UI responsiveness is when you click or hit a key and the app responds immediately, or does not while it should. Goal for "responsive": UI should react within 20ms, in any situation. --- This bug is about what needs to change in Core / Gecko / the Mozilla platform to make this possible.

This bug contains both Core changes that are strictly necessary to allow this responsiveness, as well as features/components which make it easier for applications to do the right thing. Bug 384325 is about where applications need to be fixed.

I have apps including Firefox beach-ball on my mac due to memory bloat. That does not fall under this bug, or else this bug must track all leak and bloat bugs, which reduces its usefulness to nearly zero. So this bug needs some clear statement of initial conditions before the click happens, as far as virtual and physical memory loads. Agreed? /be

How does this metabug differ from bug 91351?

Maybe it's just the next generation. One solution less drastic than duping: make bug 91351 block this bug. /be

Jesse, I simply wasn't aware of the other bug. Looking over the deps, a lot of it is app code (-> bug 384325), though, so I'll mark it as blocker of the other one.

Bug 384412 is of interest. I could see it being linked from both "app" and "core" meta-bugs, since JS can run too long for both. But "app" JS is more controlled, apart from addons, so should be able to avoid starving the UI by decree. I will let BenB or someone else add the dep(s). /be

this bug is not actionable, assigning it to myself to go through the dependencies see if any of them are snappy-worthy.

Picked out a couple of candidates for [Snappy] from dependencies.

ddurst I'm going to hand this to you; feel free to close it out or keep it around as you see fit.