rev 48000 : [mq]: open.patch

   1 /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
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   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
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   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).
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  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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  20  * or visit www.oracle.com if you need additional information or have any
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  24 
  25 #ifndef SHARE_VM_GC_SHARED_GENERATION_HPP
  26 #define SHARE_VM_GC_SHARED_GENERATION_HPP
  27 
  28 #include "gc/shared/collectorCounters.hpp"
  29 #include "gc/shared/referenceProcessor.hpp"
  30 #include "logging/log.hpp"
  31 #include "memory/allocation.hpp"
  32 #include "memory/memRegion.hpp"
  33 #include "memory/universe.hpp"
  34 #include "memory/virtualspace.hpp"
  35 #include "runtime/mutex.hpp"
  36 #include "runtime/perfData.hpp"
  37 
  38 // A Generation models a heap area for similarly-aged objects.
  39 // It will contain one ore more spaces holding the actual objects.
  40 //
  41 // The Generation class hierarchy:
  42 //
  43 // Generation                      - abstract base class
  44 // - DefNewGeneration              - allocation area (copy collected)
  45 //   - ParNewGeneration            - a DefNewGeneration that is collected by
  46 //                                   several threads
  47 // - CardGeneration                 - abstract class adding offset array behavior
  48 //   - TenuredGeneration             - tenured (old object) space (markSweepCompact)
  49 //   - ConcurrentMarkSweepGeneration - Mostly Concurrent Mark Sweep Generation
  50 //                                       (Detlefs-Printezis refinement of
  51 //                                       Boehm-Demers-Schenker)
  52 //
  53 // The system configurations currently allowed are:
  54 //
  55 //   DefNewGeneration + TenuredGeneration
  56 //
  57 //   ParNewGeneration + ConcurrentMarkSweepGeneration
  58 //
  59 
  60 class DefNewGeneration;
  61 class GenerationSpec;
  62 class CompactibleSpace;
  63 class ContiguousSpace;
  64 class CompactPoint;
  65 class OopsInGenClosure;
  66 class OopClosure;
  67 class ScanClosure;
  68 class FastScanClosure;
  69 class GenCollectedHeap;
  70 class GCStats;
  71 
  72 // A "ScratchBlock" represents a block of memory in one generation usable by
  73 // another.  It represents "num_words" free words, starting at and including
  74 // the address of "this".
  75 struct ScratchBlock {
  76   ScratchBlock* next;
  77   size_t num_words;
  78   HeapWord scratch_space[1];  // Actually, of size "num_words-2" (assuming
  79                               // first two fields are word-sized.)
  80 };
  81 
  82 class Generation: public CHeapObj<mtGC> {
  83   friend class VMStructs;
  84  private:
  85   jlong _time_of_last_gc; // time when last gc on this generation happened (ms)
  86   MemRegion _prev_used_region; // for collectors that want to "remember" a value for
  87                                // used region at some specific point during collection.
  88 
  89   GCMemoryManager* _gc_manager;
  90 
  91  protected:
  92   // Minimum and maximum addresses for memory reserved (not necessarily
  93   // committed) for generation.
  94   // Used by card marking code. Must not overlap with address ranges of
  95   // other generations.
  96   MemRegion _reserved;
  97 
  98   // Memory area reserved for generation
  99   VirtualSpace _virtual_space;
 100 
 101   // ("Weak") Reference processing support
 102   ReferenceProcessor* _ref_processor;
 103 
 104   // Performance Counters
 105   CollectorCounters* _gc_counters;
 106 
 107   // Statistics for garbage collection
 108   GCStats* _gc_stats;
 109 
 110   // Initialize the generation.
 111   Generation(ReservedSpace rs, size_t initial_byte_size);
 112 
 113   // Apply "cl->do_oop" to (the address of) (exactly) all the ref fields in
 114   // "sp" that point into younger generations.
 115   // The iteration is only over objects allocated at the start of the
 116   // iterations; objects allocated as a result of applying the closure are
 117   // not included.
 118   void younger_refs_in_space_iterate(Space* sp, OopsInGenClosure* cl, uint n_threads);
 119 
 120  public:
 121   // The set of possible generation kinds.
