Re: Reporting a performance regression in sched/fair on Unixbench Shell Scripts with commit a53ce18cacb4

[Vincent Guittot]

On Fri, 30 Jun 2023 at 00:20, Saeed Mirzamohammadi
<saeed.mirzamohammadi@xxxxxxxxxx> wrote:
>
>
>
> > On Jun 21, 2023, at 9:41 AM, Saeed Mirzamohammadi <saeed.mirzamohammadi@xxxxxxxxxx> wrote:
> >
> > Hi Chen, Vincent,
> >
> >> On Jun 13, 2023, at 11:37 PM, Chen Yu <yu.c.chen@xxxxxxxxx> wrote:
> >>
> >> On 2023-06-13 at 19:35:55 +0000, Saeed Mirzamohammadi wrote:
> >>> Hi Vincent,
> >>>
> >>>> On Jun 9, 2023, at 9:52 AM, Vincent Guittot <vincent.guittot@xxxxxxxxxx> wrote:
> >>>>
> >>>> Hi Saeed,
> >>>>
> >>>> On Fri, 9 Jun 2023 at 00:48, Saeed Mirzamohammadi
> >>>> <saeed.mirzamohammadi@xxxxxxxxxx> wrote:
> >>>>>
> >>>>> Hi all,
> >>>>>
> >>>>> I’m reporting a regression of up to 8% with Unixbench Shell Scripts benchmarks after the following commit:
> >>>>>
> >>>>> Commit Data:
> >>>>> commit-id        : a53ce18cacb477dd0513c607f187d16f0fa96f71
> >>>>> subject          : sched/fair: Sanitize vruntime of entity being migrated
> >>>>> author           : vincent.guittot@xxxxxxxxxx
> >>>>> author date      : 2023-03-17 16:08:10
> >>>>>
> >>>>>
> >>>>> We have observed this on our v5.4 and v4.14 kernel and not yet tested 5.15 but I expect the same.
> >>>>
> >>>> It would be good to confirm that the regression is present on v6.3
> >>>> where the patch has been merged originally.  It can be that there is
> >>>> hidden dependency with other patches introduced since v5.4
> >>>
> >>> Regression is present on v6.3 as well, examples:
> >>> ub_gcc_224copies_Shell_Scripts_8_concurrent: ~6%
> >>> ub_gcc_224copies_Shell_Scripts_16_concurrent: ~8%
> >>> ub_gcc_448copies_Shell_Scripts_1_concurrent: ~2%
> >
> > Apologize for the confusion, I should correct the v6.3 upstream result above. v6.3 doesn’t have any regression.
> > v6.3.y -> no regression
> > v5.15.y -> no regression
> > v5.4.y -> 5-8% regression.
>
> A gentle reminder if there is any recommendation for v5.4.y and v4.14.y regression. Thanks!

I tried to find why the regression happens only for v5.4.y (or lower)
and not for v5.15.y (or above) but I haven't been able to find any
possible reason in the code.

Regarding the 2 commits below, they must come together so we can't
simply revert 1 and not the other.
commit 829c1651e9c4 sched/fair: sanitize vruntime of entity being placed
commit a53ce18cacb4 sched/fair: Sanitize vruntime of entity being migrated

entity_is_long_sleeper() should never return true in your case. Could
you try to check that it's the case for you ?





