[pgpool-general: 7721] Re: Out of memory

[Tatsuo Ishii]

At this point I cannot judge whether the problem is caused by a pgpool
bug or client's resource request is too much.

Typical bug which requests too much memory allocation is not something
like this because 33947648 = 32MB memory request itself is not insane.

> Sep 24 09:14:10 pgpool pgpool[12650]: [426-2] 2021-09-24 09:14:10: pid
> 12650: DETAIL:  Failed on request of size 33947648.

(Please let us know what version of Pgpool-II you are using because
it's important information to identify any known bug).

In the mean time, however, I think 32MB memory request is not very
common in pgpool. One thing I wonder is, whether your application
issues SQL which requires large memory: e.g. very long SQL statement,
COPY for large data set. They will request large read/write buffer in
pgpool.

> We saw both, but pgpool aborting is way more common:
> Sep 24 09:14:10 pgpool pgpool[12650]: [426-1] 2021-09-24 09:14:10: pid
> 12650: ERROR:  out of memory
> Sep 24 09:14:10 pgpool pgpool[12650]: [426-2] 2021-09-24 09:14:10: pid
> 12650: DETAIL:  Failed on request of size 33947648.
> Sep 24 09:14:10 pgpool pgpool[12650]: [426-3] 2021-09-24 09:14:10: pid
> 12650: LOCATION:  mcxt.c:900
> 
> Here, two other ways we saw at the logs, but those just occurred once each:
> Sep 24 07:33:14 pgpool pgpool[5874]: [434-1] 2021-09-24 07:33:14: pid 5874:
> FATAL:  failed to fork a child
> Sep 24 07:33:14 pgpool pgpool[5874]: [434-2] 2021-09-24 07:33:14: pid 5874:
> DETAIL:  system call fork() failed with reason: Cannot allocate memory
> Sep 24 07:33:14 pgpool pgpool[5874]: [434-3] 2021-09-24 07:33:14: pid 5874:
> LOCATION:  pgpool_main.c:681
> 
> And:
> Sep 23 17:07:40 pgpool kernel: [157160.691518] pgpool invoked oom-killer:
> gfp_mask=0x24200ca, order=0, oom_score_adj=0
> Sep 23 17:07:40 pgpool kernel: [157160.691525] CPU: 1 PID: 1194 Comm:
> pgpool Not tainted 4.4.276 #1
> Sep 23 17:07:40 pgpool kernel: [157160.691527] Hardware name: VMware, Inc.
> VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00
> 12/12/2018
> Sep 23 17:07:40 pgpool kernel: [157160.691528]  0000000000000000
> ffff8803281cbae8 ffffffff81c930e7 ffff880420efe2c0
> Sep 23 17:07:40 pgpool kernel: [157160.691530]  ffff880420efe2c0
> ffff8803281cbb50 ffffffff81c8d9da ffff8803281cbb08
> Sep 23 17:07:40 pgpool kernel: [157160.691532]  ffffffff81133f1a
> ffff8803281cbb80 ffffffff81182eb0 ffff8800bba393c0
> Sep 23 17:07:40 pgpool kernel: [157160.691533] Call Trace:
> Sep 23 17:07:40 pgpool kernel: [157160.691540]  [<ffffffff81c930e7>]
> dump_stack+0x57/0x6d
> Sep 23 17:07:40 pgpool kernel: [157160.691542]  [<ffffffff81c8d9da>]
> dump_header.isra.9+0x54/0x1ae
> Sep 23 17:07:40 pgpool kernel: [157160.691547]  [<ffffffff81133f1a>] ?
> __delayacct_freepages_end+0x2a/0x30
> Sep 23 17:07:40 pgpool kernel: [157160.691553]  [<ffffffff81182eb0>] ?
> do_try_to_free_pages+0x350/0x3d0
> Sep 23 17:07:40 pgpool kernel: [157160.691556]  [<ffffffff811709f9>]
> oom_kill_process+0x209/0x3c0
