Re: Auto-tuning work_mem and maintenance_work_mem

On Thu, Oct 10, 2013 at 03:40:17PM -0700, Josh Berkus wrote:
>
> >> I don't follow that. Why would using a connection pooler change the multiples
> >> of work_mem that a connection would use?
> >
> > I assume that a connection pooler would keep processes running longer,
> > so even if they were not all using work_mem, they would have that memory
> > mapped into the process, and perhaps swapped out.
>
> Yes, and then this is when it *really* matters what OS you're running,
> and what release. FreeBSD and Solaris++ don't overallocate RAM, so
> those long-running connections pin a lot of RAM eventually. And for
> Linux, it's a question of how aggressive the OOM killer is, which kinda
> depends on distro/version/sysadmin settings.
>
> When I configure pgbouncer for Illumos users, I specifically have it
> rotate out old connections once an hour for this reason.

Just as a point of education, this is a good idea why you want to
allocate swap even if you expect your workload to fit in memory.
Pushing unused memory to swap is a good use of swap.

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

+ Everyone has their own god. +