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Re: LISTEN / NOTIFY performance in 8.3

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Joel Stevenson <joelstevenson(at)mac(dot)com>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: LISTEN / NOTIFY performance in 8.3
Date: 2008-02-24 18:57:48
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-performance
Joel Stevenson <joelstevenson(at)mac(dot)com> writes:
>> This sounds a bit like pg_listener has gotten bloated.  Try a "VACUUM
>> VERBOSE pg_listener" (as superuser) and see what it says.

> At the moment (server is inactive):

> pcdb=# VACUUM VERBOSE pg_listener;
> INFO:  vacuuming "pg_catalog.pg_listener"
> INFO:  "pg_listener": removed 1 row versions in 1 pages
> INFO:  "pg_listener": found 1 removable, 21 nonremovable row versions 
> in 28 pages

OK, that destroys the table-bloat theory.  Just to make sure, I
pre-populated pg_listener with enough dead rows to make 28 pages,
but I still don't see any slow notifies or noticeable load in vmstat.

That server is not quite "inactive", though.  What are the 21 remaining
pg_listener entries for?  Is it possible that those jobs are having
some impact on the ones run by the test script?

Also, it might be worth enabling log_lock_waits to see if the slow
notifies are due to having to wait on some lock or other.

			regards, tom lane

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