[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_PROMITION|: A page tagged with this flag has been moved

[ulan, 2016/06/14 15:38:51]

typo PAGE_NEW_NEW_PROMOTION

[Michael Lippautz, 2016/06/15 06:49:30]

Done.

+    // 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 1995 matching lines @@
 
   // 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_; }
 
+  bool OnLastPage() { return current_page() == anchor()->prev_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() {
@@ skipping 75 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 164 matching lines @@
     DCHECK_LE(allocated, Size());
     return static_cast<size_t>(allocated);
   }
 
   bool ReplaceWithEmptyPage(Page* page) {
     // This method is called after flipping the semispace.
     DCHECK(page->InFromSpace());
     return from_space_.ReplaceWithEmptyPage(page);
   }
 
+  // Swaps the given |from_space_page| with a proper page in *to* space. The
+  // method should only be called during evacuation.
+  void SwapFromSpacePageWithToSpacePage(Page* from_space_page);
+
+  // Swaps |from_space_page| with |to_space_page| by swapping their interiors
+  // and inserting them at |from_target| and |to_target| respectively. Note
+  // that this implies that |from_target| is in *to* space and vice versa.
+  void SwapPages(Page* from_space_page, Page* to_space_page, Page* from_target,
+                 Page* to_target);
+
   // 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_