Mercurial > jdk8-mips64-public > hotspot / file revision

 /*

  * Copyright 1997-2009 Sun Microsystems, Inc.  All Rights Reserved.

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

  *

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

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

  * published by the Free Software Foundation.

  *

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

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

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

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

  * accompanied this code).

  *

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

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

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

  *

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

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

  * have any questions.

  *

  */

 // A Generation models a heap area for similarly-aged objects.

 // It will contain one ore more spaces holding the actual objects.

 //

 // The Generation class hierarchy:

 //

 // Generation                      - abstract base class

 // - DefNewGeneration              - allocation area (copy collected)

 //   - ParNewGeneration            - a DefNewGeneration that is collected by

 //                                   several threads

 // - CardGeneration                 - abstract class adding offset array behavior

 //   - OneContigSpaceCardGeneration - abstract class holding a single

 //                                    contiguous space with card marking

 //     - TenuredGeneration         - tenured (old object) space (markSweepCompact)

 //     - CompactingPermGenGen      - reflective object area (klasses, methods, symbols, ...)

 //   - ConcurrentMarkSweepGeneration - Mostly Concurrent Mark Sweep Generation

 //                                       (Detlefs-Printezis refinement of

 //                                       Boehm-Demers-Schenker)

 //

 // The system configurations currently allowed are:

 //

 //   DefNewGeneration + TenuredGeneration + PermGeneration

 //   DefNewGeneration + ConcurrentMarkSweepGeneration + ConcurrentMarkSweepPermGen

 //

 //   ParNewGeneration + TenuredGeneration + PermGeneration

 //   ParNewGeneration + ConcurrentMarkSweepGeneration + ConcurrentMarkSweepPermGen

 //

 class DefNewGeneration;

 class GenerationSpec;

 class CompactibleSpace;

 class ContiguousSpace;

 class CompactPoint;

 class OopsInGenClosure;

 class OopClosure;

 class ScanClosure;

 class FastScanClosure;

 class GenCollectedHeap;

 class GenRemSet;

 class GCStats;

 // A "ScratchBlock" represents a block of memory in one generation usable by

 // another.  It represents "num_words" free words, starting at and including

 // the address of "this".

 struct ScratchBlock {

   ScratchBlock* next;

   size_t num_words;

   HeapWord scratch_space[1];  // Actually, of size "num_words-2" (assuming

                               // first two fields are word-sized.)

 };

 class Generation: public CHeapObj {

   friend class VMStructs;

  private:

   jlong _time_of_last_gc; // time when last gc on this generation happened (ms)

   MemRegion _prev_used_region; // for collectors that want to "remember" a value for

                                // used region at some specific point during collection.

  protected:

   // Minimum and maximum addresses for memory reserved (not necessarily

   // committed) for generation.

   // Used by card marking code. Must not overlap with address ranges of

   // other generations.

   MemRegion _reserved;

   // Memory area reserved for generation

   VirtualSpace _virtual_space;

   // Level in the generation hierarchy.

   int _level;

   // ("Weak") Reference processing support

   ReferenceProcessor* _ref_processor;

   // Performance Counters

   CollectorCounters* _gc_counters;

   // Statistics for garbage collection

   GCStats* _gc_stats;

   // Returns the next generation in the configuration, or else NULL if this

   // is the highest generation.

   Generation* next_gen() const;

   // Initialize the generation.

   Generation(ReservedSpace rs, size_t initial_byte_size, int level);

   // Apply "cl->do_oop" to (the address of) (exactly) all the ref fields in

   // "sp" that point into younger generations.

   // The iteration is only over objects allocated at the start of the

   // iterations; objects allocated as a result of applying the closure are

   // not included.

   void younger_refs_in_space_iterate(Space* sp, OopsInGenClosure* cl);

  public:

   // The set of possible generation kinds.

   enum Name {

     ASParNew,

     ASConcurrentMarkSweep,

     DefNew,

     ParNew,

     MarkSweepCompact,

     ConcurrentMarkSweep,

     Other

   };

   enum SomePublicConstants {

     // Generations are GenGrain-aligned and have size that are multiples of

     // GenGrain.

