From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mel Gorman Subject: Re: [BUG] Commit d065bd81 severely regresses huge page allocation success rates Date: Thu, 11 Nov 2010 14:25:27 +0000 Message-ID: <20101111142527.GG19679@csn.ul.ie> References: <20101111121545.GF19679@csn.ul.ie> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Return-path: Received: from gir.skynet.ie ([193.1.99.77]:57312 "EHLO gir.skynet.ie" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755888Ab0KKOZl (ORCPT ); Thu, 11 Nov 2010 09:25:41 -0500 Content-Disposition: inline In-Reply-To: Sender: linux-arch-owner@vger.kernel.org List-ID: To: Michel Lespinasse Cc: Rik van Riel , Wu Fengguang , "H. Peter Anvin" , linux-arch@vger.kernel.org, Andrew Morton , linux-kernel@vger.kernel.org, Ying Han , Andrea Arcangeli On Thu, Nov 11, 2010 at 04:25:00AM -0800, Michel Lespinasse wrote: > On Thu, Nov 11, 2010 at 4:15 AM, Mel Gorman wrote: > > When testing 2.6.37-rc1, I noticed that huge page allocation success > > rates were severely impaired. Bisection showed that commit [d065bd81: mm: > > retry page fault when blocking on disk transfer] was the biggest factor. > > Reverting the patch confirmed this. Here are the results of a high-order > > allocation stress test. The vanilla kernel is 2.6.37-rc1 and the revert > > kernel has this commit removed with minor conflicts cleaned up. > [...] > > I have not digested what the patch is doing but am reporting it in case > > people familiar with the patch spot the problem quickly. > > There was a bug in that commit, which was fixed in > d88c0922fa0e2c021a028b310a641126c6d4b7dc > > I think this may explain the issue; compaction won't work well if > extra references are kept :/ > Reclaim would not work either as it is effectively a leak. > Can you check that this indeed solves your test case ? > It does. Thanks very much. -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab