From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail137.messagelabs.com (mail137.messagelabs.com [216.82.249.19]) by kanga.kvack.org (Postfix) with ESMTP id 836319000BD for ; Mon, 26 Sep 2011 03:36:45 -0400 (EDT) Subject: Re: [PATCH 5/5] slub: Only IPI CPUs that have per cpu obj to flush From: Peter Zijlstra Date: Mon, 26 Sep 2011 09:36:05 +0200 In-Reply-To: References: <1316940890-24138-1-git-send-email-gilad@benyossef.com> <1316940890-24138-6-git-send-email-gilad@benyossef.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Message-ID: <1317022565.9084.60.camel@twins> Mime-Version: 1.0 Sender: owner-linux-mm@kvack.org List-ID: To: Pekka Enberg Cc: Gilad Ben-Yossef , linux-kernel@vger.kernel.org, Frederic Weisbecker , Russell King , Chris Metcalf , linux-mm@kvack.org, Christoph Lameter , Matt Mackall On Mon, 2011-09-26 at 09:54 +0300, Pekka Enberg wrote: >=20 > AFAICT, flush_all() isn't all that performance sensitive. Why do we > want to reduce IPIs here?=20 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).=20 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org