Since it may be relevant, my hardware specs:

Windows 10 x64 (latest build)
Haswell-E CPU
GeForce GTX 1080, latest drivers. Also reproduces on a 980ti.

I've heard other people who play this browser game complain about this lag before, but previously did not experience. Something (a Chrome update, a driver update, an OS update?) made this regress for me.

I'm not able to reproduce the problem on my (beefy) macbook pro. I thought the difference might be that we've enabled GPU acceleration on Mac (windows is WIP), but force disabling via about:flags still gets 60 fps. Maybe a Window specific issue?

Optimistically labelling this as Compositing and Paint with the expectation that the bugs would be in those areas.

Here's a self contained version of the dropbox link for permanence in the bug tracker. :)

I don't see much variance in frame rate on OS X unless I'm interacting with multiple tabs at once. Then we get hit pretty bad by the serialization the GPU process imposes where one tab doing a very large raster will delay all the other tabs.

I think this might be more of the same "windows does vsync really badly" bugs (ex. issue 422000), this doesn't look like paint or compositing per the thread on twitter. It's either a problem in the way we issue commands to the commands in the gpu process, or a problem with our scheduling.

The canvas is being drawn to with:

        canvas.clearRect(0, 0, 320, 320);
        canvas.fillStyle = "black";
        canvas.fillRect(x - 2, 0, 4, 320);

kg@luminance.org if you resize the window after starting the animation do the frame drops go away?

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Resizing window doesn't appear to help. I'll do some more testing a bit later, and try to get a detailed trace file for you.

Here's a trace from the game that has this issue with all tracing categories checked.

Thanks for the trace. Looks like the main thread is spending a lot of time waiting for something from the GPU process. Sunny, could you take a look?

Here's a similar all tracing categories trace for the reduced test case in this bug; it may be easier to investigate it since less is going on. The game may be affected by two different issues at once (but one of them is definitely this problem).

Deleted: trace_raf-test.json.gz 7.4 MB

trace_raf-test.json.gz 7.4 MB Download

kg@: could you please try the canary channel,
https://www.google.com/chrome/browser/canary.html

I can repro the bug on stable version, but not on canary. Thanks.

My isolated repro does not cause lag issues in Canary anymore, so I can confirm that's fixed. The other (CSS/layout related as well?) lag issue in this game still reproduces, so I'll file a new bug for it. Thanks.

\o/ Marking fixed. Please reopen if I'm misunderstanding.