Re: [PATCH v7] mm: Add memory allocation watchdog kernel thread.
From: Brian Foster
Date: Fri Mar 10 2017 - 08:50:22 EST
On Fri, Mar 10, 2017 at 08:19:58PM +0900, Tetsuo Handa wrote:
> Andrew Morton wrote:
> > On Thu, 9 Mar 2017 19:46:14 +0900 Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> wrote:
> > > Tetsuo Handa wrote:
> > > > This patch adds a watchdog which periodically reports number of memory
> > > > allocating tasks, dying tasks and OOM victim tasks when some task is
> > > > spending too long time inside __alloc_pages_slowpath(). This patch also
> > > > serves as a hook for obtaining additional information using SystemTap
> > > > (e.g. examine other variables using printk(), capture a crash dump by
> > > > calling panic()) by triggering a callback only when a stall is detected.
> > > > Ability to take administrator-controlled actions based on some threshold
> > > > is a big advantage gained by introducing a state tracking.
> > > >
> > > > Commit 63f53dea0c9866e9 ("mm: warn about allocations which stall for
> > > > too long") was a great step for reducing possibility of silent hang up
> > > > problem caused by memory allocation stalls [1]. However, there are
> > > > reports of long stalls (e.g. [2] is over 30 minutes!) and lockups (e.g.
> > > > [3] is an "unable to invoke the OOM killer due to !__GFP_FS allocation"
> > > > lockup problem) where this patch is more useful than that commit, for
> > > > this patch can report possibly related tasks even if allocating tasks
> > > > are unexpectedly blocked for so long. Regarding premature OOM killer
> > > > invocation, tracepoints which can accumulate samples in short interval
> > > > would be useful. But regarding too late to report allocation stalls,
> > > > this patch which can capture all tasks (for reporting overall situation)
> > > > in longer interval and act as a trigger (for accumulating short interval
> > > > samples) would be useful.
> > )
> > > Andrew, do you have any questions on this patch?
> > > I really need this patch for finding bugs which MM people overlook.
> >
> > Undecided. I can see the need but it is indeed quite a large lump of
> > code. Perhaps some additional examples of how this new code was used
> > to understand and improve real-world kernel problems would be persuasive.
>
> This patch is aimed for help bisecting whether unexpected hung cases are related to
> memory allocation. By merging this patch (and enabling this watchdog in enterprise
> systems via kernels supported by distributors), we can identify patterns/cases of
> problems (if related to memory allocation) and improve quality of Linux kernels
> by fixing problems related to memory allocation.
>
> I was working at a support center for 3 years and had many cases where Linux
> systems encountered unexpected silent hangup/reboot problem. In most cases, all
> clue available was limited to sar (in sysstat package) showing that free memory
> was low just before unexpected hung/reboot.
>
> As a nature of such problems, it is very hard for administrators to collect
> information for analysis; let alone identify the cause of problems. As a result,
> such problems are left unrecognized/unsolved at the support center, and are
> seldom reported to distributors/developers in order to ask for fixes.
>
> Michal Hocko wrote:
> > Well, it is true that the watchdog can provide much more information
> > than we can gather with other debugging options we currently have when
> > allocations run away. So I am not questioning this is useful when doing
> > memory stress testing and trying to trigger corner cases but I am not
> > really sure how much this will be useful in production systems, though.
> > Tracking is not for free both in runtime and longterm in maintenance.
>
> I don't think that my stress testing is hitting bugs which do not occur in
> production systems. But I can't prove it without using watchdog mechanism.
> Today I heard about a case where an enterprise system hung last Sunday due to
> XFS deadlock by memory allocation. This was rather a lucky case where
> administrator of that system was able to capture vmcore. In most cases,
> administrators can't capture even SysRq-t; let alone vmcore. Therefore,
> automatic watchdog is highly appreciated.
>
>
>
> Or, did you mean "some additional examples of how this new code was used
> to understand and improve real-world kernel problems" as how this patch
> helped in [2] [3] ?
>
> Regarding [3] (now continued as
> http://lkml.kernel.org/r/201703031948.CHJ81278.VOHSFFFOOLJQMt@xxxxxxxxxxxxxxxxxxx ),
> I used this patch for confirming the following things.
>
> (1) kswapd cannot make progress waiting for lock.