 122   enum Name {
 123     DefNew,
 124     ParNew,
 125     MarkSweepCompact,
 126     ConcurrentMarkSweep,
 127     Other
 128   };
 129 
 130   enum SomePublicConstants {
 131     // Generations are GenGrain-aligned and have size that are multiples of
 132     // GenGrain.
 133     // Note: on ARM we add 1 bit for card_table_base to be properly aligned
 134     // (we expect its low byte to be zero - see implementation of post_barrier)
 135     LogOfGenGrain = 16 ARM32_ONLY(+1),
 136     GenGrain = 1 << LogOfGenGrain
 137   };
 138 
 139   // allocate and initialize ("weak") refs processing support
 140   virtual void ref_processor_init();
 141   void set_ref_processor(ReferenceProcessor* rp) {
 142     assert(_ref_processor == NULL, "clobbering existing _ref_processor");
 143     _ref_processor = rp;
 144   }
 145 
 146   virtual Generation::Name kind() { return Generation::Other; }
 147 
 148   // This properly belongs in the collector, but for now this
 149   // will do.
 150   virtual bool refs_discovery_is_atomic() const { return true;  }
 151   virtual bool refs_discovery_is_mt()     const { return false; }
 152 
 153   // Space inquiries (results in bytes)
 154   size_t initial_size();
 155   virtual size_t capacity() const = 0;  // The maximum number of object bytes the
 156                                         // generation can currently hold.
 157   virtual size_t used() const = 0;      // The number of used bytes in the gen.
 158   virtual size_t free() const = 0;      // The number of free bytes in the gen.
 159 
 160   // Support for java.lang.Runtime.maxMemory(); see CollectedHeap.
 161   // Returns the total number of bytes  available in a generation
 162   // for the allocation of objects.
 163   virtual size_t max_capacity() const;
 164 
 165   // If this is a young generation, the maximum number of bytes that can be
 166   // allocated in this generation before a GC is triggered.
 167   virtual size_t capacity_before_gc() const { return 0; }
 168 
 169   // The largest number of contiguous free bytes in the generation,
 170   // including expansion  (Assumes called at a safepoint.)
 171   virtual size_t contiguous_available() const = 0;
 172   // The largest number of contiguous free bytes in this or any higher generation.
 173   virtual size_t max_contiguous_available() const;
 174 
 175   // Returns true if promotions of the specified amount are
 176   // likely to succeed without a promotion failure.
 177   // Promotion of the full amount is not guaranteed but
 178   // might be attempted in the worst case.
 179   virtual bool promotion_attempt_is_safe(size_t max_promotion_in_bytes) const;
 180 
 181   // For a non-young generation, this interface can be used to inform a
 182   // generation that a promotion attempt into that generation failed.
 183   // Typically used to enable diagnostic output for post-mortem analysis,
 184   // but other uses of the interface are not ruled out.
 185   virtual void promotion_failure_occurred() { /* does nothing */ }
 186 
 187   // Return an estimate of the maximum allocation that could be performed
 188   // in the generation without triggering any collection or expansion
 189   // activity.  It is "unsafe" because no locks are taken; the result
 190   // should be treated as an approximation, not a guarantee, for use in
 191   // heuristic resizing decisions.
 192   virtual size_t unsafe_max_alloc_nogc() const = 0;
 193 
 194   // Returns true if this generation cannot be expanded further
 195   // without a GC. Override as appropriate.
 196   virtual bool is_maximal_no_gc() const {
 197     return _virtual_space.uncommitted_size() == 0;
 198   }
 199 
 200   MemRegion reserved() const { return _reserved; }
 201 
 202   // Returns a region guaranteed to contain all the objects in the
 203   // generation.
 204   virtual MemRegion used_region() const { return _reserved; }
 205 
 206   MemRegion prev_used_region() const { return _prev_used_region; }
 207   virtual void  save_used_region()   { _prev_used_region = used_region(); }
 208 
 209   // Returns "TRUE" iff "p" points into the committed areas in the generation.
 210   // For some kinds of generations, this may be an expensive operation.
