linux-kernel - Re: [PATCH] do_wait wakeup optimization

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: <alpine.LFD.2.00.0811191929450.21698@nehalem.linux-foundation.org>
Date:	Wed, 19 Nov 2008 19:35:45 -0800 (PST)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Roland McGrath <roland@...hat.com>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Ratan Nalumasu <rnalumasu@...il.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] do_wait wakeup optimization



On Wed, 19 Nov 2008, Roland McGrath wrote:
>
> Ratan Nalumasu reported that in a process with many threads doing
> different, mutually-exclusive waitpid() calls, there were a lot of
> unnecessary wakeups.  Every waiting thread in the process wakes up to
> loop through the children and see that the only ones it cares about
> are still not ready.

Patch looks sane, and look worth queueing up for the next merge window. 
But if somebody actually has numbers and/or can talk about the real-life 
load that made people even notice this, that would be good to add to the 
description.

Also, do we really need to call eligible_child() twice? The real wait only 
does it once in that "wait_consider_task()". Explanations would be good..

			Linus
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/