From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759275AbZFIS44 (ORCPT ); Tue, 9 Jun 2009 14:56:56 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756720AbZFIS4t (ORCPT ); Tue, 9 Jun 2009 14:56:49 -0400 Received: from mx2.redhat.com ([66.187.237.31]:60184 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756650AbZFIS4t (ORCPT ); Tue, 9 Jun 2009 14:56:49 -0400 Message-ID: <4A2EB04F.2090906@redhat.com> Date: Tue, 09 Jun 2009 14:56:15 -0400 From: Rik van Riel Organization: Red Hat, Inc User-Agent: Thunderbird 2.0.0.17 (X11/20080915) MIME-Version: 1.0 To: Mel Gorman CC: KOSAKI Motohiro , Christoph Lameter , yanmin.zhang@intel.com, Wu Fengguang , linuxram@us.ibm.com, linux-mm , LKML Subject: Re: [PATCH 3/4] Count the number of times zone_reclaim() scans and fails References: <1244566904-31470-1-git-send-email-mel@csn.ul.ie> <1244566904-31470-4-git-send-email-mel@csn.ul.ie> In-Reply-To: <1244566904-31470-4-git-send-email-mel@csn.ul.ie> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Mel Gorman wrote: > On NUMA machines, the administrator can configure zone_reclaim_mode that > is a more targetted form of direct reclaim. On machines with large NUMA > distances for example, a zone_reclaim_mode defaults to 1 meaning that clean > unmapped pages will be reclaimed if the zone watermarks are not being met. > > There is a heuristic that determines if the scan is worthwhile but it is > possible that the heuristic will fail and the CPU gets tied up scanning > uselessly. Detecting the situation requires some guesswork and experimentation > so this patch adds a counter "zreclaim_failed" to /proc/vmstat. If during > high CPU utilisation this counter is increasing rapidly, then the resolution > to the problem may be to set /proc/sys/vm/zone_reclaim_mode to 0. > > Signed-off-by: Mel Gorman Reviewed-by: Rik van Riel -- All rights reversed.