linux-kernel - Re: [pipe] 566d136289: stress-ng.tee.ops_per

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Message-ID: <0cc7fed8-faaf-459a-8b78-a9f66b556c1d@i-love.sakura.ne.jp>
Date:   Thu, 18 Jun 2020 14:17:52 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
To:     kernel test robot <rong.a.chen@...el.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>, lkp@...ts.01.org
Subject: Re: [pipe] 566d136289: stress-ng.tee.ops_per_sec -84.7% regression

On 2020/06/18 9:51, kernel test robot wrote:
> FYI, we noticed a -84.7% regression of stress-ng.tee.ops_per_sec due to commit:
> 
> 
> commit: 566d136289dc57816ac290de87a9a0f7d9bd3cbb ("pipe: Fix pipe_full() test in opipe_prep().")
> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master

This would be because the test case shows higher performance if the pipe writer does busy wait.
This commit fixed an unkillable busy wait bug when the pipe reader does not try to read.

> If you fix the issue, kindly add following tag
> Reported-by: kernel test robot <rong.a.chen@...el.com>

We can't fix the issue. ;-)