From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wg0-f54.google.com (mail-wg0-f54.google.com [74.125.82.54]) by kanga.kvack.org (Postfix) with ESMTP id CD3FE6B0038 for ; Wed, 13 May 2015 09:07:59 -0400 (EDT) Received: by wgbhc8 with SMTP id hc8so9392389wgb.3 for ; Wed, 13 May 2015 06:07:59 -0700 (PDT) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id kf4si8414072wic.48.2015.05.13.06.07.57 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 13 May 2015 06:07:58 -0700 (PDT) Message-ID: <55534CA2.7030105@redhat.com> Date: Wed, 13 May 2015 09:07:46 -0400 From: Rik van Riel MIME-Version: 1.0 Subject: Re: [PATCH] mm, numa: Really disable NUMA balancing by default on single node machines References: <20150513081053.GQ2462@suse.de> In-Reply-To: <20150513081053.GQ2462@suse.de> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Mel Gorman , Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org On 05/13/2015 04:10 AM, Mel Gorman wrote: > NUMA balancing is meant to be disabled by default on UMA machines but > the check is using nr_node_ids (highest node) instead of num_online_nodes > (online nodes). The consequences are that a UMA machine with a node ID of 1 > or higher will enable NUMA balancing. This will incur useless overhead due > to minor faults with the impact depending on the workload. These are the > impact on the stats when running a kernel build on a single node machine > whose node ID happened to be 1; > > vanilla patched > NUMA base PTE updates 5113158 0 > NUMA huge PMD updates 643 0 > NUMA page range updates 5442374 0 > NUMA hint faults 2109622 0 > NUMA hint local faults 2109622 0 > NUMA hint local percent 100 100 > NUMA pages migrated 0 0 > > Signed-off-by: Mel Gorman > Cc: #v3.8+ Reviewed-by: Rik van Riel -- All rights reversed -- 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