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. Greetings, Andres Freund -- Andres Freund http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
