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 /*

  * 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.

  *

  */

 # include "incls/_precompiled.incl"

 # include "incls/_binaryTreeDictionary.cpp.incl"

 ////////////////////////////////////////////////////////////////////////////////

 // A binary tree based search structure for free blocks.

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

 ////////////////////////////////////////////////////////////////////////////////

 TreeChunk* TreeChunk::as_TreeChunk(FreeChunk* fc) {

   // Do some assertion checking here.

   return (TreeChunk*) fc;

 }

 void TreeChunk::verifyTreeChunkList() const {

   TreeChunk* nextTC = (TreeChunk*)next();

   if (prev() != NULL) { // interior list node shouldn'r have tree fields

     guarantee(embedded_list()->parent() == NULL && embedded_list()->left() == NULL &&

               embedded_list()->right()  == NULL, "should be clear");

   }

   if (nextTC != NULL) {

     guarantee(as_TreeChunk(nextTC->prev()) == this, "broken chain");

     guarantee(nextTC->size() == size(), "wrong size");

     nextTC->verifyTreeChunkList();

   }

 }

 TreeList* TreeList::as_TreeList(TreeChunk* tc) {

   // This first free chunk in the list will be the tree list.

   assert(tc->size() >= sizeof(TreeChunk), "Chunk is too small for a TreeChunk");

   TreeList* tl = tc->embedded_list();

   tc->set_list(tl);

 #ifdef ASSERT

   tl->set_protecting_lock(NULL);

 #endif

   tl->set_hint(0);

   tl->set_size(tc->size());

   tl->link_head(tc);

   tl->link_tail(tc);

   tl->set_count(1);

   tl->init_statistics(true /* split_birth */);

   tl->setParent(NULL);

   tl->setLeft(NULL);

   tl->setRight(NULL);

   return tl;

 }

 TreeList* TreeList::as_TreeList(HeapWord* addr, size_t size) {

   TreeChunk* tc = (TreeChunk*) addr;

   assert(size >= sizeof(TreeChunk), "Chunk is too small for a TreeChunk");

   // The space in the heap will have been mangled initially but

   // is not remangled when a free chunk is returned to the free list

   // (since it is used to maintain the chunk on the free list).

   assert((ZapUnusedHeapArea &&

           SpaceMangler::is_mangled((HeapWord*) tc->size_addr()) &&

           SpaceMangler::is_mangled((HeapWord*) tc->prev_addr()) &&

           SpaceMangler::is_mangled((HeapWord*) tc->next_addr())) ||

           (tc->size() == 0 && tc->prev() == NULL && tc->next() == NULL),

     "Space should be clear or mangled");

   tc->setSize(size);

   tc->linkPrev(NULL);

   tc->linkNext(NULL);

   TreeList* tl = TreeList::as_TreeList(tc);

   return tl;

 }

 TreeList* TreeList::removeChunkReplaceIfNeeded(TreeChunk* tc) {

   TreeList* retTL = this;

   FreeChunk* list = head();

   assert(!list || list != list->next(), "Chunk on list twice");

   assert(tc != NULL, "Chunk being removed is NULL");

   assert(parent() == NULL || this == parent()->left() ||

     this == parent()->right(), "list is inconsistent");

   assert(tc->isFree(), "Header is not marked correctly");

   assert(head() == NULL || head()->prev() == NULL, "list invariant");

   assert(tail() == NULL || tail()->next() == NULL, "list invariant");

   FreeChunk* prevFC = tc->prev();

   TreeChunk* nextTC = TreeChunk::as_TreeChunk(tc->next());

   assert(list != NULL, "should have at least the target chunk");

   // Is this the first item on the list?

   if (tc == list) {

     // The "getChunk..." functions for a TreeList will not return the

     // first chunk in the list unless it is the last chunk in the list

     // because the first chunk is also acting as the tree node.

     // When coalescing happens, however, the first chunk in the a tree

     // list can be the start of a free range.  Free ranges are removed

     // from the free lists so that they are not available to be

     // allocated when the sweeper yields (giving up the free list lock)

     // to allow mutator activity.  If this chunk is the first in the

     // list and is not the last in the list, do the work to copy the

     // TreeList from the first chunk to the next chunk and update all

     // the TreeList pointers in the chunks in the list.

     if (nextTC == NULL) {

       assert(prevFC == NULL, "Not last chunk in the list");

       set_tail(NULL);

       set_head(NULL);

     } else {

       // copy embedded list.

       nextTC->set_embedded_list(tc->embedded_list());

       retTL = nextTC->embedded_list();

       // Fix the pointer to the list in each chunk in the list.

       // This can be slow for a long list.  Consider having

       // an option that does not allow the first chunk on the

       // list to be coalesced.

       for (TreeChunk* curTC = nextTC; curTC != NULL;

           curTC = TreeChunk::as_TreeChunk(curTC->next())) {

         curTC->set_list(retTL);

       }

       // Fix the parent to point to the new TreeList.

       if (retTL->parent() != NULL) {

         if (this == retTL->parent()->left()) {

           retTL->parent()->setLeft(retTL);

         } else {

           assert(this == retTL->parent()->right(), "Parent is incorrect");

           retTL->parent()->setRight(retTL);

         }

       }

       // Fix the children's parent pointers to point to the

       // new list.

       assert(right() == retTL->right(), "Should have been copied");

       if (retTL->right() != NULL) {

         retTL->right()->setParent(retTL);

       }

       assert(left() == retTL->left(), "Should have been copied");

       if (retTL->left() != NULL) {

         retTL->left()->setParent(retTL);

       }

       retTL->link_head(nextTC);

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

     }

   } else {

     if (nextTC == NULL) {

       // Removing chunk at tail of list

       link_tail(prevFC);

     }

     // Chunk is interior to the list

     prevFC->linkAfter(nextTC);

   }

   // Below this point the embeded TreeList being used for the

   // tree node may have changed. Don't use "this"

   // TreeList*.

