Specialize ScavengingVisitor for the case when all logging and profiling is disabled.

src/heap.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 923 matching lines @@
 }
 
 
 void Heap::Scavenge() {
 #ifdef DEBUG
   if (FLAG_enable_slow_asserts) VerifyNonPointerSpacePointers();
 #endif
 
   gc_state_ = SCAVENGE;
 
+  SwitchScavengingVisitorsTableIfProfilingWasEnabled();
+
   Page::FlipMeaningOfInvalidatedWatermarkFlag(this);
 #ifdef DEBUG
   VerifyPageWatermarkValidity(old_pointer_space_, ALL_VALID);
   VerifyPageWatermarkValidity(map_space_, ALL_VALID);
 #endif
 
   // We do not update an allocation watermark of the top page during linear
   // allocation to avoid overhead. So to maintain the watermark invariant
   // we have to manually cache the watermark and mark the top page as having an
   // invalid watermark. This guarantees that dirty regions iteration will use a
@@ skipping 271 matching lines @@
     }
 
     // Take another spin if there are now unswept objects in new space
     // (there are currently no more unswept promoted objects).
   } while (new_space_front < new_space_.top());
 
   return new_space_front;
 }
 
 
+enum LoggingAndProfiling {
+  LOGGING_AND_PROFILING_ENABLED,
+  LOGGING_AND_PROFILING_DISABLED
+};
+
+
+typedef void (*ScavengingCallback)(Map* map,
+                                   HeapObject** slot,
+                                   HeapObject* object);
+
+
+static Atomic32 scavenging_visitors_table_mode_;
+static VisitorDispatchTable<ScavengingCallback> scavenging_visitors_table_;
+
+
+static inline void DoScavengeObject(Map* map,

[Vitaly Repeshko, 2011/03/30 15:11:04]

This probably needs INLINE to prevent surprises with gcc.

+                                    HeapObject** slot,
+                                    HeapObject* obj) {
+  scavenging_visitors_table_.GetVisitor(map)(map, slot, obj);
+}
+
+
+template<LoggingAndProfiling logging_and_profiling_mode>
 class ScavengingVisitor : public StaticVisitorBase {
  public:
   static void Initialize() {
     table_.Register(kVisitSeqAsciiString, &EvacuateSeqAsciiString);
     table_.Register(kVisitSeqTwoByteString, &EvacuateSeqTwoByteString);
     table_.Register(kVisitShortcutCandidate, &EvacuateShortcutCandidate);
     table_.Register(kVisitByteArray, &EvacuateByteArray);
     table_.Register(kVisitFixedArray, &EvacuateFixedArray);
+
     table_.Register(kVisitGlobalContext,
                     &ObjectEvacuationStrategy<POINTER_OBJECT>::
-                        VisitSpecialized<Context::kSize>);
-
-    typedef ObjectEvacuationStrategy<POINTER_OBJECT> PointerObject;
+                        template VisitSpecialized<Context::kSize>);
 
     table_.Register(kVisitConsString,
                     &ObjectEvacuationStrategy<POINTER_OBJECT>::
-                        VisitSpecialized<ConsString::kSize>);
+                        template VisitSpecialized<ConsString::kSize>);
 
     table_.Register(kVisitSharedFunctionInfo,
                     &ObjectEvacuationStrategy<POINTER_OBJECT>::
-                        VisitSpecialized<SharedFunctionInfo::kSize>);
+                        template VisitSpecialized<SharedFunctionInfo::kSize>);
 
     table_.Register(kVisitJSFunction,
                     &ObjectEvacuationStrategy<POINTER_OBJECT>::
-                    VisitSpecialized<JSFunction::kSize>);
+                        template VisitSpecialized<JSFunction::kSize>);
 
     table_.RegisterSpecializations<ObjectEvacuationStrategy<DATA_OBJECT>,
                                    kVisitDataObject,
                                    kVisitDataObjectGeneric>();
 
     table_.RegisterSpecializations<ObjectEvacuationStrategy<POINTER_OBJECT>,
                                    kVisitJSObject,
                                    kVisitJSObjectGeneric>();
 
     table_.RegisterSpecializations<ObjectEvacuationStrategy<POINTER_OBJECT>,
                                    kVisitStruct,
                                    kVisitStructGeneric>();
   }
 
