Messages in this thread | | | Date | Mon, 2 Nov 2020 16:52:30 +0000 | From | Mel Gorman <> | Subject | Re: [PATCH v1] sched/fair: update_pick_idlest() Select group with lowest group_util when idle_cpus are equal |
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On Mon, Nov 02, 2020 at 09:44:18AM -0500, Phil Auld wrote: > > I'm going to have a look at the regressions and see if patches that > > have been queued for v5.10 or even more recent patch can help or if > > the patch should be adjusted > > > > Fwiw, we have pulled this in, along with some of the 5.10-rc1 fixes in this > area and in the load balancing code. >
I assume you mean a distro kernel but in this case, all the bisections were vanilla mainline.
> We found some load balancing improvements and some minor overall perf > gains in a few places, but generally did not see any difference from before > the commit mentioned here. > > I'm wondering, Mel, if you have compared 5.10-rc1? >
No, but it's queued now -- 5.9 vs 5.9-revert vs 5.10-rc2 vs 5.10-rc2-revert. It's only one machine queued but hopefully it'll reproduce. Both 5.9 and 5.10 are being tested in case one of the changes merged in 5.10 mask the problem. Ordinarily I would have checked first but I'm backlogged so I took a report-first-test-later approach this time around.
> We don't have everything though so it's possible something we have > not pulled back is interacting with this patch, or we are missing something > in our testing, or it's better with the later fixes in 5.10 or ... > something else :) >
Add userspace differences, core counts, CPU generation, volume of scheduler changes with interactions, different implementations of tests, masking from cpufreq changes, phase of the moon and just general plain old bad luck.
> I'll try to see if we can run some direct 5.8 - 5.9 tests like these. >
That would be nice. While I often see false positive bisections for performance bugs, the number of identical reports and different machines made this more suspicious.
-- Mel Gorman SUSE Labs
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