Re: Shared_buffers

Justin Pryzby

Tuesday, March 12, 2019 4:11 PM

I've tuned ~40 postgres instances, primarily using log_checkpoints and
pg_stat_bgwriter, with custom RRD graphs. pg_buffercache does provide some
valuable insights, and I know it's commonly suggested to check histogram of
usagecounts, but I've never had any idea how to apply that to tune
shared_buffers.

Could you elaborate on what procedure you suggest ?

Justin

MichaelDBA

Tuesday, March 12, 2019 4:03 PM

Set shared_buffers more accurately by using pg_buffercache extension and the related queries during high load times.

Regards,
Michael Vitale

Michael Lewis

Tuesday, March 12, 2019 3:23 PM

On Tue, Mar 12, 2019 at 2:29 AM Laurenz Albe <laurenz.albe@cybertec.at> wrote:

Daulat Ram wrote:
> I want to know about the working and importance of shared_buffers  in Postgresql?
> is it similar to the oracle database buffer cache?

Yes, exactly.

The main difference is that PostgreSQL uses buffered I/O, while Oracle usually
uses direct I/O.

Usually you start with shared_buffers being the minimum of a quarter of the
available RAM and 8 GB.

Any good rule of thumb or write up about when shared buffers in excess of 8GBs makes sense (assuming system ram 64+ GBs perhaps)?