Adding flow traces for blink scheduler events

Source/platform/scheduler/Scheduler.cpp

Index: Source/platform/scheduler/Scheduler.cpp
diff --git a/Source/platform/scheduler/Scheduler.cpp b/Source/platform/scheduler/Scheduler.cpp
index fb331ac6e3766aad23db042059ad0c43b549bb18..2805aa4b37953a315b14d422c637f33ae9a0beeb 100644
--- a/Source/platform/scheduler/Scheduler.cpp
+++ b/Source/platform/scheduler/Scheduler.cpp
@@ -73,8 +73,8 @@ public:
 class Scheduler::MainThreadPendingTaskRunner : public WebThread::Task {
 public:
     MainThreadPendingTaskRunner(
-        const Scheduler::Task& task, const TraceLocation& location)
-        : m_task(task, location)
+        const Scheduler::Task& task, const TraceLocation& location, const char * name, int flowTraceID)

[Sami, 2014/08/29 14:50:25]

No space before "*".

[picksi1, 2014/09/01 11:06:51]

Done.

+        : m_task(task, location, name, flowTraceID)
     {
         ASSERT(Scheduler::shared());
     }
@@ -90,7 +90,7 @@ public:
         m_task.run();
     }
 
-    Scheduler::TracedTask m_task;
+    TracedTask m_task;
 };
 
 Scheduler* Scheduler::s_sharedScheduler = nullptr;
@@ -117,6 +117,12 @@ Scheduler::Scheduler()
     , m_highPriorityTaskCount(0)
     , m_highPriorityTaskRunnerPosted(false)
 {
+    // Start trace ID off as 'this' to keep multiple instances of the scheduler
+    // having different(-ish) unique flow tracing IDs. Keep compiler happy
+    // by casting to a pointer and then to an integer.
+    intptr_t thisAsPointer = reinterpret_cast<intptr_t>(this);

[Sami, 2014/08/29 14:50:25]

Maybe it's just me, but I think this is a little verbose -- I'd just write the
conversion into a single line in the member initialization.

[picksi1, 2014/09/01 11:06:51]

Done.

+    int thisAsInteger = static_cast<int>(thisAsPointer);
+    m_nextFlowTraceID = thisAsInteger;
 }
 
 Scheduler::~Scheduler()
@@ -126,31 +132,40 @@ Scheduler::~Scheduler()
     }
 }
 
+int Scheduler::generateFlowTraceID()
+{
+    return atomicIncrement(&m_nextFlowTraceID);
+}
+
 void Scheduler::scheduleIdleTask(const TraceLocation& location, const IdleTask& idleTask)
 {
     // TODO: send a real allottedTime here.
     m_mainThread->postTask(new MainThreadIdleTaskAdapter(idleTask, 0, location));
 }
 
+void Scheduler::postAsHighPriorityTask(const TraceLocation& location, const Task& task, const char * traceName)

[Sami, 2014/08/29 14:50:25]

nit: postHighPriorityTask to match the wording of the other functions.

No space before "*".

[picksi1, 2014/09/01 11:06:51]

I'd named this differently on purpose as it is an internal (i.e. private)
function and has different parameters from the other PostTask functions (which
all take a location and a task).

+{
+    Locker<Mutex> lock(m_pendingTasksMutex);
+
+    TracedTask tracedTask = TracedTask(task, location, traceName, generateFlowTraceID());
+    m_pendingHighPriorityTasks.append(tracedTask);
+    atomicIncrement(&m_highPriorityTaskCount);
+    maybePostMainThreadPendingHighPriorityTaskRunner();
+}
+
 void Scheduler::postTask(const TraceLocation& location, const Task& task)
 {
-    m_mainThread->postTask(new MainThreadPendingTaskRunner(task, location));
+    m_mainThread->postTask(new MainThreadPendingTaskRunner(task, location, "Scheduler::MainThreadTask", generateFlowTraceID()));
 }
 
 void Scheduler::postInputTask(const TraceLocation& location, const Task& task)
 {
-    Locker<Mutex> lock(m_pendingTasksMutex);
-    m_pendingHighPriorityTasks.append(TracedTask(task, location));
-    atomicIncrement(&m_highPriorityTaskCount);
-    maybePostMainThreadPendingHighPriorityTaskRunner();
+    postAsHighPriorityTask(location, task, "Scheduler::InputTask");
 }
 
 void Scheduler::postCompositorTask(const TraceLocation& location, const Task& task)
 {
-    Locker<Mutex> lock(m_pendingTasksMutex);
-    m_pendingHighPriorityTasks.append(TracedTask(task, location));
-    atomicIncrement(&m_highPriorityTaskCount);
-    maybePostMainThreadPendingHighPriorityTaskRunner();
+    postAsHighPriorityTask(location, task, "Scheduler::CompositorTask");
 }
 
 void Scheduler::maybePostMainThreadPendingHighPriorityTaskRunner()
@@ -256,12 +271,4 @@ bool Scheduler::hasPendingHighPriorityWork() const
     return acquireLoad(&m_highPriorityTaskCount) != 0;
 }
 
-void Scheduler::TracedTask::run()
-{
-    TRACE_EVENT2("blink", "TracedTask::run",
-        "src_file", m_location.fileName(),
-        "src_func", m_location.functionName());
-    m_task();
-}
-
 } // namespace blink