Re: Autovacuum running out of memory

From: Jason Lustig <lustig(at)brandeis(dot)edu>
To: Richard Huxton <dev(at)archonet(dot)com>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Autovacuum running out of memory
Date: 2007-10-16 14:14:30
Message-ID: A727D61D-09FC-4174-B120-18D5C3D5D475@brandeis.edu
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I ran "ulimit -a" for the postgres user, and here's what I got:

core file size (blocks, -c) 200000
data seg size (kbytes, -d) 200000
max nice (-e) 0
file size (blocks, -f) unlimited
pending signals (-i) 32635
max locked memory (kbytes, -l) 32
max memory size (kbytes, -m) 200000
open files (-n) 100
pipe size (512 bytes, -p) 8
POSIX message queues (bytes, -q) 819200
max rt priority (-r) 0
stack size (kbytes, -s) 8192
cpu time (seconds, -t) unlimited
max user processes (-u) 100
virtual memory (kbytes, -v) 200000
file locks (-x) unlimited

--
Jason Lustig
Israel: 054-231-8476
U.S.: 716-228-8729
Skype: jasonlustig

On Oct 16, 2007, at 10:01 AM, Richard Huxton wrote:

> Jason Lustig wrote:
>> I lowered the maintenance_work_mem to 50MB and am still getting
>> the same errors:
>> Oct 16 09:26:57 [16402]: [1-1] user=,db= ERROR: out of memory
>> Oct 16 09:26:57 [16402]: [1-2] user=,db= DETAIL: Failed on
>> request of size 52428798.
>> Oct 16 09:27:57 [16421]: [1-1] user=,db= ERROR: out of memory
>> Oct 16 09:27:57 [16421]: [1-2] user=,db= DETAIL: Failed on
>> request of size 52428798.
>> Oct 16 09:29:44 [16500]: [1-1] user=,db= ERROR: out of memory
>> Oct 16 09:29:44 [16500]: [1-2] user=,db= DETAIL: Failed on
>> request of size 52428798.
>
> Hmm - it's now failing on a request of 50MB, which shows it is in
> fact maintenance_work_mem that's the issue.
>
>> Looking at my free memory (from TOP) I find
>> Mem: 2062364k total, 1846696k used, 215668k free, 223324k
>> buffers
>> Swap: 2104496k total, 160k used, 2104336k free, 928216k
>> cached
>> So I don't think that I'm running out of memory total... it seems
>> like it's continually trying to do it. Is there a reason why
>> Postgres would be doing something without a username or database?
>> Or is that just how autovacuum works?
>
> I've not seen an error at startup before, but if it's not connected
> yet then that would make sense.
>
> I'm guessing this is a per-user limit that the postgres user is
> hitting. If you "su" to user postgres and run "ulimit -a" that
> should show you if you have any limits defined. See "man bash" for
> more details on ulimit.
>
>
> --
> Richard Huxton
> Archonet Ltd

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