| From: | Josh Berkus <josh(at)agliodbs(dot)com> |
|---|---|
| To: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Claudio Freire <klaussfreire(at)gmail(dot)com> |
| Cc: | Craig Ringer <craig(at)2ndquadrant(dot)com>, Andres Freund <andres(at)2ndquadrant(dot)com>, Mark Kirkwood <mark(dot)kirkwood(at)catalyst(dot)net(dot)nz>, Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, "Joshua D(dot) Drake" <jd(at)commandprompt(dot)com> |
| Subject: | Re: Why do we let autovacuum give up? |
| Date: | 2014-01-24 17:44:27 |
| Message-ID: | 52E2A67B.60208@agliodbs.com |
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| Lists: | pgsql-hackers |
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
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