On Sun, 2007-03-04 at 10:14 -0800, Tom Lane wrote:
> If you did this only once, the results are not really trustworthy;
> you need to average several similar runs before you can have much
> confidence. pgbench's inter-run variation is usually upwards of 10%,
> so trying to draw conclusions about half-percentage-point differences
> without averaging is a waste of time.
Good point, thanks
> Also, if scaling factor < number of clients then what you're mostly
> measuring is update-contention behavior. Try it with -s 10 and -c 5;
> and don't forget to reinitialize the database for each run of tests
> to be sure it's fair.
>
I did another 18 runs, 9 each for huge pages and normal shared memory.
The database was reinitialized before every third run with "pgbench -i
-s 10". The runs themselves were done with "pgbench -s 10 -c 5 -t 10000"
Normal shared memory:
tps = 1835.929043 (including connections establishing)
tps = 1697.455165 (including connections establishing)
tps = 1378.393001 (including connections establishing)
tps = 1834.802729 (including connections establishing)
tps = 1630.100895 (including connections establishing)
tps = 1415.504943 (including connections establishing)
tps = 1864.908838 (including connections establishing)
tps = 1726.295622 (including connections establishing)
tps = 1323.679649 (including connections establishing)
Average: 1634.19 tps
Huge pages:
tps = 1867.400381 (including connections establishing)
tps = 1715.269338 (including connections establishing)
tps = 1259.314139 (including connections establishing)
tps = 1880.803336 (including connections establishing)
tps = 1885.351404 (including connections establishing)
tps = 1603.302855 (including connections establishing)
tps = 1884.888431 (including connections establishing)
tps = 1563.452093 (including connections establishing)
tps = 1361.896887 (including connections establishing)
Average: 1669.08
That works out to approximately a 2.1% performance boost for huge pages.
It still doesn't seem very compelling but I could try to put together a
patch for inclusion if people were interested in such a thing.
-Ryan
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