1 /* 2 * Copyright (c) 1997, 2014, 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_GENERATION_HPP 26 #define SHARE_VM_MEMORY_GENERATION_HPP 27 28 #include "gc_implementation/shared/collectorCounters.hpp" 29 #include "memory/allocation.hpp" 30 #include "memory/memRegion.hpp" 31 #include "memory/referenceProcessor.hpp" 32 #include "memory/universe.hpp" 33 #include "memory/watermark.hpp" 34 #include "runtime/mutex.hpp" 35 #include "runtime/perfData.hpp" 36 #include "runtime/virtualspace.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 // - OneContigSpaceCardGeneration - abstract class holding a single 49 // contiguous space with card marking 50 // - TenuredGeneration - tenured (old object) space (markSweepCompact) 51 // - ConcurrentMarkSweepGeneration - Mostly Concurrent Mark Sweep Generation 52 // (Detlefs-Printezis refinement of 53 // Boehm-Demers-Schenker) 54 // 55 // The system configurations currently allowed are: 56 // 57 // DefNewGeneration + TenuredGeneration 58 // DefNewGeneration + ConcurrentMarkSweepGeneration 59 // 60 // ParNewGeneration + TenuredGeneration 61 // ParNewGeneration + ConcurrentMarkSweepGeneration 62 // 63 64 class DefNewGeneration; 65 class GenerationSpec; 66 class CompactibleSpace; 67 class ContiguousSpace; 68 class CompactPoint; 69 class OopsInGenClosure; 70 class OopClosure; 71 class ScanClosure; 72 class FastScanClosure; 73 class GenCollectedHeap; 74 class GenRemSet; 75 class GCStats; 76 77 // A "ScratchBlock" represents a block of memory in one generation usable by 78 // another. It represents "num_words" free words, starting at and including 79 // the address of "this". 80 struct ScratchBlock { 81 ScratchBlock* next; 82 size_t num_words; 83 HeapWord scratch_space[1]; // Actually, of size "num_words-2" (assuming 84 // first two fields are word-sized.) 85 }; 86 87 88 class Generation: public CHeapObj<mtGC> { 89 friend class VMStructs; 90 private: 91 jlong _time_of_last_gc; // time when last gc on this generation happened (ms) 92 MemRegion _prev_used_region; // for collectors that want to "remember" a value for 93 // used region at some specific point during collection. 94 95 protected: 96 // Minimum and maximum addresses for memory reserved (not necessarily 97 // committed) for generation. 98 // Used by card marking code. Must not overlap with address ranges of 99 // other generations. 100 MemRegion _reserved; 101 102 // Memory area reserved for generation 103 VirtualSpace _virtual_space; 104 105 // Level in the generation hierarchy. 106 int _level; 107 108 // ("Weak") Reference processing support 109 ReferenceProcessor* _ref_processor; 110 111 // Performance Counters 112 CollectorCounters* _gc_counters; 113 114 // Statistics for garbage collection 115 GCStats* _gc_stats; 116 117 enum { 118 _dispatch_index_generation_cms, 119 _dispatch_index_generation_def_new, 120 _dispatch_index_generation_one_contig 121 }; 122 const jbyte _dispatch_index; 123 124 // Returns the next generation in the configuration, or else NULL if this 125 // is the highest generation. 126 Generation* next_gen() const; 127 128 // Initialize the generation. 129 Generation(ReservedSpace rs, size_t initial_byte_size, int level, jbyte dispatch_index); 130 131 // Apply "cl->do_oop" to (the address of) (exactly) all the ref fields in 132 // "sp" that point into younger generations. 133 // The iteration is only over objects allocated at the start of the 134 // iterations; objects allocated as a result of applying the closure are 135 // not included. 136 void younger_refs_in_space_iterate(Space* sp, OopsInGenClosure* cl); 137 138 public: 139 // The set of possible generation kinds. 140 enum Name { 141 DefNew, 142 ParNew, 143 MarkSweepCompact, 144 ConcurrentMarkSweep, 145 Other 146 }; 147 148 enum SomePublicConstants { 149 // Generations are GenGrain-aligned and have size that are multiples of 150 // GenGrain. 