Sampling heap profiler data structure changes

Previously, the sampling heap profiler stored a list of samples and then
built a tree representation when the profile was queried by calling
GetAllocationProfile. This change reduces duplication by removing stacks
from all samples. Also, less information is stored in the tree
maintained by the profiler and remaining information (script name, line
no, etc) is resolved when a profile is requested.

BUG=

Review URL: https://codereview.chromium.org/1697903002

Cr-Commit-Position: refs/heads/master@{#34119}

src/profiler/sampling-heap-profiler.cc

@@ -44,6 +44,7 @@ SamplingHeapProfiler::SamplingHeapProfiler(Heap* heap, StringsStorage* names,
           heap_, static_cast<intptr_t>(rate), rate, this,
           heap->isolate()->random_number_generator())),
       names_(names),
+      profile_root_("(root)", v8::UnboundScript::kNoScriptId, 0),
       samples_(),
       stack_depth_(stack_depth) {
   heap->new_space()->AddAllocationObserver(new_space_observer_.get());
@@ -65,12 +66,10 @@ SamplingHeapProfiler::~SamplingHeapProfiler() {
     }
   }
 
-  // Clear samples and drop all the weak references we are keeping.
-  std::set<SampledAllocation*>::iterator it;
-  for (it = samples_.begin(); it != samples_.end(); ++it) {
-    delete *it;
+  for (auto sample : samples_) {
+    delete sample;
   }
-  std::set<SampledAllocation*> empty;
+  std::set<Sample*> empty;
   samples_.swap(empty);
 }
 
@@ -88,51 +87,48 @@ void SamplingHeapProfiler::SampleObject(Address soon_object, size_t size) {
 
   Local<v8::Value> loc = v8::Utils::ToLocal(obj);
 
-  SampledAllocation* sample =
-      new SampledAllocation(this, isolate_, loc, size, stack_depth_);
+  AllocationNode* node = AddStack();
+  node->allocations_[size]++;
+  Sample* sample = new Sample(size, node, loc, this);
   samples_.insert(sample);
+  sample->global.SetWeak(sample, OnWeakCallback, WeakCallbackType::kParameter);
 }
 
-
-void SamplingHeapProfiler::SampledAllocation::OnWeakCallback(
-    const WeakCallbackInfo<SampledAllocation>& data) {
-  SampledAllocation* sample = data.GetParameter();
-  sample->sampling_heap_profiler_->samples_.erase(sample);
+void SamplingHeapProfiler::OnWeakCallback(
+    const WeakCallbackInfo<Sample>& data) {
+  Sample* sample = data.GetParameter();
+  AllocationNode* node = sample->owner;
+  DCHECK(node->allocations_[sample->size] > 0);
+  node->allocations_[sample->size]--;
+  sample->profiler->samples_.erase(sample);
   delete sample;
 }
 
-
-SamplingHeapProfiler::FunctionInfo::FunctionInfo(SharedFunctionInfo* shared,
-                                                 StringsStorage* names)
-    : name_(names->GetFunctionName(shared->DebugName())),
-      script_name_(""),
-      script_id_(v8::UnboundScript::kNoScriptId),
-      start_position_(shared->start_position()) {
-  if (shared->script()->IsScript()) {
-    Script* script = Script::cast(shared->script());
-    script_id_ = script->id();
-    if (script->name()->IsName()) {
-      Name* name = Name::cast(script->name());
-      script_name_ = names->GetName(name);
+SamplingHeapProfiler::AllocationNode* SamplingHeapProfiler::FindOrAddChildNode(
+    AllocationNode* parent, const char* name, int script_id,
+    int start_position) {
+  for (AllocationNode* child : parent->children_) {
+    if (child->script_id_ == script_id &&
+        child->script_position_ == start_position &&
+        strcmp(child->name_, name) == 0) {
+      return child;
     }
   }
+  AllocationNode* child = new AllocationNode(name, script_id, start_position);
+  parent->children_.push_back(child);
+  return child;
 }
 
+SamplingHeapProfiler::AllocationNode* SamplingHeapProfiler::AddStack() {
+  AllocationNode* node = &profile_root_;
 
-SamplingHeapProfiler::SampledAllocation::SampledAllocation(
-    SamplingHeapProfiler* sampling_heap_profiler, Isolate* isolate,
-    Local<Value> local, size_t size, int max_frames)
-    : sampling_heap_profiler_(sampling_heap_profiler),
-      global_(reinterpret_cast<v8::Isolate*>(isolate), local),
-      size_(size) {
-  global_.SetWeak(this, OnWeakCallback, WeakCallbackType::kParameter);
-
-  StackTraceFrameIterator it(isolate);
+  std::vector<SharedFunctionInfo*> stack;
+  StackTraceFrameIterator it(isolate_);
   int frames_captured = 0;
-  while (!it.done() && frames_captured < max_frames) {
+  while (!it.done() && frames_captured < stack_depth_) {
     JavaScriptFrame* frame = it.frame();
     SharedFunctionInfo* shared = frame->function()->shared();
-    stack_.push_back(new FunctionInfo(shared, sampling_heap_profiler->names()));
+    stack.push_back(shared);
 
