Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753273Ab1CEQmP (ORCPT ); Sat, 5 Mar 2011 11:42:15 -0500 Received: from mailhub.sw.ru ([195.214.232.25]:18119 "EHLO relay.sw.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752213Ab1CEQmO (ORCPT ); Sat, 5 Mar 2011 11:42:14 -0500 Message-ID: <4D7267B6.6020406@gmail.com> Date: Sat, 05 Mar 2011 19:41:26 +0300 From: Andrew Vagin Reply-To: avagin@gmail.com User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.13) Gecko/20101209 Fedora/3.1.7-0.35.b3pre.fc13 Thunderbird/3.1.7 MIME-Version: 1.0 To: Minchan Kim CC: Andrey Vagin , Andrew Morton , Mel Gorman , KOSAKI Motohiro , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: check zone->all_unreclaimable in all_unreclaimable() References: <1299325456-2687-1-git-send-email-avagin@openvz.org> <20110305152056.GA1918@barrios-desktop> <4D72580D.4000208@gmail.com> <20110305155316.GB1918@barrios-desktop> In-Reply-To: <20110305155316.GB1918@barrios-desktop> Content-Type: text/plain; charset=KOI8-R; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4112 Lines: 124 On 03/05/2011 06:53 PM, Minchan Kim wrote: > On Sat, Mar 05, 2011 at 06:34:37PM +0300, Andrew Vagin wrote: >> On 03/05/2011 06:20 PM, Minchan Kim wrote: >>> On Sat, Mar 05, 2011 at 02:44:16PM +0300, Andrey Vagin wrote: >>>> Check zone->all_unreclaimable in all_unreclaimable(), otherwise the >>>> kernel may hang up, because shrink_zones() will do nothing, but >>>> all_unreclaimable() will say, that zone has reclaimable pages. >>>> >>>> do_try_to_free_pages() >>>> shrink_zones() >>>> for_each_zone >>>> if (zone->all_unreclaimable) >>>> continue >>>> if !all_unreclaimable(zonelist, sc) >>>> return 1 >>>> >>>> __alloc_pages_slowpath() >>>> retry: >>>> did_some_progress = do_try_to_free_pages(page) >>>> ... >>>> if (!page&& did_some_progress) >>>> retry; >>>> >>>> Signed-off-by: Andrey Vagin >>>> --- >>>> mm/vmscan.c | 2 ++ >>>> 1 files changed, 2 insertions(+), 0 deletions(-) >>>> >>>> diff --git a/mm/vmscan.c b/mm/vmscan.c >>>> index 6771ea7..1c056f7 100644 >>>> --- a/mm/vmscan.c >>>> +++ b/mm/vmscan.c >>>> @@ -2002,6 +2002,8 @@ static bool all_unreclaimable(struct zonelist *zonelist, >>>> >>>> for_each_zone_zonelist_nodemask(zone, z, zonelist, >>>> gfp_zone(sc->gfp_mask), sc->nodemask) { >>>> + if (zone->all_unreclaimable) >>>> + continue; >>>> if (!populated_zone(zone)) >>>> continue; >>>> if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) >>> zone_reclaimable checks it. Isn't it enough? >> I sent one more patch [PATCH] mm: skip zombie in OOM-killer. >> This two patches are enough. > Sorry if I confused you. > I mean zone->all_unreclaimable become true if !zone_reclaimable in balance_pgdat. > zone_reclaimable compares recent pages_scanned with the number of zone lru pages. > So too many page scanning in small lru pages makes the zone to unreclaimable zone. > > In all_unreclaimable, we calls zone_reclaimable to detect it. > It's the same thing with your patch. balance_pgdat set zone->all_unreclaimable, but the problem is that it is cleaned late. The problem is that zone->all_unreclaimable = True, but zone_reclaimable() returns True too. zone->all_unreclaimable will be cleaned in free_*_pages, but this may be late. It is enough allocate one page from page cache, that zone_reclaimable() returns True and zone->all_unreclaimable becomes True. >>> Does the hang up really happen or see it by code review? >> Yes. You can reproduce it for help the attached python program. It's >> not very clever:) >> It make the following actions in loop: >> 1. fork >> 2. mmap >> 3. touch memory >> 4. read memory >> 5. munmmap > It seems the test program makes fork bombs and memory hogging. > If you applied this patch, the problem is gone? Yes. >>>> -- >>>> 1.7.1 >>>> >>>> -- >>>> 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 >> import sys, time, mmap, os >> from subprocess import Popen, PIPE >> import random >> >> global mem_size >> >> def info(msg): >> pid = os.getpid() >> print>> sys.stderr, "%s: %s" % (pid, msg) >> sys.stderr.flush() >> >> >> >> def memory_loop(cmd = "a"): >> """ >> cmd may be: >> c: check memory >> else: touch memory >> """ >> c = 0 >> for j in xrange(0, mem_size): >> if cmd == "c": >> if f[j<<12] != chr(j % 255): >> info("Data corruption") >> sys.exit(1) >> else: >> f[j<<12] = chr(j % 255) >> >> while True: >> pid = os.fork() >> if (pid != 0): >> mem_size = random.randint(0, 56 * 4096) >> f = mmap.mmap(-1, mem_size<< 12, mmap.MAP_ANONYMOUS|mmap.MAP_PRIVATE) >> memory_loop() >> memory_loop("c") >> f.close() > -- 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/