Re: 2nd Level Buffer Cache

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?

Cheers,

Jeff