From: Michal Hocko <mhocko@kernel.org>
To: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Johannes Weiner <hannes@cmpxchg.org>,
Nils Holland <nholland@tisys.org>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Chris Mason <clm@fb.com>, David Sterba <dsterba@suse.cz>,
linux-btrfs@vger.kernel.org
Subject: Re: [PATCH 2/2] mm, oom: do not enfore OOM killer for __GFP_NOFAIL automatically
Date: Sun, 18 Dec 2016 17:37:27 +0100 [thread overview]
Message-ID: <20161218163727.GC8440@dhcp22.suse.cz> (raw)
In-Reply-To: <18652e94-8f5c-dcf1-16e6-0deab6c642ec@I-love.SAKURA.ne.jp>
On Sat 17-12-16 20:17:07, Tetsuo Handa wrote:
[...]
> I feel that allowing access to memory reserves based on __GFP_NOFAIL might not
> make sense. My understanding is that actual I/O operation triggered by I/O
> requests by filesystem code are processed by other threads. Even if we grant
> access to memory reserves to GFP_NOFS | __GFP_NOFAIL allocations by fs code,
> I think that it is possible that memory allocations by underlying bio code
> fails to make a further progress unless memory reserves are granted as well.
IO layer should rely on mempools to guarantee a forward progress.
> Below is a typical trace which I observe under OOM lockuped situation (though
> this trace is from an OOM stress test using XFS).
>
> ----------------------------------------
> [ 1845.187246] MemAlloc: kworker/2:1(14498) flags=0x4208060 switches=323636 seq=48 gfp=0x2400000(GFP_NOIO) order=0 delay=430400 uninterruptible
> [ 1845.187248] kworker/2:1 D12712 14498 2 0x00000080
> [ 1845.187251] Workqueue: events_freezable_power_ disk_events_workfn
> [ 1845.187252] Call Trace:
> [ 1845.187253] ? __schedule+0x23f/0xba0
> [ 1845.187254] schedule+0x38/0x90
> [ 1845.187255] schedule_timeout+0x205/0x4a0
> [ 1845.187256] ? del_timer_sync+0xd0/0xd0
> [ 1845.187257] schedule_timeout_uninterruptible+0x25/0x30
> [ 1845.187258] __alloc_pages_nodemask+0x1035/0x10e0
> [ 1845.187259] ? alloc_request_struct+0x14/0x20
> [ 1845.187261] alloc_pages_current+0x96/0x1b0
> [ 1845.187262] ? bio_alloc_bioset+0x20f/0x2e0
> [ 1845.187264] bio_copy_kern+0xc4/0x180
> [ 1845.187265] blk_rq_map_kern+0x6f/0x120
> [ 1845.187268] __scsi_execute.isra.23+0x12f/0x160
> [ 1845.187270] scsi_execute_req_flags+0x8f/0x100
> [ 1845.187271] sr_check_events+0xba/0x2b0 [sr_mod]
> [ 1845.187274] cdrom_check_events+0x13/0x30 [cdrom]
> [ 1845.187275] sr_block_check_events+0x25/0x30 [sr_mod]
> [ 1845.187276] disk_check_events+0x5b/0x150
> [ 1845.187277] disk_events_workfn+0x17/0x20
> [ 1845.187278] process_one_work+0x1fc/0x750
> [ 1845.187279] ? process_one_work+0x167/0x750
> [ 1845.187279] worker_thread+0x126/0x4a0
> [ 1845.187280] kthread+0x10a/0x140
> [ 1845.187281] ? process_one_work+0x750/0x750
> [ 1845.187282] ? kthread_create_on_node+0x60/0x60
> [ 1845.187283] ret_from_fork+0x2a/0x40
> ----------------------------------------
>
> I think that this GFP_NOIO allocation request needs to consume more memory reserves
> than GFP_NOFS allocation request to make progress.
AFAIU, this is an allocation path which doesn't block a forward progress
on a regular IO. It is merely a check whether there is a new medium in
the CDROM (aka regular polling of the device). I really fail to see any
reason why this one should get any access to memory reserves at all.
I actually do not see any reason why it should be NOIO in the first
place but I am not familiar with this code much so there might be some
reasons for that. The fact that it might stall under a heavy memory
pressure is sad but who actually cares?
> Do we want to add __GFP_NOFAIL to this GFP_NOIO allocation request
> in order to allow access to memory reserves as well as GFP_NOFS |
> __GFP_NOFAIL allocation request?
Why?
