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/workgroup.hpp"
  38 #ifdef TARGET_OS_FAMILY_linux
  39 # include "os_linux.inline.hpp"
  40 #endif
  41 #ifdef TARGET_OS_FAMILY_solaris
  42 # include "os_solaris.inline.hpp"
  43 #endif
  44 #ifdef TARGET_OS_FAMILY_windows
  45 # include "os_windows.inline.hpp"
  46 #endif
  47 #ifdef TARGET_OS_FAMILY_bsd
  48 # include "os_bsd.inline.hpp"
  49 #endif
  50 
  51 // A space is an abstraction for the "storage units" backing
  52 // up the generation abstraction. It includes specific
  53 // implementations for keeping track of free and used space,
  54 // for iterating over objects and free blocks, etc.
  55 
  56 // Here's the Space hierarchy:
  57 //
  58 // - Space               -- an asbtract base class describing a heap area
  59 //   - CompactibleSpace  -- a space supporting compaction
  60 //     - CompactibleFreeListSpace -- (used for CMS generation)
  61 //     - ContiguousSpace -- a compactible space in which all free space
  62 //                          is contiguous
  63 //       - EdenSpace     -- contiguous space used as nursery
  64 //         - ConcEdenSpace -- contiguous space with a 'soft end safe' allocation
  65 //       - OffsetTableContigSpace -- contiguous space with a block offset array
  66 //                          that allows "fast" block_start calls
  67 //         - TenuredSpace -- (used for TenuredGeneration)
  68 //         - ContigPermSpace -- an offset table contiguous space for perm gen
  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 OopClosure {
  83  private:
  84   OopClosure* _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(OopClosure* cl, MemRegion mr):
  94     _cl(cl), _mr(mr) {}
  95   virtual void do_oop(oop* p);
  96   virtual void do_oop(narrowOop* p);
  97 };
  98 
  99 // A Space describes a heap area. Class Space is an abstract
 100 // base class.
 101 //
 102 // Space supports allocation, size computation and GC support is provided.
 103 //
 104 // Invariant: bottom() and end() are on page_size boundaries and
 105 // bottom() <= top() <= end()
 106 // top() is inclusive and end() is exclusive.
 107 
 108 class Space: public CHeapObj {
 109   friend class VMStructs;
 110  protected:
 111   HeapWord* _bottom;
 112   HeapWord* _end;
 113 
 114   // Used in support of save_marks()
 115   HeapWord* _saved_mark_word;
 116 
 117   MemRegionClosure* _preconsumptionDirtyCardClosure;
 118 
 119   // A sequential tasks done structure. This supports
 120   // parallel GC, where we have threads dynamically
 121   // claiming sub-tasks from a larger parallel task.
 122   SequentialSubTasksDone _par_seq_tasks;
 123 
 124   Space():
 125     _bottom(NULL), _end(NULL), _preconsumptionDirtyCardClosure(NULL) { }
 126 
 127  public:
 128   // Accessors
 129   HeapWord* bottom() const         { return _bottom; }
 130   HeapWord* end() const            { return _end;    }
 131   virtual void set_bottom(HeapWord* value) { _bottom = value; }
 132   virtual void set_end(HeapWord* value)    { _end = value; }
 133 
 134   virtual HeapWord* saved_mark_word() const  { return _saved_mark_word; }
 135 
 136   void set_saved_mark_word(HeapWord* p) { _saved_mark_word = p; }
 137 
 138   MemRegionClosure* preconsumptionDirtyCardClosure() const {
 139     return _preconsumptionDirtyCardClosure;
 140   }
 141   void setPreconsumptionDirtyCardClosure(MemRegionClosure* cl) {
 142     _preconsumptionDirtyCardClosure = cl;
 143   }
 144 
 145   // Returns a subregion of the space containing all the objects in
 146   // the space.
 147   virtual MemRegion used_region() const { return MemRegion(bottom(), end()); }
 148 
 149   // Returns a region that is guaranteed to contain (at least) all objects
 150   // allocated at the time of the last call to "save_marks".  If the space
 151   // initializes its DirtyCardToOopClosure's specifying the "contig" option
 152   // (that is, if the space is contiguous), then this region must contain only
 153   // such objects: the memregion will be from the bottom of the region to the
 154   // saved mark.  Otherwise, the "obj_allocated_since_save_marks" method of
 155   // the space must distiguish between objects in the region allocated before
 156   // and after the call to save marks.
 157   virtual MemRegion used_region_at_save_marks() const {
 158     return MemRegion(bottom(), saved_mark_word());
 159   }
 160 
 161   // Initialization.
 162   // "initialize" should be called once on a space, before it is used for
 163   // any purpose.  The "mr" arguments gives the bounds of the space, and
 164   // the "clear_space" argument should be true unless the memory in "mr" is
 165   // known to be zeroed.
 166   virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
 167 
 168   // The "clear" method must be called on a region that may have
 169   // had allocation performed in it, but is now to be considered empty.
 170   virtual void clear(bool mangle_space);
 171 
 172   // For detecting GC bugs.  Should only be called at GC boundaries, since
 173   // some unused space may be used as scratch space during GC's.
 174   // Default implementation does nothing. We also call this when expanding
 175   // a space to satisfy an allocation request. See bug #4668531
 176   virtual void mangle_unused_area() {}
 177   virtual void mangle_unused_area_complete() {}
 178   virtual void mangle_region(MemRegion mr) {}
 179 
 180   // Testers
 181   bool is_empty() const              { return used() == 0; }
 182   bool not_empty() const             { return used() > 0; }
 183 
 184   // Returns true iff the given the space contains the
 185   // given address as part of an allocated object. For
 186   // ceratin kinds of spaces, this might be a potentially
 187   // expensive operation. To prevent performance problems
 188   // on account of its inadvertent use in product jvm's,
 189   // we restrict its use to assertion checks only.
 190   virtual bool is_in(const void* p) const = 0;
 191 
 192   // Returns true iff the given reserved memory of the space contains the
 193   // given address.
 194   bool is_in_reserved(const void* p) const { return _bottom <= p && p < _end; }
 195 
 196   // Returns true iff the given block is not allocated.
