Dramatically speed up detailed heap snapshot generation.

src/profile-generator.cc

 // Copyright 2010 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // 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
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1808 matching lines @@
        obj = iterator.next(), ++objects_count) {}
   return objects_count;
 }
 
 
 class IndexedReferencesExtractor : public ObjectVisitor {
  public:
   IndexedReferencesExtractor(V8HeapExplorer* generator,
                              HeapObject* parent_obj,
                              HeapEntry* parent_entry,
-                             HeapObjectsSet* known_references = NULL)
+                             bool process_field_marks = false)
       : generator_(generator),
         parent_obj_(parent_obj),
         parent_(parent_entry),
-        known_references_(known_references),
+        process_field_marks_(process_field_marks),
         next_index_(1) {
   }
   void VisitPointers(Object** start, Object** end) {
     for (Object** p = start; p < end; p++) {
-      if (!known_references_ || !known_references_->Contains(*p)) {
-        generator_->SetHiddenReference(parent_obj_, parent_, next_index_++, *p);
-      }
+      if (CheckVisitedAndUnmark(p)) continue;
+      generator_->SetHiddenReference(parent_obj_, parent_, next_index_++, *p);
     }
   }
+  static void MarkVisitedField(HeapObject* obj, int offset) {
+    if (offset < 0) return;
+    Address field = obj->address() + offset;
+    ASSERT(!Memory::Object_at(field)->IsFailure());
+    ASSERT(Memory::Object_at(field)->IsHeapObject());
+    *field |= kFailureTag;    
+  }
  private:
+  bool CheckVisitedAndUnmark(Object** field) {
+    if (process_field_marks_ && (*field)->IsFailure()) {
+      const int unmark_tag = ~kFailureTagMask | kHeapObjectTag;
+      *field = reinterpret_cast<Object*>(
+          reinterpret_cast<intptr_t>(*field) & unmark_tag);

[Vitaly Repeshko, 2011/03/18 12:16:36]

Hmm, I think the correct way is:
(reinterpret_cast<intptr_t>(*field) & ~kFailureTagMask) | kHeapObjectTag.

[mnaganov (inactive), 2011/03/18 12:31:01]

Done.

+      ASSERT((*field)->IsHeapObject());
+      return true;
+    }
+    return false;
+  }
   V8HeapExplorer* generator_;
   HeapObject* parent_obj_;
   HeapEntry* parent_;
-  HeapObjectsSet* known_references_;
+  bool process_field_marks_;
   int next_index_;
 };
 
 
 void V8HeapExplorer::ExtractReferences(HeapObject* obj) {
   HeapEntry* entry = GetEntry(obj);
   if (entry == NULL) return;  // No interest in this object.
 
