Subject: Re: wal_buffer tests in
From: Simon Riggs <simon@2ndquadrant.com>
To: josh@agliodbs.com
Cc: pgsql-hackers@postgresql.org
In-Reply-To: <200507271330.02083.josh@agliodbs.com>
References: <200507271330.02083.josh@agliodbs.com>
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Organization: 2nd Quadrant
Date: Wed, 27 Jul 2005 23:00:55 +0100
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On Wed, 2005-07-27 at 13:30 -0700, Josh Berkus wrote:

> I ran a wal_buffer test series.   It appears that increasing the 
> wal_buffers is indeed very important for OLTP applications, potentially 
> resulting in as much as a 15% average increase in transaction processing.  
> What's interesting is that this is not just true for 8.1, it's true for 
> 8.0.3 as well.   

The most important thing about these tests is that for the first time we
have eliminated much of the post checkpoint noise-and-delay.

Look at the response time charts between

http://khack.osdl.org/stp/302959/results/0/rt.html

and

http://khack.osdl.org/stp/302963/results/0/rt.html

This last set of results is a thing of beauty and I must congratulate
everybody involved for getting here after much effort.

The graphs are smooth, which shows a balanced machine. I'd like to
repeat test 302963 with full_page_writes=false, to see if those response
time spikes at checkpoint drop down to normal level.

I think these results are valid for large DW data loads also.

Best Regards, Simon Riggs