From: Peter Zijlstra Date: Fri, 14 Mar 2008 20:12:12 +0000 (+0100) Subject: sched: fix overload performance: buddy wakeups X-Git-Tag: v2.6.25-rc6~7 X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=aa2ac25229cd4d0280f6174c42712744ad61b140;p=pandora-kernel.git 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 --- diff --git a/kernel/sched.c b/kernel/sched.c index 6b06f23261c0..d1ad69b270ca 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; Reading git-diff-tree failed