cc: Improve texture per second calculation and overhead

cc/ThrottledTextureUploader.cpp

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 #include "ThrottledTextureUploader.h"
 
 #include "Extensions3DChromium.h"
 #include "TraceEvent.h"
 #include <algorithm>
 #include <public/Platform.h>
 #include <public/WebGraphicsContext3D.h>
 #include <vector>
 
 namespace {
 
 // How many previous uploads to use when predicting future throughput.
-static const size_t uploadHistorySize = 100;
+static const size_t uploadHistorySizeMax = 1000;
+static const size_t uploadHistorySizeInitial = 100;
 
 // Global estimated number of textures per second to maintain estimates across
 // subsequent instances of ThrottledTextureUploader.
 // More than one thread will not access this variable, so we do not need to synchronize access.
 static double estimatedTexturesPerSecondGlobal = 48.0 * 60.0;
 
 } // anonymous namespace
 
 namespace cc {
 
@@ skipping 51 matching lines @@
     m_isNonBlocking = true;
 }
 
 bool ThrottledTextureUploader::Query::isNonBlocking()
 {
     return m_isNonBlocking;
 }
 
 ThrottledTextureUploader::ThrottledTextureUploader(WebKit::WebGraphicsContext3D* context)
     : m_context(context)
-    , m_texturesPerSecondHistory(uploadHistorySize, estimatedTexturesPerSecondGlobal)
+    , m_texturesPerSecondHistory(uploadHistorySizeInitial,
+                                 estimatedTexturesPerSecondGlobal)
     , m_numBlockingTextureUploads(0)
 {
 }
 
 ThrottledTextureUploader::~ThrottledTextureUploader()
 {
 }
 
 size_t ThrottledTextureUploader::numBlockingUploads()
 {
@@ skipping 12 matching lines @@
         it->get()->markAsNonBlocking();
     }
 
     ASSERT(!m_numBlockingTextureUploads);
 }
 
 double ThrottledTextureUploader::estimatedTexturesPerSecond()
 {
     processQueries();
 
-    // The history should never be empty because we initialize all elements with an estimate.
-    ASSERT(m_texturesPerSecondHistory.size() == uploadHistorySize);
-
-    // Sort the history and use the median as our estimate.
+    // Sort the history and use the 3/4 median as our optimistic estimate.
     std::vector<double> sortedHistory(m_texturesPerSecondHistory.begin(),
                                       m_texturesPerSecondHistory.end());
     std::sort(sortedHistory.begin(), sortedHistory.end());

[reveman, 2012/10/11 17:59:46]

with the history now relatively large, does it makes sense to do something a bit
smarter than sorting every time estimatedTexturesPerSecond() is called? seems
like a balanced binary tree is just what we need here?

 
-    estimatedTexturesPerSecondGlobal = sortedHistory[sortedHistory.size() * 2 / 3];
+    estimatedTexturesPerSecondGlobal = sortedHistory[sortedHistory.size() * 3 / 4];
     TRACE_COUNTER1("cc", "estimatedTexturesPerSecond", estimatedTexturesPerSecondGlobal);
     return estimatedTexturesPerSecondGlobal;
 }
 
 void ThrottledTextureUploader::beginQuery()
 {
     processQueries();
 
     if (m_availableQueries.isEmpty())
       m_availableQueries.append(Query::create(m_context));
@@ skipping 29 matching lines @@
             break;
 
         unsigned usElapsed = m_pendingQueries.first()->value();
         WebKit::Platform::current()->histogramCustomCounts("Renderer4.TextureGpuUploadTimeUS", usElapsed, 0, 100000, 50);
 
         if (!m_pendingQueries.first()->isNonBlocking())
             m_numBlockingTextureUploads--;
 
         // Remove the oldest values from our history and insert the new one
         double texturesPerSecond = 1.0 / (usElapsed * 1e-6);
-        m_texturesPerSecondHistory.pop_back();
+        if (m_texturesPerSecondHistory.size() >= uploadHistorySizeMax)
+            m_texturesPerSecondHistory.pop_back();
         m_texturesPerSecondHistory.push_front(texturesPerSecond);
 
         m_availableQueries.append(m_pendingQueries.takeFirst());
     }
 }
 
 }