 211   // To avoid performance problems stemming from its inadvertent use in
 212   // product jvm's, we restrict its use to assertion checking or
 213   // verification only.
 214   virtual bool is_in(const void* p) const;
 215 
 216   /* Returns "TRUE" iff "p" points into the reserved area of the generation. */
 217   bool is_in_reserved(const void* p) const {
 218     return _reserved.contains(p);
 219   }
 220 
 221   // If some space in the generation contains the given "addr", return a
 222   // pointer to that space, else return "NULL".
 223   virtual Space* space_containing(const void* addr) const;
 224 
 225   // Iteration - do not use for time critical operations
 226   virtual void space_iterate(SpaceClosure* blk, bool usedOnly = false) = 0;
 227 
 228   // Returns the first space, if any, in the generation that can participate
 229   // in compaction, or else "NULL".
 230   virtual CompactibleSpace* first_compaction_space() const = 0;
 231 
 232   // Returns "true" iff this generation should be used to allocate an
 233   // object of the given size.  Young generations might
 234   // wish to exclude very large objects, for example, since, if allocated
 235   // often, they would greatly increase the frequency of young-gen
 236   // collection.
 237   virtual bool should_allocate(size_t word_size, bool is_tlab) {
 238     bool result = false;
 239     size_t overflow_limit = (size_t)1 << (BitsPerSize_t - LogHeapWordSize);
 240     if (!is_tlab || supports_tlab_allocation()) {
 241       result = (word_size > 0) && (word_size < overflow_limit);
 242     }
 243     return result;
 244   }
 245 
 246   // Allocate and returns a block of the requested size, or returns "NULL".
 247   // Assumes the caller has done any necessary locking.
 248   virtual HeapWord* allocate(size_t word_size, bool is_tlab) = 0;
 249 
 250   // Like "allocate", but performs any necessary locking internally.
 251   virtual HeapWord* par_allocate(size_t word_size, bool is_tlab) = 0;
 252 
 253   // Some generation may offer a region for shared, contiguous allocation,
 254   // via inlined code (by exporting the address of the top and end fields
 255   // defining the extent of the contiguous allocation region.)
 256 
 257   // This function returns "true" iff the heap supports this kind of
 258   // allocation.  (More precisely, this means the style of allocation that
 259   // increments *top_addr()" with a CAS.) (Default is "no".)
 260   // A generation that supports this allocation style must use lock-free
 261   // allocation for *all* allocation, since there are times when lock free
 262   // allocation will be concurrent with plain "allocate" calls.
 263   virtual bool supports_inline_contig_alloc() const { return false; }
 264 
 265   // These functions return the addresses of the fields that define the
 266   // boundaries of the contiguous allocation area.  (These fields should be
 267   // physically near to one another.)
 268   virtual HeapWord* volatile* top_addr() const { return NULL; }
 269   virtual HeapWord** end_addr() const { return NULL; }
 270 
 271   // Thread-local allocation buffers
 272   virtual bool supports_tlab_allocation() const { return false; }
 273   virtual size_t tlab_capacity() const {
 274     guarantee(false, "Generation doesn't support thread local allocation buffers");
 275     return 0;
 276   }
 277   virtual size_t tlab_used() const {
 278     guarantee(false, "Generation doesn't support thread local allocation buffers");
 279     return 0;
 280   }
 281   virtual size_t unsafe_max_tlab_alloc() const {
 282     guarantee(false, "Generation doesn't support thread local allocation buffers");
 283     return 0;
 284   }
 285 
 286   // "obj" is the address of an object in a younger generation.  Allocate space
 287   // for "obj" in the current (or some higher) generation, and copy "obj" into
 288   // the newly allocated space, if possible, returning the result (or NULL if
 289   // the allocation failed).
 290   //
 291   // The "obj_size" argument is just obj->size(), passed along so the caller can
 292   // avoid repeating the virtual call to retrieve it.
