On Mon, Apr 21, 2014 at 6:38 PM, Jim Nasby <j...@nasby.net> wrote: >> I feel that if there is no memory pressure, frankly it doesnt matter much >> about what gets out and what not. The case I am specifically targeting is >> when the clocksweep gets to move about a lot i.e. high memory pressure >> workloads. Of course, I may be totally wrong here. > > Well, there's either memory pressure or there isn't. If there isn't then > it's all moot *because we're not evicting anything*.
I don't think that's really true. A workload can fit within shared_buffers at some times and spill beyond it at others. Every time it fits within shared_buffers for even a short period of time, the reference count of any buffer that's not ice-cold goes to 5 and we essentially lose all knowledge of which buffers are relatively hotter. Then, when we spill out again, evictions are random. -- 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
