[heap] Add more tasks for parallel compaction

src/heap/spaces.h

Index: src/heap/spaces.h
diff --git a/src/heap/spaces.h b/src/heap/spaces.h
index b8fc9b7efe0845d4852b6660c8465abdda18f115..9a9a9a739511d8e7b9e38c337bb08ba90f41fad2 100644
--- a/src/heap/spaces.h
+++ b/src/heap/spaces.h
@@ -1694,6 +1694,8 @@ class FreeList {
   PagedSpace* owner() { return owner_; }
 
  private:
+  enum FreeListCategoryType { kSmall, kMedium, kLarge, kHuge };
+
   // The size range of blocks, in bytes.
   static const int kMinBlockSize = 3 * kPointerSize;
   static const int kMaxBlockSize = Page::kMaxRegularHeapObjectSize;
@@ -1707,6 +1709,27 @@ class FreeList {
   static const int kLargeAllocationMax = kMediumListMax;
 
   FreeSpace* FindNodeFor(int size_in_bytes, int* node_size);
+  FreeSpace* FindNodeIn(FreeListCategoryType category, int* node_size);
+
+  FreeListCategory* GetFreeListCategory(FreeListCategoryType category) {
+    switch (category) {
+      case kSmall:
+        return &small_list_;
+      case kMedium:
+        return &medium_list_;
+      case kLarge:
+        return &large_list_;
+      case kHuge:
+        return &huge_list_;
+      default:
+        UNREACHABLE();
+    }
+    UNREACHABLE();
+    return nullptr;
+  }
+
+  void UpdateFragmentationStats(FreeListCategoryType category, Address address,
+                                int size);
 
   PagedSpace* owner_;
   Heap* heap_;
@@ -1715,6 +1738,8 @@ class FreeList {
   FreeListCategory large_list_;
   FreeListCategory huge_list_;
 
+  friend class PagedSpace;
+
   DISALLOW_IMPLICIT_CONSTRUCTORS(FreeList);
 };
 
@@ -1997,6 +2022,22 @@ class PagedSpace : public Space {
 
   virtual bool is_local() { return false; }
 
+  // Divide {this} free lists up among {other_free_lists} up to some certain
+  // {limit} of bytes. Note that this operation eventually needs to iterate
+  // over nodes one-by-one, making it a potentially slow operation.
+  void DivideFreeLists(FreeList** other_free_lists, int num, intptr_t limit);
+
+  // Adds memory starting at {start} of {size_in_bytes} to the space.
+  void AddMemory(Address start, int size_in_bytes) {
+    IncreaseCapacity(size_in_bytes);
+    Free(start, size_in_bytes);
+  }
+
+  // Tries to remove some memory from {this} free lists. We try to remove
+  // as much memory as possible, i.e., we check the free lists from huge
+  // to small.
+  FreeSpace* TryRemoveMemory();
+
  protected:
   // PagedSpaces that should be included in snapshots have different, i.e.,
   // smaller, initial pages.
@@ -2744,12 +2785,6 @@ class CompactionSpace : public PagedSpace {
   CompactionSpace(Heap* heap, AllocationSpace id, Executability executable)
       : PagedSpace(heap, id, executable) {}
 
-  // Adds external memory starting at {start} of {size_in_bytes} to the space.
-  void AddExternalMemory(Address start, int size_in_bytes) {
-    IncreaseCapacity(size_in_bytes);
-    Free(start, size_in_bytes);
-  }
-
   virtual bool is_local() { return true; }
 
  protected: