Reduces memory consumption for parallel sweeping.

src/mark-compact.cc

 // Copyright 2012 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 3836 matching lines @@
   if (sweep_precisely_) how_to_sweep = PRECISE;
   // Noncompacting collections simply sweep the spaces to clear the mark
   // bits and free the nonlive blocks (for old and map spaces).  We sweep
   // the map space last because freeing non-live maps overwrites them and
   // the other spaces rely on possibly non-live maps to get the sizes for
   // non-live objects.
 
   SweepSpace(heap()->old_pointer_space(), how_to_sweep);
   SweepSpace(heap()->old_data_space(), how_to_sweep);
 
+  if (how_to_sweep == PARALLEL_CONSERVATIVE) {
+    // TODO(hpayer): fix race with concurrent sweeper
+    StartSweeperThreads();
+    if (FLAG_parallel_sweeping && !FLAG_concurrent_sweeping) {
+      WaitUntilSweepingCompleted();
+    }
+  }
+
   RemoveDeadInvalidatedCode();
   SweepSpace(heap()->code_space(), PRECISE);
 
   SweepSpace(heap()->cell_space(), PRECISE);
 
   EvacuateNewSpaceAndCandidates();
 
-  if (how_to_sweep == PARALLEL_CONSERVATIVE) {
-    // TODO(hpayer): The starting of the sweeper threads should be after
-    // SweepSpace old data space.
-    StartSweeperThreads();
-    if (FLAG_parallel_sweeping && !FLAG_concurrent_sweeping) {
-      WaitUntilSweepingCompleted();
-    }
-  }
-
   // ClearNonLiveTransitions depends on precise sweeping of map space to
   // detect whether unmarked map became dead in this collection or in one
   // of the previous ones.
   SweepSpace(heap()->map_space(), PRECISE);
 
   // Deallocate unmarked objects and clear marked bits for marked objects.
   heap_->lo_space()->FreeUnmarkedObjects();
 }
 
 
@@ skipping 187 matching lines @@
   while (buffer != NULL) {
     SlotsBuffer* next_buffer = buffer->next();
     DeallocateBuffer(buffer);
     buffer = next_buffer;
   }
   *buffer_address = NULL;
 }
 
 
 } }  // namespace v8::internal