 197   virtual bool is_free_block(const HeapWord* p) const = 0;
 198 
 199   // Test whether p is double-aligned
 200   static bool is_aligned(void* p) {
 201     return ((intptr_t)p & (sizeof(double)-1)) == 0;
 202   }
 203 
 204   // Size computations.  Sizes are in bytes.
 205   size_t capacity()     const { return byte_size(bottom(), end()); }
 206   virtual size_t used() const = 0;
 207   virtual size_t free() const = 0;
 208 
 209   // Iterate over all the ref-containing fields of all objects in the
 210   // space, calling "cl.do_oop" on each.  Fields in objects allocated by
 211   // applications of the closure are not included in the iteration.
 212   virtual void oop_iterate(OopClosure* cl);
 213 
 214   // Same as above, restricted to the intersection of a memory region and
 215   // the space.  Fields in objects allocated by applications of the closure
 216   // are not included in the iteration.
 217   virtual void oop_iterate(MemRegion mr, OopClosure* cl) = 0;
 218 
 219   // Iterate over all objects in the space, calling "cl.do_object" on
 220   // each.  Objects allocated by applications of the closure are not
 221   // included in the iteration.
 222   virtual void object_iterate(ObjectClosure* blk) = 0;
 223   // Similar to object_iterate() except only iterates over
 224   // objects whose internal references point to objects in the space.
 225   virtual void safe_object_iterate(ObjectClosure* blk) = 0;
 226 
 227   // Iterate over all objects that intersect with mr, calling "cl->do_object"
 228   // on each.  There is an exception to this: if this closure has already
 229   // been invoked on an object, it may skip such objects in some cases.  This is
 230   // Most likely to happen in an "upwards" (ascending address) iteration of
 231   // MemRegions.
 232   virtual void object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl);
 233 
 234   // Iterate over as many initialized objects in the space as possible,
 235   // calling "cl.do_object_careful" on each. Return NULL if all objects
 236   // in the space (at the start of the iteration) were iterated over.
 237   // Return an address indicating the extent of the iteration in the
 238   // event that the iteration had to return because of finding an
 239   // uninitialized object in the space, or if the closure "cl"
 240   // signalled early termination.
 241   virtual HeapWord* object_iterate_careful(ObjectClosureCareful* cl);
 242   virtual HeapWord* object_iterate_careful_m(MemRegion mr,
 243                                              ObjectClosureCareful* cl);
 244 
 245   // Create and return a new dirty card to oop closure. Can be
 246   // overriden to return the appropriate type of closure
 247   // depending on the type of space in which the closure will
 248   // operate. ResourceArea allocated.
 249   virtual DirtyCardToOopClosure* new_dcto_cl(OopClosure* cl,
 250                                              CardTableModRefBS::PrecisionStyle precision,
 251                                              HeapWord* boundary = NULL);
 252 
 253   // If "p" is in the space, returns the address of the start of the
 254   // "block" that contains "p".  We say "block" instead of "object" since
 255   // some heaps may not pack objects densely; a chunk may either be an
 256   // object or a non-object.  If "p" is not in the space, return NULL.
 257   virtual HeapWord* block_start_const(const void* p) const = 0;
 258 
 259   // The non-const version may have benevolent side effects on the data
 260   // structure supporting these calls, possibly speeding up future calls.
 261   // The default implementation, however, is simply to call the const
 262   // version.
 263   inline virtual HeapWord* block_start(const void* p);
 264 
 265   // Requires "addr" to be the start of a chunk, and returns its size.
 266   // "addr + size" is required to be the start of a new chunk, or the end
 267   // of the active area of the heap.
 268   virtual size_t block_size(const HeapWord* addr) const = 0;
 269 
 270   // Requires "addr" to be the start of a block, and returns "TRUE" iff
 271   // the block is an object.
 272   virtual bool block_is_obj(const HeapWord* addr) const = 0;
 273 
 274   // Requires "addr" to be the start of a block, and returns "TRUE" iff
 275   // the block is an object and the object is alive.
 276   virtual bool obj_is_alive(const HeapWord* addr) const;
 277 
 278   // Allocation (return NULL if full).  Assumes the caller has established
 279   // mutually exclusive access to the space.
 280   virtual HeapWord* allocate(size_t word_size) = 0;
 281 
 282   // Allocation (return NULL if full).  Enforces mutual exclusion internally.
 283   virtual HeapWord* par_allocate(size_t word_size) = 0;
 284 
 285   // Returns true if this object has been allocated since a
 286   // generation's "save_marks" call.
 287   virtual bool obj_allocated_since_save_marks(const oop obj) const = 0;
 288 
 289   // Mark-sweep-compact support: all spaces can update pointers to objects
 290   // moving as a part of compaction.
 291   virtual void adjust_pointers();
 292 
 293   // PrintHeapAtGC support
 294   virtual void print() const;
 295   virtual void print_on(outputStream* st) const;
 296   virtual void print_short() const;
 297   virtual void print_short_on(outputStream* st) const;
 298 
 299 
 300   // Accessor for parallel sequential tasks.
 301   SequentialSubTasksDone* par_seq_tasks() { return &_par_seq_tasks; }
 302 
 303   // IF "this" is a ContiguousSpace, return it, else return NULL.
 304   virtual ContiguousSpace* toContiguousSpace() {
 305     return NULL;
 306   }
 307 
 308   // Debugging
 309   virtual void verify() const = 0;
 310 };
 311 
 312 // A MemRegionClosure (ResourceObj) whose "do_MemRegion" function applies an
 313 // OopClosure to (the addresses of) all the ref-containing fields that could
 314 // be modified by virtue of the given MemRegion being dirty. (Note that
 315 // because of the imprecise nature of the write barrier, this may iterate
 316 // over oops beyond the region.)
 317 // This base type for dirty card to oop closures handles memory regions
 318 // in non-contiguous spaces with no boundaries, and should be sub-classed
 319 // to support other space types. See ContiguousDCTOC for a sub-class
 320 // that works with ContiguousSpaces.
 321 
 322 class DirtyCardToOopClosure: public MemRegionClosureRO {
 323 protected:
 324   OopClosure* _cl;
 325   Space* _sp;
 326   CardTableModRefBS::PrecisionStyle _precision;
 327   HeapWord* _boundary;          // If non-NULL, process only non-NULL oops
 328                                 // pointing below boundary.
