From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1422924AbXDRMIH (ORCPT ); Wed, 18 Apr 2007 08:08:07 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1422925AbXDRMIH (ORCPT ); Wed, 18 Apr 2007 08:08:07 -0400 Received: from smtp24.orange.fr ([193.252.22.25]:27035 "EHLO smtp24.orange.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1422924AbXDRMIF (ORCPT ); Wed, 18 Apr 2007 08:08:05 -0400 X-ME-UUID: 20070418120803246.3C46C1C0008B@mwinf2433.orange.fr Date: Wed, 18 Apr 2007 14:07:52 +0200 From: Eric Dumazet To: Pekka J Enberg Cc: Pavel Emelianov , Andrew Morton , Linux Kernel Mailing List , devel@openvz.org, Kirill Korotaev , linux-mm@kvack.org Subject: Re: [PATCH] Show slab memory usage on OOM and SysRq-M Message-Id: <20070418140752.02084f34.dada1@cosmosbay.com> In-Reply-To: References: <4624C3C1.9040709@sw.ru> <84144f020704170622h2b16f0f6m47ffdbb3b5686758@mail.gmail.com> <20070417171213.e3cbc260.dada1@cosmosbay.com> X-Mailer: Sylpheed 2.3.1 (GTK+ 2.10.11; 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, 18 Apr 2007 09:17:19 +0300 (EEST) Pekka J Enberg wrote: > On Tue, 17 Apr 2007, Eric Dumazet wrote: > > This nr_pages should be in struct kmem_list3, not in struct kmem_cache, > > or else you defeat NUMA optimizations if touching a field in kmem_cache > > at kmem_getpages()/kmem_freepages() time. > > We already touch ->flags, ->gfpflags, and ->gfporder in kmem_getpages(). > Sorry for my ignorance, but how is this different? > Those fields are read. Thats OK, because several CPUS might share all those without problem. But modifying one field in kmem_cache would invalidate one cache line for all cpus that would have to reload it later. This is what we call "false sharing" or cache line ping pongs