>
> ----------
> [ 518.900038] MemAlloc: kswapd0(69) flags=0xa40840 switches=23883 uninterruptible
> [ 518.902095] kswapd0 D10776 69 2 0x00000000
> [ 518.903784] Call Trace:
> [ 518.904849] __schedule+0x336/0xe00
> [ 518.906118] schedule+0x3d/0x90
> [ 518.907314] io_schedule+0x16/0x40
> [ 518.908622] __xfs_iflock+0x129/0x140 [xfs]
> [ 518.910027] ? autoremove_wake_function+0x60/0x60
> [ 518.911559] xfs_reclaim_inode+0x162/0x440 [xfs]
> [ 518.913068] xfs_reclaim_inodes_ag+0x2cf/0x4f0 [xfs]
> [ 518.914611] ? xfs_reclaim_inodes_ag+0xf2/0x4f0 [xfs]
> [ 518.916148] ? trace_hardirqs_on+0xd/0x10
> [ 518.917465] ? try_to_wake_up+0x59/0x7a0
> [ 518.918758] ? wake_up_process+0x15/0x20
> [ 518.920067] xfs_reclaim_inodes_nr+0x33/0x40 [xfs]
> [ 518.921560] xfs_fs_free_cached_objects+0x19/0x20 [xfs]
> [ 518.923114] super_cache_scan+0x181/0x190
> [ 518.924435] shrink_slab+0x29f/0x6d0
> [ 518.925683] shrink_node+0x2fa/0x310
> [ 518.926909] kswapd+0x362/0x9b0
> [ 518.928061] kthread+0x10f/0x150
> [ 518.929218] ? mem_cgroup_shrink_node+0x3b0/0x3b0
> [ 518.930953] ? kthread_create_on_node+0x70/0x70
> [ 518.932380] ret_from_fork+0x31/0x40
>
> [ 1095.632984] MemAlloc: kswapd0(69) flags=0xa40840 switches=23883 uninterruptible
> [ 1095.632985] kswapd0 D10776 69 2 0x00000000
> [ 1095.632988] Call Trace:
> [ 1095.632991] __schedule+0x336/0xe00
> [ 1095.632994] schedule+0x3d/0x90
> [ 1095.632996] io_schedule+0x16/0x40
> [ 1095.633017] __xfs_iflock+0x129/0x140 [xfs]
> [ 1095.633021] ? autoremove_wake_function+0x60/0x60
> [ 1095.633051] xfs_reclaim_inode+0x162/0x440 [xfs]
> [ 1095.633072] xfs_reclaim_inodes_ag+0x2cf/0x4f0 [xfs]
> [ 1095.633106] ? xfs_reclaim_inodes_ag+0xf2/0x4f0 [xfs]
> [ 1095.633114] ? trace_hardirqs_on+0xd/0x10
> [ 1095.633116] ? try_to_wake_up+0x59/0x7a0
> [ 1095.633120] ? wake_up_process+0x15/0x20
> [ 1095.633156] xfs_reclaim_inodes_nr+0x33/0x40 [xfs]
> [ 1095.633178] xfs_fs_free_cached_objects+0x19/0x20 [xfs]
> [ 1095.633180] super_cache_scan+0x181/0x190
> [ 1095.633183] shrink_slab+0x29f/0x6d0
> [ 1095.633189] shrink_node+0x2fa/0x310
> [ 1095.633193] kswapd+0x362/0x9b0
> [ 1095.633200] kthread+0x10f/0x150
> [ 1095.633201] ? mem_cgroup_shrink_node+0x3b0/0x3b0
> [ 1095.633202] ? kthread_create_on_node+0x70/0x70
> [ 1095.633205] ret_from_fork+0x31/0x40
> ----------
>
> (2) All WQ_MEM_RECLAIM threads shown by show_workqueue_state()
> cannot make progress waiting for memory allocation.