 293   virtual oop promote(oop obj, size_t obj_size);
 294 
 295   // Thread "thread_num" (0 <= i < ParalleGCThreads) wants to promote
 296   // object "obj", whose original mark word was "m", and whose size is
 297   // "word_sz".  If possible, allocate space for "obj", copy obj into it
 298   // (taking care to copy "m" into the mark word when done, since the mark
 299   // word of "obj" may have been overwritten with a forwarding pointer, and
 300   // also taking care to copy the klass pointer *last*.  Returns the new
 301   // object if successful, or else NULL.
 302   virtual oop par_promote(int thread_num, oop obj, markOop m, size_t word_sz);
 303 
 304   // Informs the current generation that all par_promote_alloc's in the
 305   // collection have been completed; any supporting data structures can be
 306   // reset.  Default is to do nothing.
 307   virtual void par_promote_alloc_done(int thread_num) {}
 308 
 309   // Informs the current generation that all oop_since_save_marks_iterates
 310   // performed by "thread_num" in the current collection, if any, have been
 311   // completed; any supporting data structures can be reset.  Default is to
 312   // do nothing.
 313   virtual void par_oop_since_save_marks_iterate_done(int thread_num) {}
 314 
 315   // Returns "true" iff collect() should subsequently be called on this
 316   // this generation. See comment below.
 317   // This is a generic implementation which can be overridden.
 318   //
 319   // Note: in the current (1.4) implementation, when genCollectedHeap's
 320   // incremental_collection_will_fail flag is set, all allocations are
 321   // slow path (the only fast-path place to allocate is DefNew, which
 322   // will be full if the flag is set).
 323   // Thus, older generations which collect younger generations should
 324   // test this flag and collect if it is set.
 325   virtual bool should_collect(bool   full,
 326                               size_t word_size,
 327                               bool   is_tlab) {
 328     return (full || should_allocate(word_size, is_tlab));
 329   }
 330 
 331   // Returns true if the collection is likely to be safely
 332   // completed. Even if this method returns true, a collection
 333   // may not be guaranteed to succeed, and the system should be
 334   // able to safely unwind and recover from that failure, albeit
 335   // at some additional cost.
 336   virtual bool collection_attempt_is_safe() {
 337     guarantee(false, "Are you sure you want to call this method?");
 338     return true;
 339   }
 340 
 341   // Perform a garbage collection.
 342   // If full is true attempt a full garbage collection of this generation.
 343   // Otherwise, attempting to (at least) free enough space to support an
 344   // allocation of the given "word_size".
 345   virtual void collect(bool   full,
 346                        bool   clear_all_soft_refs,
 347                        size_t word_size,
 348                        bool   is_tlab) = 0;
 349 
 350   // Perform a heap collection, attempting to create (at least) enough
 351   // space to support an allocation of the given "word_size".  If
 352   // successful, perform the allocation and return the resulting
 353   // "oop" (initializing the allocated block). If the allocation is
 354   // still unsuccessful, return "NULL".
 355   virtual HeapWord* expand_and_allocate(size_t word_size,
 356                                         bool is_tlab,
 357                                         bool parallel = false) = 0;
 358 
 359   // Some generations may require some cleanup or preparation actions before
 360   // allowing a collection.  The default is to do nothing.
 361   virtual void gc_prologue(bool full) {}
 362 
 363   // Some generations may require some cleanup actions after a collection.
 364   // The default is to do nothing.
 365   virtual void gc_epilogue(bool full) {}
 366 
 367   // Save the high water marks for the used space in a generation.
 368   virtual void record_spaces_top() {}
 369 
 370   // Some generations may need to be "fixed-up" after some allocation
 371   // activity to make them parsable again. The default is to do nothing.
 372   virtual void ensure_parsability() {}
 373 
 374   // Time (in ms) when we were last collected or now if a collection is
 375   // in progress.
 376   virtual jlong time_of_last_gc(jlong now) {
 377     // Both _time_of_last_gc and now are set using a time source
 378     // that guarantees monotonically non-decreasing values provided
 379     // the underlying platform provides such a source. So we still
 380     // have to guard against non-monotonicity.