>
> >
> >
> >>>>
> >>>>
> >>>>>
> >>>>> ub_gcc_1copy_Shell_Scripts_1_concurrent  :  -0.01%
> >>>>> ub_gcc_1copy_Shell_Scripts_8_concurrent  :  -0.1%
> >>>>> ub_gcc_1copy_Shell_Scripts_16_concurrent  :  -0.12%%
> >>>>> ub_gcc_56copies_Shell_Scripts_1_concurrent  :  -2.29%%
> >>>>> ub_gcc_56copies_Shell_Scripts_8_concurrent  :  -4.22%
> >>>>> ub_gcc_56copies_Shell_Scripts_16_concurrent  :  -4.23%
> >>>>> ub_gcc_224copies_Shell_Scripts_1_concurrent  :  -5.54%
> >>>>> ub_gcc_224copies_Shell_Scripts_8_concurrent  :  -8%
> >>>>> ub_gcc_224copies_Shell_Scripts_16_concurrent  :  -7.05%
> >>>>> ub_gcc_448copies_Shell_Scripts_1_concurrent  :  -6.4%
> >>>>> ub_gcc_448copies_Shell_Scripts_8_concurrent  :  -8.35%
> >>>>> ub_gcc_448copies_Shell_Scripts_16_concurrent  :  -7.09%
> >>>>>
> >>>>> Link to unixbench:
> >>>>> github.com/kdlucas/byte-unixbench
> >>>>
> >>>> I tried to reproduce the problem with v6.3 on my system but I don't
> >>>> see any difference with or without the patch
> >>>>
> >>>> Do you have more details on your setup ? number of cpu and topology ?
> >>>>
> >>> model name  : Intel(R) Xeon(R) CPU E5-2690 v4 @ 2.60GHz
> >>>
> >>> Topology:
> >>> node   0   1
> >>> 0:  10  21
> >>> 1:  21  10
> >>>
> >>> Architecture:          x86_64
> >>> CPU op-mode(s):        32-bit, 64-bit
> >>> CPU(s):                56
> >>> On-line CPU(s) list:   0-55
> >>> Thread(s) per core:    2
> >>> Core(s) per socket:    14
> >>> Socket(s):             2
> >>> NUMA node(s):          2
> >>>
> >> Tested on a similar platform E5-2697 v2 @ 2.70GHz which has 2 nodes,
> >> 24 cores/48 CPUs in total, however I could not reproduce the issue.
> >> Since the regression was reported mainly against 224 and 448 copies case
> >> on your platform, I tested unixbench shell1 with 4 x 48 = 192 copies.
> >>
> >>
> >> a53ce18cacb477dd 213acadd21a080fc8cda8eebe6d
> >> ---------------- ---------------------------
> >>        %stddev     %change         %stddev
> >>            \          |                \
> >>    21304            +0.5%      21420        unixbench.score
> >>   632.43            +0.0%     632.44        unixbench.time.elapsed_time
> >>   632.43            +0.0%     632.44        unixbench.time.elapsed_time.max
> >> 11837046            -4.7%   11277727        unixbench.time.involuntary_context_switches
> >>   864713            +0.1%     865914        unixbench.time.major_page_faults
> >>     9600            +4.0%       9984        unixbench.time.maximum_resident_set_size
> >> 8.433e+08            +0.6%   8.48e+08        unixbench.time.minor_page_faults
> >>     4096            +0.0%       4096        unixbench.time.page_size
> >>     3741            +1.1%       3783        unixbench.time.percent_of_cpu_this_job_got
> >>    18341            +1.3%      18572        unixbench.time.system_time
> >>     5323            +0.6%       5353        unixbench.time.user_time
> >> 78197044            -3.1%   75791701        unixbench.time.voluntary_context_switches
> >> 57178573            +0.4%   57399061        unixbench.workload
> >>
> >> There is no much difference with a53ce18cacb477dd applied or not.
> >>
> >>
> >>
> >>
> >>
> >> a2e90611b9f425ad 829c1651e9c4a6f78398d3e6765
> >> ---------------- ---------------------------
> >>        %stddev     %change         %stddev
> >>            \          |                \
> >>    19985            +8.6%      21697        unixbench.score
> >>   632.64            -0.0%     632.53        unixbench.time.elapsed_time
> >>   632.64            -0.0%     632.53        unixbench.time.elapsed_time.max
> >> 11453985            +3.7%   11880259        unixbench.time.involuntary_context_switches
> >>   818996            +3.1%     844681        unixbench.time.major_page_faults
> >>     9600            +0.0%       9600        unixbench.time.maximum_resident_set_size
> >> 7.911e+08            +8.4%  8.575e+08        unixbench.time.minor_page_faults
> >>     4096            +0.0%       4096        unixbench.time.page_size
> >>     3767            -0.4%       3752        unixbench.time.percent_of_cpu_this_job_got
> >>    18873            -2.4%      18423        unixbench.time.system_time
> >>     4960            +7.1%       5313        unixbench.time.user_time
> >> 75436000           +10.8%   83581483        unixbench.time.voluntary_context_switches
> >> 53553404            +8.7%   58235303        unixbench.workload
> >>
> >> Previously with 829c1651e9c4a6f introduced, there is 8.6% improvement. And this improvement
> >> remains with a53ce18cacb477dd applied.
> >>
> >> Can you send the full test script so I can have a try locally?
> >
> > Thanks for testing this. For v5.4.y kernel (not for v6.3.y or v5.15.y), there is an 8% regression with the following test: ub_gcc_448copies_Shell_Scripts_8_concurrent
> > And that’s ’shell8’ with ‘-c 448’ copies passed as argument.
> >
> > Thanks,
> > Saeed
> >
> >>
> >> thanks,
> >> Chenyu
>