1 /* 2 * Copyright (c) 1997, 2012, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #ifndef SHARE_VM_MEMORY_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 ASParNew, 135 ASConcurrentMarkSweep, 136 DefNew, 137 ParNew, 138 MarkSweepCompact, 139 ConcurrentMarkSweep, 140 Other 141 }; 142 143 enum SomePublicConstants { 144 // Generations are GenGrain-aligned and have size that are multiples of 145 // GenGrain. 146 // Note: on ARM we add 1 bit for card_table_base to be properly aligned 147 // (we expect its low byte to be zero - see implementation of post_barrier) 148 LogOfGenGrain = 16 ARM_ONLY(+1), 149 GenGrain = 1 << LogOfGenGrain 150 }; 151 152 // allocate and initialize ("weak") refs processing support 153 virtual void ref_processor_init(); 154 void set_ref_processor(ReferenceProcessor* rp) { 155 assert(_ref_processor == NULL, "clobbering existing _ref_processor"); 156 _ref_processor = rp; 157 } 158 159 virtual Generation::Name kind() { return Generation::Other; } 160 GenerationSpec* spec(); 161 162 // This properly belongs in the collector, but for now this 163 // will do. 164 virtual bool refs_discovery_is_atomic() const { return true; } 165 virtual bool refs_discovery_is_mt() const { return false; } 166 167 // Space enquiries (results in bytes) 168 virtual size_t capacity() const = 0; // The maximum number of object bytes the 169 // generation can currently hold. 170 virtual size_t used() const = 0; // The number of used bytes in the gen. 171 virtual size_t free() const = 0; // The number of free bytes in the gen. 172 173 // Support for java.lang.Runtime.maxMemory(); see CollectedHeap. 174 // Returns the total number of bytes available in a generation 175 // for the allocation of objects. 176 virtual size_t max_capacity() const; 177 178 // If this is a young generation, the maximum number of bytes that can be 179 // allocated in this generation before a GC is triggered. 180 virtual size_t capacity_before_gc() const { return 0; } 181 182 // The largest number of contiguous free bytes in the generation, 183 // including expansion (Assumes called at a safepoint.) 184 virtual size_t contiguous_available() const = 0; 185 // The largest number of contiguous free bytes in this or any higher generation. 186 virtual size_t max_contiguous_available() const; 187 188 // Returns true if promotions of the specified amount are 189 // likely to succeed without a promotion failure. 190 // Promotion of the full amount is not guaranteed but 191 // might be attempted in the worst case. 192 virtual bool promotion_attempt_is_safe(size_t max_promotion_in_bytes) const; 193 194 // For a non-young generation, this interface can be used to inform a 195 // generation that a promotion attempt into that generation failed. 196 // Typically used to enable diagnostic output for post-mortem analysis, 197 // but other uses of the interface are not ruled out. 198 virtual void promotion_failure_occurred() { /* does nothing */ } 199 200 // Return an estimate of the maximum allocation that could be performed 201 // in the generation without triggering any collection or expansion 202 // activity. It is "unsafe" because no locks are taken; the result 203 // should be treated as an approximation, not a guarantee, for use in 204 // heuristic resizing decisions. 205 virtual size_t unsafe_max_alloc_nogc() const = 0; 206 207 // Returns true if this generation cannot be expanded further 208 // without a GC. Override as appropriate. 209 virtual bool is_maximal_no_gc() const { 210 return _virtual_space.uncommitted_size() == 0; 211 } 212 213 MemRegion reserved() const { return _reserved; } 214 215 // Returns a region guaranteed to contain all the objects in the 216 // generation. 217 virtual MemRegion used_region() const { return _reserved; } 218 219 MemRegion prev_used_region() const { return _prev_used_region; } 220 virtual void save_used_region() { _prev_used_region = used_region(); } 221 222 // Returns "TRUE" iff "p" points into the committed areas in the generation. 223 // For some kinds of generations, this may be an expensive operation. 224 // To avoid performance problems stemming from its inadvertent use in 225 // product jvm's, we restrict its use to assertion checking or 226 // verification only. 227 virtual bool is_in(const void* p) const; 228 229 /* Returns "TRUE" iff "p" points into the reserved area of the generation. */ 230 bool is_in_reserved(const void* p) const { 231 return _reserved.contains(p); 232 } 233 234 // Check that the generation kind is DefNewGeneration or a sub 235 // class of DefNewGeneration and return a DefNewGeneration* 236 DefNewGeneration* as_DefNewGeneration(); 237 238 // If some space in the generation contains the given "addr", return a 239 // pointer to that space, else return "NULL". 