Sweep pages with lowest live memory first.

src/mark-compact.cc

Index: src/mark-compact.cc
diff --git a/src/mark-compact.cc b/src/mark-compact.cc
index fe0c685c6995ef39bd8ad6b3f74219194332b386..992c81c6010a24f1062f367ef5675e919509cf50 100644
--- a/src/mark-compact.cc
+++ b/src/mark-compact.cc
@@ -559,7 +559,9 @@ void MarkCompactCollector::WaitUntilSweepingCompleted() {
   StealMemoryFromSweeperThreads(heap()->paged_space(OLD_DATA_SPACE));
   StealMemoryFromSweeperThreads(heap()->paged_space(OLD_POINTER_SPACE));
   heap()->paged_space(OLD_DATA_SPACE)->ResetUnsweptFreeBytes();
+  heap()->paged_space(OLD_DATA_SPACE)->SetPagesToSweep(NULL);
   heap()->paged_space(OLD_POINTER_SPACE)->ResetUnsweptFreeBytes();
+  heap()->paged_space(OLD_POINTER_SPACE)->SetPagesToSweep(NULL);
 }
 
 
@@ -3828,9 +3830,9 @@ void MarkCompactCollector::SweepSpace(PagedSpace* space, SweeperType sweeper) {
             PrintF("Sweeping 0x%" V8PRIxPTR " conservatively.\n",
                    reinterpret_cast<intptr_t>(p));
           }
-          SweepConservatively<SWEEP_SEQUENTIALLY>(space, NULL, p);
+          space->SetPagesToSweep(p);
+          space->AdvanceSweeper(0);
           pages_swept++;
-          space->SetPagesToSweep(p->next_page());
           lazy_sweeping_active = true;
         }
         break;
@@ -3842,7 +3844,8 @@ void MarkCompactCollector::SweepSpace(PagedSpace* space, SweeperType sweeper) {
             PrintF("Sweeping 0x%" V8PRIxPTR " conservatively.\n",
                    reinterpret_cast<intptr_t>(p));
           }
-          SweepConservatively<SWEEP_SEQUENTIALLY>(space, NULL, p);
+          space->SetPagesToSweep(p);
+          space->AdvanceSweeper(0);
           pages_swept++;
           parallel_sweeping_active = true;
         } else {