1661491 - Frame dropping due to GC when looking at https://arewefenixyet.com

Status: NEW

(Core :: JavaScript: GC, defect, P2)

Description

[(No longer employed by Mozilla) Aaron Klotz]

Windows 10

Going to https://arewefenixyet.com, I periodically see dropped frames in the confetti animation.

I captured this profile, which looks like a full USER_INACTIVE GC is running. Is this just a heuristic thing?

https://share.firefox.dev/34DANVa

Comment 1

[Jon Coppeard (:jonco)]

We run a USER_INACTIVE GC when the user has been idle for a while. (I had forgotten this, but the time from idle to running this GC is 5 minutes in release builds but 15 seconds on nightly which seems like a pretty drastic difference).

We shouldn't really be doing this if there's an animation running, and we should also stagger these GCs across content processes which doesn't look like it's happening from your profile.

CC Steve who is looking into scheduling at the moment.

Comment 2

[Paul Bone [:pbone]]

From the staggering GCs across processes we have Bug 1629064 (it mentions PAGE_HIDE but should do USER_INACTIVE) as well.

If we really want to GC during animation (maybe we have to due to allocation thresholds) the dom code should be giving smaller slice budgets also.

Comment 3

[Jon Coppeard (:jonco)]

(In reply to Paul Bone [:pbone] from comment #2)

If we really want to GC during animation (maybe we have to due to allocation thresholds) the dom code should be giving smaller slice budgets also.

Agreed. Steve, do you know if there's a bug for this? I know it's come up a couple of times but I couldn't find which bug it was.