151 // Note: on ARM we add 1 bit for card_table_base to be properly aligned 152 // (we expect its low byte to be zero - see implementation of post_barrier) 153 LogOfGenGrain = 16 ARM_ONLY(+1), 154 GenGrain = 1 << LogOfGenGrain 155 }; 156 157 // allocate and initialize ("weak") refs processing support 158 virtual void ref_processor_init(); 159 void set_ref_processor(ReferenceProcessor* rp) { 160 assert(_ref_processor == NULL, "clobbering existing _ref_processor"); 161 _ref_processor = rp; 162 } 163 164 virtual Generation::Name kind() { return Generation::Other; } 165 GenerationSpec* spec(); 166 167 // This properly belongs in the collector, but for now this 168 // will do. 169 virtual bool refs_discovery_is_atomic() const { return true; } 170 virtual bool refs_discovery_is_mt() const { return false; } 171 172 // Space enquiries (results in bytes) 173 virtual size_t capacity() const = 0; // The maximum number of object bytes the 174 // generation can currently hold. 175 virtual size_t used() const = 0; // The number of used bytes in the gen. 176 virtual size_t free() const = 0; // The number of free bytes in the gen. 177 178 // Support for java.lang.Runtime.maxMemory(); see CollectedHeap. 179 // Returns the total number of bytes available in a generation 180 // for the allocation of objects. 181 virtual size_t max_capacity() const; 182 183 // If this is a young generation, the maximum number of bytes that can be 184 // allocated in this generation before a GC is triggered. 185 virtual size_t capacity_before_gc() const { return 0; } 186 187 // The largest number of contiguous free bytes in the generation, 188 // including expansion (Assumes called at a safepoint.) 189 virtual size_t contiguous_available() const = 0; 190 // The largest number of contiguous free bytes in this or any higher generation. 191 virtual size_t max_contiguous_available() const; 192 193 // Returns true if promotions of the specified amount are 194 // likely to succeed without a promotion failure. 195 // Promotion of the full amount is not guaranteed but 196 // might be attempted in the worst case. 197 virtual bool promotion_attempt_is_safe(size_t max_promotion_in_bytes) const; 198 199 // For a non-young generation, this interface can be used to inform a 200 // generation that a promotion attempt into that generation failed. 201 // Typically used to enable diagnostic output for post-mortem analysis, 202 // but other uses of the interface are not ruled out. 203 virtual void promotion_failure_occurred() { /* does nothing */ } 204 205 // Return an estimate of the maximum allocation that could be performed 206 // in the generation without triggering any collection or expansion 207 // activity. It is "unsafe" because no locks are taken; the result 208 // should be treated as an approximation, not a guarantee, for use in 209 // heuristic resizing decisions. 210 virtual size_t unsafe_max_alloc_nogc() const = 0; 211 212 // Returns true if this generation cannot be expanded further 213 // without a GC. Override as appropriate. 214 virtual bool is_maximal_no_gc() const { 215 return _virtual_space.uncommitted_size() == 0; 216 } 217 218 MemRegion reserved() const { return _reserved; } 219 220 // Returns a region guaranteed to contain all the objects in the 221 // generation. 222 virtual MemRegion used_region() const { return _reserved; } 223 224 MemRegion prev_used_region() const { return _prev_used_region; } 225 virtual void save_used_region() { _prev_used_region = used_region(); } 226 227 // Returns "TRUE" iff "p" points into the committed areas in the generation. 228 // For some kinds of generations, this may be an expensive operation. 229 // To avoid performance problems stemming from its inadvertent use in 230 // product jvm's, we restrict its use to assertion checking or 231 // verification only. 232 virtual bool is_in(const void* p) const; 233 234 /* Returns "TRUE" iff "p" points into the reserved area of the generation. */ 235 bool is_in_reserved(const void* p) const { 236 return _reserved.contains(p); 237 } 238 239 // Check that the generation kind is DefNewGeneration or a sub 240 // class of DefNewGeneration and return a DefNewGeneration* 241 DefNewGeneration* as_DefNewGeneration(); 242 243 // If some space in the generation contains the given "addr", return a 244 // pointer to that space, else return "NULL". 