Re: Memory usage of auto-vacuum

From: Guillaume Lelarge
Subject: Re: Memory usage of auto-vacuum
Date: ,
Msg-id: 1310200383.2101.8.camel@laptop
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In response to: Memory usage of auto-vacuum  (Gael Le Mignot)
Responses: Re: Memory usage of auto-vacuum  (Gael Le Mignot)
List: pgsql-performance

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Memory usage of auto-vacuum  (Gael Le Mignot, )
 Re: Memory usage of auto-vacuum  (Craig Ringer, )
  Re: Memory usage of auto-vacuum  (Gael Le Mignot, )
 Re: Memory usage of auto-vacuum  (Guillaume Lelarge, )
  Re: Memory usage of auto-vacuum  (Gael Le Mignot, )
   Re: Memory usage of auto-vacuum  (Guillaume Lelarge, )
    Re: Memory usage of auto-vacuum  (Gael Le Mignot, )
     Re: Memory usage of auto-vacuum  (Guillaume Lelarge, )
      Re: Memory usage of auto-vacuum  (Gael Le Mignot, )
       Re: Memory usage of auto-vacuum  (Tom Lane, )
        Re: Memory usage of auto-vacuum  (Gael Le Mignot, )
   Re: Memory usage of auto-vacuum  (Craig Ringer, )
 Re: Memory usage of auto-vacuum  (Gael Le Mignot, )

Hi,

On Sat, 2011-07-09 at 09:25 +0200, Gael Le Mignot wrote:
> [...]
> We are running  a PostgreSQL 8.4 database, with  two tables containing a
> lot (> 1 million) moderatly  small rows. It contains some btree indexes,
> and one of the two tables contains a gin full-text index.
>
> We noticed  that the  autovacuum process  tend to use  a lot  of memory,
> bumping the postgres process near 1Gb while it's running.
>

Well, it could be its own memory (see maintenance_work_mem), or shared
memory. So, it's hard to say if it's really an issue or not.

BTW, how much memory do you have on this server? what values are used
for shared_buffers and maintenance_work_mem?

> I looked in  the documentations, but I didn't find  the information : do
> you know  how to estimate the  memory required for the  autovacuum if we
> increase the number of rows ? Is it linear ? Logarithmic ?
>

It should use up to maintenance_work_mem. Depends on how much memory you
set on this parameter.

> Also, is  there a way  to reduce that  memory usage ?

Reduce maintenance_work_mem. Of course, if you do that, VACUUM could
take a lot longer to execute.

>  Would  running the
> autovacuum more frequently lower its memory usage ?
>

Yes.


--
Guillaume
  http://blog.guillaume.lelarge.info
  http://www.dalibo.com



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