[heap] Add page evacuation mode for new->new

src/heap/spaces.h

 // Copyright 2011 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.
 
 #ifndef V8_HEAP_SPACES_H_
 #define V8_HEAP_SPACES_H_
 
 #include <list>
 
 #include "src/allocation.h"
@@ skipping 407 matching lines @@
     // Large objects can have a progress bar in their page header. These object
     // are scanned in increments and will be kept black while being scanned.
     // Even if the mutator writes to them they will be kept black and a white
     // to grey transition is performed in the value.
     HAS_PROGRESS_BAR,
 
     // |PAGE_NEW_OLD_PROMOTION|: A page tagged with this flag has been promoted
     // from new to old space during evacuation.
     PAGE_NEW_OLD_PROMOTION,
 
+    // |PAGE_NEW_NEW_PROMOTION|: A page tagged with this flag has been moved
+    // within the new space during evacuation.
+    PAGE_NEW_NEW_PROMOTION,
+
     // A black page has all mark bits set to 1 (black). A black page currently
     // cannot be iterated because it is not swept. Moreover live bytes are also
     // not updated.
     BLACK_PAGE,
 
     // This flag is intended to be used for testing. Works only when both
     // FLAG_stress_compaction and FLAG_manual_evacuation_candidates_selection
     // are set. It forces the page to become an evacuation candidate at next
     // candidates selection cycle.
     FORCE_EVACUATION_CANDIDATE_FOR_TESTING,
@@ skipping 1986 matching lines @@
 
   // Grow the semispace to the new capacity.  The new capacity requested must
   // be larger than the current capacity and less than the maximum capacity.
   bool GrowTo(int new_capacity);
 
   // Shrinks the semispace to the new capacity.  The new capacity requested
   // must be more than the amount of used memory in the semispace and less
   // than the current capacity.
   bool ShrinkTo(int new_capacity);
 
+  bool EnsureCurrentCapacity();
+
   // Returns the start address of the first page of the space.
   Address space_start() {
     DCHECK_NE(anchor_.next_page(), anchor());
     return anchor_.next_page()->area_start();
   }
 
   Page* first_page() { return anchor_.next_page(); }
   Page* current_page() { return current_page_; }
 
   // Returns one past the end address of the space.
   Address space_end() { return anchor_.prev_page()->area_end(); }
 
   // Returns the start address of the current page of the space.
   Address page_low() { return current_page_->area_start(); }
 
   // Returns one past the end address of the current page of the space.
   Address page_high() { return current_page_->area_end(); }
 
   bool AdvancePage() {
     Page* next_page = current_page_->next_page();
     if (next_page == anchor()) return false;
     current_page_ = next_page;
     return true;
   }
 
   // Resets the space to using the first page.
   void Reset();
 
-  bool ReplaceWithEmptyPage(Page* page);
+  void RemovePage(Page* page);
+  void PrependPage(Page* page);
 
   // Age mark accessors.
   Address age_mark() { return age_mark_; }
   void set_age_mark(Address mark);
 
   // Returns the current capacity of the semispace.
   int current_capacity() { return current_capacity_; }
 
   // Returns the maximum capacity of the semispace.
   int maximum_capacity() { return maximum_capacity_; }
@@ skipping 55 matching lines @@
 
   // Used to govern object promotion during mark-compact collection.
   Address age_mark_;
 
   bool committed_;
   SemiSpaceId id_;
 
   Page anchor_;
   Page* current_page_;
 
+  friend class NewSpace;
+  friend class NewSpacePageIterator;
   friend class SemiSpaceIterator;
-  friend class NewSpacePageIterator;
 };
 
 
 // A SemiSpaceIterator is an ObjectIterator that iterates over the active
 // semispace of the heap's new space.  It iterates over the objects in the
 // semispace from a given start address (defaulting to the bottom of the
 // semispace) to the top of the semispace.  New objects allocated after the
 // iterator is created are not iterated.
 class SemiSpaceIterator : public ObjectIterator {
  public:
@@ skipping 158 matching lines @@
     while (current_page != last_page) {
       allocated += Page::kAllocatableMemory;
       current_page = current_page->next_page();
     }
     allocated += top() - current_page->area_start();
     DCHECK_LE(0, allocated);
     DCHECK_LE(allocated, Size());
     return static_cast<size_t>(allocated);
   }
 
-  bool ReplaceWithEmptyPage(Page* page) {
-    // This method is called after flipping the semispace.
+  void MovePageFromSpaceToSpace(Page* page) {
     DCHECK(page->InFromSpace());
-    return from_space_.ReplaceWithEmptyPage(page);
+    from_space_.RemovePage(page);
+    to_space_.PrependPage(page);
+    pages_used_++;
   }
 
+  bool Rebalance();
+
   // Return the maximum capacity of a semispace.
   int MaximumCapacity() {
     DCHECK(to_space_.maximum_capacity() == from_space_.maximum_capacity());
     return to_space_.maximum_capacity();
   }
 
   bool IsAtMaximumCapacity() { return TotalCapacity() == MaximumCapacity(); }
 
   // Returns the initial capacity of a semispace.
   int InitialTotalCapacity() {
@@ skipping 414 matching lines @@
     count = 0;
   }
   // Must be small, since an iteration is used for lookup.
   static const int kMaxComments = 64;
 };
 #endif
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_SPACES_H_