Use worst-fit allocation in old space for prentured objects.

src/spaces.h

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1508 matching lines @@
 
   // Clear the free list.
   void Reset();
 
   // Return the number of bytes available on the free list.
   intptr_t available() {
     return small_list_.available() + medium_list_.available() +
            large_list_.available() + huge_list_.available();
   }
 
+  enum AllocationStrategy {
+    BEST_FIT,
+    WORST_FIT
+  };
+
   // Place a node on the free list.  The block of size 'size_in_bytes'
   // starting at 'start' is placed on the free list.  The return value is the
   // number of bytes that have been lost due to internal fragmentation by
   // freeing the block.  Bookkeeping information will be written to the block,
   // i.e., its contents will be destroyed.  The start address should be word
   // aligned, and the size should be a non-zero multiple of the word size.
   int Free(Address start, int size_in_bytes);
 
   // Allocate a block of size 'size_in_bytes' from the free list.  The block
   // is unitialized.  A failure is returned if no block is available.  The
   // number of bytes lost to fragmentation is returned in the output parameter
   // 'wasted_bytes'.  The size should be a non-zero multiple of the word size.
+  template<AllocationStrategy strategy>
   MUST_USE_RESULT HeapObject* Allocate(int size_in_bytes);
 
 #ifdef DEBUG
   void Zap();
   intptr_t SumFreeLists();
   bool IsVeryLong();
 #endif
 
   // Used after booting the VM.
   void RepairLists(Heap* heap);
 
   intptr_t EvictFreeListItems(Page* p);
 
   FreeListCategory* small_list() { return &small_list_; }
   FreeListCategory* medium_list() { return &medium_list_; }
   FreeListCategory* large_list() { return &large_list_; }
   FreeListCategory* huge_list() { return &huge_list_; }
 
  private:
   // The size range of blocks, in bytes.
   static const int kMinBlockSize = 3 * kPointerSize;
   static const int kMaxBlockSize = Page::kMaxNonCodeHeapObjectSize;
 
-  FreeListNode* FindNodeFor(int size_in_bytes, int* node_size);
+  FreeListNode* FindNodeInHugeList(int size_in_bytes, int* node_size);
+
+  // Finds a node in the free-list using the best-fit allocation strategy.
+  FreeListNode* FindNodeForBestFit(int size_in_bytes, int* node_size);
+
+  // Finds a node in the free-list using the worst-fit allocation strategy
+  // and it ignores the smalles category.

[Michael Starzinger, 2013/04/16 13:29:27]

nit: s/smalles/smallest/

[Hannes Payer (out of office), 2013/04/16 13:41:04]

Done.

+  FreeListNode* FindNodeForWorstFit(int size_in_bytes, int* node_size);
 
   PagedSpace* owner_;
   Heap* heap_;
 
   static const int kSmallListMin = 0x20 * kPointerSize;
   static const int kSmallListMax = 0xff * kPointerSize;
   static const int kMediumListMax = 0x7ff * kPointerSize;
   static const int kLargeListMax = 0x3fff * kPointerSize;
   static const int kSmallAllocationMax = kSmallListMin - kPointerSize;
   static const int kMediumAllocationMax = kSmallListMax;
@@ skipping 110 matching lines @@
   // Returns the allocation pointer in this space.
   Address top() { return allocation_info_.top; }
   Address limit() { return allocation_info_.limit; }
 
   // The allocation top and limit addresses.
   Address* allocation_top_address() { return &allocation_info_.top; }
   Address* allocation_limit_address() { return &allocation_info_.limit; }
 
   // Allocate the requested number of bytes in the space if possible, return a
   // failure object if not.
+  template<FreeList::AllocationStrategy strategy>
   MUST_USE_RESULT inline MaybeObject* AllocateRaw(int size_in_bytes);
 
   virtual bool ReserveSpace(int bytes);
 
   // Give a block of memory to the space's free list.  It might be added to
   // the free list or accounted as waste.
   // If add_to_freelist is false then just accounting stats are updated and
   // no attempt to add area to free list is made.
   int Free(Address start, int size_in_bytes) {
     int wasted = free_list_.Free(start, size_in_bytes);
@@ skipping 157 matching lines @@
   // Expands the space by allocating a fixed number of pages. Returns false if
   // it cannot allocate requested number of pages from OS, or if the hard heap
   // size limit has been hit.
   bool Expand();
 
   // Generic fast case allocation function that tries linear allocation at the
   // address denoted by top in allocation_info_.
   inline HeapObject* AllocateLinearly(int size_in_bytes);
 
   // Slow path of AllocateRaw.  This function is space-dependent.
-  MUST_USE_RESULT virtual HeapObject* SlowAllocateRaw(int size_in_bytes);
+  template<FreeList::AllocationStrategy strategy>
+  MUST_USE_RESULT HeapObject* SlowAllocateRaw(int size_in_bytes);
 
   friend class PageIterator;
   friend class SweeperThread;
 };
 
 
 class NumberAndSizeInfo BASE_EMBEDDED {
  public:
   NumberAndSizeInfo() : number_(0), bytes_(0) {}
 
@@ skipping 962 matching lines @@
   }
   // Must be small, since an iteration is used for lookup.
   static const int kMaxComments = 64;
 };
 #endif
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_SPACES_H_