   // chunk should still be a free chunk (bit set in _prev)

   assert(!retTL->head() || retTL->size() == retTL->head()->size(),

     "Wrong sized chunk in list");

   debug_only(

     tc->linkPrev(NULL);

     tc->linkNext(NULL);

     tc->set_list(NULL);

     bool prev_found = false;

     bool next_found = false;

     for (FreeChunk* curFC = retTL->head();

          curFC != NULL; curFC = curFC->next()) {

       assert(curFC != tc, "Chunk is still in list");

       if (curFC == prevFC) {

         prev_found = true;

       }

       if (curFC == nextTC) {

         next_found = true;

       }

     }

     assert(prevFC == NULL || prev_found, "Chunk was lost from list");

     assert(nextTC == NULL || next_found, "Chunk was lost from list");

     assert(retTL->parent() == NULL ||

            retTL == retTL->parent()->left() ||

            retTL == retTL->parent()->right(),

            "list is inconsistent");

   )

   retTL->decrement_count();

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

   assert(retTL->head() == NULL || retTL->head()->prev() == NULL,

     "list invariant");

   assert(retTL->tail() == NULL || retTL->tail()->next() == NULL,

     "list invariant");

   return retTL;

 }

 void TreeList::returnChunkAtTail(TreeChunk* chunk) {

   assert(chunk != NULL, "returning NULL chunk");

   assert(chunk->list() == this, "list should be set for chunk");

   assert(tail() != NULL, "The tree list is embedded in the first chunk");

   // which means that the list can never be empty.

   assert(!verifyChunkInFreeLists(chunk), "Double entry");

   assert(head() == NULL || head()->prev() == NULL, "list invariant");

   assert(tail() == NULL || tail()->next() == NULL, "list invariant");

   FreeChunk* fc = tail();

   fc->linkAfter(chunk);

   link_tail(chunk);

   assert(!tail() || size() == tail()->size(), "Wrong sized chunk in list");

   increment_count();

   debug_only(increment_returnedBytes_by(chunk->size()*sizeof(HeapWord));)

   assert(head() == NULL || head()->prev() == NULL, "list invariant");

   assert(tail() == NULL || tail()->next() == NULL, "list invariant");

 }

 // Add this chunk at the head of the list.  "At the head of the list"

 // is defined to be after the chunk pointer to by head().  This is

 // because the TreeList is embedded in the first TreeChunk in the

 // list.  See the definition of TreeChunk.

 void TreeList::returnChunkAtHead(TreeChunk* chunk) {

   assert(chunk->list() == this, "list should be set for chunk");

   assert(head() != NULL, "The tree list is embedded in the first chunk");

   assert(chunk != NULL, "returning NULL chunk");

   assert(!verifyChunkInFreeLists(chunk), "Double entry");

   assert(head() == NULL || head()->prev() == NULL, "list invariant");

   assert(tail() == NULL || tail()->next() == NULL, "list invariant");

   FreeChunk* fc = head()->next();

   if (fc != NULL) {

     chunk->linkAfter(fc);

   } else {

     assert(tail() == NULL, "List is inconsistent");

     link_tail(chunk);

   }

   head()->linkAfter(chunk);

   assert(!head() || size() == head()->size(), "Wrong sized chunk in list");

   increment_count();

   debug_only(increment_returnedBytes_by(chunk->size()*sizeof(HeapWord));)

   assert(head() == NULL || head()->prev() == NULL, "list invariant");

   assert(tail() == NULL || tail()->next() == NULL, "list invariant");

 }

 TreeChunk* TreeList::head_as_TreeChunk() {

   assert(head() == NULL || TreeChunk::as_TreeChunk(head())->list() == this,

     "Wrong type of chunk?");

   return TreeChunk::as_TreeChunk(head());

 }

 TreeChunk* TreeList::first_available() {

   guarantee(head() != NULL, "The head of the list cannot be NULL");

   FreeChunk* fc = head()->next();

   TreeChunk* retTC;

   if (fc == NULL) {

     retTC = head_as_TreeChunk();

   } else {

     retTC = TreeChunk::as_TreeChunk(fc);

   }

   assert(retTC->list() == this, "Wrong type of chunk.");

   return retTC;

 }

 // Returns the block with the largest heap address amongst

 // those in the list for this size; potentially slow and expensive,

 // use with caution!

 TreeChunk* TreeList::largest_address() {

   guarantee(head() != NULL, "The head of the list cannot be NULL");

   FreeChunk* fc = head()->next();

   TreeChunk* retTC;

   if (fc == NULL) {

     retTC = head_as_TreeChunk();

   } else {

     // walk down the list and return the one with the highest

     // heap address among chunks of this size.

     FreeChunk* last = fc;

     while (fc->next() != NULL) {

       if ((HeapWord*)last < (HeapWord*)fc) {

         last = fc;

       }

       fc = fc->next();

     }

     retTC = TreeChunk::as_TreeChunk(last);

   }

   assert(retTC->list() == this, "Wrong type of chunk.");

   return retTC;

 }

 BinaryTreeDictionary::BinaryTreeDictionary(MemRegion mr, bool splay):

   _splay(splay)

 {

   assert(mr.byte_size() > MIN_TREE_CHUNK_SIZE, "minimum chunk size");

   reset(mr);

   assert(root()->left() == NULL, "reset check failed");

   assert(root()->right() == NULL, "reset check failed");

   assert(root()->head()->next() == NULL, "reset check failed");

   assert(root()->head()->prev() == NULL, "reset check failed");

   assert(totalSize() == root()->size(), "reset check failed");

   assert(totalFreeBlocks() == 1, "reset check failed");

