Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755460AbZKCWIJ (ORCPT ); Tue, 3 Nov 2009 17:08:09 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755348AbZKCWII (ORCPT ); Tue, 3 Nov 2009 17:08:08 -0500 Received: from gir.skynet.ie ([193.1.99.77]:56958 "EHLO gir.skynet.ie" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755063AbZKCWIH (ORCPT ); Tue, 3 Nov 2009 17:08:07 -0500 Date: Tue, 3 Nov 2009 22:08:09 +0000 From: Mel Gorman To: Frans Pop Cc: Andrew Morton , stable@kernel.org, linux-kernel@vger.kernel.org, "linux-mm@kvack.org" , Jiri Kosina , Sven Geggus , Karol Lewandowski , Tobias Oetiker , KOSAKI Motohiro , Pekka Enberg , Rik van Riel , Christoph Lameter , Stephan von Krawczynski , Kernel Testers List Subject: Re: [PATCH 3/3] vmscan: Force kswapd to take notice faster when high-order watermarks are being hit Message-ID: <20091103220808.GF22046@csn.ul.ie> References: <1256650833-15516-1-git-send-email-mel@csn.ul.ie> <200911021832.59035.elendil@planet.nl> <20091102173837.GB22046@csn.ul.ie> <200911032301.59662.elendil@planet.nl> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <200911032301.59662.elendil@planet.nl> 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: 2371 Lines: 48 On Tue, Nov 03, 2009 at 11:01:50PM +0100, Frans Pop wrote: > On Monday 02 November 2009, Mel Gorman wrote: > > On Mon, Nov 02, 2009 at 06:32:54PM +0100, Frans Pop wrote: > > > On Monday 02 November 2009, Mel Gorman wrote: > > > > vmscan: Help debug kswapd issues by counting number of rewakeups and > > > > premature sleeps > > > > > > > > There is a growing amount of anedotal evidence that high-order > > > > atomic allocation failures have been increasing since 2.6.31-rc1. > > > > The two strongest possibilities are a marked increase in the number > > > > of GFP_ATOMIC allocations and alterations in timing. Debugging > > > > printk patches have shown for example that kswapd is sleeping for > > > > shorter intervals and going to sleep when watermarks are still not > > > > being met. > > > > > > > > This patch adds two kswapd counters to help identify if timing is an > > > > issue. The first counter kswapd_highorder_rewakeup counts the number > > > > of times that kswapd stops reclaiming at one order and restarts at a > > > > higher order. The second counter kswapd_slept_prematurely counts the > > > > number of times kswapd went to sleep when the high watermark was not > > > > met. > > > > > > What testing would you like done with this patch? > > > > Same reproduction as before except post what the contents of > > /proc/vmstat were after the problem was triggered. > > With a representative test I get 0 for kswapd_slept_prematurely. > Tested with .32-rc6 + patches 1-3 + this patch. > Assuming the problem actually reproduced, can you still retest with the patch I posted as a follow-up and see if fast or slow premature sleeps are happening and if the problem still occurs please? It's still possible with the patch as-is could be timing related. After I posted this patch, I continued testing and found I could get counts fairly reliably if kswapd was calling printk() before making the premature check so the window appears to be very small. -- 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/