1 /*
   2  * Copyright 2001-2006 Sun Microsystems, Inc.  All Rights Reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
  20  * CA 95054 USA or visit www.sun.com if you need additional information or
  21  * have any questions.
  22  *
  23  */
  24 
  25 # include "incls/_precompiled.incl"
  26 # include "incls/_binaryTreeDictionary.cpp.incl"
  27 
  28 ////////////////////////////////////////////////////////////////////////////////
  29 // A binary tree based search structure for free blocks.
  30 // This is currently used in the Concurrent Mark&Sweep implementation.
  31 ////////////////////////////////////////////////////////////////////////////////
  32 
  33 TreeChunk* TreeChunk::as_TreeChunk(FreeChunk* fc) {
  34   // Do some assertion checking here.
  35   return (TreeChunk*) fc;
  36 }
  37 
  38 void TreeChunk::verifyTreeChunkList() const {
  39   TreeChunk* nextTC = (TreeChunk*)next();
  40   if (prev() != NULL) { // interior list node shouldn'r have tree fields
  41     guarantee(embedded_list()->parent() == NULL && embedded_list()->left() == NULL &&
  42               embedded_list()->right()  == NULL, "should be clear");
  43   }
  44   if (nextTC != NULL) {
  45     guarantee(as_TreeChunk(nextTC->prev()) == this, "broken chain");
  46     guarantee(nextTC->size() == size(), "wrong size");
  47     nextTC->verifyTreeChunkList();
  48   }
  49 }
  50 
  51 
  52 TreeList* TreeList::as_TreeList(TreeChunk* tc) {
  53   // This first free chunk in the list will be the tree list.
  54   assert(tc->size() >= sizeof(TreeChunk), "Chunk is too small for a TreeChunk");
  55   TreeList* tl = tc->embedded_list();
  56   tc->set_list(tl);
  57 #ifdef ASSERT
  58   tl->set_protecting_lock(NULL);
  59 #endif
  60   tl->set_hint(0);
  61   tl->set_size(tc->size());
  62   tl->link_head(tc);
  63   tl->link_tail(tc);
  64   tl->set_count(1);
  65   tl->init_statistics();
  66   tl->setParent(NULL);
  67   tl->setLeft(NULL);
  68   tl->setRight(NULL);
  69   return tl;
  70 }
  71 TreeList* TreeList::as_TreeList(HeapWord* addr, size_t size) {
  72   TreeChunk* tc = (TreeChunk*) addr;
  73   assert(size >= sizeof(TreeChunk), "Chunk is too small for a TreeChunk");
  74   assert(tc->size() == 0 && tc->prev() == NULL && tc->next() == NULL,
  75     "Space should be clear");
  76   tc->setSize(size);
  77   tc->linkPrev(NULL);
  78   tc->linkNext(NULL);
  79   TreeList* tl = TreeList::as_TreeList(tc);
  80   return tl;
  81 }
  82 
  83 TreeList* TreeList::removeChunkReplaceIfNeeded(TreeChunk* tc) {
  84 
  85   TreeList* retTL = this;
  86   FreeChunk* list = head();
  87   assert(!list || list != list->next(), "Chunk on list twice");
  88   assert(tc != NULL, "Chunk being removed is NULL");
  89   assert(parent() == NULL || this == parent()->left() ||
  90     this == parent()->right(), "list is inconsistent");
  91   assert(tc->isFree(), "Header is not marked correctly");
  92   assert(head() == NULL || head()->prev() == NULL, "list invariant");
  93   assert(tail() == NULL || tail()->next() == NULL, "list invariant");
  94 
  95   FreeChunk* prevFC = tc->prev();
  96   TreeChunk* nextTC = TreeChunk::as_TreeChunk(tc->next());
  97   assert(list != NULL, "should have at least the target chunk");
  98 
  99   // Is this the first item on the list?
 100   if (tc == list) {
 101     // The "getChunk..." functions for a TreeList will not return the
 102     // first chunk in the list unless it is the last chunk in the list
 103     // because the first chunk is also acting as the tree node.
 104     // When coalescing happens, however, the first chunk in the a tree
 105     // list can be the start of a free range.  Free ranges are removed
 106     // from the free lists so that they are not available to be
 107     // allocated when the sweeper yields (giving up the free list lock)
 108     // to allow mutator activity.  If this chunk is the first in the
 109     // list and is not the last in the list, do the work to copy the
 110     // TreeList from the first chunk to the next chunk and update all
 111     // the TreeList pointers in the chunks in the list.
 112     if (nextTC == NULL) {
 113       assert(prevFC == NULL, "Not last chunk in the list")
 114       set_tail(NULL);
 115       set_head(NULL);
 116     } else {
 117       // copy embedded list.
 118       nextTC->set_embedded_list(tc->embedded_list());
 119       retTL = nextTC->embedded_list();
 120       // Fix the pointer to the list in each chunk in the list.
 121       // This can be slow for a long list.  Consider having
 122       // an option that does not allow the first chunk on the
 123       // list to be coalesced.
 124       for (TreeChunk* curTC = nextTC; curTC != NULL;
 125           curTC = TreeChunk::as_TreeChunk(curTC->next())) {
 126         curTC->set_list(retTL);
 127       }
 128       // Fix the parent to point to the new TreeList.
 129       if (retTL->parent() != NULL) {
 130         if (this == retTL->parent()->left()) {
 131           retTL->parent()->setLeft(retTL);
 132         } else {
 133           assert(this == retTL->parent()->right(), "Parent is incorrect");
 134           retTL->parent()->setRight(retTL);
 135         }
 136       }
 137       // Fix the children's parent pointers to point to the
 138       // new list.
 139       assert(right() == retTL->right(), "Should have been copied");
 140       if (retTL->right() != NULL) {
 141         retTL->right()->setParent(retTL);
 142       }
 143       assert(left() == retTL->left(), "Should have been copied");
 144       if (retTL->left() != NULL) {
 145         retTL->left()->setParent(retTL);
 146       }
 147       retTL->link_head(nextTC);
 148       assert(nextTC->isFree(), "Should be a free chunk");
 149     }
 150   } else {
 151     if (nextTC == NULL) {
 152       // Removing chunk at tail of list
 153       link_tail(prevFC);
 154     }
 155     // Chunk is interior to the list
 156     prevFC->linkAfter(nextTC);
 157   }
 158 
 159   // Below this point the embeded TreeList being used for the
 160   // tree node may have changed. Don't use "this"
 161   // TreeList*.