240 virtual Space* space_containing(const void* addr) const; 241 242 // Iteration - do not use for time critical operations 243 virtual void space_iterate(SpaceClosure* blk, bool usedOnly = false) = 0; 244 245 // Returns the first space, if any, in the generation that can participate 246 // in compaction, or else "NULL". 247 virtual CompactibleSpace* first_compaction_space() const = 0; 248 249 // Returns "true" iff this generation should be used to allocate an 250 // object of the given size. Young generations might 251 // wish to exclude very large objects, for example, since, if allocated 252 // often, they would greatly increase the frequency of young-gen 253 // collection. 254 virtual bool should_allocate(size_t word_size, bool is_tlab) { 255 bool result = false; 256 size_t overflow_limit = (size_t)1 << (BitsPerSize_t - LogHeapWordSize); 257 if (!is_tlab || supports_tlab_allocation()) { 258 result = (word_size > 0) && (word_size < overflow_limit); 259 } 260 return result; 261 } 262 263 // Allocate and returns a block of the requested size, or returns "NULL". 264 // Assumes the caller has done any necessary locking. 265 virtual HeapWord* allocate(size_t word_size, bool is_tlab) = 0; 266 267 // Like "allocate", but performs any necessary locking internally. 268 virtual HeapWord* par_allocate(size_t word_size, bool is_tlab) = 0; 269 270 // A 'younger' gen has reached an allocation limit, and uses this to notify 271 // the next older gen. The return value is a new limit, or NULL if none. The 272 // caller must do the necessary locking. 273 virtual HeapWord* allocation_limit_reached(Space* space, HeapWord* top, 274 size_t word_size) { 275 return NULL; 276 } 277 278 // Some generation may offer a region for shared, contiguous allocation, 279 // via inlined code (by exporting the address of the top and end fields 280 // defining the extent of the contiguous allocation region.) 281 282 // This function returns "true" iff the heap supports this kind of 283 // allocation. (More precisely, this means the style of allocation that 284 // increments *top_addr()" with a CAS.) (Default is "no".) 285 // A generation that supports this allocation style must use lock-free 286 // allocation for *all* allocation, since there are times when lock free 287 // allocation will be concurrent with plain "allocate" calls. 288 virtual bool supports_inline_contig_alloc() const { return false; } 289 290 // These functions return the addresses of the fields that define the 291 // boundaries of the contiguous allocation area. (These fields should be 292 // physicall near to one another.) 293 virtual HeapWord** top_addr() const { return NULL; } 294 virtual HeapWord** end_addr() const { return NULL; } 295 296 // Thread-local allocation buffers 297 virtual bool supports_tlab_allocation() const { return false; } 298 virtual size_t tlab_capacity() const { 299 guarantee(false, "Generation doesn't support thread local allocation buffers"); 300 return 0; 301 } 302 virtual size_t unsafe_max_tlab_alloc() const { 303 guarantee(false, "Generation doesn't support thread local allocation buffers"); 304 return 0; 305 } 306 307 // "obj" is the address of an object in a younger generation. Allocate space 308 // for "obj" in the current (or some higher) generation, and copy "obj" into 309 // the newly allocated space, if possible, returning the result (or NULL if 310 // the allocation failed). 311 // 312 // The "obj_size" argument is just obj->size(), passed along so the caller can 313 // avoid repeating the virtual call to retrieve it. 314 virtual oop promote(oop obj, size_t obj_size); 315 316 // Thread "thread_num" (0 <= i < ParalleGCThreads) wants to promote 317 // object "obj", whose original mark word was "m", and whose size is 318 // "word_sz". If possible, allocate space for "obj", copy obj into it 319 // (taking care to copy "m" into the mark word when done, since the mark 320 // word of "obj" may have been overwritten with a forwarding pointer, and 321 // also taking care to copy the klass pointer *last*. Returns the new 322 // object if successful, or else NULL. 323 virtual oop par_promote(int thread_num, 324 oop obj, markOop m, size_t word_sz); 325 326 // Undo, if possible, the most recent par_promote_alloc allocation by 327 // "thread_num" ("obj", of "word_sz"). 