 329   HeapWord* _min_done;          // ObjHeadPreciseArray precision requires
 330                                 // a downwards traversal; this is the
 331                                 // lowest location already done (or,
 332                                 // alternatively, the lowest address that
 333                                 // shouldn't be done again.  NULL means infinity.)
 334   NOT_PRODUCT(HeapWord* _last_bottom;)
 335   NOT_PRODUCT(HeapWord* _last_explicit_min_done;)
 336 
 337   // Get the actual top of the area on which the closure will
 338   // operate, given where the top is assumed to be (the end of the
 339   // memory region passed to do_MemRegion) and where the object
 340   // at the top is assumed to start. For example, an object may
 341   // start at the top but actually extend past the assumed top,
 342   // in which case the top becomes the end of the object.
 343   virtual HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj);
 344 
 345   // Walk the given memory region from bottom to (actual) top
 346   // looking for objects and applying the oop closure (_cl) to
 347   // them. The base implementation of this treats the area as
 348   // blocks, where a block may or may not be an object. Sub-
 349   // classes should override this to provide more accurate
 350   // or possibly more efficient walking.
 351   virtual void walk_mem_region(MemRegion mr, HeapWord* bottom, HeapWord* top);
 352 
 353 public:
 354   DirtyCardToOopClosure(Space* sp, OopClosure* cl,
 355                         CardTableModRefBS::PrecisionStyle precision,
 356                         HeapWord* boundary) :
 357     _sp(sp), _cl(cl), _precision(precision), _boundary(boundary),
 358     _min_done(NULL) {
 359     NOT_PRODUCT(_last_bottom = NULL);
 360     NOT_PRODUCT(_last_explicit_min_done = NULL);
 361   }
 362 
 363   void do_MemRegion(MemRegion mr);
 364 
 365   void set_min_done(HeapWord* min_done) {
 366     _min_done = min_done;
 367     NOT_PRODUCT(_last_explicit_min_done = _min_done);
 368   }
 369 #ifndef PRODUCT
 370   void set_last_bottom(HeapWord* last_bottom) {
 371     _last_bottom = last_bottom;
 372   }
 373 #endif
 374 };
 375 
 376 // A structure to represent a point at which objects are being copied
 377 // during compaction.
 378 class CompactPoint : public StackObj {
 379 public:
 380   Generation* gen;
 381   CompactibleSpace* space;
 382   HeapWord* threshold;
 383   CompactPoint(Generation* _gen, CompactibleSpace* _space,
 384                HeapWord* _threshold) :
 385     gen(_gen), space(_space), threshold(_threshold) {}
 386 };
 387 
 388 
 389 // A space that supports compaction operations.  This is usually, but not
 390 // necessarily, a space that is normally contiguous.  But, for example, a
 391 // free-list-based space whose normal collection is a mark-sweep without
 392 // compaction could still support compaction in full GC's.
 393 
 394 class CompactibleSpace: public Space {
 395   friend class VMStructs;
 396   friend class CompactibleFreeListSpace;
 397   friend class CompactingPermGenGen;
 398   friend class CMSPermGenGen;
 399 private:
 400   HeapWord* _compaction_top;
 401   CompactibleSpace* _next_compaction_space;
 402 
 403 public:
 404   CompactibleSpace() :
 405    _compaction_top(NULL), _next_compaction_space(NULL) {}
 406 
 407   virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
 408   virtual void clear(bool mangle_space);
 409 
 410   // Used temporarily during a compaction phase to hold the value
 411   // top should have when compaction is complete.
 412   HeapWord* compaction_top() const { return _compaction_top;    }
 413 
 414   void set_compaction_top(HeapWord* value) {
 415     assert(value == NULL || (value >= bottom() && value <= end()),
 416       "should point inside space");
 417     _compaction_top = value;
 418   }
 419 
 420   // Perform operations on the space needed after a compaction
 421   // has been performed.
 422   virtual void reset_after_compaction() {}
 423 
 424   // Returns the next space (in the current generation) to be compacted in
 425   // the global compaction order.  Also is used to select the next
 426   // space into which to compact.
 427 
 428   virtual CompactibleSpace* next_compaction_space() const {
 429     return _next_compaction_space;
 430   }
 431 
 432   void set_next_compaction_space(CompactibleSpace* csp) {
 433     _next_compaction_space = csp;
 434   }
 435 
 436   // MarkSweep support phase2
 437 
 438   // Start the process of compaction of the current space: compute
 439   // post-compaction addresses, and insert forwarding pointers.  The fields
 440   // "cp->gen" and "cp->compaction_space" are the generation and space into
 441   // which we are currently compacting.  This call updates "cp" as necessary,
 442   // and leaves the "compaction_top" of the final value of
 443   // "cp->compaction_space" up-to-date.  Offset tables may be updated in
 444   // this phase as if the final copy had occurred; if so, "cp->threshold"
 445   // indicates when the next such action should be taken.
 446   virtual void prepare_for_compaction(CompactPoint* cp);
 447   // MarkSweep support phase3
 448   virtual void adjust_pointers();
 449   // MarkSweep support phase4
 450   virtual void compact();
 451 
 452   // The maximum percentage of objects that can be dead in the compacted
 453   // live part of a compacted space ("deadwood" support.)
 454   virtual size_t allowed_dead_ratio() const { return 0; };
 455 
 456   // Some contiguous spaces may maintain some data structures that should
 457   // be updated whenever an allocation crosses a boundary.  This function
 458   // returns the first such boundary.
 459   // (The default implementation returns the end of the space, so the
 460   // boundary is never crossed.)
 461   virtual HeapWord* initialize_threshold() { return end(); }
 462 
 463   // "q" is an object of the given "size" that should be forwarded;
 464   // "cp" names the generation ("gen") and containing "this" (which must
 465   // also equal "cp->space").  "compact_top" is where in "this" the
 466   // next object should be forwarded to.  If there is room in "this" for
 467   // the object, insert an appropriate forwarding pointer in "q".
 468   // If not, go to the next compaction space (there must
 469   // be one, since compaction must succeed -- we go to the first space of
 470   // the previous generation if necessary, updating "cp"), reset compact_top
 471   // and then forward.  In either case, returns the new value of "compact_top".
 472   // If the forwarding crosses "cp->threshold", invokes the "cross_threhold"
 473   // function of the then-current compaction space, and updates "cp->threshold
 474   // accordingly".
