1 /*
   2  * Copyright (c) 1997, 2012, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #ifndef SHARE_VM_MEMORY_SPACE_HPP
  26 #define SHARE_VM_MEMORY_SPACE_HPP
  27 
  28 #include "memory/allocation.hpp"
  29 #include "memory/blockOffsetTable.hpp"
  30 #include "memory/cardTableModRefBS.hpp"
  31 #include "memory/iterator.hpp"
  32 #include "memory/memRegion.hpp"
  33 #include "memory/watermark.hpp"
  34 #include "oops/markOop.hpp"
  35 #include "runtime/mutexLocker.hpp"
  36 #include "runtime/prefetch.hpp"
  37 #include "utilities/macros.hpp"
  38 #include "utilities/workgroup.hpp"
  39 #ifdef TARGET_OS_FAMILY_linux
  40 # include "os_linux.inline.hpp"
  41 #endif
  42 #ifdef TARGET_OS_FAMILY_solaris
  43 # include "os_solaris.inline.hpp"
  44 #endif
  45 #ifdef TARGET_OS_FAMILY_windows
  46 # include "os_windows.inline.hpp"
  47 #endif
  48 #ifdef TARGET_OS_FAMILY_bsd
  49 # include "os_bsd.inline.hpp"
  50 #endif
  51 
  52 // A space is an abstraction for the "storage units" backing
  53 // up the generation abstraction. It includes specific
  54 // implementations for keeping track of free and used space,
  55 // for iterating over objects and free blocks, etc.
  56 
  57 // Here's the Space hierarchy:
  58 //
  59 // - Space               -- an asbtract base class describing a heap area
  60 //   - CompactibleSpace  -- a space supporting compaction
  61 //     - CompactibleFreeListSpace -- (used for CMS generation)
  62 //     - ContiguousSpace -- a compactible space in which all free space
  63 //                          is contiguous
  64 //       - EdenSpace     -- contiguous space used as nursery
  65 //         - ConcEdenSpace -- contiguous space with a 'soft end safe' allocation
  66 //       - OffsetTableContigSpace -- contiguous space with a block offset array
  67 //                          that allows "fast" block_start calls
  68 //         - TenuredSpace -- (used for TenuredGeneration)
  69 
  70 // Forward decls.
  71 class Space;
  72 class BlockOffsetArray;
  73 class BlockOffsetArrayContigSpace;
  74 class Generation;
  75 class CompactibleSpace;
  76 class BlockOffsetTable;
  77 class GenRemSet;
  78 class CardTableRS;
  79 class DirtyCardToOopClosure;
  80 
  81 // An oop closure that is circumscribed by a filtering memory region.
  82 class SpaceMemRegionOopsIterClosure: public ExtendedOopClosure {
  83  private:
  84   ExtendedOopClosure* _cl;
  85   MemRegion   _mr;
  86  protected:
  87   template <class T> void do_oop_work(T* p) {
  88     if (_mr.contains(p)) {
  89       _cl->do_oop(p);
  90     }
  91   }
  92  public:
  93   SpaceMemRegionOopsIterClosure(ExtendedOopClosure* cl, MemRegion mr):
  94     _cl(cl), _mr(mr) {}
  95   virtual void do_oop(oop* p);
  96   virtual void do_oop(narrowOop* p);
  97   virtual bool do_metadata() {
  98     // _cl is of type ExtendedOopClosure instead of OopClosure, so that we can check this.
  99     assert(!_cl->do_metadata(), "I've checked all call paths, this shouldn't happen.");
 100     return false;
 101   }
 102   virtual void do_klass(Klass* k)                         { ShouldNotReachHere(); }
 103   virtual void do_class_loader_data(ClassLoaderData* cld) { ShouldNotReachHere(); }
 104 };
 105 
 106 // A Space describes a heap area. Class Space is an abstract
 107 // base class.
 108 //
 109 // Space supports allocation, size computation and GC support is provided.
 110 //
 111 // Invariant: bottom() and end() are on page_size boundaries and
 112 // bottom() <= top() <= end()
 113 // top() is inclusive and end() is exclusive.
 114 
 115 class Space: public CHeapObj<mtGC> {
 116   friend class VMStructs;
 117  protected:
 118   HeapWord* _bottom;
 119   HeapWord* _end;
 120 
 121   // Used in support of save_marks()
 122   HeapWord* _saved_mark_word;
 123 
 124   MemRegionClosure* _preconsumptionDirtyCardClosure;
 125 
 126   // A sequential tasks done structure. This supports
 127   // parallel GC, where we have threads dynamically
 128   // claiming sub-tasks from a larger parallel task.
 129   SequentialSubTasksDone _par_seq_tasks;
 130 
 131   Space():
 132     _bottom(NULL), _end(NULL), _preconsumptionDirtyCardClosure(NULL) { }
 133 
 134  public:
 135   // Accessors
 136   HeapWord* bottom() const         { return _bottom; }
 137   HeapWord* end() const            { return _end;    }
 138   virtual void set_bottom(HeapWord* value) { _bottom = value; }
 139   virtual void set_end(HeapWord* value)    { _end = value; }
 140 
 141   virtual HeapWord* saved_mark_word() const  { return _saved_mark_word; }
 142 
 143   void set_saved_mark_word(HeapWord* p) { _saved_mark_word = p; }
 144 
 145   MemRegionClosure* preconsumptionDirtyCardClosure() const {
 146     return _preconsumptionDirtyCardClosure;
 147   }
 148   void setPreconsumptionDirtyCardClosure(MemRegionClosure* cl) {
 149     _preconsumptionDirtyCardClosure = cl;
 150   }
 151 
 152   // Returns a subregion of the space containing all the objects in
 153   // the space.
 154   virtual MemRegion used_region() const { return MemRegion(bottom(), end()); }
 155 
 156   // Returns a region that is guaranteed to contain (at least) all objects
 157   // allocated at the time of the last call to "save_marks".  If the space
 158   // initializes its DirtyCardToOopClosure's specifying the "contig" option
 159   // (that is, if the space is contiguous), then this region must contain only
 160   // such objects: the memregion will be from the bottom of the region to the
 161   // saved mark.  Otherwise, the "obj_allocated_since_save_marks" method of
 162   // the space must distiguish between objects in the region allocated before
 163   // and after the call to save marks.