245 virtual Space* space_containing(const void* addr) const; 246 247 // Iteration - do not use for time critical operations 248 virtual void space_iterate(SpaceClosure* blk, bool usedOnly = false) = 0; 249 250 // Returns the first space, if any, in the generation that can participate 251 // in compaction, or else "NULL". 252 virtual CompactibleSpace* first_compaction_space() const = 0; 253 254 // Returns "true" iff this generation should be used to allocate an 255 // object of the given size. Young generations might 256 // wish to exclude very large objects, for example, since, if allocated 257 // often, they would greatly increase the frequency of young-gen 258 // collection. 259 virtual bool should_allocate(size_t word_size, bool is_tlab) { 260 bool result = false; 261 size_t overflow_limit = (size_t)1 << (BitsPerSize_t - LogHeapWordSize); 262 if (!is_tlab || supports_tlab_allocation()) { 263 result = (word_size > 0) && (word_size < overflow_limit); 264 } 265 return result; 266 } 267 268 // Allocate and returns a block of the requested size, or returns "NULL". 269 // Assumes the caller has done any necessary locking. 270 virtual HeapWord* allocate(size_t word_size, bool is_tlab) = 0; 271 272 // Like "allocate", but performs any necessary locking internally. 273 virtual HeapWord* par_allocate(size_t word_size, bool is_tlab) = 0; 274 275 // A 'younger' gen has reached an allocation limit, and uses this to notify 276 // the next older gen. The return value is a new limit, or NULL if none. The 277 // caller must do the necessary locking. 278 virtual HeapWord* allocation_limit_reached(Space* space, HeapWord* top, 279 size_t word_size) { 280 return NULL; 281 } 282 283 // Some generation may offer a region for shared, contiguous allocation, 284 // via inlined code (by exporting the address of the top and end fields 285 // defining the extent of the contiguous allocation region.) 286 287 // This function returns "true" iff the heap supports this kind of 288 // allocation. (More precisely, this means the style of allocation that 289 // increments *top_addr()" with a CAS.) (Default is "no".) 290 // A generation that supports this allocation style must use lock-free 291 // allocation for *all* allocation, since there are times when lock free 292 // allocation will be concurrent with plain "allocate" calls. 293 virtual bool supports_inline_contig_alloc() const { return false; } 294 295 // These functions return the addresses of the fields that define the 296 // boundaries of the contiguous allocation area. (These fields should be 297 // physically near to one another.) 298 virtual HeapWord** top_addr() const { return NULL; } 299 virtual HeapWord** end_addr() const { return NULL; } 300 301 // Thread-local allocation buffers 302 virtual bool supports_tlab_allocation() const { return false; } 303 virtual size_t tlab_capacity() const { 304 guarantee(false, "Generation doesn't support thread local allocation buffers"); 305 return 0; 306 } 307 virtual size_t tlab_used() const { 308 guarantee(false, "Generation doesn't support thread local allocation buffers"); 309 return 0; 310 } 311 virtual size_t unsafe_max_tlab_alloc() const { 312 guarantee(false, "Generation doesn't support thread local allocation buffers"); 313 return 0; 314 } 315 316 // "obj" is the address of an object in a younger generation. Allocate space 317 // for "obj" in the current (or some higher) generation, and copy "obj" into 318 // the newly allocated space, if possible, returning the result (or NULL if 319 // the allocation failed). 320 // 321 // The "obj_size" argument is just obj->size(), passed along so the caller can 322 // avoid repeating the virtual call to retrieve it. 323 virtual oop promote(oop obj, size_t obj_size); 324 325 // Thread "thread_num" (0 <= i < ParalleGCThreads) wants to promote 326 // object "obj", whose original mark word was "m", and whose size is 327 // "word_sz". If possible, allocate space for "obj", copy obj into it 328 // (taking care to copy "m" into the mark word when done, since the mark 329 // word of "obj" may have been overwritten with a forwarding pointer, and 330 // also taking care to copy the klass pointer *last*. Returns the new 331 // object if successful, or else NULL. 332 virtual oop par_promote(int thread_num, 333 oop obj, markOop m, size_t word_sz); 334 335 // Undo, if possible, the most recent par_promote_alloc allocation by 336 // "thread_num" ("obj", of "word_sz"). 337 virtual void par_promote_alloc_undo(int thread_num, 338 HeapWord* obj, size_t word_sz); 339 340 // Informs the current generation that all par_promote_alloc's in the 341 // collection have been completed; any supporting data structures can be 342 // reset. Default is to do nothing. 343 virtual void par_promote_alloc_done(int thread_num) {} 344 345 // Informs the current generation that all oop_since_save_marks_iterates 346 // performed by "thread_num" in the current collection, if any, have been 347 // completed; any supporting data structures can be reset. Default is to 348 // do nothing. 349 virtual void par_oop_since_save_marks_iterate_done(int thread_num) {} 350 351 // This generation will collect all younger generations 352 // during a full collection. 353 virtual bool full_collects_younger_generations() const { return false; } 354 355 // This generation does in-place marking, meaning that mark words 356 // are mutated during the marking phase and presumably reinitialized 357 // to a canonical value after the GC. This is currently used by the 358 // biased locking implementation to determine whether additional 359 // work is required during the GC prologue and epilogue. 360 virtual bool performs_in_place_marking() const { return true; } 361 362 // Returns "true" iff collect() should subsequently be called on this 363 // this generation. See comment below. 364 // This is a generic implementation which can be overridden. 365 // 366 // Note: in the current (1.4) implementation, when genCollectedHeap's 367 // incremental_collection_will_fail flag is set, all allocations are 368 // slow path (the only fast-path place to allocate is DefNew, which 369 // will be full if the flag is set). 370 // Thus, older generations which collect younger generations should 371 // test this flag and collect if it is set. 372 virtual bool should_collect(bool full, 373 size_t word_size, 374 bool is_tlab) { 375 return (full || should_allocate(word_size, is_tlab)); 376 } 377 378 // Returns true if the collection is likely to be safely 379 // completed. Even if this method returns true, a collection 380 // may not be guaranteed to succeed, and the system should be 381 // able to safely unwind and recover from that failure, albeit 382 // at some additional cost. 383 virtual bool collection_attempt_is_safe() { 384 guarantee(false, "Are you sure you want to call this method?"); 385 return true; 386 } 387 388 // Perform a garbage collection. 389 // If full is true attempt a full garbage collection of this generation. 390 // Otherwise, attempting to (at least) free enough space to support an 391 // allocation of the given "word_size". 392 virtual void collect(bool full, 393 bool clear_all_soft_refs, 394 size_t word_size, 395 bool is_tlab) = 0; 396 397 // Perform a heap collection, attempting to create (at least) enough 398 // space to support an allocation of the given "word_size". If 399 // successful, perform the allocation and return the resulting 400 // "oop" (initializing the allocated block). If the allocation is 401 // still unsuccessful, return "NULL". 402 virtual HeapWord* expand_and_allocate(size_t word_size, 403 bool is_tlab, 404 bool parallel = false) = 0; 405 406 // Some generations may require some cleanup or preparation actions before 407 // allowing a collection. The default is to do nothing. 408 virtual void gc_prologue(bool full) {}; 409 410 // Some generations may require some cleanup actions after a collection. 411 // The default is to do nothing. 412 virtual void gc_epilogue(bool full) {}; 413 414 // Save the high water marks for the used space in a generation. 415 virtual void record_spaces_top() {}; 416 417 // Some generations may need to be "fixed-up" after some allocation 418 // activity to make them parsable again. The default is to do nothing. 419 virtual void ensure_parsability() {}; 420 421 // Time (in ms) when we were last collected or now if a collection is 422 // in progress. 423 virtual jlong time_of_last_gc(jlong now) { 424 // Both _time_of_last_gc and now are set using a time source 425 // that guarantees monotonically non-decreasing values provided 426 // the underlying platform provides such a source. So we still 427 // have to guard against non-monotonicity. 