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Re: Performance regression on CVS head

From: Heikki Linnakangas <heikki(at)enterprisedb(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Performance regression on CVS head
Date: 2007-06-05 08:16:19
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Lists: pgsql-hackers
Tom Lane wrote:
> Heikki Linnakangas <heikki(at)enterprisedb(dot)com> writes:
>> I tried to repeat the DBT-2 runs with the "oldestxmin refresh" patch, 
>> but to my surprise the baseline run with CVS head, without the patch, 
>> behaved very differently than it did back in March.
>> I rerun the a shorter 1h test with CVS head from May 20th, and March 6th 
>> (which is when I ran the earlier tests), and something has clearly been 
>> changed between those dates that affects the test. Test run 248 is with 
>> CVS checkout from May 20th, and 249 is from March 6th:
> May 20th is not quite my idea of "HEAD" ;-).  It might be worth checking
> current code before investing any think-time on this. 

:) Yeah, I did run it with real head at first. I suspected the 
n_live_tuples calculations, and that's why I ran it again with a 
checkout from May 20th.

> But having said
> that, it looks a bit like a planner problem --- if I'm reading the
> graphs correctly, I/O wait time goes through the roof, suggesting a
> change to a much less efficient plan.


I'll do a "binary search" with a checkouts from different dates runs to 
pin it down.

   Heikki Linnakangas

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