When joining a Google Meet call with 78.0b3 on macOS and webrender enabled, Firefox will start to cause very high CPU usage. The CPU usage grows even more when there are more than 2 people on the call.
This means:

• Main Process: 150 - 200%
• Content Process: 200%
• kernel_task (not always): 200 - 300%

Device Specs:

• MacBook Pro (15-inch, 2018)
• Processor 2,2 GHz 6-Core Intel Core i7
• Memory 16 GB 2400 MHz DDR4
• Graphics Radeon Pro 555X 4 GB / Intel UHD Graphics 630 1536 MB
• macOS 10.15.5 (19F101)

Performance Profile: https://share.firefox.dev/3dC9sUW

Bugbug thinks this bug should belong to this component, but please revert this change in case of error.

The attached profile just shows us waiting for the gpu/kernel.

Jovan, did you have gfx.webrender.compostitor set to true or false when you experienced this?

I had gfx.webredner.all set to true, does that imply gfx.webrender.compostitor? I didn't set gfx.webrender.compostitor independently. I'm now on 78.0b5 and the performance got somewhat better. It's still higher than without web render, but I still can use my machine during calls.

I think this might be caused by machine running out of VRAM. I always have an external montior connected and just the monitor already pushes the VRAM usage to 60%. Launching Firefox with webrender enabled fills the VRAM to 80% to 99%.

How are you measuring VRAM usage?

Also can you try with today's Nightly to see if things have improved?

I "measured" that with "iStat Menus". I will try Nightly and report back.

@Jovan: Can you check if you are still seeing this on Nightly?

Performance is much better now on nightly.

Thanks @Jovan! Let us know if you see further issues.