From: Peter Zijlstra <a.p.zijlstra@chello.nl>
Date: Sat, 20 Sep 2008 21:38:02 +0000 (+0200)
Subject: sched: wakeup preempt when small overlap
X-Git-Tag: v2.6.27.46~27
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ecfb7fb9b13c617447a7f6b5925da26798c1a8a1;p=pandora-kernel.git

sched: wakeup preempt when small overlap

commit 15afe09bf496ae10c989e1a375a6b5da7bd3e16e upstream.

Lin Ming reported a 10% OLTP regression against 2.6.27-rc4.

The difference seems to come from different preemption agressiveness,
which affects the cache footprint of the workload and its effective
cache trashing.

Aggresively preempt a task if its avg overlap is very small, this should
avoid the task going to sleep and find it still running when we schedule
back to it - saving a wakeup.

Reported-by: Lin Ming <ming.m.lin@intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---

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