Gavin Hamill <gdh@xxxxxxxxxxxxx> writes: > Scott Marlowe <smarlowe@xxxxxxxxxxxxxxxxx> 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
