linux-kernel - Re: [pipe] 3c0edea9b2: lmbench3.PIPE.bandwidth.MB/sec -17.0% regression

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Date:   Tue, 10 Dec 2019 22:15:02 +0800
From:   kernel test robot <rong.a.chen@...el.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Michal Hocko <mhocko@...nel.org>,
        David Howells <dhowells@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>, lkp@...ts.01.org
Subject: Re: [pipe] 3c0edea9b2: lmbench3.PIPE.bandwidth.MB/sec -17.0%
 regression

On Mon, Dec 09, 2019 at 10:35:35AM -0800, Linus Torvalds wrote:
> On Mon, Dec 9, 2019 at 12:56 AM Michal Hocko <mhocko@...nel.org> wrote:
> >
> > Huh. How can something like that can even can get merged? No changelog,
> > no s-o-b?
> 
> Yeah, I missed that when pulling.
> 
> I wish that had been the only problem we had with that code, but it wasn't.
> 
> Anyway, I'm fairly certain the current git head should fix this
> lmbench3 performance regression too.
> 
>                    Linus

Hi Linus,

Sorry for the inconvenience, indeed, the regression has been fixed.

commit:
  cefa80ced5 ("pipe: Increase the writer-wakeup threshold to reduce context-switch count")
  3c0edea9b2 ("pipe: Remove sync on wake_ups")
  6794862a16 ("Merge tag 'for-5.5-rc1-kconfig-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux")

cefa80ced57a2917  3c0edea9b29f9be6c093f236f7  6794862a16ef41f753abd75c03  testcase/testparams/testbox
----------------  --------------------------  --------------------------  ---------------------------
         %stddev      change         %stddev      change         %stddev
             \          |                \          |                \  
     21204             -17%      17604              23%      26123 ±  3%  lmbench3/performance-development-100%-PIPE-50%-ucode=0x7000019/lkp-bdw-de1
     21204             -17%      17604              23%      26123        GEO-MEAN lmbench3.PIPE.bandwidth.MB/sec

Best Regards,
Rong Chen