DevTools: process trace events from background threads by a timed task.

Source/core/inspector/TimelineTraceEventProcessor.cpp

Index: Source/core/inspector/TimelineTraceEventProcessor.cpp
diff --git a/Source/core/inspector/TimelineTraceEventProcessor.cpp b/Source/core/inspector/TimelineTraceEventProcessor.cpp
index 14ea5c38852b474e65dc7606227fa41a38f8fee6..6403a5665bc5515ab3954ffc1276c0fd24761cf7 100644
--- a/Source/core/inspector/TimelineTraceEventProcessor.cpp
+++ b/Source/core/inspector/TimelineTraceEventProcessor.cpp
@@ -38,6 +38,7 @@
 #include "core/rendering/RenderImage.h"
 
 #include "wtf/CurrentTime.h"
+#include "wtf/Functional.h"
 #include "wtf/MainThread.h"
 #include "wtf/Vector.h"
 
@@ -156,6 +157,8 @@ TimelineTraceEventProcessor::TimelineTraceEventProcessor(WeakPtr<InspectorTimeli
     , m_layerId(0)
     , m_paintSetupStart(0)
     , m_paintSetupEnd(0)
+    , m_lastEventProcessingTime(0)
+    , m_processEventsTaskPosted(false)
 {
     registerHandler(InstrumentationEvents::BeginFrame, TRACE_EVENT_PHASE_INSTANT, &TimelineTraceEventProcessor::onBeginFrame);
     registerHandler(InstrumentationEvents::UpdateLayer, TRACE_EVENT_PHASE_BEGIN, &TimelineTraceEventProcessor::onUpdateLayerBegin);
@@ -220,19 +223,28 @@ void TimelineTraceEventProcessor::processEventOnAnyThread(char phase, const char
     if (it == m_handlersByType.end())
         return;
 
-    TraceEvent event(WTF::monotonicallyIncreasingTime(), phase, name, id, currentThread(), numArgs, argNames, argTypes, argValues);
+    double timestamp = WTF::monotonicallyIncreasingTime();
+    TraceEvent event(timestamp, phase, name, id, currentThread(), numArgs, argNames, argTypes, argValues);
 
     if (!isMainThread()) {
         MutexLocker locker(m_backgroundEventsMutex);
+        const float EventProcessingThresholdInSeconds = 0.1;

[pfeldman, 2013/10/17 17:19:23]

eventProcessingThresholdInSeconds

         m_backgroundEvents.append(event);
+        if (!m_processEventsTaskPosted && timestamp - m_lastEventProcessingTime > EventProcessingThresholdInSeconds) {
+            m_processEventsTaskPosted = true;
+            callOnMainThread(bind(&TimelineTraceEventProcessor::processBackgroundEventsTask, this));
+        }
         return;
     }
+    processBackgroundEvents();
     (this->*(it->value))(event);
 }
 
 void TimelineTraceEventProcessor::onBeginFrame(const TraceEvent&)
 {
-    processBackgroundEvents();
+    // We don't handle BeginFrame explicitly now, but it still implicitly helps
+    // to pump the background events regularly (as opponsed to a special task),
+    // as this is only done upon events we recognize.
 }
 
 void TimelineTraceEventProcessor::onUpdateLayerBegin(const TraceEvent& event)
@@ -283,8 +295,7 @@ void TimelineTraceEventProcessor::onRasterTaskBegin(const TraceEvent& event)
         return;
     unsigned long long layerId = event.asUInt(InstrumentationEventArguments::LayerId);
     ASSERT(layerId);
-    RefPtr<JSONObject> record = createRecord(event, TimelineRecordType::Rasterize);
-    record->setObject("data", TimelineRecordFactory::createLayerData(m_layerToNodeMap.get(layerId)));
+    RefPtr<JSONObject> record = createRecord(event, TimelineRecordType::Rasterize, TimelineRecordFactory::createLayerData(m_layerToNodeMap.get(layerId)));
     state.recordStack.addScopedRecord(record.release());
 }
 
@@ -422,6 +433,9 @@ void TimelineTraceEventProcessor::processBackgroundEvents()
     Vector<TraceEvent> events;
     {
         MutexLocker locker(m_backgroundEventsMutex);
+        m_lastEventProcessingTime = WTF::monotonicallyIncreasingTime();
+        if (m_backgroundEvents.isEmpty())
+            return;
         events.reserveCapacity(m_backgroundEvents.capacity());
         m_backgroundEvents.swap(events);
     }
@@ -433,5 +447,11 @@ void TimelineTraceEventProcessor::processBackgroundEvents()
     }
 }
 
+void TimelineTraceEventProcessor::processBackgroundEventsTask()
+{
+    m_processEventsTaskPosted = false;
+    processBackgroundEvents();
+}
+
 } // namespace WebCore