src/v8/src/profiler/sampling-heap-profiler.h

// 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 <memory>
#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 SamplingAllocationObserver;

class AllocationProfile : public v8::AllocationProfile {
 public:
  AllocationProfile() : nodes_() {}

  v8::AllocationProfile::Node* GetRootNode() override {
    return nodes_.size() == 0 ? nullptr : &nodes_.front();
  }

  std::deque<v8::AllocationProfile::Node>& nodes() { return nodes_; }

 private:
  std::deque<v8::AllocationProfile::Node> nodes_;

  DISALLOW_COPY_AND_ASSIGN(AllocationProfile);
};

class SamplingHeapProfiler {
 public:
  SamplingHeapProfiler(Heap* heap, StringsStorage* names, uint64_t rate,
                       int stack_depth, v8::HeapProfiler::SamplingFlags flags);
  ~SamplingHeapProfiler();

  v8::AllocationProfile* GetAllocationProfile();

  StringsStorage* names() const { return names_; }

  class AllocationNode;

  struct Sample {
   public:
    Sample(size_t size_, AllocationNode* owner_, Local<Value> local_,
           SamplingHeapProfiler* profiler_)
        : size(size_),
          owner(owner_),
          global(Global<Value>(
              reinterpret_cast<v8::Isolate*>(profiler_->isolate_), local_)),
          profiler(profiler_) {}
    ~Sample() { global.Reset(); }
    const size_t size;
    AllocationNode* const owner;
    Global<Value> global;
    SamplingHeapProfiler* const profiler;

   private:
    DISALLOW_COPY_AND_ASSIGN(Sample);
  };

  class AllocationNode {
   public:
    AllocationNode(AllocationNode* parent, const char* name, int script_id,
                   int start_position)
        : parent_(parent),
          script_id_(script_id),
          script_position_(start_position),
          name_(name),
          pinned_(false) {}
    ~AllocationNode() {
      for (auto child : children_) {
        delete child.second;
      }
    }

   private:
    typedef uint64_t FunctionId;
    static FunctionId function_id(int script_id, int start_position,
                                  const char* name) {
      // script_id == kNoScriptId case:
      //   Use function name pointer as an id. Names derived from VM state
      //   must not collide with the builtin names. The least significant bit
      //   of the id is set to 1.
      if (script_id == v8::UnboundScript::kNoScriptId) {
        return reinterpret_cast<intptr_t>(name) | 1;
      }
      // script_id != kNoScriptId case:
      //   Use script_id, start_position pair to uniquelly identify the node.
      //   The least significant bit of the id is set to 0.
      DCHECK(static_cast<unsigned>(start_position) < (1u << 31));
      return (static_cast<uint64_t>(script_id) << 32) + (start_position << 1);
    }
    AllocationNode* FindOrAddChildNode(const char* name, int script_id,
                                       int start_position);
    // TODO(alph): make use of unordered_map's here. Pay attention to
    // iterator invalidation during TranslateAllocationNode.
    std::map<size_t, unsigned int> allocations_;
    std::map<FunctionId, AllocationNode*> children_;
    AllocationNode* const parent_;
    const int script_id_;
    const int script_position_;
    const char* const name_;
    bool pinned_;

    friend class SamplingHeapProfiler;

    DISALLOW_COPY_AND_ASSIGN(AllocationNode);
  };

 private:
  Heap* heap() const { return heap_; }

  void SampleObject(Address soon_object, size_t size);

  static void OnWeakCallback(const WeakCallbackInfo<Sample>& data);

  // Methods that construct v8::AllocationProfile.

  // Translates the provided AllocationNode *node* returning an equivalent
  // AllocationProfile::Node. The newly created AllocationProfile::Node is added
  // to the provided AllocationProfile *profile*. Line numbers, column numbers,
  // and script names are resolved using *scripts* which maps all currently
  // loaded scripts keyed by their script id.
  v8::AllocationProfile::Node* TranslateAllocationNode(
      AllocationProfile* profile, SamplingHeapProfiler::AllocationNode* node,
      const std::map<int, Handle<Script>>& scripts);
  v8::AllocationProfile::Allocation ScaleSample(size_t size,
                                                unsigned int count);
  AllocationNode* AddStack();

  Isolate* const isolate_;
  Heap* const heap_;
  std::unique_ptr<SamplingAllocationObserver> new_space_observer_;
  std::unique_ptr<SamplingAllocationObserver> other_spaces_observer_;
  StringsStorage* const names_;
  AllocationNode profile_root_;
  std::set<Sample*> samples_;
  const int stack_depth_;
  const uint64_t rate_;
  v8::HeapProfiler::SamplingFlags flags_;

  friend class SamplingAllocationObserver;

  DISALLOW_COPY_AND_ASSIGN(SamplingHeapProfiler);
};

class SamplingAllocationObserver : public AllocationObserver {
 public:
  SamplingAllocationObserver(Heap* heap, intptr_t step_size, uint64_t rate,
                             SamplingHeapProfiler* profiler,
                             base::RandomNumberGenerator* random)
      : AllocationObserver(step_size),
        profiler_(profiler),
        heap_(heap),
        random_(random),
        rate_(rate) {}
  virtual ~SamplingAllocationObserver() {}

 protected:
  void Step(int bytes_allocated, Address soon_object, size_t size) override {
    USE(heap_);
    DCHECK(heap_->gc_state() == Heap::NOT_IN_GC);
    if (soon_object) {
      // TODO(ofrobots): it would be better to sample the next object rather
      // than skipping this sample epoch if soon_object happens to be null.
      profiler_->SampleObject(soon_object, size);
    }
  }

  intptr_t GetNextStepSize() override { return GetNextSampleInterval(rate_); }

 private:
  intptr_t GetNextSampleInterval(uint64_t rate);
  SamplingHeapProfiler* const profiler_;
  Heap* const heap_;
  base::RandomNumberGenerator* const random_;
  uint64_t const rate_;
};

}  // namespace internal
}  // namespace v8

#endif  // V8_PROFILER_SAMPLING_HEAP_PROFILER_H_