Re: 8.3devel slower than 8.2 under read-only load

On Sat, 24 Nov 2007, Guillaume Smet wrote:

> Here are some rough results:
> http://people.openwide.fr/~gsmet/postgresql/postgresql_8.3_development_cycle_1.png

So the big dips were Jan->Feb and April->May.  I've still got the text of 
the commit log Tom assembled sitting at 
http://developer.postgresql.org/index.php/8.3_Changelog and 
http://www.westnet.com/~gsmith/content/postgresql/83revhist.txt if anyone 
wants a relatively easy way to see what happened then.

Scanning the January results, the biggest drop, I noted that 2007-01-16 
was the day autovacuum was turned on by default.  If you're sure it's 
explicitly disabled in every test that shouldn't matter, might be 
something worth double-checking.

The other commits that looked like a lot of code changes with potential 
for performance changes were all from Tom, on 2007-01-03, 2007-01-08, and 
2007-01-10, and 2007-01-20.  If you wanted to try and nail this down 
further, three dates with no commits that would narrow the source of the 
big regression(s) that month are 2007-01-07, 2007-01-13, 2007-01-22. 
2007-01-17 would be a good additional day to confirm that autovacuum 
wasn't responsible.

> packed varlenas were commited during April

There were also several changes to pgbench itself that month.  Useful 
breakpoints in that month to subdivide might be 2007-04-08 (after varlena 
change), 2007-04-17, 2007-04-22.

--
* Greg Smith gsmith@gregsmith.com http://www.gregsmith.com Baltimore, MD