Re: [RFC PATCH 3/3] sched/fair: Use different cachelines for readers and writers of load_avg

From: Peter Zijlstra
Date: Mon Nov 30 2015 - 17:10:08 EST


On Mon, Nov 30, 2015 at 02:13:32PM -0500, Waiman Long wrote:
> >This begs the question tough; why are you running a global load in a
> >cgroup; and do we really need to update this for the root cgroup? It
> >seems to me we don't need calc_tg_weight() for the root cgroup, it
> >doesn't need to normalize its weight numbers.
> >
> >That is; isn't this simply a problem we should avoid?
>
> I didn't use any cgroup in my test setup. Autogroup was enabled, though.
> Booting up a 4.4-rc2 kernel caused sched_create_group() to be called 56
> times.

Yeah, can you kill autogroup and see if that helps? If not, we probably
should add some code to avoid calculating things for the root group.
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