WebGPU on Apple Silicon causes system-wide video/animation stutter
Categories
(Core :: Graphics: WebGPU, defect)
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(Reporter: git.ilyag, Unassigned)
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(2 files)
User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:147.0) Gecko/20100101 Firefox/147.0
Steps to reproduce:
I upgraded to Firefox 147.
I am on macOS Sonoma 14.8.3, on MacBook Pro M2 Pro
Actual results:
My whole system started to stutter. most obviously if I had a Youtube video playing and switched it between full-screen and normal, either in firefox or in Safari (while Firefox with many tabs open was open).
After a lot of trial and errorr, it seems that:
** Setting dom.webgpu.enabled to false and restarting the browser fixes the problem entirely **
Expected results:
Shouldn't have this stutter.
Aboive is about:support after setting dom.webgpu.enabled to false (which seems to have fixed the issue).
Oh, also I have an external monitor attached, though detaching it didn't immediately fix the stutter.
Above is about:support with dom.webgpu.enabled set to true. The stutter is actually subtle at first, but grows much worse as Firefox stays on. At the same time, there is no memory pressure or particularly high GPU usage when the stutter appears.
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Comment 5•17 hours ago
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The Bugbug bot thinks this bug should belong to the 'Core::Graphics: WebGPU' component, and is moving the bug to that component. Please correct in case you think the bot is wrong.
A few more thoughts:
On my system, Firefox has dozens of tabs open. The best way to confirm that this bug exists might be for someone in a similar situation to notice the stutter, set dom.webgpu.enabled to false, restart Firefox, and notice how buttery-smooth their system suddenly is (on Sonoma at least, I hear that Tahoe has other WindowServer issues).
The stutter was most noticeable for when resizing windows or switching videos between Fullscreen and not (whether Firefox windows or Safari). It was also noticeable in Ghostty; I had it set to change the background of the active window, and that was slow. It feels like a macOS bug or like an under-powered computer that's out of memory or GPU resources, but it happens even when there's plenty of memory and GPU is not at 100%. It probably is some sort of a macOS WindowServer bug that Firefox's webgpu implementation triggers. The only reason I'm sure it's Firefox is that closing Firefox or disabling dom.webgpu.enabled fixes everything.
The stutter doesn't become severe immediately. If I set dom.webgpu.enabled to true and restart, it can be noticed but is subtle. It becomes severe in a few hours/days without restarting firefox.
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