src/heap-profiler.h

// Copyright 2009 the V8 project authors. All rights reserved.
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// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
//       notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
//       copyright notice, this list of conditions and the following
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//       with the distribution.
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//       from this software without specific prior written permission.
//
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#ifndef V8_HEAP_PROFILER_H_
#define V8_HEAP_PROFILER_H_

#include "zone-inl.h"

namespace v8 {
namespace internal {

#ifdef ENABLE_LOGGING_AND_PROFILING

class HeapSnapshot;
class HeapSnapshotsCollection;

#define HEAP_PROFILE(Call)                             \
  do {                                                 \
    if (v8::internal::HeapProfiler::is_profiling()) {  \
      v8::internal::HeapProfiler::Call;                \
    }                                                  \
  } while (false)
#else
#define HEAP_PROFILE(Call) ((void) 0)
#endif  // ENABLE_LOGGING_AND_PROFILING

// The HeapProfiler writes data to the log files, which can be postprocessed
// to generate .hp files for use by the GHC/Valgrind tool hp2ps.
class HeapProfiler {
 public:
  static void Setup();
  static void TearDown();

#ifdef ENABLE_LOGGING_AND_PROFILING
  static HeapSnapshot* TakeSnapshot(const char* name);
  static HeapSnapshot* TakeSnapshot(String* name);
  static int GetSnapshotsCount();
  static HeapSnapshot* GetSnapshot(int index);
  static HeapSnapshot* FindSnapshot(unsigned uid);

  static void ObjectMoveEvent(Address from, Address to);

  static INLINE(bool is_profiling()) {
    return singleton_ != NULL && singleton_->snapshots_->is_tracking_objects();
  }

  // Obsolete interface.
  // Write a single heap sample to the log file.
  static void WriteSample();

 private:
  HeapProfiler();
  ~HeapProfiler();
  HeapSnapshot* TakeSnapshotImpl(const char* name);
  HeapSnapshot* TakeSnapshotImpl(String* name);

  // Obsolete interface.
  // Update the array info with stats from obj.
  static void CollectStats(HeapObject* obj, HistogramInfo* info);

  HeapSnapshotsCollection* snapshots_;
  unsigned next_snapshot_uid_;

  static HeapProfiler* singleton_;
#endif  // ENABLE_LOGGING_AND_PROFILING
};


#ifdef ENABLE_LOGGING_AND_PROFILING

// JSObjectsCluster describes a group of JS objects that are
// considered equivalent in terms of a particular profile.
class JSObjectsCluster BASE_EMBEDDED {
 public:
  // These special cases are used in retainer profile.
  enum SpecialCase {
    ROOTS = 1,
    GLOBAL_PROPERTY = 2,
    CODE = 3,
    SELF = 100  // This case is used in ClustersCoarser only.
  };

  JSObjectsCluster() : constructor_(NULL), instance_(NULL) {}
  explicit JSObjectsCluster(String* constructor)
      : constructor_(constructor), instance_(NULL) {}
  explicit JSObjectsCluster(SpecialCase special)
      : constructor_(FromSpecialCase(special)), instance_(NULL) {}
  JSObjectsCluster(String* constructor, Object* instance)
      : constructor_(constructor), instance_(instance) {}

  static int CompareConstructors(const JSObjectsCluster& a,
                                 const JSObjectsCluster& b) {
    // Strings are unique, so it is sufficient to compare their pointers.
    return a.constructor_ == b.constructor_ ? 0
        : (a.constructor_ < b.constructor_ ? -1 : 1);
  }
  static int Compare(const JSObjectsCluster& a, const JSObjectsCluster& b) {
    // Strings are unique, so it is sufficient to compare their pointers.
    const int cons_cmp = CompareConstructors(a, b);
    return cons_cmp == 0 ?
        (a.instance_ == b.instance_ ? 0 : (a.instance_ < b.instance_ ? -1 : 1))
        : cons_cmp;
  }
  static int Compare(const JSObjectsCluster* a, const JSObjectsCluster* b) {
    return Compare(*a, *b);
  }

  bool is_null() const { return constructor_ == NULL; }
  bool can_be_coarsed() const { return instance_ != NULL; }
  String* constructor() const { return constructor_; }

  void Print(StringStream* accumulator) const;
  // Allows null clusters to be printed.
  void DebugPrint(StringStream* accumulator) const;

 private:
  static String* FromSpecialCase(SpecialCase special) {
    // We use symbols that are illegal JS identifiers to identify special cases.
    // Their actual value is irrelevant for us.
    switch (special) {
      case ROOTS: return Heap::result_symbol();
      case GLOBAL_PROPERTY: return Heap::code_symbol();
      case CODE: return Heap::arguments_shadow_symbol();
      case SELF: return Heap::catch_var_symbol();
      default:
        UNREACHABLE();
        return NULL;
    }
  }

  String* constructor_;
  Object* instance_;
};


struct JSObjectsClusterTreeConfig {
  typedef JSObjectsCluster Key;
  typedef NumberAndSizeInfo Value;
  static const Key kNoKey;
  static const Value kNoValue;
  static int Compare(const Key& a, const Key& b) {
    return Key::Compare(a, b);
  }
};
typedef ZoneSplayTree<JSObjectsClusterTreeConfig> JSObjectsClusterTree;


