Re: Auto-tuning work_mem and maintenance_work_mem

On Thu, Oct 10, 2013 at 10:20:02AM -0700, Josh Berkus wrote:
> On 10/09/2013 02:15 PM, Bruce Momjian wrote:
> > and for shared_buffers of 2GB:
> >
> > test=> show shared_buffers;
> > shared_buffers
> > ----------------
> > 2GB
> > (1 row)
> >
> > test=> SHOW work_mem;
> > work_mem
> > ----------
> > 6010kB
> > (1 row)
>
> Huh? Only 6MB work_mem for 8GB RAM? How'd you get that?

> That's way low, and frankly it's not worth bothering with this if all
> we're going to get is an incremental increase. In that case, let's just
> set the default to 4MB like Robert suggested.

Uh, well, 100 backends at 6MB gives us 600MB, and if each backend uses
3x work_mem, that gives us 1.8GB for total work_mem. This was based on
Andrew's concerns about possible over-commit of work_mem. I can of
course adjust that.

Consider 8GB of shared memory is 21MB.

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

+ Everyone has their own god. +