I'm gearing up to do some serious investigation into performance for PostgreSQL with regard to our application. I have two issues that I've questions about, and I'll address them in two seperate emails. This one regards tuning shared_buffers. I believe I have a good way to monitor database activity and tell when a database grows large enough that it would benefit from more shared_buffers: if I monitor the blks_read column of pg_stat_database, it should increase very slowly if there is enough shared_buffer space. When shared buffer space runs out, more disk read requests will be required and this number will begin to climb. If anyone sees a flaw in this approach, I'd be interested to hear it. The other tuning issue with shared_buffers is how to tell if I'm allocating too much. For example, if I allocate 1G of RAM to shared buffers, and the entire database can fit in 100M, that 900M might be better used as work_mem, or something else. I haven't been able to find anything regarding how much of the shared buffer space PostgreSQL is actually using, as opposed to simply allocating. -- Bill Moran Collaborative Fusion Inc. wmoran@xxxxxxxxxxxxxxxxxxxxxxx Phone: 412-422-3463x4023
