Reduces memory consumption for parallel sweeping.

BUG=

Review URL: https://codereview.chromium.org/12177011

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@13652 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/mark-compact.cc

@@ -3854,22 +3854,21 @@ void MarkCompactCollector::SweepSpaces() {
   SweepSpace(heap()->old_pointer_space(), how_to_sweep);
   SweepSpace(heap()->old_data_space(), how_to_sweep);
 
-  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.
+    // 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();
+
   // 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.