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Date: Wed, 26 Apr 2017 15:27:44 -0700
From: Tejun Heo <tj@kernel.org>
To: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Ingo Molnar <mingo@redhat.com>, Peter Zijlstra <peterz@infradead.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Mike Galbraith <efault@gmx.de>, Paul Turner <pjt@google.com>,
        Chris Mason <clm@fb.com>, kernel-team@fb.com
Subject: Re: [PATCH 1/2] sched/fair: Fix how load gets propagated from cfs_rq
 to its sched_entity
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Hello, Vincent.

On Wed, Apr 26, 2017 at 06:14:17PM +0200, Vincent Guittot wrote:
> > +       if (gcfs_rq->load.weight) {
> > +               long shares = calc_cfs_shares(gcfs_rq, gcfs_rq->tg);
> >
> > +               load = min(gcfs_rq->runnable_load_avg *
> > +                          shares / gcfs_rq->load.weight, shares);
> 
> There is a unit problem above:
> runnable_load_avg and shares are not in the same range but
> runnable_load_avg and  scale_load_down(gcfs_rq->load.weight) are so
> you should use
> gcfs_rq->runnable_load_avg * scale_load_down(shares) /
> scale_load_down(gcfs_rq->load.weight).

But the only difference there is that we lose accuracy in calculation;
otherwise, the end results are the same, no?

> Hopefully both  scale_load_down cancel between them
> But the min should be then tested with scale_load_down(shares) and not
> only shares

Ah, that's right.  The min should be against scaled down shares.

Thanks.

-- 
tejun