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sched: Add WF_FORK

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Avoid the cache buddies from biasing the time distribution away
from fork()ers. Normally the next buddy will be the preferred
scheduling target, but this makes fork()s prefer to run the new
child, whereas we prefer to run the parent, since that will
generate more work.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2009-09-14 20:02:34 +02:00 committed by Ingo Molnar
parent 7d47872146
commit a7558e0105
3 changed files with 3 additions and 2 deletions
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1
include/linux/sched.h
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@ -1028,6 +1028,7 @@ struct sched_domain;
* wake flags
*/
#define WF_SYNC 0x01 /* waker goes to sleep after wakup */
#define WF_FORK 0x02 /* child wakeup after fork */
struct sched_class {
const struct sched_class *next;

2
kernel/sched.c
View file

@ -2602,7 +2602,7 @@ void wake_up_new_task(struct task_struct *p, unsigned long clone_flags)
inc_nr_running(rq);
}
trace_sched_wakeup_new(rq, p, 1);
check_preempt_curr(rq, p, 0);
check_preempt_curr(rq, p, WF_FORK);
#ifdef CONFIG_SMP
if (p->sched_class->task_wake_up)
p->sched_class->task_wake_up(rq, p);

2
kernel/sched_fair.c
View file

@ -1580,7 +1580,7 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int flags
*/
if (sched_feat(LAST_BUDDY) && likely(se->on_rq && curr != rq->idle))
set_last_buddy(se);
if (sched_feat(NEXT_BUDDY))
if (sched_feat(NEXT_BUDDY) && !(flags & WF_FORK))
set_next_buddy(pse);
/*