User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:58.0) Gecko/20100101 Firefox/58.0 Build ID: 20171103003834 Steps to reproduce: Put Windows into the power saver power plan. Open Firefox Nightly with WebRender enabled. Actual results: Firefox Nightly felt really sluggish on any website. Even simple websites liker Hacker News didn't feel quite smooth. Expected results: I expected Firefox to stay smooth like Servo in the same conditions.

Can you still reproduce this?

Yes, I still see a major difference in smoothness when switching to power saver. This is on both my integrated GPU (HD Graphics 530) and discrete GPU (GTX 960M), though it's much more noticeable on the integrated GPU. For me it's really easy to reproduce when trying power saving with auto scroll. According to the WebRender profiler I do still get 60 fps, though it's not completely stable, sometimes it dips to 50.

Can you give some more information about the cpu in you system?

My laptop has the Intel i7-6700HQ clocked at the default 2.6GHz which can turbo to 3.4GHz when I start scrolling. In power saver it clocks down to 0.8GHz on idle, but when I start auto-scrolling it clocks back to 2.6GHz.

A lot of things have changed in WebRender over the last while. Do you still see this problem?

It does make 60 fps according to the debugger, but feels a bit more sluggish as if the frame times aren't consistent. I looked into the debugger for the GPU times (though I'm not sure if it's the same as frame time) and weirdly enough it seemed like power saver was more consistent. Left of the red line is the balanced power plan, right is power saver.

(In reply to Jeff Muizelaar [:jrmuizel] from comment #5) > A lot of things have changed in WebRender over the last while. Do you still > see this problem? I still see this. On this site for example: https://www.forum-3dcenter.org/vbulletin/showthread.php?t=501178&page=287 It always stays at 48 fps with the power cable disconnected from my laptop (Intel HD 520) and is at a solid 60 fps, when I connect the cable. Even setting the mode to high performance on battery doesn't work.