Messages in this thread | | | From | Vincent Guittot <> | Date | Thu, 10 Dec 2020 10:38:37 +0100 | Subject | Re: [PATCH 0/4] Reduce scanning of runqueues in select_idle_sibling |
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On Thu, 10 Dec 2020 at 09:00, Vincent Guittot <vincent.guittot@linaro.org> wrote: > > On Wed, 9 Dec 2020 at 15:37, Mel Gorman <mgorman@techsingularity.net> wrote: > > > > On Tue, Dec 08, 2020 at 03:34:57PM +0000, Mel Gorman wrote: > > > Changelog since v1 > > > o Drop single-pass patch (vincent) > > > o Scope variables used for SIS_AVG_CPU (dietmar) > > > o Remove redundant assignment (dietmar > > > > > > This reduces the amount of runqueue scanning in select_idle_sibling in > > > the worst case. > > > > > > Patch 1 removes SIS_AVG_CPU because it's unused. > > > > > > Patch 2 moves all SIS_PROP-related calculations under SIS_PROP > > > > > > Patch 3 improves the hit rate of p->recent_used_cpu to reduce the amount > > > of scanning. It should be relatively uncontroversial > > > > > > Patch 4 returns an idle candidate if one is found while scanning for a > > > free core. > > > > > > > Any other objections to the series? Vincent marked 1, 3 and 4 as > > reviewed. While patch 2 had some mild cosmetic concerns, I think the > > version and how it treats SIS_PROP is fine as it is to keep it > > functionally equivalent to !SIS_PROP and without adding too many > > SIS_PROP checks. > > while testing your patchset and Aubrey one on top of tip, I'm facing > some perf regression on my arm64 numa system on hackbench and reaim. > The regression seems to comes from your patchset but i don't know > which patch in particular yet > > hackbench -l 256000 -g 1 > > v5.10-rc7 + tip/sched/core 13,255(+/- 3.22%) > with your patchset 15.368(+/- 2.74) -15.9% > > I'm also seeing perf regression on reaim but this one needs more > investigation before confirming > > TBH, I was not expecting regressions. I'm running more test to find > which patch is the culprit
The regression comes from patch 3: sched/fair: Do not replace recent_used_cpu with the new target
> > > > > > -- > > Mel Gorman > > SUSE Labs
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