Re: pg_buffercache's usage count

Alvaro Herrera wrote:
> BTW the only reason you don't see buffers having a larger "usage" is
> that the counters are capped at that value.
>

Right, the usage count is limited to 5 for no reason besides "that seems
like a good number". We keep hoping to come across a data set and
application with a repeatable benchmark where most of the data ends up
at 5, but there's still a lot of buffer cache churn, to allow testing
whether a further increase could be valuable. So far nobody has
actually found such a set. If I shrunk shared_buffers on Ben's data I
think I could create that situation. As is usually the case, I doubt he
has another server with 128GB of RAM hanging around just to run that
experiment on though, which has always been the reason why I can't
simulate this more easily--systems it's prone to happening on aren't cheap.

--
Greg Smith 2ndQuadrant US Baltimore, MD
PostgreSQL Training, Services and Support
greg(at)2ndQuadrant(dot)com www.2ndQuadrant.us