Reland "[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 1963 matching lines @@
 
   SemiSpace(Heap* heap, SemiSpaceId semispace)
       : Space(heap, NEW_SPACE, NOT_EXECUTABLE),
         current_capacity_(0),
         maximum_capacity_(0),
         minimum_capacity_(0),
         age_mark_(nullptr),
         committed_(false),
         id_(semispace),
         anchor_(this),
-        current_page_(nullptr) {}
+        current_page_(nullptr),
+        pages_used_(0) {}
 
   inline bool Contains(HeapObject* o);
   inline bool Contains(Object* o);
   inline bool ContainsSlow(Address a);
 
   void SetUp(int initial_capacity, int maximum_capacity);
   void TearDown();
   bool HasBeenSetUp() { return maximum_capacity_ != 0; }
 
   bool Commit();
   bool Uncommit();
   bool is_committed() { return committed_; }
 
   // 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_; }
+  int pages_used() { return pages_used_; }
 
   // 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;
+    if (next_page == anchor() || (pages_used_ == max_pages())) {

[ulan, 2016/06/17 13:59:48]

nit: no need for braces in (pages_used_ == max_pages())

[Michael Lippautz, 2016/06/17 14:32:02]

Done.

+      return false;
+    }
     current_page_ = next_page;
+    pages_used_++;
     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 33 matching lines @@
 #endif
 
 #ifdef VERIFY_HEAP
   virtual void Verify();
 #endif
 
  private:
   void RewindPages(Page* start, int num_pages);
 
   inline Page* anchor() { return &anchor_; }
+  inline int max_pages() { return current_capacity_ / Page::kPageSize; }
 
   // Copies the flags into the masked positions on all pages in the space.
   void FixPagesFlags(intptr_t flags, intptr_t flag_mask);
 
   // The currently committed space capacity.
   int current_capacity_;
 
-  // The maximum capacity that can be used by this space.
+  // The maximum capacity that can be used by this space. A space cannot grow
+  // beyond that size.
   int maximum_capacity_;
 
   // The minimum capacity for the space. A space cannot shrink below this size.
   int minimum_capacity_;
 
   // Used to govern object promotion during mark-compact collection.
   Address age_mark_;
 
   bool committed_;
   SemiSpaceId id_;
 
   Page anchor_;
   Page* current_page_;
+  int pages_used_;
 
+  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 49 matching lines @@
 // The new space consists of a contiguous pair of semispaces.  It simply
 // forwards most functions to the appropriate semispace.
 
 class NewSpace : public Space {
  public:
   explicit NewSpace(Heap* heap)
       : Space(heap, NEW_SPACE, NOT_EXECUTABLE),
         to_space_(heap, kToSpace),
         from_space_(heap, kFromSpace),
         reservation_(),
-        pages_used_(0),
         top_on_previous_step_(0),
         allocated_histogram_(nullptr),
         promoted_histogram_(nullptr) {}
 
   inline bool Contains(HeapObject* o);
   inline bool ContainsSlow(Address a);
   inline bool Contains(Object* o);
 
   bool SetUp(int initial_semispace_capacity, int max_semispace_capacity);
 
@@ skipping 11 matching lines @@
 
   // Grow the capacity of the semispaces.  Assumes that they are not at
   // their maximum capacity.
   void Grow();
 
   // Shrink the capacity of the semispaces.
   void Shrink();
 
   // Return the allocated bytes in the active semispace.
   intptr_t Size() override {
-    return pages_used_ * Page::kAllocatableMemory +
+    return to_space_.pages_used() * Page::kAllocatableMemory +
            static_cast<int>(top() - to_space_.page_low());
   }
 
   // The same, but returning an int.  We have to have the one that returns
   // intptr_t because it is inherited, but if we know we are dealing with the
   // new space, which can't get as big as the other spaces then this is useful:
   int SizeAsInt() { return static_cast<int>(Size()); }
 
   // Return the allocatable capacity of a semispace.
   intptr_t Capacity() {
@@ skipping 56 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);
   }
 
+  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 132 matching lines @@
  private:
   // Update allocation info to match the current to-space page.
   void UpdateAllocationInfo();
 
   base::Mutex mutex_;
 
   // The semispaces.
   SemiSpace to_space_;
   SemiSpace from_space_;
   base::VirtualMemory reservation_;
-  int pages_used_;
 
   // Allocation pointer and limit for normal allocation and allocation during
   // mark-compact collection.
   AllocationInfo allocation_info_;
 
   Address top_on_previous_step_;
 
   HistogramInfo* allocated_histogram_;
   HistogramInfo* promoted_histogram_;
 
@@ skipping 261 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_