/*

 * Copyright 2001-2008 Sun Microsystems, Inc.  All Rights Reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

 * CA 95054 USA or visit www.sun.com if you need additional information or

 * have any questions.

 *

 */

/*

 * A binary tree based search structure for free blocks.

 * This is currently used in the Concurrent Mark&Sweep implementation.

 */

// A TreeList is a FreeList which can be used to maintain a

// binary tree of free lists.

class TreeChunk;

class BinaryTreeDictionary;

class AscendTreeCensusClosure;

class DescendTreeCensusClosure;

class DescendTreeSearchClosure;

class TreeList: public FreeList {

  friend class TreeChunk;

  friend class BinaryTreeDictionary;

  friend class AscendTreeCensusClosure;

  friend class DescendTreeCensusClosure;

  friend class DescendTreeSearchClosure;

 protected:

  TreeList* parent() const { return _parent; }

  TreeList* left()   const { return _left;   }

  TreeList* right()  const { return _right;  }

  // Accessors for links in tree.

  void setLeft(TreeList* tl) {

    _left   = tl;

    if (tl != NULL)

      tl->setParent(this);

  }

  void setRight(TreeList* tl) {

    _right  = tl;

    if (tl != NULL)

      tl->setParent(this);

  }

  void setParent(TreeList* tl)  { _parent = tl;   }

  void clearLeft()               { _left = NULL;   }

  void clearRight()              { _right = NULL;  }

  void clearParent()             { _parent = NULL; }

  void initialize()              { clearLeft(); clearRight(), clearParent(); }

  // For constructing a TreeList from a Tree chunk or

  // address and size.

  static TreeList* as_TreeList(TreeChunk* tc);

  static TreeList* as_TreeList(HeapWord* addr, size_t size);

  // Returns the head of the free list as a pointer to a TreeChunk.

  TreeChunk* head_as_TreeChunk();

  // Returns the first available chunk in the free list as a pointer

  // to a TreeChunk.

  TreeChunk* first_available();

  // removeChunkReplaceIfNeeded() removes the given "tc" from the TreeList.

  // If "tc" is the first chunk in the list, it is also the

  // TreeList that is the node in the tree.  removeChunkReplaceIfNeeded()

  // returns the possibly replaced TreeList* for the node in

  // the tree.  It also updates the parent of the original

  // node to point to the new node.

  TreeList* removeChunkReplaceIfNeeded(TreeChunk* tc);

  // See FreeList.

  void returnChunkAtHead(TreeChunk* tc);

  void returnChunkAtTail(TreeChunk* tc);

};

// A TreeChunk is a subclass of a FreeChunk that additionally

// maintains a pointer to the free list on which it is currently

// linked.

// A TreeChunk is also used as a node in the binary tree.  This

// allows the binary tree to be maintained without any additional

// storage (the free chunks are used).  In a binary tree the first

// chunk in the free list is also the tree node.  Note that the

// TreeChunk has an embedded TreeList for this purpose.  Because

// the first chunk in the list is distinguished in this fashion

// (also is the node in the tree), it is the last chunk to be found

// on the free list for a node in the tree and is only removed if

// it is the last chunk on the free list.

class TreeChunk : public FreeChunk {

  friend class TreeList;

  TreeList* _list;

  TreeList _embedded_list;  // if non-null, this chunk is on _list

 protected:

  TreeList* embedded_list() const { return (TreeList*) &_embedded_list; }

  void set_embedded_list(TreeList* v) { _embedded_list = *v; }

 public:

  TreeList* list() { return _list; }

  void set_list(TreeList* v) { _list = v; }

  static TreeChunk* as_TreeChunk(FreeChunk* fc);

  // Initialize fields in a TreeChunk that should be

  // initialized when the TreeChunk is being added to

  // a free list in the tree.

  void initialize() { embedded_list()->initialize(); }

  // debugging

  void verifyTreeChunkList() const;

};

const size_t MIN_TREE_CHUNK_SIZE  = sizeof(TreeChunk)/HeapWordSize;

class BinaryTreeDictionary: public FreeBlockDictionary {

  friend class VMStructs;

  bool       _splay;

  size_t     _totalSize;

  size_t     _totalFreeBlocks;

  TreeList* _root;

  // private accessors

  bool splay() const { return _splay; }

  void set_splay(bool v) { _splay = v; }

  size_t totalSize() const { return _totalSize; }

  void set_totalSize(size_t v) { _totalSize = v; }

  virtual void inc_totalSize(size_t v);

  virtual void dec_totalSize(size_t v);

  size_t totalFreeBlocks() const { return _totalFreeBlocks; }

  void set_totalFreeBlocks(size_t v) { _totalFreeBlocks = v; }

  TreeList* root() const { return _root; }

  void set_root(TreeList* v) { _root = v; }

  // Remove a chunk of size "size" or larger from the tree and

  // return it.  If the chunk

  // is the last chunk of that size, remove the node for that size

  // from the tree.

