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Re: survey of WAL blocksize changes

From: Simon Riggs <simon(at)2ndQuadrant(dot)com>
To: Mark Wong <markwkm(at)gmail(dot)com>
Cc: PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: survey of WAL blocksize changes
Date: 2009-05-28 07:17:41
Message-ID: 1243495061.24860.444.camel@ebony.2ndQuadrant (view raw or flat)
Thread:
Lists: pgsql-hackers
On Wed, 2009-05-27 at 17:51 -0700, Mark Wong wrote:
> On Wed, May 27, 2009 at 1:46 AM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
> >
> > On Tue, 2009-05-26 at 19:51 -0700, Mark Wong wrote:
> >> It appears for this workload using a 16KB or 32KB gets more than 4%
> >> throughput improvement, but some of that could be noise.
> >
> > The baseline appears to have a significant jump in txn response time
> > after 77 mins on the baseline test. I think you should rerun that. My
> > guess would be it will reduce any gains shown with higher settings.
> 
> Oopsies.  I've rerun, but now that there is no dip, the average
> throughput still didn't change much:
> 
> BS notpm % Change from default
> -- ----- ----------
>  1 14673 -5.1%
>  2 15864 2.7%
>  4 15774 2.1%
>  8 15454 (default)
> 16 16118 4.3%
> 32 16051 3.9%
> 64 14874 -3.8%
> 
> Pointers to raw data:
> 
> BS url
> -- ---
>  1 http://207.173.203.223/~markwkm/community6/dbt2/m1500-8.4beta2/m1500.8.4beta2.wal.1/
>  2 http://207.173.203.223/~markwkm/community6/dbt2/m1500-8.4beta2/m1500.8.4beta2.wal.2/
>  4 http://207.173.203.223/~markwkm/community6/dbt2/m1500-8.4beta2/m1500.8.4beta2.wal.4/
>  8 http://207.173.203.223/~markwkm/community6/dbt2/m1500-8.4beta2/m1500.8.4beta2.wal.8/report/
> 16 http://207.173.203.223/~markwkm/community6/dbt2/m1500-8.4beta2/m1500.8.4beta2.wal.16/
> 32 http://207.173.203.223/~markwkm/community6/dbt2/m1500-8.4beta2/m1500.8.4beta2.wal.32/
> 64 http://207.173.203.223/~markwkm/community6/dbt2/m1500-8.4beta2/m1500.8.4beta2.wal.64/

Look at these graphs, in this order
http://207.173.203.223/~markwkm/community6/dbt2/m1500-8.4beta2/m1500.8.4beta2.wal.16/report/rt_d.png
http://207.173.203.223/~markwkm/community6/dbt2/m1500-8.4beta2/m1500.8.4beta2.wal.2/report/rt_d.png
http://207.173.203.223/~markwkm/community6/dbt2/m1500-8.4beta2/m1500.8.4beta2.wal.8/report/rt_d.png

BS 16 and 2 look very similar, though with 16 clearly a better curve.
BS=8 looks very strange in comparison. Still something wrong, I suspect.

-- 
 Simon Riggs           www.2ndQuadrant.com
 PostgreSQL Training, Services and Support


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