Brian Fehrle <brianf@xxxxxxxxxxxxxxxxxxx> wrote: > In this system I have a table that is extremely active. On a > 'normal' day, the autovacuum process takes about 7 hours to > complete on this table, and once it's complete, the system > performs an autoanalyze on the table, finding that we have > millions of new dead rows. Once this happens, it kicks off the > autovacuum again, so we basically always have a vacuum running on > this table at any given time. > > If I were to tweak the autovacuum_vacuum_cost_delay parameter, > what would that be doing? That controls how long an autovacuum worker naps after it has done enough work to hit the autovacuum_cost_limit. As tuning knobs go, this one is pretty coarse. > Would it be limiting what the current autovacuum is allowed to do? No, just how fast it does it. > Or does it simply space out the time between autovacuum runs? Not that either; it's part of pacing the work of a run. > In my case, with 7 hour long autovacuums (sometimes 14 hours), a > few milliseconds between each vacuum wouldn't mean anything to me. Generally, I find that the best way to tune it is to pick 10ms to 20ms for autovacuum_cost_delay, and adjust adjust autovacuum_cost_limit to tune from there. A small change in the former can cause a huge change in pacing; the latter is better for fine-tuning. > It may cause the system to perform better at that time, but would > prolong the length of the autovacuum right? Right. -Kevin -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
