On 11/22/2016 02:58 PM, E V wrote: > System OOM'd several times last night with 4.8.10, I attached the > page_owner output from a morning cat ~8 hours after OOM's to the > bugzilla case, split and compressed to fit under the 5M attachment > limit. Let me know if you need anything else. Looks like for some reason, the stack saving produces garbage stacks that only repeat save_stack_trace and save_stack functions :/ But judging from gfp flags and page flags, most pages seem to be allocated with: mask 0x2400840(GFP_NOFS|__GFP_NOFAIL) and page flags: 0x20000000000006c(referenced|uptodate|lru|active) or 0x20000000000016c(referenced|uptodate|lru|active|owner_priv_1) or 0x20000000000086c(referenced|uptodate|lru|active|private) While GFP_HIGHUSER_MOVABLE (which I would expect on lru) are less frequent. Example: > grep GFP_NOFS page_owner_after_af | wc -l 973596 > grep GFP_HIGHUSER_MOVABLE page_owner_after_af | wc -l 158879 > grep GFP_NOFAIL page_owner_after_af | wc -l 971442 grepping for btrfs shows that at least some stacks for NOFS/NOFAIL pages imply it: clear_state_bit+0x135/0x1c0 [btrfs] or add_delayed_tree_ref+0xbf/0x170 [btrfs] or __btrfs_map_block+0x6a8/0x1200 [btrfs] or btrfs_buffer_uptodate+0x48/0x70 [btrfs] or btrfs_set_path_blocking+0x34/0x60 [btrfs] and some more variants. So looks like the pages contain btrfs metadata, are on file lru and from previous checks of /proc/kpagecount we know that they most likely have page_count() == 0 but are not freed. Could btrfs guys provide some insight here? > On Fri, Nov 18, 2016 at 10:02 AM, E V <eliventer@xxxxxxxxx> wrote: >> Yes, the short window between the stalls and the panic makes it >> difficult to manually check much. I could setup a cron every 5 minutes >> or so if you want. Also, I see the OOM's in 4.8, but it has yet to >> panic on me. Where as 4.9rc has panic'd both times I've booted it, so >> depending on what you want to look at it might be easier to >> investigate on 4.8. Let me know, I can turn on a couple of the DEBUG >> config's and build a new 4.8.8. Never looked into a netconsole or >> serial console. I think just getting the system to use a higher res >> console would be an improvement, but the OOM's seemed to be the root >> cause of the panic so I haven't spent any time looking into that as of >> yet, >> >> Thanks, >> -Eli >> >> On Fri, Nov 18, 2016 at 6:54 AM, Tetsuo Handa >> <penguin-kernel@xxxxxxxxxxxxxxxxxxx> wrote: >>> On 2016/11/18 6:49, Vlastimil Babka wrote: >>>> On 11/16/2016 02:39 PM, E V wrote: >>>>> System panic'd overnight running 4.9rc5 & rsync. Attached a photo of >>>>> the stack trace, and the 38 call traces in a 2 minute window shortly >>>>> before, to the bugzilla case for those not on it's e-mail list: >>>>> >>>>> https://bugzilla.kernel.org/show_bug.cgi?id=186671 >>>> >>>> The panic screenshot has only the last part, but the end marker says >>>> it's OOM with no killable processes. The DEBUG_VM config thus didn't >>>> trigger anything, and still there's tons of pagecache, mostly clean, >>>> that's not being reclaimed. >>>> >>>> Could you now try this? >>>> - enable CONFIG_PAGE_OWNER >>>> - boot with kernel option: page_owner=on >>>> - after the first oom, "cat /sys/kernel/debug/page_owner > file" >>>> - provide the file (compressed, it will be quite large) >>> >>> Excuse