Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754047Ab2F2Wuf (ORCPT ); Fri, 29 Jun 2012 18:50:35 -0400 Received: from mail-pb0-f46.google.com ([209.85.160.46]:45554 "EHLO mail-pb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752363Ab2F2Wud (ORCPT ); Fri, 29 Jun 2012 18:50:33 -0400 Date: Fri, 29 Jun 2012 15:50:31 -0700 (PDT) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: Andrew Morton cc: Petr Holasek , Hugh Dickins , Andrea Arcangeli , Chris Wright , Izik Eidus , Rik van Riel , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Anton Arapov Subject: Re: [PATCH v2] KSM: numa awareness sysfs knob In-Reply-To: <20120629141759.3312b49e.akpm@linux-foundation.org> Message-ID: References: <1340970592-25001-1-git-send-email-pholasek@redhat.com> <20120629141759.3312b49e.akpm@linux-foundation.org> User-Agent: Alpine 2.00 (DEB 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1182 Lines: 35 On Fri, 29 Jun 2012, Andrew Morton wrote: > > I've tested this patch on numa machines with 2, 4 and 8 nodes and > > measured speed of memory access inside of KVM guests with memory pinned > > to one of nodes with this benchmark: > > > > http://pholasek.fedorapeople.org/alloc_pg.c > > > > Population standard deviations of access times in percentage of average > > were following: > > > > merge_nodes=1 > > 2 nodes 1.4% > > 4 nodes 1.6% > > 8 nodes 1.7% > > > > merge_nodes=0 > > 2 nodes 1% > > 4 nodes 0.32% > > 8 nodes 0.018% > > ooh, numbers! Thanks. > Ok, the standard deviation increases when merging pages from nodes with remote distance, that makes sense. But if that's true, then you would restrict either the entire application to local memory with mempolicies or cpusets, or you would use mbind() to restrict this memory to that set of nodes already so that accesses, even with ksm merging, would have affinity. -- 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/