-
-  static inline void Scavenge(Map* map, HeapObject** slot, HeapObject* obj) {
-    table_.GetVisitor(map)(map, slot, obj);
+  static VisitorDispatchTable<ScavengingCallback>* GetTable() {
+    return &table_;
   }
 
-
  private:
   enum ObjectContents  { DATA_OBJECT, POINTER_OBJECT };
   enum SizeRestriction { SMALL, UNKNOWN_SIZE };
 
 #if defined(DEBUG) || defined(ENABLE_LOGGING_AND_PROFILING)
   static void RecordCopiedObject(Heap* heap, HeapObject* obj) {
     bool should_record = false;
 #ifdef DEBUG
     should_record = FLAG_heap_stats;
 #endif
@@ skipping 16 matching lines @@
   INLINE(static HeapObject* MigrateObject(Heap* heap,
                                           HeapObject* source,
                                           HeapObject* target,
                                           int size)) {
     // Copy the content of source to target.
     heap->CopyBlock(target->address(), source->address(), size);
 
     // Set the forwarding address.
     source->set_map_word(MapWord::FromForwardingAddress(target));
 
+    if (logging_and_profiling_mode == LOGGING_AND_PROFILING_ENABLED) {
 #if defined(DEBUG) || defined(ENABLE_LOGGING_AND_PROFILING)
-    // Update NewSpace stats if necessary.
-    RecordCopiedObject(heap, target);
+      // Update NewSpace stats if necessary.
+      RecordCopiedObject(heap, target);
 #endif
-    HEAP_PROFILE(heap, ObjectMoveEvent(source->address(), target->address()));
+      HEAP_PROFILE(heap, ObjectMoveEvent(source->address(), target->address()));
 #if defined(ENABLE_LOGGING_AND_PROFILING)
-    Isolate* isolate = heap->isolate();
-    if (isolate->logger()->is_logging() ||
-        isolate->cpu_profiler()->is_profiling()) {
-      if (target->IsSharedFunctionInfo()) {
-        PROFILE(isolate, SharedFunctionInfoMoveEvent(
-            source->address(), target->address()));
+      Isolate* isolate = heap->isolate();
+      if (isolate->logger()->is_logging() ||
+          isolate->cpu_profiler()->is_profiling()) {
+        if (target->IsSharedFunctionInfo()) {
+          PROFILE(isolate, SharedFunctionInfoMoveEvent(
+              source->address(), target->address()));
+        }
       }
+#endif
     }
-#endif
+
     return target;
   }
 
 
   template<ObjectContents object_contents, SizeRestriction size_restriction>
   static inline void EvacuateObject(Map* map,
                                     HeapObject** slot,
                                     HeapObject* object,
                                     int object_size) {
     ASSERT((size_restriction != SMALL) ||
@@ skipping 95 matching lines @@
 
       MapWord first_word = first->map_word();
       if (first_word.IsForwardingAddress()) {
         HeapObject* target = first_word.ToForwardingAddress();
 
         *slot = target;
         object->set_map_word(MapWord::FromForwardingAddress(target));
         return;
       }
 
-      Scavenge(first->map(), slot, first);
+      DoScavengeObject(first->map(), slot, first);
       object->set_map_word(MapWord::FromForwardingAddress(*slot));
       return;
     }
 
     int object_size = ConsString::kSize;
     EvacuateObject<POINTER_OBJECT, SMALL>(map, slot, object, object_size);
   }
 
   template<ObjectContents object_contents>
   class ObjectEvacuationStrategy {
    public:
     template<int object_size>
     static inline void VisitSpecialized(Map* map,
                                         HeapObject** slot,
                                         HeapObject* object) {
       EvacuateObject<object_contents, SMALL>(map, slot, object, object_size);
     }
 
     static inline void Visit(Map* map,
                              HeapObject** slot,
                              HeapObject* object) {
       int object_size = map->instance_size();
       EvacuateObject<object_contents, SMALL>(map, slot, object, object_size);
     }
   };
 
-  typedef void (*Callback)(Map* map, HeapObject** slot, HeapObject* object);
-
-  static VisitorDispatchTable<Callback> table_;
+  static VisitorDispatchTable<ScavengingCallback> table_;
 };
 
