linux-kernel - Re: [PATCH 5/5] slub: Only IPI CPUs that have per cpu obj to flush

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: <1317022565.9084.60.camel@twins>
Date:	Mon, 26 Sep 2011 09:36:05 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Pekka Enberg <penberg@...helsinki.fi>
Cc:	Gilad Ben-Yossef <gilad@...yossef.com>,
	linux-kernel@...r.kernel.org,
	Frederic Weisbecker <fweisbec@...il.com>,
	Russell King <linux@....linux.org.uk>,
	Chris Metcalf <cmetcalf@...era.com>, linux-mm@...ck.org,
	Christoph Lameter <cl@...ux-foundation.org>,
	Matt Mackall <mpm@...enic.com>
Subject: Re: [PATCH 5/5] slub: Only IPI CPUs that have per cpu obj to flush

On Mon, 2011-09-26 at 09:54 +0300, Pekka Enberg wrote:
> 
> AFAICT, flush_all() isn't all that performance sensitive. Why do we
> want to reduce IPIs here? 

Because it can wake up otherwise idle CPUs, wasting power. Or for the
case I care more about, unnecessarily perturb a CPU that didn't actually
have anything to flush but was running something, introducing jitter.

on_each_cpu() things are bad when you have a ton of CPUs (which is
pretty normal these days). 
--
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/