[Webkit-unassigned] [Bug 90019] [chromium] Add time spent painting to GPU benchmarking renderingStats() API.

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=90019





--- Comment #7 from Dave Tu <dtu at chromium.org>  2012-06-27 12:54:53 PST ---
(In reply to comment #6)
> (From update of attachment 149624 [details])
> View in context: https://bugs.webkit.org/attachment.cgi?id=149624&action=review
> 
> There's an interesting question of what this should report in skpicture/impl-side-painting mode.
> 
> These are different quantities in that case:
> - time spent painting
> - time spent rasterizing
> 
> In the regular "rasterize as you go mode" (bitmapcanvaslayertextureupdater) mode, should we just say "rasterizing time is zero"?
> 
> >> Source/WebCore/platform/graphics/chromium/cc/CCLayerTreeHost.cpp:471
> >> +    m_timeSpentPainting = monotonicallyIncreasingTime() - updateBeginTime;
> > 
> > updateLayers() covers more than just painting.  for instance, a canvas 2d layer will do a flush here, image layers will prepare texture uploads, WebGL layers will issue multisample resolves etc

So, "painting" is defined as specifically the GraphicsContext calls, and "rasterizing" includes the rest of all of that stuff?

> You're clobbering this every frame. That means we can only get the time spent painting in the last frame.
> 
> Should we instead be accumulating to this value? E.g. so we track the time we've spent paiting ever? That way we can check it twice and from the deltas, get the real time spent painting.

How can you ensure that you've checked it at adjacent frames? Maybe it should have both the total and the last one, or last ten?

> And, if thats the case, should we be concerned about numeric precision as this number gets larger?

No, double precision is far greater than the precision of the measurements, which is probably about millisecond-precision (depending on platform). But that leads to another question, are we okay with this level of precision on the individual measurements?

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