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sched: fix buddie group latency

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Similar to the previous patch, by not clearing buddies we can select entities
past their run quota, which can increase latency. This means we have to clear
group buddies as well.

Do not use the group clear for pick_next_task(), otherwise that'll get O(n^2).

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2009-01-28 14:51:40 +01:00 committed by Ingo Molnar
parent a9f3e2b549
commit a571bbeafb
1 changed files with 8 additions and 2 deletions
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10
kernel/sched_fair.c
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@ -719,7 +719,7 @@ enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int wakeup)
__enqueue_entity(cfs_rq, se);
}
static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
static void __clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
if (cfs_rq->last == se)
cfs_rq->last = NULL;
@ -728,6 +728,12 @@ static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
cfs_rq->next = NULL;
}
static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
for_each_sched_entity(se)
__clear_buddies(cfs_rq_of(se), se);
}
static void
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int sleep)
{
@ -1455,7 +1461,7 @@ static struct task_struct *pick_next_task_fair(struct rq *rq)
* If se was a buddy, clear it so that it will have to earn
* the favour again.
*/
clear_buddies(cfs_rq, se);
__clear_buddies(cfs_rq, se);
set_next_entity(cfs_rq, se);
cfs_rq = group_cfs_rq(se);
} while (cfs_rq);