> Sep 23 17:07:40 pgpool kernel: [157160.691558]  [<ffffffff81170eeb>]
> out_of_memory+0x2db/0x2f0
> Sep 23 17:07:40 pgpool kernel: [157160.691561]  [<ffffffff81176111>]
> __alloc_pages_nodemask+0xa81/0xae0
> Sep 23 17:07:40 pgpool kernel: [157160.691565]  [<ffffffff811ad2cd>]
> __read_swap_cache_async+0xdd/0x130
> Sep 23 17:07:40 pgpool kernel: [157160.691567]  [<ffffffff811ad337>]
> read_swap_cache_async+0x17/0x40
> Sep 23 17:07:40 pgpool kernel: [157160.691569]  [<ffffffff811ad455>]
> swapin_readahead+0xf5/0x190
> Sep 23 17:07:40 pgpool kernel: [157160.691571]  [<ffffffff8119ce3f>]
> handle_mm_fault+0xf3f/0x15e0
> Sep 23 17:07:40 pgpool kernel: [157160.691574]  [<ffffffff81c9d4e2>] ?
> __schedule+0x272/0x770
> Sep 23 17:07:40 pgpool kernel: [157160.691576]  [<ffffffff8104e241>]
> __do_page_fault+0x161/0x370
> Sep 23 17:07:40 pgpool kernel: [157160.691577]  [<ffffffff8104e49c>]
> do_page_fault+0xc/0x10
> Sep 23 17:07:40 pgpool kernel: [157160.691579]  [<ffffffff81ca3782>]
> page_fault+0x22/0x30
> Sep 23 17:07:40 pgpool kernel: [157160.691581] Mem-Info:
> Sep 23 17:07:40 pgpool kernel: [157160.691584] active_anon:3564689
> inactive_anon:445592 isolated_anon:0
> Sep 23 17:07:40 pgpool kernel: [157160.691584]  active_file:462
> inactive_file:44 isolated_file:0
> Sep 23 17:07:40 pgpool kernel: [157160.691584]  unevictable:0 dirty:2
> writeback:2212 unstable:0
> Sep 23 17:07:40 pgpool kernel: [157160.691584]  slab_reclaimable:3433
> slab_unreclaimable:5859
> Sep 23 17:07:40 pgpool kernel: [157160.691584]  mapped:989 shmem:2607
> pagetables:16367 bounce:0
> Sep 23 17:07:40 pgpool kernel: [157160.691584]  free:51773 free_pcp:189
> free_cma:0
> Sep 23 17:07:40 pgpool kernel: [157160.691589] DMA free:15904kB min:128kB
> low:160kB high:192kB active_anon:0kB inactive_anon:0kB active_file:0kB
> inactive_file:0kB unevictable:0kB isolated(anon):0kB isolated(file):0kB
> present:15992kB managed:15904kB mlocked:0kB dirty:0kB writeback:0kB
> mapped:0kB shmem:0kB slab_reclaimable:0kB slab_unreclaimable:0kB
> kernel_stack:0kB pagetables:0kB unstable:0kB bounce:0kB free_pcp:0kB
> local_pcp:0kB free_cma:0kB writeback_tmp:0kB pages_scanned:0
> all_unreclaimable? yes
> Sep 23 17:07:40 pgpool kernel: [157160.691590] lowmem_reserve[]: 0 2960
> 15991 15991
> Sep 23 17:07:40 pgpool kernel: [157160.691596] DMA32 free:77080kB
> min:25000kB low:31248kB high:37500kB active_anon:2352676kB
> inactive_anon:590536kB active_file:472kB inactive_file:140kB
> unevictable:0kB isolated(anon):0kB isolated(file):0kB present:3129216kB
> managed:3043556kB mlocked:0kB dirty:0kB writeback:4144kB mapped:1140kB
> shmem:3568kB slab_reclaimable:1028kB slab_unreclaimable:3004kB
> kernel_stack:816kB pagetables:10988kB unstable:0kB bounce:0kB
> free_pcp:312kB local_pcp:196kB free_cma:0kB writeback_tmp:0kB
> pages_scanned:4292 all_unreclaimable? yes
> Sep 23 17:07:40 pgpool kernel: [157160.691597] lowmem_reserve[]: 0 0 13031
> 13031
> Sep 23 17:07:40 pgpool kernel: [157160.691601] Normal free:114108kB