 164   virtual MemRegion used_region_at_save_marks() const {
 165     return MemRegion(bottom(), saved_mark_word());
 166   }
 167 
 168   // Initialization.
 169   // "initialize" should be called once on a space, before it is used for
 170   // any purpose.  The "mr" arguments gives the bounds of the space, and
 171   // the "clear_space" argument should be true unless the memory in "mr" is
 172   // known to be zeroed.
 173   virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
 174 
 175   // The "clear" method must be called on a region that may have
 176   // had allocation performed in it, but is now to be considered empty.
 177   virtual void clear(bool mangle_space);
 178 
 179   // For detecting GC bugs.  Should only be called at GC boundaries, since
 180   // some unused space may be used as scratch space during GC's.
 181   // Default implementation does nothing. We also call this when expanding
 182   // a space to satisfy an allocation request. See bug #4668531
 183   virtual void mangle_unused_area() {}
 184   virtual void mangle_unused_area_complete() {}
 185   virtual void mangle_region(MemRegion mr) {}
 186 
 187   // Testers
 188   bool is_empty() const              { return used() == 0; }
 189   bool not_empty() const             { return used() > 0; }
 190 
 191   // Returns true iff the given the space contains the
 192   // given address as part of an allocated object. For
 193   // ceratin kinds of spaces, this might be a potentially
 194   // expensive operation. To prevent performance problems
 195   // on account of its inadvertent use in product jvm's,
 196   // we restrict its use to assertion checks only.
 197   virtual bool is_in(const void* p) const = 0;
 198 
 199   // Returns true iff the given reserved memory of the space contains the
 200   // given address.
 201   bool is_in_reserved(const void* p) const { return _bottom <= p && p < _end; }
 202 
 203   // Returns true iff the given block is not allocated.
 204   virtual bool is_free_block(const HeapWord* p) const = 0;
 205 
 206   // Test whether p is double-aligned
 207   static bool is_aligned(void* p) {
 208     return ((intptr_t)p & (sizeof(double)-1)) == 0;
 209   }
 210 
 211   // Size computations.  Sizes are in bytes.
 212   size_t capacity()     const { return byte_size(bottom(), end()); }
 213   virtual size_t used() const = 0;
 214   virtual size_t free() const = 0;
 215 
 216   // Iterate over all the ref-containing fields of all objects in the
 217   // space, calling "cl.do_oop" on each.  Fields in objects allocated by
 218   // applications of the closure are not included in the iteration.
 219   virtual void oop_iterate(ExtendedOopClosure* cl);
 220 
 221   // Same as above, restricted to the intersection of a memory region and
 222   // the space.  Fields in objects allocated by applications of the closure
 223   // are not included in the iteration.
 224   virtual void oop_iterate(MemRegion mr, ExtendedOopClosure* cl) = 0;
 225 
 226   // Iterate over all objects in the space, calling "cl.do_object" on
 227   // each.  Objects allocated by applications of the closure are not
 228   // included in the iteration.
 229   virtual void object_iterate(ObjectClosure* blk) = 0;
 230   // Similar to object_iterate() except only iterates over
 231   // objects whose internal references point to objects in the space.
 232   virtual void safe_object_iterate(ObjectClosure* blk) = 0;
 233 
 234   // Iterate over all objects that intersect with mr, calling "cl->do_object"
 235   // on each.  There is an exception to this: if this closure has already
 236   // been invoked on an object, it may skip such objects in some cases.  This is
 237   // Most likely to happen in an "upwards" (ascending address) iteration of
 238   // MemRegions.
 239   virtual void object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl);
 240 
 241   // Iterate over as many initialized objects in the space as possible,
 242   // calling "cl.do_object_careful" on each. Return NULL if all objects
 243   // in the space (at the start of the iteration) were iterated over.
 244   // Return an address indicating the extent of the iteration in the
 245   // event that the iteration had to return because of finding an
 246   // uninitialized object in the space, or if the closure "cl"
 247   // signalled early termination.
 248   virtual HeapWord* object_iterate_careful(ObjectClosureCareful* cl);
 249   virtual HeapWord* object_iterate_careful_m(MemRegion mr,
 250                                              ObjectClosureCareful* cl);
 251 
 252   // Create and return a new dirty card to oop closure. Can be
 253   // overriden to return the appropriate type of closure
 254   // depending on the type of space in which the closure will
 255   // operate. ResourceArea allocated.
 256   virtual DirtyCardToOopClosure* new_dcto_cl(ExtendedOopClosure* cl,
 257                                              CardTableModRefBS::PrecisionStyle precision,
 258                                              HeapWord* boundary = NULL);
 259 
 260   // If "p" is in the space, returns the address of the start of the
 261   // "block" that contains "p".  We say "block" instead of "object" since
 262   // some heaps may not pack objects densely; a chunk may either be an
 263   // object or a non-object.  If "p" is not in the space, return NULL.
 264   virtual HeapWord* block_start_const(const void* p) const = 0;
 265 
 266   // The non-const version may have benevolent side effects on the data
 267   // structure supporting these calls, possibly speeding up future calls.
 268   // The default implementation, however, is simply to call the const
 269   // version.
 270   inline virtual HeapWord* block_start(const void* p);
 271 
 272   // Requires "addr" to be the start of a chunk, and returns its size.
 273   // "addr + size" is required to be the start of a new chunk, or the end
 274   // of the active area of the heap.
 275   virtual size_t block_size(const HeapWord* addr) const = 0;
 276 
 277   // Requires "addr" to be the start of a block, and returns "TRUE" iff
 278   // the block is an object.
 279   virtual bool block_is_obj(const HeapWord* addr) const = 0;
 280 
 281   // Requires "addr" to be the start of a block, and returns "TRUE" iff
 282   // the block is an object and the object is alive.
 283   virtual bool obj_is_alive(const HeapWord* addr) const;
 284 
 285   // Allocation (return NULL if full).  Assumes the caller has established
 286   // mutually exclusive access to the space.
 287   virtual HeapWord* allocate(size_t word_size) = 0;
 288 
 289   // Allocation (return NULL if full).  Enforces mutual exclusion internally.
 290   virtual HeapWord* par_allocate(size_t word_size) = 0;
 291 
 292   // Returns true if this object has been allocated since a
 293   // generation's "save_marks" call.