     LogOfGenGrain = 16,

     GenGrain = 1 << LogOfGenGrain

   };

   // allocate and initialize ("weak") refs processing support

   virtual void ref_processor_init();

   void set_ref_processor(ReferenceProcessor* rp) {

     assert(_ref_processor == NULL, "clobbering existing _ref_processor");

     _ref_processor = rp;

   }

   virtual Generation::Name kind() { return Generation::Other; }

   GenerationSpec* spec();

   // This properly belongs in the collector, but for now this

   // will do.

   virtual bool refs_discovery_is_atomic() const { return true;  }

   virtual bool refs_discovery_is_mt()     const { return false; }

   // Space enquiries (results in bytes)

   virtual size_t capacity() const = 0;  // The maximum number of object bytes the

                                         // generation can currently hold.

   virtual size_t used() const = 0;      // The number of used bytes in the gen.

   virtual size_t free() const = 0;      // The number of free bytes in the gen.

   // Support for java.lang.Runtime.maxMemory(); see CollectedHeap.

   // Returns the total number of bytes  available in a generation

   // for the allocation of objects.

   virtual size_t max_capacity() const;

   // If this is a young generation, the maximum number of bytes that can be

   // allocated in this generation before a GC is triggered.

   virtual size_t capacity_before_gc() const { return 0; }

   // The largest number of contiguous free bytes in the generation,

   // including expansion  (Assumes called at a safepoint.)

   virtual size_t contiguous_available() const = 0;

   // The largest number of contiguous free bytes in this or any higher generation.

   virtual size_t max_contiguous_available() const;

   // Returns true if promotions of the specified amount can

   // be attempted safely (without a vm failure).

   // Promotion of the full amount is not guaranteed but

   // can be attempted.

   //   younger_handles_promotion_failure

   // is true if the younger generation handles a promotion

   // failure.

   virtual bool promotion_attempt_is_safe(size_t promotion_in_bytes,

     bool younger_handles_promotion_failure) const;

   // For a non-young generation, this interface can be used to inform a

   // generation that a promotion attempt into that generation failed.

   // Typically used to enable diagnostic output for post-mortem analysis,

   // but other uses of the interface are not ruled out.

   virtual void promotion_failure_occurred() { /* does nothing */ }

   // Return an estimate of the maximum allocation that could be performed

   // in the generation without triggering any collection or expansion

   // activity.  It is "unsafe" because no locks are taken; the result

   // should be treated as an approximation, not a guarantee, for use in

   // heuristic resizing decisions.

   virtual size_t unsafe_max_alloc_nogc() const = 0;

   // Returns true if this generation cannot be expanded further

   // without a GC. Override as appropriate.

   virtual bool is_maximal_no_gc() const {

     return _virtual_space.uncommitted_size() == 0;

   }

   MemRegion reserved() const { return _reserved; }

   // Returns a region guaranteed to contain all the objects in the

   // generation.

   virtual MemRegion used_region() const { return _reserved; }

   MemRegion prev_used_region() const { return _prev_used_region; }

   virtual void  save_used_region()   { _prev_used_region = used_region(); }

   // Returns "TRUE" iff "p" points into an allocated object in the generation.

   // For some kinds of generations, this may be an expensive operation.

   // To avoid performance problems stemming from its inadvertent use in

   // product jvm's, we restrict its use to assertion checking or

   // verification only.

   virtual bool is_in(const void* p) const;

   /* Returns "TRUE" iff "p" points into the reserved area of the generation. */

   bool is_in_reserved(const void* p) const {

     return _reserved.contains(p);

   }

   // Check that the generation kind is DefNewGeneration or a sub

   // class of DefNewGeneration and return a DefNewGeneration*

   DefNewGeneration*  as_DefNewGeneration();

   // If some space in the generation contains the given "addr", return a

   // pointer to that space, else return "NULL".

   virtual Space* space_containing(const void* addr) const;

   // Iteration - do not use for time critical operations

   virtual void space_iterate(SpaceClosure* blk, bool usedOnly = false) = 0;

   // Returns the first space, if any, in the generation that can participate

   // in compaction, or else "NULL".

   virtual CompactibleSpace* first_compaction_space() const = 0;

   // Returns "true" iff this generation should be used to allocate an

   // object of the given size.  Young generations might

   // wish to exclude very large objects, for example, since, if allocated

   // often, they would greatly increase the frequency of young-gen

   // collection.

   virtual bool should_allocate(size_t word_size, bool is_tlab) {

     bool result = false;

     size_t overflow_limit = (size_t)1 << (BitsPerSize_t - LogHeapWordSize);

     if (!is_tlab || supports_tlab_allocation()) {

       result = (word_size > 0) && (word_size < overflow_limit);

     }

     return result;

   }

   // Allocate and returns a block of the requested size, or returns "NULL".

