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 2cef421f5175ab45e4f854802b8eb0fb4dc3edee..56934cc883e6d4f6654caf80756609e09561cfe0 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 {
@@ -156,11 +155,11 @@ 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).

[Jakob Kummerow, 2012/09/04 11:25:18]

long line.
Also, can you put in an ASSERT that makes sure this rule is not violated?

+  INLINE(TickSample* StartTickSampleEvent());
+  INLINE(void FinishTickSampleEvent()) { ticks_buffer_is_empty_ = false; }
 
  private:
   union CodeEventsContainer {
@@ -172,7 +171,7 @@ 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));
@@ -183,7 +182,8 @@ class ProfilerEventsProcessor : public Thread {
   // Sampling interval in microseconds.
   const int interval_in_useconds_;
   UnboundQueue<CodeEventsContainer> events_buffer_;
-  SamplingCircularQueue ticks_buffer_;
+  TickSampleEventRecord ticks_buffer_;
+  bool ticks_buffer_is_empty_;
   UnboundQueue<TickSampleEventRecord> ticks_from_vm_buffer_;
   unsigned enqueue_order_;
 };
@@ -222,7 +222,9 @@ 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).

[Jakob Kummerow, 2012/09/04 11:25:18]

long line

+  static TickSample* StartTickSampleEvent(Isolate* isolate);
+  static void FinishTickSampleEvent(Isolate* isolate);
 
   // Must be called via PROFILE macro, otherwise will crash when
   // profiling is not enabled.