Re: pg 8.1.3, AIX, huge box, painfully slow.

Gavin Hamill <gdh(at)laterooms(dot)com> writes:
> Scott Marlowe <smarlowe(at)g2switchworks(dot)com> wrote:
>> My guess is that this is an OS issue. Maybe there are AIX tweaks that
>> will get it up to the same or higher level of performance as your four
>> way xeon. Maybe there aren't.

> The pSeries isn't much older than our Xeon machine, and I expected the
> performance level to be exemplary out of the box..

I'm fairly surprised too. One thing I note from your comparison of
settings is that the default WAL sync method is different on the two
operating systems. If the query load is update-heavy then it would be
very worth your while to experiment with the sync method. However,
if the bottleneck is pure-SELECT transactions then WAL sync should not
be a factor at all.

Does AIX have anything comparable to oprofile or dtrace? It'd be
interesting to try to monitor things at that level and see what we can
learn. Failing a low-level profiler, there should at least be something
comparable to strace --- you should try watching some of the backends
with strace and see what their behavior is when the performance goes
south. Lots of delaying select()s or semop()s would be a red flag.

regards, tom lane