Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753278Ab0HWNkF (ORCPT ); Mon, 23 Aug 2010 09:40:05 -0400 Received: from gir.skynet.ie ([193.1.99.77]:50973 "EHLO gir.skynet.ie" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753093Ab0HWNkC (ORCPT ); Mon, 23 Aug 2010 09:40:02 -0400 Date: Mon, 23 Aug 2010 14:39:48 +0100 From: Mel Gorman To: Christoph Lameter Cc: Andrew Morton , Linux Kernel List , linux-mm@kvack.org, Rik van Riel , Johannes Weiner , Minchan Kim , KAMEZAWA Hiroyuki , KOSAKI Motohiro Subject: Re: [PATCH 0/3] Reduce watermark-related problems with the per-cpu allocator V2 Message-ID: <20100823133948.GR19797@csn.ul.ie> References: <1282550442-15193-1-git-send-email-mel@csn.ul.ie> <20100823130127.GP19797@csn.ul.ie> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17+20080114 (2008-01-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1432 Lines: 33 On Mon, Aug 23, 2010 at 08:38:25AM -0500, Christoph Lameter wrote: > On Mon, 23 Aug 2010, Mel Gorman wrote: > > > > The maximum time for which the livelock can exists is the vm stat > > > interval. By default the counters are brought up to date at least once per > > > second or if a certain delta was violated. Drifts are controlled by the > > > delta configuration. > > > > > > > While there is a maximum time (2 seconds I think) the drift can exist > > in, a machine under enough pressure can make a mess of the watermarks > > during that time. If it wasn't the case, these livelocks with 0 pages > > free wouldn't be happening. > > So because we go way beyond the watermarks we reach a state in which a > livelock exists that does not go away when the counters are finally > updated? > That appears to be the case. The system has already gotten into a state where there are 0 pages free. Just because the NR_FREE_PAGES counter gets updated to reflect the accurate count of 0 does not mean the system can recover from it. -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab -- 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/