328 virtual void par_promote_alloc_undo(int thread_num, 329 HeapWord* obj, size_t word_sz); 330 331 // Informs the current generation that all par_promote_alloc's in the 332 // collection have been completed; any supporting data structures can be 333 // reset. Default is to do nothing. 334 virtual void par_promote_alloc_done(int thread_num) {} 335 336 // Informs the current generation that all oop_since_save_marks_iterates 337 // performed by "thread_num" in the current collection, if any, have been 338 // completed; any supporting data structures can be reset. Default is to 339 // do nothing. 340 virtual void par_oop_since_save_marks_iterate_done(int thread_num) {} 341 342 // This generation will collect all younger generations 343 // during a full collection. 344 virtual bool full_collects_younger_generations() const { return false; } 345 346 // This generation does in-place marking, meaning that mark words 347 // are mutated during the marking phase and presumably reinitialized 348 // to a canonical value after the GC. This is currently used by the 349 // biased locking implementation to determine whether additional 350 // work is required during the GC prologue and epilogue. 351 virtual bool performs_in_place_marking() const { return true; } 352 353 // Returns "true" iff collect() should subsequently be called on this 354 // this generation. See comment below. 355 // This is a generic implementation which can be overridden. 356 // 357 // Note: in the current (1.4) implementation, when genCollectedHeap's 358 // incremental_collection_will_fail flag is set, all allocations are 359 // slow path (the only fast-path place to allocate is DefNew, which 360 // will be full if the flag is set). 361 // Thus, older generations which collect younger generations should 362 // test this flag and collect if it is set. 363 virtual bool should_collect(bool full, 364 size_t word_size, 365 bool is_tlab) { 366 return (full || should_allocate(word_size, is_tlab)); 367 } 368 369 // Returns true if the collection is likely to be safely 370 // completed. Even if this method returns true, a collection 371 // may not be guaranteed to succeed, and the system should be 372 // able to safely unwind and recover from that failure, albeit 373 // at some additional cost. 374 virtual bool collection_attempt_is_safe() { 375 guarantee(false, "Are you sure you want to call this method?"); 376 return true; 377 } 378 379 // Perform a garbage collection. 380 // If full is true attempt a full garbage collection of this generation. 381 // Otherwise, attempting to (at least) free enough space to support an 382 // allocation of the given "word_size". 383 virtual void collect(bool full, 384 bool clear_all_soft_refs, 385 size_t word_size, 386 bool is_tlab) = 0; 387 388 // Perform a heap collection, attempting to create (at least) enough 389 // space to support an allocation of the given "word_size". If 390 // successful, perform the allocation and return the resulting 391 // "oop" (initializing the allocated block). If the allocation is 392 // still unsuccessful, return "NULL". 393 virtual HeapWord* expand_and_allocate(size_t word_size, 394 bool is_tlab, 395 bool parallel = false) = 0; 396 397 // Some generations may require some cleanup or preparation actions before 398 // allowing a collection. The default is to do nothing. 399 virtual void gc_prologue(bool full) {}; 400 401 // Some generations may require some cleanup actions after a collection. 402 // The default is to do nothing. 403 virtual void gc_epilogue(bool full) {}; 404 405 // Save the high water marks for the used space in a generation. 406 virtual void record_spaces_top() {}; 407 408 // Some generations may need to be "fixed-up" after some allocation 409 // activity to make them parsable again. The default is to do nothing. 410 virtual void ensure_parsability() {}; 411 412 // Time (in ms) when we were last collected or now if a collection is 413 // in progress. 414 virtual jlong time_of_last_gc(jlong now) { 415 // Both _time_of_last_gc and now are set using a time source 416 // that guarantees monotonically non-decreasing values provided 417 // the underlying platform provides such a source. So we still 418 // have to guard against non-monotonicity. 