428 NOT_PRODUCT( 429 if (now < _time_of_last_gc) { 430 warning("time warp: "INT64_FORMAT" to "INT64_FORMAT, (int64_t)_time_of_last_gc, (int64_t)now); 431 } 432 ) 433 return _time_of_last_gc; 434 } 435 436 virtual void update_time_of_last_gc(jlong now) { 437 _time_of_last_gc = now; 438 } 439 440 // Generations may keep statistics about collection. This 441 // method updates those statistics. current_level is 442 // the level of the collection that has most recently 443 // occurred. This allows the generation to decide what 444 // statistics are valid to collect. For example, the 445 // generation can decide to gather the amount of promoted data 446 // if the collection of the younger generations has completed. 447 GCStats* gc_stats() const { return _gc_stats; } 448 virtual void update_gc_stats(int current_level, bool full) {} 449 450 // Mark sweep support phase2 451 virtual void prepare_for_compaction(CompactPoint* cp); 452 // Mark sweep support phase3 453 virtual void adjust_pointers(); 454 // Mark sweep support phase4 455 virtual void compact(); 456 virtual void post_compact() {ShouldNotReachHere();} 457 458 // Support for CMS's rescan. In this general form we return a pointer 459 // to an abstract object that can be used, based on specific previously 460 // decided protocols, to exchange information between generations, 461 // information that may be useful for speeding up certain types of 462 // garbage collectors. A NULL value indicates to the client that 463 // no data recording is expected by the provider. The data-recorder is 464 // expected to be GC worker thread-local, with the worker index 465 // indicated by "thr_num". 466 virtual void* get_data_recorder(int thr_num) { return NULL; } 467 virtual void sample_eden_chunk() {} 468 469 // Some generations may require some cleanup actions before allowing 470 // a verification. 471 virtual void prepare_for_verify() {}; 472 473 // Accessing "marks". 474 475 // This function gives a generation a chance to note a point between 476 // collections. For example, a contiguous generation might note the 477 // beginning allocation point post-collection, which might allow some later 478 // operations to be optimized. 479 virtual void save_marks() {} 480 481 // This function allows generations to initialize any "saved marks". That 482 // is, should only be called when the generation is empty. 483 virtual void reset_saved_marks() {} 484 485 // This function is "true" iff any no allocations have occurred in the 486 // generation since the last call to "save_marks". 487 virtual bool no_allocs_since_save_marks() = 0; 488 489 // ...and specializations for de-virtualization. (The general 490 // implementation of the _nv versions call the virtual version. 491 // Note that the _nv suffix is not really semantically necessary, 492 // but it avoids some not-so-useful warnings on Solaris.) 493 template <typename OopClosureType> 494 void oop_since_save_marks_iterate(OopClosureType* cl); 495 496 template <bool nv, typename OopClosureType> 497 void oop_since_save_marks_iterate_disp(OopClosureType* cl); 498 499 // The "requestor" generation is performing some garbage collection 500 // action for which it would be useful to have scratch space. If 501 // the target is not the requestor, no gc actions will be required 502 // of the target. The requestor promises to allocate no more than 503 // "max_alloc_words" in the target generation (via promotion say, 504 // if the requestor is a young generation and the target is older). 505 // If the target generation can provide any scratch space, it adds 506 // it to "list", leaving "list" pointing to the head of the 507 // augmented list. The default is to offer no space. 508 virtual void contribute_scratch(ScratchBlock*& list, Generation* requestor, 509 size_t max_alloc_words) {} 510 511 // Give each generation an opportunity to do clean up for any 512 // contributed scratch. 513 virtual void reset_scratch() {}; 514 515 // When an older generation has been collected, and perhaps resized, 516 // this method will be invoked on all younger generations (from older to 517 // younger), allowing them to resize themselves as appropriate. 