[pgpool-general: 7726] Re: Out of memory

Luiz Pasqual luiz at pasquall.com
Tue Sep 28 22:02:04 JST 2021 

I did those tests:
4.0.15 is running fine, when I upgraded to 4.1.8 it started to consume a
lot of memory.

On Tue, Sep 28, 2021 at 8:30 AM Tatsuo Ishii <ishii at sraoss.co.jp> wrote:

> Ok. 4.2.1 consumes 10 times of memory than 3.7.3 (maybe 5, not 10
> because in your test connections of 4.2.1 is twice of 3.7.3).
>
> Next thing I need to know is, from which version of pgpool started to
> consume lot of memory.  Is it possible to run the same test against
> 4.0 and 4.1? Ideally from which version, including minor version will
> be a lot helpful. I wish I could the test myself but I don't know to
> do it on my environment.
>
> > Sure.
> >
> > On 3.7.3:
> > $ ps aux | grep pgpool | awk '{sum += $6}END{print sum}'
> > 896752
> >
> > On 4.2.1:
> > $ ps aux | grep pgpool | awk '{sum += $6}END{print sum}'
> > 9969280
> >
> >
> > On Mon, Sep 27, 2021 at 11:41 PM Tatsuo Ishii <ishii at sraoss.co.jp>
> wrote:
> >
> >> Ok, let's see how much RSS pgpool consume in total. Can you share the
> >> result of the command for both pgpool 4.2 and 3.7?
> >>
> >> ps aux | grep pgpool | awk '{sum += $6}END{print sum}'
> >>
> >> > I see.
> >> >
> >> > The problem is, the OOM happens when all RAM is already compromised by
> >> > pgpool (all 16Gb of RAM is dedicated to pgpool), so any common request
> >> will
> >> > die anyway.
> >> >
> >> > It happens on versions: 4.2.5 and 4.2.1. Now, I'm running the same
> >> > application on 3.7.3 and it's running great.
> >> >
> >> > I don't know if it helps, but just to demonstrate the amount of RAM is
> >> > necessary to run a few connections I created another VM, and
> comparing:
> >> >
> >> > 62 active connections running on 4.2.1 (same behaviour on 4.2.5):
> >> > $ vmstat -a -SM
> >> > procs -----------memory---------- ---swap-- -----io---- -system--
> >> > ------cpu-----
> >> >  r  b   swpd   free  inact active   si   so    bi    bo   in   cs us
> sy
> >> id
> >> > wa st
> >> >  0  0      0   4829    173  10772    0    0     2     1   68   56  1
> 1
> >> 99
> >> >  0  0
> >> >
> >> > 31 active connections running on 3.7.3:
> >> > $ vmstat -a -SM
> >> > procs -----------memory---------- ---swap-- -----io---- -system--
> >> > ------cpu-----
> >> >  r  b   swpd   free  inact active   si   so    bi    bo   in   cs us
> sy
> >> id
> >> > wa st
> >> >  0  0      0  15174     73    635    0    0     1     1   76    3  0
> 0
> >> 100
> >> >  0  0
> >> >
> >> > Both are running basically the same application.
> >> >
> >> > Seeing the RAM consumption of 3.7.3, it does not seem to be receiving
> >> such
> >> > a big requests. Is there a way to track it down?
> >> >
> >> >
> >> >
> >> > On Mon, Sep 27, 2021 at 9:07 AM Tatsuo Ishii <ishii at sraoss.co.jp>
> wrote:
> >> >
> >> >> 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
> >> >>
> >> >
> >> >
> >> > --
> >> > Luiz Fernando Pasqual S. Souza
> >> > mail: luiz at pasquall.com
> >>
> >
> >
> > --
> > Luiz Fernando Pasqual S. Souza
> > mail: luiz at pasquall.com
>


-- 
Luiz Fernando Pasqual S. Souza
mail: luiz at pasquall.com
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