419 NOT_PRODUCT( 420 if (now < _time_of_last_gc) { 421 warning("time warp: "INT64_FORMAT" to "INT64_FORMAT, _time_of_last_gc, now); 422 } 423 ) 424 return _time_of_last_gc; 425 } 426 427 virtual void update_time_of_last_gc(jlong now) { 428 _time_of_last_gc = now; 429 } 430 431 // Generations may keep statistics about collection. This 432 // method updates those statistics. current_level is 433 // the level of the collection that has most recently 434 // occurred. This allows the generation to decide what 435 // statistics are valid to collect. For example, the 436 // generation can decide to gather the amount of promoted data 437 // if the collection of the younger generations has completed. 438 GCStats* gc_stats() const { return _gc_stats; } 439 virtual void update_gc_stats(int current_level, bool full) {} 440 441 // Mark sweep support phase2 442 virtual void prepare_for_compaction(CompactPoint* cp); 443 // Mark sweep support phase3 444 virtual void adjust_pointers(); 445 // Mark sweep support phase4 446 virtual void compact(); 447 virtual void post_compact() {ShouldNotReachHere();} 448 449 // Support for CMS's rescan. In this general form we return a pointer 450 // to an abstract object that can be used, based on specific previously 451 // decided protocols, to exchange information between generations, 452 // information that may be useful for speeding up certain types of 453 // garbage collectors. A NULL value indicates to the client that 454 // no data recording is expected by the provider. The data-recorder is 455 // expected to be GC worker thread-local, with the worker index 456 // indicated by "thr_num". 457 virtual void* get_data_recorder(int thr_num) { return NULL; } 458 459 // Some generations may require some cleanup actions before allowing 460 // a verification. 461 virtual void prepare_for_verify() {}; 462 463 // Accessing "marks". 464 465 // This function gives a generation a chance to note a point between 466 // collections. For example, a contiguous generation might note the 467 // beginning allocation point post-collection, which might allow some later 468 // operations to be optimized. 469 virtual void save_marks() {} 470 471 // This function allows generations to initialize any "saved marks". That 472 // is, should only be called when the generation is empty. 473 virtual void reset_saved_marks() {} 474 475 // This function is "true" iff any no allocations have occurred in the 476 // generation since the last call to "save_marks". 477 virtual bool no_allocs_since_save_marks() = 0; 478 479 // Apply "cl->apply" to (the addresses of) all reference fields in objects 480 // allocated in the current generation since the last call to "save_marks". 481 // If more objects are allocated in this generation as a result of applying 482 // the closure, iterates over reference fields in those objects as well. 483 // Calls "save_marks" at the end of the iteration. 484 // General signature... 485 virtual void oop_since_save_marks_iterate_v(OopsInGenClosure* cl) = 0; 486 // ...and specializations for de-virtualization. (The general 487 // implemention of the _nv versions call the virtual version. 488 // Note that the _nv suffix is not really semantically necessary, 489 // but it avoids some not-so-useful warnings on Solaris.) 490 #define Generation_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \ 491 virtual void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \ 492 oop_since_save_marks_iterate_v((OopsInGenClosure*)cl); \ 493 } 494 SPECIALIZED_SINCE_SAVE_MARKS_CLOSURES(Generation_SINCE_SAVE_MARKS_DECL) 495 496 #undef Generation_SINCE_SAVE_MARKS_DECL 497 498 // The "requestor" generation is performing some garbage collection 499 // action for which it would be useful to have scratch space. If 500 // the target is not the requestor, no gc actions will be required 501 // of the target. The requestor promises to allocate no more than 502 // "max_alloc_words" in the target generation (via promotion say, 503 // if the requestor is a young generation and the target is older). 504 // If the target generation can provide any scratch space, it adds 505 // it to "list", leaving "list" pointing to the head of the 506 // augmented list. The default is to offer no space. 507 virtual void contribute_scratch(ScratchBlock*& list, Generation* requestor, 508 size_t max_alloc_words) {} 509 510 // Give each generation an opportunity to do clean up for any 511 // contributed scratch. 512 virtual void reset_scratch() {}; 513 514 // When an older generation has been collected, and perhaps resized, 515 // this method will be invoked on all younger generations (from older to 516 // younger), allowing them to resize themselves as appropriate. 