linux-kernel - Re: [sched/fair] fcf0553db6: netperf.Throughput

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Date:   Mon, 5 Oct 2020 09:12:37 +0200
From:   Vincent Guittot <vincent.guittot@...aro.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     kernel test robot <rong.a.chen@...el.com>,
        Ingo Molnar <mingo@...nel.org>,
        Rik van Riel <riel@...riel.com>,
        Ben Segall <bsegall@...gle.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Mel Gorman <mgorman@...e.de>, Mike Galbraith <efault@....de>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>, lkp@...ts.01.org,
        kbuild test robot <lkp@...el.com>,
        "Huang, Ying" <ying.huang@...el.com>,
        "Tang, Feng" <feng.tang@...el.com>, zhengjun.xing@...el.com,
        Aubrey Li <aubrey.li@...ux.intel.com>,
        Chen Yu <yu.c.chen@...el.com>
Subject: Re: [sched/fair] fcf0553db6: netperf.Throughput_Mbps -30.8% regression

On Mon, 5 Oct 2020 at 08:50, Peter Zijlstra <peterz@...radead.org> wrote:
>
> On Sun, Oct 04, 2020 at 09:27:16PM +0800, kernel test robot wrote:
> > Greeting,
> >
> > FYI, we noticed a -30.8% regression of netperf.Throughput_Mbps due to commit:
> >
> >
> > commit: fcf0553db6f4c79387864f6e4ab4a891601f395e ("sched/fair: Remove meaningless imbalance calculation")
>
> This is the middle of a series that reworks the load balancer. Does this
> regression still exist at the end of it?
>
> Which would be around:
>
>   57abff067a08 ("sched/fair: Rework find_idlest_group()")
>
> or possible a little later, Vincent?

I would consider 6cf82d559e1a ("sched/cfs: fix spurious active migration")

But even then, some fixes have been added. Mel perfectly described that