 294   virtual bool obj_allocated_since_save_marks(const oop obj) const = 0;
 295 
 296   // Mark-sweep-compact support: all spaces can update pointers to objects
 297   // moving as a part of compaction.
 298   virtual void adjust_pointers();
 299 
 300   // PrintHeapAtGC support
 301   virtual void print() const;
 302   virtual void print_on(outputStream* st) const;
 303   virtual void print_short() const;
 304   virtual void print_short_on(outputStream* st) const;
 305 
 306 
 307   // Accessor for parallel sequential tasks.
 308   SequentialSubTasksDone* par_seq_tasks() { return &_par_seq_tasks; }
 309 
 310   // IF "this" is a ContiguousSpace, return it, else return NULL.
 311   virtual ContiguousSpace* toContiguousSpace() {
 312     return NULL;
 313   }
 314 
 315   // Debugging
 316   virtual void verify() const = 0;
 317 };
 318 
 319 // A MemRegionClosure (ResourceObj) whose "do_MemRegion" function applies an
 320 // OopClosure to (the addresses of) all the ref-containing fields that could
 321 // be modified by virtue of the given MemRegion being dirty. (Note that
 322 // because of the imprecise nature of the write barrier, this may iterate
 323 // over oops beyond the region.)
 324 // This base type for dirty card to oop closures handles memory regions
 325 // in non-contiguous spaces with no boundaries, and should be sub-classed
 326 // to support other space types. See ContiguousDCTOC for a sub-class
 327 // that works with ContiguousSpaces.
 328 
 329 class DirtyCardToOopClosure: public MemRegionClosureRO {
 330 protected:
 331   ExtendedOopClosure* _cl;
 332   Space* _sp;
 333   CardTableModRefBS::PrecisionStyle _precision;
 334   HeapWord* _boundary;          // If non-NULL, process only non-NULL oops
 335                                 // pointing below boundary.
 336   HeapWord* _min_done;          // ObjHeadPreciseArray precision requires
 337                                 // a downwards traversal; this is the
 338                                 // lowest location already done (or,
 339                                 // alternatively, the lowest address that
 340                                 // shouldn't be done again.  NULL means infinity.)
 341   NOT_PRODUCT(HeapWord* _last_bottom;)
 342   NOT_PRODUCT(HeapWord* _last_explicit_min_done;)
 343 
 344   // Get the actual top of the area on which the closure will
 345   // operate, given where the top is assumed to be (the end of the
 346   // memory region passed to do_MemRegion) and where the object
 347   // at the top is assumed to start. For example, an object may
 348   // start at the top but actually extend past the assumed top,
 349   // in which case the top becomes the end of the object.
 350   virtual HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj);
 351 
 352   // Walk the given memory region from bottom to (actual) top
 353   // looking for objects and applying the oop closure (_cl) to
 354   // them. The base implementation of this treats the area as
 355   // blocks, where a block may or may not be an object. Sub-
 356   // classes should override this to provide more accurate
 357   // or possibly more efficient walking.
 358   virtual void walk_mem_region(MemRegion mr, HeapWord* bottom, HeapWord* top);
 359 
 360 public:
 361   DirtyCardToOopClosure(Space* sp, ExtendedOopClosure* cl,
 362                         CardTableModRefBS::PrecisionStyle precision,
 363                         HeapWord* boundary) :
 364     _sp(sp), _cl(cl), _precision(precision), _boundary(boundary),
 365     _min_done(NULL) {
 366     NOT_PRODUCT(_last_bottom = NULL);
 367     NOT_PRODUCT(_last_explicit_min_done = NULL);
 368   }
 369 
 370   void do_MemRegion(MemRegion mr);
 371 
 372   void set_min_done(HeapWord* min_done) {
 373     _min_done = min_done;
 374     NOT_PRODUCT(_last_explicit_min_done = _min_done);
 375   }
 376 #ifndef PRODUCT
 377   void set_last_bottom(HeapWord* last_bottom) {
 378     _last_bottom = last_bottom;
 379   }
 380 #endif
 381 };
 382 
 383 // A structure to represent a point at which objects are being copied
 384 // during compaction.
 385 class CompactPoint : public StackObj {
 386 public:
 387   Generation* gen;
 388   CompactibleSpace* space;
 389   HeapWord* threshold;
 390   CompactPoint(Generation* _gen, CompactibleSpace* _space,
 391                HeapWord* _threshold) :
 392     gen(_gen), space(_space), threshold(_threshold) {}
 393 };
 394 
 395 
 396 // A space that supports compaction operations.  This is usually, but not
 397 // necessarily, a space that is normally contiguous.  But, for example, a
 398 // free-list-based space whose normal collection is a mark-sweep without
 399 // compaction could still support compaction in full GC's.
 400 
 401 class CompactibleSpace: public Space {
 402   friend class VMStructs;
 403   friend class CompactibleFreeListSpace;
 404 private:
 405   HeapWord* _compaction_top;
 406   CompactibleSpace* _next_compaction_space;
 407 
 408 public:
 409   CompactibleSpace() :
 410    _compaction_top(NULL), _next_compaction_space(NULL) {}
 411 
 412   virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
 413   virtual void clear(bool mangle_space);
 414 
 415   // Used temporarily during a compaction phase to hold the value
 416   // top should have when compaction is complete.
 417   HeapWord* compaction_top() const { return _compaction_top;    }
 418 
 419   void set_compaction_top(HeapWord* value) {
 420     assert(value == NULL || (value >= bottom() && value <= end()),
 421       "should point inside space");
 422     _compaction_top = value;
 423   }
 424 
 425   // Perform operations on the space needed after a compaction
 426   // has been performed.
 427   virtual void reset_after_compaction() {}
 428 
 429   // Returns the next space (in the current generation) to be compacted in
 430   // the global compaction order.  Also is used to select the next
 431   // space into which to compact.