 }

 void BinaryTreeDictionary::inc_totalSize(size_t inc) {

   _totalSize = _totalSize + inc;

 }

 void BinaryTreeDictionary::dec_totalSize(size_t dec) {

   _totalSize = _totalSize - dec;

 }

 void BinaryTreeDictionary::reset(MemRegion mr) {

   assert(mr.byte_size() > MIN_TREE_CHUNK_SIZE, "minimum chunk size");

   set_root(TreeList::as_TreeList(mr.start(), mr.word_size()));

   set_totalSize(mr.word_size());

   set_totalFreeBlocks(1);

 }

 void BinaryTreeDictionary::reset(HeapWord* addr, size_t byte_size) {

   MemRegion mr(addr, heap_word_size(byte_size));

   reset(mr);

 }

 void BinaryTreeDictionary::reset() {

   set_root(NULL);

   set_totalSize(0);

   set_totalFreeBlocks(0);

 }

 // Get a free block of size at least size from tree, or NULL.

 // If a splay step is requested, the removal algorithm (only) incorporates

 // a splay step as follows:

 // . the search proceeds down the tree looking for a possible

 //   match. At the (closest) matching location, an appropriate splay step is applied

 //   (zig, zig-zig or zig-zag). A chunk of the appropriate size is then returned

 //   if available, and if it's the last chunk, the node is deleted. A deteleted

 //   node is replaced in place by its tree successor.

 TreeChunk*

 BinaryTreeDictionary::getChunkFromTree(size_t size, Dither dither, bool splay)

 {

   TreeList *curTL, *prevTL;

   TreeChunk* retTC = NULL;

   assert(size >= MIN_TREE_CHUNK_SIZE, "minimum chunk size");

   if (FLSVerifyDictionary) {

     verifyTree();

   }

   // starting at the root, work downwards trying to find match.

   // Remember the last node of size too great or too small.

   for (prevTL = curTL = root(); curTL != NULL;) {

     if (curTL->size() == size) {        // exact match

       break;

     }

     prevTL = curTL;

     if (curTL->size() < size) {        // proceed to right sub-tree

       curTL = curTL->right();

     } else {                           // proceed to left sub-tree

       assert(curTL->size() > size, "size inconsistency");

       curTL = curTL->left();

     }

   }

   if (curTL == NULL) { // couldn't find exact match

     // try and find the next larger size by walking back up the search path

     for (curTL = prevTL; curTL != NULL;) {

       if (curTL->size() >= size) break;

       else curTL = curTL->parent();

     }

     assert(curTL == NULL || curTL->count() > 0,

       "An empty list should not be in the tree");

   }

   if (curTL != NULL) {

     assert(curTL->size() >= size, "size inconsistency");

     if (UseCMSAdaptiveFreeLists) {

       // A candidate chunk has been found.  If it is already under

       // populated, get a chunk associated with the hint for this

       // chunk.

       if (curTL->surplus() <= 0) {

         /* Use the hint to find a size with a surplus, and reset the hint. */

         TreeList* hintTL = curTL;

         while (hintTL->hint() != 0) {

           assert(hintTL->hint() == 0 || hintTL->hint() > hintTL->size(),

             "hint points in the wrong direction");

           hintTL = findList(hintTL->hint());

           assert(curTL != hintTL, "Infinite loop");

           if (hintTL == NULL ||

               hintTL == curTL /* Should not happen but protect against it */ ) {

             // No useful hint.  Set the hint to NULL and go on.

             curTL->set_hint(0);

             break;

           }

           assert(hintTL->size() > size, "hint is inconsistent");

           if (hintTL->surplus() > 0) {

             // The hint led to a list that has a surplus.  Use it.

             // Set the hint for the candidate to an overpopulated

             // size.

             curTL->set_hint(hintTL->size());

             // Change the candidate.

             curTL = hintTL;

             break;

           }

           // The evm code reset the hint of the candidate as

           // at an interim point.  Why?  Seems like this leaves

           // the hint pointing to a list that didn't work.

           // curTL->set_hint(hintTL->size());

         }

       }

     }

     // don't waste time splaying if chunk's singleton

     if (splay && curTL->head()->next() != NULL) {

       semiSplayStep(curTL);

     }

     retTC = curTL->first_available();

     assert((retTC != NULL) && (curTL->count() > 0),

       "A list in the binary tree should not be NULL");

     assert(retTC->size() >= size,

       "A chunk of the wrong size was found");

     removeChunkFromTree(retTC);

     assert(retTC->isFree(), "Header is not marked correctly");

   }

   if (FLSVerifyDictionary) {

     verify();

   }

   return retTC;

 }

 TreeList* BinaryTreeDictionary::findList(size_t size) const {

   TreeList* curTL;

   for (curTL = root(); curTL != NULL;) {

     if (curTL->size() == size) {        // exact match

       break;

     }

     if (curTL->size() < size) {        // proceed to right sub-tree

       curTL = curTL->right();

     } else {                           // proceed to left sub-tree

       assert(curTL->size() > size, "size inconsistency");

       curTL = curTL->left();

     }

   }

   return curTL;

 }

 bool BinaryTreeDictionary::verifyChunkInFreeLists(FreeChunk* tc) const {

   size_t size = tc->size();

   TreeList* tl = findList(size);

   if (tl == NULL) {

     return false;

   } else {

     return tl->verifyChunkInFreeLists(tc);

   }

 }

 FreeChunk* BinaryTreeDictionary::findLargestDict() const {

   TreeList *curTL = root();

   if (curTL != NULL) {

     while(curTL->right() != NULL) curTL = curTL->right();

     return curTL->largest_address();

   } else {

     return NULL;

   }

 }

 // Remove the current chunk from the tree.  If it is not the last

 // chunk in a list on a tree node, just unlink it.