   // Assumes the caller has done any necessary locking.

   virtual HeapWord* allocate(size_t word_size, bool is_tlab) = 0;

   // Like "allocate", but performs any necessary locking internally.

   virtual HeapWord* par_allocate(size_t word_size, bool is_tlab) = 0;

   // A 'younger' gen has reached an allocation limit, and uses this to notify

   // the next older gen.  The return value is a new limit, or NULL if none.  The

   // caller must do the necessary locking.

   virtual HeapWord* allocation_limit_reached(Space* space, HeapWord* top,

                                              size_t word_size) {

     return NULL;

   }

   // Some generation may offer a region for shared, contiguous allocation,

   // via inlined code (by exporting the address of the top and end fields

   // defining the extent of the contiguous allocation region.)

   // This function returns "true" iff the heap supports this kind of

   // allocation.  (More precisely, this means the style of allocation that

   // increments *top_addr()" with a CAS.) (Default is "no".)

   // A generation that supports this allocation style must use lock-free

   // allocation for *all* allocation, since there are times when lock free

   // allocation will be concurrent with plain "allocate" calls.

   virtual bool supports_inline_contig_alloc() const { return false; }

   // These functions return the addresses of the fields that define the

   // boundaries of the contiguous allocation area.  (These fields should be

   // physicall near to one another.)

   virtual HeapWord** top_addr() const { return NULL; }

   virtual HeapWord** end_addr() const { return NULL; }

   // Thread-local allocation buffers

   virtual bool supports_tlab_allocation() const { return false; }

   virtual size_t tlab_capacity() const {

     guarantee(false, "Generation doesn't support thread local allocation buffers");

     return 0;

   }

   virtual size_t unsafe_max_tlab_alloc() const {

     guarantee(false, "Generation doesn't support thread local allocation buffers");

     return 0;

   }

   // "obj" is the address of an object in a younger generation.  Allocate space

   // for "obj" in the current (or some higher) generation, and copy "obj" into

   // the newly allocated space, if possible, returning the result (or NULL if

   // the allocation failed).

   //

   // The "obj_size" argument is just obj->size(), passed along so the caller can

   // avoid repeating the virtual call to retrieve it.

   virtual oop promote(oop obj, size_t obj_size);

   // Thread "thread_num" (0 <= i < ParalleGCThreads) wants to promote

   // object "obj", whose original mark word was "m", and whose size is

   // "word_sz".  If possible, allocate space for "obj", copy obj into it

   // (taking care to copy "m" into the mark word when done, since the mark

   // word of "obj" may have been overwritten with a forwarding pointer, and

   // also taking care to copy the klass pointer *last*.  Returns the new

   // object if successful, or else NULL.

   virtual oop par_promote(int thread_num,

                           oop obj, markOop m, size_t word_sz);

   // Undo, if possible, the most recent par_promote_alloc allocation by

   // "thread_num" ("obj", of "word_sz").

   virtual void par_promote_alloc_undo(int thread_num,

                                       HeapWord* obj, size_t word_sz);

   // Informs the current generation that all par_promote_alloc's in the

   // collection have been completed; any supporting data structures can be

   // reset.  Default is to do nothing.

   virtual void par_promote_alloc_done(int thread_num) {}

   // Informs the current generation that all oop_since_save_marks_iterates

   // performed by "thread_num" in the current collection, if any, have been

   // completed; any supporting data structures can be reset.  Default is to

   // do nothing.

   virtual void par_oop_since_save_marks_iterate_done(int thread_num) {}

   // This generation will collect all younger generations

   // during a full collection.

   virtual bool full_collects_younger_generations() const { return false; }

   // This generation does in-place marking, meaning that mark words

   // are mutated during the marking phase and presumably reinitialized

   // to a canonical value after the GC. This is currently used by the

   // biased locking implementation to determine whether additional

   // work is required during the GC prologue and epilogue.

   virtual bool performs_in_place_marking() const { return true; }

   // Returns "true" iff collect() should subsequently be called on this

   // this generation. See comment below.

   // This is a generic implementation which can be overridden.

   //

   // Note: in the current (1.4) implementation, when genCollectedHeap's

   // incremental_collection_will_fail flag is set, all allocations are

   // slow path (the only fast-path place to allocate is DefNew, which

   // will be full if the flag is set).

   // Thus, older generations which collect younger generations should

   // test this flag and collect if it is set.

   virtual bool should_collect(bool   full,

                               size_t word_size,

                               bool   is_tlab) {

     return (full || should_allocate(word_size, is_tlab));

   }

   // Perform a garbage collection.

