From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with SMTP id 80A358D0039 for ; Sat, 19 Mar 2011 12:05:03 -0400 (EDT) Message-ID: <4D84D3F2.4010200@fiec.espol.edu.ec> Date: Sat, 19 Mar 2011 11:04:02 -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> <4D839EDB.9080703@fiec.espol.edu.ec> <20110319134628.GG707@csn.ul.ie> In-Reply-To: <20110319134628.GG707@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 19/03/11 08:46, Mel Gorman escribio: > On Fri, Mar 18, 2011 at 01:05:15PM -0500, Alex Villac??s Lasso wrote: >> 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? >> > Thanks for testing and reporting, it's very helpful. Based on that that > report the patch should help. Can you test it to be absolutly sure please? > > The patch did not help. I have attached a sysrq-w trace with the patch applied in the bug report. -- 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