On Wed, Oct 10, 2012 at 02:05:20PM -0300, Claudio Freire wrote: > On Wed, Oct 10, 2012 at 1:10 PM, Bruce Momjian <bruce@xxxxxxxxxx> wrote: > >> >shared_buffers = 10GB > >> > >> Generally going over 4GB for shared_buffers doesn't help.. some of > >> the overhead of bgwriter and checkpoints is more or less linear in > >> the size of shared_buffers .. > >> > >> >effective_cache_size = 90GB > >> > >> effective_cache_size should be ~75% of the RAM (if it's a dedicated server) > > > > Why guess? Use 'free' to tell you the kernel cache size: > > > > http://momjian.us/main/blogs/pgblog/2012.html#May_4_2012 > > Why does nobody every mention that concurrent access has to be taken > into account? > > Ie: if I expect concurrent access to 10 really big indices, I'll set > effective_cache_size = free ram / 10 It is true that the estimate assumes a single session is using all the cache, but I think that is based on the assumion is that there is a major overlap between the cache needs of multiple sessions. -- Bruce Momjian <bruce@xxxxxxxxxx> http://momjian.us EnterpriseDB http://enterprisedb.com + It's impossible for everything to be true. + -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