   // If full is true attempt a full garbage collection of this generation.

   // Otherwise, attempting to (at least) free enough space to support an

   // allocation of the given "word_size".

   virtual void collect(bool   full,

                        bool   clear_all_soft_refs,

                        size_t word_size,

                        bool   is_tlab) = 0;

   // Perform a heap collection, attempting to create (at least) enough

   // space to support an allocation of the given "word_size".  If

   // successful, perform the allocation and return the resulting

   // "oop" (initializing the allocated block). If the allocation is

   // still unsuccessful, return "NULL".

   virtual HeapWord* expand_and_allocate(size_t word_size,

                                         bool is_tlab,

                                         bool parallel = false) = 0;

   // Some generations may require some cleanup or preparation actions before

   // allowing a collection.  The default is to do nothing.

   virtual void gc_prologue(bool full) {};

   // Some generations may require some cleanup actions after a collection.

   // The default is to do nothing.

   virtual void gc_epilogue(bool full) {};

   // Save the high water marks for the used space in a generation.

   virtual void record_spaces_top() {};

   // Some generations may need to be "fixed-up" after some allocation

   // activity to make them parsable again. The default is to do nothing.

   virtual void ensure_parsability() {};

   // Time (in ms) when we were last collected or now if a collection is

   // in progress.

   virtual jlong time_of_last_gc(jlong now) {

     // XXX See note in genCollectedHeap::millis_since_last_gc()

     NOT_PRODUCT(

       if (now < _time_of_last_gc) {

         warning("time warp: %d to %d", _time_of_last_gc, now);

       }

     )

     return _time_of_last_gc;

   }

   virtual void update_time_of_last_gc(jlong now)  {

     _time_of_last_gc = now;

   }

   // Generations may keep statistics about collection.  This

   // method updates those statistics.  current_level is

   // the level of the collection that has most recently

   // occurred.  This allows the generation to decide what

   // statistics are valid to collect.  For example, the

   // generation can decide to gather the amount of promoted data

   // if the collection of the younger generations has completed.

   GCStats* gc_stats() const { return _gc_stats; }

   virtual void update_gc_stats(int current_level, bool full) {}

   // Mark sweep support phase2

   virtual void prepare_for_compaction(CompactPoint* cp);

   // Mark sweep support phase3

   virtual void pre_adjust_pointers() {ShouldNotReachHere();}

   virtual void adjust_pointers();

   // Mark sweep support phase4

   virtual void compact();

   virtual void post_compact() {ShouldNotReachHere();}

   // Support for CMS's rescan. In this general form we return a pointer

   // to an abstract object that can be used, based on specific previously

   // decided protocols, to exchange information between generations,

   // information that may be useful for speeding up certain types of

   // garbage collectors. A NULL value indicates to the client that

   // no data recording is expected by the provider. The data-recorder is

   // expected to be GC worker thread-local, with the worker index

   // indicated by "thr_num".

   virtual void* get_data_recorder(int thr_num) { return NULL; }

   // Some generations may require some cleanup actions before allowing

   // a verification.

   virtual void prepare_for_verify() {};

   // Accessing "marks".

   // This function gives a generation a chance to note a point between

   // collections.  For example, a contiguous generation might note the

   // beginning allocation point post-collection, which might allow some later

   // operations to be optimized.

   virtual void save_marks() {}

   // This function allows generations to initialize any "saved marks".  That

   // is, should only be called when the generation is empty.

   virtual void reset_saved_marks() {}

   // This function is "true" iff any no allocations have occurred in the

   // generation since the last call to "save_marks".

   virtual bool no_allocs_since_save_marks() = 0;

   // Apply "cl->apply" to (the addresses of) all reference fields in objects

   // allocated in the current generation since the last call to "save_marks".

   // If more objects are allocated in this generation as a result of applying

   // the closure, iterates over reference fields in those objects as well.

   // Calls "save_marks" at the end of the iteration.

   // General signature...

   virtual void oop_since_save_marks_iterate_v(OopsInGenClosure* cl) = 0;

   // ...and specializations for de-virtualization.  (The general

   // implemention of the _nv versions call the virtual version.

   // Note that the _nv suffix is not really semantically necessary,

   // but it avoids some not-so-useful warnings on Solaris.)