>
> ----------
> [ 1095.633625] MemAlloc: xfs-data/sda1(451) flags=0x4228060 switches=45509 seq=1 gfp=0x1604240(GFP_NOFS|__GFP_NOWARN|__GFP_COMP|__GFP_NOTRACK) order=0 delay=652073
> [ 1095.633626] xfs-data/sda1 R running task 12696 451 2 0x00000000
> [ 1095.633663] Workqueue: xfs-data/sda1 xfs_end_io [xfs]
> [ 1095.633665] Call Trace:
> [ 1095.633668] __schedule+0x336/0xe00
> [ 1095.633671] schedule+0x3d/0x90
> [ 1095.633672] schedule_timeout+0x20d/0x510
> [ 1095.633675] ? lock_timer_base+0xa0/0xa0
> [ 1095.633678] schedule_timeout_uninterruptible+0x2a/0x30
> [ 1095.633680] __alloc_pages_slowpath+0x2b5/0xd95
> [ 1095.633687] __alloc_pages_nodemask+0x3e4/0x460
> [ 1095.633699] alloc_pages_current+0x97/0x1b0
> [ 1095.633702] new_slab+0x4cb/0x6b0
> [ 1095.633706] ___slab_alloc+0x3a3/0x620
> [ 1095.633728] ? kmem_alloc+0x96/0x120 [xfs]
> [ 1095.633730] ? ___slab_alloc+0x5c6/0x620
> [ 1095.633732] ? cpuacct_charge+0x38/0x1e0
> [ 1095.633767] ? kmem_alloc+0x96/0x120 [xfs]
> [ 1095.633770] __slab_alloc+0x46/0x7d
> [ 1095.633773] __kmalloc+0x301/0x3b0
> [ 1095.633802] kmem_alloc+0x96/0x120 [xfs]
> [ 1095.633804] ? kfree+0x1fa/0x330
> [ 1095.633842] xfs_log_commit_cil+0x489/0x710 [xfs]
> [ 1095.633864] __xfs_trans_commit+0x83/0x260 [xfs]
> [ 1095.633883] xfs_trans_commit+0x10/0x20 [xfs]
> [ 1095.633901] __xfs_setfilesize+0xdb/0x240 [xfs]
> [ 1095.633936] xfs_setfilesize_ioend+0x89/0xb0 [xfs]
> [ 1095.633954] ? xfs_setfilesize_ioend+0x5/0xb0 [xfs]
> [ 1095.633971] xfs_end_io+0x81/0x110 [xfs]
> [ 1095.633973] process_one_work+0x22b/0x760
> [ 1095.633975] ? process_one_work+0x194/0x760
> [ 1095.633997] rescuer_thread+0x1f2/0x3d0
> [ 1095.634002] kthread+0x10f/0x150
> [ 1095.634003] ? worker_thread+0x4b0/0x4b0
> [ 1095.634004] ? kthread_create_on_node+0x70/0x70
> [ 1095.634007] ret_from_fork+0x31/0x40
> [ 1095.634013] MemAlloc: xfs-eofblocks/s(456) flags=0x4228860 switches=15435 seq=1 gfp=0x1400240(GFP_NOFS|__GFP_NOWARN) order=0 delay=293074
> [ 1095.634014] xfs-eofblocks/s R running task 12032 456 2 0x00000000
> [ 1095.634037] Workqueue: xfs-eofblocks/sda1 xfs_eofblocks_worker [xfs]
> [ 1095.634038] Call Trace:
> [ 1095.634040] ? _raw_spin_lock+0x3d/0x80
> [ 1095.634042] ? vmpressure+0xd0/0x120
> [ 1095.634044] ? vmpressure+0xd0/0x120
> [ 1095.634047] ? vmpressure_prio+0x21/0x30
> [ 1095.634049] ? do_try_to_free_pages+0x70/0x300
> [ 1095.634052] ? try_to_free_pages+0x131/0x3f0
> [ 1095.634058] ? __alloc_pages_slowpath+0x3ec/0xd95
> [ 1095.634065] ? __alloc_pages_nodemask+0x3e4/0x460
> [ 1095.634069] ? alloc_pages_current+0x97/0x1b0
> [ 1095.634111] ? xfs_buf_allocate_memory+0x160/0x2a3 [xfs]
> [ 1095.634133] ? xfs_buf_get_map+0x2be/0x480 [xfs]
> [ 1095.634169] ? xfs_buf_read_map+0x2c/0x400 [xfs]
> [ 1095.634204] ? xfs_trans_read_buf_map+0x186/0x830 [xfs]
> [ 1095.634222] ? xfs_btree_read_buf_block.constprop.34+0x78/0xc0 [xfs]
> [ 1095.634239] ? xfs_btree_lookup_get_block+0x8a/0x180 [xfs]
> [ 1095.634257] ? xfs_btree_lookup+0xd0/0x3f0 [xfs]
> [ 1095.634296] ? kmem_zone_alloc+0x96/0x120 [xfs]
> [ 1095.634299] ? _raw_spin_unlock+0x27/0x40
> [ 1095.634315] ? xfs_bmbt_lookup_eq+0x1f/0x30 [xfs]
> [ 1095.634348] ? xfs_bmap_del_extent+0x1b2/0x1610 [xfs]
> [ 1095.634380] ? kmem_zone_alloc+0x96/0x120 [xfs]
> [ 1095.634400] ? __xfs_bunmapi+0x4db/0xda0 [xfs]
> [ 1095.634421] ? xfs_bunmapi+0x2b/0x40 [xfs]
> [ 1095.634459] ? xfs_itruncate_extents+0x1df/0x780 [xfs]
> [ 1095.634502] ? xfs_rename+0xc70/0x1080 [xfs]
> [ 1095.634525] ? xfs_free_eofblocks+0x1c4/0x230 [xfs]
