Introduce lazy sweeping.

src/heap.cc

 // Copyright 2011 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 460 matching lines @@
 #endif
 
   if (collector == SCAVENGER && !incremental_marking()->IsStopped()) {
     if (FLAG_trace_incremental_marking) {
       PrintF("[IncrementalMarking] Scavenge during marking.\n");
     }
   }
 
   if (collector == MARK_COMPACTOR &&
       !mark_compact_collector()->PreciseSweepingRequired() &&
-      incremental_marking()->IsMarking() &&
+      incremental_marking()->IsMarkingIncomplete() &&
       !incremental_marking()->should_hurry() &&
       FLAG_incremental_marking_steps) {
     if (FLAG_trace_incremental_marking) {
       PrintF("[IncrementalMarking] Delaying MarkSweep.\n");
     }
     collector = SCAVENGER;
   }
 
   bool next_gc_likely_to_collect_more = false;
 
@@ skipping 504 matching lines @@
 
   // Used for updating survived_since_last_expansion_ at function end.
   intptr_t survived_watermark = PromotedSpaceSize();
 
   CheckNewSpaceExpansionCriteria();
 
   SelectScavengingVisitorsTable();
 
   incremental_marking()->PrepareForScavenge();
 
+  old_pointer_space()->AdvanceSweeper(new_space_.Size());
+  old_data_space()->AdvanceSweeper(new_space_.Size());
+
   // Flip the semispaces.  After flipping, to space is empty, from space has
   // live objects.
   new_space_.Flip();
   new_space_.ResetAllocationInfo();
 
   // We need to sweep newly copied objects which can be either in the
   // to space or promoted to the old generation.  For to-space
   // objects, we treat the bottom of the to space as a queue.  Newly
   // copied and unswept objects lie between a 'front' mark and the
   // allocation pointer.
@@ skipping 4878 matching lines @@
 }
 
 
 void ExternalStringTable::TearDown() {
   new_space_strings_.Free();
   old_space_strings_.Free();
 }
 
 
 } }  // namespace v8::internal