517 virtual void compute_new_size() = 0; 518 519 // Printing 520 virtual const char* name() const = 0; 521 virtual const char* short_name() const = 0; 522 523 int level() const { return _level; } 524 525 // Attributes 526 527 // True iff the given generation may only be the youngest generation. 528 virtual bool must_be_youngest() const = 0; 529 // True iff the given generation may only be the oldest generation. 530 virtual bool must_be_oldest() const = 0; 531 532 // Reference Processing accessor 533 ReferenceProcessor* const ref_processor() { return _ref_processor; } 534 535 // Iteration. 536 537 // Iterate over all the ref-containing fields of all objects in the 538 // generation, calling "cl.do_oop" on each. 539 virtual void oop_iterate(ExtendedOopClosure* cl); 540 541 // Same as above, restricted to the intersection of a memory region and 542 // the generation. 543 virtual void oop_iterate(MemRegion mr, ExtendedOopClosure* cl); 544 545 // Iterate over all objects in the generation, calling "cl.do_object" on 546 // each. 547 virtual void object_iterate(ObjectClosure* cl); 548 549 // Iterate over all safe objects in the generation, calling "cl.do_object" on 550 // each. An object is safe if its references point to other objects in 551 // the heap. This defaults to object_iterate() unless overridden. 552 virtual void safe_object_iterate(ObjectClosure* cl); 553 554 // Iterate over all objects allocated in the generation since the last 555 // collection, calling "cl.do_object" on each. The generation must have 556 // been initialized properly to support this function, or else this call 557 // will fail. 558 virtual void object_iterate_since_last_GC(ObjectClosure* cl) = 0; 559 560 // Apply "cl->do_oop" to (the address of) all and only all the ref fields 561 // in the current generation that contain pointers to objects in younger 562 // generations. Objects allocated since the last "save_marks" call are 563 // excluded. 564 virtual void younger_refs_iterate(OopsInGenClosure* cl) = 0; 565 566 // Inform a generation that it longer contains references to objects 567 // in any younger generation. [e.g. Because younger gens are empty, 568 // clear the card table.] 569 virtual void clear_remembered_set() { } 570 571 // Inform a generation that some of its objects have moved. [e.g. The 572 // generation's spaces were compacted, invalidating the card table.] 573 virtual void invalidate_remembered_set() { } 574 575 // Block abstraction. 576 577 // Returns the address of the start of the "block" that contains the 578 // address "addr". We say "blocks" instead of "object" since some heaps 579 // may not pack objects densely; a chunk may either be an object or a 580 // non-object. 581 virtual HeapWord* block_start(const void* addr) const; 582 583 // Requires "addr" to be the start of a chunk, and returns its size. 584 // "addr + size" is required to be the start of a new chunk, or the end 585 // of the active area of the heap. 586 virtual size_t block_size(const HeapWord* addr) const ; 587 588 // Requires "addr" to be the start of a block, and returns "TRUE" iff 589 // the block is an object. 590 virtual bool block_is_obj(const HeapWord* addr) const; 591 592 593 // PrintGC, PrintGCDetails support 594 void print_heap_change(size_t prev_used) const; 595 596 // PrintHeapAtGC support 597 virtual void print() const; 598 virtual void print_on(outputStream* st) const; 599 600 virtual void verify() = 0; 601 602 struct StatRecord { 603 int invocations; 604 elapsedTimer accumulated_time; 605 StatRecord() : 606 invocations(0), 607 accumulated_time(elapsedTimer()) {} 608 }; 609 private: 610 StatRecord _stat_record; 611 public: 612 StatRecord* stat_record() { return &_stat_record; } 613 614 virtual void print_summary_info(); 615 virtual void print_summary_info_on(outputStream* st); 616 617 // Performance Counter support 618 virtual void update_counters() = 0; 619 virtual CollectorCounters* counters() { return _gc_counters; } 620 }; 621 622 // Class CardGeneration is a generation that is covered by a card table, 623 // and uses a card-size block-offset array to implement block_start. 624 625 // class BlockOffsetArray; 626 // class BlockOffsetArrayContigSpace; 627 class BlockOffsetSharedArray; 628 629 class CardGeneration: public Generation { 630 friend class VMStructs; 631 protected: 632 // This is shared with other generations. 633 GenRemSet* _rs; 634 // This is local to this generation. 