> [ 1095.634546] ? xfs_inode_free_eofblocks+0x18d/0x280 [xfs]
> [ 1095.634565] ? xfs_inode_ag_walk.isra.13+0x2b5/0x620 [xfs]
> [ 1095.634582] ? xfs_inode_ag_walk.isra.13+0x91/0x620 [xfs]
> [ 1095.634618] ? xfs_inode_clear_eofblocks_tag+0x1a0/0x1a0 [xfs]
> [ 1095.634630] ? radix_tree_next_chunk+0x10b/0x2d0
> [ 1095.634635] ? radix_tree_gang_lookup_tag+0xd7/0x150
> [ 1095.634672] ? xfs_perag_get_tag+0x11d/0x370 [xfs]
> [ 1095.634690] ? xfs_perag_get_tag+0x5/0x370 [xfs]
> [ 1095.634709] ? xfs_inode_ag_iterator_tag+0x71/0xa0 [xfs]
> [ 1095.634726] ? xfs_inode_clear_eofblocks_tag+0x1a0/0x1a0 [xfs]
> [ 1095.634744] ? __xfs_icache_free_eofblocks+0x3b/0x40 [xfs]
> [ 1095.634759] ? xfs_eofblocks_worker+0x27/0x40 [xfs]
> [ 1095.634762] ? process_one_work+0x22b/0x760
> [ 1095.634763] ? process_one_work+0x194/0x760
> [ 1095.634784] ? rescuer_thread+0x1f2/0x3d0
> [ 1095.634788] ? kthread+0x10f/0x150
> [ 1095.634789] ? worker_thread+0x4b0/0x4b0
> [ 1095.634790] ? kthread_create_on_node+0x70/0x70
> [ 1095.634793] ? ret_from_fork+0x31/0x40
> ----------
>
Clearly we have some rescuer threads blocked on memory reclaim. What
about the rescuer threads that are not blocked in reclaim? For example,
the one that could very well be responsible for allowing xfsaild (and
thus kswapd) to proceed is here:
[ 1041.555227] xfs-buf/sda1 S14904 450 2 0x00000000
[ 1041.556813] Call Trace:
[ 1041.557796] __schedule+0x336/0xe00
[ 1041.558983] schedule+0x3d/0x90
[ 1041.560085] rescuer_thread+0x322/0x3d0
[ 1041.561333] kthread+0x10f/0x150
[ 1041.562464] ? worker_thread+0x4b0/0x4b0
[ 1041.563732] ? kthread_create_on_node+0x70/0x70
[ 1041.565123] ret_from_fork+0x31/0x40
I've pointed this out at least twice now in the original thread. :/
> (3) order-0 GFP_NOIO allocation request cannot make progress
> waiting for memory allocation.
>
> ----------
> [ 1095.631687] MemAlloc: kworker/2:0(27) flags=0x4208860 switches=38727 seq=21 gfp=0x1400000(GFP_NOIO) order=0 delay=652160
> [ 1095.631688] kworker/2:0 R running task 12680 27 2 0x00000000
> [ 1095.631739] Workqueue: events_freezable_power_ disk_events_workfn
> [ 1095.631740] Call Trace:
> [ 1095.631743] __schedule+0x336/0xe00
> [ 1095.631746] preempt_schedule_common+0x1f/0x31
> [ 1095.631747] _cond_resched+0x1c/0x30
> [ 1095.631749] shrink_slab+0x339/0x6d0
> [ 1095.631754] shrink_node+0x2fa/0x310
> [ 1095.631758] do_try_to_free_pages+0xe1/0x300
> [ 1095.631761] try_to_free_pages+0x131/0x3f0
> [ 1095.631765] __alloc_pages_slowpath+0x3ec/0xd95
> [ 1095.631771] __alloc_pages_nodemask+0x3e4/0x460
> [ 1095.631775] alloc_pages_current+0x97/0x1b0
> [ 1095.631779] bio_copy_kern+0xc9/0x180
> [ 1095.631830] blk_rq_map_kern+0x70/0x140
> [ 1095.631835] __scsi_execute.isra.22+0x13a/0x1e0
> [ 1095.631838] scsi_execute_req_flags+0x94/0x100
> [ 1095.631844] sr_check_events+0xbf/0x2b0 [sr_mod]
> [ 1095.631852] cdrom_check_events+0x18/0x30 [cdrom]
> [ 1095.631854] sr_block_check_events+0x2a/0x30 [sr_mod]
> [ 1095.631856] disk_check_events+0x60/0x170
> [ 1095.631859] disk_events_workfn+0x1c/0x20
> [ 1095.631862] process_one_work+0x22b/0x760
> [ 1095.631863] ? process_one_work+0x194/0x760
> [ 1095.631867] worker_thread+0x137/0x4b0
> [ 1095.631887] kthread+0x10f/0x150
> [ 1095.631889] ? process_one_work+0x760/0x760
> [ 1095.631890] ? kthread_create_on_node+0x70/0x70
> [ 1095.631893] ret_from_fork+0x31/0x40
> ----------
>
> (4) Number of stalling threads does not decrease over time while
> number of out_of_memory() calls increases over time.
