Commit abfafa54 authored Sep 13, 2013 by Jason Low Committed by Ingo Molnar Sep 20, 2013

sched: Reduce overestimating rq->avg_idle



When updating avg_idle, if the delta exceeds some max value, then avg_idle
gets set to the max, regardless of what the previous avg was. This can cause
avg_idle to often be overestimated.

This patch modifies the way we update avg_idle by always updating it with the
function call to update_avg() first. Then, if avg_idle exceeds the max, we set
it to the max.

Signed-off-by: Jason Low <jason.low2@hp.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Reviewed-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1379096813-3032-2-git-send-email-jason.low2@hp.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 7aff2e3a

kernel/sched/core.c

+4 −3

Original line number	Diff line number	Diff line
		@@ -1332,10 +1332,11 @@ ttwu_do_wakeup(struct rq rq, struct task_struct p, int wake_flags)
		u64 delta = rq_clock(rq) - rq->idle_stamp;
		u64 max = 2*sysctl_sched_migration_cost;

		if (delta > max)
		rq->avg_idle = max;
		else
		update_avg(&rq->avg_idle, delta);

		if (rq->avg_idle > max)
		rq->avg_idle = max;

		rq->idle_stamp = 0;
		}
		#endif

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