> min:110032kB low:137540kB high:165048kB active_anon:11906080kB
> inactive_anon:1191832kB active_file:1376kB inactive_file:36kB
> unevictable:0kB isolated(anon):0kB isolated(file):0kB present:13631488kB
> managed:13343784kB mlocked:0kB dirty:8kB writeback:4704kB mapped:2816kB
> shmem:6860kB slab_reclaimable:12704kB slab_unreclaimable:20432kB
> kernel_stack:4848kB pagetables:54480kB unstable:0kB bounce:0kB
> free_pcp:444kB local_pcp:196kB free_cma:0kB writeback_tmp:0kB
> pages_scanned:105664 all_unreclaimable? yes
> Sep 23 17:07:40 pgpool kernel: [157160.691602] lowmem_reserve[]: 0 0 0 0
> Sep 23 17:07:40 pgpool kernel: [157160.691603] DMA: 0*4kB 0*8kB 0*16kB
> 1*32kB (U) 2*64kB (U) 1*128kB (U) 1*256kB (U) 0*512kB 1*1024kB (U) 1*2048kB
> (U) 3*4096kB (M) = 15904kB
> Sep 23 17:07:40 pgpool kernel: [157160.691610] DMA32: 48*4kB (ME) 63*8kB
> (ME) 62*16kB (E) 46*32kB (UME) 35*64kB (UME) 26*128kB (UME) 25*256kB (UME)
> 61*512kB (UME) 28*1024kB (UME) 1*2048kB (M) 0*4096kB = 77080kB
> Sep 23 17:07:40 pgpool kernel: [157160.691616] Normal: 165*4kB (MEH)
> 317*8kB (UMEH) 442*16kB (UMEH) 289*32kB (UMEH) 162*64kB (UMEH) 121*128kB
> (UMEH) 74*256kB (UMEH) 33*512kB (UMEH) 24*1024kB (ME) 0*2048kB 2*4096kB (M)
> = 113980kB
> Sep 23 17:07:40 pgpool kernel: [157160.691623] 5552 total pagecache pages
> Sep 23 17:07:40 pgpool kernel: [157160.691624] 2355 pages in swap cache
> Sep 23 17:07:40 pgpool kernel: [157160.691625] Swap cache stats: add
> 5385308, delete 5382953, find 1159094/1325033
> Sep 23 17:07:40 pgpool kernel: [157160.691626] Free swap  = 0kB
> Sep 23 17:07:40 pgpool kernel: [157160.691626] Total swap = 4194300kB
> Sep 23 17:07:40 pgpool kernel: [157160.691627] 4194174 pages RAM
> Sep 23 17:07:40 pgpool kernel: [157160.691628] 0 pages HighMem/MovableOnly
> Sep 23 17:07:40 pgpool kernel: [157160.691628] 93363 pages reserved
> Sep 23 17:07:40 pgpool kernel: [157160.691989] Out of memory: Kill process
> 8975 (pgpool) score 7 or sacrifice child
> Sep 23 17:07:40 pgpool kernel: [157160.691995] Killed process 8975 (pgpool)
> total-vm:337504kB, anon-rss:166824kB, file-rss:1920kB
> 
> 
> 
> On Mon, Sep 27, 2021 at 1:22 AM Tatsuo Ishii <ishii at sraoss.co.jp> wrote:
> 
>> Hi,
>>
>> > Hello,
>> >
>> > Our pgpool is consuming A LOT of memory and frequently dies with: Out of
>> > memory error.
>> >
>> > We have 2 backends, 1 master and 1 slave. Here some config:
>> > num_init_children = 150
>> > max_pool = 1
>> > child_life_time = 300
>> > child_max_connections = 1
>> > connection_life_time = 0
>> > client_idle_limit = 0
>> > connection_cache = on
>> > load_balance_mode = on
>> > memory_cache_enabled = off
>> >
>> > RAM: 16Gb
>> >
>> > Does anyone have a clue what's going on?
>> >
>> > Thank you.
>>
>> Is that OOM killer or pgpool itself aborted with an out of memory
>> error?  If latter, can you share the pgpool log?
>> --
>> Tatsuo Ishii
>> SRA OSS, Inc. Japan
>> English: http://www.sraoss.co.jp/index_en.php
>> Japanese:http://www.sraoss.co.jp
>>
> 
> 
> -- 
> Luiz Fernando Pasqual S. Souza
> mail: luiz at pasquall.com