The sweeper thread should not write the page flags. Added a sweeping complete phase, where the main thread writes the given page flags.

BUG=
R=jarin@chromium.org, jochen@chromium.org

Review URL: https://codereview.chromium.org/163683003

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@19377 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/mark-compact.cc

@@ -622,6 +622,7 @@ void MarkCompactCollector::WaitUntilSweepingCompleted() {
     pending_sweeper_jobs_semaphore_.Wait();
     pending_sweeper_jobs_semaphore_.Wait();
   }
+  ParallelSweepSpacesComplete();
   sweeping_pending_ = false;
   RefillFreeLists(heap()->paged_space(OLD_DATA_SPACE));
   RefillFreeLists(heap()->paged_space(OLD_POINTER_SPACE));
@@ -3946,7 +3947,11 @@ intptr_t MarkCompactCollector::SweepConservatively(PagedSpace* space,
          (mode == MarkCompactCollector::SWEEP_SEQUENTIALLY &&
          free_list == NULL));
 
-  p->MarkSweptConservatively();
+  // When parallel sweeping is active, the page will be marked after
+  // sweeping by the main thread.
+  if (mode != MarkCompactCollector::SWEEP_IN_PARALLEL) {
+    p->MarkSweptConservatively();
+  }
 
   intptr_t freed_bytes = 0;
   size_t size = 0;
@@ -4058,7 +4063,7 @@ void MarkCompactCollector::SweepSpace(PagedSpace* space, SweeperType sweeper) {
   while (it.has_next()) {
     Page* p = it.next();
 
-    ASSERT(p->parallel_sweeping() == 0);
+    ASSERT(p->parallel_sweeping() == MemoryChunk::PARALLEL_SWEEPING_DONE);
     ASSERT(!p->IsEvacuationCandidate());
 
     // Clear sweeping flags indicating that marking bits are still intact.
@@ -4131,7 +4136,7 @@ void MarkCompactCollector::SweepSpace(PagedSpace* space, SweeperType sweeper) {
             PrintF("Sweeping 0x%" V8PRIxPTR " conservatively in parallel.\n",
                    reinterpret_cast<intptr_t>(p));
           }
-          p->set_parallel_sweeping(1);
+          p->set_parallel_sweeping(MemoryChunk::PARALLEL_SWEEPING_PENDING);
           space->IncreaseUnsweptFreeBytes(p);
         }
         break;
@@ -4223,6 +4228,24 @@ void MarkCompactCollector::SweepSpaces() {
 }
 
 
+void MarkCompactCollector::ParallelSweepSpaceComplete(PagedSpace* space) {
+  PageIterator it(space);
+  while (it.has_next()) {
+    Page* p = it.next();
+    if (p->parallel_sweeping() == MemoryChunk::PARALLEL_SWEEPING_IN_PROGRESS) {
+      p->set_parallel_sweeping(MemoryChunk::PARALLEL_SWEEPING_DONE);
+      p->MarkSweptConservatively();
+    }
+  }
+}
+
+
+void MarkCompactCollector::ParallelSweepSpacesComplete() {
+  ParallelSweepSpaceComplete(heap()->old_pointer_space());
+  ParallelSweepSpaceComplete(heap()->old_data_space());
+}
+
+
 void MarkCompactCollector::EnableCodeFlushing(bool enable) {
 #ifdef ENABLE_DEBUGGER_SUPPORT
   if (isolate()->debug()->IsLoaded() ||

src/mark-compact.h

@@ -944,6 +944,12 @@ class MarkCompactCollector {
 
   void SweepSpace(PagedSpace* space, SweeperType sweeper);
 
+  // Finalizes the parallel sweeping phase. Marks all the pages that were
+  // swept in parallel.
+  void ParallelSweepSpacesComplete();
+
+  void ParallelSweepSpaceComplete(PagedSpace* space);
+
 #ifdef DEBUG
   friend class MarkObjectVisitor;
   static void VisitObject(HeapObject* obj);

src/spaces.cc

@@ -483,7 +483,7 @@ MemoryChunk* MemoryChunk::Initialize(Heap* heap,
   chunk->write_barrier_counter_ = kWriteBarrierCounterGranularity;
   chunk->progress_bar_ = 0;
   chunk->high_water_mark_ = static_cast<int>(area_start - base);
-  chunk->parallel_sweeping_ = 0;
+  chunk->set_parallel_sweeping(PARALLEL_SWEEPING_DONE);
   chunk->available_in_small_free_list_ = 0;
   chunk->available_in_medium_free_list_ = 0;
   chunk->available_in_large_free_list_ = 0;

src/spaces.h

@@ -467,16 +467,32 @@ class MemoryChunk {
   // Return all current flags.
   intptr_t GetFlags() { return flags_; }
 
-  intptr_t parallel_sweeping() const {
-    return parallel_sweeping_;
+
+  // PARALLEL_SWEEPING_PENDING - This page is ready for parallel sweeping.
+  // PARALLEL_SWEEPING_IN_PROGRESS - This page is currently swept or was
+  // swept by a sweeper thread.
+  // PARALLEL_SWEEPING_DONE - The page state when sweeping is complete or
+  // sweeping must not be performed on that page.
+  enum ParallelSweepingState {
+    PARALLEL_SWEEPING_DONE,
+    PARALLEL_SWEEPING_IN_PROGRESS,
+    PARALLEL_SWEEPING_PENDING
+  };
+
+  ParallelSweepingState parallel_sweeping() {
+    return static_cast<ParallelSweepingState>(
+        NoBarrier_Load(&parallel_sweeping_));
   }
 
-  void set_parallel_sweeping(intptr_t state) {
-    parallel_sweeping_ = state;
+  void set_parallel_sweeping(ParallelSweepingState state) {
+    NoBarrier_Store(&parallel_sweeping_, state);
   }
 
   bool TryParallelSweeping() {
-    return NoBarrier_CompareAndSwap(&parallel_sweeping_, 1, 0) == 1;
+    return NoBarrier_CompareAndSwap(&parallel_sweeping_,
+                                    PARALLEL_SWEEPING_PENDING,
+                                    PARALLEL_SWEEPING_IN_PROGRESS) ==
+                                        PARALLEL_SWEEPING_PENDING;
   }
 
   // Manage live byte count (count of bytes known to be live,
@@ -711,7 +727,7 @@ class MemoryChunk {
   // count highest number of bytes ever allocated on the page.
   int high_water_mark_;
 
-  intptr_t parallel_sweeping_;
+  AtomicWord parallel_sweeping_;
 
   // PagedSpace free-list statistics.
   intptr_t available_in_small_free_list_;