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2016-12-18 16:37 UTC|newest]
Thread overview: 78+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-15 22:57 OOM: Better, but still there on 4.9 Nils Holland
2016-12-16 7:39 ` Michal Hocko
2016-12-16 15:58 ` OOM: Better, but still there on Michal Hocko
2016-12-16 15:58 ` [PATCH 1/2] mm: consolidate GFP_NOFAIL checks in the allocator slowpath Michal Hocko
2016-12-16 15:58 ` [PATCH 2/2] mm, oom: do not enfore OOM killer for __GFP_NOFAIL automatically Michal Hocko
2016-12-16 17:31 ` Johannes Weiner
2016-12-16 22:12 ` Michal Hocko
2016-12-17 11:17 ` Tetsuo Handa
2016-12-18 16:37 ` Michal Hocko [this message]
2016-12-16 18:47 ` OOM: Better, but still there on Nils Holland
2016-12-17 0:02 ` Michal Hocko
2016-12-17 12:59 ` Nils Holland
2016-12-17 14:44 ` Tetsuo Handa
2016-12-17 17:11 ` Nils Holland
2016-12-17 21:06 ` Nils Holland
2016-12-18 5:14 ` Tetsuo Handa
2016-12-19 13:45 ` Michal Hocko
2016-12-20 2:08 ` Nils Holland
2016-12-21 7:36 ` Michal Hocko
2016-12-21 11:00 ` Tetsuo Handa
2016-12-21 11:16 ` Michal Hocko
2016-12-21 14:04 ` Chris Mason
2016-12-22 10:10 ` Nils Holland
2016-12-22 10:27 ` Michal Hocko
2016-12-22 10:35 ` Nils Holland
2016-12-22 10:46 ` Tetsuo Handa
2016-12-22 19:17 ` Michal Hocko
2016-12-22 21:46 ` Nils Holland
2016-12-23 10:51 ` Michal Hocko
2016-12-23 12:18 ` Nils Holland
2016-12-23 12:57 ` Michal Hocko
2016-12-23 14:47 ` [RFC PATCH] mm, memcg: fix (Re: OOM: Better, but still there on) Michal Hocko
2016-12-23 22:26 ` Nils Holland
2016-12-26 12:48 ` Michal Hocko
2016-12-26 18:57 ` Nils Holland
2016-12-27 8:08 ` Michal Hocko
2016-12-27 11:23 ` Nils Holland
2016-12-27 11:27 ` Michal Hocko
2016-12-27 15:55 ` Michal Hocko
2016-12-27 16:28 ` [PATCH] mm, vmscan: consider eligible zones in get_scan_count kbuild test robot
2016-12-28 8:51 ` Michal Hocko
2016-12-27 19:33 ` [RFC PATCH] mm, memcg: fix (Re: OOM: Better, but still there on) Nils Holland
2016-12-28 8:57 ` Michal Hocko
2016-12-29 1:20 ` Minchan Kim
2016-12-29 9:04 ` Michal Hocko
2016-12-30 2:05 ` Minchan Kim
2016-12-30 10:40 ` Michal Hocko
2016-12-29 0:31 ` Minchan Kim
2016-12-29 0:48 ` Minchan Kim
2016-12-29 8:52 ` Michal Hocko
2016-12-30 10:19 ` Mel Gorman
2016-12-30 11:05 ` Michal Hocko
2016-12-30 12:43 ` Mel Gorman
2016-12-25 22:25 ` [lkp-developer] [mm, memcg] d18e2b2aca: WARNING:at_mm/memcontrol.c:#mem_cgroup_update_lru_size kernel test robot
2016-12-26 12:26 ` Michal Hocko
2016-12-26 12:50 ` Michal Hocko
2016-12-18 0:28 ` OOM: Better, but still there on Xin Zhou
2016-12-16 18:15 ` OOM: Better, but still there on 4.9 Chris Mason
2016-12-16 22:14 ` Michal Hocko
2016-12-16 22:47 ` Chris Mason
2016-12-16 23:31 ` Michal Hocko
2016-12-16 19:50 ` Chris Mason
-- strict thread matches above, loose matches on Subject: below --
2016-12-01 15:25 [PATCH 0/2] GFP_NOFAIL cleanups Michal Hocko
2016-12-01 15:25 ` [PATCH 2/2] mm, oom: do not enfore OOM killer for __GFP_NOFAIL automatically Michal Hocko
2016-12-02 7:23 ` Vlastimil Babka
2016-12-05 13:45 ` Tetsuo Handa
2016-12-05 14:10 ` Michal Hocko
2016-12-06 8:27 ` Michal Hocko
2016-12-06 10:38 ` Tetsuo Handa
2016-12-06 11:03 ` Vlastimil Babka
2016-12-06 19:25 ` Michal Hocko
2016-12-06 19:22 ` Michal Hocko
2016-12-08 12:53 ` Tetsuo Handa
2016-12-08 13:47 ` Michal Hocko
2016-12-11 11:23 ` Tetsuo Handa
2016-12-11 13:53 ` Tetsuo Handa
2016-12-12 8:52 ` Michal Hocko
2016-12-12 8:48 ` Michal Hocko
2016-12-14 10:34 ` Michal Hocko
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