Messages in this thread | | | Subject | Re: [PATCH v3 0/5] Scan for an idle sibling in a single pass | From | "Li, Aubrey" <> | Date | Mon, 25 Jan 2021 12:29:47 +0800 |
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On 2021/1/22 21:22, Vincent Guittot wrote: > On Fri, 22 Jan 2021 at 11:14, Mel Gorman <mgorman@techsingularity.net> wrote: >> >> On Fri, Jan 22, 2021 at 10:30:52AM +0100, Vincent Guittot wrote: >>> Hi Mel, >>> >>> On Tue, 19 Jan 2021 at 13:02, Mel Gorman <mgorman@techsingularity.net> wrote: >>>> >>>> On Tue, Jan 19, 2021 at 12:33:04PM +0100, Vincent Guittot wrote: >>>>> On Tue, 19 Jan 2021 at 12:22, Mel Gorman <mgorman@techsingularity.net> wrote: >>>>>> >>>>>> Changelog since v2 >>>>>> o Remove unnecessary parameters >>>>>> o Update nr during scan only when scanning for cpus >>>>> >>>>> Hi Mel, >>>>> >>>>> I haven't looked at your previous version mainly because I'm chasing a >>>>> performance regression on v5.11-rcx which prevents me from testing the >>>>> impact of your patchset on my !SMT2 system. >>>>> Will do this as soon as this problem is fixed >>>>> >>>> >>>> Thanks, that would be appreciated as I do not have access to a !SMT2 >>>> system to do my own evaluation. >>> >>> I have been able to run tests with your patchset on both large arm64 >>> SMT4 system and small arm64 !SMT system and patch 3 is still a source >>> of regression on both. Decreasing min number of loops to 2 instead of >>> 4 and scaling it with smt weight doesn't seem to be a good option as >>> regressions disappear when I remove them as I tested with the patch >>> below >>> >>> hackbench -l 2560 -g 1 on 8 cores arm64 >>> v5.11-rc4 : 1.355 (+/- 7.96) >>> + sis improvement : 1.923 (+/- 25%) >>> + the patch below : 1.332 (+/- 4.95) >>> >>> hackbench -l 2560 -g 256 on 8 cores arm64 >>> v5.11-rc4 : 2.116 (+/- 4.62%) >>> + sis improvement : 2.216 (+/- 3.84%) >>> + the patch below : 2.113 (+/- 3.01%) >>>
4 benchmarks reported out during weekend, with patch 3 on a x86 4s system with 24 cores per socket and 2 HT per core, total 192 CPUs.
It looks like mid-load has notable changes on my side: - netperf 50% num of threads in TCP mode has 27.25% improved - tbench 50% num of threads has 9.52% regression
Details below:
hackbench: 10 iterations, 10000 loops, 40 fds per group ======================================================
- pipe process
group base %std patch %std 6 1 5.27 1.0469 8.53 12 1 1.03 1.0398 1.44 24 1 2.36 1.0275 3.34
- pipe thread
group base %std patch %std 6 1 7.48 1.0747 5.25 12 1 0.97 1.0432 1.95 24 1 7.01 1.0299 6.81
- socket process
group base %std patch %std 6 1 1.01 0.9656 1.09 12 1 0.35 0.9853 0.49 24 1 1.33 0.9877 1.20
- socket thread
group base %std patch %std 6 1 2.52 0.9346 2.75 12 1 0.86 0.9830 0.66 24 1 1.17 0.9791 1.23
netperf: 10 iterations x 100 seconds, transactions rate / sec =============================================================
- tcp request/response performance
thread base %std patch %std 50% 1 3.98 1.2725 7.52 100% 1 2.73 0.9446 2.86 200% 1 39.36 0.9955 29.45
- udp request/response performance
thread base %std patch %std 50% 1 6.18 1.0704 11.99 100% 1 47.85 0.9637 45.83 200% 1 45.74 1.0162 36.99
tbench: 10 iterations x 100 seconds, throughput / sec =====================================================
thread base %std patch %std 50% 1 1.38 0.9048 2.46 100% 1 1.05 0.9640 0.68 200% 1 6.76 0.9886 2.86
schbench: 10 iterations x 100 seconds, 99th percentile latency ==============================================================
mthread base %std patch %std 6 1 29.07 0.8714 25.73 12 1 15.32 1.0000 12.39 24 1 0.08 0.9996 0.01
>>> So starting with a min of 2 loops instead of 4 currently and scaling >>> nr loop with smt weight doesn't seem to be a good option and we should >>> remove it for now >>> >> Note that this is essentially reverting the patch. As you remove "nr *= >> sched_smt_weight", the scan is no longer proportional to cores, it's > > Yes. My goal above was to narrow the changes only to lines that > generate the regressions but i agree that removing patch 3 is the > right solution> >> proportial to logical CPUs and the rest of the patch and changelog becomes >> meaningless. On that basis, I'll queue tests over the weekend that remove >> this patch entirely and keep the CPU scan as a single pass. >> >> -- >> Mel Gorman >> SUSE Labs
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