 432 
 433   virtual CompactibleSpace* next_compaction_space() const {
 434     return _next_compaction_space;
 435   }
 436 
 437   void set_next_compaction_space(CompactibleSpace* csp) {
 438     _next_compaction_space = csp;
 439   }
 440 
 441   // MarkSweep support phase2
 442 
 443   // Start the process of compaction of the current space: compute
 444   // post-compaction addresses, and insert forwarding pointers.  The fields
 445   // "cp->gen" and "cp->compaction_space" are the generation and space into
 446   // which we are currently compacting.  This call updates "cp" as necessary,
 447   // and leaves the "compaction_top" of the final value of
 448   // "cp->compaction_space" up-to-date.  Offset tables may be updated in
 449   // this phase as if the final copy had occurred; if so, "cp->threshold"
 450   // indicates when the next such action should be taken.
 451   virtual void prepare_for_compaction(CompactPoint* cp);
 452   // MarkSweep support phase3
 453   virtual void adjust_pointers();
 454   // MarkSweep support phase4
 455   virtual void compact();
 456 
 457   // The maximum percentage of objects that can be dead in the compacted
 458   // live part of a compacted space ("deadwood" support.)
 459   virtual size_t allowed_dead_ratio() const { return 0; };
 460 
 461   // Some contiguous spaces may maintain some data structures that should
 462   // be updated whenever an allocation crosses a boundary.  This function
 463   // returns the first such boundary.
 464   // (The default implementation returns the end of the space, so the
 465   // boundary is never crossed.)
 466   virtual HeapWord* initialize_threshold() { return end(); }
 467 
 468   // "q" is an object of the given "size" that should be forwarded;
 469   // "cp" names the generation ("gen") and containing "this" (which must
 470   // also equal "cp->space").  "compact_top" is where in "this" the
 471   // next object should be forwarded to.  If there is room in "this" for
 472   // the object, insert an appropriate forwarding pointer in "q".
 473   // If not, go to the next compaction space (there must
 474   // be one, since compaction must succeed -- we go to the first space of
 475   // the previous generation if necessary, updating "cp"), reset compact_top
 476   // and then forward.  In either case, returns the new value of "compact_top".
 477   // If the forwarding crosses "cp->threshold", invokes the "cross_threhold"
 478   // function of the then-current compaction space, and updates "cp->threshold
 479   // accordingly".
 480   virtual HeapWord* forward(oop q, size_t size, CompactPoint* cp,
 481                     HeapWord* compact_top);
 482 
 483   // Return a size with adjusments as required of the space.
 484   virtual size_t adjust_object_size_v(size_t size) const { return size; }
 485 
 486 protected:
 487   // Used during compaction.
 488   HeapWord* _first_dead;
 489   HeapWord* _end_of_live;
 490 
 491   // Minimum size of a free block.
 492   virtual size_t minimum_free_block_size() const = 0;
 493 
 494   // This the function is invoked when an allocation of an object covering
 495   // "start" to "end occurs crosses the threshold; returns the next
 496   // threshold.  (The default implementation does nothing.)
 497   virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* the_end) {
 498     return end();
 499   }
 500 
 501   // Requires "allowed_deadspace_words > 0", that "q" is the start of a
 502   // free block of the given "word_len", and that "q", were it an object,
 503   // would not move if forwared.  If the size allows, fill the free
 504   // block with an object, to prevent excessive compaction.  Returns "true"
 505   // iff the free region was made deadspace, and modifies
 506   // "allowed_deadspace_words" to reflect the number of available deadspace
 507   // words remaining after this operation.
 508   bool insert_deadspace(size_t& allowed_deadspace_words, HeapWord* q,
 509                         size_t word_len);
 510 };
 511 
 512 #define SCAN_AND_FORWARD(cp,scan_limit,block_is_obj,block_size) {            \
 513   /* Compute the new addresses for the live objects and store it in the mark \
 514    * Used by universe::mark_sweep_phase2()                                   \
 515    */                                                                        \
 516   HeapWord* compact_top; /* This is where we are currently compacting to. */ \
 517                                                                              \
 518   /* We're sure to be here before any objects are compacted into this        \
 519    * space, so this is a good time to initialize this:                       \
 520    */                                                                        \
 521   set_compaction_top(bottom());                                              \
 522                                                                              \
 523   if (cp->space == NULL) {                                                   \
 524     assert(cp->gen != NULL, "need a generation");                            \
 525     assert(cp->threshold == NULL, "just checking");                          \
 526     assert(cp->gen->first_compaction_space() == this, "just checking");      \
 527     cp->space = cp->gen->first_compaction_space();                           \
 528     compact_top = cp->space->bottom();                                       \
 529     cp->space->set_compaction_top(compact_top);                              \
 530     cp->threshold = cp->space->initialize_threshold();                       \
 531   } else {                                                                   \
 532     compact_top = cp->space->compaction_top();                               \
 533   }                                                                          \
 534                                                                              \
 535   /* We allow some amount of garbage towards the bottom of the space, so     \
 536    * we don't start compacting before there is a significant gain to be made.\
 537    * Occasionally, we want to ensure a full compaction, which is determined  \
 538    * by the MarkSweepAlwaysCompactCount parameter.                           \
 539    */                                                                        \
 540   uint invocations = MarkSweep::total_invocations();                         \
 541   bool skip_dead = ((invocations % MarkSweepAlwaysCompactCount) != 0);       \
 542                                                                              \
 543   size_t allowed_deadspace = 0;                                              \
 544   if (skip_dead) {                                                           \
 545     const size_t ratio = allowed_dead_ratio();                               \
 546     allowed_deadspace = (capacity() * ratio / 100) / HeapWordSize;           \
 547   }                                                                          \
 548                                                                              \
 549   HeapWord* q = bottom();                                                    \
 550   HeapWord* t = scan_limit();                                                \
 551                                                                              \
 552   HeapWord*  end_of_live= q;    /* One byte beyond the last byte of the last \
 553                                    live object. */                           \
 554   HeapWord*  first_dead = end();/* The first dead object. */                 \
 555   LiveRange* liveRange  = NULL; /* The current live range, recorded in the   \
 556                                    first header of preceding free area. */   \
 557   _first_dead = first_dead;                                                  \
 558                                                                              \
 559   const intx interval = PrefetchScanIntervalInBytes;                         \
 560                                                                              \
 561   while (q < t) {                                                            \
 562     assert(!block_is_obj(q) ||                                               \
 563            oop(q)->mark()->is_marked() || oop(q)->mark()->is_unlocked() ||   \
 564            oop(q)->mark()->has_bias_pattern(),                               \
 565            "these are the only valid states during a mark sweep");           \
 566     if (block_is_obj(q) && oop(q)->is_gc_marked()) {                         \
 567       /* prefetch beyond q */                                                \
 568       Prefetch::write(q, interval);                                          \
 569       size_t size = block_size(q);                                           \
 570       compact_top = cp->space->forward(oop(q), size, cp, compact_top);       \
 571       q += size;                                                             \
 572       end_of_live = q;                                                       \
 573     } else {                                                                 \
 574       /* run over all the contiguous dead objects */                         \
 575       HeapWord* end = q;                                                     \
 576       do {                                                                   \