-  known_references_.Clear();
   if (obj->IsJSGlobalProxy()) {
     // We need to reference JS global objects from snapshot's root.
     // We use JSGlobalProxy because this is what embedder (e.g. browser)
     // uses for the global object.
     JSGlobalProxy* proxy = JSGlobalProxy::cast(obj);
     SetRootShortcutReference(proxy->map()->prototype());
     IndexedReferencesExtractor refs_extractor(this, obj, entry);
     obj->Iterate(&refs_extractor);
   } else if (obj->IsJSObject()) {
     JSObject* js_obj = JSObject::cast(obj);
     ExtractClosureReferences(js_obj, entry);
     ExtractPropertyReferences(js_obj, entry);
     ExtractElementReferences(js_obj, entry);
     ExtractInternalReferences(js_obj, entry);
-    SetPropertyReference(
-        obj, entry, Heap::Proto_symbol(), js_obj->GetPrototype());
+    SetPropertyReference(obj, entry,
+                         Heap::Proto_symbol(), js_obj->GetPrototype());
     if (obj->IsJSFunction()) {
-      JSFunction* js_fun = JSFunction::cast(obj);
-      if (js_fun->has_prototype()) {
-        SetPropertyReference(
-            obj, entry, Heap::prototype_symbol(), js_fun->prototype());
+      JSFunction* js_fun = JSFunction::cast(js_obj);
+      SetInternalReference(
+          js_fun, entry,
+          "code", js_fun->shared(),
+          JSFunction::kSharedFunctionInfoOffset);
+      Object* proto_or_map = js_fun->prototype_or_initial_map();
+      if (!proto_or_map->IsTheHole()) {
+        if (!proto_or_map->IsMap()) {
+          SetPropertyReference(
+              obj, entry,
+              Heap::prototype_symbol(), proto_or_map,
+              JSFunction::kPrototypeOrInitialMapOffset);
+        } else {
+          SetPropertyReference(
+              obj, entry,
+              Heap::prototype_symbol(), js_fun->prototype());
+        }
       }
     }
-    IndexedReferencesExtractor refs_extractor(
-        this, obj, entry, &known_references_);
+    IndexedReferencesExtractor refs_extractor(this, obj, entry, true);
     obj->Iterate(&refs_extractor);
   } else if (obj->IsString()) {
     if (obj->IsConsString()) {
       ConsString* cs = ConsString::cast(obj);
       SetInternalReference(obj, entry, 1, cs->first());
       SetInternalReference(obj, entry, 2, cs->second());
     }
   } else {
     IndexedReferencesExtractor refs_extractor(this, obj, entry);
     obj->Iterate(&refs_extractor);
@@ skipping 12 matching lines @@
         context->closure()->shared()->scope_info();
     ScopeInfo<ZoneListAllocationPolicy> zone_scope_info(serialized_scope_info);
     int locals_number = zone_scope_info.NumberOfLocals();
     for (int i = 0; i < locals_number; ++i) {
       String* local_name = *zone_scope_info.LocalName(i);
       int idx = serialized_scope_info->ContextSlotIndex(local_name, NULL);
       if (idx >= 0 && idx < context->length()) {
         SetClosureReference(js_obj, entry, local_name, context->get(idx));
       }
     }
-    SetInternalReference(js_obj, entry, "code", func->shared());
   }
 }
 
 
 void V8HeapExplorer::ExtractPropertyReferences(JSObject* js_obj,
                                                HeapEntry* entry) {
   if (js_obj->HasFastProperties()) {
     DescriptorArray* descs = js_obj->map()->instance_descriptors();
     for (int i = 0; i < descs->number_of_descriptors(); i++) {
       switch (descs->GetType(i)) {
         case FIELD: {
           int index = descs->GetFieldIndex(i);
           SetPropertyReference(
-              js_obj, entry, descs->GetKey(i), js_obj->FastPropertyAt(index));
+              js_obj, entry,
+              descs->GetKey(i), js_obj->FastPropertyAt(index),
+              js_obj->GetFastPropertyOffset(index));
           break;
         }
         case CONSTANT_FUNCTION:
           SetPropertyReference(
-              js_obj, entry, descs->GetKey(i), descs->GetConstantFunction(i));
+              js_obj, entry,
+              descs->GetKey(i), descs->GetConstantFunction(i));
           break;
         default: ;
       }
     }
   } else {
     StringDictionary* dictionary = js_obj->property_dictionary();
     int length = dictionary->Capacity();
     for (int i = 0; i < length; ++i) {
       Object* k = dictionary->KeyAt(i);
       if (dictionary->IsKey(k)) {
@@ skipping 39 matching lines @@
     }
   }
 }
 
 
 void V8HeapExplorer::ExtractInternalReferences(JSObject* js_obj,
                                                HeapEntry* entry) {
   int length = js_obj->GetInternalFieldCount();
   for (int i = 0; i < length; ++i) {
     Object* o = js_obj->GetInternalField(i);
-    SetInternalReference(js_obj, entry, i, o);
+    SetInternalReference(
+        js_obj, entry, i, o, js_obj->GetInternalFieldOffset(i));
   }
 }
 
 
 HeapEntry* V8HeapExplorer::GetEntry(Object* obj) {
   if (!obj->IsHeapObject()) return NULL;
   return filler_->FindOrAddEntry(obj, this);
 }
 
