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      1 // Copyright 2013 the V8 project authors. All rights reserved.
      2 // Redistribution and use in source and binary forms, with or without
      3 // modification, are permitted provided that the following conditions are
      4 // met:
      5 //
      6 //     * Redistributions of source code must retain the above copyright
      7 //       notice, this list of conditions and the following disclaimer.
      8 //     * Redistributions in binary form must reproduce the above
      9 //       copyright notice, this list of conditions and the following
     10 //       disclaimer in the documentation and/or other materials provided
     11 //       with the distribution.
     12 //     * Neither the name of Google Inc. nor the names of its
     13 //       contributors may be used to endorse or promote products derived
     14 //       from this software without specific prior written permission.
     15 //
     16 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     17 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     18 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
     19 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
     20 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     21 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
     22 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     23 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     24 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     25 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     26 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     27 
     28 #ifndef V8_SAMPLER_H_
     29 #define V8_SAMPLER_H_
     30 
     31 #include "atomicops.h"
     32 #include "frames.h"
     33 #include "v8globals.h"
     34 
     35 namespace v8 {
     36 namespace internal {
     37 
     38 class Isolate;
     39 
     40 // ----------------------------------------------------------------------------
     41 // Sampler
     42 //
     43 // A sampler periodically samples the state of the VM and optionally
     44 // (if used for profiling) the program counter and stack pointer for
     45 // the thread that created it.
     46 
     47 struct RegisterState {
     48   RegisterState() : pc(NULL), sp(NULL), fp(NULL) {}
     49   Address pc;      // Instruction pointer.
     50   Address sp;      // Stack pointer.
     51   Address fp;      // Frame pointer.
     52 };
     53 
     54 // TickSample captures the information collected for each sample.
     55 struct TickSample {
     56   TickSample()
     57       : state(OTHER),
     58         pc(NULL),
     59         external_callback(NULL),
     60         frames_count(0),
     61         has_external_callback(false),
     62         top_frame_type(StackFrame::NONE) {}
     63   void Init(Isolate* isolate, const RegisterState& state);
     64   StateTag state;  // The state of the VM.
     65   Address pc;      // Instruction pointer.
     66   union {
     67     Address tos;   // Top stack value (*sp).
     68     Address external_callback;
     69   };
     70   static const int kMaxFramesCount = 64;
     71   Address stack[kMaxFramesCount];  // Call stack.
     72   int frames_count : 8;  // Number of captured frames.
     73   bool has_external_callback : 1;
     74   StackFrame::Type top_frame_type : 4;
     75 };
     76 
     77 class Sampler {
     78  public:
     79   // Initializes the Sampler support. Called once at VM startup.
     80   static void SetUp();
     81   static void TearDown();
     82 
     83   // Initialize sampler.
     84   Sampler(Isolate* isolate, int interval);
     85   virtual ~Sampler();
     86 
     87   Isolate* isolate() const { return isolate_; }
     88   int interval() const { return interval_; }
     89 
     90   // Performs stack sampling.
     91   void SampleStack(const RegisterState& regs);
     92 
     93   // Start and stop sampler.
     94   void Start();
     95   void Stop();
     96 
     97   // Is the sampler used for profiling?
     98   bool IsProfiling() const { return NoBarrier_Load(&profiling_) > 0; }
     99   void IncreaseProfilingDepth() { NoBarrier_AtomicIncrement(&profiling_, 1); }
    100   void DecreaseProfilingDepth() { NoBarrier_AtomicIncrement(&profiling_, -1); }
    101 
    102   // Whether the sampler is running (that is, consumes resources).
    103   bool IsActive() const { return NoBarrier_Load(&active_); }
    104 
    105   // Used in tests to make sure that stack sampling is performed.
    106   unsigned js_and_external_sample_count() const {
    107     return js_and_external_sample_count_;
    108   }
    109   void StartCountingSamples() {
    110       is_counting_samples_ = true;
    111       js_and_external_sample_count_ = 0;
    112   }
    113 
    114   class PlatformData;
    115   PlatformData* platform_data() const { return data_; }
    116 
    117  protected:
    118   // This method is called for each sampling period with the current
    119   // program counter.
    120   virtual void Tick(TickSample* sample) = 0;
    121 
    122  private:
    123   void SetActive(bool value) { NoBarrier_Store(&active_, value); }
    124 
    125   Isolate* isolate_;
    126   const int interval_;
    127   Atomic32 profiling_;
    128   Atomic32 active_;
    129   PlatformData* data_;  // Platform specific data.
    130   bool is_counting_samples_;
    131   // Counts stack samples taken in JS VM state.
    132   unsigned js_and_external_sample_count_;
    133   DISALLOW_IMPLICIT_CONSTRUCTORS(Sampler);
    134 };
    135 
    136 
    137 } }  // namespace v8::internal
    138 
    139 #endif  // V8_SAMPLER_H_
    140