On 2013-10-09 10:35:28 -0400, Bruce Momjian wrote: > On Wed, Oct 9, 2013 at 04:32:44PM +0200, Andres Freund wrote: > > On 2013-10-09 10:30:46 -0400, Bruce Momjian wrote: > > > Josh Berkus suggested here that work_mem and maintenance_work_mem could > > > be auto-tuned like effective_cache_size: > > > > > > http://www.postgresql.org/message-id/50eccf93.3060...@agliodbs.com > > > > > > The attached patch implements this, closely matching the default values > > > for the default shared_buffers value: > > > > There imo is no correlation between correct values for shared_buffers > > and work_mem at all. They really are much more workload dependant than > > anything. > > Well, that is true, but the more shared_buffers you allocate, the more > work_mem you _probably_ want to use. This is only a change of the > default.
Not at all. There's lots of OLTP workloads where huge shared buffers are beneficial but you definitely don't want a huge work_mem. > Effectively, if every session uses one full work_mem, you end up with > total work_mem usage equal to shared_buffers. But that's not how work_mem works. It's limiting memory, per node in the query. So a complex query can use it several dozen times. 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