 475   virtual HeapWord* forward(oop q, size_t size, CompactPoint* cp,
 476                     HeapWord* compact_top);
 477 
 478   // Return a size with adjusments as required of the space.
 479   virtual size_t adjust_object_size_v(size_t size) const { return size; }
 480 
 481 protected:
 482   // Used during compaction.
 483   HeapWord* _first_dead;
 484   HeapWord* _end_of_live;
 485 
 486   // Minimum size of a free block.
 487   virtual size_t minimum_free_block_size() const = 0;
 488 
 489   // This the function is invoked when an allocation of an object covering
 490   // "start" to "end occurs crosses the threshold; returns the next
 491   // threshold.  (The default implementation does nothing.)
 492   virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* the_end) {
 493     return end();
 494   }
 495 
 496   // Requires "allowed_deadspace_words > 0", that "q" is the start of a
 497   // free block of the given "word_len", and that "q", were it an object,
 498   // would not move if forwared.  If the size allows, fill the free
 499   // block with an object, to prevent excessive compaction.  Returns "true"
 500   // iff the free region was made deadspace, and modifies
 501   // "allowed_deadspace_words" to reflect the number of available deadspace
 502   // words remaining after this operation.
 503   bool insert_deadspace(size_t& allowed_deadspace_words, HeapWord* q,
 504                         size_t word_len);
 505 };
 506 
 507 #define SCAN_AND_FORWARD(cp,scan_limit,block_is_obj,block_size) {            \
 508   /* Compute the new addresses for the live objects and store it in the mark \
 509    * Used by universe::mark_sweep_phase2()                                   \
 510    */                                                                        \
 511   HeapWord* compact_top; /* This is where we are currently compacting to. */ \
 512                                                                              \
 513   /* We're sure to be here before any objects are compacted into this        \
 514    * space, so this is a good time to initialize this:                       \
 515    */                                                                        \
 516   set_compaction_top(bottom());                                              \
 517                                                                              \
 518   if (cp->space == NULL) {                                                   \
 519     assert(cp->gen != NULL, "need a generation");                            \
 520     assert(cp->threshold == NULL, "just checking");                          \
 521     assert(cp->gen->first_compaction_space() == this, "just checking");      \
 522     cp->space = cp->gen->first_compaction_space();                           \
 523     compact_top = cp->space->bottom();                                       \
 524     cp->space->set_compaction_top(compact_top);                              \
 525     cp->threshold = cp->space->initialize_threshold();                       \
 526   } else {                                                                   \
 527     compact_top = cp->space->compaction_top();                               \
 528   }                                                                          \
 529                                                                              \
 530   /* We allow some amount of garbage towards the bottom of the space, so     \
 531    * we don't start compacting before there is a significant gain to be made.\
 532    * Occasionally, we want to ensure a full compaction, which is determined  \
 533    * by the MarkSweepAlwaysCompactCount parameter.                           \
 534    */                                                                        \
 535   int invocations = SharedHeap::heap()->perm_gen()->stat_record()->invocations;\
 536   bool skip_dead = (MarkSweepAlwaysCompactCount < 1)                         \
 537     ||((invocations % MarkSweepAlwaysCompactCount) != 0);                    \
 538                                                                              \
 539   size_t allowed_deadspace = 0;                                              \
 540   if (skip_dead) {                                                           \
 541     const size_t ratio = allowed_dead_ratio();                               \
 542     allowed_deadspace = (capacity() * ratio / 100) / HeapWordSize;           \
 543   }                                                                          \
 544                                                                              \
 545   HeapWord* q = bottom();                                                    \
 546   HeapWord* t = scan_limit();                                                \
 547                                                                              \
 548   HeapWord*  end_of_live= q;    /* One byte beyond the last byte of the last \
 549                                    live object. */                           \
 550   HeapWord*  first_dead = end();/* The first dead object. */                 \
 551   LiveRange* liveRange  = NULL; /* The current live range, recorded in the   \
 552                                    first header of preceding free area. */   \
 553   _first_dead = first_dead;                                                  \
 554                                                                              \
 555   const intx interval = PrefetchScanIntervalInBytes;                         \
 556                                                                              \
 557   while (q < t) {                                                            \
 558     assert(!block_is_obj(q) ||                                               \
 559            oop(q)->mark()->is_marked() || oop(q)->mark()->is_unlocked() ||   \
 560            oop(q)->mark()->has_bias_pattern(),                               \
 561            "these are the only valid states during a mark sweep");           \
 562     if (block_is_obj(q) && oop(q)->is_gc_marked()) {                         \
 563       /* prefetch beyond q */                                                \
 564       Prefetch::write(q, interval);                                          \
 565       /* size_t size = oop(q)->size();  changing this for cms for perm gen */\
 566       size_t size = block_size(q);                                           \
 567       compact_top = cp->space->forward(oop(q), size, cp, compact_top);       \
 568       q += size;                                                             \
 569       end_of_live = q;                                                       \
 570     } else {                                                                 \
 571       /* run over all the contiguous dead objects */                         \
 572       HeapWord* end = q;                                                     \
 573       do {                                                                   \
 574         /* prefetch beyond end */                                            \
 575         Prefetch::write(end, interval);                                      \
 576         end += block_size(end);                                              \
 577       } while (end < t && (!block_is_obj(end) || !oop(end)->is_gc_marked()));\
 578                                                                              \
 579       /* see if we might want to pretend this object is alive so that        \
 580        * we don't have to compact quite as often.                            \
 581        */                                                                    \
 582       if (allowed_deadspace > 0 && q == compact_top) {                       \
 583         size_t sz = pointer_delta(end, q);                                   \
 584         if (insert_deadspace(allowed_deadspace, q, sz)) {                    \
 585           compact_top = cp->space->forward(oop(q), sz, cp, compact_top);     \
 586           q = end;                                                           \
 587           end_of_live = end;                                                 \
 588           continue;                                                          \
 589         }                                                                    \
 590       }                                                                      \
 591                                                                              \
 592       /* otherwise, it really is a free region. */                           \
 593                                                                              \
 594       /* for the previous LiveRange, record the end of the live objects. */  \
 595       if (liveRange) {                                                       \
 596         liveRange->set_end(q);                                               \
 597       }                                                                      \
 598                                                                              \
