Shrinking of PagedSpace is done only by sweeper.

src/heap.cc

Index: src/heap.cc
diff --git a/src/heap.cc b/src/heap.cc
index 9028989b8768440f1d36eaf479cc3cafe394d5f1..19750354e73baa4d92ff51c651c548d465836e70 100644
--- a/src/heap.cc
+++ b/src/heap.cc
@@ -591,7 +591,6 @@ void Heap::CollectAllAvailableGarbage(const char* gc_reason) {
   mark_compact_collector()->SetFlags(kNoGCFlags);
   new_space_.Shrink();
   UncommitFromSpace();
-  Shrink();
   incremental_marking()->UncommitMarkingDeque();
 }
 
@@ -788,11 +787,6 @@ void Heap::ReserveSpace(
 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.

[Michael Starzinger, 2013/02/26 18:19:54]

s/failed again/failed/

[Hannes Payer (out of office), 2013/02/27 10:15:29]

Done.

   // Memory is exhausted and we will die.
   V8::FatalProcessOutOfMemory("Committing semi space failed.");
@@ -822,7 +816,6 @@ void Heap::ClearJSFunctionResultCaches() {
 }
 
 
-
 void Heap::ClearNormalizedMapCaches() {
   if (isolate_->bootstrapper()->IsActive() &&
       !incremental_marking()->IsMarking()) {
@@ -6414,17 +6407,6 @@ void Heap::TearDown() {
 }
 
 
-void Heap::Shrink() {
-  // Try to shrink all paged spaces.
-  PagedSpaces spaces(this);
-  for (PagedSpace* space = spaces.next();
-       space != NULL;
-       space = spaces.next()) {
-    space->ReleaseAllUnusedPages();

[Michael Starzinger, 2013/02/26 18:19:54]

The PagedSpace::ReleaseAllUnusedPages() is no longer called either. Also remove
that one.

[Hannes Payer (out of office), 2013/02/27 10:15:29]

Done.

-  }
-}
-
-
 void Heap::AddGCPrologueCallback(GCPrologueCallback callback, GCType gc_type) {
   ASSERT(callback != NULL);
   GCPrologueCallbackPair pair(callback, gc_type);