linux-kernel - Re: [PATCH 2/2] sched/numa: Delay retrying placement for automatic NUMA balance after wake

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Date:   Mon, 12 Feb 2018 17:52:57 +0000
From:   Mel Gorman <mgorman@...hsingularity.net>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Mike Galbraith <efault@....de>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] sched/numa: Delay retrying placement for automatic
 NUMA balance after wake_affine

On Mon, Feb 12, 2018 at 06:34:49PM +0100, Peter Zijlstra wrote:
> On Mon, Feb 12, 2018 at 05:11:31PM +0000, Mel Gorman wrote:
> 
> > However, the benefit in other cases is large. This is the result for NAS
> > with the D class sizing on a 4-socket machine
> > 
> >                           4.15.0                 4.15.0
> >                     sdnuma-v1r23       delayretry-v1r23
> > Time cg.D      557.00 (   0.00%)      431.82 (  22.47%)
> > Time ep.D       77.83 (   0.00%)       79.01 (  -1.52%)
> > Time is.D       26.46 (   0.00%)       26.64 (  -0.68%)
> > Time lu.D      727.14 (   0.00%)      597.94 (  17.77%)
> > Time mg.D      191.35 (   0.00%)      146.85 (  23.26%)
> 
> Last time I checked, we were some ~25% from OMP_PROC_BIND with NAS, this
> seems to close that hole significantly. Do you happen to have
> OMP_PROC_BIND numbers handy to see how far away we are from manual
> affinity?
> 

OMP_PROC_BIND implies openmp and this particular test was using MPI for
parallisation. I'll look into doing an openmp comparison and see what it
looks like with OMP_PROC_BIND set.

-- 
Mel Gorman
SUSE Labs