 599       /* record the current LiveRange object.                                \
 600        * liveRange->start() is overlaid on the mark word.                    \
 601        */                                                                    \
 602       liveRange = (LiveRange*)q;                                             \
 603       liveRange->set_start(end);                                             \
 604       liveRange->set_end(end);                                               \
 605                                                                              \
 606       /* see if this is the first dead region. */                            \
 607       if (q < first_dead) {                                                  \
 608         first_dead = q;                                                      \
 609       }                                                                      \
 610                                                                              \
 611       /* move on to the next object */                                       \
 612       q = end;                                                               \
 613     }                                                                        \
 614   }                                                                          \
 615                                                                              \
 616   assert(q == t, "just checking");                                           \
 617   if (liveRange != NULL) {                                                   \
 618     liveRange->set_end(q);                                                   \
 619   }                                                                          \
 620   _end_of_live = end_of_live;                                                \
 621   if (end_of_live < first_dead) {                                            \
 622     first_dead = end_of_live;                                                \
 623   }                                                                          \
 624   _first_dead = first_dead;                                                  \
 625                                                                              \
 626   /* save the compaction_top of the compaction space. */                     \
 627   cp->space->set_compaction_top(compact_top);                                \
 628 }
 629 
 630 #define SCAN_AND_ADJUST_POINTERS(adjust_obj_size) {                             \
 631   /* adjust all the interior pointers to point at the new locations of objects  \
 632    * Used by MarkSweep::mark_sweep_phase3() */                                  \
 633                                                                                 \
 634   HeapWord* q = bottom();                                                       \
 635   HeapWord* t = _end_of_live;  /* Established by "prepare_for_compaction". */   \
 636                                                                                 \
 637   assert(_first_dead <= _end_of_live, "Stands to reason, no?");                 \
 638                                                                                 \
 639   if (q < t && _first_dead > q &&                                               \
 640       !oop(q)->is_gc_marked()) {                                                \
 641     /* we have a chunk of the space which hasn't moved and we've                \
 642      * reinitialized the mark word during the previous pass, so we can't        \
 643      * use is_gc_marked for the traversal. */                                   \
 644     HeapWord* end = _first_dead;                                                \
 645                                                                                 \
 646     while (q < end) {                                                           \
 647       /* I originally tried to conjoin "block_start(q) == q" to the             \
 648        * assertion below, but that doesn't work, because you can't              \
 649        * accurately traverse previous objects to get to the current one         \
 650        * after their pointers (including pointers into permGen) have been       \
 651        * updated, until the actual compaction is done.  dld, 4/00 */            \
 652       assert(block_is_obj(q),                                                   \
 653              "should be at block boundaries, and should be looking at objs");   \
 654                                                                                 \
 655       VALIDATE_MARK_SWEEP_ONLY(MarkSweep::track_interior_pointers(oop(q)));     \
 656                                                                                 \
 657       /* point all the oops to the new location */                              \
 658       size_t size = oop(q)->adjust_pointers();                                  \
 659       size = adjust_obj_size(size);                                             \
 660                                                                                 \
 661       VALIDATE_MARK_SWEEP_ONLY(MarkSweep::check_interior_pointers());           \
 662                                                                                 \
 663       VALIDATE_MARK_SWEEP_ONLY(MarkSweep::validate_live_oop(oop(q), size));     \
 664                                                                                 \
 665       q += size;                                                                \
 666     }                                                                           \
 667                                                                                 \
 668     if (_first_dead == t) {                                                     \
 669       q = t;                                                                    \
 670     } else {                                                                    \
 671       /* $$$ This is funky.  Using this to read the previously written          \
 672        * LiveRange.  See also use below. */                                     \
 673       q = (HeapWord*)oop(_first_dead)->mark()->decode_pointer();                \
 674     }                                                                           \
 675   }                                                                             \
 676                                                                                 \
 677   const intx interval = PrefetchScanIntervalInBytes;                            \
 678                                                                                 \
 679   debug_only(HeapWord* prev_q = NULL);                                          \
 680   while (q < t) {                                                               \
 681     /* prefetch beyond q */                                                     \
 682     Prefetch::write(q, interval);                                               \
 683     if (oop(q)->is_gc_marked()) {                                               \
 684       /* q is alive */                                                          \
 685       VALIDATE_MARK_SWEEP_ONLY(MarkSweep::track_interior_pointers(oop(q)));     \
 686       /* point all the oops to the new location */                              \
 687       size_t size = oop(q)->adjust_pointers();                                  \
 688       size = adjust_obj_size(size);                                             \
 689       VALIDATE_MARK_SWEEP_ONLY(MarkSweep::check_interior_pointers());           \
 690       VALIDATE_MARK_SWEEP_ONLY(MarkSweep::validate_live_oop(oop(q), size));     \
 691       debug_only(prev_q = q);                                                   \
 692       q += size;                                                                \
 693     } else {                                                                    \
 694       /* q is not a live object, so its mark should point at the next           \
 695        * live object */                                                         \
 696       debug_only(prev_q = q);                                                   \
 697       q = (HeapWord*) oop(q)->mark()->decode_pointer();                         \
 698       assert(q > prev_q, "we should be moving forward through memory");         \
 699     }                                                                           \
 700   }                                                                             \
 701                                                                                 \
 702   assert(q == t, "just checking");                                              \
 703 }
 704 
 705 #define SCAN_AND_COMPACT(obj_size) {                                            \
 706   /* Copy all live objects to their new location                                \
 707    * Used by MarkSweep::mark_sweep_phase4() */                                  \
 708                                                                                 \
