From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f177.google.com (mail-wi0-f177.google.com [209.85.212.177]) by kanga.kvack.org (Postfix) with ESMTP id 98BAB82BEF for ; Sun, 9 Nov 2014 04:43:03 -0500 (EST) Received: by mail-wi0-f177.google.com with SMTP id ex7so7960347wid.10 for ; Sun, 09 Nov 2014 01:43:03 -0800 (PST) Received: from mx2.suse.de (cantor2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id fv10si1155131wib.88.2014.11.09.01.43.02 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Sun, 09 Nov 2014 01:43:02 -0800 (PST) Message-ID: <545F3724.7070502@suse.cz> Date: Sun, 09 Nov 2014 10:43:00 +0100 From: Vlastimil Babka MIME-Version: 1.0 Subject: Re: Early test: hangs in mm/compact.c w. Linus's 12d7aacab56e9ef185c References: <12996532.NCRhVKzS9J@xorhgos3.pefnos> <3583067.00bS4AInhm@xorhgos3.pefnos> <545BEA3B.40005@suse.cz> <3443150.6EQzxj6Rt9@xorhgos3.pefnos> <545E96BD.5040103@suse.cz> <20141109082746.GA3402@amd> In-Reply-To: <20141109082746.GA3402@amd> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Pavel Machek Cc: "P. Christeas" , linux-mm@kvack.org, Joonsoo Kim , lkml , David Rientjes , Norbert Preining , Markus Trippelsdorf On 11/09/2014 09:27 AM, Pavel Machek wrote: > Hi! > >>>> Oh and did I ask in this thread for /proc/zoneinfo yet? :) >>> >>> Using that same kernel[1], got again into a race, gathered a few more data. >>> >>> This time, I had 1x "urpmq" process [2] hung at 100% CPU , when "kwin" got >>> apparently blocked (100% CPU, too) trying to resize a GUI window. I suppose >>> the resizing operation would mean heavy memory alloc/free. >>> >>> The rest of the system was responsive, I could easily get a console, login, >>> gather the files.. Then, I have *killed* -9 the "urpmq" process, which solved >>> the race and my system is still alive! "kwin" is still running, returned to >>> regular CPU load. >>> >>> Attached is traces from SysRq+l (pressed a few times, wanted to "snapshot" the >>> stack) and /proc/zoneinfo + /proc/vmstat >>> >>> Bisection is not yet meaningful, IMHO, because I cannot be sure that "good" >>> points are really free from this issue. I'd estimate that each test would take >>> +3days, unless I really find a deterministic way to reproduce the issue . >> >> Hi, >> >> I think I finally found the cause by staring into the code... CCing >> people from all 4 separate threads I know about this issue. >> The problem with finding the cause was that the first report I got from >> Markus was about isolate_freepages_block() overhead, and later Norbert >> reported that reverting a patch for isolate_freepages* helped. But the >> problem seems to be that although the loop in isolate_migratepages exits >> because the scanners almost meet (they are within same pageblock), they >> don't truly meet, therefore compact_finished() decides to continue, but >> isolate_migratepages() exits immediately... boom! But indeed e14c720efdd7 >> made this situation possible, as free scaner pfn can now point to a >> middle of pageblock. > > Ok, it seems it happened second time now, again shortly after > resume. I guess I should apply your patch after all. Thanks. > (Or... instead it should go to Linus ASAP -- it fixes known problem > that is affected people, and we want it in soon in case it is not > complete fix.) I don't want to send untested fix, and wasn't able to reproduce the bug myself. I think Norbert could do it rather quickly so I hope he can tell us soon. > Dmesg is in the attachment, perhaps it helps. > Pavel It looks the same as before, so no surprises there, which is 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/ . Don't email: email@kvack.org