 162   // chunk should still be a free chunk (bit set in _prev)
 163   assert(!retTL->head() || retTL->size() == retTL->head()->size(),
 164     "Wrong sized chunk in list");
 165   debug_only(
 166     tc->linkPrev(NULL);
 167     tc->linkNext(NULL);
 168     tc->set_list(NULL);
 169     bool prev_found = false;
 170     bool next_found = false;
 171     for (FreeChunk* curFC = retTL->head();
 172          curFC != NULL; curFC = curFC->next()) {
 173       assert(curFC != tc, "Chunk is still in list");
 174       if (curFC == prevFC) {
 175         prev_found = true;
 176       }
 177       if (curFC == nextTC) {
 178         next_found = true;
 179       }
 180     }
 181     assert(prevFC == NULL || prev_found, "Chunk was lost from list");
 182     assert(nextTC == NULL || next_found, "Chunk was lost from list");
 183     assert(retTL->parent() == NULL ||
 184            retTL == retTL->parent()->left() ||
 185            retTL == retTL->parent()->right(),
 186            "list is inconsistent");
 187   )
 188   retTL->decrement_count();
 189 
 190   assert(tc->isFree(), "Should still be a free chunk");
 191   assert(retTL->head() == NULL || retTL->head()->prev() == NULL,
 192     "list invariant");
 193   assert(retTL->tail() == NULL || retTL->tail()->next() == NULL,
 194     "list invariant");
 195   return retTL;
 196 }
 197 void TreeList::returnChunkAtTail(TreeChunk* chunk) {
 198   assert(chunk != NULL, "returning NULL chunk");
 199   assert(chunk->list() == this, "list should be set for chunk");
 200   assert(tail() != NULL, "The tree list is embedded in the first chunk");
 201   // which means that the list can never be empty.
 202   assert(!verifyChunkInFreeLists(chunk), "Double entry");
 203   assert(head() == NULL || head()->prev() == NULL, "list invariant");
 204   assert(tail() == NULL || tail()->next() == NULL, "list invariant");
 205 
 206   FreeChunk* fc = tail();
 207   fc->linkAfter(chunk);
 208   link_tail(chunk);
 209 
 210   assert(!tail() || size() == tail()->size(), "Wrong sized chunk in list");
 211   increment_count();
 212   debug_only(increment_returnedBytes_by(chunk->size()*sizeof(HeapWord));)
 213   assert(head() == NULL || head()->prev() == NULL, "list invariant");
 214   assert(tail() == NULL || tail()->next() == NULL, "list invariant");
 215 }
 216 
 217 // Add this chunk at the head of the list.  "At the head of the list"
 218 // is defined to be after the chunk pointer to by head().  This is
 219 // because the TreeList is embedded in the first TreeChunk in the
 220 // list.  See the definition of TreeChunk.
 221 void TreeList::returnChunkAtHead(TreeChunk* chunk) {
 222   assert(chunk->list() == this, "list should be set for chunk");
 223   assert(head() != NULL, "The tree list is embedded in the first chunk");
 224   assert(chunk != NULL, "returning NULL chunk");
 225   assert(!verifyChunkInFreeLists(chunk), "Double entry");
 226   assert(head() == NULL || head()->prev() == NULL, "list invariant");
 227   assert(tail() == NULL || tail()->next() == NULL, "list invariant");
 228 
 229   FreeChunk* fc = head()->next();
 230   if (fc != NULL) {
 231     chunk->linkAfter(fc);
 232   } else {
 233     assert(tail() == NULL, "List is inconsistent");
 234     link_tail(chunk);
 235   }
 236   head()->linkAfter(chunk);
 237   assert(!head() || size() == head()->size(), "Wrong sized chunk in list");
 238   increment_count();
 239   debug_only(increment_returnedBytes_by(chunk->size()*sizeof(HeapWord));)
 240   assert(head() == NULL || head()->prev() == NULL, "list invariant");
 241   assert(tail() == NULL || tail()->next() == NULL, "list invariant");
 242 }
 243 
 244 TreeChunk* TreeList::head_as_TreeChunk() {
 245   assert(head() == NULL || TreeChunk::as_TreeChunk(head())->list() == this,
 246     "Wrong type of chunk?");
 247   return TreeChunk::as_TreeChunk(head());
 248 }
 249 
 250 TreeChunk* TreeList::first_available() {
 251   guarantee(head() != NULL, "The head of the list cannot be NULL");
 252   FreeChunk* fc = head()->next();
 253   TreeChunk* retTC;
 254   if (fc == NULL) {
 255     retTC = head_as_TreeChunk();
 256   } else {
 257     retTC = TreeChunk::as_TreeChunk(fc);
 258   }
 259   assert(retTC->list() == this, "Wrong type of chunk.");
 260   return retTC;
 261 }
 262 
 263 BinaryTreeDictionary::BinaryTreeDictionary(MemRegion mr, bool splay):
 264   _splay(splay)
 265 {
 266   assert(mr.byte_size() > MIN_TREE_CHUNK_SIZE, "minimum chunk size");
 267 
 268   reset(mr);
 269   assert(root()->left() == NULL, "reset check failed");
 270   assert(root()->right() == NULL, "reset check failed");
 271   assert(root()->head()->next() == NULL, "reset check failed");
 272   assert(root()->head()->prev() == NULL, "reset check failed");
 273   assert(totalSize() == root()->size(), "reset check failed");
 274   assert(totalFreeBlocks() == 1, "reset check failed");
 275 }
 276 
 277 void BinaryTreeDictionary::inc_totalSize(size_t inc) {
 278   _totalSize = _totalSize + inc;
 279 }
 280 
 281 void BinaryTreeDictionary::dec_totalSize(size_t dec) {
 282   _totalSize = _totalSize - dec;
 283 }
 284 
 285 void BinaryTreeDictionary::reset(MemRegion mr) {
 286   assert(mr.byte_size() > MIN_TREE_CHUNK_SIZE, "minimum chunk size");
 287   set_root(TreeList::as_TreeList(mr.start(), mr.word_size()));
 288   set_totalSize(mr.word_size());
 289   set_totalFreeBlocks(1);
 290 }
 291 
 292 void BinaryTreeDictionary::reset(HeapWord* addr, size_t byte_size) {
 293   MemRegion mr(addr, heap_word_size(byte_size));
 294   reset(mr);
 295 }
 296 
 297 void BinaryTreeDictionary::reset() {
 298   set_root(NULL);
 299   set_totalSize(0);
 300   set_totalFreeBlocks(0);
 301 }
 302 
 303 // Get a free block of size at least size from tree, or NULL.
