From aa2ac25229cd4d0280f6174c42712744ad61b140 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Fri, 14 Mar 2008 21:12:12 +0100 Subject: sched: fix overload performance: buddy wakeups Currently we schedule to the leftmost task in the runqueue. When the runtimes are very short because of some server/client ping-pong, especially in over-saturated workloads, this will cycle through all tasks trashing the cache. Reduce cache trashing by keeping dependent tasks together by running newly woken tasks first. However, by not running the leftmost task first we could starve tasks because the wakee can gain unlimited runtime. Therefore we only run the wakee if its within a small (wakeup_granularity) window of the leftmost task. This preserves fairness, but does alternate server/client task groups. Signed-off-by: Peter Zijlstra Signed-off-by: Ingo Molnar --- kernel/sched.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'kernel/sched.c') diff --git a/kernel/sched.c b/kernel/sched.c index 6b06f23261c..d1ad69b270c 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -301,7 +301,7 @@ struct cfs_rq { /* 'curr' points to currently running entity on this cfs_rq. * It is set to NULL otherwise (i.e when none are currently running). */ - struct sched_entity *curr; + struct sched_entity *curr, *next; unsigned long nr_spread_over; -- cgit v1.2.3-18-g5258