Improving canvas 2D performance by switching graphics rendering pipeline.

third_party/WebKit/Source/modules/canvas2d/CanvasRenderingContext2D.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2007 Alp Toker <alp@atoker.com>
  * Copyright (C) 2008 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2008 Dirk Schulze <krit@webkit.org>
  * Copyright (C) 2010 Torch Mobile (Beijing) Co. Ltd. All rights reserved.
  * Copyright (C) 2012, 2013 Intel Corporation. All rights reserved.
  * Copyright (C) 2013 Adobe Systems Incorporated. All rights reserved.
  *
@@ skipping 1050 matching lines @@
 }
 
 unsigned CanvasRenderingContext2D::hitRegionsCount() const
 {
     if (m_hitRegionManager)
         return m_hitRegionManager->getHitRegionsCount();
 
     return 0;
 }
 
+bool CanvasRenderingContext2D::shouldAccelerate() const
+{
+    // Simple heuristic to determine if the GPU accelerated pipeline should be
+    // used to maximize performance of 2D canvas based on past usage.
+    // The current implementation has a bias towards suggesting
+    // the use of the accelerated pipeline. The coefficients used
+    // to estimate the rendering cost of pipelines are approximate
+    // and were determined experimentally.
+
+    int numDrawPathCalls =
+        m_usageCounters.numDrawCalls[StrokePath] +
+        m_usageCounters.numDrawCalls[FillPath] +
+        m_usageCounters.numDrawCalls[FillText] +
+        m_usageCounters.numDrawCalls[StrokeText] +
+        m_usageCounters.numDrawCalls[FillRect] +
+        m_usageCounters.numDrawCalls[StrokeRect];
+
+    double acceleratedCost =
+        numDrawPathCalls * 0.004 +

[Justin Novosad, 2016/07/12 19:31:24]

These coefficients should all go in ExpensiveCAnvasHeuristicParameters, along
with comment that explaining how they were determined and any caveats.

[sebastienlc, 2016/07/13 19:51:02]

Done.

+        m_usageCounters.numGetImageDataCalls * 0.1 +
+        m_usageCounters.numDrawCalls[DrawImage] * 0.002;
+
+    double unacceleratedCost =
+        numDrawPathCalls * 0.0014 +
+        m_usageCounters.numGetImageDataCalls * 0.001 +
+        m_usageCounters.numDrawCalls[DrawImage] * 0.004;
+
+    double unacceleratedPenalty = 1.5; // greater than 1 to create a bias towards suggesting acceleration

[Justin Novosad, 2016/07/12 19:31:24]

This threshold should be in ExpensiveCanvasHeuristicParameters

[sebastienlc, 2016/07/13 19:51:02]

Done.

+    if (unacceleratedCost * unacceleratedPenalty < acceleratedCost) {
+        return false;
+    }
+    return true;
+}
+
 } // namespace blink