Clean JS function results cache on each major GC.

We don't want to retain cached objects for too long.

Review URL: http://codereview.chromium.org/1780001

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@4582 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/bootstrapper.cc

@@ -1335,14 +1335,12 @@ bool Genesis::InstallNatives() {
 static FixedArray* CreateCache(int size, JSFunction* factory) {
   // Caches are supposed to live for a long time, allocate in old space.
   int array_size = JSFunctionResultCache::kEntriesIndex + 2 * size;
-  Handle<FixedArray> cache =
-      Factory::NewFixedArrayWithHoles(array_size, TENURED);
+  // Cannot use cast as object is not fully initialized yet.
+  JSFunctionResultCache* cache = reinterpret_cast<JSFunctionResultCache*>(
+      *Factory::NewFixedArrayWithHoles(array_size, TENURED));
   cache->set(JSFunctionResultCache::kFactoryIndex, factory);
-  cache->set(JSFunctionResultCache::kFingerIndex,
-      Smi::FromInt(JSFunctionResultCache::kEntriesIndex));
-  cache->set(JSFunctionResultCache::kCacheSizeIndex,
-      Smi::FromInt(JSFunctionResultCache::kEntriesIndex));
-  return *cache;
+  cache->MakeZeroSize();
+  return cache;
 }
 
 

src/heap.cc

@@ -306,6 +306,7 @@ void Heap::ReportStatisticsAfterGC() {
 
 void Heap::GarbageCollectionPrologue() {
   TranscendentalCache::Clear();
+  ClearJSFunctionResultCaches();
   gc_count_++;
   unflattened_strings_length_ = 0;
 #ifdef DEBUG
@@ -541,6 +542,28 @@ void Heap::EnsureFromSpaceIsCommitted() {
 }
 
 
+class ClearThreadJSFunctionResultCachesVisitor: public ThreadVisitor  {
+  virtual void VisitThread(ThreadLocalTop* top) {
+    Context* context = top->context_;
+    if (context == NULL) return;
+
+    FixedArray* caches =
+      context->global()->global_context()->jsfunction_result_caches();
+    int length = caches->length();
+    for (int i = 0; i < length; i++) {
+      JSFunctionResultCache::cast(caches->get(i))->Clear();
+    }
+  }
+};
+
+
+void Heap::ClearJSFunctionResultCaches() {
+  if (Bootstrapper::IsActive()) return;
+  ClearThreadJSFunctionResultCachesVisitor visitor;
+  ThreadManager::IterateThreads(&visitor);
+}
+
+
 void Heap::PerformGarbageCollection(AllocationSpace space,
                                     GarbageCollector collector,
                                     GCTracer* tracer) {

src/heap.h

@@ -1178,6 +1178,8 @@ class Heap : public AllStatic {
                                           HeapObject* target,
                                           int size);
 
+  static void ClearJSFunctionResultCaches();
+
 #if defined(DEBUG) || defined(ENABLE_LOGGING_AND_PROFILING)
   // Record the copy of an object in the NewSpace's statistics.
   static void RecordCopiedObject(HeapObject* obj);

src/objects-debug.cc

@@ -1328,6 +1328,32 @@ bool DescriptorArray::IsSortedNoDuplicates() {
 }
 
 
+void JSFunctionResultCache::JSFunctionResultCacheVerify() {
+  JSFunction::cast(get(kFactoryIndex))->Verify();
+
+  int size = Smi::cast(get(kCacheSizeIndex))->value();
+  ASSERT(kEntriesIndex <= size);
+  ASSERT(size <= length());
+  ASSERT_EQ(0, size % kEntrySize);
+
+  int finger = Smi::cast(get(kFingerIndex))->value();
+  ASSERT(kEntriesIndex <= finger);
+  ASSERT(finger < size || finger == kEntriesIndex);
+  ASSERT_EQ(0, finger % kEntrySize);
+
+  if (FLAG_enable_slow_asserts) {
+    for (int i = kEntriesIndex; i < size; i++) {
+      ASSERT(!get(i)->IsTheHole());
+      get(i)->Verify();
+    }
+    for (int i = size; i < length(); i++) {
+      ASSERT(get(i)->IsTheHole());
+      get(i)->Verify();
+    }
+  }
+}
+
+
 #endif  // DEBUG
 
