Implement a heap profiler for the Dart managed heap.

runtime/vm/heap_profiler.h

+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+#ifndef VM_HEAP_PROFILER_H_
+#define VM_HEAP_PROFILER_H_
+
+#include <set>
+
+#include "include/dart_api.h"
+#include "vm/globals.h"
+#include "vm/handles.h"
+#include "vm/object.h"
+#include "vm/visitor.h"
+
+namespace dart {
+
+// A HeapProfiler writes a snapshot of the heap for off-line analysis.
+// The heap is written in binary HPROF format, which is a sequence of
+// self describing records.  A description of the HPROF format can be
+// found at
+//
+// http://java.net/downloads/heap-snapshot/hprof-binary-format.html
+//
+// HPROF was not designed for Dart, but most Dart concepts can be
+// mapped directly into HPROF.  Some features, such as immediate
+// objects and variable length objects, require a translation.
+class HeapProfiler {
+ public:
+  enum Tag {
+    kStringInUtf8 = 0x01,
+    kLoadClass = 0x02,
+    kUnloadClass = 0x03,
+    kStackFrame = 0x04,
+    kStackTrace = 0x05,
+    kAllocSites = 0x06,
+    kHeapSummary = 0x07,
+    kStartThread = 0x0A,
+    kEndThread = 0x0B,
+    kHeapDump = 0x0C,
+    kCpuSamples = 0x0D,
+    kControlSettings = 0x0E,
+    kHeapDumpSummary = 0x1C,
+    kHeapDumpEnd = 0x2C
+  };
+
+  // Sub-record tags describe sub-records within a heap dump.
+  enum Subtag {
+    kRootJniGlobal = 0x01,
+    kRootJniLocal = 0x01,
+    kRootJavaFrame = 0x03,
+    kRootNativeStack = 0x04,
+    kRootStickyClass = 0x05,
+    kRootThreadBlock = 0x06,
+    kRootMonitorUsed = 0x07,
+    kRootThreadObject = 0x08,
+    kClassDump = 0x20,
+    kInstanceDump = 0x21,
+    kObjectArrayDump = 0x22,
+    kPrimitiveArrayDump = 0x23,
+    kRootUnknown = 0xFF
+  };
+
+  // Tags for describing element and field types.
+  enum BasicType {
+    kObject = 2,
+    kBoolean = 4,
+    kChar = 5,
+    kFloat = 6,
+    kDouble = 7,
+    kByte = 8,
+    kShort = 9,
+    kInt = 10,
+    kLong = 11
+  };
+
+  HeapProfiler(Dart_HeapProfileWriteCallback callback, void* stream);
+  ~HeapProfiler();
+
+  // Writes a root to the heap dump.
+  void WriteRoot(const RawObject* raw_obj);
+
+  // Writes a object to the heap dump.
+  void WriteObject(const RawObject* raw_obj);
+
+ private:
+  // Record tags describe top-level records.
+  // A growable array of bytes used to build a record body.
+  class Buffer {
+   public:
+    Buffer() : data_(0), size_(0), capacity_(0) {
+    }
+    ~Buffer();
+
+    // Writes an array of bytes to the buffer, increasing the capacity
+    // as needed.
+    void Write(const uint8_t* data, intptr_t length);
+
+    // Returns the underlying element storage.
+    const uint8_t* Data() const {
+      return data_;
+    }
+
+    // Returns the number of elements written to the buffer.
+    intptr_t Size() const {
+      return size_;
+    }
+
+   private:
+    // Resizes the element storage, if needed.
+    void EnsureCapacity(intptr_t size);
+
+    uint8_t* data_;
+
+    intptr_t size_;
+
+    // Size of the element storage.
+    intptr_t capacity_;
+
+    DISALLOW_COPY_AND_ASSIGN(Buffer);
+  };
+
+  // A top-level data record.
+  class Record {
+   public:
+    Record(uint8_t tag, HeapProfiler* profiler)
+        : tag_(tag), profiler_(profiler) {
+    }
+    ~Record() {
+      profiler_->WriteRecord(*this);
+    }
+
+    // Returns the tag describing the record format.
+    uint8_t Tag() const {
+      return tag_;
+    }
+
+    // Returns a millisecond time delta, always 0.
+    uint8_t Time() const {
+      return 0;
+    }
+
+    // Returns the record length in bytes.
+    uint32_t Length() const {
+      return body_.Size();
+    }
+
+    // Returns the record body.
+    const uint8_t* Body() const {
+      return body_.Data();
+    }
+
+    // Appends an array of 8-bit values to the record body.
+    void Write(const uint8_t* value, intptr_t size);
+
+    // Appends an 8-, 16-, 32- or 64-bit value to the body in
+    // big-endian format.
+    void Write8(uint8_t value);
+    void Write16(uint16_t value);
+    void Write32(uint32_t value);
+    void Write64(uint64_t value);
+
+    // Appends an ID to the body.
+    void WritePointer(const void* value);
+
+   private:
+    // A tag value that describes the record format.