>
> ----------
> [ 518.090012] MemAlloc-Info: stalling=184 dying=1 exiting=0 victim=1 oom_count=8441307
> [ 553.070829] MemAlloc-Info: stalling=184 dying=1 exiting=0 victim=1 oom_count=10318507
> [ 616.394649] MemAlloc-Info: stalling=186 dying=1 exiting=0 victim=1 oom_count=13908219
> [ 642.266252] MemAlloc-Info: stalling=186 dying=1 exiting=0 victim=1 oom_count=15180673
> [ 702.412189] MemAlloc-Info: stalling=187 dying=1 exiting=0 victim=1 oom_count=18732529
> [ 736.787879] MemAlloc-Info: stalling=187 dying=1 exiting=0 victim=1 oom_count=20565244
> [ 800.715759] MemAlloc-Info: stalling=188 dying=1 exiting=0 victim=1 oom_count=24411576
> [ 837.571405] MemAlloc-Info: stalling=188 dying=1 exiting=0 victim=1 oom_count=26463562
> [ 899.021495] MemAlloc-Info: stalling=189 dying=1 exiting=0 victim=1 oom_count=30144879
> [ 936.282709] MemAlloc-Info: stalling=189 dying=1 exiting=0 victim=1 oom_count=32129234
> [ 997.328119] MemAlloc-Info: stalling=190 dying=1 exiting=0 victim=1 oom_count=35657983
> [ 1033.977265] MemAlloc-Info: stalling=190 dying=1 exiting=0 victim=1 oom_count=37659912
> [ 1095.630961] MemAlloc-Info: stalling=190 dying=1 exiting=0 victim=1 oom_count=40639677
> [ 1095.821248] MemAlloc-Info: stalling=190 dying=1 exiting=0 victim=1 oom_count=40646791
> ----------
>
> Further interpretation is up to XFS people (Brian and Dave). So far, boosting priority
> (lowering watermark) of WQ_MEM_RECLAIM threads based on current_is_workqueue_rescuer()
> seems to be considered as a fix because writeback path already has a special case
> handling for the rescuer. But I'm not sure whether it helps getting writeback unstuck
> when writeback path is blocked on a lock rather than memory allocation. (Threads doing
> writeback and/or mempool allocations might be candidates for always reporting as with
> kswapd. That would be in followup patches.)
>
Using the rescuer context in those associated workqueues is probably a
good idea, it may even resolve (or workaround) this problem. As noted
above, however, I don't think we've proven that addresses this problem.
How would you expect current_is_workqueue_rescuer() to affect the idle
xfs-buf rescuer thread above? Is there something else going on that
could be blocking metadata buffer I/O completion via xfs-buf? We do have
the following, which I suppose suggests there is a pending work item:
[ 273.412600] workqueue xfs-buf/sda1: flags=0xc
[ 273.414486] pwq 4: cpus=2 node=0 flags=0x0 nice=0 active=1/1
[ 273.416415] pending: xfs_buf_ioend_work [xfs]
... but otherwise I don't see anything executing xfs_buf_ioend()..? Am I
missing something?
AFAICT, all the information we have so far shows is that kswapd is
blocked in XFS, and as a result of that, we've ultimately deadlocked on
memory allocation.