 577         /* prefetch beyond end */                                            \
 578         Prefetch::write(end, interval);                                      \
 579         end += block_size(end);                                              \
 580       } while (end < t && (!block_is_obj(end) || !oop(end)->is_gc_marked()));\
 581                                                                              \
 582       /* see if we might want to pretend this object is alive so that        \
 583        * we don't have to compact quite as often.                            \
 584        */                                                                    \
 585       if (allowed_deadspace > 0 && q == compact_top) {                       \
 586         size_t sz = pointer_delta(end, q);                                   \
 587         if (insert_deadspace(allowed_deadspace, q, sz)) {                    \
 588           compact_top = cp->space->forward(oop(q), sz, cp, compact_top);     \
 589           q = end;                                                           \
 590           end_of_live = end;                                                 \
 591           continue;                                                          \
 592         }                                                                    \
 593       }                                                                      \
 594                                                                              \
 595       /* otherwise, it really is a free region. */                           \
 596                                                                              \
 597       /* for the previous LiveRange, record the end of the live objects. */  \
 598       if (liveRange) {                                                       \
 599         liveRange->set_end(q);                                               \
 600       }                                                                      \
 601                                                                              \
 602       /* record the current LiveRange object.                                \
 603        * liveRange->start() is overlaid on the mark word.                    \
 604        */                                                                    \
 605       liveRange = (LiveRange*)q;                                             \
 606       liveRange->set_start(end);                                             \
 607       liveRange->set_end(end);                                               \
 608                                                                              \
 609       /* see if this is the first dead region. */                            \
 610       if (q < first_dead) {                                                  \
 611         first_dead = q;                                                      \
 612       }                                                                      \
 613                                                                              \
 614       /* move on to the next object */                                       \
 615       q = end;                                                               \
 616     }                                                                        \
 617   }                                                                          \
 618                                                                              \
 619   assert(q == t, "just checking");                                           \
 620   if (liveRange != NULL) {                                                   \
 621     liveRange->set_end(q);                                                   \
 622   }                                                                          \
 623   _end_of_live = end_of_live;                                                \
 624   if (end_of_live < first_dead) {                                            \
 625     first_dead = end_of_live;                                                \
 626   }                                                                          \
 627   _first_dead = first_dead;                                                  \
 628                                                                              \
 629   /* save the compaction_top of the compaction space. */                     \
 630   cp->space->set_compaction_top(compact_top);                                \
 631 }
 632 
 633 #define SCAN_AND_ADJUST_POINTERS(adjust_obj_size) {                             \
 634   /* adjust all the interior pointers to point at the new locations of objects  \
 635    * Used by MarkSweep::mark_sweep_phase3() */                                  \
 636                                                                                 \
 637   HeapWord* q = bottom();                                                       \
 638   HeapWord* t = _end_of_live;  /* Established by "prepare_for_compaction". */   \
 639                                                                                 \
 640   assert(_first_dead <= _end_of_live, "Stands to reason, no?");                 \
 641                                                                                 \
 642   if (q < t && _first_dead > q &&                                               \
 643       !oop(q)->is_gc_marked()) {                                                \
 644     /* we have a chunk of the space which hasn't moved and we've                \
 645      * reinitialized the mark word during the previous pass, so we can't        \
 646      * use is_gc_marked for the traversal. */                                   \
 647     HeapWord* end = _first_dead;                                                \
 648                                                                                 \
 649     while (q < end) {                                                           \
 650       /* I originally tried to conjoin "block_start(q) == q" to the             \
 651        * assertion below, but that doesn't work, because you can't              \
 652        * accurately traverse previous objects to get to the current one         \
 653        * after their pointers have been                                         \
 654        * updated, until the actual compaction is done.  dld, 4/00 */            \
 655       assert(block_is_obj(q),                                                   \
 656              "should be at block boundaries, and should be looking at objs");   \
 657                                                                                 \
 658       /* point all the oops to the new location */                              \
 659       size_t size = oop(q)->adjust_pointers();                                  \
 660       size = adjust_obj_size(size);                                             \
 661                                                                                 \
 662       q += size;                                                                \
 663     }                                                                           \
 664                                                                                 \
 665     if (_first_dead == t) {                                                     \
 666       q = t;                                                                    \
 667     } else {                                                                    \
 668       /* $$$ This is funky.  Using this to read the previously written          \
 669        * LiveRange.  See also use below. */                                     \
 670       q = (HeapWord*)oop(_first_dead)->mark()->decode_pointer();                \
 671     }                                                                           \
 672   }                                                                             \
 673                                                                                 \
 674   const intx interval = PrefetchScanIntervalInBytes;                            \
 675                                                                                 \
 676   debug_only(HeapWord* prev_q = NULL);                                          \
 677   while (q < t) {                                                               \
 678     /* prefetch beyond q */                                                     \
 679     Prefetch::write(q, interval);                                               \
 680     if (oop(q)->is_gc_marked()) {                                               \
 681       /* q is alive */                                                          \
 682       /* point all the oops to the new location */                              \
 683       size_t size = oop(q)->adjust_pointers();                                  \
 684       size = adjust_obj_size(size);                                             \
 685       debug_only(prev_q = q);                                                   \
 686       q += size;                                                                \
 687     } else {                                                                    \
 688       /* q is not a live object, so its mark should point at the next           \
