Messages in this thread Patch in this message | | | Date | Wed, 28 Jan 2009 14:51:40 +0100 | From | Peter Zijlstra <> | Subject | [PATCH 3/3] 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> --- kernel/sched_fair.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-)
Index: linux-2.6/kernel/sched_fair.c =================================================================== --- linux-2.6.orig/kernel/sched_fair.c +++ linux-2.6/kernel/sched_fair.c @@ -719,7 +719,7 @@ enqueue_entity(struct cfs_rq *cfs_rq, st __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->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) { @@ -1502,7 +1508,7 @@ static struct task_struct *pick_next_tas * 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); --
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