Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751591AbWBWQQE (ORCPT ); Thu, 23 Feb 2006 11:16:04 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751598AbWBWQQE (ORCPT ); Thu, 23 Feb 2006 11:16:04 -0500 Received: from amdext4.amd.com ([163.181.251.6]:27277 "EHLO amdext4.amd.com") by vger.kernel.org with ESMTP id S1751591AbWBWQQC (ORCPT ); Thu, 23 Feb 2006 11:16:02 -0500 X-Server-Uuid: 5FC0E2DF-CD44-48CD-883A-0ED95B391E89 From: "Ray Bryant" To: "Arjan van de Ven" Subject: Re: [Patch 1/3] prefetch the mmap_sem in the fault path Date: Wed, 22 Feb 2006 22:15:41 -0600 User-Agent: KMail/1.8 cc: "Jes Sorensen" , ak@suse.de, akpm@osdl.org, linux-kernel@vger.kernel.org References: <1140686152.2972.25.camel@laptopd505.fenrus.org> <1140698357.4672.46.camel@laptopd505.fenrus.org> In-Reply-To: <1140698357.4672.46.camel@laptopd505.fenrus.org> MIME-Version: 1.0 Message-ID: <200602222215.42412.raybry@mpdtxmail.amd.com> X-OriginalArrivalTime: 23 Feb 2006 16:15:37.0544 (UTC) FILETIME=[61E65C80:01C63894] X-WSS-ID: 6FE300231VK1964961-01-01 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1793 Lines: 40 On Thursday 23 February 2006 06:39, Arjan van de Ven wrote: > On Thu, 2006-02-23 at 07:29 -0500, Jes Sorensen wrote: > > >>>>> "Arjan" == Arjan van de Ven writes: > > > > Arjan> In a micro-benchmark that stresses the pagefault path, the > > Arjan> down_read_trylock on the mmap_sem showed up quite high on the > > Arjan> profile. Turns out this lock is bouncing between cpus quite a > > Arjan> bit and thus is cache-cold a lot. This patch prefetches the > > Arjan> lock (for write) as early as possible (and before some other > > Arjan> somewhat expensive operations). With this patch, the > > Arjan> down_read_trylock basically fell out of the top of profile. > > > > Out of curiousity, how big was the box used for testing? It might be > > worth investigating if anything can be done to reduce the number of > > times that lock is taken in the first place. > > > > After all, what's a pain on a 4-way tends to be an utter nightmare on > > a 16-way ;( > > most of it was done on a 2 way, but some tests were done on a 4-way. > - > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ Could you share your microbenchmark with us (or point to the source) and we can give this a try on larger systems? Thanks, -- Ray Bryant AMD Performance Labs Austin, Tx 512-602-0038 (o) 512-507-7807 (c) - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/