linux-kernel - Re: [RFC PATCH v2] sched/fair: select idle cpu from idle cpumask in sched domain

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Message-ID: <CAKfTPtCvQ41-mqvYXc-DWnz3y5byw_OsmHNfc7UvczC-nwWMUg@mail.gmail.com>
Date:   Fri, 25 Sep 2020 08:50:55 +0200
From:   Vincent Guittot <vincent.guittot@...aro.org>
To:     Tim Chen <tim.c.chen@...ux.intel.com>
Cc:     "Li, Aubrey" <aubrey.li@...ux.intel.com>,
        Mel Gorman <mgorman@...e.de>, Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>,
        Valentin Schneider <valentin.schneider@....com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Qais Yousef <qais.yousef@....com>,
        Jiang Biao <benbjiang@...il.com>
Subject: Re: [RFC PATCH v2] sched/fair: select idle cpu from idle cpumask in
 sched domain

Hi Tim

On Thu, 24 Sep 2020 at 18:37, Tim Chen <tim.c.chen@...ux.intel.com> wrote:
>
>
>
> On 9/22/20 12:14 AM, Vincent Guittot wrote:
>
> >>
> >>>>
> >>>> And a quick test with hackbench on my octo cores arm64 gives for 12
>
> Vincent,
>
> Is it octo (=10) or octa (=8) cores on a single socket for your system?

it's a 8 cores and the cores are splitted in 2 cache domains

> The L2 is per core or there are multiple L2s shared among groups of cores?
>
> Wonder if placing the threads within a L2 or not within
> an L2 could cause differences seen with Aubrey's test.

I haven't checked recently but the 2 tasks involved in sched pipe run
on CPUs which belong to the same cache domain

Vincent

>
> Tim
>