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From:   Vincent Guittot <vincent.guittot@linaro.org>
Date:   Mon, 11 Jan 2021 15:39:29 +0100
Message-ID: <CAKfTPtDk3+96ZuytRAPA3ZBqW-whzn3cbGmwgS7ZfyoPaTTKnA@mail.gmail.com>
Subject: Re: [RFC][PATCH 1/5] sched/fair: Fix select_idle_cpu()s cost accounting
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     Mel Gorman <mgorman@techsingularity.net>,
        "Li, Aubrey" <aubrey.li@linux.intel.com>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Ingo Molnar <mingo@redhat.com>,
        Juri Lelli <juri.lelli@redhat.com>,
        Valentin Schneider <valentin.schneider@arm.com>,
        Qais Yousef <qais.yousef@arm.com>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Ben Segall <bsegall@google.com>,
        Tim Chen <tim.c.chen@linux.intel.com>,
        Jiang Biao <benbjiang@gmail.com>
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On Fri, 8 Jan 2021 at 20:45, Peter Zijlstra <peterz@infradead.org> wrote:
>
> On Fri, Jan 08, 2021 at 04:10:51PM +0100, Vincent Guittot wrote:
> > Also, there is another problem (that I'm investigating)  which is that
> > this_rq()->avg_idle is stalled when your cpu is busy. Which means that
> > this avg_idle can just be a very old and meaningless value. I think
> > that we should decay it periodically to reflect there is less and less
>
> https://lkml.kernel.org/r/20180530143105.977759909@infradead.org
>
> :-)

:-)

I was more thinking of something like decaying avg_idle during
tick_fair but at leat we all agree that we can't stay with a stalled
avg_idle value