518 virtual void compute_new_size() = 0; 519 520 // Printing 521 virtual const char* name() const = 0; 522 virtual const char* short_name() const = 0; 523 524 int level() const { return _level; } 525 526 // Attributes 527 528 // True iff the given generation may only be the youngest generation. 529 virtual bool must_be_youngest() const = 0; 530 // True iff the given generation may only be the oldest generation. 531 virtual bool must_be_oldest() const = 0; 532 533 // Reference Processing accessor 534 ReferenceProcessor* const ref_processor() { return _ref_processor; } 535 536 // Iteration. 537 538 // Iterate over all the ref-containing fields of all objects in the 539 // generation, calling "cl.do_oop" on each. 540 virtual void oop_iterate(ExtendedOopClosure* cl); 541 542 // Iterate over all objects in the generation, calling "cl.do_object" on 543 // each. 544 virtual void object_iterate(ObjectClosure* cl); 545 546 // Iterate over all safe objects in the generation, calling "cl.do_object" on 547 // each. An object is safe if its references point to other objects in 548 // the heap. This defaults to object_iterate() unless overridden. 549 virtual void safe_object_iterate(ObjectClosure* cl); 550 551 // Apply "cl->do_oop" to (the address of) all and only all the ref fields 552 // in the current generation that contain pointers to objects in younger 553 // generations. Objects allocated since the last "save_marks" call are 554 // excluded. 555 virtual void younger_refs_iterate(OopsInGenClosure* cl) = 0; 556 557 // Inform a generation that it longer contains references to objects 558 // in any younger generation. [e.g. Because younger gens are empty, 559 // clear the card table.] 560 virtual void clear_remembered_set() { } 561 562 // Inform a generation that some of its objects have moved. [e.g. The 563 // generation's spaces were compacted, invalidating the card table.] 564 virtual void invalidate_remembered_set() { } 565 566 // Block abstraction. 567 568 // Returns the address of the start of the "block" that contains the 569 // address "addr". We say "blocks" instead of "object" since some heaps 570 // may not pack objects densely; a chunk may either be an object or a 571 // non-object. 572 virtual HeapWord* block_start(const void* addr) const; 573 574 // Requires "addr" to be the start of a chunk, and returns its size. 575 // "addr + size" is required to be the start of a new chunk, or the end 576 // of the active area of the heap. 577 virtual size_t block_size(const HeapWord* addr) const ; 578 579 // Requires "addr" to be the start of a block, and returns "TRUE" iff 580 // the block is an object. 581 virtual bool block_is_obj(const HeapWord* addr) const; 582 583 584 // PrintGC, PrintGCDetails support 585 void print_heap_change(size_t prev_used) const; 586 587 // PrintHeapAtGC support 588 virtual void print() const; 589 virtual void print_on(outputStream* st) const; 590 591 virtual void verify() = 0; 592 593 struct StatRecord { 594 int invocations; 595 elapsedTimer accumulated_time; 596 StatRecord() : 597 invocations(0), 598 accumulated_time(elapsedTimer()) {} 599 }; 600 private: 601 StatRecord _stat_record; 602 public: 603 StatRecord* stat_record() { return &_stat_record; } 604 605 virtual void print_summary_info(); 606 virtual void print_summary_info_on(outputStream* st); 607 608 // Performance Counter support 609 virtual void update_counters() = 0; 610 virtual CollectorCounters* counters() { return _gc_counters; } 611 }; 612 613 // Class CardGeneration is a generation that is covered by a card table, 614 // and uses a card-size block-offset array to implement block_start. 615 616 // class BlockOffsetArray; 617 // class BlockOffsetArrayContigSpace; 618 class BlockOffsetSharedArray; 619 620 class CardGeneration: public Generation { 621 friend class VMStructs; 622 protected: 623 // This is shared with other generations. 624 GenRemSet* _rs; 625 // This is local to this generation. 626 BlockOffsetSharedArray* _bts; 627 628 // current shrinking effect: this damps shrinking when the heap gets empty. 