 
@@ skipping 41 matching lines @@
                                          String* reference_name,
                                          Object* child_obj) {
   HeapEntry* child_entry = GetEntry(child_obj);
   if (child_entry != NULL) {
     filler_->SetNamedReference(HeapGraphEdge::kContextVariable,
                                parent_obj,
                                parent_entry,
                                collection_->names()->GetName(reference_name),
                                child_obj,
                                child_entry);
-    known_references_.Insert(child_obj);
   }
 }
 
 
 void V8HeapExplorer::SetElementReference(HeapObject* parent_obj,
                                          HeapEntry* parent_entry,
                                          int index,
                                          Object* child_obj) {
   HeapEntry* child_entry = GetEntry(child_obj);
   if (child_entry != NULL) {
     filler_->SetIndexedReference(HeapGraphEdge::kElement,
                                  parent_obj,
                                  parent_entry,
                                  index,
                                  child_obj,
                                  child_entry);
-    known_references_.Insert(child_obj);
   }
 }
 
 
 void V8HeapExplorer::SetInternalReference(HeapObject* parent_obj,
                                           HeapEntry* parent_entry,
                                           const char* reference_name,
-                                          Object* child_obj) {
+                                          Object* child_obj,
+                                          int field_offset) {
   HeapEntry* child_entry = GetEntry(child_obj);
   if (child_entry != NULL) {
     filler_->SetNamedReference(HeapGraphEdge::kInternal,
                                parent_obj,
                                parent_entry,
                                reference_name,
                                child_obj,
                                child_entry);
-    known_references_.Insert(child_obj);
+    IndexedReferencesExtractor::MarkVisitedField(parent_obj, field_offset);
   }
 }
 
 
 void V8HeapExplorer::SetInternalReference(HeapObject* parent_obj,
                                           HeapEntry* parent_entry,
                                           int index,
-                                          Object* child_obj) {
+                                          Object* child_obj,
+                                          int field_offset) {
   HeapEntry* child_entry = GetEntry(child_obj);
   if (child_entry != NULL) {
     filler_->SetNamedReference(HeapGraphEdge::kInternal,
                                parent_obj,
                                parent_entry,
                                collection_->names()->GetName(index),
                                child_obj,
                                child_entry);
-    known_references_.Insert(child_obj);
+    IndexedReferencesExtractor::MarkVisitedField(parent_obj, field_offset);
   }
 }
 
 
 void V8HeapExplorer::SetHiddenReference(HeapObject* parent_obj,
                                         HeapEntry* parent_entry,
                                         int index,
                                         Object* child_obj) {
   HeapEntry* child_entry = GetEntry(child_obj);
   if (child_entry != NULL) {
     filler_->SetIndexedReference(HeapGraphEdge::kHidden,
                                  parent_obj,
                                  parent_entry,
                                  index,
                                  child_obj,
                                  child_entry);
   }
 }
 
 
 void V8HeapExplorer::SetPropertyReference(HeapObject* parent_obj,
                                           HeapEntry* parent_entry,
                                           String* reference_name,
-                                          Object* child_obj) {
+                                          Object* child_obj,
+                                          int field_offset) {
   HeapEntry* child_entry = GetEntry(child_obj);
   if (child_entry != NULL) {
     HeapGraphEdge::Type type = reference_name->length() > 0 ?
         HeapGraphEdge::kProperty : HeapGraphEdge::kInternal;
     filler_->SetNamedReference(type,
                                parent_obj,
                                parent_entry,
                                collection_->names()->GetName(reference_name),
                                child_obj,
                                child_entry);
-    known_references_.Insert(child_obj);
+    IndexedReferencesExtractor::MarkVisitedField(parent_obj, field_offset);
   }
 }
 
 
-void V8HeapExplorer::SetPropertyShortcutReference(
-    HeapObject* parent_obj,
-    HeapEntry* parent_entry,
-    String* reference_name,
-    Object* child_obj) {
+void V8HeapExplorer::SetPropertyShortcutReference(HeapObject* parent_obj,
+                                                  HeapEntry* parent_entry,
+                                                  String* reference_name,
+                                                  Object* child_obj) {
   HeapEntry* child_entry = GetEntry(child_obj);
   if (child_entry != NULL) {
     filler_->SetNamedReference(HeapGraphEdge::kShortcut,
                                parent_obj,
                                parent_entry,
                                collection_->names()->GetName(reference_name),
                                child_obj,
                                child_entry);
   }
 }
@@ skipping 986 matching lines @@
 
 
 String* GetConstructorNameForHeapProfile(JSObject* object) {
   if (object->IsJSFunction()) return Heap::closure_symbol();
   return object->constructor_name();
 }
 
 } }  // namespace v8::internal
 
 #endif  // ENABLE_LOGGING_AND_PROFILING