linux-kernel - Re: [thermal] 9223d0dccb: stress-ng.msg.ops_per

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Message-ID: <20210413172827.GC17097@zn.tnic>
Date:   Tue, 13 Apr 2021 19:28:27 +0200
From:   Borislav Petkov <bp@...e.de>
To:     kernel test robot <oliver.sang@...el.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        LKML <linux-kernel@...r.kernel.org>, lkp@...ts.01.org,
        lkp@...el.com, ying.huang@...el.com, feng.tang@...el.com,
        zhengjun.xing@...el.com
Subject: Re: [thermal]  9223d0dccb:  stress-ng.msg.ops_per_sec -27.4%
 regression

On Tue, Apr 13, 2021 at 09:58:01PM +0800, kernel test robot wrote:
> Greeting,
> 
> FYI, we noticed a -27.4% regression of stress-ng.msg.ops_per_sec due to commit:
> 
> 
> commit: 9223d0dccb8f8523754122f68316dd1a4f39f7f8 ("thermal: Move therm_throt there from x86/mce")
> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master

Hmm, so I went and ran your reproducer, but simplified (see end of
mail), on a KBL box here. The kernel is tip:x86/urgent from last week:

5.12.0-rc6+
-----------
stress-ng: info:  [1430] dispatching hogs: 9 msg
stress-ng: info:  [1430] successful run completed in 60.01s (1 min, 0.01 secs)
stress-ng: info:  [1430] stressor       bogo ops real time  usr time  sys time   bogo ops/s   bogo ops/s
stress-ng: info:  [1430]                           (secs)    (secs)    (secs)   (real time) (usr+sys time)
stress-ng: info:  [1430] msg           237390147     60.01    104.03    255.85   3955872.56    659636.95
stress-ng: info:  [1430] for a 60.01s run time:
stress-ng: info:  [1430]     360.08s available CPU time
stress-ng: info:  [1430]     104.11s user time   ( 28.91%)
stress-ng: info:  [1430]     255.93s system time ( 71.08%)
stress-ng: info:  [1430]     360.04s total time  ( 99.99%)
stress-ng: info:  [1430] load average: 8.47 3.71 1.48

Now the same kernel with

>   4f432e8bb1 ("x86/mce: Get rid of mcheck_intel_therm_init()")
>   9223d0dccb ("thermal: Move therm_throt there from x86/mce")

reverted.

5.12.0-rc6-rev+
---------------
stress-ng: info:  [1246] dispatching hogs: 9 msg
stress-ng: info:  [1246] successful run completed in 60.02s (1 min, 0.02 secs)
stress-ng: info:  [1246] stressor       bogo ops real time  usr time  sys time   bogo ops/s   bogo ops/s
stress-ng: info:  [1246]                           (secs)    (secs)    (secs)   (real time) (usr+sys time)
stress-ng: info:  [1246] msg           215174467     60.01     99.64    260.24   3585438.79    597906.15
stress-ng: info:  [1246] for a 60.02s run time:
stress-ng: info:  [1246]     360.10s available CPU time
stress-ng: info:  [1246]      99.72s user time   ( 27.69%)
stress-ng: info:  [1246]     260.32s system time ( 72.29%)
stress-ng: info:  [1246]     360.04s total time  ( 99.98%)
stress-ng: info:  [1246] load average: 7.98 2.33 0.80

so if I'm reading this correctly, reverting the patches here brings the
*slow-down*.

What's up?

reproducer:
----------

#!/usr/bin/bash

for cpu_dir in /sys/devices/system/cpu/cpu[0-9]*
do
        online_file="$cpu_dir"/online
        [ -f "$online_file" ] && [ "$(cat "$online_file")" -eq 0 ] && continue

        file="$cpu_dir"/cpufreq/scaling_governor
        [ -f "$file" ] && echo "performance" > "$file"
done

stress-ng --timeout 60 --times --verify --metrics-brief --msg 9

-- 
Regards/Gruss,
    Boris.

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