     frames_captured++;
     it.Advance();
@@ -140,7 +136,7 @@ SamplingHeapProfiler::SampledAllocation::SampledAllocation(
 
   if (frames_captured == 0) {
     const char* name = nullptr;
-    switch (isolate->current_vm_state()) {
+    switch (isolate_->current_vm_state()) {
       case GC:
         name = "(GC)";
         break;
@@ -160,71 +156,63 @@ SamplingHeapProfiler::SampledAllocation::SampledAllocation(
         name = "(JS)";
         break;
     }
-    stack_.push_back(new FunctionInfo(name));
+    return FindOrAddChildNode(node, name, v8::UnboundScript::kNoScriptId, 0);
   }
-}
 
-v8::AllocationProfile::Node* SamplingHeapProfiler::AllocateNode(
-    AllocationProfile* profile, const std::map<int, Script*>& scripts,
-    FunctionInfo* function_info) {
-  DCHECK(function_info->get_name());
-  DCHECK(function_info->get_script_name());
+  // We need to process the stack in reverse order as the top of the stack is
+  // the first element in the list.
+  for (auto it = stack.rbegin(); it != stack.rend(); ++it) {
+    SharedFunctionInfo* shared = *it;
+    const char* name = this->names()->GetFunctionName(shared->DebugName());
+    int script_id = v8::UnboundScript::kNoScriptId;
+    if (shared->script()->IsScript()) {
+      Script* script = Script::cast(shared->script());
+      script_id = script->id();
+    }
+    node = FindOrAddChildNode(node, name, script_id, shared->start_position());
+  }
+  return node;
+}
 
+v8::AllocationProfile::Node* SamplingHeapProfiler::TranslateAllocationNode(
+    AllocationProfile* profile, SamplingHeapProfiler::AllocationNode* node,
+    const std::map<int, Script*>& scripts) {
+  Local<v8::String> script_name =
+      ToApiHandle<v8::String>(isolate_->factory()->InternalizeUtf8String(""));
   int line = v8::AllocationProfile::kNoLineNumberInfo;
   int column = v8::AllocationProfile::kNoColumnNumberInfo;
-
-  if (function_info->get_script_id() != v8::UnboundScript::kNoScriptId) {
+  std::vector<v8::AllocationProfile::Allocation> allocations;
+  if (node->script_id_ != v8::UnboundScript::kNoScriptId) {
     // Cannot use std::map<T>::at because it is not available on android.
     auto non_const_scripts = const_cast<std::map<int, Script*>&>(scripts);
-    Handle<Script> script(non_const_scripts[function_info->get_script_id()]);
+    Script* script = non_const_scripts[node->script_id_];
+    if (script->name()->IsName()) {
+      Name* name = Name::cast(script->name());
+      script_name = ToApiHandle<v8::String>(
+          isolate_->factory()->InternalizeUtf8String(names_->GetName(name)));
+    }
+    Handle<Script> script_handle(script);
 
-    line =
-        1 + Script::GetLineNumber(script, function_info->get_start_position());
-    column = 1 + Script::GetColumnNumber(script,
-                                         function_info->get_start_position());
+    line = 1 + Script::GetLineNumber(script_handle, node->script_position_);
+    column = 1 + Script::GetColumnNumber(script_handle, node->script_position_);
+    for (auto alloc : node->allocations_) {
+      allocations.push_back({alloc.first, alloc.second});
+    }
   }
 
   profile->nodes().push_back(v8::AllocationProfile::Node(
-      {ToApiHandle<v8::String>(isolate_->factory()->InternalizeUtf8String(
-           function_info->get_name())),
-       ToApiHandle<v8::String>(isolate_->factory()->InternalizeUtf8String(
-           function_info->get_script_name())),
-       function_info->get_script_id(), function_info->get_start_position(),
-       line, column, std::vector<v8::AllocationProfile::Node*>(),
-       std::vector<v8::AllocationProfile::Allocation>()}));
-
-  return &profile->nodes().back();
-}
-
-v8::AllocationProfile::Node* SamplingHeapProfiler::FindOrAddChildNode(
-    AllocationProfile* profile, const std::map<int, Script*>& scripts,
-    v8::AllocationProfile::Node* parent, FunctionInfo* function_info) {
-  for (v8::AllocationProfile::Node* child : parent->children) {
-    if (child->script_id == function_info->get_script_id() &&
-        child->start_position == function_info->get_start_position())
-      return child;
-  }
-  v8::AllocationProfile::Node* child =
-      AllocateNode(profile, scripts, function_info);
-  parent->children.push_back(child);
-  return child;
-}
-
-v8::AllocationProfile::Node* SamplingHeapProfiler::AddStack(
-    AllocationProfile* profile, const std::map<int, Script*>& scripts,
-    const std::vector<FunctionInfo*>& stack) {
-  v8::AllocationProfile::Node* node = profile->GetRootNode();
-
-  // We need to process the stack in reverse order as the top of the stack is
-  // the first element in the list.
-  for (auto it = stack.rbegin(); it != stack.rend(); ++it) {
-    FunctionInfo* function_info = *it;
-    node = FindOrAddChildNode(profile, scripts, node, function_info);
+      {ToApiHandle<v8::String>(
+           isolate_->factory()->InternalizeUtf8String(node->name_)),
+       script_name, node->script_id_, node->script_position_, line, column,
+       std::vector<v8::AllocationProfile::Node*>(), allocations}));
+  v8::AllocationProfile::Node* current = &profile->nodes().back();
+  for (auto child : node->children_) {
+    current->children.push_back(
+        TranslateAllocationNode(profile, child, scripts));
   }
-  return node;
+  return current;
 }
 
