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