 709   HeapWord*       q = bottom();                                                 \
 710   HeapWord* const t = _end_of_live;                                             \
 711   debug_only(HeapWord* prev_q = NULL);                                          \
 712                                                                                 \
 713   if (q < t && _first_dead > q &&                                               \
 714       !oop(q)->is_gc_marked()) {                                                \
 715     debug_only(                                                                 \
 716     /* we have a chunk of the space which hasn't moved and we've reinitialized  \
 717      * the mark word during the previous pass, so we can't use is_gc_marked for \
 718      * the traversal. */                                                        \
 719     HeapWord* const end = _first_dead;                                          \
 720                                                                                 \
 721     while (q < end) {                                                           \
 722       size_t size = obj_size(q);                                                \
 723       assert(!oop(q)->is_gc_marked(),                                           \
 724              "should be unmarked (special dense prefix handling)");             \
 725       VALIDATE_MARK_SWEEP_ONLY(MarkSweep::live_oop_moved_to(q, size, q));       \
 726       debug_only(prev_q = q);                                                   \
 727       q += size;                                                                \
 728     }                                                                           \
 729     )  /* debug_only */                                                         \
 730                                                                                 \
 731     if (_first_dead == t) {                                                     \
 732       q = t;                                                                    \
 733     } else {                                                                    \
 734       /* $$$ Funky */                                                           \
 735       q = (HeapWord*) oop(_first_dead)->mark()->decode_pointer();               \
 736     }                                                                           \
 737   }                                                                             \
 738                                                                                 \
 739   const intx scan_interval = PrefetchScanIntervalInBytes;                       \
 740   const intx copy_interval = PrefetchCopyIntervalInBytes;                       \
 741   while (q < t) {                                                               \
 742     if (!oop(q)->is_gc_marked()) {                                              \
 743       /* mark is pointer to next marked oop */                                  \
 744       debug_only(prev_q = q);                                                   \
 745       q = (HeapWord*) oop(q)->mark()->decode_pointer();                         \
 746       assert(q > prev_q, "we should be moving forward through memory");         \
 747     } else {                                                                    \
 748       /* prefetch beyond q */                                                   \
 749       Prefetch::read(q, scan_interval);                                         \
 750                                                                                 \
 751       /* size and destination */                                                \
 752       size_t size = obj_size(q);                                                \
 753       HeapWord* compaction_top = (HeapWord*)oop(q)->forwardee();                \
 754                                                                                 \
 755       /* prefetch beyond compaction_top */                                      \
 756       Prefetch::write(compaction_top, copy_interval);                           \
 757                                                                                 \
 758       /* copy object and reinit its mark */                                     \
 759       VALIDATE_MARK_SWEEP_ONLY(MarkSweep::live_oop_moved_to(q, size,            \
 760                                                             compaction_top));   \
 761       assert(q != compaction_top, "everything in this pass should be moving");  \
 762       Copy::aligned_conjoint_words(q, compaction_top, size);                    \
 763       oop(compaction_top)->init_mark();                                         \
 764       assert(oop(compaction_top)->klass() != NULL, "should have a class");      \
 765                                                                                 \
 766       debug_only(prev_q = q);                                                   \
 767       q += size;                                                                \
 768     }                                                                           \
 769   }                                                                             \
 770                                                                                 \
 771   /* Let's remember if we were empty before we did the compaction. */           \
 772   bool was_empty = used_region().is_empty();                                    \
 773   /* Reset space after compaction is complete */                                \
 774   reset_after_compaction();                                                     \
 775   /* We do this clear, below, since it has overloaded meanings for some */      \
 776   /* space subtypes.  For example, OffsetTableContigSpace's that were   */      \
 777   /* compacted into will have had their offset table thresholds updated */      \
 778   /* continuously, but those that weren't need to have their thresholds */      \
 779   /* re-initialized.  Also mangles unused area for debugging.           */      \
 780   if (used_region().is_empty()) {                                               \
 781     if (!was_empty) clear(SpaceDecorator::Mangle);                              \
 782   } else {                                                                      \
 783     if (ZapUnusedHeapArea) mangle_unused_area();                                \
 784   }                                                                             \
 785 }
 786 
 787 class GenSpaceMangler;
 788 
 789 // A space in which the free area is contiguous.  It therefore supports
 790 // faster allocation, and compaction.
 791 class ContiguousSpace: public CompactibleSpace {
 792   friend class OneContigSpaceCardGeneration;
 793   friend class VMStructs;
 794  protected:
 795   HeapWord* _top;
 796   HeapWord* _concurrent_iteration_safe_limit;
 797   // A helper for mangling the unused area of the space in debug builds.
 798   GenSpaceMangler* _mangler;
 799 
 800   GenSpaceMangler* mangler() { return _mangler; }
 801 
 802   // Allocation helpers (return NULL if full).
 803   inline HeapWord* allocate_impl(size_t word_size, HeapWord* end_value);
 804   inline HeapWord* par_allocate_impl(size_t word_size, HeapWord* end_value);
 805 
 806  public:
 807   ContiguousSpace();
 808   ~ContiguousSpace();
 809 
 810   virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
 811   virtual void clear(bool mangle_space);
 812 
 813   // Accessors
 814   HeapWord* top() const            { return _top;    }
 815   void set_top(HeapWord* value)    { _top = value; }
 816 
 817   virtual void set_saved_mark()    { _saved_mark_word = top();    }
 818   void reset_saved_mark()          { _saved_mark_word = bottom(); }
 819 
 820   WaterMark bottom_mark()     { return WaterMark(this, bottom()); }
 821   WaterMark top_mark()        { return WaterMark(this, top()); }
 822   WaterMark saved_mark()      { return WaterMark(this, saved_mark_word()); }
 823   bool saved_mark_at_top() const { return saved_mark_word() == top(); }
 824 
 825   // In debug mode mangle (write it with a particular bit
 826   // pattern) the unused part of a space.
 827 
 828   // Used to save the an address in a space for later use during mangling.
 829   void set_top_for_allocations(HeapWord* v) PRODUCT_RETURN;
 830   // Used to save the space's current top for later use during mangling.
 831   void set_top_for_allocations() PRODUCT_RETURN;
 832 
 833   // Mangle regions in the space from the current top up to the
 834   // previously mangled part of the space.
 835   void mangle_unused_area() PRODUCT_RETURN;
 836   // Mangle [top, end)
 837   void mangle_unused_area_complete() PRODUCT_RETURN;
 838   // Mangle the given MemRegion.
 839   void mangle_region(MemRegion mr) PRODUCT_RETURN;
 840 
 841   // Do some sparse checking on the area that should have been mangled.
 842   void check_mangled_unused_area(HeapWord* limit) PRODUCT_RETURN;
 843   // Check the complete area that should have been mangled.
 844   // This code may be NULL depending on the macro DEBUG_MANGLING.
