From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759803AbXEIXjS (ORCPT ); Wed, 9 May 2007 19:39:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756894AbXEIXjJ (ORCPT ); Wed, 9 May 2007 19:39:09 -0400 Received: from smtp1.linux-foundation.org ([65.172.181.25]:49285 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751473AbXEIXjG (ORCPT ); Wed, 9 May 2007 19:39:06 -0400 Date: Wed, 9 May 2007 16:36:16 -0700 From: Andrew Morton To: "Yu, Fenghua" Cc: "Christoph Lameter" , "Siddha, Suresh B" , Subject: Re: [PATCH 2/2] Call percpu smp cacheline algin interface Message-Id: <20070509163616.e8a36a4c.akpm@linux-foundation.org> In-Reply-To: References: X-Mailer: Sylpheed version 2.2.7 (GTK+ 2.8.6; i686-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 9 May 2007 16:10:05 -0700 "Yu, Fenghua" wrote: > > > On Wed, 9 May 2007, Andrew Morton wrote: > > >> erm, it's not obviosu from all this that the patches are worth > proceeding > >> with, are they? > > >What was it? 0.5% performance improvement on a synthetic benchmark? > >Process wakeup I believe? > > The initial patch and discussion is from: > http://www.uwsg.iu.edu/hypermail/linux/kernel/0704.1/0340.html > > Yes, the runqueue patch has a 0.5% perf improvement on database > workload(which is a good improvement for this workload). > > The theory behind the patches is: > > 1. Minimize number of cache lines that are touched during a remote > access. On Numa system, remote access is more expensive than local. > 2. Do not share cache line between remote accessed data and local > accessed data. Local data update may cause remote access cache miss and > wait for longer time. > > Although the patches themselves don't save or waste per_cpu size, the > above two reasons are good to have them in. > Guys, this is all a lesson in the value of changelogs, and in how not to write them. Can you please prepare a new changelog for these patches? Something which encapsulates all the above in as brief a form as possible and which includes some numbers describing the space and/or speed improvements? Thanks.