linux-kernel - Re: [PATCH] pipe_read: don't wake up the writer if the pipe is still full

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAHk-=wioaHG2P0KH=1zP0Zy=CcQb_JxZrksSS2+-FwcptHtntw@mail.gmail.com>
Date: Fri, 31 Jan 2025 12:06:44 -0800
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: K Prateek Nayak <kprateek.nayak@....com>
Cc: Oleg Nesterov <oleg@...hat.com>, 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, "Gautham R. Shenoy" <gautham.shenoy@....com>, 
	Swapnil Sapkal <swapnil.sapkal@....com>, Neeraj Upadhyay <Neeraj.Upadhyay@....com>
Subject: Re: [PATCH] pipe_read: don't wake up the writer if the pipe is still full

On Fri, 31 Jan 2025 at 01:50, K Prateek Nayak <kprateek.nayak@....com> wrote:
>
> On my 3rd Generation EPYC system (2 x 64C/128T), I see that on reverting
> the changes on the above mentioned commit, sched-messaging sees a
> regression up until the 8 group case which contains 320 tasks, however
> with 16 groups (640 tasks), the revert helps with performance.

I suspect that the extra wakeups just end up perturbing timing, and
then you just randomly get better performance on that particular
test-case and machine.

I'm not sure this is worth worrying about, unless there's a real load
somewhere that shows this regression.

            Linus