PCTFree Results

Folks,

Well, it took a while but I finally have the results of Satoshi's PCTFree
patch back from the STP. Bad news about the STP, see below ...

Anyway, a series of DBT2 runs doesn't seem to show any advantage to PCTFree
over a 3-hour run with no vacuums:

test# pctfree full_page_writes notpm
303164 off off 1803
303165 on on 1847
303166 on off 1860
303167 off on 1801
303168 off off 1838
303169 on on 1821
303170 on off 1846

(again, check all results at http://www.testing.osdl.org/stp/######/)

The differences above are small enough to be in the "noise" factor of DBT2
execution. The good news is that it appears that stuff which has been
done since July has lessened the penalty for checkpoints somewhat; while
the maximum response time is still better on the full_page_writes=off
systems, the average throughput is no longer substantially different.
Either that, or full_page_writes=off isn't working properly anymore.

If anyone has suggestions on different tests to run, or better stats to
compile, please speak up.

Now, the bad news: the STP has had some failures and is down to *one*
usable machine for testing. I have, like, 160 performance tests backed up
which are never going to get run before we release 8.1. I'm going to be
hitting up some major PostgreSQL sponsors for hardware donations, any help
is welcome.

--
--Josh

Josh Berkus
Aglio Database Solutions
San Francisco