linux-kernel - Reporting a performance regression in sched/fair on Unixbench Shell Scripts with commit a53ce18cacb4

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Date:   Thu, 8 Jun 2023 22:48:29 +0000
From:   Saeed Mirzamohammadi <saeed.mirzamohammadi@...cle.com>
To:     Ingo Molnar <mingo@...hat.com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "vincent.guittot@...aro.org" <vincent.guittot@...aro.org>,
        "zhangqiao22@...wei.com" <zhangqiao22@...wei.com>
Subject: Reporting a performance regression in sched/fair on Unixbench Shell
 Scripts with commit a53ce18cacb4

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@...aro.org
 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.

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

Info about benchmark:
 "The shells scripts test measures the number of times per minute a
  process can start and reap a set of one, two, four and eight concurrent
copies of a shell scripts where the shell script applies a series of
transformation to a data file”

I have also evaluated performance before and after both of these two commits (one if fixing the other) but I still observe the same regression (C1 is still the source of regression).
C1. a53ce18cacb4 sched/fair: Sanitize vruntime of entity being migrated
C2. 829c1651e9c4 sched/fair: sanitize vruntime of entity being placed

Thank you very much,
Saeed