linux-kernel - Re: [RFC PATCHSET v2] sched/fair: fix load balancer behavior when cgroup is in use

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Date:   Fri, 5 May 2017 10:46:53 +0200
From:   Vincent Guittot <vincent.guittot@...aro.org>
To:     Tejun Heo <tj@...nel.org>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Mike Galbraith <efault@....de>, Paul Turner <pjt@...gle.com>,
        Chris Mason <clm@...com>, kernel-team@...com
Subject: Re: [RFC PATCHSET v2] sched/fair: fix load balancer behavior when
 cgroup is in use

Hi Tejun,

On 4 May 2017 at 22:28, Tejun Heo <tj@...nel.org> wrote:
> Hello,
>
> v1 posting can be found at
>
>   http://lkml.kernel.org/r/20170424201344.GA14169@wtj.duckdns.org
>
> The patchset is still RFC and based on v4.11.  I used Peter's updated
> calc_cfs_shares() instead of scaling manually and updated so that
> runnable_load_avg is propagated independently from load_avg.  Due to
> the way sched_entity and cfs_rq loads are calculated, this requires an
> extra runnable_load_avg calculation for group sched_entities, but the
> end result is cleaner and actually makes sense.
>
> Vincent, can you please verify whether the regression that you see is
> gone with this version?

schbench results looks better with this version
Latency percentiles (usec)
50.0000th: 212
75.0000th: 292
90.0000th: 385
95.0000th: 439
*99.0000th: 671
99.5000th: 7992
99.9000th: 12176
min=0, max=14855

p99 is back to a normal value but p99.5 stays higher than mainline

I have also checked load_avg and runnable_load_avg value and there is
something incorrect. I will provide details on the related patch

Regards,
Vincent
>
> Thanks.
>
> --
> tejun