 845   void check_mangled_unused_area_complete() PRODUCT_RETURN;
 846 
 847   // Size computations: sizes in bytes.
 848   size_t capacity() const        { return byte_size(bottom(), end()); }
 849   size_t used() const            { return byte_size(bottom(), top()); }
 850   size_t free() const            { return byte_size(top(),    end()); }
 851 
 852   // Override from space.
 853   bool is_in(const void* p) const;
 854 
 855   virtual bool is_free_block(const HeapWord* p) const;
 856 
 857   // In a contiguous space we have a more obvious bound on what parts
 858   // contain objects.
 859   MemRegion used_region() const { return MemRegion(bottom(), top()); }
 860 
 861   MemRegion used_region_at_save_marks() const {
 862     return MemRegion(bottom(), saved_mark_word());
 863   }
 864 
 865   // Allocation (return NULL if full)
 866   virtual HeapWord* allocate(size_t word_size);
 867   virtual HeapWord* par_allocate(size_t word_size);
 868 
 869   virtual bool obj_allocated_since_save_marks(const oop obj) const {
 870     return (HeapWord*)obj >= saved_mark_word();
 871   }
 872 
 873   // Iteration
 874   void oop_iterate(OopClosure* cl);
 875   void oop_iterate(MemRegion mr, OopClosure* cl);
 876   void object_iterate(ObjectClosure* blk);
 877   // For contiguous spaces this method will iterate safely over objects
 878   // in the space (i.e., between bottom and top) when at a safepoint.
 879   void safe_object_iterate(ObjectClosure* blk);
 880   void object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl);
 881   // iterates on objects up to the safe limit
 882   HeapWord* object_iterate_careful(ObjectClosureCareful* cl);
 883   HeapWord* concurrent_iteration_safe_limit() {
 884     assert(_concurrent_iteration_safe_limit <= top(),
 885            "_concurrent_iteration_safe_limit update missed");
 886     return _concurrent_iteration_safe_limit;
 887   }
 888   // changes the safe limit, all objects from bottom() to the new
 889   // limit should be properly initialized
 890   void set_concurrent_iteration_safe_limit(HeapWord* new_limit) {
 891     assert(new_limit <= top(), "uninitialized objects in the safe range");
 892     _concurrent_iteration_safe_limit = new_limit;
 893   }
 894 
 895 #ifndef SERIALGC
 896   // In support of parallel oop_iterate.
 897   #define ContigSpace_PAR_OOP_ITERATE_DECL(OopClosureType, nv_suffix)  \
 898     void par_oop_iterate(MemRegion mr, OopClosureType* blk);
 899 
 900     ALL_PAR_OOP_ITERATE_CLOSURES(ContigSpace_PAR_OOP_ITERATE_DECL)
 901   #undef ContigSpace_PAR_OOP_ITERATE_DECL
 902 #endif // SERIALGC
 903 
 904   // Compaction support
 905   virtual void reset_after_compaction() {
 906     assert(compaction_top() >= bottom() && compaction_top() <= end(), "should point inside space");
 907     set_top(compaction_top());
 908     // set new iteration safe limit
 909     set_concurrent_iteration_safe_limit(compaction_top());
 910   }
 911   virtual size_t minimum_free_block_size() const { return 0; }
 912 
 913   // Override.
 914   DirtyCardToOopClosure* new_dcto_cl(OopClosure* cl,
 915                                      CardTableModRefBS::PrecisionStyle precision,
 916                                      HeapWord* boundary = NULL);
 917 
 918   // Apply "blk->do_oop" to the addresses of all reference fields in objects
 919   // starting with the _saved_mark_word, which was noted during a generation's
 920   // save_marks and is required to denote the head of an object.
 921   // Fields in objects allocated by applications of the closure
 922   // *are* included in the iteration.
 923   // Updates _saved_mark_word to point to just after the last object
 924   // iterated over.
 925 #define ContigSpace_OOP_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix)  \
 926   void oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk);
 927 
 928   ALL_SINCE_SAVE_MARKS_CLOSURES(ContigSpace_OOP_SINCE_SAVE_MARKS_DECL)
 929 #undef ContigSpace_OOP_SINCE_SAVE_MARKS_DECL
 930 
 931   // Same as object_iterate, but starting from "mark", which is required
 932   // to denote the start of an object.  Objects allocated by
 933   // applications of the closure *are* included in the iteration.
 934   virtual void object_iterate_from(WaterMark mark, ObjectClosure* blk);
 935 
 936   // Very inefficient implementation.
 937   virtual HeapWord* block_start_const(const void* p) const;
 938   size_t block_size(const HeapWord* p) const;
 939   // If a block is in the allocated area, it is an object.
 940   bool block_is_obj(const HeapWord* p) const { return p < top(); }
 941 
 942   // Addresses for inlined allocation
 943   HeapWord** top_addr() { return &_top; }
 944   HeapWord** end_addr() { return &_end; }
 945 
 946   // Overrides for more efficient compaction support.
 947   void prepare_for_compaction(CompactPoint* cp);
 948 
 949   // PrintHeapAtGC support.
 950   virtual void print_on(outputStream* st) const;
 951 
 952   // Checked dynamic downcasts.
 953   virtual ContiguousSpace* toContiguousSpace() {
 954     return this;
 955   }
 956 
 957   // Debugging
 958   virtual void verify() const;
 959 
 960   // Used to increase collection frequency.  "factor" of 0 means entire
 961   // space.
 962   void allocate_temporary_filler(int factor);
 963 
 964 };
 965 
 966 
 967 // A dirty card to oop closure that does filtering.
 968 // It knows how to filter out objects that are outside of the _boundary.
 969 class Filtering_DCTOC : public DirtyCardToOopClosure {
 970 protected:
 971   // Override.
 972   void walk_mem_region(MemRegion mr,
 973                        HeapWord* bottom, HeapWord* top);
 974 
 975   // Walk the given memory region, from bottom to top, applying
 976   // the given oop closure to (possibly) all objects found. The
 977   // given oop closure may or may not be the same as the oop
 978   // closure with which this closure was created, as it may
 979   // be a filtering closure which makes use of the _boundary.
 980   // We offer two signatures, so the FilteringClosure static type is
 981   // apparent.
