linux-kernel - Re: [v4.8-rc1 Regression] sched/fair: Apply more PELT fixes

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Message-ID: <CAKfTPtDo7PsZjDSH4KteyCJ=yq63Ha5iwkucjRTvtP_J3o=MKw@mail.gmail.com>
Date:   Wed, 12 Oct 2016 14:20:42 +0200
From:   Vincent Guittot <vincent.guittot@...aro.org>
To:     Joseph Salisbury <joseph.salisbury@...onical.com>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>,
        Mike Galbraith <efault@....de>
Subject: Re: [v4.8-rc1 Regression] sched/fair: Apply more PELT fixes

On 8 October 2016 at 13:49, Mike Galbraith <efault@....de> wrote:
> On Sat, 2016-10-08 at 13:37 +0200, Vincent Guittot wrote:
>> On 8 October 2016 at 10:39, Ingo Molnar <mingo@...nel.org> wrote:
>> >
>> > * Peter Zijlstra <peterz@...radead.org> wrote:
>> >
>> > > On Fri, Oct 07, 2016 at 03:38:23PM -0400, Joseph Salisbury wrote:
>> > > > Hello Peter,
>> > > >
>> > > > A kernel bug report was opened against Ubuntu [0].  After a
>> > > > kernel
>> > > > bisect, it was found that reverting the following commit
>> > > > resolved this bug:
>> > > >
>> > > > commit 3d30544f02120b884bba2a9466c87dba980e3be5
>> > > > Author: Peter Zijlstra <peterz@...radead.org>
>> > > > Date:   Tue Jun 21 14:27:50 2016 +0200
>> > > >
>> > > >     sched/fair: Apply more PELT fixes
>>
>> This patch only speeds up the update of task group load in order to
>> reflect the new load balance but It should not change the final value
>> and as a result the final behavior. I will try to reproduce it in my
>> target later today
>
> FWIW, I tried and failed w/wo autogroup on 4.8 and master.

Me too

Is it possible to get some dump of  /proc/sched_debug while the problem occurs ?

Vincent

>         -Mike