From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail190.messagelabs.com (mail190.messagelabs.com [216.82.249.51]) by kanga.kvack.org (Postfix) with ESMTP id 778F18D0039 for ; Sat, 5 Mar 2011 10:53:29 -0500 (EST) Received: by pwi10 with SMTP id 10so769525pwi.14 for ; Sat, 05 Mar 2011 07:53:27 -0800 (PST) Date: Sun, 6 Mar 2011 00:53:16 +0900 From: Minchan Kim Subject: Re: [PATCH] mm: check zone->all_unreclaimable in all_unreclaimable() Message-ID: <20110305155316.GB1918@barrios-desktop> References: <1299325456-2687-1-git-send-email-avagin@openvz.org> <20110305152056.GA1918@barrios-desktop> <4D72580D.4000208@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4D72580D.4000208@gmail.com> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Vagin Cc: Andrey Vagin , Andrew Morton , Mel Gorman , KOSAKI Motohiro , linux-mm@kvack.org, linux-kernel@vger.kernel.org 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. > >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? > > >>-- > >>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() -- Kind regards, Minchan Kim -- 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