Brian
> ----------
> [ 1044.701393] kworker/u256:0 D10024 8444 2 0x00000080
> [ 1044.703017] Workqueue: writeback wb_workfn (flush-8:0)
> [ 1044.704550] Call Trace:
> [ 1044.705550] __schedule+0x336/0xe00
> [ 1044.706761] schedule+0x3d/0x90
> [ 1044.707891] io_schedule+0x16/0x40
> [ 1044.709073] __lock_page+0x126/0x180
> [ 1044.710272] ? page_cache_tree_insert+0x120/0x120
> [ 1044.711728] write_cache_pages+0x39a/0x6b0
> [ 1044.713077] ? xfs_map_blocks+0x5a0/0x5a0 [xfs]
> [ 1044.714499] ? xfs_vm_writepages+0x48/0xa0 [xfs]
> [ 1044.715944] xfs_vm_writepages+0x6b/0xa0 [xfs]
> [ 1044.717362] do_writepages+0x21/0x40
> [ 1044.718577] __writeback_single_inode+0x72/0x9d0
> [ 1044.719998] ? _raw_spin_unlock+0x27/0x40
> [ 1044.721308] writeback_sb_inodes+0x322/0x750
> [ 1044.722662] __writeback_inodes_wb+0x8c/0xc0
> [ 1044.724009] wb_writeback+0x3be/0x6e0
> [ 1044.725238] wb_workfn+0x146/0x7d0
> [ 1044.726413] ? process_one_work+0x194/0x760
> [ 1044.727736] process_one_work+0x22b/0x760
> [ 1044.729017] ? process_one_work+0x194/0x760
> [ 1044.730343] worker_thread+0x137/0x4b0
> [ 1044.731577] kthread+0x10f/0x150
> [ 1044.732702] ? process_one_work+0x760/0x760
> [ 1044.734021] ? kthread_create_on_node+0x70/0x70
> [ 1044.735415] ? do_syscall_64+0x195/0x200
> [ 1044.736684] ret_from_fork+0x31/0x40
> ----------
>
> Regarding "infinite too_many_isolated() loop" case
> ( http://lkml.kernel.org/r/201702212335.DJB30777.JOFMHSFtVLQOOF@xxxxxxxxxxxxxxxxxxx ),
> I used this patch for confirming the following things.
>
> (1) kswapd cannot make progress waiting for lock.
>
> ----------
> [ 1209.790966] MemAlloc: kswapd0(67) flags=0xa60840 switches=51139 uninterruptible
> [ 1209.799726] kswapd0 D10936 67 2 0x00000000
> [ 1209.807326] Call Trace:
> [ 1209.812581] __schedule+0x336/0xe00
> [ 1209.818599] schedule+0x3d/0x90
> [ 1209.823907] schedule_timeout+0x26a/0x510
> [ 1209.827218] ? trace_hardirqs_on+0xd/0x10
> [ 1209.830535] __down_common+0xfb/0x131
> [ 1209.833801] ? _xfs_buf_find+0x2cb/0xc10 [xfs]
> [ 1209.837372] __down+0x1d/0x1f
> [ 1209.840331] down+0x41/0x50
> [ 1209.843243] xfs_buf_lock+0x64/0x370 [xfs]
> [ 1209.846597] _xfs_buf_find+0x2cb/0xc10 [xfs]
> [ 1209.850031] ? _xfs_buf_find+0xa4/0xc10 [xfs]
> [ 1209.853514] xfs_buf_get_map+0x2a/0x480 [xfs]
> [ 1209.855831] xfs_buf_read_map+0x2c/0x400 [xfs]
> [ 1209.857388] ? free_debug_processing+0x27d/0x2af
> [ 1209.859037] xfs_trans_read_buf_map+0x186/0x830 [xfs]
> [ 1209.860707] xfs_read_agf+0xc8/0x2b0 [xfs]
> [ 1209.862184] xfs_alloc_read_agf+0x7a/0x300 [xfs]
> [ 1209.863728] ? xfs_alloc_space_available+0x7b/0x120 [xfs]
> [ 1209.865385] xfs_alloc_fix_freelist+0x3bc/0x490 [xfs]
> [ 1209.866974] ? __radix_tree_lookup+0x84/0xf0
> [ 1209.868374] ? xfs_perag_get+0x1a0/0x310 [xfs]
> [ 1209.869798] ? xfs_perag_get+0x5/0x310 [xfs]
> [ 1209.871288] xfs_alloc_vextent+0x161/0xda0 [xfs]
> [ 1209.872757] xfs_bmap_btalloc+0x46c/0x8b0 [xfs]
> [ 1209.874182] ? save_stack_trace+0x1b/0x20
> [ 1209.875542] xfs_bmap_alloc+0x17/0x30 [xfs]
> [ 1209.876847] xfs_bmapi_write+0x74e/0x11d0 [xfs]
> [ 1209.878190] xfs_iomap_write_allocate+0x199/0x3a0 [xfs]
> [ 1209.879632] xfs_map_blocks+0x2cc/0x5a0 [xfs]
> [ 1209.880909] xfs_do_writepage+0x215/0x920 [xfs]
> [ 1209.882255] ? clear_page_dirty_for_io+0xb4/0x310
> [ 1209.883598] xfs_vm_writepage+0x3b/0x70 [xfs]
> [ 1209.884841] pageout.isra.54+0x1a4/0x460
> [ 1209.886210] shrink_page_list+0xa86/0xcf0
> [ 1209.887441] shrink_inactive_list+0x1c5/0x660
> [ 1209.888682] shrink_node_memcg+0x535/0x7f0
> [ 1209.889975] ? mem_cgroup_iter+0x14d/0x720
> [ 1209.891197] shrink_node+0xe1/0x310
> [ 1209.892288] kswapd+0x362/0x9b0
> [ 1209.893308] kthread+0x10f/0x150
> [ 1209.894383] ? mem_cgroup_shrink_node+0x3b0/0x3b0
> [ 1209.895703] ? kthread_create_on_node+0x70/0x70
> [ 1209.896956] ret_from_fork+0x31/0x40
> ----------
>
> (2) Both GFP_IO and GFP_KERNEL allocations are stuck at
> too_many_isolated() loop.