 304 // If a splay step is requested, the removal algorithm (only) incorporates
 305 // a splay step as follows:
 306 // . the search proceeds down the tree looking for a possible
 307 //   match. At the (closest) matching location, an appropriate splay step is applied
 308 //   (zig, zig-zig or zig-zag). A chunk of the appropriate size is then returned
 309 //   if available, and if it's the last chunk, the node is deleted. A deteleted
 310 //   node is replaced in place by its tree successor.
 311 TreeChunk*
 312 BinaryTreeDictionary::getChunkFromTree(size_t size, Dither dither, bool splay)
 313 {
 314   TreeList *curTL, *prevTL;
 315   TreeChunk* retTC = NULL;
 316   assert(size >= MIN_TREE_CHUNK_SIZE, "minimum chunk size");
 317   if (FLSVerifyDictionary) {
 318     verifyTree();
 319   }
 320   // starting at the root, work downwards trying to find match.
 321   // Remember the last node of size too great or too small.
 322   for (prevTL = curTL = root(); curTL != NULL;) {
 323     if (curTL->size() == size) {        // exact match
 324       break;
 325     }
 326     prevTL = curTL;
 327     if (curTL->size() < size) {        // proceed to right sub-tree
 328       curTL = curTL->right();
 329     } else {                           // proceed to left sub-tree
 330       assert(curTL->size() > size, "size inconsistency");
 331       curTL = curTL->left();
 332     }
 333   }
 334   if (curTL == NULL) { // couldn't find exact match
 335     // try and find the next larger size by walking back up the search path
 336     for (curTL = prevTL; curTL != NULL;) {
 337       if (curTL->size() >= size) break;
 338       else curTL = curTL->parent();
 339     }
 340     assert(curTL == NULL || curTL->count() > 0,
 341       "An empty list should not be in the tree");
 342   }
 343   if (curTL != NULL) {
 344     assert(curTL->size() >= size, "size inconsistency");
 345     if (UseCMSAdaptiveFreeLists) {
 346 
 347       // A candidate chunk has been found.  If it is already under
 348       // populated, get a chunk associated with the hint for this
 349       // chunk.
 350       if (curTL->surplus() <= 0) {
 351         /* Use the hint to find a size with a surplus, and reset the hint. */
 352         TreeList* hintTL = curTL;
 353         while (hintTL->hint() != 0) {
 354           assert(hintTL->hint() == 0 || hintTL->hint() > hintTL->size(),
 355             "hint points in the wrong direction");
 356           hintTL = findList(hintTL->hint());
 357           assert(curTL != hintTL, "Infinite loop");
 358           if (hintTL == NULL ||
 359               hintTL == curTL /* Should not happen but protect against it */ ) {
 360             // No useful hint.  Set the hint to NULL and go on.
 361             curTL->set_hint(0);
 362             break;
 363           }
 364           assert(hintTL->size() > size, "hint is inconsistent");
 365           if (hintTL->surplus() > 0) {
 366             // The hint led to a list that has a surplus.  Use it.
 367             // Set the hint for the candidate to an overpopulated
 368             // size.
 369             curTL->set_hint(hintTL->size());
 370             // Change the candidate.
 371             curTL = hintTL;
 372             break;
 373           }
 374           // The evm code reset the hint of the candidate as
 375           // at an interrim point.  Why?  Seems like this leaves
 376           // the hint pointing to a list that didn't work.
 377           // curTL->set_hint(hintTL->size());
 378         }
 379       }
 380     }
 381     // don't waste time splaying if chunk's singleton
 382     if (splay && curTL->head()->next() != NULL) {
 383       semiSplayStep(curTL);
 384     }
 385     retTC = curTL->first_available();
 386     assert((retTC != NULL) && (curTL->count() > 0),
 387       "A list in the binary tree should not be NULL");
 388     assert(retTC->size() >= size,
 389       "A chunk of the wrong size was found");
 390     removeChunkFromTree(retTC);
 391     assert(retTC->isFree(), "Header is not marked correctly");
 392   }
 393 
 394   if (FLSVerifyDictionary) {
 395     verify();
 396   }
 397   return retTC;
 398 }
 399 
 400 TreeList* BinaryTreeDictionary::findList(size_t size) const {
 401   TreeList* curTL;
 402   for (curTL = root(); curTL != NULL;) {
 403     if (curTL->size() == size) {        // exact match
 404       break;
 405     }
 406 
 407     if (curTL->size() < size) {        // proceed to right sub-tree
 408       curTL = curTL->right();
 409     } else {                           // proceed to left sub-tree
 410       assert(curTL->size() > size, "size inconsistency");
 411       curTL = curTL->left();
 412     }
 413   }
 414   return curTL;
 415 }
 416 
 417 
 418 bool BinaryTreeDictionary::verifyChunkInFreeLists(FreeChunk* tc) const {
 419   size_t size = tc->size();
 420   TreeList* tl = findList(size);
 421   if (tl == NULL) {
 422     return false;
 423   } else {
 424     return tl->verifyChunkInFreeLists(tc);
 425   }
 426 }
 427 
 428 FreeChunk* BinaryTreeDictionary::findLargestDict() const {
 429   TreeList *curTL = root();
 430   if (curTL != NULL) {
 431     while(curTL->right() != NULL) curTL = curTL->right();
 432     return curTL->first_available();
 433   } else {
 434     return NULL;
 435   }
 436 }
 437 
 438 // Remove the current chunk from the tree.  If it is not the last
 439 // chunk in a list on a tree node, just unlink it.
 440 // If it is the last chunk in the list (the next link is NULL),
 441 // remove the node and repair the tree.
 442 TreeChunk*
 443 BinaryTreeDictionary::removeChunkFromTree(TreeChunk* tc) {
 444   assert(tc != NULL, "Should not call with a NULL chunk");
 445   assert(tc->isFree(), "Header is not marked correctly");
 446 
 447   TreeList *newTL, *parentTL;
 448   TreeChunk* retTC;
 449   TreeList* tl = tc->list();
 450   debug_only(
 451     bool removing_only_chunk = false;
 452     if (tl == _root) {
 453       if ((_root->left() == NULL) && (_root->right() == NULL)) {
 454         if (_root->count() == 1) {
 455           assert(_root->head() == tc, "Should only be this one chunk");
 456           removing_only_chunk = true;
 457         }
 458       }
 459     }
 460   )
 461   assert(tl != NULL, "List should be set");
 462   assert(tl->parent() == NULL || tl == tl->parent()->left() ||
 463          tl == tl->parent()->right(), "list is inconsistent");
 464 
 465   bool complicatedSplice = false;
 466 
 467   retTC = tc;
 468   // Removing this chunk can have the side effect of changing the node
 469   // (TreeList*) in the tree.  If the node is the root, update it.
