Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965968AbbFJPs4 (ORCPT ); Wed, 10 Jun 2015 11:48:56 -0400 Received: from ip4-83-240-67-251.cust.nbox.cz ([83.240.67.251]:36139 "EHLO ip4-83-240-18-248.cust.nbox.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S933840AbbFJP1u (ORCPT ); Wed, 10 Jun 2015 11:27:50 -0400 From: Jiri Slaby To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Mel Gorman , Andrew Morton , Linus Torvalds , Jiri Slaby Subject: [PATCH 3.12 074/111] mm, numa: really disable NUMA balancing by default on single node machines Date: Wed, 10 Jun 2015 17:27:03 +0200 Message-Id: X-Mailer: git-send-email 2.4.2 In-Reply-To: <93091169a673f49c2574cddf1ef858cf0704f646.1433943052.git.jslaby@suse.cz> References: <93091169a673f49c2574cddf1ef858cf0704f646.1433943052.git.jslaby@suse.cz> In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2208 Lines: 57 From: Mel Gorman 3.12-stable review patch. If anyone has any objections, please let me know. =============== 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: Jiri Slaby --- mm/mempolicy.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/mempolicy.c b/mm/mempolicy.c index e63ade49ea24..51cd7d066e0f 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -2589,7 +2589,7 @@ static void __init check_numabalancing_enable(void) if (numabalancing_override) set_numabalancing_state(numabalancing_override == 1); - if (nr_node_ids > 1 && !numabalancing_override) { + if (num_online_nodes() > 1 && !numabalancing_override) { printk(KERN_INFO "%s automatic NUMA balancing. " "Configure with numa_balancing= or sysctl", numabalancing_default ? "Enabling" : "Disabling"); -- 2.4.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/