From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx106.postini.com [74.125.245.106]) by kanga.kvack.org (Postfix) with SMTP id B33606B0032 for ; Tue, 3 Sep 2013 06:01:20 -0400 (EDT) Date: Tue, 3 Sep 2013 12:01:17 +0200 From: Michal Hocko Subject: Re: [PATCH] memcg: fix multiple large threshold notifications Message-ID: <20130903100117.GA14914@dhcp22.suse.cz> References: <1377994002-1857-1-git-send-email-gthelen@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1377994002-1857-1-git-send-email-gthelen@google.com> Sender: owner-linux-mm@kvack.org List-ID: To: Greg Thelen Cc: Andrew Morton , Johannes Weiner , Balbir Singh , KAMEZAWA Hiroyuki , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org On Sat 31-08-13 17:06:42, Greg Thelen wrote: > A memory cgroup with (1) multiple threshold notifications and (2) at > least one threshold >=2G was not reliable. Specifically the > notifications would either not fire or would not fire in the proper > order. > > The __mem_cgroup_threshold() signaling logic depends on keeping 64 bit > thresholds in sorted order. mem_cgroup_usage_register_event() sorts > them with compare_thresholds(), which returns the difference of two 64 > bit thresholds as an int. If the difference is positive but has > bit[31] set, then sort() treats the difference as negative and breaks > sort order. > > This fix compares the two arbitrary 64 bit thresholds returning the > classic -1, 0, 1 result. > > The test below sets two notifications (at 0x1000 and 0x81001000): > cd /sys/fs/cgroup/memory > mkdir x > for x in 4096 2164264960; do > cgroup_event_listener x/memory.usage_in_bytes $x | sed "s/^/$x listener:/" & > done > echo $$ > x/cgroup.procs > anon_leaker 500M > > v3.11-rc7 fails to signal the 4096 event listener: > Leaking... > Done leaking pages. > > Patched v3.11-rc7 properly notifies: > Leaking... > 4096 listener:2013:8:31:14:13:36 > Done leaking pages. > > The fixed bug is old. It appears to date back to the introduction of > memcg threshold notifications in v2.6.34-rc1-116-g2e72b6347c94 "memcg: > implement memory thresholds" > > Signed-off-by: Greg Thelen Acked-by: Michal Hocko I guess this qualifies to the stable tree. Thanks! > --- > mm/memcontrol.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 0878ff7..aa44621 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -5616,7 +5616,13 @@ static int compare_thresholds(const void *a, const void *b) > const struct mem_cgroup_threshold *_a = a; > const struct mem_cgroup_threshold *_b = b; > > - return _a->threshold - _b->threshold; > + if (_a->threshold > _b->threshold) > + return 1; > + > + if (_a->threshold < _b->threshold) > + return -1; > + > + return 0; > } > > static int mem_cgroup_oom_notify_cb(struct mem_cgroup *memcg) > -- > 1.8.4 > -- Michal Hocko SUSE Labs -- 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