// ConstructorHeapProfile is responsible for gathering and logging
// "constructor profile" of JS objects allocated on heap.
// It is run during garbage collection cycle, thus it doesn't need
// to use handles.
class ConstructorHeapProfile BASE_EMBEDDED {
 public:
  ConstructorHeapProfile();
  virtual ~ConstructorHeapProfile() {}
  void CollectStats(HeapObject* obj);
  void PrintStats();
  // Used by ZoneSplayTree::ForEach. Made virtual to allow overriding in tests.
  virtual void Call(const JSObjectsCluster& cluster,
                    const NumberAndSizeInfo& number_and_size);

 private:
  ZoneScope zscope_;
  JSObjectsClusterTree js_objects_info_tree_;
};


// JSObjectsRetainerTree is used to represent retainer graphs using
// adjacency list form:
//
//   Cluster -> (Cluster -> NumberAndSizeInfo)
//
// Subordinate splay trees are stored by pointer. They are zone-allocated,
// so it isn't needed to manage their lifetime.
//
struct JSObjectsRetainerTreeConfig {
  typedef JSObjectsCluster Key;
  typedef JSObjectsClusterTree* Value;
  static const Key kNoKey;
  static const Value kNoValue;
  static int Compare(const Key& a, const Key& b) {
    return Key::Compare(a, b);
  }
};
typedef ZoneSplayTree<JSObjectsRetainerTreeConfig> JSObjectsRetainerTree;


class ClustersCoarser BASE_EMBEDDED {
 public:
  ClustersCoarser();

  // Processes a given retainer graph.
  void Process(JSObjectsRetainerTree* tree);

  // Returns an equivalent cluster (can be the cluster itself).
  // If the given cluster doesn't have an equivalent, returns null cluster.
  JSObjectsCluster GetCoarseEquivalent(const JSObjectsCluster& cluster);
  // Returns whether a cluster can be substitued with an equivalent and thus,
  // skipped in some cases.
  bool HasAnEquivalent(const JSObjectsCluster& cluster);

  // Used by JSObjectsRetainerTree::ForEach.
  void Call(const JSObjectsCluster& cluster, JSObjectsClusterTree* tree);
  void Call(const JSObjectsCluster& cluster,
            const NumberAndSizeInfo& number_and_size);

 private:
  // Stores a list of back references for a cluster.
  struct ClusterBackRefs {
    explicit ClusterBackRefs(const JSObjectsCluster& cluster_);
    ClusterBackRefs(const ClusterBackRefs& src);
    ClusterBackRefs& operator=(const ClusterBackRefs& src);

    static int Compare(const ClusterBackRefs& a, const ClusterBackRefs& b);
    void SortRefs() { refs.Sort(JSObjectsCluster::Compare); }
    static void SortRefsIterator(ClusterBackRefs* ref) { ref->SortRefs(); }

    JSObjectsCluster cluster;
    ZoneList<JSObjectsCluster> refs;
  };
  typedef ZoneList<ClusterBackRefs> SimilarityList;

  // A tree for storing a list of equivalents for a cluster.
  struct ClusterEqualityConfig {
    typedef JSObjectsCluster Key;
    typedef JSObjectsCluster Value;
    static const Key kNoKey;
    static const Value kNoValue;
    static int Compare(const Key& a, const Key& b) {
      return Key::Compare(a, b);
    }
  };
  typedef ZoneSplayTree<ClusterEqualityConfig> EqualityTree;

  static int ClusterBackRefsCmp(const ClusterBackRefs* a,
                                const ClusterBackRefs* b) {
    return ClusterBackRefs::Compare(*a, *b);
  }
  int DoProcess(JSObjectsRetainerTree* tree);
  int FillEqualityTree();

  static const int kInitialBackrefsListCapacity = 2;
  static const int kInitialSimilarityListCapacity = 2000;
  // Number of passes for finding equivalents. Limits the length of paths
  // that can be considered equivalent.
  static const int kMaxPassesCount = 10;

  ZoneScope zscope_;
  SimilarityList sim_list_;
  EqualityTree eq_tree_;
  ClusterBackRefs* current_pair_;
  JSObjectsRetainerTree* current_set_;
  const JSObjectsCluster* self_;
};


// RetainerHeapProfile is responsible for gathering and logging
// "retainer profile" of JS objects allocated on heap.
// It is run during garbage collection cycle, thus it doesn't need
// to use handles.
class RetainerHeapProfile BASE_EMBEDDED {
 public:
  class Printer {
   public:
    virtual ~Printer() {}
    virtual void PrintRetainers(const JSObjectsCluster& cluster,
                                const StringStream& retainers) = 0;
  };

  RetainerHeapProfile();
  void CollectStats(HeapObject* obj);
  void PrintStats();
  void DebugPrintStats(Printer* printer);
  void StoreReference(const JSObjectsCluster& cluster, HeapObject* ref);

 private:
  ZoneScope zscope_;
  JSObjectsRetainerTree retainers_tree_;
  ClustersCoarser coarser_;
};


class ProducerHeapProfile : public AllStatic {
 public:
  static void Setup();
  static void RecordJSObjectAllocation(Object* obj) {
    if (FLAG_log_producers) DoRecordJSObjectAllocation(obj);
  }

 private:
  static void DoRecordJSObjectAllocation(Object* obj);
  static bool can_log_;
};

#endif  // ENABLE_LOGGING_AND_PROFILING

} }  // namespace v8::internal

#endif  // V8_HEAP_PROFILER_H_