Re: [kris@obsecurity.org: Progress on scaling of FreeBSD on 8 CPU systems]

Tom Lane wrote:
> Stefan Kaltenbrunner <stefan(at)kaltenbrunner(dot)cc> writes:
>> Arjen van der Meijden wrote:
>>> Stefan Kaltenbrunner wrote:
>>>> ouch - do I read that right that even after tom's fixes for the
>>>> "regressions" in 8.2.0 we are still 30% slower then the -HEAD checkout
>>>> from the middle of the 8.2 development cycle ?
>>> Yes, and although I tested about 17 different cvs-checkouts, Tom and I
>>> weren't really able to figure out where "it" happened. So its a bit of a
>>> mystery why the performance is so much worse.
>
>> double ouch - losing that much in performance without an idea WHY it
>> happened is really unfortunate :-(
>
> Keep in mind that Arjen's test exercises some rather narrow scenarios;
> IIRC its performance is mostly determined by some complicated
> bitmap-indexscan cases. So that "30% slower" bit certainly doesn't
> represent an across-the-board figure. As best I can tell, the decisions
> the planner happened to be making in late June were peculiarly nicely
> suited to his test, but not so much for other cases.

understood - I was not trying to imply that we suffer a 30% performance
drop overall.
But still it means we know about a set of queries that we once could
handle faster than we can now ...

Stefan