 
-VisitorDispatchTable<ScavengingVisitor::Callback> ScavengingVisitor::table_;
+template<LoggingAndProfiling logging_and_profiling_mode>
+VisitorDispatchTable<ScavengingCallback>
+    ScavengingVisitor<logging_and_profiling_mode>::table_;
+
+
+static void InitializeScavengingVisitorsTables() {
+  ScavengingVisitor<LOGGING_AND_PROFILING_DISABLED>::Initialize();
+  ScavengingVisitor<LOGGING_AND_PROFILING_ENABLED>::Initialize();
+  scavenging_visitors_table_.CopyFrom(
+      ScavengingVisitor<LOGGING_AND_PROFILING_DISABLED>::GetTable());
+  scavenging_visitors_table_mode_ = LOGGING_AND_PROFILING_DISABLED;
+}
+
+
+void Heap::SwitchScavengingVisitorsTableIfProfilingWasEnabled() {
+  if (scavenging_visitors_table_mode_ == LOGGING_AND_PROFILING_ENABLED) {
+    // Table was already updated by some isolate.
+    return;
+  }
+
+  if (isolate()->logger()->is_logging() ||
+      isolate()->cpu_profiler()->is_profiling() ||
+      (isolate()->heap_profiler() != NULL &&
+       isolate()->heap_profiler()->is_profiling())) {
+    // If one of the isolates is doing scavenge at this moment of time
+    // it might see this table in an inconsitent state when
+    // some of the callbacks point to
+    // ScavengingVisitor<LOGGING_AND_PROFILING_ENABLED> and others
+    // to ScavengingVisitor<LOGGING_AND_PROFILING_DISABLED>.
+    // However this does not lead any bugs as such isolate does not have

[Vitaly Repeshko, 2011/03/30 15:11:04]

"lead to"

+    // profiling enabled and any isolate with enabled profiling is guaranteed
+    // to see table it in the consistent state.

[Vitaly Repeshko, 2011/03/30 15:11:04]

"table it" -> "the table"

+    scavenging_visitors_table_.CopyFrom(
+        ScavengingVisitor<LOGGING_AND_PROFILING_ENABLED>::GetTable());
+
+    // We use Release_Store to prevent reordering of this write before writes
+    // to the table.
+    Release_Store(&scavenging_visitors_table_mode_,
+                  LOGGING_AND_PROFILING_ENABLED);
+  }
+}
 
 
 void Heap::ScavengeObjectSlow(HeapObject** p, HeapObject* object) {
   ASSERT(HEAP->InFromSpace(object));
   MapWord first_word = object->map_word();
   ASSERT(!first_word.IsForwardingAddress());
   Map* map = first_word.ToMap();
-  ScavengingVisitor::Scavenge(map, p, object);
+  DoScavengeObject(map, p, object);
 }
 
 
 MaybeObject* Heap::AllocatePartialMap(InstanceType instance_type,
                                       int instance_size) {
   Object* result;
   { MaybeObject* maybe_result = AllocateRawMap();
     if (!maybe_result->ToObject(&result)) return maybe_result;
   }
 
@@ skipping 3252 matching lines @@
   // Configuration is based on the flags new-space-size (really the semispace
   // size) and old-space-size if set or the initial values of semispace_size_
   // and old_generation_size_ otherwise.
   if (!configured_) {
     if (!ConfigureHeapDefault()) return false;
   }
 
   gc_initializer_mutex->Lock();
   static bool initialized_gc = false;
   if (!initialized_gc) {
       initialized_gc = true;

[Vitaly Repeshko, 2011/03/30 15:11:04]

nit: Is indentation off here?

-      ScavengingVisitor::Initialize();
+      InitializeScavengingVisitorsTables();
       NewSpaceScavenger::Initialize();
       MarkCompactCollector::Initialize();
   }
   gc_initializer_mutex->Unlock();
 
   MarkMapPointersAsEncoded(false);
 
   // Setup memory allocator and reserve a chunk of memory for new
   // space.  The chunk is double the size of the requested reserved
   // new space size to ensure that we can find a pair of semispaces that
@@ skipping 1009 matching lines @@
 }
 
 
 void ExternalStringTable::TearDown() {
   new_space_strings_.Free();
   old_space_strings_.Free();
 }
 
 
 } }  // namespace v8::internal