Re: Lockless pg_buffercache

On Feb 9, 2008 10:34 PM, Markus Bertheau <mbertheau(dot)pg(at)googlemail(dot)com> wrote:
> Hi,
>
> I want to use the pg_buffercache contrib module for monitoring our
> server. It takes a lock on all buffers and then on each buffer header
> in order to get a consistent picture of the buffers. I would be
> running the function provided by the module once every 5 minutes.

If it takes 500mS every 5 minutes that might be an acceptable decrease
in performance for that second or two.

> I'm worrying about the performance hit of that - a comment in the code
> says it's horrible for concurrency.

It is, but again, it really depends on the time frame etc. If you can
run it quickly as a series of related queries or a user function, it
should be fast enough to not be a significant burden.

So, what's the real burden like from the pg_buffercache contrib module?