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

[Chen Yu]

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%
> > 
> > 
> >> 
> >> 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,
Chenyu