From: Michal Hocko <mhocko@kernel.org>
To: Brian Foster <bfoster@redhat.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
david@fromorbit.com, dchinner@redhat.com, hch@lst.de,
mgorman@suse.de, viro@ZenIV.linux.org.uk, linux-mm@kvack.org,
hannes@cmpxchg.org, linux-kernel@vger.kernel.org,
darrick.wong@oracle.com, linux-xfs@vger.kernel.org
Subject: Re: [RFC PATCH 1/2] mm, vmscan: account the number of isolated pages per zone
Date: Mon, 6 Feb 2017 15:42:22 +0100 [thread overview]
Message-ID: <20170206144221.GE10298@dhcp22.suse.cz> (raw)
In-Reply-To: <20170206143533.GC57865@bfoster.bfoster>
On Mon 06-02-17 09:35:33, Brian Foster wrote:
> On Mon, Feb 06, 2017 at 03:29:24PM +0900, Tetsuo Handa wrote:
> > Brian Foster wrote:
> > > On Fri, Feb 03, 2017 at 03:50:09PM +0100, Michal Hocko wrote:
> > > > [Let's CC more xfs people]
> > > >
> > > > On Fri 03-02-17 19:57:39, Tetsuo Handa wrote:
> > > > [...]
> > > > > (1) I got an assertion failure.
> > > >
> > > > I suspect this is a result of
> > > > http://lkml.kernel.org/r/20170201092706.9966-2-mhocko@kernel.org
> > > > I have no idea what the assert means though.
> > > >
> > > > >
> > > > > [ 969.626518] Killed process 6262 (oom-write) total-vm:2166856kB, anon-rss:1128732kB, file-rss:4kB, shmem-rss:0kB
> > > > > [ 969.958307] oom_reaper: reaped process 6262 (oom-write), now anon-rss:0kB, file-rss:0kB, shmem-rss:0kB
> > > > > [ 972.114644] XFS: Assertion failed: oldlen > newlen, file: fs/xfs/libxfs/xfs_bmap.c, line: 2867
> > >
> > > Indirect block reservation underrun on delayed allocation extent merge.
> > > These are extra blocks are used for the inode bmap btree when a delalloc
> > > extent is converted to physical blocks. We're in a case where we expect
> > > to only ever free excess blocks due to a merge of extents with
> > > independent reservations, but a situation occurs where we actually need
> > > blocks and hence the assert fails. This can occur if an extent is merged
> > > with one that has a reservation less than the expected worst case
> > > reservation for its size (due to previous extent splits due to hole
> > > punches, for example). Therefore, I think the core expectation that
> > > xfs_bmap_add_extent_hole_delay() will always have enough blocks
> > > pre-reserved is invalid.
> > >
> > > Can you describe the workload that reproduces this? FWIW, I think the
> > > way xfs_bmap_add_extent_hole_delay() currently works is likely broken
> > > and have a couple patches to fix up indlen reservation that I haven't
> > > posted yet. The diff that deals with this particular bit is appended.
> > > Care to give that a try?
> >
> > The workload is to write to a single file on XFS from 10 processes demonstrated at
> > http://lkml.kernel.org/r/201512052133.IAE00551.LSOQFtMFFVOHOJ@I-love.SAKURA.ne.jp
> > using "while :; do ./oom-write; done" loop on a VM with 4CPUs / 2048MB RAM.
> > With this XFS_FILBLKS_MIN() change applied, I no longer hit assertion failures.
> >
>
> Thanks for testing. Well, that's an interesting workload. I couldn't
> reproduce on a few quick tries in a similarly configured vm.
>
> Normally I'd expect to see this kind of thing on a hole punching
> workload or dealing with large, sparse files that make use of
> speculative preallocation (post-eof blocks allocated in anticipation of
> file extending writes). I'm wondering if what is happening here is that
> the appending writes and file closes due to oom kills are generating
> speculative preallocs and prealloc truncates, respectively, and that
> causes prealloc extents at the eof boundary to be split up and then
> re-merged by surviving appending writers.
Can those preallocs be affected by
http://lkml.kernel.org/r/20170201092706.9966-2-mhocko@kernel.org ?
--
Michal Hocko
SUSE Labs
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next prev parent reply other threads:[~2017-02-06 14:42 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-18 13:44 [RFC PATCH 0/2] fix unbounded too_many_isolated Michal Hocko
2017-01-18 13:44 ` [RFC PATCH 1/2] mm, vmscan: account the number of isolated pages per zone Michal Hocko
2017-01-18 14:46 ` Mel Gorman
2017-01-18 15:15 ` Michal Hocko
2017-01-18 15:54 ` Mel Gorman
2017-01-18 16:17 ` Michal Hocko
2017-01-18 17:00 ` Mel Gorman
2017-01-18 17:29 ` Michal Hocko
2017-01-19 10:07 ` Mel Gorman
2017-01-19 11:23 ` Michal Hocko
2017-01-19 13:11 ` Mel Gorman
2017-01-20 13:27 ` Tetsuo Handa
2017-01-21 7:42 ` Tetsuo Handa
2017-01-25 10:15 ` Michal Hocko
2017-01-25 10:19 ` Christoph Hellwig
2017-01-25 10:46 ` Michal Hocko
2017-01-25 11:09 ` Tetsuo Handa
2017-01-25 13:00 ` Michal Hocko
2017-01-27 14:49 ` Michal Hocko
2017-01-28 15:27 ` Tetsuo Handa
2017-01-30 8:55 ` Michal Hocko
2017-02-02 10:14 ` Michal Hocko
2017-02-03 10:57 ` Tetsuo Handa
2017-02-03 14:41 ` Michal Hocko
2017-02-03 14:50 ` Michal Hocko
2017-02-03 17:24 ` Brian Foster
2017-02-06 6:29 ` Tetsuo Handa
2017-02-06 14:35 ` Brian Foster
2017-02-06 14:42 ` Michal Hocko [this message]
2017-02-06 15:47 ` Brian Foster
2017-02-07 10:30 ` Tetsuo Handa
2017-02-07 16:54 ` Brian Foster
2017-02-03 14:55 ` Michal Hocko
2017-02-05 10:43 ` Tetsuo Handa
2017-02-06 10:34 ` Michal Hocko
2017-02-06 10:39 ` Michal Hocko
2017-02-07 21:12 ` Michal Hocko
2017-02-08 9:24 ` Peter Zijlstra
2017-02-21 9:40 ` Michal Hocko
2017-02-21 14:35 ` Tetsuo Handa
2017-02-21 15:53 ` Michal Hocko
2017-02-22 2:02 ` Tetsuo Handa
2017-02-22 7:54 ` Michal Hocko
2017-02-26 6:30 ` Tetsuo Handa
2017-01-31 11:58 ` Michal Hocko
2017-01-31 12:51 ` Christoph Hellwig
2017-01-31 13:21 ` Michal Hocko
2017-01-25 10:33 ` [RFC PATCH 1/2] mm, vmscan: account the number of isolated pagesper zone Tetsuo Handa
2017-01-25 12:34 ` Michal Hocko
2017-01-25 13:13 ` [RFC PATCH 1/2] mm, vmscan: account the number of isolated pages per zone Tetsuo Handa
2017-01-25 9:53 ` Michal Hocko
2017-01-20 6:42 ` Hillf Danton
2017-01-20 9:25 ` Mel Gorman
2017-01-18 13:44 ` [RFC PATCH 2/2] mm, vmscan: do not loop on too_many_isolated for ever Michal Hocko
2017-01-18 14:50 ` Mel Gorman
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