>
> ----------
> [ 1209.898117] MemAlloc: systemd-journal(526) flags=0x400900 switches=33248 seq=121659 gfp=0x14201ca(GFP_HIGHUSER_MOVABLE|__GFP_COLD) order=0 delay=52772 uninterruptible
> [ 1209.902154] systemd-journal D11240 526 1 0x00000000
> [ 1209.903642] Call Trace:
> [ 1209.904574] __schedule+0x336/0xe00
> [ 1209.905734] schedule+0x3d/0x90
> [ 1209.906817] schedule_timeout+0x20d/0x510
> [ 1209.908025] ? prepare_to_wait+0x2b/0xc0
> [ 1209.909268] ? lock_timer_base+0xa0/0xa0
> [ 1209.910460] io_schedule_timeout+0x1e/0x50
> [ 1209.911681] congestion_wait+0x86/0x260
> [ 1209.912853] ? remove_wait_queue+0x60/0x60
> [ 1209.914115] shrink_inactive_list+0x5b4/0x660
> [ 1209.915385] ? __list_lru_count_one.isra.2+0x22/0x80
> [ 1209.916768] shrink_node_memcg+0x535/0x7f0
> [ 1209.918173] shrink_node+0xe1/0x310
> [ 1209.919288] do_try_to_free_pages+0xe1/0x300
> [ 1209.920548] try_to_free_pages+0x131/0x3f0
> [ 1209.921827] __alloc_pages_slowpath+0x3ec/0xd95
> [ 1209.923137] __alloc_pages_nodemask+0x3e4/0x460
> [ 1209.924454] ? __radix_tree_lookup+0x84/0xf0
> [ 1209.925790] alloc_pages_current+0x97/0x1b0
> [ 1209.927021] ? find_get_entry+0x5/0x300
> [ 1209.928189] __page_cache_alloc+0x15d/0x1a0
> [ 1209.929471] ? pagecache_get_page+0x2c/0x2b0
> [ 1209.930716] filemap_fault+0x4df/0x8b0
> [ 1209.931867] ? filemap_fault+0x373/0x8b0
> [ 1209.933111] ? xfs_ilock+0x22c/0x360 [xfs]
> [ 1209.934510] ? xfs_filemap_fault+0x64/0x1e0 [xfs]
> [ 1209.935857] ? down_read_nested+0x7b/0xc0
> [ 1209.937123] ? xfs_ilock+0x22c/0x360 [xfs]
> [ 1209.938373] xfs_filemap_fault+0x6c/0x1e0 [xfs]
> [ 1209.939691] __do_fault+0x1e/0xa0
> [ 1209.940807] ? _raw_spin_unlock+0x27/0x40
> [ 1209.942002] __handle_mm_fault+0xbb1/0xf40
> [ 1209.943228] ? mutex_unlock+0x12/0x20
> [ 1209.944410] ? devkmsg_read+0x15c/0x330
> [ 1209.945912] handle_mm_fault+0x16b/0x390
> [ 1209.947297] ? handle_mm_fault+0x49/0x390
> [ 1209.948868] __do_page_fault+0x24a/0x530
> [ 1209.950351] do_page_fault+0x30/0x80
> [ 1209.951615] page_fault+0x28/0x30
>
> [ 1210.538496] MemAlloc: kworker/3:0(6345) flags=0x4208860 switches=10134 seq=22 gfp=0x1400000(GFP_NOIO) order=0 delay=45953 uninterruptible
> [ 1210.541487] kworker/3:0 D12560 6345 2 0x00000080
> [ 1210.542991] Workqueue: events_freezable_power_ disk_events_workfn
> [ 1210.544577] Call Trace:
> [ 1210.545468] __schedule+0x336/0xe00
> [ 1210.546606] schedule+0x3d/0x90
> [ 1210.547616] schedule_timeout+0x20d/0x510
> [ 1210.548778] ? prepare_to_wait+0x2b/0xc0
> [ 1210.550013] ? lock_timer_base+0xa0/0xa0
> [ 1210.551208] io_schedule_timeout+0x1e/0x50
> [ 1210.552519] congestion_wait+0x86/0x260
> [ 1210.553650] ? remove_wait_queue+0x60/0x60
> [ 1210.554900] shrink_inactive_list+0x5b4/0x660
