From: Tom Lane <tgl@sss.pgh.pa.us>
To: Erik Jones <erik@myemma.com>
Cc: PostgreSQL Performance <pgsql-performance@postgresql.org>
Subject: Re: Shared buffers, db transactions commited, and write IO on Solaris
Date: Thu, 29 Mar 2007 12:16:36 -0400
Message-ID: <23286.1175184996@sss.pgh.pa.us> (raw)
In-Reply-To: <9B7F4B34-7E96-4501-BCE0-D0BED739530A@myemma.com>
References: <9B7F4B34-7E96-4501-BCE0-D0BED739530A@myemma.com>
Erik Jones <erik@myemma.com> writes:
> We've recently made a couple changes to our system that have resulted
> in a drastic increase in performance as well as some very confusing
> changes to the database statistics, specifically
> pg_stat_database.xact_commit. Here's the details:
I'm kinda boggled too. I can see how increasing shared buffers could
result in a drastic reduction in write rate, if the working set of your
queries fits in the new space but didn't fit in the old. I have no idea
how that leads to a drop in number of transactions committed though.
It doesn't make sense that autovac would run less frequently, because
it's driven by number of tuples changed not number of disk writes; and
that could hardly account for a 10x drop anyway.
Did you by any chance take note of exactly which processes were
generating all the I/O or the CPU load?
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, erik@myemma.com
Subject: Re: Shared buffers, db transactions commited, and write IO on Solaris
In-Reply-To: <23286.1175184996@sss.pgh.pa.us>
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