 } }  // namespace v8::internal

src/objects-inl.h

@@ -569,6 +569,22 @@ bool Object::IsSymbolTable() {
 }
 
 
+bool Object::IsJSFunctionResultCache() {
+  if (!IsFixedArray()) return false;
+  FixedArray* self = FixedArray::cast(this);
+  int length = self->length();
+  if (length < JSFunctionResultCache::kEntriesIndex) return false;
+  if ((length - JSFunctionResultCache::kEntriesIndex)
+      % JSFunctionResultCache::kEntrySize != 0) {
+    return false;
+  }
+#ifdef DEBUG
+  reinterpret_cast<JSFunctionResultCache*>(this)->JSFunctionResultCacheVerify();
+#endif
+  return true;
+}
+
+
 bool Object::IsCompilationCacheTable() {
   return IsHashTable();
 }
@@ -1594,6 +1610,7 @@ void NumberDictionary::set_requires_slow_elements() {
 CAST_ACCESSOR(FixedArray)
 CAST_ACCESSOR(DescriptorArray)
 CAST_ACCESSOR(SymbolTable)
+CAST_ACCESSOR(JSFunctionResultCache)
 CAST_ACCESSOR(CompilationCacheTable)
 CAST_ACCESSOR(CodeCacheHashTable)
 CAST_ACCESSOR(MapCache)
@@ -1836,6 +1853,20 @@ void ExternalTwoByteString::set_resource(
 }
 
 
+void JSFunctionResultCache::MakeZeroSize() {
+  set(kFingerIndex, Smi::FromInt(kEntriesIndex));
+  set(kCacheSizeIndex, Smi::FromInt(kEntriesIndex));
+}
+
+
+void JSFunctionResultCache::Clear() {
+  int cache_size = Smi::cast(get(kCacheSizeIndex))->value();
+  Object** entries_start = RawField(this, OffsetOfElementAt(kEntriesIndex));
+  MemsetPointer(entries_start, Heap::the_hole_value(), cache_size);
+  MakeZeroSize();
+}
+
+
 byte ByteArray::get(int index) {
   ASSERT(index >= 0 && index < this->length());
   return READ_BYTE_FIELD(this, kHeaderSize + index * kCharSize);

src/objects.h

@@ -606,6 +606,7 @@ class Object BASE_EMBEDDED {
   inline bool IsHashTable();
   inline bool IsDictionary();
   inline bool IsSymbolTable();
+  inline bool IsJSFunctionResultCache();
   inline bool IsCompilationCacheTable();
   inline bool IsCodeCacheHashTable();
   inline bool IsMapCache();
@@ -2326,6 +2327,16 @@ class JSFunctionResultCache: public FixedArray {
   static const int kEntriesIndex = kDummyIndex + 1;
 
   static const int kEntrySize = 2;  // key + value
+
+  inline void MakeZeroSize();
+  inline void Clear();
+
+  // Casting
+  static inline JSFunctionResultCache* cast(Object* obj);
+
+#ifdef DEBUG
+  void JSFunctionResultCacheVerify();
+#endif
 };
 
 

test/cctest/test-threads.cc

@@ -50,3 +50,87 @@ TEST(Preemption) {
 
   script->Run();
 }
+
+
+enum Turn {
+  FILL_CACHE,
+  CLEAN_CACHE,
+  SECOND_TIME_FILL_CACHE,
+  DONE
+};
+
+static Turn turn = FILL_CACHE;
+
+
+class ThreadA: public v8::internal::Thread {
+ public:
+  void Run() {
+    v8::Locker locker;
+    v8::HandleScope scope;
+    v8::Context::Scope context_scope(v8::Context::New());
+
+    CHECK_EQ(FILL_CACHE, turn);
+
+    // Fill String.search cache.
+    v8::Handle<v8::Script> script = v8::Script::Compile(
+        v8::String::New(
+          "for (var i = 0; i < 3; i++) {"
+          "  var result = \"a\".search(\"a\");"
+          "  if (result != 0) throw \"result: \" + result + \" @\" + i;"
+          "};"
+          "true"));
+    CHECK(script->Run()->IsTrue());
+
+    turn = CLEAN_CACHE;
+    do {
+      {
+        v8::Unlocker unlocker;
+        Thread::YieldCPU();
+      }
+    } while (turn != SECOND_TIME_FILL_CACHE);
+
+    // Rerun the script.
+    CHECK(script->Run()->IsTrue());
+
+    turn = DONE;
+  }
+};
+
+
+class ThreadB: public v8::internal::Thread {
+ public:
+  void Run() {
+    do {
+      {
+        v8::Locker locker;
+        if (turn == CLEAN_CACHE) {
+          v8::HandleScope scope;
+          v8::Context::Scope context_scope(v8::Context::New());
+
+          // Clear the caches by forcing major GC.
+          v8::internal::Heap::CollectAllGarbage(false);
+          turn = SECOND_TIME_FILL_CACHE;
+          break;
+        }
+      }
+
+      Thread::YieldCPU();
+    } while (true);
+  }
+};
+
+
+TEST(JSFunctionResultCachesInTwoThreads) {
+  v8::V8::Initialize();
+
+  ThreadA threadA;
+  ThreadB threadB;
+
+  threadA.Start();
+  threadB.Start();
+
+  threadA.Join();
+  threadB.Join();
+
+  CHECK_EQ(DONE, turn);
+}