 470   TreeList* replacementTL = tl->removeChunkReplaceIfNeeded(tc);
 471   assert(tc->isFree(), "Chunk should still be free");
 472   assert(replacementTL->parent() == NULL ||
 473          replacementTL == replacementTL->parent()->left() ||
 474          replacementTL == replacementTL->parent()->right(),
 475          "list is inconsistent");
 476   if (tl == root()) {
 477     assert(replacementTL->parent() == NULL, "Incorrectly replacing root");
 478     set_root(replacementTL);
 479   }
 480   debug_only(
 481     if (tl != replacementTL) {
 482       assert(replacementTL->head() != NULL,
 483         "If the tree list was replaced, it should not be a NULL list");
 484       TreeList* rhl = replacementTL->head_as_TreeChunk()->list();
 485       TreeList* rtl = TreeChunk::as_TreeChunk(replacementTL->tail())->list();
 486       assert(rhl == replacementTL, "Broken head");
 487       assert(rtl == replacementTL, "Broken tail");
 488       assert(replacementTL->size() == tc->size(),  "Broken size");
 489     }
 490   )
 491 
 492   // Does the tree need to be repaired?
 493   if (replacementTL->count() == 0) {
 494     assert(replacementTL->head() == NULL &&
 495            replacementTL->tail() == NULL, "list count is incorrect");
 496     // Find the replacement node for the (soon to be empty) node being removed.
 497     // if we have a single (or no) child, splice child in our stead
 498     if (replacementTL->left() == NULL) {
 499       // left is NULL so pick right.  right may also be NULL.
 500       newTL = replacementTL->right();
 501       debug_only(replacementTL->clearRight();)
 502     } else if (replacementTL->right() == NULL) {
 503       // right is NULL
 504       newTL = replacementTL->left();
 505       debug_only(replacementTL->clearLeft();)
 506     } else {  // we have both children, so, by patriarchal convention,
 507               // my replacement is least node in right sub-tree
 508       complicatedSplice = true;
 509       newTL = removeTreeMinimum(replacementTL->right());
 510       assert(newTL != NULL && newTL->left() == NULL &&
 511              newTL->right() == NULL, "sub-tree minimum exists");
 512     }
 513     // newTL is the replacement for the (soon to be empty) node.
 514     // newTL may be NULL.
 515     // should verify; we just cleanly excised our replacement
 516     if (FLSVerifyDictionary) {
 517       verifyTree();
 518     }
 519     // first make newTL my parent's child
 520     if ((parentTL = replacementTL->parent()) == NULL) {
 521       // newTL should be root
 522       assert(tl == root(), "Incorrectly replacing root");
 523       set_root(newTL);
 524       if (newTL != NULL) {
 525         newTL->clearParent();
 526       }
 527     } else if (parentTL->right() == replacementTL) {
 528       // replacementTL is a right child
 529       parentTL->setRight(newTL);
 530     } else {                                // replacementTL is a left child
 531       assert(parentTL->left() == replacementTL, "should be left child");
 532       parentTL->setLeft(newTL);
 533     }
 534     debug_only(replacementTL->clearParent();)
 535     if (complicatedSplice) {  // we need newTL to get replacementTL's
 536                               // two children
 537       assert(newTL != NULL &&
 538              newTL->left() == NULL && newTL->right() == NULL,
 539             "newTL should not have encumbrances from the past");
 540       // we'd like to assert as below:
 541       // assert(replacementTL->left() != NULL && replacementTL->right() != NULL,
 542       //       "else !complicatedSplice");
 543       // ... however, the above assertion is too strong because we aren't
 544       // guaranteed that replacementTL->right() is still NULL.
 545       // Recall that we removed
 546       // the right sub-tree minimum from replacementTL.
 547       // That may well have been its right
 548       // child! So we'll just assert half of the above:
 549       assert(replacementTL->left() != NULL, "else !complicatedSplice");
 550       newTL->setLeft(replacementTL->left());
 551       newTL->setRight(replacementTL->right());
 552       debug_only(
 553         replacementTL->clearRight();
 554         replacementTL->clearLeft();
 555       )
 556     }
 557     assert(replacementTL->right() == NULL &&
 558            replacementTL->left() == NULL &&
 559            replacementTL->parent() == NULL,
 560         "delete without encumbrances");
 561   }
 562 
 563   assert(totalSize() >= retTC->size(), "Incorrect total size");
 564   dec_totalSize(retTC->size());     // size book-keeping
 565   assert(totalFreeBlocks() > 0, "Incorrect total count");
 566   set_totalFreeBlocks(totalFreeBlocks() - 1);
 567 
 568   assert(retTC != NULL, "null chunk?");
 569   assert(retTC->prev() == NULL && retTC->next() == NULL,
 570          "should return without encumbrances");
 571   if (FLSVerifyDictionary) {
 572     verifyTree();
 573   }
 574   assert(!removing_only_chunk || _root == NULL, "root should be NULL");
 575   return TreeChunk::as_TreeChunk(retTC);
 576 }
 577 
 578 // Remove the leftmost node (lm) in the tree and return it.
 579 // If lm has a right child, link it to the left node of
 580 // the parent of lm.
 581 TreeList* BinaryTreeDictionary::removeTreeMinimum(TreeList* tl) {
 582   assert(tl != NULL && tl->parent() != NULL, "really need a proper sub-tree");
 583   // locate the subtree minimum by walking down left branches
 584   TreeList* curTL = tl;
 585   for (; curTL->left() != NULL; curTL = curTL->left());
 586   // obviously curTL now has at most one child, a right child
 587   if (curTL != root()) {  // Should this test just be removed?
 588     TreeList* parentTL = curTL->parent();
 589     if (parentTL->left() == curTL) { // curTL is a left child
 590       parentTL->setLeft(curTL->right());
 591     } else {
 592       // If the list tl has no left child, then curTL may be
 593       // the right child of parentTL.
 594       assert(parentTL->right() == curTL, "should be a right child");
 595       parentTL->setRight(curTL->right());
 596     }
 597   } else {
 598     // The only use of this method would not pass the root of the
 599     // tree (as indicated by the assertion above that the tree list
 600     // has a parent) but the specification does not explicitly exclude the
 601     // passing of the root so accomodate it.
