linux-kernel - Re: [LKP] [lkp-robot] [sched/fair] d519329f72: unixbench.score -9.9% regression

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Date:   Wed, 24 Oct 2018 14:41:00 +0800
From:   Aaron Lu <aaron.lu@...el.com>
To:     Patrick Bellasi <patrick.bellasi@....com>
Cc:     "Ye, Xiaolong" <xiaolong.ye@...el.com>,
        Joel Fernandes <joelaf@...gle.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Todd Kjos <tkjos@...roid.com>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Peter Zijlstra <peterz@...radead.org>,
        Paul Turner <pjt@...gle.com>,
        "Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steve Muckle <smuckle@...gle.com>, "lkp@...org" <lkp@...org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Chris Redpath <chris.redpath@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Ingo Molnar <mingo@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [LKP] [lkp-robot] [sched/fair] d519329f72: unixbench.score -9.9%
 regression

On Mon, Apr 02, 2018 at 11:20:00AM +0800, Ye, Xiaolong wrote:
> 
> Greeting,
> 
> FYI, we noticed a -9.9% regression of unixbench.score due to commit:
> 
> 
> commit: d519329f72a6f36bc4f2b85452640cfe583b4f81 ("sched/fair: Update util_est only on util_avg updates")
> https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git master
> 
> in testcase: unixbench
> on test machine: 8 threads Intel(R) Core(TM) i7 CPU 870 @ 2.93GHz with 6G memory
> with following parameters:
> 
>         runtime: 300s
>         nr_task: 100%
>         test: execl
> 
> test-description: UnixBench is the original BYTE UNIX benchmark suite aims to test performance of Unix-like system.
> test-url: https://github.com/kdlucas/byte-unixbench

I tested this workload on different machines with this commit
d519329f72a6f36bc4f2b85452 and its parent a07630b8b2c16f82, I also
tested with v4.19-rc8 to see if the regression is gone -
the performance drop is there with v4.19-rc8 and with different
machines so I assume this regression is not solved yet.
Here are detailed data:

cmdline used to run this workload:
./Run execl -c $nr_cpu -i 30

lkp-ivb-d04(Ivybridge desktop, 4 CPUs)
a07630b8b2c16f82 d519329f72a6f36bc4f2b85452
---------------- --------------------------
         %stddev     %change         %stddev
             \          |                \
      2924            -8.7%       2669        unixbench.score
 
a07630b8b2c16f82fd5b71d890079f4dd7599c1d/avg.json:  "unixbench.score": 2924.3333333333335,
d519329f72a6f36bc4f2b85452640cfe583b4f81/avg.json:  "unixbench.score": 2669.5333333333333,
v4.19-rc8/avg.json:  "unixbench.score": 2611.733333333333,

lkp-hsw-d01(Haswell desktop, 8 CPUs)
a07630b8b2c16f82 d519329f72a6f36bc4f2b85452
---------------- --------------------------
         %stddev     %change         %stddev
             \          |                \
      7090            -9.4%       6421        unixbench.score
 
a07630b8b2c16f82fd5b71d890079f4dd7599c1d/avg.json:  "unixbench.score": 7090.400000000001,
d519329f72a6f36bc4f2b85452640cfe583b4f81/avg.json:  "unixbench.score": 6421.233333333333,
v4.19-rc8/avg.json:  "unixbench.score": 6431.933333333333,

lkp-skl-2sp2(2 sockets Skylake, 80 CPUs)
a07630b8b2c16f82 d519329f72a6f36bc4f2b85452
---------------- --------------------------                                                                                                           
         %stddev     %change         %stddev                                                                                                          
             \          |                \                                                                                                            
      9657 ±  2%      -3.3%       9334        unixbench.score
      
a07630b8b2c16f82fd5b71d890079f4dd7599c1d/avg.json:  "unixbench.score": 9657.6,
d519329f72a6f36bc4f2b85452640cfe583b4f81/avg.json:  "unixbench.score": 9334.9,
v4.19-rc8/avg.json:  "unixbench.score": 9278.333333333334,

Please let me know if you need other information, thanks.