Add basic support for parallel compaction and flag.

src/heap/mark-compact.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/heap/mark-compact.h"
 
 #include "src/base/atomicops.h"
 #include "src/base/bits.h"
 #include "src/code-stubs.h"
 #include "src/compilation-cache.h"
@@ skipping 30 matching lines @@
 MarkCompactCollector::MarkCompactCollector(Heap* heap)
     :  // NOLINT
 #ifdef DEBUG
       state_(IDLE),
 #endif
       marking_parity_(ODD_MARKING_PARITY),
       compacting_(false),
       was_marked_incrementally_(false),
       sweeping_in_progress_(false),
       pending_sweeper_jobs_semaphore_(0),
+      pending_compaction_jobs_semaphore_(0),
       evacuation_(false),
       migration_slots_buffer_(NULL),
       heap_(heap),
       marking_deque_memory_(NULL),
       marking_deque_memory_committed_(0),
       code_flusher_(NULL),
       have_code_to_deoptimize_(false) {
 }
 
 #ifdef VERIFY_HEAP
@@ skipping 391 matching lines @@
 
   LargeObjectIterator it(heap_->lo_space());
   for (HeapObject* obj = it.Next(); obj != NULL; obj = it.Next()) {
     Marking::MarkWhite(Marking::MarkBitFrom(obj));
     Page::FromAddress(obj->address())->ResetProgressBar();
     Page::FromAddress(obj->address())->ResetLiveBytes();
   }
 }
 
 
+class MarkCompactCollector::CompactionTask : public v8::Task {
+ public:
+  explicit CompactionTask(Heap* heap) : heap_(heap) {}
+
+  virtual ~CompactionTask() {}
+
+ private:
+  // v8::Task overrides.
+  void Run() override {
+    // TODO(mlippautz, hpayer): EvacuatePages is not thread-safe and can just be
+    // called by one thread concurrently.
+    heap_->mark_compact_collector()->EvacuatePages();
+    heap_->mark_compact_collector()
+        ->pending_compaction_jobs_semaphore_.Signal();
+  }
+
+  Heap* heap_;
+
+  DISALLOW_COPY_AND_ASSIGN(CompactionTask);
+};
+
+
 class MarkCompactCollector::SweeperTask : public v8::Task {
  public:
   SweeperTask(Heap* heap, PagedSpace* space) : heap_(heap), space_(space) {}
 
   virtual ~SweeperTask() {}
 
  private:
   // v8::Task overrides.
   void Run() override {
     heap_->mark_compact_collector()->SweepInParallel(space_, 0);
@@ skipping 2810 matching lines @@
       DCHECK(object->map_word().IsForwardingAddress());
     }
 
     // Clear marking bits for current cell.
     *cell = 0;
   }
   p->ResetLiveBytes();
 }
 
 
+void MarkCompactCollector::EvacuatePagesInParallel() {
+  V8::GetCurrentPlatform()->CallOnBackgroundThread(
+      new CompactionTask(heap()), v8::Platform::kShortRunningTask);
+}
+
+
 void MarkCompactCollector::EvacuatePages() {
   int npages = evacuation_candidates_.length();
   int abandoned_pages = 0;
   for (int i = 0; i < npages; i++) {
     Page* p = evacuation_candidates_[i];
     DCHECK(p->IsEvacuationCandidate() ||
            p->IsFlagSet(Page::RESCAN_ON_EVACUATION));
     DCHECK(static_cast<int>(p->parallel_sweeping()) ==
            MemoryChunk::SWEEPING_DONE);
     PagedSpace* space = static_cast<PagedSpace*>(p->owner());
@@ skipping 286 matching lines @@
     GCTracer::Scope gc_scope(heap()->tracer(),
                              GCTracer::Scope::MC_SWEEP_NEWSPACE);
     EvacuationScope evacuation_scope(this);
     EvacuateNewSpace();
   }
 
   {
     GCTracer::Scope gc_scope(heap()->tracer(),
                              GCTracer::Scope::MC_EVACUATE_PAGES);
     EvacuationScope evacuation_scope(this);
-    EvacuatePages();
+    if (FLAG_parallel_compaction) {
+      EvacuatePagesInParallel();
+      pending_compaction_jobs_semaphore_.Wait();
+    } else {
+      EvacuatePages();
+    }
   }
 
   // Second pass: find pointers to new space and update them.
   PointersUpdatingVisitor updating_visitor(heap());
 
   {
     GCTracer::Scope gc_scope(heap()->tracer(),
                              GCTracer::Scope::MC_UPDATE_NEW_TO_NEW_POINTERS);
     // Update pointers in to space.
     SemiSpaceIterator to_it(heap()->new_space());
@@ skipping 1087 matching lines @@
   SlotsBuffer* buffer = *buffer_address;
   while (buffer != NULL) {
     SlotsBuffer* next_buffer = buffer->next();
     DeallocateBuffer(buffer);
     buffer = next_buffer;
   }
   *buffer_address = NULL;
 }
 }  // namespace internal
 }  // namespace v8