Build: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2a1pre) Gecko/20090306 Minefield/3.2a1pre An animation engine in a garbage-collected language requires short GC pauses for smooth animation. A 150 ms GC pause every 10 seconds in a 30 fps animation is visually jarring. But a 3 ms pause every 0.1 seconds looks OK, even if the GC throughput is halved as a result. I'm seeing >100 ms spikes in the attached simulation of a 60 fps animation with 150 4x4 matrix multiplications per frame. A 10 fps (100 ms) frame in a 60 fps animation sticks out like a sore thumb.

I am seeing the same effect. I'm working on something similar, but it uses an experimental extension to canvas. You can run our benchmark without the extension though: http://www.c3dl.org/test-case/benchmark.html I've filed a bug on javascript rather than canvas, but I believe it may be a duplicate of your bug: https://bugzilla.mozilla.org/show_bug.cgi?id=482853

Is the problem still present? Perhaps close this bug as duplicate of bug 482853 ?

This seems pretty solid now, but can still be better; but we should file explicit examples of GC interruptions.