 689        * live object */                                                         \
 690       debug_only(prev_q = q);                                                   \
 691       q = (HeapWord*) oop(q)->mark()->decode_pointer();                         \
 692       assert(q > prev_q, "we should be moving forward through memory");         \
 693     }                                                                           \
 694   }                                                                             \
 695                                                                                 \
 696   assert(q == t, "just checking");                                              \
 697 }
 698 
 699 #define SCAN_AND_COMPACT(obj_size) {                                            \
 700   /* Copy all live objects to their new location                                \
 701    * Used by MarkSweep::mark_sweep_phase4() */                                  \
 702                                                                                 \
 703   HeapWord*       q = bottom();                                                 \
 704   HeapWord* const t = _end_of_live;                                             \
 705   debug_only(HeapWord* prev_q = NULL);                                          \
 706                                                                                 \
 707   if (q < t && _first_dead > q &&                                               \
 708       !oop(q)->is_gc_marked()) {                                                \
 709     debug_only(                                                                 \
 710     /* we have a chunk of the space which hasn't moved and we've reinitialized  \
 711      * the mark word during the previous pass, so we can't use is_gc_marked for \
 712      * the traversal. */                                                        \
 713     HeapWord* const end = _first_dead;                                          \
 714                                                                                 \
 715     while (q < end) {                                                           \
 716       size_t size = obj_size(q);                                                \
 717       assert(!oop(q)->is_gc_marked(),                                           \
 718              "should be unmarked (special dense prefix handling)");             \
 719       debug_only(prev_q = q);                                                   \
 720       q += size;                                                                \
 721     }                                                                           \
 722     )  /* debug_only */                                                         \
 723                                                                                 \
 724     if (_first_dead == t) {                                                     \
 725       q = t;                                                                    \
 726     } else {                                                                    \
 727       /* $$$ Funky */                                                           \
 728       q = (HeapWord*) oop(_first_dead)->mark()->decode_pointer();               \
 729     }                                                                           \
 730   }                                                                             \
 731                                                                                 \
 732   const intx scan_interval = PrefetchScanIntervalInBytes;                       \
 733   const intx copy_interval = PrefetchCopyIntervalInBytes;                       \
 734   while (q < t) {                                                               \
 735     if (!oop(q)->is_gc_marked()) {                                              \
 736       /* mark is pointer to next marked oop */                                  \
 737       debug_only(prev_q = q);                                                   \
 738       q = (HeapWord*) oop(q)->mark()->decode_pointer();                         \
 739       assert(q > prev_q, "we should be moving forward through memory");         \
 740     } else {                                                                    \
 741       /* prefetch beyond q */                                                   \
 742       Prefetch::read(q, scan_interval);                                         \
 743                                                                                 \
 744       /* size and destination */                                                \
 745       size_t size = obj_size(q);                                                \
 746       HeapWord* compaction_top = (HeapWord*)oop(q)->forwardee();                \
 747                                                                                 \
 748       /* prefetch beyond compaction_top */                                      \
 749       Prefetch::write(compaction_top, copy_interval);                           \
 750                                                                                 \
 751       /* copy object and reinit its mark */                                     \
 752       assert(q != compaction_top, "everything in this pass should be moving");  \
 753       Copy::aligned_conjoint_words(q, compaction_top, size);                    \
 754       oop(compaction_top)->init_mark();                                         \
 755       assert(oop(compaction_top)->klass() != NULL, "should have a class");      \
 756                                                                                 \
 757       debug_only(prev_q = q);                                                   \
 758       q += size;                                                                \
 759     }                                                                           \
 760   }                                                                             \
 761                                                                                 \
 762   /* Let's remember if we were empty before we did the compaction. */           \
 763   bool was_empty = used_region().is_empty();                                    \
 764   /* Reset space after compaction is complete */                                \
 765   reset_after_compaction();                                                     \
 766   /* We do this clear, below, since it has overloaded meanings for some */      \
 767   /* space subtypes.  For example, OffsetTableContigSpace's that were   */      \
 768   /* compacted into will have had their offset table thresholds updated */      \
 769   /* continuously, but those that weren't need to have their thresholds */      \
 770   /* re-initialized.  Also mangles unused area for debugging.           */      \
 771   if (used_region().is_empty()) {                                               \
 772     if (!was_empty) clear(SpaceDecorator::Mangle);                              \
 773   } else {                                                                      \
 774     if (ZapUnusedHeapArea) mangle_unused_area();                                \
 775   }                                                                             \
 776 }
 777 
 778 class GenSpaceMangler;
 779 
 780 // A space in which the free area is contiguous.  It therefore supports
 781 // faster allocation, and compaction.
 782 class ContiguousSpace: public CompactibleSpace {
 783   friend class OneContigSpaceCardGeneration;
 784   friend class VMStructs;
 785  protected:
 786   HeapWord* _top;
 787   HeapWord* _concurrent_iteration_safe_limit;
 788   // A helper for mangling the unused area of the space in debug builds.
 789   GenSpaceMangler* _mangler;
 790 
 791   GenSpaceMangler* mangler() { return _mangler; }
 792 
 793   // Allocation helpers (return NULL if full).
 794   inline HeapWord* allocate_impl(size_t word_size, HeapWord* end_value);
 795   inline HeapWord* par_allocate_impl(size_t word_size, HeapWord* end_value);
 796 
 797  public:
 798   ContiguousSpace();
 799   ~ContiguousSpace();
 800 
 801   virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
 802   virtual void clear(bool mangle_space);
 803 
 804   // Accessors
 805   HeapWord* top() const            { return _top;    }
 806   void set_top(HeapWord* value)    { _top = value; }
 807 
 808   virtual void set_saved_mark()    { _saved_mark_word = top();    }
 809   void reset_saved_mark()          { _saved_mark_word = bottom(); }
 810 
 811   WaterMark bottom_mark()     { return WaterMark(this, bottom()); }
 812   WaterMark top_mark()        { return WaterMark(this, top()); }
 813   WaterMark saved_mark()      { return WaterMark(this, saved_mark_word()); }
 814   bool saved_mark_at_top() const { return saved_mark_word() == top(); }
 815 
 816   // In debug mode mangle (write it with a particular bit
 817   // pattern) the unused part of a space.
 818 
 819   // Used to save the an address in a space for later use during mangling.
 820   void set_top_for_allocations(HeapWord* v) PRODUCT_RETURN;
 821   // Used to save the space's current top for later use during mangling.
 822   void set_top_for_allocations() PRODUCT_RETURN;
 823 
 824   // Mangle regions in the space from the current top up to the
 825   // previously mangled part of the space.
