I have a *very* serious issue with performance in 9.0.4 (build IC-95.621) running on 64-bit Ubuntu with jdk 1.6.0_21, 64-bit).
Every time I bring focus to the Idea window it simply hangs (no cursor movements, nothing) with 100% CPU on one core for a minimum of one minute, but sometimes up to three minutes - and this is on a 3.2GHz i7-960 with 12GB of memory(!) Granted we have a large code-base, about 1.4M lines of code in about 7000 java files, but this is simply ridicolous.
My qualified guess is that it's GC'ing, but the memory bar doesn't move a whole lot before or after, mostly just a few percent.
My vmoptions are as follows:
Typically used memory hovers around 400-800M, so way below maxmem. As long as Idea stays in focus everything's fine, but as soon as I drop focus and come back in I'm simply hosed to the point where I'm considering switching to another IDE. This is not just a nuisance but rather a major malfunction to the point where the product is simply unusable.
I have used Idea for many years at another company and really like it (as much as I dislike Eclipse) and I sincerely hope that someone can step in and tell me that all problems are fixed in 10.x or there is a simple configuration option. I am not looking for something that improves performance 10% though, but rather 10 times.