 602     set_root(NULL);
 603   }
 604   debug_only(
 605     curTL->clearParent();  // Test if this needs to be cleared
 606     curTL->clearRight();    // recall, above, left child is already null
 607   )
 608   // we just excised a (non-root) node, we should still verify all tree invariants
 609   if (FLSVerifyDictionary) {
 610     verifyTree();
 611   }
 612   return curTL;
 613 }
 614 
 615 // Based on a simplification of the algorithm by Sleator and Tarjan (JACM 1985).
 616 // The simplifications are the following:
 617 // . we splay only when we delete (not when we insert)
 618 // . we apply a single spay step per deletion/access
 619 // By doing such partial splaying, we reduce the amount of restructuring,
 620 // while getting a reasonably efficient search tree (we think).
 621 // [Measurements will be needed to (in)validate this expectation.]
 622 
 623 void BinaryTreeDictionary::semiSplayStep(TreeList* tc) {
 624   // apply a semi-splay step at the given node:
 625   // . if root, norting needs to be done
 626   // . if child of root, splay once
 627   // . else zig-zig or sig-zag depending on path from grandparent
 628   if (root() == tc) return;
 629   warning("*** Splaying not yet implemented; "
 630           "tree operations may be inefficient ***");
 631 }
 632 
 633 void BinaryTreeDictionary::insertChunkInTree(FreeChunk* fc) {
 634   TreeList *curTL, *prevTL;
 635   size_t size = fc->size();
 636 
 637   assert(size >= MIN_TREE_CHUNK_SIZE, "too small to be a TreeList");
 638   if (FLSVerifyDictionary) {
 639     verifyTree();
 640   }
 641   // XXX: do i need to clear the FreeChunk fields, let me do it just in case
 642   // Revisit this later
 643 
 644   fc->clearNext();
 645   fc->linkPrev(NULL);
 646 
 647   // work down from the _root, looking for insertion point
 648   for (prevTL = curTL = root(); curTL != NULL;) {
 649     if (curTL->size() == size)  // exact match
 650       break;
 651     prevTL = curTL;
 652     if (curTL->size() > size) { // follow left branch
 653       curTL = curTL->left();
 654     } else {                    // follow right branch
 655       assert(curTL->size() < size, "size inconsistency");
 656       curTL = curTL->right();
 657     }
 658   }
 659   TreeChunk* tc = TreeChunk::as_TreeChunk(fc);
 660   // This chunk is being returned to the binary try.  It's embedded
 661   // TreeList should be unused at this point.
 662   tc->initialize();
 663   if (curTL != NULL) {          // exact match
 664     tc->set_list(curTL);
 665     curTL->returnChunkAtTail(tc);
 666   } else {                     // need a new node in tree
 667     tc->clearNext();
 668     tc->linkPrev(NULL);
 669     TreeList* newTL = TreeList::as_TreeList(tc);
 670     assert(((TreeChunk*)tc)->list() == newTL,
 671       "List was not initialized correctly");
 672     if (prevTL == NULL) {      // we are the only tree node
 673       assert(root() == NULL, "control point invariant");
 674       set_root(newTL);
 675     } else {                   // insert under prevTL ...
 676       if (prevTL->size() < size) {   // am right child
 677         assert(prevTL->right() == NULL, "control point invariant");
 678         prevTL->setRight(newTL);
 679       } else {                       // am left child
 680         assert(prevTL->size() > size && prevTL->left() == NULL, "cpt pt inv");
 681         prevTL->setLeft(newTL);
 682       }
 683     }
 684   }
 685   assert(tc->list() != NULL, "Tree list should be set");
 686 
 687   inc_totalSize(size);
 688   // Method 'totalSizeInTree' walks through the every block in the
 689   // tree, so it can cause significant performance loss if there are
 690   // many blocks in the tree
 691   assert(!FLSVerifyDictionary || totalSizeInTree(root()) == totalSize(), "_totalSize inconsistency");
 692   set_totalFreeBlocks(totalFreeBlocks() + 1);
 693   if (FLSVerifyDictionary) {
 694     verifyTree();
 695   }
 696 }
 697 
 698 size_t BinaryTreeDictionary::maxChunkSize() const {
 699   verify_par_locked();
 700   TreeList* tc = root();
 701   if (tc == NULL) return 0;
 702   for (; tc->right() != NULL; tc = tc->right());
 703   return tc->size();
 704 }
 705 
 706 size_t BinaryTreeDictionary::totalListLength(TreeList* tl) const {
 707   size_t res;
 708   res = tl->count();
 709 #ifdef ASSERT
 710   size_t cnt;
 711   FreeChunk* tc = tl->head();
 712   for (cnt = 0; tc != NULL; tc = tc->next(), cnt++);
 713   assert(res == cnt, "The count is not being maintained correctly");
 714 #endif
 715   return res;
 716 }
 717 
 718 size_t BinaryTreeDictionary::totalSizeInTree(TreeList* tl) const {
 719   if (tl == NULL)
 720     return 0;
 721   return (tl->size() * totalListLength(tl)) +
 722          totalSizeInTree(tl->left())    +
 723          totalSizeInTree(tl->right());
 724 }
 725 
 726 double BinaryTreeDictionary::sum_of_squared_block_sizes(TreeList* const tl) const {
 727   if (tl == NULL) {
 728     return 0.0;
 729   }
 730   double size = (double)(tl->size());
 731   double curr = size * size * totalListLength(tl);
 732   curr += sum_of_squared_block_sizes(tl->left());
 733   curr += sum_of_squared_block_sizes(tl->right());
 734   return curr;
 735 }
 736 
 737 size_t BinaryTreeDictionary::totalFreeBlocksInTree(TreeList* tl) const {
 738   if (tl == NULL)
 739     return 0;
 740   return totalListLength(tl) +
 741          totalFreeBlocksInTree(tl->left()) +
 742          totalFreeBlocksInTree(tl->right());
 743 }
 744 
 745 size_t BinaryTreeDictionary::numFreeBlocks() const {
 746   assert(totalFreeBlocksInTree(root()) == totalFreeBlocks(),
 747          "_totalFreeBlocks inconsistency");
 748   return totalFreeBlocks();
 749 }
 750 
 751 size_t BinaryTreeDictionary::treeHeightHelper(TreeList* tl) const {
 752   if (tl == NULL)
 753     return 0;
 754   return 1 + MAX2(treeHeightHelper(tl->left()),
 755                   treeHeightHelper(tl->right()));
 756 }
 757 
 758 size_t BinaryTreeDictionary::treeHeight() const {
 759   return treeHeightHelper(root());
 760 }
 761 
 762 size_t BinaryTreeDictionary::totalNodesHelper(TreeList* tl) const {
 763   if (tl == NULL) {
 764     return 0;
 765   }
 766   return 1 + totalNodesHelper(tl->left()) +
 767     totalNodesHelper(tl->right());
 768 }
 769 
 770 size_t BinaryTreeDictionary::totalNodesInTree(TreeList* tl) const {
 771   return totalNodesHelper(root());
 772 }
 773 
 774 void BinaryTreeDictionary::dictCensusUpdate(size_t size, bool split, bool birth){
 775   TreeList* nd = findList(size);
 776   if (nd) {
 777     if (split) {
 778       if (birth) {
 779         nd->increment_splitBirths();
 780         nd->increment_surplus();
 781       }  else {
 782         nd->increment_splitDeaths();
 783         nd->decrement_surplus();
 784       }
 785     } else {
 786       if (birth) {
 787         nd->increment_coalBirths();
 788         nd->increment_surplus();
 789       } else {
 790         nd->increment_coalDeaths();
 791         nd->decrement_surplus();
 792       }
 793     }
 794   }
 795   // A list for this size may not be found (nd == 0) if
 796   //   This is a death where the appropriate list is now
 797   //     empty and has been removed from the list.
