On Fri, Dec 14, 2012 at 10:40 AM, Andrew Dunstan < andrew.duns...@pgexperts.com> wrote: > One of my clients has an odd problem. Every so often a backend will suddenly > become very slow. The odd thing is that once this has happened it remains > slowed down, for all subsequent queries. Zone reclaim is off. There is no IO > or CPU spike, no checkpoint issues or stats timeouts, no other symptom that > we can see.
By "no spike", do you mean that the system as a whole is not using an unusual amount of IO or CPU, or that this specific slow back-end is not using an unusual amount? Could you strace is and see what it is doing? > The problem was a lot worse that it is now, but two steps have > alleviated it mostly, but not completely: much less aggressive autovacuuming > and reducing the maximum lifetime of backends in the connection pooler to 30 > minutes. Do you have a huge number of tables? Maybe over the course of a long-lived connection, it touches enough tables to bloat the relcache / syscache. I don't know how the autovac would be involved in that, though. Cheers, Jeff
