Re: 2nd Level Buffer Cache

On Tue, Mar 22, 2011 at 11:24 AM, Jeff Janes <jeff.janes@gmail.com> wrote:
> On Fri, Mar 18, 2011 at 9:19 AM, Robert Haas <robertmhaas@gmail.com> wrote:
>> On Fri, Mar 18, 2011 at 11:14 AM, Kevin Grittner
>> <Kevin.Grittner@wicourts.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.