 381     NOT_PRODUCT(
 382       if (now < _time_of_last_gc) {
 383         log_warning(gc)("time warp: " JLONG_FORMAT " to " JLONG_FORMAT, _time_of_last_gc, now);
 384       }
 385     )
 386     return _time_of_last_gc;
 387   }
 388 
 389   virtual void update_time_of_last_gc(jlong now)  {
 390     _time_of_last_gc = now;
 391   }
 392 
 393   // Generations may keep statistics about collection. This method
 394   // updates those statistics. current_generation is the generation
 395   // that was most recently collected. This allows the generation to
 396   // decide what statistics are valid to collect. For example, the
 397   // generation can decide to gather the amount of promoted data if
 398   // the collection of the young generation has completed.
 399   GCStats* gc_stats() const { return _gc_stats; }
 400   virtual void update_gc_stats(Generation* current_generation, bool full) {}
 401 
 402   // Mark sweep support phase2
 403   virtual void prepare_for_compaction(CompactPoint* cp);
 404   // Mark sweep support phase3
 405   virtual void adjust_pointers();
 406   // Mark sweep support phase4
 407   virtual void compact();
 408   virtual void post_compact() { ShouldNotReachHere(); }
 409 
 410   // Support for CMS's rescan. In this general form we return a pointer
 411   // to an abstract object that can be used, based on specific previously
 412   // decided protocols, to exchange information between generations,
 413   // information that may be useful for speeding up certain types of
 414   // garbage collectors. A NULL value indicates to the client that
 415   // no data recording is expected by the provider. The data-recorder is
 416   // expected to be GC worker thread-local, with the worker index
 417   // indicated by "thr_num".
 418   virtual void* get_data_recorder(int thr_num) { return NULL; }
 419   virtual void sample_eden_chunk() {}
 420 
 421   // Some generations may require some cleanup actions before allowing
 422   // a verification.
 423   virtual void prepare_for_verify() {}
 424 
 425   // Accessing "marks".
 426 
 427   // This function gives a generation a chance to note a point between
 428   // collections.  For example, a contiguous generation might note the
 429   // beginning allocation point post-collection, which might allow some later
 430   // operations to be optimized.
 431   virtual void save_marks() {}
 432 
 433   // This function allows generations to initialize any "saved marks".  That
 434   // is, should only be called when the generation is empty.
 435   virtual void reset_saved_marks() {}
 436 
 437   // This function is "true" iff any no allocations have occurred in the
 438   // generation since the last call to "save_marks".
 439   virtual bool no_allocs_since_save_marks() = 0;
 440 
 441   // Apply "cl->apply" to (the addresses of) all reference fields in objects
 442   // allocated in the current generation since the last call to "save_marks".
 443   // If more objects are allocated in this generation as a result of applying
 444   // the closure, iterates over reference fields in those objects as well.
 445   // Calls "save_marks" at the end of the iteration.
 446   // General signature...
 447   virtual void oop_since_save_marks_iterate_v(OopsInGenClosure* cl) = 0;
 448   // ...and specializations for de-virtualization.  (The general
 449   // implementation of the _nv versions call the virtual version.
 450   // Note that the _nv suffix is not really semantically necessary,
 451   // but it avoids some not-so-useful warnings on Solaris.)
 452 #define Generation_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix)             \
 453   virtual void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) {    \
 454     oop_since_save_marks_iterate_v((OopsInGenClosure*)cl);                      \
 455   }
 456   SPECIALIZED_SINCE_SAVE_MARKS_CLOSURES(Generation_SINCE_SAVE_MARKS_DECL)
 457 
 458 #undef Generation_SINCE_SAVE_MARKS_DECL
 459 
 460   // The "requestor" generation is performing some garbage collection
 461   // action for which it would be useful to have scratch space.  If
 462   // the target is not the requestor, no gc actions will be required
 463   // of the target.  The requestor promises to allocate no more than
 464   // "max_alloc_words" in the target generation (via promotion say,
 465   // if the requestor is a young generation and the target is older).
 466   // If the target generation can provide any scratch space, it adds
 467   // it to "list", leaving "list" pointing to the head of the
 468   // augmented list.  The default is to offer no space.