 826   void mangle_unused_area() PRODUCT_RETURN;
 827   // Mangle [top, end)
 828   void mangle_unused_area_complete() PRODUCT_RETURN;
 829   // Mangle the given MemRegion.
 830   void mangle_region(MemRegion mr) PRODUCT_RETURN;
 831 
 832   // Do some sparse checking on the area that should have been mangled.
 833   void check_mangled_unused_area(HeapWord* limit) PRODUCT_RETURN;
 834   // Check the complete area that should have been mangled.
 835   // This code may be NULL depending on the macro DEBUG_MANGLING.
 836   void check_mangled_unused_area_complete() PRODUCT_RETURN;
 837 
 838   // Size computations: sizes in bytes.
 839   size_t capacity() const        { return byte_size(bottom(), end()); }
 840   size_t used() const            { return byte_size(bottom(), top()); }
 841   size_t free() const            { return byte_size(top(),    end()); }
 842 
 843   // Override from space.
 844   bool is_in(const void* p) const;
 845 
 846   virtual bool is_free_block(const HeapWord* p) const;
 847 
 848   // In a contiguous space we have a more obvious bound on what parts
 849   // contain objects.
 850   MemRegion used_region() const { return MemRegion(bottom(), top()); }
 851 
 852   MemRegion used_region_at_save_marks() const {
 853     return MemRegion(bottom(), saved_mark_word());
 854   }
 855 
 856   // Allocation (return NULL if full)
 857   virtual HeapWord* allocate(size_t word_size);
 858   virtual HeapWord* par_allocate(size_t word_size);
 859 
 860   virtual bool obj_allocated_since_save_marks(const oop obj) const {
 861     return (HeapWord*)obj >= saved_mark_word();
 862   }
 863 
 864   // Iteration
 865   void oop_iterate(ExtendedOopClosure* cl);
 866   void oop_iterate(MemRegion mr, ExtendedOopClosure* cl);
 867   void object_iterate(ObjectClosure* blk);
 868   // For contiguous spaces this method will iterate safely over objects
 869   // in the space (i.e., between bottom and top) when at a safepoint.
 870   void safe_object_iterate(ObjectClosure* blk);
 871   void object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl);
 872   // iterates on objects up to the safe limit
 873   HeapWord* object_iterate_careful(ObjectClosureCareful* cl);
 874   HeapWord* concurrent_iteration_safe_limit() {
 875     assert(_concurrent_iteration_safe_limit <= top(),
 876            "_concurrent_iteration_safe_limit update missed");
 877     return _concurrent_iteration_safe_limit;
 878   }
 879   // changes the safe limit, all objects from bottom() to the new
 880   // limit should be properly initialized
 881   void set_concurrent_iteration_safe_limit(HeapWord* new_limit) {
 882     assert(new_limit <= top(), "uninitialized objects in the safe range");
 883     _concurrent_iteration_safe_limit = new_limit;
 884   }
 885 
 886 
 887 #if INCLUDE_ALL_GCS
 888   // In support of parallel oop_iterate.
 889   #define ContigSpace_PAR_OOP_ITERATE_DECL(OopClosureType, nv_suffix)  \
 890     void par_oop_iterate(MemRegion mr, OopClosureType* blk);
 891 
 892     ALL_PAR_OOP_ITERATE_CLOSURES(ContigSpace_PAR_OOP_ITERATE_DECL)
 893   #undef ContigSpace_PAR_OOP_ITERATE_DECL
 894 #endif // INCLUDE_ALL_GCS
 895 
 896   // Compaction support
 897   virtual void reset_after_compaction() {
 898     assert(compaction_top() >= bottom() && compaction_top() <= end(), "should point inside space");
 899     set_top(compaction_top());
 900     // set new iteration safe limit
 901     set_concurrent_iteration_safe_limit(compaction_top());
 902   }
 903   virtual size_t minimum_free_block_size() const { return 0; }
 904 
 905   // Override.
 906   DirtyCardToOopClosure* new_dcto_cl(ExtendedOopClosure* cl,
 907                                      CardTableModRefBS::PrecisionStyle precision,
 908                                      HeapWord* boundary = NULL);
 909 
 910   // Apply "blk->do_oop" to the addresses of all reference fields in objects
 911   // starting with the _saved_mark_word, which was noted during a generation's
 912   // save_marks and is required to denote the head of an object.
 913   // Fields in objects allocated by applications of the closure
 914   // *are* included in the iteration.
 915   // Updates _saved_mark_word to point to just after the last object
 916   // iterated over.
 917 #define ContigSpace_OOP_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix)  \
 918   void oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk);
 919 
 920   ALL_SINCE_SAVE_MARKS_CLOSURES(ContigSpace_OOP_SINCE_SAVE_MARKS_DECL)
 921 #undef ContigSpace_OOP_SINCE_SAVE_MARKS_DECL
 922 
 923   // Same as object_iterate, but starting from "mark", which is required
 924   // to denote the start of an object.  Objects allocated by
 925   // applications of the closure *are* included in the iteration.
 926   virtual void object_iterate_from(WaterMark mark, ObjectClosure* blk);
 927 
 928   // Very inefficient implementation.
 929   virtual HeapWord* block_start_const(const void* p) const;
 930   size_t block_size(const HeapWord* p) const;
 931   // If a block is in the allocated area, it is an object.
 932   bool block_is_obj(const HeapWord* p) const { return p < top(); }
 933 
 934   // Addresses for inlined allocation
 935   HeapWord** top_addr() { return &_top; }
 936   HeapWord** end_addr() { return &_end; }
 937 
 938   // Overrides for more efficient compaction support.
 939   void prepare_for_compaction(CompactPoint* cp);
 940 
 941   // PrintHeapAtGC support.
 942   virtual void print_on(outputStream* st) const;
 943 
 944   // Checked dynamic downcasts.
 945   virtual ContiguousSpace* toContiguousSpace() {
 946     return this;
 947   }
 948 
 949   // Debugging
 950   virtual void verify() const;
 951 
 952   // Used to increase collection frequency.  "factor" of 0 means entire
 953   // space.
 954   void allocate_temporary_filler(int factor);
 955 
 956 };
 957 
 958 
 959 // A dirty card to oop closure that does filtering.
 960 // It knows how to filter out objects that are outside of the _boundary.
 961 class Filtering_DCTOC : public DirtyCardToOopClosure {
 962 protected:
 963   // Override.