  TreeChunk* getChunkFromTree(size_t size, Dither dither, bool splay);

  // Return a list of the specified size or NULL from the tree.

  // The list is not removed from the tree.

  TreeList* findList (size_t size) const;

  // Remove this chunk from the tree.  If the removal results

  // in an empty list in the tree, remove the empty list.

  TreeChunk* removeChunkFromTree(TreeChunk* tc);

  // Remove the node in the trees starting at tl that has the

  // minimum value and return it.  Repair the tree as needed.

  TreeList* removeTreeMinimum(TreeList* tl);

  void       semiSplayStep(TreeList* tl);

  // Add this free chunk to the tree.

  void       insertChunkInTree(FreeChunk* freeChunk);

 public:

  void       verifyTree() const;

  // verify that the given chunk is in the tree.

  bool       verifyChunkInFreeLists(FreeChunk* tc) const;

 private:

  void          verifyTreeHelper(TreeList* tl) const;

  static size_t verifyPrevFreePtrs(TreeList* tl);

  // Returns the total number of chunks in the list.

  size_t     totalListLength(TreeList* tl) const;

  // Returns the total number of words in the chunks in the tree

  // starting at "tl".

  size_t     totalSizeInTree(TreeList* tl) const;

  // Returns the sum of the square of the size of each block

  // in the tree starting at "tl".

  double     sum_of_squared_block_sizes(TreeList* const tl) const;

  // Returns the total number of free blocks in the tree starting

  // at "tl".

  size_t     totalFreeBlocksInTree(TreeList* tl) const;

  size_t     numFreeBlocks() const;

  size_t     treeHeight() const;

  size_t     treeHeightHelper(TreeList* tl) const;

  size_t     totalNodesInTree(TreeList* tl) const;

  size_t     totalNodesHelper(TreeList* tl) const;

 public:

  // Constructor

  BinaryTreeDictionary(MemRegion mr, bool splay = false);

  // Reset the dictionary to the initial conditions with

  // a single free chunk.

  void       reset(MemRegion mr);

  void       reset(HeapWord* addr, size_t size);

  // Reset the dictionary to be empty.

  void       reset();

  // Return a chunk of size "size" or greater from

  // the tree.

  // want a better dynamic splay strategy for the future.

  FreeChunk* getChunk(size_t size, Dither dither) {

    verify_par_locked();

    FreeChunk* res = getChunkFromTree(size, dither, splay());

    assert(res == NULL || res->isFree(),

           "Should be returning a free chunk");

    return res;

  }

  void returnChunk(FreeChunk* chunk) {

    verify_par_locked();

    insertChunkInTree(chunk);

  }

  void removeChunk(FreeChunk* chunk) {

    verify_par_locked();

    removeChunkFromTree((TreeChunk*)chunk);

    assert(chunk->isFree(), "Should still be a free chunk");

  }

  size_t     maxChunkSize() const;

  size_t     totalChunkSize(debug_only(const Mutex* lock)) const {

    debug_only(

      if (lock != NULL && lock->owned_by_self()) {

        assert(totalSizeInTree(root()) == totalSize(),

               "_totalSize inconsistency");

      }

    )

    return totalSize();

  }

  size_t     minSize() const {

    return MIN_TREE_CHUNK_SIZE;

  }

  double     sum_of_squared_block_sizes() const {

    return sum_of_squared_block_sizes(root());

  }

  FreeChunk* find_chunk_ends_at(HeapWord* target) const;

  // Find the list with size "size" in the binary tree and update

  // the statistics in the list according to "split" (chunk was

  // split or coalesce) and "birth" (chunk was added or removed).

  void       dictCensusUpdate(size_t size, bool split, bool birth);

  // Return true if the dictionary is overpopulated (more chunks of

  // this size than desired) for size "size".

  bool       coalDictOverPopulated(size_t size);

  // Methods called at the beginning of a sweep to prepare the

  // statistics for the sweep.

  void       beginSweepDictCensus(double coalSurplusPercent,

  // Methods called after the end of a sweep to modify the

  // statistics for the sweep.

  void       endSweepDictCensus(double splitSurplusPercent);

  // Return the largest free chunk in the tree.

  FreeChunk* findLargestDict() const;

  // Accessors for statistics

  void       setTreeSurplus(double splitSurplusPercent);

  void       setTreeHints(void);

  // Reset statistics for all the lists in the tree.

  void       clearTreeCensus(void);

  // Print the statistcis for all the lists in the tree.  Also may

  // print out summaries.

  void       printDictCensus(void) const;

  // For debugging.  Returns the sum of the _returnedBytes for

  // all lists in the tree.

  size_t     sumDictReturnedBytes()     PRODUCT_RETURN0;

  // Sets the _returnedBytes for all the lists in the tree to zero.

  void       initializeDictReturnedBytes()      PRODUCT_RETURN;

  // For debugging.  Return the total number of chunks in the dictionary.

  size_t     totalCount()       PRODUCT_RETURN0;

  void       reportStatistics() const;

  void       verify() const;

};