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 13:32:54
Message-ID: 57031F92-40D5-4832-8B76-FB73E510C735@brandeis.edu
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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.

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?

Thanks,
Jason

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

On Oct 16, 2007, at 8:23 AM, Richard Huxton wrote:

> Jason Lustig wrote:
>> There isn't any more error message than this... it simply repeats
>> every minute or so, which is really quite strange. And the user &
>> db is really blank in the log, I didn't trim it (if I did I would
>> have replaced it with dummy values).
>
> Hmm - odd that you're not getting any connection details.
>
>> I'm using pg 8.2.4 on Linux 2.6.15.
>
> Fair enough.
>
>>>> Oct 16 06:43:47 [2897]: [1-1] user=,db= ERROR: out of memory
>>>> Oct 16 06:43:47 [2897]: [1-2] user=,db= DETAIL: Failed on
>>>> request of size 524287998.
>
> Well, since this is about 500MB and your maintenance_work_mem is
> set to 500MB that's the obvious place to start. It might just be
> that you've not got enough free memory.
>
> What happens if you set maintenance_work_mem to say 50MB?
>
> --
> Richard Huxton
> Archonet Ltd
>
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