From: Michal Hocko <mhocko@kernel.org>
To: Naresh Kamboju <naresh.kamboju@linaro.org>
Cc: Chris Down <chris@chrisdown.name>,
Yafang Shao <laoar.shao@gmail.com>,
Anders Roxell <anders.roxell@linaro.org>,
"Linux F2FS DEV,
Mailing List" <linux-f2fs-devel@lists.sourceforge.net>,
linux-ext4 <linux-ext4@vger.kernel.org>,
linux-block <linux-block@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
open list <linux-kernel@vger.kernel.org>,
Linux-Next Mailing List <linux-next@vger.kernel.org>,
linux-mm <linux-mm@kvack.org>, Arnd Bergmann <arnd@arndb.de>,
Andreas Dilger <adilger.kernel@dilger.ca>,
Jaegeuk Kim <jaegeuk@kernel.org>, Theodore Ts'o <tytso@mit.edu>,
Chao Yu <chao@kernel.org>, Hugh Dickins <hughd@google.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Matthew Wilcox <willy@infradead.org>,
Chao Yu <yuchao0@huawei.com>,
lkft-triage@lists.linaro.org,
Johannes Weiner <hannes@cmpxchg.org>,
Roman Gushchin <guro@fb.com>, Cgroups <cgroups@vger.kernel.org>
Subject: Re: mm: mkfs.ext4 invoked oom-killer on i386 - pagecache_get_page
Date: Wed, 17 Jun 2020 18:06:24 +0200 [thread overview]
Message-ID: <20200617160624.GS9499@dhcp22.suse.cz> (raw)
In-Reply-To: <CA+G9fYu+FB1PE0AMmE-9MrHpayE9kChwTyc3zfM6V83uQ0zcQA@mail.gmail.com>
On Wed 17-06-20 21:23:05, Naresh Kamboju wrote:
> On Wed, 17 Jun 2020 at 19:41, Michal Hocko <mhocko@kernel.org> wrote:
> >
> > [Our emails have crossed]
> >
> > On Wed 17-06-20 14:57:58, Chris Down wrote:
> > > Naresh Kamboju writes:
> > > > mkfs -t ext4 /dev/disk/by-id/ata-TOSHIBA_MG04ACA100N_Y8RQK14KF6XF
> > > > mke2fs 1.43.8 (1-Jan-2018)
> > > > Creating filesystem with 244190646 4k blocks and 61054976 inodes
> > > > Filesystem UUID: 7c380766-0ed8-41ba-a0de-3c08e78f1891
> > > > Superblock backups stored on blocks:
> > > > 32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,
> > > > 4096000, 7962624, 11239424, 20480000, 23887872, 71663616, 78675968,
> > > > 102400000, 214990848
> > > > Allocating group tables: 0/7453 done
> > > > Writing inode tables: 0/7453 done
> > > > Creating journal (262144 blocks): [ 51.544525] under min:0 emin:0
> > > > [ 51.845304] under min:0 emin:0
> > > > [ 51.848738] under min:0 emin:0
> > > > [ 51.858147] under min:0 emin:0
> > > > [ 51.861333] under min:0 emin:0
> > > > [ 51.862034] under min:0 emin:0
> > > > [ 51.862442] under min:0 emin:0
> > > > [ 51.862763] under min:0 emin:0
> > >
> > > Thanks, this helps a lot. Somehow we're entering mem_cgroup_below_min even
> > > when min/emin is 0 (which should indeed be the case if you haven't set them
> > > in the hierarchy).
> > >
> > > My guess is that page_counter_read(&memcg->memory) is 0, which means
> > > mem_cgroup_below_min will return 1.
> >
> > Yes this is the case because this is likely the root memcg which skips
> > all charges.
> >
> > > However, I don't know for sure why that should then result in the OOM killer
> > > coming along. My guess is that since this memcg has 0 pages to scan anyway,
> > > we enter premature OOM under some conditions. I don't know why we wouldn't
> > > have hit that with the old version of mem_cgroup_protected that returned
> > > MEMCG_PROT_* members, though.
> >
> > Not really. There is likely no other memcg to reclaim from and assuming
> > min limit protection will result in no reclaimable memory and thus the
> > OOM killer.
