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

[Peter Zijlstra]

On Mon, Nov 30, 2015 at 10:55:02PM -0500, Waiman Long wrote:
> On 11/30/2015 05:09 PM, Peter Zijlstra wrote:
> >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.
> 
> I will try that out tomorrow. However, SCHED_AUTOGROUP was enabled in the
> distribution kernels. So we still need to look at that with autogroup
> enabled.

Meh, or just tell the people that have stupid large machines to use
noautogroup on boot (its of questionable benefit in the first place imo,
esp. on servers).
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