 964   void walk_mem_region(MemRegion mr,
 965                        HeapWord* bottom, HeapWord* top);
 966 
 967   // Walk the given memory region, from bottom to top, applying
 968   // the given oop closure to (possibly) all objects found. The
 969   // given oop closure may or may not be the same as the oop
 970   // closure with which this closure was created, as it may
 971   // be a filtering closure which makes use of the _boundary.
 972   // We offer two signatures, so the FilteringClosure static type is
 973   // apparent.
 974   virtual void walk_mem_region_with_cl(MemRegion mr,
 975                                        HeapWord* bottom, HeapWord* top,
 976                                        ExtendedOopClosure* cl) = 0;
 977   virtual void walk_mem_region_with_cl(MemRegion mr,
 978                                        HeapWord* bottom, HeapWord* top,
 979                                        FilteringClosure* cl) = 0;
 980 
 981 public:
 982   Filtering_DCTOC(Space* sp, ExtendedOopClosure* cl,
 983                   CardTableModRefBS::PrecisionStyle precision,
 984                   HeapWord* boundary) :
 985     DirtyCardToOopClosure(sp, cl, precision, boundary) {}
 986 };
 987 
 988 // A dirty card to oop closure for contiguous spaces
 989 // (ContiguousSpace and sub-classes).
 990 // It is a FilteringClosure, as defined above, and it knows:
 991 //
 992 // 1. That the actual top of any area in a memory region
 993 //    contained by the space is bounded by the end of the contiguous
 994 //    region of the space.
 995 // 2. That the space is really made up of objects and not just
 996 //    blocks.
 997 
 998 class ContiguousSpaceDCTOC : public Filtering_DCTOC {
 999 protected:
1000   // Overrides.
1001   HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj);
1002 
1003   virtual void walk_mem_region_with_cl(MemRegion mr,
1004                                        HeapWord* bottom, HeapWord* top,
1005                                        ExtendedOopClosure* cl);
1006   virtual void walk_mem_region_with_cl(MemRegion mr,
1007                                        HeapWord* bottom, HeapWord* top,
1008                                        FilteringClosure* cl);
1009 
1010 public:
1011   ContiguousSpaceDCTOC(ContiguousSpace* sp, ExtendedOopClosure* cl,
1012                        CardTableModRefBS::PrecisionStyle precision,
1013                        HeapWord* boundary) :
1014     Filtering_DCTOC(sp, cl, precision, boundary)
1015   {}
1016 };
1017 
1018 
1019 // Class EdenSpace describes eden-space in new generation.
1020 
1021 class DefNewGeneration;
1022 
1023 class EdenSpace : public ContiguousSpace {
1024   friend class VMStructs;
1025  private:
1026   DefNewGeneration* _gen;
1027 
1028   // _soft_end is used as a soft limit on allocation.  As soft limits are
1029   // reached, the slow-path allocation code can invoke other actions and then
1030   // adjust _soft_end up to a new soft limit or to end().
1031   HeapWord* _soft_end;
1032 
1033  public:
1034   EdenSpace(DefNewGeneration* gen) :
1035    _gen(gen), _soft_end(NULL) {}
1036 
1037   // Get/set just the 'soft' limit.
1038   HeapWord* soft_end()               { return _soft_end; }
1039   HeapWord** soft_end_addr()         { return &_soft_end; }
1040   void set_soft_end(HeapWord* value) { _soft_end = value; }
1041 
1042   // Override.
1043   void clear(bool mangle_space);
1044 
1045   // Set both the 'hard' and 'soft' limits (_end and _soft_end).
1046   void set_end(HeapWord* value) {
1047     set_soft_end(value);
1048     ContiguousSpace::set_end(value);
1049   }
1050 
1051   // Allocation (return NULL if full)
1052   HeapWord* allocate(size_t word_size);
1053   HeapWord* par_allocate(size_t word_size);
1054 };
1055 
1056 // Class ConcEdenSpace extends EdenSpace for the sake of safe
1057 // allocation while soft-end is being modified concurrently
1058 
1059 class ConcEdenSpace : public EdenSpace {
1060  public:
1061   ConcEdenSpace(DefNewGeneration* gen) : EdenSpace(gen) { }
1062 
1063   // Allocation (return NULL if full)
1064   HeapWord* par_allocate(size_t word_size);
1065 };
1066 
1067 
1068 // A ContigSpace that Supports an efficient "block_start" operation via
1069 // a BlockOffsetArray (whose BlockOffsetSharedArray may be shared with
1070 // other spaces.)  This is the abstract base class for old generation
1071 // (tenured) spaces.
1072 
1073 class OffsetTableContigSpace: public ContiguousSpace {
1074   friend class VMStructs;
1075  protected:
1076   BlockOffsetArrayContigSpace _offsets;
1077   Mutex _par_alloc_lock;
1078 
1079  public:
1080   // Constructor
1081   OffsetTableContigSpace(BlockOffsetSharedArray* sharedOffsetArray,
1082                          MemRegion mr);
1083 
1084   void set_bottom(HeapWord* value);
1085   void set_end(HeapWord* value);
1086 
1087   void clear(bool mangle_space);
1088 
1089   inline HeapWord* block_start_const(const void* p) const;
1090 
1091   // Add offset table update.
1092   virtual inline HeapWord* allocate(size_t word_size);
1093   inline HeapWord* par_allocate(size_t word_size);
1094 
1095   // MarkSweep support phase3
1096   virtual HeapWord* initialize_threshold();
1097   virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* end);
1098 
1099   virtual void print_on(outputStream* st) const;
1100 
1101   // Debugging
1102   void verify() const;
1103 };
1104 
1105 
1106 // Class TenuredSpace is used by TenuredGeneration
1107 
1108 class TenuredSpace: public OffsetTableContigSpace {
1109   friend class VMStructs;
1110  protected:
1111   // Mark sweep support
1112   size_t allowed_dead_ratio() const;
1113  public:
1114   // Constructor
1115   TenuredSpace(BlockOffsetSharedArray* sharedOffsetArray,
1116                MemRegion mr) :
1117     OffsetTableContigSpace(sharedOffsetArray, mr) {}
1118 };
1119 #endif // SHARE_VM_MEMORY_SPACE_HPP