From: Peter Zijlstra Date: Fri, 24 Oct 2008 09:06:16 +0000 (+0200) Subject: sched: virtual time buddy preemption X-Git-Tag: v2.6.28-rc3~90^2~1 X-Git-Url: http://pilppa.com/gitweb/?a=commitdiff_plain;h=3f3a490480d8ab96e0fe30a41f80f14e6a0c579d;p=linux-2.6-omap-h63xx.git sched: virtual time buddy preemption Since we moved wakeup preemption back to virtual time, it makes sense to move the buddy stuff back as well. The purpose of the buddy scheduling is to allow a quickly scheduling pair of tasks to run away from the group as far as a regular busy task would be allowed under wakeup preemption. This has the advantage that the pair can ping-pong for a while, enjoying cache-hotness. Without buddy scheduling other tasks would interleave destroying the cache. Also, it saves a word in cfs_rq. Signed-off-by: Peter Zijlstra Acked-by: Mike Galbraith Signed-off-by: Ingo Molnar --- diff --git a/kernel/sched.c b/kernel/sched.c index 12bc367d924..e8819bc6f46 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -386,7 +386,6 @@ struct cfs_rq { u64 exec_clock; u64 min_vruntime; - u64 pair_start; struct rb_root tasks_timeline; struct rb_node *rb_leftmost; diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c index 7af17e04a6d..ce514afd78f 100644 --- a/kernel/sched_fair.c +++ b/kernel/sched_fair.c @@ -791,16 +791,14 @@ set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se) se->prev_sum_exec_runtime = se->sum_exec_runtime; } +static int +wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se); + static struct sched_entity * pick_next(struct cfs_rq *cfs_rq, struct sched_entity *se) { - struct rq *rq = rq_of(cfs_rq); - u64 pair_slice = rq->clock - cfs_rq->pair_start; - - if (!cfs_rq->next || pair_slice > sysctl_sched_min_granularity) { - cfs_rq->pair_start = rq->clock; + if (!cfs_rq->next || wakeup_preempt_entity(cfs_rq->next, se) == 1) return se; - } return cfs_rq->next; }