[Webkit-unassigned] [Bug 72452] [Chromium] Avoid clear and color mask operations for root layers

bugzilla-daemon at webkit.org bugzilla-daemon at webkit.org
Wed Nov 16 11:48:52 PST 2011


https://bugs.webkit.org/show_bug.cgi?id=72452





--- Comment #7 from Daniel Sievers <sievers at chromium.org>  2011-11-16 11:48:52 PST ---
(In reply to comment #4)
> View in context: https://bugs.webkit.org/attachment.cgi?id=115300&action=review
> 
> > Source/WebCore/platform/graphics/chromium/LayerRendererChromium.cpp:394
> >      m_context->clear(GraphicsContext3D::COLOR_BUFFER_BIT);
> 
> Note: depending on the gpu architecture, doing the clear may actually be a performance improvement. For example, on a tiled architecture, clearing usually permits the driver to avoid loading in the previous frame's back buffer, saving bandwidth. But obviously on others, it has the cost of writing the back buffer with pixels that will be overwritten later. Not sure which way to go, maybe we'll want to make that an option at some point.

Wait, turning off blending for the root layer and turning off masking out of the alpha channel means that it does not have to read anything from the back buffer, right? And that is the purpose of my patch, i.e. instead of writing the source alpha values, just write out 1.0, so it should always be a perf win.

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