[heap] Add more tasks for parallel compaction

src/heap/mark-compact.cc

Index: src/heap/mark-compact.cc
diff --git a/src/heap/mark-compact.cc b/src/heap/mark-compact.cc
index 7f98b33ec508509c858f20078a5548009ed9d941..96a10c5d30d5afbaba9f53c22278388ba7552932 100644
--- a/src/heap/mark-compact.cc
+++ b/src/heap/mark-compact.cc
@@ -3370,23 +3370,22 @@ bool MarkCompactCollector::EvacuateLiveObjectsFromPage(
 void MarkCompactCollector::EvacuatePagesInParallel() {
   if (evacuation_candidates_.length() == 0) return;
 
-  int num_tasks = 1;
-  if (FLAG_parallel_compaction) {
-    num_tasks = NumberOfParallelCompactionTasks();
-  }
+  const int num_tasks = NumberOfParallelCompactionTasks();
 
   // Set up compaction spaces.
   CompactionSpaceCollection** compaction_spaces_for_tasks =
       new CompactionSpaceCollection*[num_tasks];
+  FreeList** free_lists = new FreeList*[2 * num_tasks];
   for (int i = 0; i < num_tasks; i++) {
     compaction_spaces_for_tasks[i] = new CompactionSpaceCollection(heap());
+    free_lists[i] = compaction_spaces_for_tasks[i]->Get(OLD_SPACE)->free_list();
+    free_lists[i + num_tasks] =
+        compaction_spaces_for_tasks[i]->Get(CODE_SPACE)->free_list();
   }
-
-  compaction_spaces_for_tasks[0]->Get(OLD_SPACE)->MoveOverFreeMemory(
-      heap()->old_space());
-  compaction_spaces_for_tasks[0]
-      ->Get(CODE_SPACE)
-      ->MoveOverFreeMemory(heap()->code_space());
+  heap()->old_space()->free_list()->Divide(free_lists, num_tasks, 1 * MB);
+  heap()->code_space()->free_list()->Divide(&free_lists[num_tasks], num_tasks,
+                                            1 * MB);
+  delete[] free_lists;
 
   compaction_in_progress_ = true;
   // Kick off parallel tasks.
@@ -3397,10 +3396,8 @@ void MarkCompactCollector::EvacuatePagesInParallel() {
         v8::Platform::kShortRunningTask);
   }
 
-  // Contribute in main thread. Counter and signal are in principal not needed.
-  concurrent_compaction_tasks_active_++;
+  // Contribute in main thread.

[Hannes Payer (out of office), 2015/09/23 07:26:03]

// Perform compaction on the main thread.

[Michael Lippautz, 2015/09/23 07:40:50]

Done.

   EvacuatePages(compaction_spaces_for_tasks[0], &migration_slots_buffer_);
-  pending_compaction_tasks_semaphore_.Signal();
 
   WaitUntilCompactionCompleted();