me for a noise, but do we really need to do >>> "cat /sys/kernel/debug/page_owner > file" after the first OOM killer >>> invocation? I worry that it might be too difficult to do. >>> Shouldn't we rather do "cat /sys/kernel/debug/page_owner > file" >>> hourly and compare tendency between the latest one and previous one? >>> >>> This system has swap, and /var/log/messages before panic >>> reports that swapin was stalling at memory allocation. >>> >>> ---------------------------------------- >>> [130346.262510] dsm_sa_datamgrd: page allocation stalls for 52400ms, order:0, mode:0x24200ca(GFP_HIGHUSER_MOVABLE) >>> [130346.262572] CPU: 1 PID: 3622 Comm: dsm_sa_datamgrd Tainted: G W I 4.9.0-rc5 #2 >>> [130346.262662] 0000000000000000 ffffffff8129ba69 ffffffff8170e4c8 ffffc90003ccb8d8 >>> [130346.262714] ffffffff8113449f 024200ca1ca11b40 ffffffff8170e4c8 ffffc90003ccb880 >>> [130346.262765] ffffffff00000010 ffffc90003ccb8e8 ffffc90003ccb898 ffff88041f226e80 >>> [130346.262817] Call Trace: >>> [130346.262843] [<ffffffff8129ba69>] ? dump_stack+0x46/0x5d >>> [130346.262872] [<ffffffff8113449f>] ? warn_alloc+0x11f/0x140 >>> [130346.262899] [<ffffffff81134d7b>] ? __alloc_pages_slowpath+0x84b/0xa80 >>> [130346.262929] [<ffffffff81135260>] ? __alloc_pages_nodemask+0x2b0/0x2f0 >>> [130346.262960] [<ffffffff8117f1be>] ? alloc_pages_vma+0xbe/0x260 >>> [130346.262989] [<ffffffff8112af02>] ? pagecache_get_page+0x22/0x280 >>> [130346.263019] [<ffffffff81171b68>] ? __read_swap_cache_async+0x118/0x1a0 >>> [130346.263048] [<ffffffff81171bff>] ? read_swap_cache_async+0xf/0x30 >>> [130346.263077] [<ffffffff81171d8e>] ? swapin_readahead+0x16e/0x1c0 >>> [130346.263106] [<ffffffff812a0f6e>] ? radix_tree_lookup_slot+0xe/0x20 >>> [130346.263135] [<ffffffff8112ac84>] ? find_get_entry+0x14/0x130 >>> [130346.263162] [<ffffffff8112af02>] ? pagecache_get_page+0x22/0x280 >>> [130346.263193] [<ffffffff8115cb1f>] ? do_swap_page+0x44f/0x5f0 >>> [130346.263220] [<ffffffff812a0f02>] ? __radix_tree_lookup+0x62/0xc0 >>> [130346.263249] [<ffffffff8115e91a>] ? handle_mm_fault+0x66a/0xf00 >>> [130346.263277] [<ffffffff8112ac84>] ? find_get_entry+0x14/0x130 >>> [130346.263305] [<ffffffff8104a245>] ? __do_page_fault+0x1c5/0x490 >>> [130346.263336] [<ffffffff8150e322>] ? page_fault+0x22/0x30 >>> [130346.263364] [<ffffffff812a7cac>] ? copy_user_generic_string+0x2c/0x40 >>> [130346.263395] [<ffffffff811adc1d>] ? set_fd_set+0x1d/0x30 >>> [130346.263422] [<ffffffff811ae905>] ? core_sys_select+0x1a5/0x260 >>> [130346.263450] [<ffffffff811a913a>] ? getname_flags+0x6a/0x1e0 >>> [130346.263479] [<ffffffff8119ef25>] ? cp_new_stat+0x115/0x130 >>> [130346.263509] [<ffffffff810bf01f>] ? ktime_get_ts64+0x3f/0xf0 >>> [130346.263537] [<ffffffff811aea65>] ? SyS_select+0xa5/0xe0 >>> [130346.263564] [<ffffffff8150c6a0>] ? entry_SYSCALL_64_fastpath+0x13/0x94 >>> ---------------------------------------- >>> >>> Under such situation, trying to login and execute /bin/cat could take minutes. >>> Also, writing to btrfs and ext4 seems to be stalling. The btrfs one is a >>> situation where WQ_MEM_RECLAIM kernel workqueue is unable to make progress. >>> >>> ---------------------------------------- >>> [130420.008231] kworker/u34:21: page allocation stalls for 35028ms, order:0, mode:0x2400840(GFP_NOFS|__GFP_NOFAIL) >>> [130420.008287] CPU: 