Fixing laggy chrome on a multitude of accelerated canvases

third_party/WebKit/Source/core/html/HTMLCanvasElement.h

 /*
  * Copyright (C) 2004, 2006, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alp Toker <alp@atoker.com>
  * Copyright (C) 2010 Torch Mobile (Beijing) Co. Ltd. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
@@ skipping 151 matching lines @@
     // ImageBitmapSource implementation
     IntSize bitmapSourceSize() const override;
     ScriptPromise createImageBitmap(ScriptState*, EventTarget&, int sx, int sy, int sw, int sh, ExceptionState&) override;
 
     DECLARE_VIRTUAL_TRACE();
 
     void createImageBufferUsingSurfaceForTesting(PassOwnPtr<ImageBufferSurface>);
 
     static void registerRenderingContextFactory(PassOwnPtr<CanvasRenderingContextFactory>);
     void updateExternallyAllocatedMemory() const;
+    static void updateTotalMemoryForAcceleratedCanvases(intptr_t diffFromCurrAllocatedMemory);
 
     void styleDidChange(const ComputedStyle* oldStyle, const ComputedStyle& newStyle);
 
 protected:
     void didMoveToNewDocument(Document& oldDocument) override;
 
 private:
     explicit HTMLCanvasElement(Document&);
 
     using ContextFactoryVector = Vector<OwnPtr<CanvasRenderingContextFactory>>;
@@ skipping 20 matching lines @@
     String toDataURLInternal(const String& mimeType, const double& quality, SourceDrawingBuffer) const;
 
     IntSize m_size;
 
     OwnPtrWillBeMember<CanvasRenderingContext> m_context;
 
     bool m_ignoreReset;
     FloatRect m_dirtyRect;
 
     mutable intptr_t m_externallyAllocatedMemory;
-
+    static intptr_t s_totalMemoryForAcceleratedCanvases;

[danakj, 2015/11/30 23:07:03]

I would maybe suggest tying this to a single blink (or canvas) instance rather
than the whole process. There may be multiple tabs in the same process, that are
all visible. And usually you'd want them to each have their own budget, probably
(compositors would). Maybe junov has thoughts here.

[xlai (Olivia), 2015/12/01 21:50:25]

I did some experiments and confirmed that this variable is keeping track of each
browser tab's own usage separately; so it's not a "total" computation of all
tabs. 

[danakj, 2015/12/01 22:13:35]

Chrome will put tabs in different processes in different ways, depending how you
launched the tab (from a js link = same process) and on diff platforms (on
android almost all tabs share one process.. maybe they all do)

+    
     bool m_originClean;
 
     // It prevents HTMLCanvasElement::buffer() from continuously re-attempting to allocate an imageBuffer
     // after the first attempt failed.
     mutable bool m_didFailToCreateImageBuffer;
     bool m_imageBufferIsClear;
     OwnPtr<ImageBuffer> m_imageBuffer;
 
     mutable RefPtr<Image> m_copiedImage; // FIXME: This is temporary for platforms that have to copy the image buffer to render (and for CSSCanvasValue).
 };
 
 } // namespace blink
 
 #endif // HTMLCanvasElement_h