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SubjectRe: [PATCH v4 04/11] sched/fair: rework load_balance
On Tue, 12 Nov 2019 at 16:06, Mel Gorman <mgorman@techsingularity.net> wrote:
>
> On Tue, Nov 12, 2019 at 11:58:30AM +0100, Vincent Guittot wrote:
> > > This roughly matches what I've seen. The interesting part to me for
> > > netperf is the next section of the report that reports the locality of
> > > numa hints. With netperf on a 2-socket machine, it's generally around
> > > 50% as the client/server are pulled apart. Because netperf is not
> > > heavily memory bound, it doesn't have much impact on the overall
> > > performance but it's good at catching the cross-node migrations.
> >
> > Ok. I didn't want to make my reply too long. I have put them below for
> > the netperf-tcp results:
> > 5.3-rc2 5.3-rc2
> > tip +rwk+fix
> > Ops NUMA alloc hit 60077762.00 60387907.00
> > Ops NUMA alloc miss 0.00 0.00
> > Ops NUMA interleave hit 0.00 0.00
> > Ops NUMA alloc local 60077571.00 60387798.00
> > Ops NUMA base-page range updates 5948.00 17223.00
> > Ops NUMA PTE updates 5948.00 17223.00
> > Ops NUMA PMD updates 0.00 0.00
> > Ops NUMA hint faults 4639.00 14050.00
> > Ops NUMA hint local faults % 2073.00 6515.00
> > Ops NUMA hint local percent 44.69 46.37
> > Ops NUMA pages migrated 1528.00 4306.00
> > Ops AutoNUMA cost 23.27 70.45
> >
>
> Thanks -- it was "NUMA hint local percent" I was interested in and the
> 46.37% local hinting faults is likely indicative of the client/server
> being load balanced across SD_NUMA domains without NUMA Balancing being
> aggressive enough to fix it. At least I know I am not just seriously
> unlucky or testing magical machines!

I agree that the collaboration between load balanced across SD_NUMA
level and NUMA balancing should be improved

It's also interesting to notice that the patchset doesn't seem to do
worse than the baseline: 46.37% vs 44.69%

Vincent

>
> --
> Mel Gorman
> SUSE Labs

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