1935804 - YouTube creating or exacerbating performance issues across Firefox, resulting in low responsiveness (7 second lon CC's)

Status: RESOLVED DUPLICATE of bug 1939295

(Core :: Performance, defect)

Description

[Matt Rasmussen]

User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:133.0) Gecko/20100101 Firefox/133.0

Steps to reproduce:

Consistent repro has been tricky, but it's been happening for months, and now across multiple machines (Intel and Apple Silicon Macs, reasonably high memory machines that otherwise aren't having memory pressure issues). User uses Firefox with a fairly high tab count, including multiple windows and tabs/suspended tabs involving YouTube videos, watching several hours' worth of videos between recurrence of the bug, sometimes taking multiple days to recur.

Actual results:

Over time, responsiveness degrades (particularly with YouTube pages, but elsewhere in the app as well) -- UI triggers take longer, hover events, links, media interactions (pause/play), even text selection will have multi-second delays.

Recently discovered that Firefox's Task Manager can occasionally identify the "problem" YouTube tabs -- if the tab in question's group is terminated, responsiveness returns, even upon reloading the "problem" page. Closing the individual tabs normally doesn't seem to be sufficient.

Profile of a short interaction with a page exhibiting the issue: https://share.firefox.dev/4gqjubR ; the timeline shows event processing delays aligned with the jank felt by the user.

Expected results:

Performance of Firefox and the webpages in question should not excessively degrade, and forcibly shutting down "problem" tabs shouldn't be required to restore normal browser functionality.

Comment 1

[BugBot [:suhaib / :marco/ :calixte]]

The Bugbug bot thinks this bug should belong to the 'Core::Audio/Video: Playback' component, and is moving the bug to that component. Please correct in case you think the bot is wrong.

Comment 2

[BugBot [:suhaib / :marco/ :calixte]]

This bug was moved into the Performance component.

:mrasmus, could you make sure the following information is on this bug?

• ✅ For slowness or high CPU usage, capture a profile with http://profiler.firefox.com/, upload it and share the link here.
• For memory usage issues, capture a memory dump from about:memory and attach it to this bug.
• Troubleshooting information: Go to about:support, click "Copy raw data to clipboard", paste it into a file, save it, and attach the file here.

If the requested information is already in the bug, please confirm it is recent.

Thank you.

Comment 3

[Kagami Rosylight [:saschanaz] (they/them)]

Dupe of bug 1931717?

Comment 4

[Alexey104]

I have also been struggling with this issue for months. ArchLinux, X11, Firefox 133.0.3, but also reproducible on older versions, clean profile and no extensions installed. My performance profile is here After some time spent on Youtube one of the CPU cores starts showing spikes to 100% every several seconds, and the UI lags and freezes a lot until Isolated Web Content process is killed.

Comment 5

[Matt Rasmussen]

Attachment: Troubleshooting information

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Comment 6

[Matt Rasmussen]

Attached troubleshooting information, I've been unable to grab memory dumps as the issue has been occurring due to poor timing, but I'll try to get it and will upload when I get the chance. I'll grab another profile to share at that time as well, just so that the two are consistent with one another.

Comment 7

[sheaf]

Having an identical issue, MacOS 15 with M3. ~30 seconds of jank. https://share.firefox.dev/4fALEQk

@Kagami not a duplicate at least in as much as the issues being reported occur in different places (YT Live v.s. the whole site).

Comment 8

[sheaf]

https://bugzilla.mozilla.org/show_bug.cgi?id=1913404

Comment 9

[sheaf]

(In reply to sheaf from comment #8)

https://bugzilla.mozilla.org/show_bug.cgi?id=1913404

Apologies, unsure of how to officially add via the 'See also' links

Comment 10

[y31z8tnp6]

(In reply to sheaf from comment #7)

Having an identical issue, MacOS 15 with M3. ~30 seconds of jank. https://share.firefox.dev/4fALEQk

@Kagami not a duplicate at least in as much as the issues being reported occur in different places (YT Live v.s. the whole site).

Also having an identical issue on MacOS 15.2 with M1 base model. I got about 8 seconds of jank on this particular profile. CPU usage skyrockets, fans spin up and the window becomes unresponsive to media controls such as clicking to pause the video or bringing up the seek bar. I can't consistently reproduce the issue but it's normally manifests on youtube tabs that have been sleeping for awhile after I've made them the active tab. I have no idea how to make this consistently reproduceable though.

https://share.firefox.dev/41RYvKJ

Comment 11

[Bas Schouten (:bas.schouten)]

Indeed sounds to me like it might be a dupe of 1935456.

The Performance Impact Calculator has determined this bug's performance impact to be high. If you'd like to request re-triage, you can reset the Performance Impact flag to "?" or needinfo the triage sheriff.

Platforms: [x] Windows [x] macOS
Impact on site: Causes noticeable jank
Websites affected: Major
[x] Multiple reporters

Comment 12

[Andrew McCreight [:mccr8]]

The profiles in this bug show the CPU is being used for the cycle collector, so this is probably a dupe of bug 1939295. We released a fix for that in a Firefox update this week, so please update your browser and see if you are still experiencing this problem.