From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail202.messagelabs.com (mail202.messagelabs.com [216.82.254.227]) by kanga.kvack.org (Postfix) with SMTP id A56E28D0039 for ; Fri, 18 Mar 2011 14:06:15 -0400 (EDT) Message-ID: <4D839EDB.9080703@fiec.espol.edu.ec> Date: Fri, 18 Mar 2011 13:05:15 -0500 From: =?ISO-8859-15?Q?Alex_Villac=ED=ADs_Lasso?= MIME-Version: 1.0 Subject: Re: [Bugme-new] [Bug 31142] New: Large write to USB stick freezes unrelated tasks for a long time References: <20110315135334.36e29414.akpm@linux-foundation.org> <4D7FEDDC.3020607@fiec.espol.edu.ec> <20110315161926.595bdb65.akpm@linux-foundation.org> <4D80D65C.5040504@fiec.espol.edu.ec> <20110316150208.7407c375.akpm@linux-foundation.org> <4D827CC1.4090807@fiec.espol.edu.ec> <20110317144727.87a461f9.akpm@linux-foundation.org> <20110318111300.GF707@csn.ul.ie> In-Reply-To: <20110318111300.GF707@csn.ul.ie> Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: Mel Gorman Cc: Andrew Morton , avillaci@ceibo.fiec.espol.edu.ec, bugzilla-daemon@bugzilla.kernel.org, Andrea Arcangeli , bugme-daemon@bugzilla.kernel.org, linux-mm@kvack.org El 18/03/11 06:13, Mel Gorman escribio: > > \o/ ... no wait, it's the other one - :( > > If you look at the stack traces though, all of them had called > do_huge_pmd_anonymous_page() so while it looks similar to 12309, the trigger > is new because it's THP triggering compaction that is causing the stalls > rather than page reclaim doing direct writeback which was the culprit in > the past. > > To confirm if this is the case, I'd be very interested in hearing if this > problem persists in the following cases > > 1. 2.6.38-rc8 with defrag disabled by > echo never>/sys/kernel/mm/transparent_hugepage/defrag > (this will stop THP allocations calling into compaction) > 2. 2.6.38-rc8 with THP disabled by > echo never> > /sys/kernel/mm/transparent_hugepage/enabled > (if the problem still persists, then page reclaim is still a problem > but we should still stop THP doing sync writes) > 3. 2.6.37 vanilla > (in case this is a new regression introduced since then) > > Migration can do sync writes on dirty pages which is why it looks so similar > to page reclaim but this can be controlled by the value of sync_migration > passed into try_to_compact_pages(). If we find that option 1 above makes > the regression go away or at least helps a lot, then a reasonable fix may > be to never set sync_migration if __GFP_NO_KSWAPD which is always set for > THP allocations. I've added Andrea to the cc to see what he thinks. > > Thanks for the report. > I have just done tests 1 and 2 on 2.6.38 (final, not -rc8), and I have verified that echoing "never" on either /sys/kernel/mm/transparent_hugepage/defrag or /sys/kernel/mm/transparent_hugepage/enabled does allow the file copy to USB to proceed smoothly (copying 4GB of data). Just to verify, I later wrote "always" to both files, and sure enough, some applications stalled when I repeated the same file copy. So I have at least a workaround for the issue. Given this evidence, will the patch at comment #14 fix the issue for good? -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org