 798   //   This is a birth associated with a LinAB.  The chunk
 799   //     for the LinAB is not in the dictionary.
 800 }
 801 
 802 bool BinaryTreeDictionary::coalDictOverPopulated(size_t size) {
 803   TreeList* list_of_size = findList(size);
 804   // None of requested size implies overpopulated.
 805   return list_of_size == NULL || list_of_size->coalDesired() <= 0 ||
 806          list_of_size->count() > list_of_size->coalDesired();
 807 }
 808 
 809 // Closures for walking the binary tree.
 810 //   do_list() walks the free list in a node applying the closure
 811 //     to each free chunk in the list
 812 //   do_tree() walks the nodes in the binary tree applying do_list()
 813 //     to each list at each node.
 814 
 815 class TreeCensusClosure : public StackObj {
 816  protected:
 817   virtual void do_list(FreeList* fl) = 0;
 818  public:
 819   virtual void do_tree(TreeList* tl) = 0;
 820 };
 821 
 822 class AscendTreeCensusClosure : public TreeCensusClosure {
 823  public:
 824   void do_tree(TreeList* tl) {
 825     if (tl != NULL) {
 826       do_tree(tl->left());
 827       do_list(tl);
 828       do_tree(tl->right());
 829     }
 830   }
 831 };
 832 
 833 class DescendTreeCensusClosure : public TreeCensusClosure {
 834  public:
 835   void do_tree(TreeList* tl) {
 836     if (tl != NULL) {
 837       do_tree(tl->right());
 838       do_list(tl);
 839       do_tree(tl->left());
 840     }
 841   }
 842 };
 843 
 844 // For each list in the tree, calculate the desired, desired
 845 // coalesce, count before sweep, and surplus before sweep.
 846 class BeginSweepClosure : public AscendTreeCensusClosure {
 847   double _percentage;
 848   float _inter_sweep_current;
 849   float _inter_sweep_estimate;
 850 
 851  public:
 852   BeginSweepClosure(double p, float inter_sweep_current,
 853                               float inter_sweep_estimate) :
 854    _percentage(p),
 855    _inter_sweep_current(inter_sweep_current),
 856    _inter_sweep_estimate(inter_sweep_estimate) { }
 857 
 858   void do_list(FreeList* fl) {
 859     double coalSurplusPercent = _percentage;
 860     fl->compute_desired(_inter_sweep_current, _inter_sweep_estimate);
 861     fl->set_coalDesired((ssize_t)((double)fl->desired() * coalSurplusPercent));
 862     fl->set_beforeSweep(fl->count());
 863     fl->set_bfrSurp(fl->surplus());
 864   }
 865 };
 866 
 867 // Used to search the tree until a condition is met.
 868 // Similar to TreeCensusClosure but searches the
 869 // tree and returns promptly when found.
 870 
 871 class TreeSearchClosure : public StackObj {
 872  protected:
 873   virtual bool do_list(FreeList* fl) = 0;
 874  public:
 875   virtual bool do_tree(TreeList* tl) = 0;
 876 };
 877 
 878 #if 0 //  Don't need this yet but here for symmetry.
 879 class AscendTreeSearchClosure : public TreeSearchClosure {
 880  public:
 881   bool do_tree(TreeList* tl) {
 882     if (tl != NULL) {
 883       if (do_tree(tl->left())) return true;
 884       if (do_list(tl)) return true;
 885       if (do_tree(tl->right())) return true;
 886     }
 887     return false;
 888   }
 889 };
 890 #endif
 891 
 892 class DescendTreeSearchClosure : public TreeSearchClosure {
 893  public:
 894   bool do_tree(TreeList* tl) {
 895     if (tl != NULL) {
 896       if (do_tree(tl->right())) return true;
 897       if (do_list(tl)) return true;
 898       if (do_tree(tl->left())) return true;
 899     }
 900     return false;
 901   }
 902 };
 903 
 904 // Searches the tree for a chunk that ends at the
 905 // specified address.
 906 class EndTreeSearchClosure : public DescendTreeSearchClosure {
 907   HeapWord* _target;
 908   FreeChunk* _found;
 909 
 910  public:
 911   EndTreeSearchClosure(HeapWord* target) : _target(target), _found(NULL) {}
 912   bool do_list(FreeList* fl) {
 913     FreeChunk* item = fl->head();
 914     while (item != NULL) {
 915       if (item->end() == _target) {
 916         _found = item;
 917         return true;
 918       }
 919       item = item->next();
 920     }
 921     return false;
 922   }
 923   FreeChunk* found() { return _found; }
 924 };
 925 
 926 FreeChunk* BinaryTreeDictionary::find_chunk_ends_at(HeapWord* target) const {
 927   EndTreeSearchClosure etsc(target);
 928   bool found_target = etsc.do_tree(root());
 929   assert(found_target || etsc.found() == NULL, "Consistency check");
 930   assert(!found_target || etsc.found() != NULL, "Consistency check");
 931   return etsc.found();
 932 }
 933 
 934 void BinaryTreeDictionary::beginSweepDictCensus(double coalSurplusPercent,
 935   float inter_sweep_current, float inter_sweep_estimate) {
 936   BeginSweepClosure bsc(coalSurplusPercent, inter_sweep_current,
 937                                             inter_sweep_estimate);
 938   bsc.do_tree(root());
 939 }
 940 
 941 // Closures and methods for calculating total bytes returned to the
 942 // free lists in the tree.