 #define Generation_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix)             \

   virtual void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) {    \

     oop_since_save_marks_iterate_v((OopsInGenClosure*)cl);                      \

   }

   SPECIALIZED_SINCE_SAVE_MARKS_CLOSURES(Generation_SINCE_SAVE_MARKS_DECL)

 #undef Generation_SINCE_SAVE_MARKS_DECL

   // The "requestor" generation is performing some garbage collection

   // action for which it would be useful to have scratch space.  If

   // the target is not the requestor, no gc actions will be required

   // of the target.  The requestor promises to allocate no more than

   // "max_alloc_words" in the target generation (via promotion say,

   // if the requestor is a young generation and the target is older).

   // If the target generation can provide any scratch space, it adds

   // it to "list", leaving "list" pointing to the head of the

   // augmented list.  The default is to offer no space.

   virtual void contribute_scratch(ScratchBlock*& list, Generation* requestor,

                                   size_t max_alloc_words) {}

   // Give each generation an opportunity to do clean up for any

   // contributed scratch.

   virtual void reset_scratch() {};

   // When an older generation has been collected, and perhaps resized,

   // this method will be invoked on all younger generations (from older to

   // younger), allowing them to resize themselves as appropriate.

   virtual void compute_new_size() = 0;

   // Printing

   virtual const char* name() const = 0;

   virtual const char* short_name() const = 0;

   int level() const { return _level; }

   // Attributes

   // True iff the given generation may only be the youngest generation.

   virtual bool must_be_youngest() const = 0;

   // True iff the given generation may only be the oldest generation.

   virtual bool must_be_oldest() const = 0;

   // Reference Processing accessor

   ReferenceProcessor* const ref_processor() { return _ref_processor; }

   // Iteration.

   // Iterate over all the ref-containing fields of all objects in the

   // generation, calling "cl.do_oop" on each.

   virtual void oop_iterate(OopClosure* cl);

   // Same as above, restricted to the intersection of a memory region and

   // the generation.

   virtual void oop_iterate(MemRegion mr, OopClosure* cl);

   // Iterate over all objects in the generation, calling "cl.do_object" on

   // each.

   virtual void object_iterate(ObjectClosure* cl);

   // Iterate over all safe objects in the generation, calling "cl.do_object" on

   // each.  An object is safe if its references point to other objects in

   // the heap.  This defaults to object_iterate() unless overridden.

   virtual void safe_object_iterate(ObjectClosure* cl);

   // Iterate over all objects allocated in the generation since the last

   // collection, calling "cl.do_object" on each.  The generation must have

   // been initialized properly to support this function, or else this call

   // will fail.

   virtual void object_iterate_since_last_GC(ObjectClosure* cl) = 0;

   // Apply "cl->do_oop" to (the address of) all and only all the ref fields

   // in the current generation that contain pointers to objects in younger

   // generations. Objects allocated since the last "save_marks" call are

   // excluded.

   virtual void younger_refs_iterate(OopsInGenClosure* cl) = 0;

   // Inform a generation that it longer contains references to objects

   // in any younger generation.    [e.g. Because younger gens are empty,

   // clear the card table.]

   virtual void clear_remembered_set() { }

   // Inform a generation that some of its objects have moved.  [e.g. The

   // generation's spaces were compacted, invalidating the card table.]

   virtual void invalidate_remembered_set() { }

   // Block abstraction.

   // Returns the address of the start of the "block" that contains the

   // address "addr".  We say "blocks" instead of "object" since some heaps

   // may not pack objects densely; a chunk may either be an object or a

   // non-object.

   virtual HeapWord* block_start(const void* addr) const;

   // Requires "addr" to be the start of a chunk, and returns its size.

   // "addr + size" is required to be the start of a new chunk, or the end

   // of the active area of the heap.

   virtual size_t block_size(const HeapWord* addr) const ;

   // Requires "addr" to be the start of a block, and returns "TRUE" iff

   // the block is an object.

   virtual bool block_is_obj(const HeapWord* addr) const;

   // PrintGC, PrintGCDetails support

   void print_heap_change(size_t prev_used) const;

   // PrintHeapAtGC support

   virtual void print() const;

   virtual void print_on(outputStream* st) const;

   virtual void verify(bool allow_dirty) = 0;

   struct StatRecord {

     int invocations;

     elapsedTimer accumulated_time;

     StatRecord() :

       invocations(0),

       accumulated_time(elapsedTimer()) {}

   };

 private:

   StatRecord _stat_record;

 public:

   StatRecord* stat_record() { return &_stat_record; }

   virtual void print_summary_info();

   virtual void print_summary_info_on(outputStream* st);

   // Performance Counter support

   virtual void update_counters() = 0;

   virtual CollectorCounters* counters() { return _gc_counters; }

 };

 // Class CardGeneration is a generation that is covered by a card table,

 // and uses a card-size block-offset array to implement block_start.

