linux-kernel - Re: Performance regression introduced by commit b667b8673443 ("pipe: Advance tail pointer inside of wait spinlock in pipe

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Message-ID: <CAHk-=wiOwghtCi8kpdefmLbyG0oSH23vYrMOU8v_XKEe7va-4g@mail.gmail.com>
Date:   Fri, 17 Jan 2020 11:20:17 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Waiman Long <longman@...hat.com>
Cc:     David Howells <dhowells@...hat.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>
Subject: Re: Performance regression introduced by commit b667b8673443 ("pipe:
 Advance tail pointer inside of wait spinlock in pipe_read()")

On Fri, Jan 17, 2020 at 10:11 AM Waiman Long <longman@...hat.com> wrote:
>
> I built a make with the lastest make git tree and the problem was gone
> with the new make. So it was a bug in make not the kernel. Sorry for the
> noise.

I think I spent about three days trying to figure it out. At least it
felt that way. I looked at the pipe code a _lot_, also blaming the
kernel for obvious reasons.

             Linus