I saw 52% vs 15% usage on Dzmitry's laptop.

Jeff, which Intel GPU and what OS?

This was on Win10 with a relatively recent embedded intel gpu. Kvark can fill in the details.

I'm seeing this here too on Win10 1903 with an Intel UHD 620. When playing a VP9 Youtube video with 1080p/60fps I get 70-75% "3D" usage with WebRender enabled compared to 25-30% with WebRender disabled.

Intel Graphics 630 GPU
Windows 10 updated ~ month ago.

Just tested with webrender and direct composition enabled on windows + intel (0x191d skylake) running on battery:

• WR enabled: 81% GPU usage, 5.5W Package power draw
• WR disabled: 48% GPU usage, 4W Package power draw

Nical - can you say more about how you tested this? Are you still seeing worse numbers with WR enabled?

FWIW, with windowed youtube on a surface GO (gen9 at 1800x1200) during a windows update in the background5

• WR enabled: 4% GPU usage, 1.6W package
• WR disabled: 5% GPU usage, 1.8W package

In full screen, with double buffering turned off to match release I see:

• WR enabled: 10% GPU usage, 1.8-2W package
• WR disabled: 30% GPU usage, 3.3W package

Dzmitry can you check how the situation looks on your machine with WR off and on. Make sure you set gfx.direct3d11.use-double-buffering=false so that the situation more accurately matches release.

WR + DC windowed youtube: GPU 90%, CPU 13%, Package power 14W
WR + DC full screen youtube: GPU 93%, CPU 14%, Package power 20W

WR no DC windowed youtube: GPU 80%, CPU 19%, Package power 9W
WR no DC full screen youtube: GPU 89%, CPU 19%, Package power 9W

Advanced layers windowed youtube: GPU 75%, CPU 13%, Package power 7W
Advanced layers full screen youtube: GPU 83%, CPU 12%, Package power 8W

Display resolution is 3840x2160 this is an optimus laptop (nvidia + intel), firefox is using the intel chip.
The task manager attributes the majority of the GPU work to the DWM (60% DWM vs 20% to firefox).
The video is software-decoded.

Edit: So the new scene indicator was enabled (but it's not visible one windows). and it was causing a ton of blended pixels. After disabling it, the package power consumption is around 7.5W.

Tested on a large 4K window youtube with "Intel(R) UHD Graphics 630". Set "gfx.direct3d11.use-double-buffering=false".
Numbers are taken from the Intel Power Gadget.

Edit: fixed non-WR numbers

WR DC: GPU 13-20%, CPU 16-20%, Power 5W
no-WR: GPU 65%, CPU 15-20%, Power 5.2W

Edit: full-screen video numbers

WR DC: GPU 60+%, CPU 17-20%, Power 8W+
no-WR: GPU 65%, CPU 15-20%, Power 5.5W+

Power measurements jump quite a bit, so the lower bound may not be entirely accurate. Overall, seems very close.

It looks like remaining differences here are probably because of higher CPU usage. That's being addressed elsewhere. The bulk of the problem has been fixed by DC and bug 1579235