From: Luke Lonergan <llonergan@greenplum.com>
To: Alvaro Herrera <alvherre@alvh.no-ip.org>
Cc: Andrew McMillan <andrew@catalyst.net.nz>
Cc: Matthew Schumacher <matt.s@aptalaska.net>
Cc: pgsql-performance@postgresql.org
Subject: Re: Performance problems testing with Spamassassin
Date: Fri, 29 Jul 2005 10:11:10 -0700
Message-ID: <BF0FB13E.A3F4%llonergan@greenplum.com> (raw)
In-Reply-To: <20050729132319.GA13680@alvh.no-ip.org>
Alvaro,
On 7/29/05 6:23 AM, "Alvaro Herrera" <alvherre@alvh.no-ip.org> wrote:
> On Fri, Jul 29, 2005 at 03:01:07AM -0400, Luke Lonergan wrote:
>
>> I guess we see the real culprit here. Anyone surprised it's the WAL?
>
> So what? Are you planning to suggest people to turn fsync=false?
That's not the conclusion I made, no. I was pointing out that fsync has a
HUGE impact on his problem, which implies something to do with the I/O sync
operations. Black box bottleneck hunt approach #12.
> With fsync off, there's no
> work _at all_ going on, not just the WAL -- heap/index file fsync at
> checkpoint is also skipped. This is no good.
OK - so that's what Tom is pointing out, that fsync impacts more than WAL.
However, finding out that fsync/no fsync makes a 400% difference in speed
for this problem is interesting and relevant, no?
- Luke
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To: pgsql-performance@postgresql.org
Cc: llonergan@greenplum.com, alvherre@alvh.no-ip.org, andrew@catalyst.net.nz, matt.s@aptalaska.net
Subject: Re: Performance problems testing with Spamassassin
In-Reply-To: <BF0FB13E.A3F4%llonergan@greenplum.com>
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