Re: [RFC] vmstat: Avoid waking up idle-cpu to service shepherd work

[Michal Hocko]

On Thu 26-03-15 11:09:01, Viresh Kumar wrote:
> A delayed work to schedule vmstat_shepherd() is queued at periodic intervals for
> internal working of vmstat core. This work and its timer end up waking an idle
> cpu sometimes, as this always stays on CPU0.
> 
> Because we re-queue the work from its handler, idle_cpu() returns false and so
> the timer (used by delayed work) never migrates to any other CPU.
> 
> This may not be the desired behavior always as waking up an idle CPU to queue
> work on few other CPUs isn't good from power-consumption point of view.

Wouldn't something like I was suggesting few months back
(http://article.gmane.org/gmane.linux.kernel.mm/127569) solve this
problem as well? Scheduler should be idle aware, no? I mean it shouldn't
wake up an idle CPU if the task might run on another one.
-- 
Michal Hocko
SUSE Labs
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