Re: 2nd Level Buffer Cache

On Tue, Mar 22, 2011 at 3:53 PM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:

> On Tue, Mar 22, 2011 at 11:24 AM, Jeff Janes <jeff(dot)janes(at)gmail(dot)com> wrote:
> > On Fri, Mar 18, 2011 at 9:19 AM, Robert Haas <robertmhaas(at)gmail(dot)com>
> wrote:
> >> On Fri, Mar 18, 2011 at 11:14 AM, Kevin Grittner
> >> <Kevin(dot)Grittner(at)wicourts(dot)gov> wrote:
> >>> Maybe the thing to focus on first is the oft-discussed "benchmark
> >>> farm" (similar to the "build farm"), with a good mix of loads, so
> >>> that the impact of changes can be better tracked for multiple
> >>> workloads on a variety of platforms and configurations. Without
> >>> something like that it is very hard to justify the added complexity
> >>> of an idea like this in terms of the performance benefit gained.
> >>
> >> A related area that could use some looking at is why performance tops
> >> out at shared_buffers ~8GB and starts to fall thereafter.
> >
> > Under what circumstances does this happen? Can a simple pgbench -S
> > with a large scaling factor elicit this behavior?
>
> To be honest, I'm mostly just reporting what I've heard Greg Smith say
> on this topic. I don't have any machine with that kind of RAM.
>

I can sponsor a few hours (say 10) of one High-memory on-demand Quadruple
Extra Large instance (26 EC2 Compute Units (8 virtual cores with 3.25 EC2
Compute Units each), 1690 GB of local instance storage, 64-bit platform).
That's the largest memory AWS has.

Let me know if I can help.

Regards,
--
Gurjeet Singh
EnterpriseDB Corporation
The Enterprise PostgreSQL Company