-
 v8::AllocationProfile* SamplingHeapProfiler::GetAllocationProfile() {
   // To resolve positions to line/column numbers, we will need to look up
   // scripts. Build a map to allow fast mapping from script id to script.
@@ -239,15 +227,7 @@ v8::AllocationProfile* SamplingHeapProfiler::GetAllocationProfile() {
 
   auto profile = new v8::internal::AllocationProfile();
 
-  // Create the root node.
-  FunctionInfo function_info("(root)");
-  AllocateNode(profile, scripts, &function_info);
-
-  for (SampledAllocation* allocation : samples_) {
-    v8::AllocationProfile::Node* node =
-        AddStack(profile, scripts, allocation->get_stack());
-    node->allocations.push_back({allocation->get_size(), 1});
-  }
+  TranslateAllocationNode(profile, &profile_root_, scripts);
 
   return profile;
 }

src/profiler/sampling-heap-profiler.h

@@ -48,50 +48,50 @@ class SamplingHeapProfiler {
 
   StringsStorage* names() const { return names_; }
 
-  class FunctionInfo {
+  class AllocationNode;
+
+  struct Sample {
    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_; }
+    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:
-    const char* const name_;
-    const char* script_name_;
-    int script_id_;
-    const int start_position_;
+    DISALLOW_COPY_AND_ASSIGN(Sample);
   };
 
-  class SampledAllocation {
+  class AllocationNode {
    public:
-    SampledAllocation(SamplingHeapProfiler* sampling_heap_profiler,
-                      Isolate* isolate, Local<Value> local, size_t size,
-                      int max_frames);
-    ~SampledAllocation() {
-      for (auto info : stack_) {
-        delete info;
+    AllocationNode(const char* const name, int script_id,
+                   const int start_position)
+        : script_id_(script_id),
+          script_position_(start_position),
+          name_(name) {}
+    ~AllocationNode() {
+      for (auto child : children_) {
+        delete child;
       }
-      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);
+    std::map<size_t, unsigned int> allocations_;
+    std::vector<AllocationNode*> children_;
+    const int script_id_;
+    const int script_position_;
+    const char* const name_;
 
-    SamplingHeapProfiler* const sampling_heap_profiler_;
-    Global<Value> global_;
-    std::vector<FunctionInfo*> stack_;
-    const size_t size_;
+    friend class SamplingHeapProfiler;
 
-    DISALLOW_COPY_AND_ASSIGN(SampledAllocation);
+    DISALLOW_COPY_AND_ASSIGN(AllocationNode);
   };
 
  private:
@@ -99,23 +99,29 @@ class SamplingHeapProfiler {
 
   void SampleObject(Address soon_object, size_t size);
 
+  static void OnWeakCallback(const WeakCallbackInfo<Sample>& data);
+
   // Methods that construct v8::AllocationProfile.
-  v8::AllocationProfile::Node* AddStack(
-      AllocationProfile* profile, const std::map<int, Script*>& scripts,
-      const std::vector<FunctionInfo*>& stack);
-  v8::AllocationProfile::Node* FindOrAddChildNode(
-      AllocationProfile* profile, const std::map<int, Script*>& scripts,
-      v8::AllocationProfile::Node* parent, FunctionInfo* function_info);
-  v8::AllocationProfile::Node* AllocateNode(
-      AllocationProfile* profile, const std::map<int, Script*>& scripts,
-      FunctionInfo* function_info);
+
+  // 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, Script*>& scripts);
+  AllocationNode* AddStack();
+  AllocationNode* FindOrAddChildNode(AllocationNode* parent, const char* name,
+                                     int script_id, int start_position);
 
   Isolate* const isolate_;
   Heap* const heap_;
   base::SmartPointer<SamplingAllocationObserver> new_space_observer_;
   base::SmartPointer<SamplingAllocationObserver> other_spaces_observer_;
   StringsStorage* const names_;
-  std::set<SampledAllocation*> samples_;
+  AllocationNode profile_root_;
+  std::set<Sample*> samples_;
   const int stack_depth_;
 
   friend class SamplingAllocationObserver;