linux-kernel - Re: [PATCH 2/2] sched/fair: Always propagate runnable_load

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Message-ID: <20170504174341.GC7288@htj.duckdns.org>
Date:   Thu, 4 May 2017 13:43:41 -0400
From:   Tejun Heo <tj@...nel.org>
To:     Vincent Guittot <vincent.guittot@...aro.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        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: [PATCH 2/2] sched/fair: Always propagate runnable_load_avg

Hello,

On Thu, May 04, 2017 at 10:19:46AM +0200, Vincent Guittot wrote:
> > schbench inside a cgroup and have some base load, it is actually
> > expected to show worse latency.  You need to give higher weight to the
> > cgroup matching the number of active threads (to be accruate, scaled
> > by duty cycle but shouldn't matter too much in practice).
> 
> I don't have to change anything cgroup weight with mainline to get
> good number which means that the base load which is quite close to
> null, is probably not the problem

So, while that *could* be the case, it could also be the baseline
incorrectly favoring the nested cfs_rqs over other tasks because of
the nested runnables being inflated with blocked load avgs.  I think
it'd be a good idea to test with matching weight to put things on the
even ground.

Thanks.

-- 
tejun