Greg Smith wrote:
>
> Note that I've had some issues with the desktop Ubuntu giving slower
> results in tests like this than the same kernel release using the
> stock kernel parameters. Haven't had a chance yet to see how the
> server Ubuntu kernel fits into that or exactly what the desktop one is
> doing wrong yet. Could be worse--if you were running any 8.04 I expect
> your pgbench results would be downright awful.
Ah interesting. Isn't it a scheduler problem, I thought CFQ was the
default for desktop ?
I doublechecked the 7.10 server on this box and it's really the deadline
one that is used:
cat /sys/block/sdb/queue/scheduler
noop anticipatory [deadline] cfq
Do you have some more pointers on the 8.04 issues you mentioned ?
(that's deemed to be the next upgrade from ops)
>> postgresql 8.2.9 with data and xlog as mentioned above
> There are so many known performance issues in 8.2 that are improved in
> 8.3 that I'd suggest you really should be considering it for a new
> install at this point.
Yes I'd definitely prefer to go 8.3 as well but there are a couple
reasons for now I have to suck it up:
- 8.2 is the one in the 7.10 repository.
- I need plr as well and 8.3-plr debian package does not exist yet.
(I know in both cases we could recompile and install it from there, but ...)
> In general, you'll want to use a couple of clients per CPU core for
> pgbench tests to get a true look at the scalability. Unfortunately,
> the way the pgbench client runs means that it tends to top out at 20
> or 30 thousand TPS on read-only tests no matter how many cores you
> have around. But you may find operations where peak throughput comes
> at closer to 32 clients here rather than just 8.
ok. Make sense.
> As far as the rest of your results go, Luke's comment that you may
> need more than one process to truly see the upper limit of your disk
> performance is right on target. More useful commentary on that issue
> I'd recomend is near the end of
>
http://www.commandprompt.com/blogs/joshua_drake/2008/04/is_that_performance_i_smell_ext2_vs_ext3_on_50_spindles_testing_for_postgresql/
>
Yeah I was looking at that url as well. Very useful.
Thanks for all the info Greg.
-- stephane
