From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx179.postini.com [74.125.245.179]) by kanga.kvack.org (Postfix) with SMTP id 549606B005A for ; Fri, 29 Jun 2012 18:50:34 -0400 (EDT) Received: by dakp5 with SMTP id p5so6084081dak.14 for ; Fri, 29 Jun 2012 15:50:33 -0700 (PDT) Date: Fri, 29 Jun 2012 15:50:31 -0700 (PDT) From: David Rientjes 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> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: 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 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, 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/ . Don't email: email@kvack.org