> [ 1210.556119] ? __list_lru_count_one.isra.2+0x22/0x80
> [ 1210.557447] shrink_node_memcg+0x535/0x7f0
> [ 1210.558714] shrink_node+0xe1/0x310
> [ 1210.559803] do_try_to_free_pages+0xe1/0x300
> [ 1210.561009] try_to_free_pages+0x131/0x3f0
> [ 1210.562250] __alloc_pages_slowpath+0x3ec/0xd95
> [ 1210.563506] __alloc_pages_nodemask+0x3e4/0x460
> [ 1210.564777] alloc_pages_current+0x97/0x1b0
> [ 1210.566017] bio_copy_kern+0xc9/0x180
> [ 1210.567116] blk_rq_map_kern+0x70/0x140
> [ 1210.568356] __scsi_execute.isra.22+0x13a/0x1e0
> [ 1210.569839] scsi_execute_req_flags+0x94/0x100
> [ 1210.571218] sr_check_events+0xbf/0x2b0 [sr_mod]
> [ 1210.572500] cdrom_check_events+0x18/0x30 [cdrom]
> [ 1210.573934] sr_block_check_events+0x2a/0x30 [sr_mod]
> [ 1210.575335] disk_check_events+0x60/0x170
> [ 1210.576509] disk_events_workfn+0x1c/0x20
> [ 1210.577744] process_one_work+0x22b/0x760
> [ 1210.578934] ? process_one_work+0x194/0x760
> [ 1210.580147] worker_thread+0x137/0x4b0
> [ 1210.581336] kthread+0x10f/0x150
> [ 1210.582365] ? process_one_work+0x760/0x760
> [ 1210.583603] ? kthread_create_on_node+0x70/0x70
> [ 1210.584961] ? do_syscall_64+0x6c/0x200
> [ 1210.586343] ret_from_fork+0x31/0x40
> ----------
>
> (3) Number of stalling threads does not decrease over time and
> number of out_of_memory() calls does not increase over time.
>
> ----------
> [ 1209.781787] MemAlloc-Info: stalling=32 dying=1 exiting=0 victim=1 oom_count=45896
> [ 1212.195351] MemAlloc-Info: stalling=32 dying=1 exiting=0 victim=1 oom_count=45896
> [ 1242.551629] MemAlloc-Info: stalling=36 dying=1 exiting=0 victim=1 oom_count=45896
> [ 1245.149165] MemAlloc-Info: stalling=36 dying=1 exiting=0 victim=1 oom_count=45896
> [ 1275.319189] MemAlloc-Info: stalling=40 dying=1 exiting=0 victim=1 oom_count=45896
> [ 1278.241813] MemAlloc-Info: stalling=40 dying=1 exiting=0 victim=1 oom_count=45896
> ----------
>
> Regarding [2], Alexander, Brian and Dave can explain it better than I. But
> I think that "check threads which cannot make progress" principle is same.
>
>
>
> > (top-posting repaired - please don't do that)
>
> Hmm, I don't see anything wrong with mail headers of replied one that can
> cause top-posting. I think something wired occurred outside of my control.
>
> Subject: Re: [PATCH v7] mm: Add memory allocation watchdog kernel thread.
> From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
> References: <1488244908-57586-1-git-send-email-penguin-kernel@xxxxxxxxxxxxxxxxxxx>
> In-Reply-To: <1488244908-57586-1-git-send-email-penguin-kernel@xxxxxxxxxxxxxxxxxxx>
> Message-Id: <201703091946.GDC21885.OQFFOtJHSOFVML@xxxxxxxxxxxxxxxxxxx>
> Date: Thu, 9 Mar 2017 19:46:14 +0900
>
> --
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