 // If it is the last chunk in the list (the next link is NULL),

 // remove the node and repair the tree.

 TreeChunk*

 BinaryTreeDictionary::removeChunkFromTree(TreeChunk* tc) {

   assert(tc != NULL, "Should not call with a NULL chunk");

   assert(tc->isFree(), "Header is not marked correctly");

   TreeList *newTL, *parentTL;

   TreeChunk* retTC;

   TreeList* tl = tc->list();

   debug_only(

     bool removing_only_chunk = false;

     if (tl == _root) {

       if ((_root->left() == NULL) && (_root->right() == NULL)) {

         if (_root->count() == 1) {

           assert(_root->head() == tc, "Should only be this one chunk");

           removing_only_chunk = true;

         }

       }

     }

   )

   assert(tl != NULL, "List should be set");

   assert(tl->parent() == NULL || tl == tl->parent()->left() ||

          tl == tl->parent()->right(), "list is inconsistent");

   bool complicatedSplice = false;

   retTC = tc;

   // Removing this chunk can have the side effect of changing the node

   // (TreeList*) in the tree.  If the node is the root, update it.

   TreeList* replacementTL = tl->removeChunkReplaceIfNeeded(tc);

   assert(tc->isFree(), "Chunk should still be free");

   assert(replacementTL->parent() == NULL ||

          replacementTL == replacementTL->parent()->left() ||

          replacementTL == replacementTL->parent()->right(),

          "list is inconsistent");

   if (tl == root()) {

     assert(replacementTL->parent() == NULL, "Incorrectly replacing root");

     set_root(replacementTL);

   }

   debug_only(

     if (tl != replacementTL) {

       assert(replacementTL->head() != NULL,

         "If the tree list was replaced, it should not be a NULL list");

       TreeList* rhl = replacementTL->head_as_TreeChunk()->list();

       TreeList* rtl = TreeChunk::as_TreeChunk(replacementTL->tail())->list();

       assert(rhl == replacementTL, "Broken head");

       assert(rtl == replacementTL, "Broken tail");

       assert(replacementTL->size() == tc->size(),  "Broken size");

     }

   )

   // Does the tree need to be repaired?

   if (replacementTL->count() == 0) {

     assert(replacementTL->head() == NULL &&

            replacementTL->tail() == NULL, "list count is incorrect");

     // Find the replacement node for the (soon to be empty) node being removed.

     // if we have a single (or no) child, splice child in our stead

     if (replacementTL->left() == NULL) {

       // left is NULL so pick right.  right may also be NULL.

       newTL = replacementTL->right();

       debug_only(replacementTL->clearRight();)

     } else if (replacementTL->right() == NULL) {

       // right is NULL

       newTL = replacementTL->left();

       debug_only(replacementTL->clearLeft();)

     } else {  // we have both children, so, by patriarchal convention,

               // my replacement is least node in right sub-tree

       complicatedSplice = true;

       newTL = removeTreeMinimum(replacementTL->right());

       assert(newTL != NULL && newTL->left() == NULL &&

              newTL->right() == NULL, "sub-tree minimum exists");

     }

     // newTL is the replacement for the (soon to be empty) node.

     // newTL may be NULL.

     // should verify; we just cleanly excised our replacement

     if (FLSVerifyDictionary) {

       verifyTree();

     }

     // first make newTL my parent's child

     if ((parentTL = replacementTL->parent()) == NULL) {

       // newTL should be root

       assert(tl == root(), "Incorrectly replacing root");

       set_root(newTL);

       if (newTL != NULL) {

         newTL->clearParent();

       }

     } else if (parentTL->right() == replacementTL) {

       // replacementTL is a right child

       parentTL->setRight(newTL);

     } else {                                // replacementTL is a left child

       assert(parentTL->left() == replacementTL, "should be left child");

       parentTL->setLeft(newTL);

     }

     debug_only(replacementTL->clearParent();)

     if (complicatedSplice) {  // we need newTL to get replacementTL's

                               // two children

       assert(newTL != NULL &&

              newTL->left() == NULL && newTL->right() == NULL,

             "newTL should not have encumbrances from the past");

       // we'd like to assert as below:

       // assert(replacementTL->left() != NULL && replacementTL->right() != NULL,

       //       "else !complicatedSplice");

       // ... however, the above assertion is too strong because we aren't

       // guaranteed that replacementTL->right() is still NULL.

       // Recall that we removed

       // the right sub-tree minimum from replacementTL.

       // That may well have been its right

       // child! So we'll just assert half of the above:

       assert(replacementTL->left() != NULL, "else !complicatedSplice");

       newTL->setLeft(replacementTL->left());

       newTL->setRight(replacementTL->right());

       debug_only(

         replacementTL->clearRight();

         replacementTL->clearLeft();

       )

     }

     assert(replacementTL->right() == NULL &&

            replacementTL->left() == NULL &&

            replacementTL->parent() == NULL,

         "delete without encumbrances");

   }

   assert(totalSize() >= retTC->size(), "Incorrect total size");

   dec_totalSize(retTC->size());     // size book-keeping

   assert(totalFreeBlocks() > 0, "Incorrect total count");

   set_totalFreeBlocks(totalFreeBlocks() - 1);

   assert(retTC != NULL, "null chunk?");

   assert(retTC->prev() == NULL && retTC->next() == NULL,

          "should return without encumbrances");

   if (FLSVerifyDictionary) {

     verifyTree();

   }

   assert(!removing_only_chunk || _root == NULL, "root should be NULL");

   return TreeChunk::as_TreeChunk(retTC);

 }

 // Remove the leftmost node (lm) in the tree and return it.

 // If lm has a right child, link it to the left node of

 // the parent of lm.

