Re: Question about maintenance_work_mem and shared_buffer

On Tue, May 21, 2013 at 1:03 PM, Amit Langote <amitlangote09(at)gmail(dot)com>wrote:

> On Wed, May 22, 2013 at 12:07 AM, Rodrigo Barboza
> <rodrigombufrj(at)gmail(dot)com> wrote:
> > Hi, everyone.
> > I have a doubt.
> > I have a 32-bit postrgesql running with 2.5gb of shared_buffer.
> > And I have maintenance_work_mem = 1gb and autovacuum_max_workers = 3.
> > How maintenance_work_mem is related to shared_buffer?
>
> They are independent settings.
>
> > If the 3 workers uses 1gb, will the database crash?
>
> Documentation does warn about not setting it (maintenance_work_mem) too
> high:
>
> "Note that when autovacuum runs, up to autovacuum_max_workers times
> this memory may be allocated, so be careful not to set the default
> value too high."
>
> http://www.postgresql.org/docs/9.3/static/runtime-config-resource.html
>
> --
> Amit Langote
>

So what would it be a reasonable value?
Because I saw some people suggesting to set it to total_mem / 8.
In my case I am running a 32 bit postgres with 64gb of total memory. My
kernel is 64 bits (I know that is not ideal, but that's what I have now) to
recognize and use the to total memory.