 469   virtual void contribute_scratch(ScratchBlock*& list, Generation* requestor,
 470                                   size_t max_alloc_words) {}
 471 
 472   // Give each generation an opportunity to do clean up for any
 473   // contributed scratch.
 474   virtual void reset_scratch() {}
 475 
 476   // When an older generation has been collected, and perhaps resized,
 477   // this method will be invoked on all younger generations (from older to
 478   // younger), allowing them to resize themselves as appropriate.
 479   virtual void compute_new_size() = 0;
 480 
 481   // Printing
 482   virtual const char* name() const = 0;
 483   virtual const char* short_name() const = 0;
 484 
 485   // Reference Processing accessor
 486   ReferenceProcessor* const ref_processor() { return _ref_processor; }
 487 
 488   // Iteration.
 489 
 490   // Iterate over all the ref-containing fields of all objects in the
 491   // generation, calling "cl.do_oop" on each.
 492   virtual void oop_iterate(ExtendedOopClosure* cl);
 493 
 494   // Iterate over all objects in the generation, calling "cl.do_object" on
 495   // each.
 496   virtual void object_iterate(ObjectClosure* cl);
 497 
 498   // Iterate over all safe objects in the generation, calling "cl.do_object" on
 499   // each.  An object is safe if its references point to other objects in
 500   // the heap.  This defaults to object_iterate() unless overridden.
 501   virtual void safe_object_iterate(ObjectClosure* cl);
 502 
 503   // Apply "cl->do_oop" to (the address of) all and only all the ref fields
 504   // in the current generation that contain pointers to objects in younger
 505   // generations. Objects allocated since the last "save_marks" call are
 506   // excluded.
 507   virtual void younger_refs_iterate(OopsInGenClosure* cl, uint n_threads) = 0;
 508 
 509   // Inform a generation that it longer contains references to objects
 510   // in any younger generation.    [e.g. Because younger gens are empty,
 511   // clear the card table.]
 512   virtual void clear_remembered_set() { }
 513 
 514   // Inform a generation that some of its objects have moved.  [e.g. The
 515   // generation's spaces were compacted, invalidating the card table.]
 516   virtual void invalidate_remembered_set() { }
 517 
 518   // Block abstraction.
 519 
 520   // Returns the address of the start of the "block" that contains the
 521   // address "addr".  We say "blocks" instead of "object" since some heaps
 522   // may not pack objects densely; a chunk may either be an object or a
 523   // non-object.
 524   virtual HeapWord* block_start(const void* addr) const;
 525 
 526   // Requires "addr" to be the start of a chunk, and returns its size.
 527   // "addr + size" is required to be the start of a new chunk, or the end
 528   // of the active area of the heap.
 529   virtual size_t block_size(const HeapWord* addr) const ;
 530 
 531   // Requires "addr" to be the start of a block, and returns "TRUE" iff
 532   // the block is an object.
 533   virtual bool block_is_obj(const HeapWord* addr) const;
 534 
 535   void print_heap_change(size_t prev_used) const;
 536 
 537   virtual void print() const;
 538   virtual void print_on(outputStream* st) const;
 539 
 540   virtual void verify() = 0;
 541 
 542   struct StatRecord {
 543     int invocations;
 544     elapsedTimer accumulated_time;
 545     StatRecord() :
 546       invocations(0),
 547       accumulated_time(elapsedTimer()) {}
 548   };
 549 private:
 550   StatRecord _stat_record;
 551 public:
 552   StatRecord* stat_record() { return &_stat_record; }
 553 
 554   virtual void print_summary_info_on(outputStream* st);
 555 
 556   // Performance Counter support
 557   virtual void update_counters() = 0;
 558   virtual CollectorCounters* counters() { return _gc_counters; }
 559 
 560   GCMemoryManager* gc_manager() const {
 561     assert(_gc_manager != NULL, "not initialized yet");
 562     return _gc_manager;
 563   }
 564 
 565   void set_gc_manager(GCMemoryManager* gc_manager) {
 566     _gc_manager = gc_manager;
 567   }
 568 
 569 };
 570 
 571 #endif // SHARE_VM_GC_SHARED_GENERATION_HPP
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