629 size_t _shrink_factor; 630 631 size_t _min_heap_delta_bytes; // Minimum amount to expand. 632 633 // Some statistics from before gc started. 634 // These are gathered in the gc_prologue (and should_collect) 635 // to control growing/shrinking policy in spite of promotions. 636 size_t _capacity_at_prologue; 637 size_t _used_at_prologue; 638 639 CardGeneration(ReservedSpace rs, size_t initial_byte_size, int level, 640 GenRemSet* remset, jbyte dispatch_index); 641 642 public: 643 644 // Attempt to expand the generation by "bytes". Expand by at a 645 // minimum "expand_bytes". Return true if some amount (not 646 // necessarily the full "bytes") was done. 647 virtual bool expand(size_t bytes, size_t expand_bytes); 648 649 // Shrink generation with specified size (returns false if unable to shrink) 650 virtual void shrink(size_t bytes) = 0; 651 652 virtual void compute_new_size(); 653 654 virtual void clear_remembered_set(); 655 656 virtual void invalidate_remembered_set(); 657 658 virtual void prepare_for_verify(); 659 660 // Grow generation with specified size (returns false if unable to grow) 661 virtual bool grow_by(size_t bytes) = 0; 662 // Grow generation to reserved size. 663 virtual bool grow_to_reserved() = 0; 664 }; 665 666 // OneContigSpaceCardGeneration models a heap of old objects contained in a single 667 // contiguous space. 668 // 669 // Garbage collection is performed using mark-compact. 670 671 class OneContigSpaceCardGeneration: public CardGeneration { 672 friend class VMStructs; 673 // Abstractly, this is a subtype that gets access to protected fields. 674 friend class VM_PopulateDumpSharedSpace; 675 676 protected: 677 ContiguousSpace* _the_space; // actual space holding objects 678 WaterMark _last_gc; // watermark between objects allocated before 679 // and after last GC. 680 681 // Grow generation with specified size (returns false if unable to grow) 682 virtual bool grow_by(size_t bytes); 683 // Grow generation to reserved size. 684 virtual bool grow_to_reserved(); 685 // Shrink generation with specified size (returns false if unable to shrink) 686 void shrink_by(size_t bytes); 687 688 // Allocation failure 689 virtual bool expand(size_t bytes, size_t expand_bytes); 690 void shrink(size_t bytes); 691 692 // Accessing spaces 693 ContiguousSpace* the_space() const { return _the_space; } 694 695 public: 696 OneContigSpaceCardGeneration(ReservedSpace rs, size_t initial_byte_size, 697 int level, GenRemSet* remset, 698 ContiguousSpace* space) : 699 CardGeneration(rs, initial_byte_size, level, remset, _dispatch_index_generation_one_contig), 700 _the_space(space) 701 {} 702 703 inline bool is_in(const void* p) const; 704 705 // Space enquiries 706 size_t capacity() const; 707 size_t used() const; 708 size_t free() const; 709 710 MemRegion used_region() const; 711 712 size_t unsafe_max_alloc_nogc() const; 713 size_t contiguous_available() const; 714 715 // Iteration 716 void object_iterate(ObjectClosure* blk); 717 void space_iterate(SpaceClosure* blk, bool usedOnly = false); 718 719 void younger_refs_iterate(OopsInGenClosure* blk); 720 721 inline CompactibleSpace* first_compaction_space() const; 722 723 virtual inline HeapWord* allocate(size_t word_size, bool is_tlab); 724 virtual inline HeapWord* par_allocate(size_t word_size, bool is_tlab); 725 726 // Accessing marks 727 inline WaterMark top_mark(); 728 inline WaterMark bottom_mark(); 729 730 template <bool nv, typename OopClosureType> 731 void oop_since_save_marks_iterate(OopClosureType* cl); 732 733 void save_marks(); 734 void reset_saved_marks(); 735 bool no_allocs_since_save_marks(); 736 737 inline size_t block_size(const HeapWord* addr) const; 738 739 inline bool block_is_obj(const HeapWord* addr) const; 740 741 virtual void collect(bool full, 742 bool clear_all_soft_refs, 743 size_t size, 744 bool is_tlab); 745 HeapWord* expand_and_allocate(size_t size, 746 bool is_tlab, 747 bool parallel = false); 748 749 virtual void prepare_for_verify(); 750 751 virtual void gc_epilogue(bool full); 752 753 virtual void record_spaces_top(); 754 755 virtual void verify(); 756 virtual void print_on(outputStream* st) const; 757 }; 758 759 #endif // SHARE_VM_MEMORY_GENERATION_HPP