Replacing circular queue by single buffer in CPU Profiler.

src/cpu-profiler.h

Index: src/cpu-profiler.h
diff --git a/src/cpu-profiler.h b/src/cpu-profiler.h
index d335dedc5cb765f2f2a66eb1e451207c44d749f3..7e6b5d4852eea701de7550c1f0157873a80b8f32 100644
--- a/src/cpu-profiler.h
+++ b/src/cpu-profiler.h
@@ -30,7 +30,6 @@
 
 #include "allocation.h"
 #include "atomicops.h"
-#include "circular-queue.h"
 #include "unbound-queue.h"
 
 namespace v8 {
@@ -158,11 +157,12 @@ class ProfilerEventsProcessor : public Thread {
   // Puts current stack into tick sample events buffer.
   void AddCurrentStack();
 
-  // Tick sample events are filled directly in the buffer of the circular
-  // queue (because the structure is of fixed width, but usually not all
-  // stack frame entries are filled.) This method returns a pointer to the
-  // next record of the buffer.
-  INLINE(TickSample* TickSampleEvent());
+  // StartTickSampleEvent returns a pointer only if the ticks_buffer_ is empty,
+  // FinishTickSampleEvent marks the ticks_buffer_ as filled.
+  // Finish should be called only after successful Start (returning non-NULL
+  // pointer).
+  INLINE(TickSample* StartTickSampleEvent());
+  INLINE(void FinishTickSampleEvent());
 
  private:
   union CodeEventsContainer {
@@ -174,7 +174,7 @@ class ProfilerEventsProcessor : public Thread {
 
   // Called from events processing thread (Run() method.)
   bool ProcessCodeEvent(unsigned* dequeue_order);
-  bool ProcessTicks(int64_t stop_time, unsigned dequeue_order);
+  bool ProcessTicks(unsigned dequeue_order);
   void ProcessEventsQueue(int64_t stop_time, unsigned* dequeue_order);
 
   INLINE(static bool FilterOutCodeCreateEvent(Logger::LogEventsAndTags tag));
@@ -185,7 +185,9 @@ class ProfilerEventsProcessor : public Thread {
   // Sampling period in microseconds.
   const int period_in_useconds_;
   UnboundQueue<CodeEventsContainer> events_buffer_;
-  SamplingCircularQueue ticks_buffer_;
+  TickSampleEventRecord ticks_buffer_;
+  bool ticks_buffer_is_empty_;
+  bool ticks_buffer_is_initialized_;
   UnboundQueue<TickSampleEventRecord> ticks_from_vm_buffer_;
   unsigned enqueue_order_;
 };
@@ -224,7 +226,10 @@ class CpuProfiler {
   static bool HasDetachedProfiles();
 
   // Invoked from stack sampler (thread or signal handler.)
-  static TickSample* TickSampleEvent(Isolate* isolate);
+  // Finish should be called only after successful Start (returning non-NULL
+  // pointer).
+  static TickSample* StartTickSampleEvent(Isolate* isolate);
+  static void FinishTickSampleEvent(Isolate* isolate);
 
   // Must be called via PROFILE macro, otherwise will crash when
   // profiling is not enabled.