From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx190.postini.com [74.125.245.190]) by kanga.kvack.org (Postfix) with SMTP id E3A116B0073 for ; Mon, 9 Jan 2012 12:57:51 -0500 (EST) Message-ID: <4F0B2A9D.5020208@tilera.com> Date: Mon, 9 Jan 2012 12:57:49 -0500 From: Chris Metcalf MIME-Version: 1.0 Subject: Re: [PATCH v6 0/8] Reduce cross CPU IPI interference References: <1326040026-7285-1-git-send-email-gilad@benyossef.com> In-Reply-To: <1326040026-7285-1-git-send-email-gilad@benyossef.com> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Gilad Ben-Yossef Cc: linux-kernel@vger.kernel.org, Christoph Lameter , Peter Zijlstra , Frederic Weisbecker , linux-mm@kvack.org, Pekka Enberg , Matt Mackall , Sasha Levin , Rik van Riel , Andi Kleen , Mel Gorman , Andrew Morton , Alexander Viro , Avi Kivity , Michal Nazarewicz , Kosaki Motohiro On 1/8/2012 11:26 AM, Gilad Ben-Yossef wrote: > We have lots of infrastructure in place to partition a multi-core systems > such that we have a group of CPUs that are dedicated to specific task: > cgroups, scheduler and interrupt affinity and cpuisol boot parameter. > Still, kernel code will some time interrupt all CPUs in the system via IPIs > for various needs. These IPIs are useful and cannot be avoided altogether, > but in certain cases it is possible to interrupt only specific CPUs that > have useful work to do and not the entire system. > > This patch set, inspired by discussions with Peter Zijlstra and Frederic > Weisbecker when testing the nohz task patch set, is a first stab at trying > to explore doing this by locating the places where such global IPI calls > are being made and turning a global IPI into an IPI for a specific group > of CPUs. The purpose of the patch set is to get feedback if this is the > right way to go for dealing with this issue and indeed, if the issue is > even worth dealing with at all. Based on the feedback from this patch set > I plan to offer further patches that address similar issue in other code > paths. > > The patch creates an on_each_cpu_mask and on_each_cpu_conf infrastructure > API (the former derived from existing arch specific versions in Tile and > Arm) and and uses them to turn several global IPI invocation to per CPU > group invocations. Acked-by: Chris Metcalf (To be fair, mostly this acks the proposed infrastructure, and moving the functions out of the tile architecture and into the generic code; I not expert enough at slub or the invalidate_bh_lrus path to ack those changes, other than to say I like how they look.) -- Chris Metcalf, Tilera Corp. http://www.tilera.com -- 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