linux-kernel - Re: PATCH? avoid the unnecessary wakeups in pipe

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Message-ID: <CAHk-=whZHXHtpdakcLx+K-LF0=tav6r698Ph3=p3Fpuvi2D+5w@mail.gmail.com>
Date: Sun, 29 Dec 2024 09:27:21 -0800
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Oleg Nesterov <oleg@...hat.com>
Cc: Manfred Spraul <manfred@...orfullife.com>, Christian Brauner <brauner@...nel.org>, 
	David Howells <dhowells@...hat.com>, WangYuli <wangyuli@...ontech.com>, 
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: PATCH? avoid the unnecessary wakeups in pipe_read()

On Sun, 29 Dec 2024 at 05:58, Oleg Nesterov <oleg@...hat.com> wrote:
>
> If I read this code correctly, in this case the child will wakeup the parent
> 4095 times for no reason, pipe_writable() == !pipe_pull() will still be true
> until the last read(fd[0], &c, 1) does

Ack, that patch looks sane to me.

Only wake writer if we actually released a pipe slot, and it was full
before we did so.

Makes sense.

                Linus