linux-kernel - Re: [PATCH v2 1/3] sched/fair: fix rounding issue for asym packing

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Message-ID: <CAKfTPtCVqSYOC_GUdBm8_5KNMNEwXdf77mXL4SDB4_G5_iE0iA@mail.gmail.com>
Date:   Wed, 19 Dec 2018 16:05:59 +0100
From:   Vincent Guittot <vincent.guittot@...aro.org>
To:     Valentin Schneider <valentin.schneider@....com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Morten Rasmussen <Morten.Rasmussen@....com>
Subject: Re: [PATCH v2 1/3] sched/fair: fix rounding issue for asym packing

On Wed, 19 Dec 2018 at 15:59, Valentin Schneider
<valentin.schneider@....com> wrote:
>
>
>
> On 19/12/2018 13:39, Vincent Guittot wrote:
> [...]
> >> I used that setup out of convenience for myself, but AFAICT that use-case
> >> just stresses that issue.
> >
> > After looking at you UC in details, your problem comes from the wl=1
> > for cpu0 whereas there is no running task.
> > But wl!=0 without running task should not be possible since fdf5f3
> > ("wsched/fair: Disable LB_BIAS by default")
> >
> > This explain the 1023 instead of 1022
> >
> >
>
> True, I had a look at the trace and there doesn't seem to be any running
> task on that CPU. That's a separate matter however - the rounding issues
> can happen regardless of the wl values.

But it means that the rounding fix +1 works and your problems comes
from something else