Re: Auto-tuning work_mem and maintenance_work_mem

2013/10/9 Bruce Momjian <bruce(at)momjian(dot)us>

> On Wed, Oct 9, 2013 at 04:32:44PM +0200, Andres Freund wrote:
> > On 2013-10-09 10:30:46 -0400, Bruce Momjian wrote:
> > > Josh Berkus suggested here that work_mem and maintenance_work_mem could
> > > be auto-tuned like effective_cache_size:
> > >
> > > http://www.postgresql.org/message-id/50ECCF93.3060101@agliodbs.com
> > >
> > > The attached patch implements this, closely matching the default values
> > > for the default shared_buffers value:
> >
> > There imo is no correlation between correct values for shared_buffers
> > and work_mem at all. They really are much more workload dependant than
> > anything.
>
> Well, that is true, but the more shared_buffers you allocate, the more
> work_mem you _probably_ want to use. This is only a change of the
> default.
>
> Effectively, if every session uses one full work_mem, you end up with
> total work_mem usage equal to shared_buffers.
>
> We can try a different algorithm to scale up work_mem, but it seems wise
> to auto-scale it up to some extent based on shared_buffers.
>

In my experience a optimal value of work_mem depends on data and load, so I
prefer a work_mem as independent parameter.

maintenance_work_mem can depend on work_mem ~ work_mem * 1 * max_connection
/ 4

Regards

Pavel

>
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> EnterpriseDB http://enterprisedb.com
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