Open Bug 1793982 Opened 2 years ago Updated 2 years ago

A lot of time spent reading back from 2d canvas on google maps on windows

Categories

(Core :: Graphics: Canvas2D, defect, P3)

Product:
Core
Component:
Graphics: Canvas2D
Type:
defect

Tracking

()

People

(Reporter: nical, Unassigned)

References

(Blocks 1 open bug)

Details

It looks like this is at the intersection between canvas2D and WebGL.

When profiling google maps, we found that on Windows (but not on Linux and Mac) a lot of time was spent on the content process main thread reading back a 2D canvas in GetDataSurface. We didn't delve into what exactly was causing this but our initial assumption is that a D2D canvas is used to draw some things and is read back in order to be uploaded into a WebGL texture for use in the main map rendering logic.

It would be good to confirm that, and see whether we should:

  • default to non-accelerated canvas in this specific case via a heuristic,
  • or support transparently copying a GPU-side canvas2d texture into a WebGL texture.
Summary: A lot of time spent reading back from 2d canvas on google maps → A lot of time spent reading back from 2d canvas on google maps on windows

At Nical's request, here's a profile: https://share.firefox.dev/3T3WQKJ

The getImageData chunk is very visible when using the flamegraph view on the content process main thread.

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