Re: Solaris shared_buffers anomaly?

On Tue, Jun 13, 2006 at 04:20:34PM -0700, Mischa Sandberg wrote:
> Jim C. Nasby wrote:
> >On Tue, Jun 13, 2006 at 03:21:34PM -0700, Mischa Sandberg wrote:
> >>Raised shared_buffers to 16000 (128MB).
> >>DB server dropped to a CRAWL.
> >>
> >>vmstat showed that it was swapping like crazy.
> >>Dropped shared_buffers back down again.
> >>Swapping stopped.
> >
> >What's sort_mem set to? I suspect you simply ran the machine out of
> >memory.
>
> 8192 (8MB). No issue when shared_buffers was 2000; same apps always.

So if all 50 backends were running a sort, you'd use 400MB. The box has
4G, right?

> >Also, Solaris by default will only use a portion of memory for
> >filesystem caching, which will kill PostgreSQL performance.
>
> Yep, tested /etc/system segmap_percent at 20,40,60.
> No significant difference between 20 and 60.

That's pretty disturbing... how large is your database?
--
Jim C. Nasby, Sr. Engineering Consultant jnasby(at)pervasive(dot)com
Pervasive Software http://pervasive.com work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461