1624711 - Youtube leaks closed tabs due to missing CC edge

Status: VERIFIED FIXED

(Core :: Audio/Video: Playback, defect, P1)

Description

[Nika Layzell [:nika] (ni? for response)]

Earlier today I was experiencing very poor performance when switching tabs and other actions, due to long (>5 second) CCs on YouTube, caused by us leaking ~600MB of closed window objects.

Based on CC and GC logs, I discovered YouTube was installing MediaSessionEventHandler callbacks, which are being held alive by non-traversed strong references, and causing memory leaks. It appears as though the mActionHandlers field of MediaSession (https://searchfox.org/mozilla-central/rev/c80fa7258c935223fe319c5345b58eae85d4c6ae/dom/media/mediasession/MediaSession.h#92) is not being exposed to the cycle-collector, which would explain this leak.

This should be fixed by ensuring the pointers in mActionHandlers are traversed and unlinked by the cycle-collector.

Marking bug 1620077 as the regressing bug, due to it enabling this feature on Nightly.

Comment 1

[Nika Layzell [:nika] (ni? for response)]

Attachment: Bug 1624711 - Traverse and Unlink MediaSession::mActionHandlers

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/dea5a9179f87
Traverse and Unlink MediaSession::mActionHandlers r=alwu

Comment 3

[Virtual_ManPL [:Virtual] 🇵🇱 - (please needinfo? me - so I will see your comment/reply/question/etc.)]

@ :Nika Layzell - Thank you very much for diagnosing this issue!
I have identical problems, even when all tabs and windows were closed, leaving only new tab, Firefox will be using lot of CPU from time to time.
Here's profile - https://bit.ly/3agTy0H , maybe it will be useful in some way, if not, just for archive proposes.

Comment 6

[Oana Pop-Rus]

https://hg.mozilla.org/mozilla-central/rev/dea5a9179f87

Comment 7

[Virtual_ManPL [:Virtual] 🇵🇱 - (please needinfo? me - so I will see your comment/reply/question/etc.)]

I'm confirming that bug is fixed, starting in Mozilla Firefox Nightly 76.0a1 (2020-03-25), so I'm marking this bug as VERIFIED.
Thank you very much! \o/