 // class BlockOffsetArray;

 // class BlockOffsetArrayContigSpace;

 class BlockOffsetSharedArray;

 class CardGeneration: public Generation {

   friend class VMStructs;

  protected:

   // This is shared with other generations.

   GenRemSet* _rs;

   // This is local to this generation.

   BlockOffsetSharedArray* _bts;

   CardGeneration(ReservedSpace rs, size_t initial_byte_size, int level,

                  GenRemSet* remset);

  public:

   // Attempt to expand the generation by "bytes".  Expand by at a

   // minimum "expand_bytes".  Return true if some amount (not

   // necessarily the full "bytes") was done.

   virtual bool expand(size_t bytes, size_t expand_bytes);

   virtual void clear_remembered_set();

   virtual void invalidate_remembered_set();

   virtual void prepare_for_verify();

   // Grow generation with specified size (returns false if unable to grow)

   virtual bool grow_by(size_t bytes) = 0;

   // Grow generation to reserved size.

   virtual bool grow_to_reserved() = 0;

 };

 // OneContigSpaceCardGeneration models a heap of old objects contained in a single

 // contiguous space.

 //

 // Garbage collection is performed using mark-compact.

 class OneContigSpaceCardGeneration: public CardGeneration {

   friend class VMStructs;

   // Abstractly, this is a subtype that gets access to protected fields.

   friend class CompactingPermGen;

   friend class VM_PopulateDumpSharedSpace;

  protected:

   size_t     _min_heap_delta_bytes;   // Minimum amount to expand.

   ContiguousSpace*  _the_space;       // actual space holding objects

   WaterMark  _last_gc;                // watermark between objects allocated before

                                       // and after last GC.

   // Grow generation with specified size (returns false if unable to grow)

   virtual bool grow_by(size_t bytes);

   // Grow generation to reserved size.

   virtual bool grow_to_reserved();

   // Shrink generation with specified size (returns false if unable to shrink)

   void shrink_by(size_t bytes);

   // Allocation failure

   virtual bool expand(size_t bytes, size_t expand_bytes);

   void shrink(size_t bytes);

   // Accessing spaces

   ContiguousSpace* the_space() const { return _the_space; }

  public:

   OneContigSpaceCardGeneration(ReservedSpace rs, size_t initial_byte_size,

                                size_t min_heap_delta_bytes,

                                int level, GenRemSet* remset,

                                ContiguousSpace* space) :

     CardGeneration(rs, initial_byte_size, level, remset),

     _the_space(space), _min_heap_delta_bytes(min_heap_delta_bytes)

   {}

   inline bool is_in(const void* p) const;

   // Space enquiries

   size_t capacity() const;

   size_t used() const;

   size_t free() const;

   MemRegion used_region() const;

   size_t unsafe_max_alloc_nogc() const;

   size_t contiguous_available() const;

   // Iteration

   void object_iterate(ObjectClosure* blk);

   void space_iterate(SpaceClosure* blk, bool usedOnly = false);

   void object_iterate_since_last_GC(ObjectClosure* cl);

   void younger_refs_iterate(OopsInGenClosure* blk);

   inline CompactibleSpace* first_compaction_space() const;

   virtual inline HeapWord* allocate(size_t word_size, bool is_tlab);

   virtual inline HeapWord* par_allocate(size_t word_size, bool is_tlab);

   // Accessing marks

   inline WaterMark top_mark();

   inline WaterMark bottom_mark();

 #define OneContig_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix)      \

   void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl);

   OneContig_SINCE_SAVE_MARKS_DECL(OopsInGenClosure,_v)

   SPECIALIZED_SINCE_SAVE_MARKS_CLOSURES(OneContig_SINCE_SAVE_MARKS_DECL)

   void save_marks();

   void reset_saved_marks();

   bool no_allocs_since_save_marks();

   inline size_t block_size(const HeapWord* addr) const;

   inline bool block_is_obj(const HeapWord* addr) const;

   virtual void collect(bool full,

                        bool clear_all_soft_refs,

                        size_t size,

                        bool is_tlab);

   HeapWord* expand_and_allocate(size_t size,

                                 bool is_tlab,

                                 bool parallel = false);

   virtual void prepare_for_verify();

   virtual void gc_epilogue(bool full);

   virtual void record_spaces_top();

   virtual void verify(bool allow_dirty);

   virtual void print_on(outputStream* st) const;

 };