_snap_whence = VTIME_USER;
write_sequnlock(&tsk->vtime_seqlock);
}
void vtime_guest_enter(struct task_struct *tsk)
{
+ /*
+ * The flags must be updated under the lock with
+ * the vtime_snap flush and update.
+ * That enforces a right ordering and update sequence
+ * synchronization against the reader (task_gtime())
+ * that can thus safely catch up with a tickless delta.
+ */
write_seqlock(&tsk->vtime_seqlock);
__vtime_account_system(tsk);
current->flags |= PF_VCPU;
write_sequnlock(&tsk->vtime_seqlock);
}
+EXPORT_SYMBOL_GPL(vtime_guest_enter);
void vtime_guest_exit(struct task_struct *tsk)
{
@@ -725,6 +708,7 @@ void vtime_guest_exit(struct task_struct *tsk)
current->flags &= ~PF_VCPU;
write_sequnlock(&tsk->vtime_seqlock);
}
+EXPORT_SYMBOL_GPL(vtime_guest_exit);
void vtime_account_idle(struct task_struct *tsk)
{
@@ -733,11 +717,6 @@ void vtime_account_idle(struct task_struct *tsk)
account_idle_time(delta_cpu);
}
-bool vtime_accounting_enabled(void)
-{
- return context_tracking_active();
-}
-
void arch_vtime_task_switch(struct task_struct *prev)
{
write_seqlock(&prev->vtime_seqlock);