Sampling heap profiler: use map instead of vector for children.

src/profiler/sampling-heap-profiler.cc

 // 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.
 
 #include "src/profiler/sampling-heap-profiler.h"
 
 #include <stdint.h>
 #include <memory>
 #include "src/api.h"
 #include "src/base/utils/random-number-generator.h"
@@ skipping 107 matching lines @@
     const WeakCallbackInfo<Sample>& data) {
   Sample* sample = data.GetParameter();
   AllocationNode* node = sample->owner;
   DCHECK(node->allocations_[sample->size] > 0);
   node->allocations_[sample->size]--;
   if (node->allocations_[sample->size] == 0) {
     node->allocations_.erase(sample->size);
     while (node->allocations_.empty() && node->children_.empty() &&
            node->parent_ && !node->parent_->pinned_) {
       AllocationNode* parent = node->parent_;
-      parent->children_.erase(
-          std::find(parent->children_.begin(), parent->children_.end(), node));
+      AllocationNode::FunctionId id = AllocationNode::function_id(
+          node->script_id_, node->script_position_, node->name_);
+      parent->children_.erase(id);
       delete node;
       node = parent;
     }
   }
   sample->profiler->samples_.erase(sample);
   delete sample;
 }
 
-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;
-    }
+SamplingHeapProfiler::AllocationNode*
+SamplingHeapProfiler::AllocationNode::FindOrAddChildNode(const char* name,
+                                                         int script_id,
+                                                         int start_position) {
+  FunctionId id = function_id(script_id, start_position, name);
+  auto it = children_.find(id);
+  if (it != children_.end()) {
+    DCHECK(strcmp(it->second->name_, name) == 0);
+    return it->second;
   }
-  AllocationNode* child =
-      new AllocationNode(parent, name, script_id, start_position);
-  parent->children_.push_back(child);
+  auto child = new AllocationNode(this, name, script_id, start_position);
+  children_.insert(std::make_pair(id, child));
   return child;
 }
 
 SamplingHeapProfiler::AllocationNode* SamplingHeapProfiler::AddStack() {
   AllocationNode* node = &profile_root_;
 
   std::vector<SharedFunctionInfo*> stack;
   JavaScriptFrameIterator it(isolate_);
   int frames_captured = 0;
   while (!it.done() && frames_captured < stack_depth_) {
@@ skipping 20 matching lines @@
       case EXTERNAL:
         name = "(EXTERNAL)";
         break;
       case IDLE:
         name = "(IDLE)";
         break;
       case JS:
         name = "(JS)";
         break;
     }
-    return FindOrAddChildNode(node, name, v8::UnboundScript::kNoScriptId, 0);
+    return node->FindOrAddChildNode(name, v8::UnboundScript::kNoScriptId, 0);
   }
 
   // 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());
+    node = node->FindOrAddChildNode(name, script_id, shared->start_position());
   }
   return node;
 }
 
 v8::AllocationProfile::Node* SamplingHeapProfiler::TranslateAllocationNode(
     AllocationProfile* profile, SamplingHeapProfiler::AllocationNode* node,
     const std::map<int, Handle<Script>>& scripts) {
   // By pinning the node we make sure its children won't get disposed if
   // a GC kicks in during the tree retrieval.
   node->pinned_ = true;
@@ skipping 22 matching lines @@
   for (auto alloc : node->allocations_) {
     allocations.push_back(ScaleSample(alloc.first, alloc.second));
   }
 
   profile->nodes().push_back(v8::AllocationProfile::Node(
       {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();
-  size_t child_len = node->children_.size();
-  // The children vector may have nodes appended to it during translation
+  // The children map may have nodes inserted into it during translation
   // because the translation may allocate strings on the JS heap that have
-  // the potential to be sampled. We cache the length of the vector before
-  // iteration so that nodes appended to the vector during iteration are
-  // not processed.
-  for (size_t i = 0; i < child_len; i++) {
+  // the potential to be sampled. That's ok since map iterators are not
+  // invalidated upon std::map insertion.
+  for (auto it : node->children_) {
     current->children.push_back(
-        TranslateAllocationNode(profile, node->children_[i], scripts));
+        TranslateAllocationNode(profile, it.second, scripts));
   }
   node->pinned_ = false;
   return current;
 }
 
 v8::AllocationProfile* SamplingHeapProfiler::GetAllocationProfile() {
   if (flags_ & v8::HeapProfiler::kSamplingForceGC) {
     isolate_->heap()->CollectAllGarbage(Heap::kNoGCFlags,
                                         "SamplingHeapProfiler");
   }
   // 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.
   std::map<int, Handle<Script>> scripts;
   {
     Script::Iterator iterator(isolate_);
     while (Script* script = iterator.Next()) {
       scripts[script->id()] = handle(script);
     }
   }
   auto profile = new v8::internal::AllocationProfile();
   TranslateAllocationNode(profile, &profile_root_, scripts);
   return profile;
 }
 
 
 }  // namespace internal
 }  // namespace v8