[profiler] Implement POC Sampling Heap Profiler

src/profiler/sampling-heap-profiler.h

Index: src/profiler/sampling-heap-profiler.h
diff --git a/src/profiler/sampling-heap-profiler.h b/src/profiler/sampling-heap-profiler.h
new file mode 100644
index 0000000000000000000000000000000000000000..d9b88e9b861bdaa2d135f53b056f301a6f543096
--- /dev/null
+++ b/src/profiler/sampling-heap-profiler.h
@@ -0,0 +1,135 @@
+// Copyright 2015 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_SAMPLING_HEAP_PROFILER_H_
+#define V8_PROFILER_SAMPLING_HEAP_PROFILER_H_
+
+#include <deque>
+#include <map>
+#include <set>
+#include "include/v8-profiler.h"
+#include "src/heap/heap.h"
+#include "src/profiler/strings-storage.h"
+
+namespace v8 {
+
+namespace base {
+class RandomNumberGenerator;
+}
+
+namespace internal {
+
+
+class AllocationProfile : public v8::AllocationProfile {
+ public:
+  AllocationProfile() : nodes_() {}
+
+  Node* GetRootNode() override {
+    return nodes_.size() == 0 ? nullptr : &nodes_.front();
+  }
+
+  std::deque<Node>& nodes() { return nodes_; }
+
+ private:
+  std::deque<Node> nodes_;
+
+  DISALLOW_COPY_AND_ASSIGN(AllocationProfile);
+};
+
+class SamplingHeapProfiler : public InlineAllocationObserver {
+ public:
+  SamplingHeapProfiler(Heap* heap, StringsStorage* names, uint64_t rate,
+                       int stack_depth);
+  ~SamplingHeapProfiler();
+
+  v8::AllocationProfile* GetAllocationProfile();
+
+  void Step(int bytes_allocated, Address soon_object, size_t size) override;
+  intptr_t GetNextStepSize() override {
+    return GetNextSampleInterval(random_, rate_);
+  }
+
+  StringsStorage* names() const { return names_; }
+
+  class FunctionInfo {
+   public:
+    FunctionInfo(SharedFunctionInfo* shared, StringsStorage* names);
+    explicit FunctionInfo(const char* name)
+        : name_(name),
+          script_name_(""),
+          script_id_(v8::UnboundScript::kNoScriptId),
+          start_position_(0) {}
+
+    const char* get_name() const { return name_; }
+    const char* get_script_name() const { return script_name_; }
+    int get_script_id() const { return script_id_; }
+    int get_start_position() const { return start_position_; }
+
+   private:
+    const char* const name_;
+    const char* script_name_;
+    int script_id_;
+    const int start_position_;
+  };
+
+  class SampledAllocation {
+   public:
+    SampledAllocation(SamplingHeapProfiler* sampling_heap_profiler,
+                      Isolate* isolate, Local<Value> local, size_t size,
+                      int max_frames);
+    ~SampledAllocation() {
+      for (auto info : stack_) {
+        delete info;
+      }
+      global_.Reset();  // drop the reference.
+    }
+    size_t get_size() const { return size_; }
+    const std::vector<FunctionInfo*>& get_stack() const { return stack_; }
+
+   private:
+    static void OnWeakCallback(const WeakCallbackInfo<SampledAllocation>& data);
+
+    SamplingHeapProfiler* const sampling_heap_profiler_;
+    Global<Value> global_;
+    std::vector<FunctionInfo*> stack_;
+    const size_t size_;
+
+    DISALLOW_COPY_AND_ASSIGN(SampledAllocation);
+  };
+
+ private:
+  using Node = v8::AllocationProfile::Node;
+
+  Heap* heap() const { return heap_; }
+
+  void SampleObject(Address soon_object, size_t size);
+
+  static intptr_t GetNextSampleInterval(base::RandomNumberGenerator* random,
+                                        uint64_t rate);
+
+  // Methods that construct v8::AllocationProfile.
+  Node* AddStack(AllocationProfile* profile,
+                 const std::map<int, Script*>& scripts,
+                 const std::vector<FunctionInfo*>& stack);
+  Node* FindOrAddChildNode(AllocationProfile* profile,
+                           const std::map<int, Script*>& scripts, Node* parent,
+                           FunctionInfo* function_info);
+  Node* AllocateNode(AllocationProfile* profile,
+                     const std::map<int, Script*>& scripts,
+                     FunctionInfo* function_info);
+
+  Isolate* const isolate_;
+  Heap* const heap_;
+  base::RandomNumberGenerator* const random_;
+  StringsStorage* const names_;
+  std::set<SampledAllocation*> samples_;
+  const uint64_t rate_;
+  const int stack_depth_;
+};
+
+
+}  // namespace internal
+}  // namespace v8
+
+#endif  // V8_PROFILER_SAMPLING_HEAP_PROFILER_H_