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

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Message-ID: <8ea1a96c-c2e0-cc3f-1cec-444706383e77@arm.com>
Date:   Wed, 19 Dec 2018 14:59:39 +0000
From:   Valentin Schneider <valentin.schneider@....com>
To:     Vincent Guittot <vincent.guittot@...aro.org>
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 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.