5 PID: 24286 Comm: kworker/u34:21 Tainted: G W I 4.9.0-rc5 #2 >>> [130420.008401] Workqueue: btrfs-extent-refs btrfs_extent_refs_helper [btrfs] >>> [130420.008432] 0000000000000000 ffffffff8129ba69 ffffffff8170e4c8 ffffc900087836a0 >>> [130420.008483] ffffffff8113449f 024008401e3f1b40 ffffffff8170e4c8 ffffc90008783648 >>> [130420.008534] ffffffff00000010 ffffc900087836b0 ffffc90008783660 ffff88041ecc4340 >>> [130420.008586] Call Trace: >>> [130420.008611] [<ffffffff8129ba69>] ? dump_stack+0x46/0x5d >>> [130420.008640] [<ffffffff8113449f>] ? warn_alloc+0x11f/0x140 >>> [130420.008667] [<ffffffff81134d7b>] ? __alloc_pages_slowpath+0x84b/0xa80 >>> [130420.008707] [<ffffffffa020c432>] ? search_bitmap+0xc2/0x140 [btrfs] >>> [130420.008736] [<ffffffff81135260>] ? __alloc_pages_nodemask+0x2b0/0x2f0 >>> [130420.008766] [<ffffffff8117dbda>] ? alloc_pages_current+0x8a/0x110 >>> [130420.008796] [<ffffffff8112afcc>] ? pagecache_get_page+0xec/0x280 >>> [130420.008836] [<ffffffffa01e9aa8>] ? alloc_extent_buffer+0x108/0x430 [btrfs] >>> [130420.008875] [<ffffffffa01b4108>] ? btrfs_alloc_tree_block+0x118/0x4d0 [btrfs] >>> [130420.008927] [<ffffffffa019ae38>] ? __btrfs_cow_block+0x148/0x5d0 [btrfs] >>> [130420.008964] [<ffffffffa019b464>] ? btrfs_cow_block+0x114/0x1d0 [btrfs] >>> [130420.009001] [<ffffffffa019f1d6>] ? btrfs_search_slot+0x206/0xa40 [btrfs] >>> [130420.009039] [<ffffffffa01a6089>] ? lookup_inline_extent_backref+0xd9/0x620 [btrfs] >>> [130420.009095] [<ffffffffa01e4e74>] ? set_extent_bit+0x24/0x30 [btrfs] >>> [130420.009124] [<ffffffff8118567f>] ? kmem_cache_alloc+0x17f/0x1b0 >>> [130420.009161] [<ffffffffa01a7b1f>] ? __btrfs_free_extent.isra.69+0xef/0xd10 [btrfs] >>> [130420.009215] [<ffffffffa0214346>] ? btrfs_merge_delayed_refs+0x56/0x6f0 [btrfs] >>> [130420.009269] [<ffffffffa01ac545>] ? __btrfs_run_delayed_refs+0x745/0x1320 [btrfs] >>> [130420.009314] [<ffffffff810801ef>] ? ttwu_do_wakeup+0xf/0xe0 >>> [130420.009351] [<ffffffffa01b0000>] ? btrfs_run_delayed_refs+0x90/0x2b0 [btrfs] >>> [130420.009404] [<ffffffffa01b02a4>] ? delayed_ref_async_start+0x84/0xa0 [btrfs] >>> [130420.009459] [<ffffffffa01f82a3>] ? normal_work_helper+0xc3/0x2f0 [btrfs] >>> [130420.009490] [<ffffffff81071efb>] ? process_one_work+0x14b/0x400 >>> [130420.009518] [<ffffffff8107251d>] ? worker_thread+0x5d/0x470 >>> [130420.009546] [<ffffffff810724c0>] ? rescuer_thread+0x310/0x310 >>> [130420.009573] [<ffffffff8105ed54>] ? do_group_exit+0x34/0xb0 >>> [130420.009601] [<ffffffff810772bb>] ? kthread+0xcb/0xf0 >>> [130420.009627] [<ffffffff810771f0>] ? kthread_park+0x50/0x50 >>> [130420.009655] [<ffffffff8150c8d2>] ? ret_from_fork+0x22/0x30 >>> ---------------------------------------- >>> >>> ---------------------------------------- >>> [130438.436025] jbd2/dm-0-8: page allocation stalls for 10492ms, order:0, mode:0x2420848(GFP_NOFS|__GFP_NOFAIL|__GFP_HARDWALL|__GFP_MOVABLE) >>> [130438.436095] CPU: 2 PID: 1838 Comm: jbd2/dm-0-8 Tainted: G W I 4.9.0-rc5 #2 >>> [130438.436184] 0000000000000000 ffffffff8129ba69 ffffffff8170e4c8 ffffc90003e13728 >>> [130438.436237] ffffffff8113449f 0242084800000200 ffffffff8170e4c8 ffffc90003e136d0 >>> [130438.436289] 0000000100000010 ffffc90003e13738 ffffc90003e136e8 0000000000000001 >>> [130438.436340] Call Trace: >>> [130438.436368] [<ffffffff8129ba69>] ? dump_stack+0x46/0x5d >>> [130438.436399] [<ffffffff8113449f>] ? warn_alloc+0x11f/0x140 >>> [130438.436426] [<ffffffff81134d7b>] ? __alloc_pages_slowpath+0x84b/0xa80 >>> [130438.436455] [<ffffffff81135260>] ? __alloc_pages_nodemask+0x2b0/0x2f0 >>> [130438.436488] [<ffffffff8117dbda>] ? alloc_pages_current+0x8a/0x110 >>> [130438.436518] [<ffffffff8112afcc>] ? pagecache_get_page+0xec/0x280 >>> [130438.436549] [<ffffffff811cc051>] ? __getblk_gfp+0xf1/0x320 >>> [130438.436593] [<ffffffffa02bc774>] ? ext4_get_branch+0xa4/0x130 [ext4] >>> [130438.436628] [<ffffffffa02bd24b>] ? ext4_ind_map_blocks+0xcb/0xb10 [ext4] >>> [130438.436658] [<ffffffff8108807e>] ? update_curr+0x7e/0x100 >>> [130438.436688] [<ffffffff810bfe61>] ? ktime_get+0x31/0xa0 >>> [130438.436716] [<ffffffff8112e329>] ? mempool_alloc+0x59/0x170 >>> [130438.436743] [<ffffffff8108807e>] ? update_curr+0x7e/0x100 >>> [130438.436775] [<ffffffffa0280813>] ? ext4_map_blocks+0x3c3/0x630 [ext4] >>> [130438.436808] [<ffffffffa0280ae4>] ? _ext4_get_block+0x64/0xc0 [ext4] >>> [130438.436838] [<ffffffff811ca6a7>] ? generic_block_bmap+0x37/0x50 >>> [130438.436870] [<ffffffffa027fc57>] ? ext4_bmap+0x37/0xd0 [ext4] >>> [130438.436901] [<ffffffffa008a5e1>] ? jbd2_journal_bmap+0x21/0x70 [jbd2] >>> [130438.436932] [<ffffffffa008a6be>] ? jbd2_journal_get_descriptor_buffer+0x1e/0xc0 [jbd2] >>> [130438.436979] [<ffffffffa0086aa8>] ? jbd2_journal_write_revoke_records+0x198/0x2b0 [jbd2] >>> [130438.437026] [<ffffffffa0083236>] ? jbd2_journal_commit_transaction+0x5d6/0x19f0 [jbd2] >>> [130438.437071] [<ffffffff8108807e>] ? update_curr+0x7e/0x100 >>> [130438.437099] [<ffffffff8108c8fc>] ? dequeue_task_fair+0x5dc/0x1120 >>> [130438.437127] [<ffffffff8108f61c>] ? pick_next_task_fair+0x12c/0x420 >>> [130438.437157] [<ffffffffa00884e8>] ? kjournald2+0xc8/0x250 [jbd2] >>> [130438.437187] [<ffffffff810948e0>] ? wake_up_atomic_t+0x30/0x30 >>> [130438.437216] [<ffffffffa0088420>] ? commit_timeout+0x10/0x10 [jbd2] >>> [130438.437247] [<ffffffff810772bb>] ? kthread+0xcb/0xf0 >>> [130438.437273] [<ffffffff810771f0>] ? kthread_park+0x50/0x50 >>> [130438.437304] [<ffffffff8150c8d2>] ? ret_from_fork+0x22/0x30 >>> ---------------------------------------- >>> >>> Under such situation, saving /sys/kernel/debug/page_owner to a file might >>> be impossible. And, once the stalling started, it took less than 5 minutes >>> before the kernel panics due to "Out of memory and no killable process". >>> This could happen when E V is offline. >>> >>> Since rsyslogd is likely be killed by the OOM killer for situations like >>> this, E V might want to try serial console or netconsole for saving kernel >>> messages reliably. >>> >>> I don't know what we will find by analyzing /sys/kernel/debug/page_owner , >>> but if something is wrong, can't we try whether >>> "echo 3 > /proc/sys/vm/drop_caches" before the stalling starts helps. >>> >>> I guess that this problem became visible by OOM detection rework which >>> went to Linux 4.7. I don't know what "free_pcp:0kB local_pcp:0kB" means >>> (get_page_from_freelist() for any order is failng?), but in general I think >>> this /var/log/messages showed that free_pcp: and local_pcp: remains small. >>> -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. 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