 TreeList* BinaryTreeDictionary::removeTreeMinimum(TreeList* tl) {

   assert(tl != NULL && tl->parent() != NULL, "really need a proper sub-tree");

   // locate the subtree minimum by walking down left branches

   TreeList* curTL = tl;

   for (; curTL->left() != NULL; curTL = curTL->left());

   // obviously curTL now has at most one child, a right child

   if (curTL != root()) {  // Should this test just be removed?

     TreeList* parentTL = curTL->parent();

     if (parentTL->left() == curTL) { // curTL is a left child

       parentTL->setLeft(curTL->right());

     } else {

       // If the list tl has no left child, then curTL may be

       // the right child of parentTL.

       assert(parentTL->right() == curTL, "should be a right child");

       parentTL->setRight(curTL->right());

     }

   } else {

     // The only use of this method would not pass the root of the

     // tree (as indicated by the assertion above that the tree list

     // has a parent) but the specification does not explicitly exclude the

     // passing of the root so accomodate it.

     set_root(NULL);

   }

   debug_only(

     curTL->clearParent();  // Test if this needs to be cleared

     curTL->clearRight();    // recall, above, left child is already null

   )

   // we just excised a (non-root) node, we should still verify all tree invariants

   if (FLSVerifyDictionary) {

     verifyTree();

   }

   return curTL;

 }

 // Based on a simplification of the algorithm by Sleator and Tarjan (JACM 1985).

 // The simplifications are the following:

 // . we splay only when we delete (not when we insert)

 // . we apply a single spay step per deletion/access

 // By doing such partial splaying, we reduce the amount of restructuring,

 // while getting a reasonably efficient search tree (we think).

 // [Measurements will be needed to (in)validate this expectation.]

 void BinaryTreeDictionary::semiSplayStep(TreeList* tc) {

   // apply a semi-splay step at the given node:

   // . if root, norting needs to be done

   // . if child of root, splay once

   // . else zig-zig or sig-zag depending on path from grandparent

   if (root() == tc) return;

   warning("*** Splaying not yet implemented; "

           "tree operations may be inefficient ***");

 }

 void BinaryTreeDictionary::insertChunkInTree(FreeChunk* fc) {

   TreeList *curTL, *prevTL;

   size_t size = fc->size();

   assert(size >= MIN_TREE_CHUNK_SIZE, "too small to be a TreeList");

   if (FLSVerifyDictionary) {

     verifyTree();

   }

   // XXX: do i need to clear the FreeChunk fields, let me do it just in case

   // Revisit this later

   fc->clearNext();

   fc->linkPrev(NULL);

   // work down from the _root, looking for insertion point

   for (prevTL = curTL = root(); curTL != NULL;) {

     if (curTL->size() == size)  // exact match

       break;

     prevTL = curTL;

     if (curTL->size() > size) { // follow left branch

       curTL = curTL->left();

     } else {                    // follow right branch

       assert(curTL->size() < size, "size inconsistency");

       curTL = curTL->right();

     }

   }

   TreeChunk* tc = TreeChunk::as_TreeChunk(fc);

   // This chunk is being returned to the binary tree.  Its embedded

   // TreeList should be unused at this point.

   tc->initialize();

   if (curTL != NULL) {          // exact match

     tc->set_list(curTL);

     curTL->returnChunkAtTail(tc);

   } else {                     // need a new node in tree

     tc->clearNext();

     tc->linkPrev(NULL);

     TreeList* newTL = TreeList::as_TreeList(tc);

     assert(((TreeChunk*)tc)->list() == newTL,

       "List was not initialized correctly");

     if (prevTL == NULL) {      // we are the only tree node

       assert(root() == NULL, "control point invariant");

       set_root(newTL);

     } else {                   // insert under prevTL ...

       if (prevTL->size() < size) {   // am right child

         assert(prevTL->right() == NULL, "control point invariant");

         prevTL->setRight(newTL);

       } else {                       // am left child

         assert(prevTL->size() > size && prevTL->left() == NULL, "cpt pt inv");

         prevTL->setLeft(newTL);

       }

     }

   }

   assert(tc->list() != NULL, "Tree list should be set");

   inc_totalSize(size);

   // Method 'totalSizeInTree' walks through the every block in the

   // tree, so it can cause significant performance loss if there are

   // many blocks in the tree

   assert(!FLSVerifyDictionary || totalSizeInTree(root()) == totalSize(), "_totalSize inconsistency");

   set_totalFreeBlocks(totalFreeBlocks() + 1);

   if (FLSVerifyDictionary) {

     verifyTree();

   }

 }

 size_t BinaryTreeDictionary::maxChunkSize() const {

   verify_par_locked();

   TreeList* tc = root();

   if (tc == NULL) return 0;

   for (; tc->right() != NULL; tc = tc->right());

   return tc->size();

 }

 size_t BinaryTreeDictionary::totalListLength(TreeList* tl) const {

   size_t res;

   res = tl->count();

 #ifdef ASSERT

   size_t cnt;

   FreeChunk* tc = tl->head();

   for (cnt = 0; tc != NULL; tc = tc->next(), cnt++);

   assert(res == cnt, "The count is not being maintained correctly");

 #endif

   return res;

 }

 size_t BinaryTreeDictionary::totalSizeInTree(TreeList* tl) const {

   if (tl == NULL)

     return 0;

   return (tl->size() * totalListLength(tl)) +

          totalSizeInTree(tl->left())    +

          totalSizeInTree(tl->right());

 }

 double BinaryTreeDictionary::sum_of_squared_block_sizes(TreeList* const tl) const {

   if (tl == NULL) {

     return 0.0;

   }

   double size = (double)(tl->size());

   double curr = size * size * totalListLength(tl);

   curr += sum_of_squared_block_sizes(tl->left());

   curr += sum_of_squared_block_sizes(tl->right());

   return curr;

