Create libsampler as V8 sampler library.

src/libsampler/v8-sampler.h

-// Copyright 2013 the V8 project authors. All rights reserved.
+// Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef V8_PROFILER_SAMPLER_H_
-#define V8_PROFILER_SAMPLER_H_
+#ifndef V8_LIBSAMPLER_SAMPLER_H_
+#define V8_LIBSAMPLER_SAMPLER_H_
 
 #include "include/v8.h"
 
 #include "src/base/atomicops.h"
-#include "src/base/platform/time.h"
-#include "src/frames.h"
-#include "src/globals.h"
+#include "src/base/macros.h"
 
 namespace v8 {
-namespace internal {
-
-class Isolate;
 
 // ----------------------------------------------------------------------------
 // Sampler
 //
 // A sampler periodically samples the state of the VM and optionally
 // (if used for profiling) the program counter and stack pointer for
 // the thread that created it.
 
-// TickSample captures the information collected for each sample.
-struct TickSample {
-  // Internal profiling (with --prof + tools/$OS-tick-processor) wants to
-  // include the runtime function we're calling. Externally exposed tick
-  // samples don't care.
-  enum RecordCEntryFrame { kIncludeCEntryFrame, kSkipCEntryFrame };
-
-  TickSample()
-      : state(OTHER),
-        pc(NULL),
-        external_callback_entry(NULL),
-        frames_count(0),
-        has_external_callback(false),
-        update_stats(true),
-        top_frame_type(StackFrame::NONE) {}
-  void Init(Isolate* isolate, const v8::RegisterState& state,
-            RecordCEntryFrame record_c_entry_frame, bool update_stats);
-  static void GetStackSample(Isolate* isolate, const v8::RegisterState& state,
-                             RecordCEntryFrame record_c_entry_frame,
-                             void** frames, size_t frames_limit,
-                             v8::SampleInfo* sample_info);
-  StateTag state;  // The state of the VM.
-  Address pc;      // Instruction pointer.
-  union {
-    Address tos;   // Top stack value (*sp).
-    Address external_callback_entry;
-  };
-  static const unsigned kMaxFramesCountLog2 = 8;
-  static const unsigned kMaxFramesCount = (1 << kMaxFramesCountLog2) - 1;
-  Address stack[kMaxFramesCount];  // Call stack.
-  base::TimeTicks timestamp;
-  unsigned frames_count : kMaxFramesCountLog2;  // Number of captured frames.
-  bool has_external_callback : 1;
-  bool update_stats : 1;  // Whether the sample should update aggregated stats.
-  StackFrame::Type top_frame_type : 5;
-};
-
 class Sampler {
  public:
   // Initializes the Sampler support. Called once at VM startup.
   static void SetUp();
   static void TearDown();
 
   // Initialize sampler.
-  Sampler(Isolate* isolate, int interval);
+  explicit Sampler(Isolate* isolate);
   virtual ~Sampler();
 
   Isolate* isolate() const { return isolate_; }
-  int interval() const { return interval_; }
 
   // Performs stack sampling.
-  void SampleStack(const v8::RegisterState& regs);
+  // Everyone else should override this method in order to queue samples,

[fmeawad, 2016/05/02 23:14:37]

"// All Sampler implementations should override this method in order to queue
samples, the default implementation is used for testing purposes only."

[alph, 2016/05/03 18:48:07]

Can you then make the method pure virtual and create the TestSampler for the
tests?

[lpy, 2016/05/04 00:09:24]

Done.

+  // the default method is for testing functionality only.
+  virtual void SampleStack(const v8::RegisterState& regs);
 
   // Start and stop sampler.
   void Start();
   void Stop();
 
   // Whether the sampling thread should use this Sampler for CPU profiling?
   bool IsProfiling() const {
-    return base::NoBarrier_Load(&profiling_) > 0 &&
-        !base::NoBarrier_Load(&has_processing_thread_);
+    return base::NoBarrier_Load(&profiling_) > 0;
   }
   void IncreaseProfilingDepth();
   void DecreaseProfilingDepth();
 
   // Whether the sampler is running (that is, consumes resources).
   bool IsActive() const { return base::NoBarrier_Load(&active_); }
 
-  // CpuProfiler collects samples by calling DoSample directly
-  // without calling Start. To keep it working, we register the sampler
-  // with the CpuProfiler.
-  bool IsRegistered() const { return base::NoBarrier_Load(&registered_); }
-
   void DoSample();
-  // If true next sample must be initiated on the profiler event processor
-  // thread right after latest sample is processed.
-  void SetHasProcessingThread(bool value) {
-    base::NoBarrier_Store(&has_processing_thread_, value);
-  }
 
   // Used in tests to make sure that stack sampling is performed.
   unsigned js_sample_count() const { return js_sample_count_; }
   unsigned external_sample_count() const { return external_sample_count_; }
   void StartCountingSamples() {
     js_sample_count_ = 0;
     external_sample_count_ = 0;
     is_counting_samples_ = true;
   }
 
   class PlatformData;
   PlatformData* platform_data() const { return data_; }
 
- protected:
-  // This method is called for each sampling period with the current
-  // program counter.
-  virtual void Tick(TickSample* sample) = 0;
-
  private:
   void SetActive(bool value) { base::NoBarrier_Store(&active_, value); }
 
-  void SetRegistered(bool value) { base::NoBarrier_Store(&registered_, value); }
-
   Isolate* isolate_;
-  const int interval_;
   base::Atomic32 profiling_;
-  base::Atomic32 has_processing_thread_;
   base::Atomic32 active_;
-  base::Atomic32 registered_;
   PlatformData* data_;  // Platform specific data.
   // Counts stack samples taken in various VM states.
   bool is_counting_samples_;
   unsigned js_sample_count_;
   unsigned external_sample_count_;
   DISALLOW_IMPLICIT_CONSTRUCTORS(Sampler);
 };
 
-
-#if defined(USE_SIMULATOR)
-class SimulatorHelper : AllStatic {
- public:
-  // Returns true if register values were successfully retrieved
-  // from the simulator, otherwise returns false.
-  static bool FillRegisters(Isolate* isolate, v8::RegisterState* state);
-};
-#endif  // USE_SIMULATOR
-
-
-}  // namespace internal
 }  // namespace v8
 
-#endif  // V8_PROFILER_SAMPLER_H_
+#endif  // V8_LIBSAMPLER_SAMPLER_H_