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

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Date:   Mon, 5 Oct 2020 10:04:56 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Mel Gorman <mgorman@...e.de>,
        kernel test robot <rong.a.chen@...el.com>,
        Vincent Guittot <vincent.guittot@...aro.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>,
        Mike Galbraith <efault@....de>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>, lkp@...ts.01.org,
        lkp@...el.com, ying.huang@...el.com, feng.tang@...el.com,
        zhengjun.xing@...el.com, aubrey.li@...ux.intel.com,
        yu.c.chen@...el.com
Subject: Re: [sched/fair] fcf0553db6: netperf.Throughput_Mbps -30.8%
 regression


* Peter Zijlstra <peterz@...radead.org> wrote:

> On Sun, Oct 04, 2020 at 05:21:08PM +0100, Mel Gorman 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")
> > > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master
> > > 
> > 
> > This commit was the start of a series that made large changes to load
> > balancing.  The series was not bisect-safe and has since been reconciled
> > with the NUMA balancing. Any workload with a potential load balancing
> > problem has to be checked against the latest kernel to see if the problem
> > persists there. If it does, then tip/sched/core should be checked or
> > 5.10-rc1 when it comes out as tip has a few more LB changes pending.
> 
> What Mel said ;-)

Basically it would be nice to test either the following commit directly 
(which is the latest relevant sched/core commit):

   233e7aca4c8a: ("sched/fair: Use dst group while checking imbalance for NUMA balancer")

Or a -next version that includes these commits.

Thanks,

	Ingo