On 01/23/2014 07:22 PM, Alvaro Herrera wrote:
>> If you ask me, I'd like autovac to know when not to run (or rather
>> > wait a bit, not forever), perhaps by checking load factors or some
>> > other tell-tale of an already-saturated I/O system.
> We had a proposed design to tell autovac when not to run (or rather,
> when to switch settings very high so that in practice it'd never run).
> At some point somebody said "but we can just change autovacuum=off in
> postgresql.conf via crontab when the high load period starts, and turn
> it back on afterwards" --- and that was the end of it.
Anything which depends on a timing-based feedback loop is going to be
hopeless. Saying "autovac shouldn't run if load is high" sounds like a
simple statement, until you actually try to implement it.
--
Josh Berkus
PostgreSQL Experts Inc.
http://pgexperts.com