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sched: wakeup preempt when small overlap

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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>
This commit is contained in:
Peter Zijlstra
2008-09-20 23:38:02 +02:00
committed by Ingo Molnar
parent 09b22a2f67
commit 15afe09bf4
6 changed files with 22 additions and 14 deletions
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include/linux/sched.h
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@@ -897,7 +897,7 @@ struct sched_class {
void (*yield_task) (struct rq *rq);
int (*select_task_rq)(struct task_struct *p, int sync);
void (*check_preempt_curr) (struct rq *rq, struct task_struct *p);
void (*check_preempt_curr) (struct rq *rq, struct task_struct *p, int sync);
struct task_struct * (*pick_next_task) (struct rq *rq);
void (*put_prev_task) (struct rq *rq, struct task_struct *p);