 }

 size_t BinaryTreeDictionary::totalFreeBlocksInTree(TreeList* tl) const {

   if (tl == NULL)

     return 0;

   return totalListLength(tl) +

          totalFreeBlocksInTree(tl->left()) +

          totalFreeBlocksInTree(tl->right());

 }

 size_t BinaryTreeDictionary::numFreeBlocks() const {

   assert(totalFreeBlocksInTree(root()) == totalFreeBlocks(),

          "_totalFreeBlocks inconsistency");

   return totalFreeBlocks();

 }

 size_t BinaryTreeDictionary::treeHeightHelper(TreeList* tl) const {

   if (tl == NULL)

     return 0;

   return 1 + MAX2(treeHeightHelper(tl->left()),

                   treeHeightHelper(tl->right()));

 }

 size_t BinaryTreeDictionary::treeHeight() const {

   return treeHeightHelper(root());

 }

 size_t BinaryTreeDictionary::totalNodesHelper(TreeList* tl) const {

   if (tl == NULL) {

     return 0;

   }

   return 1 + totalNodesHelper(tl->left()) +

     totalNodesHelper(tl->right());

 }

 size_t BinaryTreeDictionary::totalNodesInTree(TreeList* tl) const {

   return totalNodesHelper(root());

 }

 void BinaryTreeDictionary::dictCensusUpdate(size_t size, bool split, bool birth){

   TreeList* nd = findList(size);

   if (nd) {

     if (split) {

       if (birth) {

         nd->increment_splitBirths();

         nd->increment_surplus();

       }  else {

         nd->increment_splitDeaths();

         nd->decrement_surplus();

       }

     } else {

       if (birth) {

         nd->increment_coalBirths();

         nd->increment_surplus();

       } else {

         nd->increment_coalDeaths();

         nd->decrement_surplus();

       }

     }

   }

   // A list for this size may not be found (nd == 0) if

   //   This is a death where the appropriate list is now

   //     empty and has been removed from the list.

   //   This is a birth associated with a LinAB.  The chunk

   //     for the LinAB is not in the dictionary.

 }

 bool BinaryTreeDictionary::coalDictOverPopulated(size_t size) {

   if (FLSAlwaysCoalesceLarge) return true;

   TreeList* list_of_size = findList(size);

   // None of requested size implies overpopulated.

   return list_of_size == NULL || list_of_size->coalDesired() <= 0 ||

          list_of_size->count() > list_of_size->coalDesired();

 }

 // Closures for walking the binary tree.

 //   do_list() walks the free list in a node applying the closure

 //     to each free chunk in the list

 //   do_tree() walks the nodes in the binary tree applying do_list()

 //     to each list at each node.

 class TreeCensusClosure : public StackObj {

  protected:

   virtual void do_list(FreeList* fl) = 0;

  public:

   virtual void do_tree(TreeList* tl) = 0;

 };

 class AscendTreeCensusClosure : public TreeCensusClosure {

  public:

   void do_tree(TreeList* tl) {

     if (tl != NULL) {

       do_tree(tl->left());

       do_list(tl);

       do_tree(tl->right());

     }

   }

 };

 class DescendTreeCensusClosure : public TreeCensusClosure {

  public:

   void do_tree(TreeList* tl) {

     if (tl != NULL) {

       do_tree(tl->right());

       do_list(tl);

       do_tree(tl->left());

     }

   }

 };

 // For each list in the tree, calculate the desired, desired

 // coalesce, count before sweep, and surplus before sweep.

 class BeginSweepClosure : public AscendTreeCensusClosure {

   double _percentage;

   float _inter_sweep_current;

   float _inter_sweep_estimate;

   float _intra_sweep_estimate;

  public:

   BeginSweepClosure(double p, float inter_sweep_current,

                               float inter_sweep_estimate,

                               float intra_sweep_estimate) :

    _percentage(p),

    _inter_sweep_current(inter_sweep_current),

    _inter_sweep_estimate(inter_sweep_estimate),

    _intra_sweep_estimate(intra_sweep_estimate) { }

   void do_list(FreeList* fl) {

     double coalSurplusPercent = _percentage;

     fl->compute_desired(_inter_sweep_current, _inter_sweep_estimate, _intra_sweep_estimate);

     fl->set_coalDesired((ssize_t)((double)fl->desired() * coalSurplusPercent));

     fl->set_beforeSweep(fl->count());

     fl->set_bfrSurp(fl->surplus());

   }

 };

 // Used to search the tree until a condition is met.

 // Similar to TreeCensusClosure but searches the

 // tree and returns promptly when found.

 class TreeSearchClosure : public StackObj {

  protected:

   virtual bool do_list(FreeList* fl) = 0;

  public:

   virtual bool do_tree(TreeList* tl) = 0;

 };

 #if 0 //  Don't need this yet but here for symmetry.

 class AscendTreeSearchClosure : public TreeSearchClosure {

  public:

   bool do_tree(TreeList* tl) {

     if (tl != NULL) {

       if (do_tree(tl->left())) return true;

       if (do_list(tl)) return true;

       if (do_tree(tl->right())) return true;

     }

     return false;

   }

 };

 #endif

 class DescendTreeSearchClosure : public TreeSearchClosure {

  public:

   bool do_tree(TreeList* tl) {

     if (tl != NULL) {

       if (do_tree(tl->right())) return true;

       if (do_list(tl)) return true;

       if (do_tree(tl->left())) return true;

     }

     return false;

   }

 };

 // Searches the tree for a chunk that ends at the

 // specified address.

 class EndTreeSearchClosure : public DescendTreeSearchClosure {

   HeapWord* _target;

   FreeChunk* _found;

  public:

