From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:50931 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751739AbbFCDYg (ORCPT ); Tue, 2 Jun 2015 23:24:36 -0400 Subject: Patch "mm, numa: really disable NUMA balancing by default on single node machines" has been added to the 3.14-stable tree To: mgorman@suse.de, akpm@linux-foundation.org, gregkh@linuxfoundation.org, riel@redhat.com, torvalds@linux-foundation.org Cc: , From: Date: Wed, 03 Jun 2015 12:24:31 +0900 Message-ID: <1433301871229159@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled mm, numa: really disable NUMA balancing by default on single node machines to the 3.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: mm-numa-really-disable-numa-balancing-by-default-on-single-node-machines.patch and it can be found in the queue-3.14 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From b0dc2b9bb4ab782115b964310518ee0b17784277 Mon Sep 17 00:00:00 2001 From: Mel Gorman Date: Thu, 14 May 2015 15:17:09 -0700 Subject: mm, numa: really disable NUMA balancing by default on single node machines From: Mel Gorman commit b0dc2b9bb4ab782115b964310518ee0b17784277 upstream. 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 Reviewed-by: Rik van Riel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/mempolicy.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -2663,7 +2663,7 @@ static void __init check_numabalancing_e if (numabalancing_override) set_numabalancing_state(numabalancing_override == 1); - if (nr_node_ids > 1 && !numabalancing_override) { + if (num_online_nodes() > 1 && !numabalancing_override) { pr_info("%s automatic NUMA balancing. " "Configure with numa_balancing= or the " "kernel.numa_balancing sysctl", Patches currently in stable-queue which might be from mgorman@suse.de are queue-3.14/mm-numa-really-disable-numa-balancing-by-default-on-single-node-machines.patch