- Added simple memory reduction behavior for IdleNotification.

- This also include a one line change approved by lrh.
     http://codereview.chromium.org/164469

Review URL: http://codereview.chromium.org/165448

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@2677 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/flag-definitions.h

@@ -161,6 +161,9 @@ DEFINE_bool(trace_gc_verbose, false,
 DEFINE_bool(collect_maps, true,
             "garbage collect maps from which no objects can be reached")
 
+// v8.cc
+DEFINE_bool(use_idle_notification, true,
+            "Use idle notification to reduce memory footprint.")
 // ic.cc
 DEFINE_bool(use_ic, true, "use inline caching")
 

src/heap.cc

@@ -425,6 +425,20 @@ static void VerifySymbolTable() {
 }
 
 
+void Heap::EnsureFromSpaceIsCommitted() {
+  if (new_space_.CommitFromSpaceIfNeeded()) return;
+
+  // Committing memory to from space failed.
+  // Try shrinking and try again.
+  Shrink();
+  if (new_space_.CommitFromSpaceIfNeeded()) return;
+
+  // Committing memory to from space failed again.
+  // Memory is exhausted and we will die.
+  V8::FatalProcessOutOfMemory("Committing semi space failed.");
+}
+
+
 void Heap::PerformGarbageCollection(AllocationSpace space,
                                     GarbageCollector collector,
                                     GCTracer* tracer) {
@@ -433,7 +447,7 @@ void Heap::PerformGarbageCollection(AllocationSpace space,
     ASSERT(!allocation_allowed_);
     global_gc_prologue_callback_();
   }
-
+  EnsureFromSpaceIsCommitted();
   if (collector == MARK_COMPACTOR) {
     MarkCompact(tracer);
 

src/heap.h

@@ -280,6 +280,9 @@ class Heap : public AllStatic {
     return new_space_.allocation_limit_address();
   }
 
+  // Uncommit unused semi space.
+  static bool UncommitFromSpace() { return new_space_.UncommitFromSpace(); }
+
 #ifdef ENABLE_HEAP_PROTECTION
   // Protect/unprotect the heap by marking all spaces read-only/writable.
   static void Protect();
@@ -794,6 +797,9 @@ class Heap : public AllStatic {
   // Rebuild remembered set in old and map spaces.
   static void RebuildRSets();
 
+  // Commits from space if it is uncommitted.
+  static void EnsureFromSpaceIsCommitted();
+
   //
   // Support for the API.
   //

src/spaces.h

@@ -367,6 +367,13 @@ class MemoryAllocator : public AllStatic {
   // and false otherwise.
   static bool CommitBlock(Address start, size_t size, Executability executable);
 
+
+  // Uncommit a contiguous block of memory [start..(start+size)[.
+  // start is not NULL, the size is greater than zero, and the
+  // block is contained in the initial chunk.  Returns true if it succeeded
+  // and false otherwise.
+  static bool UncommitBlock(Address start, size_t size);
+
   // Attempts to allocate the requested (non-zero) number of pages from the
   // OS.  Fewer pages might be allocated than requested. If it fails to
   // allocate memory for the OS or cannot allocate a single page, this
@@ -1035,6 +1042,10 @@ class SemiSpace : public Space {
     return 0;
   }
 
+  bool is_committed() { return committed_; }
+  bool Commit();
+  bool Uncommit();
+
 #ifdef DEBUG
   virtual void Print();
   virtual void Verify();
@@ -1058,6 +1069,8 @@ class SemiSpace : public Space {
   uintptr_t object_mask_;
   uintptr_t object_expected_;
 
+  bool committed_;
+
  public:
   TRACK_MEMORY("SemiSpace")
 };
@@ -1250,6 +1263,17 @@ class NewSpace : public Space {
   void RecordPromotion(HeapObject* obj);
 #endif
 
+  // Return whether the operation succeded.
+  bool CommitFromSpaceIfNeeded() {
+    if (from_space_.is_committed()) return true;
+    return from_space_.Commit();
+  }
+
+  bool UncommitFromSpace() {
+    if (!from_space_.is_committed()) return true;
+    return from_space_.Uncommit();
+  }
+
  private:
   // The current and maximum capacities of a semispace.
   int capacity_;

src/v8.cc

@@ -157,7 +157,12 @@ uint32_t V8::Random() {
 }
 
 void V8::IdleNotification(bool is_high_priority) {
-  // todo(bak): Reduce memory footprint.
+  if (!FLAG_use_idle_notification) return;
+  // Ignore high priority instances of V8.
+  if (is_high_priority) return;
+
+  // Uncommit unused memory in new space.
+  Heap::UncommitFromSpace();
 }