From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-we0-f170.google.com (mail-we0-f170.google.com [74.125.82.170]) by kanga.kvack.org (Postfix) with ESMTP id 4F0046B0035 for ; Mon, 28 Jul 2014 04:42:12 -0400 (EDT) Received: by mail-we0-f170.google.com with SMTP id w62so6949340wes.29 for ; Mon, 28 Jul 2014 01:42:09 -0700 (PDT) Received: from mx2.suse.de (cantor2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id vl8si32705148wjc.152.2014.07.28.01.42.07 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Mon, 28 Jul 2014 01:42:08 -0700 (PDT) Message-ID: <53D60CDD.4080801@suse.cz> Date: Mon, 28 Jul 2014 10:42:05 +0200 From: Vlastimil Babka MIME-Version: 1.0 Subject: Re: [patch v3] mm, thp: only collapse hugepages to nodes with affinity for zone_reclaim_mode References: <53C69C7B.1010709@suse.cz> 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 , Andrew Morton Cc: Andrea Arcangeli , Mel Gorman , Rik van Riel , "Kirill A. Shutemov" , Bob Liu , linux-mm@kvack.org, linux-kernel@vger.kernel.org On 07/17/2014 02:59 AM, David Rientjes wrote: > Commit 9f1b868a13ac ("mm: thp: khugepaged: add policy for finding target > node") improved the previous khugepaged logic which allocated a > transparent hugepages from the node of the first page being collapsed. > > However, it is still possible to collapse pages to remote memory which may > suffer from additional access latency. With the current policy, it is > possible that 255 pages (with PAGE_SHIFT == 12) will be collapsed remotely > if the majority are allocated from that node. > > When zone_reclaim_mode is enabled, it means the VM should make every attempt > to allocate locally to prevent NUMA performance degradation. In this case, > we do not want to collapse hugepages to remote nodes that would suffer from > increased access latency. Thus, when zone_reclaim_mode is enabled, only > allow collapsing to nodes with RECLAIM_DISTANCE or less. > > There is no functional change for systems that disable zone_reclaim_mode. > > Signed-off-by: David Rientjes Acked-by: Vlastimil Babka -- 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