 943 NOT_PRODUCT(
 944   class InitializeDictReturnedBytesClosure : public AscendTreeCensusClosure {
 945    public:
 946     void do_list(FreeList* fl) {
 947       fl->set_returnedBytes(0);
 948     }
 949   };
 950 
 951   void BinaryTreeDictionary::initializeDictReturnedBytes() {
 952     InitializeDictReturnedBytesClosure idrb;
 953     idrb.do_tree(root());
 954   }
 955 
 956   class ReturnedBytesClosure : public AscendTreeCensusClosure {
 957     size_t _dictReturnedBytes;
 958    public:
 959     ReturnedBytesClosure() { _dictReturnedBytes = 0; }
 960     void do_list(FreeList* fl) {
 961       _dictReturnedBytes += fl->returnedBytes();
 962     }
 963     size_t dictReturnedBytes() { return _dictReturnedBytes; }
 964   };
 965 
 966   size_t BinaryTreeDictionary::sumDictReturnedBytes() {
 967     ReturnedBytesClosure rbc;
 968     rbc.do_tree(root());
 969 
 970     return rbc.dictReturnedBytes();
 971   }
 972 
 973   // Count the number of entries in the tree.
 974   class treeCountClosure : public DescendTreeCensusClosure {
 975    public:
 976     uint count;
 977     treeCountClosure(uint c) { count = c; }
 978     void do_list(FreeList* fl) {
 979       count++;
 980     }
 981   };
 982 
 983   size_t BinaryTreeDictionary::totalCount() {
 984     treeCountClosure ctc(0);
 985     ctc.do_tree(root());
 986     return ctc.count;
 987   }
 988 )
 989 
 990 // Calculate surpluses for the lists in the tree.
 991 class setTreeSurplusClosure : public AscendTreeCensusClosure {
 992   double percentage;
 993  public:
 994   setTreeSurplusClosure(double v) { percentage = v; }
 995   void do_list(FreeList* fl) {
 996     double splitSurplusPercent = percentage;
 997     fl->set_surplus(fl->count() -
 998                    (ssize_t)((double)fl->desired() * splitSurplusPercent));
 999   }
1000 };
1001 
1002 void BinaryTreeDictionary::setTreeSurplus(double splitSurplusPercent) {
1003   setTreeSurplusClosure sts(splitSurplusPercent);
1004   sts.do_tree(root());
1005 }
1006 
1007 // Set hints for the lists in the tree.
1008 class setTreeHintsClosure : public DescendTreeCensusClosure {
1009   size_t hint;
1010  public:
1011   setTreeHintsClosure(size_t v) { hint = v; }
1012   void do_list(FreeList* fl) {
1013     fl->set_hint(hint);
1014     assert(fl->hint() == 0 || fl->hint() > fl->size(),
1015       "Current hint is inconsistent");
1016     if (fl->surplus() > 0) {
1017       hint = fl->size();
1018     }
1019   }
1020 };
1021 
1022 void BinaryTreeDictionary::setTreeHints(void) {
1023   setTreeHintsClosure sth(0);
1024   sth.do_tree(root());
1025 }
1026 
1027 // Save count before previous sweep and splits and coalesces.
1028 class clearTreeCensusClosure : public AscendTreeCensusClosure {
1029   void do_list(FreeList* fl) {
1030     fl->set_prevSweep(fl->count());
1031     fl->set_coalBirths(0);
1032     fl->set_coalDeaths(0);
1033     fl->set_splitBirths(0);
1034     fl->set_splitDeaths(0);
1035   }
1036 };
1037 
1038 void BinaryTreeDictionary::clearTreeCensus(void) {
1039   clearTreeCensusClosure ctc;
1040   ctc.do_tree(root());
1041 }
1042 
1043 // Do reporting and post sweep clean up.
1044 void BinaryTreeDictionary::endSweepDictCensus(double splitSurplusPercent) {
1045   // Does walking the tree 3 times hurt?
1046   setTreeSurplus(splitSurplusPercent);
1047   setTreeHints();
1048   if (PrintGC && Verbose) {
1049     reportStatistics();
1050   }
1051   clearTreeCensus();
1052 }
1053 
1054 // Print summary statistics
1055 void BinaryTreeDictionary::reportStatistics() const {
1056   verify_par_locked();
1057   gclog_or_tty->print("Statistics for BinaryTreeDictionary:\n"
1058          "------------------------------------\n");
1059   size_t totalSize = totalChunkSize(debug_only(NULL));
1060   size_t    freeBlocks = numFreeBlocks();
1061   gclog_or_tty->print("Total Free Space: %d\n", totalSize);
1062   gclog_or_tty->print("Max   Chunk Size: %d\n", maxChunkSize());
1063   gclog_or_tty->print("Number of Blocks: %d\n", freeBlocks);
1064   if (freeBlocks > 0) {
1065     gclog_or_tty->print("Av.  Block  Size: %d\n", totalSize/freeBlocks);
1066   }
1067   gclog_or_tty->print("Tree      Height: %d\n", treeHeight());
1068 }
1069 
1070 // Print census information - counts, births, deaths, etc.
1071 // for each list in the tree.  Also print some summary
1072 // information.
