linux-kernel - Re: [PATCH v4 11/11] sched/fair: rework find_idlest

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Date:   Wed, 20 Nov 2019 17:34:31 +0000
From:   Qais Yousef <qais.yousef@....com>
To:     Vincent Guittot <vincent.guittot@...aro.org>
Cc:     linux-kernel <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Phil Auld <pauld@...hat.com>,
        Valentin Schneider <valentin.schneider@....com>,
        Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
        Quentin Perret <quentin.perret@....com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Morten Rasmussen <Morten.Rasmussen@....com>,
        Hillf Danton <hdanton@...a.com>,
        Parth Shah <parth@...ux.ibm.com>,
        Rik van Riel <riel@...riel.com>
Subject: Re: [PATCH v4 11/11] sched/fair: rework find_idlest_group

On 11/20/19 17:53, Vincent Guittot wrote:
> On Wed, 20 Nov 2019 at 14:21, Vincent Guittot
> <vincent.guittot@...aro.org> wrote:
> >
> > Hi Qais,
> >
> > On Wed, 20 Nov 2019 at 12:58, Qais Yousef <qais.yousef@....com> wrote:
> > >
> > > Hi Vincent
> > >
> > > On 10/18/19 15:26, Vincent Guittot wrote:
> > > > The slow wake up path computes per sched_group statisics to select the
> > > > idlest group, which is quite similar to what load_balance() is doing
> > > > for selecting busiest group. Rework find_idlest_group() to classify the
> > > > sched_group and select the idlest one following the same steps as
> > > > load_balance().
> > > >
> > > > Signed-off-by: Vincent Guittot <vincent.guittot@...aro.org>
> > > > ---
> > >
> > > LTP test has caught a regression in perf_event_open02 test on linux-next and I
> > > bisected it to this patch.
> > >
> > > That is checking out next-20191119 tag and reverting this patch on top the test
> > > passes. Without the revert the test fails.
> 
> I haven't tried linux-next yet but LTP test is passed with
> tip/sched/core, which includes this patch, on hikey960 which is arm64
> too.
> 
> Have you tried tip/sched/core on your juno ? this could help to
> understand if it's only for juno or if this patch interact with
> another branch merged in linux next

Okay will give it a go. But out of curiosity, what is the output of your run?

While bisecting on linux-next I noticed that at some point the test was
passing but all the read values were 0. At some point I started seeing
none-zero values.

--
Qais Yousef