 982   virtual void walk_mem_region_with_cl(MemRegion mr,
 983                                        HeapWord* bottom, HeapWord* top,
 984                                        OopClosure* cl) = 0;
 985   virtual void walk_mem_region_with_cl(MemRegion mr,
 986                                        HeapWord* bottom, HeapWord* top,
 987                                        FilteringClosure* cl) = 0;
 988 
 989 public:
 990   Filtering_DCTOC(Space* sp, OopClosure* cl,
 991                   CardTableModRefBS::PrecisionStyle precision,
 992                   HeapWord* boundary) :
 993     DirtyCardToOopClosure(sp, cl, precision, boundary) {}
 994 };
 995 
 996 // A dirty card to oop closure for contiguous spaces
 997 // (ContiguousSpace and sub-classes).
 998 // It is a FilteringClosure, as defined above, and it knows:
 999 //
1000 // 1. That the actual top of any area in a memory region
1001 //    contained by the space is bounded by the end of the contiguous
1002 //    region of the space.
1003 // 2. That the space is really made up of objects and not just
1004 //    blocks.
1005 
1006 class ContiguousSpaceDCTOC : public Filtering_DCTOC {
1007 protected:
1008   // Overrides.
1009   HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj);
1010 
1011   virtual void walk_mem_region_with_cl(MemRegion mr,
1012                                        HeapWord* bottom, HeapWord* top,
1013                                        OopClosure* cl);
1014   virtual void walk_mem_region_with_cl(MemRegion mr,
1015                                        HeapWord* bottom, HeapWord* top,
1016                                        FilteringClosure* cl);
1017 
1018 public:
1019   ContiguousSpaceDCTOC(ContiguousSpace* sp, OopClosure* cl,
1020                        CardTableModRefBS::PrecisionStyle precision,
1021                        HeapWord* boundary) :
1022     Filtering_DCTOC(sp, cl, precision, boundary)
1023   {}
1024 };
1025 
1026 
1027 // Class EdenSpace describes eden-space in new generation.
1028 
1029 class DefNewGeneration;
1030 
1031 class EdenSpace : public ContiguousSpace {
1032   friend class VMStructs;
1033  private:
1034   DefNewGeneration* _gen;
1035 
1036   // _soft_end is used as a soft limit on allocation.  As soft limits are
1037   // reached, the slow-path allocation code can invoke other actions and then
1038   // adjust _soft_end up to a new soft limit or to end().
1039   HeapWord* _soft_end;
1040 
1041  public:
1042   EdenSpace(DefNewGeneration* gen) :
1043    _gen(gen), _soft_end(NULL) {}
1044 
1045   // Get/set just the 'soft' limit.
1046   HeapWord* soft_end()               { return _soft_end; }
1047   HeapWord** soft_end_addr()         { return &_soft_end; }
1048   void set_soft_end(HeapWord* value) { _soft_end = value; }
1049 
1050   // Override.
1051   void clear(bool mangle_space);
1052 
1053   // Set both the 'hard' and 'soft' limits (_end and _soft_end).
1054   void set_end(HeapWord* value) {
1055     set_soft_end(value);
1056     ContiguousSpace::set_end(value);
1057   }
1058 
1059   // Allocation (return NULL if full)
1060   HeapWord* allocate(size_t word_size);
1061   HeapWord* par_allocate(size_t word_size);
1062 };
1063 
1064 // Class ConcEdenSpace extends EdenSpace for the sake of safe
1065 // allocation while soft-end is being modified concurrently
1066 
1067 class ConcEdenSpace : public EdenSpace {
1068  public:
1069   ConcEdenSpace(DefNewGeneration* gen) : EdenSpace(gen) { }
1070 
1071   // Allocation (return NULL if full)
1072   HeapWord* par_allocate(size_t word_size);
1073 };
1074 
1075 
1076 // A ContigSpace that Supports an efficient "block_start" operation via
1077 // a BlockOffsetArray (whose BlockOffsetSharedArray may be shared with
1078 // other spaces.)  This is the abstract base class for old generation
1079 // (tenured, perm) spaces.
1080 
1081 class OffsetTableContigSpace: public ContiguousSpace {
1082   friend class VMStructs;
1083  protected:
1084   BlockOffsetArrayContigSpace _offsets;
1085   Mutex _par_alloc_lock;
1086 
1087  public:
1088   // Constructor
1089   OffsetTableContigSpace(BlockOffsetSharedArray* sharedOffsetArray,
1090                          MemRegion mr);
1091 
1092   void set_bottom(HeapWord* value);
1093   void set_end(HeapWord* value);
1094 
1095   void clear(bool mangle_space);
1096 
1097   inline HeapWord* block_start_const(const void* p) const;
1098 
1099   // Add offset table update.
1100   virtual inline HeapWord* allocate(size_t word_size);
1101   inline HeapWord* par_allocate(size_t word_size);
1102 
1103   // MarkSweep support phase3
1104   virtual HeapWord* initialize_threshold();
1105   virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* end);
1106 
1107   virtual void print_on(outputStream* st) const;
1108 
1109   // Debugging
1110   void verify() const;
1111 
1112   // Shared space support
1113   void serialize_block_offset_array_offsets(SerializeOopClosure* soc);
1114 };
1115 
1116 
1117 // Class TenuredSpace is used by TenuredGeneration
1118 
1119 class TenuredSpace: public OffsetTableContigSpace {
1120   friend class VMStructs;
1121  protected:
1122   // Mark sweep support
1123   size_t allowed_dead_ratio() const;
1124  public:
1125   // Constructor
1126   TenuredSpace(BlockOffsetSharedArray* sharedOffsetArray,
1127                MemRegion mr) :
1128     OffsetTableContigSpace(sharedOffsetArray, mr) {}
1129 };
1130 
1131 
1132 // Class ContigPermSpace is used by CompactingPermGen
1133 
1134 class ContigPermSpace: public OffsetTableContigSpace {
1135   friend class VMStructs;
1136  protected:
1137   // Mark sweep support
1138   size_t allowed_dead_ratio() const;
1139  public:
1140   // Constructor
1141   ContigPermSpace(BlockOffsetSharedArray* sharedOffsetArray, MemRegion mr) :
1142     OffsetTableContigSpace(sharedOffsetArray, mr) {}
1143 };
1144 
1145 #endif // SHARE_VM_MEMORY_SPACE_HPP