Re: Possible mem cgroup bug in kernels between 4.18.0 and 5.3-rc1.

[Masoud Sharbiani]

> On Aug 2, 2019, at 12:40 AM, Michal Hocko <mhocko@xxxxxxxxxx> wrote:
> 
> On Thu 01-08-19 11:04:14, Masoud Sharbiani wrote:
>> Hey folks,
>> Iâve come across an issue that affects most of 4.19, 4.20 and 5.2 linux-stable kernels that has only been fixed in 5.3-rc1.
>> It was introduced by
>> 
>> 29ef680 memcg, oom: move out_of_memory back to the charge path 
> 
> This commit shouldn't really change the OOM behavior for your particular
> test case. It would have changed MAP_POPULATE behavior but your usage is
> triggering the standard page fault path. The only difference with
> 29ef680 is that the OOM killer is invoked during the charge path rather
> than on the way out of the page fault.
> 
> Anyway, I tried to run your test case in a loop and leaker always ends
> up being killed as expected with 5.2. See the below oom report. There
> must be something else going on. How much swap do you have on your
> system?

I do not have swap defined. 
-m


> 
> [337533.314245] leaker invoked oom-killer: gfp_mask=0x100cca(GFP_HIGHUSER_MOVABLE), order=0, oom_score_adj=0
> [337533.314250] CPU: 3 PID: 23793 Comm: leaker Not tainted 5.2.0-rc7 #54
> [337533.314251] Hardware name: Dell Inc. Latitude E7470/0T6HHJ, BIOS 1.5.3 04/18/2016
> [337533.314252] Call Trace:
> [337533.314258]  dump_stack+0x67/0x8e
> [337533.314262]  dump_header+0x51/0x2e9
> [337533.314265]  ? preempt_count_sub+0xc6/0xd2
> [337533.314267]  ? _raw_spin_unlock_irqrestore+0x2c/0x3e
> [337533.314269]  oom_kill_process+0x90/0x11d
> [337533.314271]  out_of_memory+0x25c/0x26f
> [337533.314273]  mem_cgroup_out_of_memory+0x8a/0xa6
> [337533.314276]  try_charge+0x1d0/0x782
> [337533.314278]  ? preempt_count_sub+0xc6/0xd2
> [337533.314280]  mem_cgroup_try_charge+0x1a1/0x207
> [337533.314282]  __add_to_page_cache_locked+0xf9/0x2dd
> [337533.314285]  ? memcg_drain_all_list_lrus+0x125/0x125
> [337533.314286]  add_to_page_cache_lru+0x3c/0x96
> [337533.314288]  pagecache_get_page.part.7+0x1d6/0x240
> [337533.314290]  filemap_fault+0x267/0x54a
> [337533.314292]  ext4_filemap_fault+0x2d/0x41
> [337533.314294]  ? ext4_page_mkwrite+0x3cd/0x3cd
> [337533.314296]  __do_fault+0x47/0xa7
> [337533.314297]  __handle_mm_fault+0xaaa/0xf9d
> [337533.314300]  handle_mm_fault+0x174/0x1c3
> [337533.314303]  __do_page_fault+0x309/0x412
> [337533.314305]  do_page_fault+0x10b/0x131
> [337533.314307]  ? page_fault+0x8/0x30
> [337533.314309]  page_fault+0x1e/0x30
> [337533.314311] RIP: 0033:0x55a806ef8503
> [337533.314313] Code: 48 89 c6 48 8d 3d 28 0c 00 00 b8 00 00 00 00 e8 73 fb ff ff c7 45 ec 00 00 00 00 eb 36 8b 45 ec 48 63 d0 48 8b 45 c8 48 01 d0 <0f> b6 00 0f be c0 01 45 e4 8b 45 ec 25 ff 0f 00 00 85 c0 75 10 8b
> [337533.314314] RSP: 002b:00007ffcf6734730 EFLAGS: 00010206
> [337533.314316] RAX: 00007f2228f74000 RBX: 0000000000000000 RCX: 0000000000000000
> [337533.314317] RDX: 0000000000487000 RSI: 000055a806efc260 RDI: 0000000000000000
> [337533.314318] RBP: 00007ffcf6735780 R08: 0000000000000000 R09: 00007ffcf67345fc
> [337533.314319] R10: 0000000000000000 R11: 0000000000000246 R12: 000055a806ef8120
> [337533.314320] R13: 00007ffcf6735860 R14: 0000000000000000 R15: 0000000000000000
> [337533.314322] memory: usage 524288kB, limit 524288kB, failcnt 1240247
> [337533.314323] memory+swap: usage 2592556kB, limit 9007199254740988kB, failcnt 0
> [337533.314324] kmem: usage 7260kB, limit 9007199254740988kB, failcnt 0
> [337533.314325] Memory cgroup stats for /leaker: cache:80KB rss:516948KB rss_huge:0KB shmem:0KB mapped_file:0KB dirty:0KB writeback:0KB swap:2068268KB inactive_anon:258520KB active_anon:258412KB inactive_file:32KB active_file:12KB unevictable:0KB
> [337533.314332] Tasks state (memory values in pages):
> [337533.314333] [  pid  ]   uid  tgid total_vm      rss pgtables_bytes swapents oom_score_adj name
> [337533.314404] [  23777]     0 23777      596      400    36864        4             0 sh
> [337533.314407] [  23793]     0 23793   655928   126942  5226496   519670             0 leaker
> [337533.314408] oom-kill:constraint=CONSTRAINT_MEMCG,nodemask=(null),oom_memcg=/leaker,task_memcg=/leaker,task=leaker,pid=23793,uid=0
> [337533.314412] Memory cgroup out of memory: Killed process 23793 (leaker) total-vm:2623712kB, anon-rss:506500kB, file-rss:1268kB, shmem-rss:0kB
> [337533.418036] oom_reaper: reaped process 23793 (leaker), now anon-rss:0kB, file-rss:0kB, shmem-rss:0kB
> -- 
> Michal Hocko
> SUSE Labs