635 BlockOffsetSharedArray* _bts; 636 637 // current shrinking effect: this damps shrinking when the heap gets empty. 638 size_t _shrink_factor; 639 640 size_t _min_heap_delta_bytes; // Minimum amount to expand. 641 642 // Some statistics from before gc started. 643 // These are gathered in the gc_prologue (and should_collect) 644 // to control growing/shrinking policy in spite of promotions. 645 size_t _capacity_at_prologue; 646 size_t _used_at_prologue; 647 648 CardGeneration(ReservedSpace rs, size_t initial_byte_size, int level, 649 GenRemSet* remset); 650 651 public: 652 653 // Attempt to expand the generation by "bytes". Expand by at a 654 // minimum "expand_bytes". Return true if some amount (not 655 // necessarily the full "bytes") was done. 656 virtual bool expand(size_t bytes, size_t expand_bytes); 657 658 // Shrink generation with specified size (returns false if unable to shrink) 659 virtual void shrink(size_t bytes) = 0; 660 661 virtual void compute_new_size(); 662 663 virtual void clear_remembered_set(); 664 665 virtual void invalidate_remembered_set(); 666 667 virtual void prepare_for_verify(); 668 669 // Grow generation with specified size (returns false if unable to grow) 670 virtual bool grow_by(size_t bytes) = 0; 671 // Grow generation to reserved size. 672 virtual bool grow_to_reserved() = 0; 673 }; 674 675 // OneContigSpaceCardGeneration models a heap of old objects contained in a single 676 // contiguous space. 677 // 678 // Garbage collection is performed using mark-compact. 679 680 class OneContigSpaceCardGeneration: public CardGeneration { 681 friend class VMStructs; 682 // Abstractly, this is a subtype that gets access to protected fields. 683 friend class VM_PopulateDumpSharedSpace; 684 685 protected: 686 ContiguousSpace* _the_space; // actual space holding objects 687 WaterMark _last_gc; // watermark between objects allocated before 688 // and after last GC. 689 690 // Grow generation with specified size (returns false if unable to grow) 691 virtual bool grow_by(size_t bytes); 692 // Grow generation to reserved size. 693 virtual bool grow_to_reserved(); 694 // Shrink generation with specified size (returns false if unable to shrink) 695 void shrink_by(size_t bytes); 696 697 // Allocation failure 698 virtual bool expand(size_t bytes, size_t expand_bytes); 699 void shrink(size_t bytes); 700 701 // Accessing spaces 702 ContiguousSpace* the_space() const { return _the_space; } 703 704 public: 705 OneContigSpaceCardGeneration(ReservedSpace rs, size_t initial_byte_size, 706 int level, GenRemSet* remset, 707 ContiguousSpace* space) : 708 CardGeneration(rs, initial_byte_size, level, remset), 709 _the_space(space) 710 {} 711 712 inline bool is_in(const void* p) const; 713 714 // Space enquiries 715 size_t capacity() const; 716 size_t used() const; 717 size_t free() const; 718 719 MemRegion used_region() const; 720 721 size_t unsafe_max_alloc_nogc() const; 722 size_t contiguous_available() const; 723 724 // Iteration 725 void object_iterate(ObjectClosure* blk); 726 void space_iterate(SpaceClosure* blk, bool usedOnly = false); 727 void object_iterate_since_last_GC(ObjectClosure* cl); 728 729 void younger_refs_iterate(OopsInGenClosure* blk); 730 731 inline CompactibleSpace* first_compaction_space() const; 732 733 virtual inline HeapWord* allocate(size_t word_size, bool is_tlab); 734 virtual inline HeapWord* par_allocate(size_t word_size, bool is_tlab); 735 736 // Accessing marks 737 inline WaterMark top_mark(); 738 inline WaterMark bottom_mark(); 739 740 #define OneContig_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \ 741 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl); 742 OneContig_SINCE_SAVE_MARKS_DECL(OopsInGenClosure,_v) 743 SPECIALIZED_SINCE_SAVE_MARKS_CLOSURES(OneContig_SINCE_SAVE_MARKS_DECL) 744 745 void save_marks(); 746 void reset_saved_marks(); 747 bool no_allocs_since_save_marks(); 748 749 inline size_t block_size(const HeapWord* addr) const; 750 751 inline bool block_is_obj(const HeapWord* addr) const; 752 753 virtual void collect(bool full, 754 bool clear_all_soft_refs, 755 size_t size, 756 bool is_tlab); 757 HeapWord* expand_and_allocate(size_t size, 758 bool is_tlab, 759 bool parallel = false); 760 761 virtual void prepare_for_verify(); 762 763 virtual void gc_epilogue(bool full); 764 765 virtual void record_spaces_top(); 766 767 virtual void verify(); 768 virtual void print_on(outputStream* st) const; 769 }; 770 771 #endif // SHARE_VM_MEMORY_GENERATION_HPP