   EndTreeSearchClosure(HeapWord* target) : _target(target), _found(NULL) {}

   bool do_list(FreeList* fl) {

     FreeChunk* item = fl->head();

     while (item != NULL) {

       if (item->end() == _target) {

         _found = item;

         return true;

       }

       item = item->next();

     }

     return false;

   }

   FreeChunk* found() { return _found; }

 };

 FreeChunk* BinaryTreeDictionary::find_chunk_ends_at(HeapWord* target) const {

   EndTreeSearchClosure etsc(target);

   bool found_target = etsc.do_tree(root());

   assert(found_target || etsc.found() == NULL, "Consistency check");

   assert(!found_target || etsc.found() != NULL, "Consistency check");

   return etsc.found();

 }

 void BinaryTreeDictionary::beginSweepDictCensus(double coalSurplusPercent,

   float inter_sweep_current, float inter_sweep_estimate, float intra_sweep_estimate) {

   BeginSweepClosure bsc(coalSurplusPercent, inter_sweep_current,

                                             inter_sweep_estimate,

                                             intra_sweep_estimate);

   bsc.do_tree(root());

 }

 // Closures and methods for calculating total bytes returned to the

 // free lists in the tree.

 NOT_PRODUCT(

   class InitializeDictReturnedBytesClosure : public AscendTreeCensusClosure {

    public:

     void do_list(FreeList* fl) {

       fl->set_returnedBytes(0);

     }

   };

   void BinaryTreeDictionary::initializeDictReturnedBytes() {

     InitializeDictReturnedBytesClosure idrb;

     idrb.do_tree(root());

   }

   class ReturnedBytesClosure : public AscendTreeCensusClosure {

     size_t _dictReturnedBytes;

    public:

     ReturnedBytesClosure() { _dictReturnedBytes = 0; }

     void do_list(FreeList* fl) {

       _dictReturnedBytes += fl->returnedBytes();

     }

     size_t dictReturnedBytes() { return _dictReturnedBytes; }

   };

   size_t BinaryTreeDictionary::sumDictReturnedBytes() {

     ReturnedBytesClosure rbc;

     rbc.do_tree(root());

     return rbc.dictReturnedBytes();

   }

   // Count the number of entries in the tree.

   class treeCountClosure : public DescendTreeCensusClosure {

    public:

     uint count;

     treeCountClosure(uint c) { count = c; }

     void do_list(FreeList* fl) {

       count++;

     }

   };

   size_t BinaryTreeDictionary::totalCount() {

     treeCountClosure ctc(0);

     ctc.do_tree(root());

     return ctc.count;

   }

 )

 // Calculate surpluses for the lists in the tree.

 class setTreeSurplusClosure : public AscendTreeCensusClosure {

   double percentage;

  public:

   setTreeSurplusClosure(double v) { percentage = v; }

   void do_list(FreeList* fl) {

     double splitSurplusPercent = percentage;

     fl->set_surplus(fl->count() -

                    (ssize_t)((double)fl->desired() * splitSurplusPercent));

   }

 };

 void BinaryTreeDictionary::setTreeSurplus(double splitSurplusPercent) {

   setTreeSurplusClosure sts(splitSurplusPercent);

   sts.do_tree(root());

 }

 // Set hints for the lists in the tree.

 class setTreeHintsClosure : public DescendTreeCensusClosure {

   size_t hint;

  public:

   setTreeHintsClosure(size_t v) { hint = v; }

   void do_list(FreeList* fl) {

     fl->set_hint(hint);

     assert(fl->hint() == 0 || fl->hint() > fl->size(),

       "Current hint is inconsistent");

     if (fl->surplus() > 0) {

       hint = fl->size();

     }

   }

 };

 void BinaryTreeDictionary::setTreeHints(void) {

   setTreeHintsClosure sth(0);

   sth.do_tree(root());

 }

 // Save count before previous sweep and splits and coalesces.

 class clearTreeCensusClosure : public AscendTreeCensusClosure {

   void do_list(FreeList* fl) {

     fl->set_prevSweep(fl->count());

     fl->set_coalBirths(0);

     fl->set_coalDeaths(0);

     fl->set_splitBirths(0);

     fl->set_splitDeaths(0);

   }

 };

 void BinaryTreeDictionary::clearTreeCensus(void) {

   clearTreeCensusClosure ctc;

   ctc.do_tree(root());

 }

 // Do reporting and post sweep clean up.

 void BinaryTreeDictionary::endSweepDictCensus(double splitSurplusPercent) {

   // Does walking the tree 3 times hurt?

   setTreeSurplus(splitSurplusPercent);

   setTreeHints();

   if (PrintGC && Verbose) {

     reportStatistics();

   }

   clearTreeCensus();

 }

 // Print summary statistics

 void BinaryTreeDictionary::reportStatistics() const {

   verify_par_locked();

   gclog_or_tty->print("Statistics for BinaryTreeDictionary:\n"

          "------------------------------------\n");

   size_t totalSize = totalChunkSize(debug_only(NULL));

   size_t    freeBlocks = numFreeBlocks();

   gclog_or_tty->print("Total Free Space: %d\n", totalSize);

   gclog_or_tty->print("Max   Chunk Size: %d\n", maxChunkSize());

   gclog_or_tty->print("Number of Blocks: %d\n", freeBlocks);

   if (freeBlocks > 0) {

     gclog_or_tty->print("Av.  Block  Size: %d\n", totalSize/freeBlocks);

   }

   gclog_or_tty->print("Tree      Height: %d\n", treeHeight());

 }

 // Print census information - counts, births, deaths, etc.