1073 class printTreeCensusClosure : public AscendTreeCensusClosure {
1074   size_t _totalFree;
1075   AllocationStats _totals;
1076   size_t _count;
1077 
1078  public:
1079   printTreeCensusClosure() {
1080     _totalFree = 0;
1081     _count = 0;
1082     _totals.initialize();
1083   }
1084   AllocationStats* totals() { return &_totals; }
1085   size_t count() { return _count; }
1086   void increment_count_by(size_t v) { _count += v; }
1087   size_t totalFree() { return _totalFree; }
1088   void increment_totalFree_by(size_t v) { _totalFree += v; }
1089   void do_list(FreeList* fl) {
1090     bool nl = false; // "maybe this is not needed" isNearLargestChunk(fl->head());
1091 
1092     gclog_or_tty->print("%c %4d\t\t" "%7d\t" "%7d\t"
1093                "%7d\t"      "%7d\t" "%7d\t" "%7d\t"
1094                "%7d\t"      "%7d\t" "%7d\t"
1095                "%7d\t" "\n",
1096                " n"[nl], fl->size(), fl->bfrSurp(), fl->surplus(),
1097                fl->desired(), fl->prevSweep(), fl->beforeSweep(), fl->count(),
1098                fl->coalBirths(), fl->coalDeaths(), fl->splitBirths(),
1099                fl->splitDeaths());
1100 
1101     increment_totalFree_by(fl->count() * fl->size());
1102     increment_count_by(fl->count());
1103     totals()->set_bfrSurp(totals()->bfrSurp() + fl->bfrSurp());
1104     totals()->set_surplus(totals()->splitDeaths()     + fl->surplus());
1105     totals()->set_prevSweep(totals()->prevSweep()   + fl->prevSweep());
1106     totals()->set_beforeSweep(totals()->beforeSweep() + fl->beforeSweep());
1107     totals()->set_coalBirths(totals()->coalBirths()  + fl->coalBirths());
1108     totals()->set_coalDeaths(totals()->coalDeaths()  + fl->coalDeaths());
1109     totals()->set_splitBirths(totals()->splitBirths() + fl->splitBirths());
1110     totals()->set_splitDeaths(totals()->splitDeaths() + fl->splitDeaths());
1111   }
1112 };
1113 
1114 void BinaryTreeDictionary::printDictCensus(void) const {
1115 
1116   gclog_or_tty->print("\nBinaryTree\n");
1117   gclog_or_tty->print(
1118              "%4s\t\t" "%7s\t"   "%7s\t"    "%7s\t"    "%7s\t"    "%7s\t"
1119              "%7s\t"   "%7s\t"   "%7s\t"    "%7s\t"    "%7s\t"     "\n",
1120              "size",  "bfrsurp", "surplus", "desired", "prvSwep", "bfrSwep",
1121              "count", "cBirths", "cDeaths", "sBirths", "sDeaths");
1122 
1123   printTreeCensusClosure ptc;
1124   ptc.do_tree(root());
1125 
1126   gclog_or_tty->print(
1127              "\t\t"    "%7s\t"    "%7s\t"    "%7s\t"    "%7s\t"
1128              "%7s\t"   "%7s\t"    "%7s\t"    "%7s\t"    "%7s\t"     "\n",
1129                        "bfrsurp", "surplus", "prvSwep", "bfrSwep",
1130              "count",  "cBirths", "cDeaths", "sBirths", "sDeaths");
1131   gclog_or_tty->print(
1132              "%s\t\t"  "%7d\t"    "%7d\t"     "%7d\t"    "%7d\t"
1133              "%7d\t"   "%7d\t"    "%7d\t"     "%7d\t"    "%7d\t"    "\n",
1134              "totl",
1135              ptc.totals()->bfrSurp(),
1136              ptc.totals()->surplus(),
1137              ptc.totals()->prevSweep(),
1138              ptc.totals()->beforeSweep(),
1139              ptc.count(),
1140              ptc.totals()->coalBirths(),
1141              ptc.totals()->coalDeaths(),
1142              ptc.totals()->splitBirths(),
1143              ptc.totals()->splitDeaths());
1144   gclog_or_tty->print("totalFree(words): %7d growth: %8.5f  deficit: %8.5f\n",
1145               ptc.totalFree(),
1146               (double)(ptc.totals()->splitBirths()+ptc.totals()->coalBirths()
1147                        -ptc.totals()->splitDeaths()-ptc.totals()->coalDeaths())
1148               /(ptc.totals()->prevSweep() != 0 ?
1149                 (double)ptc.totals()->prevSweep() : 1.0),
1150              (double)(ptc.totals()->desired() - ptc.count())
1151              /(ptc.totals()->desired() != 0 ?
1152                (double)ptc.totals()->desired() : 1.0));
1153 }
1154 
1155 // Verify the following tree invariants:
1156 // . _root has no parent
1157 // . parent and child point to each other
1158 // . each node's key correctly related to that of its child(ren)
1159 void BinaryTreeDictionary::verifyTree() const {
1160   guarantee(root() == NULL || totalFreeBlocks() == 0 ||
1161     totalSize() != 0, "_totalSize should't be 0?");
1162   guarantee(root() == NULL || root()->parent() == NULL, "_root shouldn't have parent");
1163   verifyTreeHelper(root());
1164 }
1165 
1166 size_t BinaryTreeDictionary::verifyPrevFreePtrs(TreeList* tl) {
1167   size_t ct = 0;
1168   for (FreeChunk* curFC = tl->head(); curFC != NULL; curFC = curFC->next()) {
1169     ct++;
1170     assert(curFC->prev() == NULL || curFC->prev()->isFree(),
1171       "Chunk should be free");
1172   }
1173   return ct;
1174 }
1175 
1176 // Note: this helper is recursive rather than iterative, so use with
1177 // caution on very deep trees; and watch out for stack overflow errors;
1178 // In general, to be used only for debugging.
1179 void BinaryTreeDictionary::verifyTreeHelper(TreeList* tl) const {
1180   if (tl == NULL)
1181     return;
1182   guarantee(tl->size() != 0, "A list must has a size");
1183   guarantee(tl->left()  == NULL || tl->left()->parent()  == tl,
1184          "parent<-/->left");
1185   guarantee(tl->right() == NULL || tl->right()->parent() == tl,
1186          "parent<-/->right");;
1187   guarantee(tl->left() == NULL  || tl->left()->size()    <  tl->size(),
1188          "parent !> left");
1189   guarantee(tl->right() == NULL || tl->right()->size()   >  tl->size(),
1190          "parent !< left");
1191   guarantee(tl->head() == NULL || tl->head()->isFree(), "!Free");
1192   guarantee(tl->head() == NULL || tl->head_as_TreeChunk()->list() == tl,
1193     "list inconsistency");
1194   guarantee(tl->count() > 0 || (tl->head() == NULL && tl->tail() == NULL),
1195     "list count is inconsistent");
1196   guarantee(tl->count() > 1 || tl->head() == tl->tail(),
1197     "list is incorrectly constructed");
1198   size_t count = verifyPrevFreePtrs(tl);
1199   guarantee(count == (size_t)tl->count(), "Node count is incorrect");
1200   if (tl->head() != NULL) {
1201     tl->head_as_TreeChunk()->verifyTreeChunkList();
1202   }
1203   verifyTreeHelper(tl->left());
1204   verifyTreeHelper(tl->right());
1205 }
1206 
1207 void BinaryTreeDictionary::verify() const {
1208   verifyTree();
1209   guarantee(totalSize() == totalSizeInTree(root()), "Total Size inconsistency");
1210 }