+    uint8_t tag_;
+
+    // The payload of the record as described by the tag.
+    Buffer body_;
+
+    // Parent object.
+    HeapProfiler* profiler_;
+
+    DISALLOW_COPY_AND_ASSIGN(Record);
+  };
+
+  // A sub-record within a heap dump record.  Write calls are
+  // forwarded to the profilers heap dump record instance.
+  class SubRecord {
+   public:
+    // Starts a new sub-record within the heap dump record.
+    SubRecord(uint8_t sub_tag, HeapProfiler* profiler);
+    ~SubRecord();
+
+    // Appends an array of 8-bit values to the heap dump record.
+    void Write(const uint8_t* value, intptr_t size);
+
+    // Appends an 8-, 16-, 32- or 64-bit value to the heap dump
+    // record.
+    void Write8(uint8_t value);
+    void Write16(uint16_t value);
+    void Write32(uint32_t value);
+    void Write64(uint64_t value);
+
+    // Appends an ID to the current heap dump record.
+    void WritePointer(const void* value);
+
+   private:
+    // The record instance that receives forwarded write calls.
+    Record* record_;
+  };
+
+  // Id canonizers.
+  const RawClass* ClassId(const RawClass* raw_class);
+  const RawObject* ObjectId(const RawObject* raw_obj);
+  const char* StringId(const char* c_string);
+  const RawString* StringId(const RawString* raw_string);
+
+  // Invokes the write callback.
+  void Write(const void* data, intptr_t size);
+
+  // Writes the binary hprof header to the output stream.
+  void WriteHeader();
+
+  // Writes a record to the output stream.
+  void WriteRecord(const Record& record);
+
+
+  // Writes a string in utf-8 record to the output stream.
+  void WriteStringInUtf8(const char* c_string);
+  void WriteStringInUtf8(const RawString* raw_string);
+
+
+  // Writes a load class record to the output stream.
+  void WriteLoadClass(const RawClass* raw_class);
+
+  // Writes an empty stack trace to the output stream.
+  void WriteStackTrace();
+
+  // Writes a heap summary record to the output stream.
+  void WriteHeapSummary(uint32_t total_live_bytes,
+                        uint32_t total_live_instances,
+                        uint64_t total_bytes_allocated,
+                        uint64_t total_instances_allocated);
+
+  // Writes a heap dump record to the output stream.
+  void WriteHeapDump();
+
+  // Writes a sub-record to the heap dump record.
+  void WriteClassDump(const RawClass* raw_class);
+  void WriteInstanceDump(const RawObject* raw_obj);
+  void WriteObjectArrayDump(const RawArray* raw_array);
+  void WritePrimitiveArrayDump(const RawByteArray* raw_byte_array,
+                               uint8_t tag,
+                               const void* data);
+
+  static const RawClass* GetClass(const RawObject* raw_obj);
+  static const RawClass* GetSuperClass(const RawClass* raw_class);
+
+  Dart_HeapProfileWriteCallback write_callback_;
+
+  void* output_stream_;
+
+  Record* heap_dump_record_;
+
+  std::set<const RawSmi*> smi_table_;
+  std::set<const RawClass*> class_table_;
+  std::set<const RawString*> string_table_;
+
+  DISALLOW_COPY_AND_ASSIGN(HeapProfiler);
+};
+
+
+// Writes a root sub-record to the heap dump for every strong handle.
+class HeapProfilerRootVisitor : public ObjectPointerVisitor {
+ public:
+  explicit HeapProfilerRootVisitor(HeapProfiler* profiler)
+      : ObjectPointerVisitor(Isolate::Current()),
+        profiler_(profiler) {
+  }
+
+  virtual void VisitPointers(RawObject** first, RawObject** last);
+
+ private:
+  HeapProfiler* profiler_;
+  DISALLOW_IMPLICIT_CONSTRUCTORS(HeapProfilerRootVisitor);
+};
+
+
+// Writes a root sub-record to the heap dump for every weak handle.
+class HeapProfilerWeakRootVisitor : public HandleVisitor {
+ public:
+  explicit HeapProfilerWeakRootVisitor(HeapProfilerRootVisitor* visitor)
+      : visitor_(visitor) {
+  }
+
+  virtual void VisitHandle(uword addr);
+
+ private:
+  HeapProfilerRootVisitor* visitor_;
+  DISALLOW_COPY_AND_ASSIGN(HeapProfilerWeakRootVisitor);
+};
+
+
+// Writes a sub-record to the heap dump for every object in the heap.
+class HeapProfilerObjectVisitor : public ObjectVisitor {
+ public:
+  explicit HeapProfilerObjectVisitor(HeapProfiler* profiler)
+      : profiler_(profiler) {
+  }
+
+  virtual void VisitObject(RawObject* obj);
+
+ private:
+  HeapProfiler* profiler_;
+  DISALLOW_COPY_AND_ASSIGN(HeapProfilerObjectVisitor);
+};
+
+}  // namespace dart
+
+#endif  // VM_HEAP_PROFILER_H_