 // for each list in the tree.  Also print some summary

 // information.

 class PrintTreeCensusClosure : public AscendTreeCensusClosure {

   int _print_line;

   size_t _totalFree;

   FreeList _total;

  public:

   PrintTreeCensusClosure() {

     _print_line = 0;

     _totalFree = 0;

   }

   FreeList* total() { return &_total; }

   size_t totalFree() { return _totalFree; }

   void do_list(FreeList* fl) {

     if (++_print_line >= 40) {

       FreeList::print_labels_on(gclog_or_tty, "size");

       _print_line = 0;

     }

     fl->print_on(gclog_or_tty);

     _totalFree +=            fl->count()            * fl->size()        ;

     total()->set_count(      total()->count()       + fl->count()      );

     total()->set_bfrSurp(    total()->bfrSurp()     + fl->bfrSurp()    );

     total()->set_surplus(    total()->splitDeaths() + fl->surplus()    );

     total()->set_desired(    total()->desired()     + fl->desired()    );

     total()->set_prevSweep(  total()->prevSweep()   + fl->prevSweep()  );

     total()->set_beforeSweep(total()->beforeSweep() + fl->beforeSweep());

     total()->set_coalBirths( total()->coalBirths()  + fl->coalBirths() );

     total()->set_coalDeaths( total()->coalDeaths()  + fl->coalDeaths() );

     total()->set_splitBirths(total()->splitBirths() + fl->splitBirths());

     total()->set_splitDeaths(total()->splitDeaths() + fl->splitDeaths());

   }

 };

 void BinaryTreeDictionary::printDictCensus(void) const {

   gclog_or_tty->print("\nBinaryTree\n");

   FreeList::print_labels_on(gclog_or_tty, "size");

   PrintTreeCensusClosure ptc;

   ptc.do_tree(root());

   FreeList* total = ptc.total();

   FreeList::print_labels_on(gclog_or_tty, " ");

   total->print_on(gclog_or_tty, "TOTAL\t");

   gclog_or_tty->print(

               "totalFree(words): " SIZE_FORMAT_W(16)

               " growth: %8.5f  deficit: %8.5f\n",

               ptc.totalFree(),

               (double)(total->splitBirths() + total->coalBirths()

                      - total->splitDeaths() - total->coalDeaths())

               /(total->prevSweep() != 0 ? (double)total->prevSweep() : 1.0),

              (double)(total->desired() - total->count())

              /(total->desired() != 0 ? (double)total->desired() : 1.0));

 }

 class PrintFreeListsClosure : public AscendTreeCensusClosure {

   outputStream* _st;

   int _print_line;

  public:

   PrintFreeListsClosure(outputStream* st) {

     _st = st;

     _print_line = 0;

   }

   void do_list(FreeList* fl) {

     if (++_print_line >= 40) {

       FreeList::print_labels_on(_st, "size");

       _print_line = 0;

     }

     fl->print_on(gclog_or_tty);

     size_t sz = fl->size();

     for (FreeChunk* fc = fl->head(); fc != NULL;

          fc = fc->next()) {

       _st->print_cr("\t[" PTR_FORMAT "," PTR_FORMAT ")  %s",

                     fc, (HeapWord*)fc + sz,

                     fc->cantCoalesce() ? "\t CC" : "");

     }

   }

 };

 void BinaryTreeDictionary::print_free_lists(outputStream* st) const {

   FreeList::print_labels_on(st, "size");

   PrintFreeListsClosure pflc(st);

   pflc.do_tree(root());

 }

 // Verify the following tree invariants:

 // . _root has no parent

 // . parent and child point to each other

 // . each node's key correctly related to that of its child(ren)

 void BinaryTreeDictionary::verifyTree() const {

   guarantee(root() == NULL || totalFreeBlocks() == 0 ||

     totalSize() != 0, "_totalSize should't be 0?");

   guarantee(root() == NULL || root()->parent() == NULL, "_root shouldn't have parent");

   verifyTreeHelper(root());

 }

 size_t BinaryTreeDictionary::verifyPrevFreePtrs(TreeList* tl) {

   size_t ct = 0;

   for (FreeChunk* curFC = tl->head(); curFC != NULL; curFC = curFC->next()) {

     ct++;

     assert(curFC->prev() == NULL || curFC->prev()->isFree(),

       "Chunk should be free");

   }

   return ct;

 }

 // Note: this helper is recursive rather than iterative, so use with

 // caution on very deep trees; and watch out for stack overflow errors;

 // In general, to be used only for debugging.

 void BinaryTreeDictionary::verifyTreeHelper(TreeList* tl) const {

   if (tl == NULL)

     return;

   guarantee(tl->size() != 0, "A list must has a size");

   guarantee(tl->left()  == NULL || tl->left()->parent()  == tl,

          "parent<-/->left");

   guarantee(tl->right() == NULL || tl->right()->parent() == tl,

          "parent<-/->right");;

   guarantee(tl->left() == NULL  || tl->left()->size()    <  tl->size(),

          "parent !> left");

   guarantee(tl->right() == NULL || tl->right()->size()   >  tl->size(),

          "parent !< left");

   guarantee(tl->head() == NULL || tl->head()->isFree(), "!Free");

   guarantee(tl->head() == NULL || tl->head_as_TreeChunk()->list() == tl,

     "list inconsistency");

   guarantee(tl->count() > 0 || (tl->head() == NULL && tl->tail() == NULL),

     "list count is inconsistent");

   guarantee(tl->count() > 1 || tl->head() == tl->tail(),

     "list is incorrectly constructed");

   size_t count = verifyPrevFreePtrs(tl);

   guarantee(count == (size_t)tl->count(), "Node count is incorrect");

   if (tl->head() != NULL) {

     tl->head_as_TreeChunk()->verifyTreeChunkList();

   }

   verifyTreeHelper(tl->left());

   verifyTreeHelper(tl->right());

 }

 void BinaryTreeDictionary::verify() const {

   verifyTree();

   guarantee(totalSize() == totalSizeInTree(root()), "Total Size inconsistency");

 }