In looking at bug 716445 (spin-off from bug 490122), I strummed the menus in Fedora 15 using a 12.x trunk build. They were unexpectedly slow, and the jprof showed a ton of fork()s and a lot of time in nsSound::PlayEventSound(). Per roc's comment: Probably something to do with libcanberra trying to play a system menu sound --- bug 567746, or bug 110385 The guess is that it's forking to play the menu event sounds (why do we have menu event sounds?) and while the sounds might be asynchronous, spawning the background process on each sound to handle it is expensive. Jprof: https://bugzilla.mozilla.org/attachment.cgi?id=586802

The forking is probably ESD. There's a plan to get rid of that code path (bug 635918), but it hasn't landed yet.

Bug 635918 just landed on inbound; all event sounds are now handled by libcanberra. Please retest and update the bug if there is still an issue.

I believe this is now fixed.