From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx124.postini.com [74.125.245.124]) by kanga.kvack.org (Postfix) with SMTP id AA8A86B009B for ; Sat, 30 Jun 2012 05:43:30 -0400 (EDT) Received: by wibhr14 with SMTP id hr14so1251771wib.7 for ; Sat, 30 Jun 2012 02:43:28 -0700 (PDT) Message-ID: <4FEECA3C.5070308@ravellosystems.com> Date: Sat, 30 Jun 2012 12:43:24 +0300 From: Izik Eidus MIME-Version: 1.0 Subject: Re: [PATCH v2] KSM: numa awareness sysfs knob References: <1340970592-25001-1-git-send-email-pholasek@redhat.com> <20120629141759.3312b49e.akpm@linux-foundation.org> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: David Rientjes Cc: Andrew Morton , Petr Holasek , Hugh Dickins , Andrea Arcangeli , Chris Wright , Rik van Riel , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Anton Arapov On 06/30/2012 01:50 AM, David Rientjes wrote: > 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. While you are right for case you write your own custom application, but I think the KVM guest case is little bit more problomatic in case the guest memory must be splitted across serval nodes. -- 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