> >
> > > Can you please try the patch with the `>=` checks in mem_cgroup_below_min
> > > and mem_cgroup_below_low changed to `>`? If that fixes it, then that gives a
> > > strong hint about what's going on here.
> >
> > This would work but I believe an explicit check for the root memcg would
> > be easier to spot the reasoning.
>
> May I request you to send debugging or proposed fix patches here.
> I am happy to do more testing.
Sure, here is the diff to test.
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index c74a8f2323f1..6b5a31672fbe 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -392,6 +392,13 @@ static inline bool mem_cgroup_below_low(struct mem_cgroup *memcg)
if (mem_cgroup_disabled())
return false;
+ /*
+ * Root memcg doesn't account charges and doesn't support
+ * protection
+ */
+ if (mem_cgroup_is_root(memcg))
+ return false;
+
return READ_ONCE(memcg->memory.elow) >=
page_counter_read(&memcg->memory);
}
@@ -401,6 +408,13 @@ static inline bool mem_cgroup_below_min(struct mem_cgroup *memcg)
if (mem_cgroup_disabled())
return false;
+ /*
+ * Root memcg doesn't account charges and doesn't support
+ * protection
+ */
+ if (mem_cgroup_is_root(memcg))
+ return false;
+
return READ_ONCE(memcg->memory.emin) >=
page_counter_read(&memcg->memory);
}
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2020-06-17 16:06 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-01 12:38 mm: mkfs.ext4 invoked oom-killer on i386 - pagecache_get_page Naresh Kamboju
2020-05-01 20:58 ` Andrew Morton
2020-05-18 14:10 ` Naresh Kamboju
2020-05-19 7:52 ` Michal Hocko
2020-05-19 8:11 ` Arnd Bergmann
2020-05-19 8:45 ` Michal Hocko
2020-05-20 11:56 ` Naresh Kamboju
2020-05-20 17:59 ` Naresh Kamboju
2020-05-20 19:09 ` Chris Down
2020-05-21 9:22 ` Naresh Kamboju
2020-05-21 9:35 ` Arnd Bergmann
2020-05-21 9:55 ` Michal Hocko
2020-05-21 10:41 ` Naresh Kamboju
2020-05-21 10:58 ` Michal Hocko
2020-05-21 12:24 ` Hugh Dickins
2020-05-21 12:44 ` Michal Hocko
2020-05-21 19:17 ` Johannes Weiner
2020-05-21 20:06 ` Hugh Dickins
2020-05-21 21:58 ` Johannes Weiner
2020-05-21 23:35 ` Hugh Dickins
2020-05-28 14:59 ` Michal Hocko
2020-05-21 16:34 ` Michal Hocko
2020-05-21 19:00 ` Naresh Kamboju
2020-05-21 20:53 ` Naresh Kamboju
2020-05-28 15:03 ` Michal Hocko
2020-05-28 16:17 ` Naresh Kamboju
2020-05-28 16:41 ` Chris Down
2020-05-29 1:50 ` Yafang Shao
2020-05-29 1:56 ` Chris Down
2020-05-29 9:49 ` Michal Hocko
2020-06-11 9:55 ` Michal Hocko
2020-06-12 9:43 ` Naresh Kamboju
2020-06-12 12:09 ` Michal Hocko
2020-06-17 13:37 ` Naresh Kamboju
2020-06-17 13:57 ` Chris Down
2020-06-17 14:11 ` Michal Hocko
2020-06-17 15:53 ` Naresh Kamboju
2020-06-17 16:06 ` Michal Hocko [this message]
2020-06-17 20:13 ` Naresh Kamboju
2020-06-17 21:09 ` Chris Down
2020-06-18 1:43 ` Yafang Shao
2020-06-18 12:37 ` Chris Down
2020-06-18 12:41 ` Michal Hocko
2020-06-18 12:49 ` Chris Down
2020-06-18 14:59 ` Yafang Shao
2020-06-17 13:59 ` Michal Hocko
2020-06-17 14:08 ` Chris Down
2020-05-21 2:39 ` Yafang Shao
2020-05-21 8:58 ` Naresh Kamboju
2020-05-21 9:47 ` Yafang Shao
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