On Wed, May 7, 2014 at 2:49 PM, Andres Freund <and...@2ndquadrant.com> wrote: > On 2014-05-07 11:45:04 -0700, Peter Geoghegan wrote: >> On Wed, May 7, 2014 at 11:38 AM, Andres Freund <and...@2ndquadrant.com> >> wrote: >> >> *) raising shared buffers does not 'give more memory to postgres for >> >> caching' -- it can only reduce it via double paging >> > >> > That's absolutely not a necessary consequence. If pages are in s_b for a >> > while the OS will be perfectly happy to throw them away. >> >> The biggest problem with double buffering is not that it wastes >> memory. Rather, it's that it wastes memory bandwidth. > > Doesn't match my experience. Even with the current buffer manager > there's usually enough locality to keep important pages in s_b for a > meaningful time. I *have* seen workloads that should have fit into > memory not fit because of double buffering.
Same here. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
