From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail137.messagelabs.com (mail137.messagelabs.com [216.82.249.19]) by kanga.kvack.org (Postfix) with SMTP id BE8EB6B004F for ; Tue, 9 Jun 2009 14:08:25 -0400 (EDT) Message-ID: <4A2EB04F.2090906@redhat.com> Date: Tue, 09 Jun 2009 14:56:15 -0400 From: Rik van Riel MIME-Version: 1.0 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: owner-linux-mm@kvack.org To: Mel Gorman Cc: KOSAKI Motohiro , Christoph Lameter , yanmin.zhang@intel.com, Wu Fengguang , linuxram@us.ibm.com, linux-mm , LKML List-ID: 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. -- 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