linux-kernel - Re: [PATCH v2 0/4] Mitigate inconsistent NUMA imbalance behaviour

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Date:   Tue, 31 May 2022 15:09:24 +0100
From:   Mel Gorman <mgorman@...hsingularity.net>
To:     Vincent Guittot <vincent.guittot@...aro.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Valentin Schneider <valentin.schneider@....com>,
        K Prateek Nayak <kprateek.nayak@....com>,
        Aubrey Li <aubrey.li@...ux.intel.com>,
        Ying Huang <ying.huang@...el.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 0/4] Mitigate inconsistent NUMA imbalance behaviour

On Tue, May 31, 2022 at 12:26:51PM +0200, Vincent Guittot wrote:
> > # cd work/log
> > # ../../compare-kernels.sh
> >
> > nas-mpich-mg NAS Time
> >                                  test
> >                              mgD-many
> > Min       mg.D       95.80 (   0.00%)
> > Amean     mg.D      110.77 (   0.00%)
> > Stddev    mg.D       21.55 (   0.00%)
> > CoeffVar  mg.D       19.46 (   0.00%)
> > Max       mg.D      155.35 (   0.00%)
> > BAmean-50 mg.D       96.05 (   0.00%)
> > BAmean-95 mg.D      107.83 (   0.00%)
> > BAmean-99 mg.D      109.23 (   0.00%)
> >
> > Note the min of 95.80 seconds, max of 155.35 and high stddev indicating
> > the results are not stable.
> >
> > The generated config is for openSUSE so it may not work for you. After
> > installing the mpich package, you'll need to adjust these lines
> >
> > export NAS_MPICH_PATH=/usr/$MMTESTS_LIBDIR/mpi/gcc/$NAS_MPICH_VERSION/bin
> > export NAS_MPICH_LIBPATH=/usr/$MMTESTS_LIBDIR/mpi/gcc/$NAS_MPICH_VERSION/$MMTESTS_LIBDIR
> >
> > NAS_MPICH_PATH and NAS_MPICH_LIBPATH need to point to the bin and lib
> > path for the mpich package your distribution ships.
> 
> I have been able to run your tests on my setup: aarch64 2 nodes * 28
> cores * 4 threads. But I can't reproduce the problem, results stay
> stable before and after reverting c6f886546cb8.
> 

It's unfortunate but not surprising that it's not perfectly reproducible
given that I expect this to be a race of some description and not all
machines will observe the problem.

Thanks for trying.

-- 
Mel Gorman
SUSE Labs