Adjust idle notification handler to do full GC at the end of idle round in...

Adjust idle notification handler to do full GC at the end of idle round in order to compact code space.

R=mstarzinger@chromium.org

Review URL: https://chromiumcodereview.appspot.com/10639002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@11900 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/heap.cc

@@ -5014,7 +5014,11 @@ void Heap::AdvanceIdleIncrementalMarking(intptr_t step_size) {
 
 
 bool Heap::IdleNotification(int hint) {
+  // Hints greater than this value indicate that
+  // the embedder is requesting a lot of GC work.
   const int kMaxHint = 1000;
+  // Minimal hint that allows to do full GC.
+  const int kMinHintForFullGC = 100;
   intptr_t size_factor = Min(Max(hint, 20), kMaxHint) / 4;
   // The size factor is in range [5..250]. The numbers here are chosen from
   // experiments. If you changes them, make sure to test with
@@ -5082,16 +5086,30 @@ bool Heap::IdleNotification(int hint) {
   mark_sweeps_since_idle_round_started_ += new_mark_sweeps;
   ms_count_at_last_idle_notification_ = ms_count_;
 
-  if (mark_sweeps_since_idle_round_started_ >= kMaxMarkSweepsInIdleRound) {
+  int remaining_mark_sweeps = kMaxMarkSweepsInIdleRound -
+                              mark_sweeps_since_idle_round_started_;
+
+  if (remaining_mark_sweeps <= 0) {
     FinishIdleRound();
     return true;
   }
 
   if (incremental_marking()->IsStopped()) {
-    incremental_marking()->Start();
+    // If there are no more than two GCs left in this idle round and we are
+    // allowed to do a full GC, then make those GCs full in order to compact
+    // the code space.
+    // TODO(ulan): Once we enable code compaction for incremental marking,
+    // we can get rid of this special case and always start incremental marking.
+    if (remaining_mark_sweeps <= 2 && hint >= kMinHintForFullGC) {
+      CollectAllGarbage(kReduceMemoryFootprintMask,
+                        "idle notification: finalize idle round");
+    } else {
+      incremental_marking()->Start();
+    }
+  }
+  if (!incremental_marking()->IsStopped()) {
+    AdvanceIdleIncrementalMarking(step_size);
   }
-
-  AdvanceIdleIncrementalMarking(step_size);
   return false;
 }