From: | Josh Berkus <josh(at)agliodbs(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | postgres performance list <pgsql-performance(at)postgresql(dot)org> |
Subject: | Re: Anyone seen this kind of lock pileup? |
Date: | 2010-11-17 23:42:14 |
Message-ID: | 4CE46856.7070006@agliodbs.com |
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Thread: | |
Lists: | pgsql-performance |
>> What's odd about this is that the resulting "lock pileup" takes a
>> mysterious 2-3.5 seconds to clear, despite the fact that none of the
>> connections are *doing* anything during that time, nor are there
>> deadlock errors. In theory at least, the locks should clear out in
>> reverse order in less than a second; none of the individual statements
>> takes more than 10ms to execute.
Ok, I've collected more data. Looks like the case I was examining was
idiosyncratic; most of these lock pile-ups involve 400 or more locks
waiting held by around 20 different backends. Given this, taking 3
seconds to sort that all out doesn't seem that unreasonable.
Presumably there's a poll cycle of some sort for waiting statements?
Anyway, the obvious answer is for the user to fix their application.
--
-- Josh Berkus
PostgreSQL Experts Inc.
http://www.pgexperts.com
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