1 /* 2 * Copyright (c) 1997, 2017, 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_GC_SHARED_SPACE_HPP 26 #define SHARE_VM_GC_SHARED_SPACE_HPP 27 28 #include "gc/shared/blockOffsetTable.hpp" 29 #include "gc/shared/cardTableModRefBS.hpp" 30 #include "gc/shared/workgroup.hpp" 31 #include "memory/allocation.hpp" 32 #include "memory/iterator.hpp" 33 #include "memory/memRegion.hpp" 34 #include "oops/markOop.hpp" 35 #include "runtime/mutexLocker.hpp" 36 #include "utilities/align.hpp" 37 #include "utilities/macros.hpp" 38 39 // A space is an abstraction for the "storage units" backing 40 // up the generation abstraction. It includes specific 41 // implementations for keeping track of free and used space, 42 // for iterating over objects and free blocks, etc. 43 44 // Forward decls. 45 class Space; 46 class BlockOffsetArray; 47 class BlockOffsetArrayContigSpace; 48 class Generation; 49 class CompactibleSpace; 50 class BlockOffsetTable; 51 class CardTableRS; 52 class DirtyCardToOopClosure; 53 54 // A Space describes a heap area. Class Space is an abstract 55 // base class. 56 // 57 // Space supports allocation, size computation and GC support is provided. 58 // 59 // Invariant: bottom() and end() are on page_size boundaries and 60 // bottom() <= top() <= end() 61 // top() is inclusive and end() is exclusive. 62 63 class Space: public CHeapObj<mtGC> { 64 friend class VMStructs; 65 protected: 66 HeapWord* _bottom; 67 HeapWord* _end; 68 69 // Used in support of save_marks() 70 HeapWord* _saved_mark_word; 71 72 // A sequential tasks done structure. This supports 73 // parallel GC, where we have threads dynamically 74 // claiming sub-tasks from a larger parallel task. 75 SequentialSubTasksDone _par_seq_tasks; 76 77 Space(): 78 _bottom(NULL), _end(NULL) { } 79 80 public: 81 // Accessors 82 HeapWord* bottom() const { return _bottom; } 83 HeapWord* end() const { return _end; } 84 virtual void set_bottom(HeapWord* value) { _bottom = value; } 85 virtual void set_end(HeapWord* value) { _end = value; } 86 87 virtual HeapWord* saved_mark_word() const { return _saved_mark_word; } 88 89 void set_saved_mark_word(HeapWord* p) { _saved_mark_word = p; } 90 91 // Returns true if this object has been allocated since a 92 // generation's "save_marks" call. 93 virtual bool obj_allocated_since_save_marks(const oop obj) const { 94 return (HeapWord*)obj >= saved_mark_word(); 95 } 96 97 virtual MemRegionClosure* preconsumptionDirtyCardClosure() const { 98 return NULL; 99 } 100 101 // Returns a subregion of the space containing only the allocated objects in 102 // the space. 103 virtual MemRegion used_region() const = 0; 104 105 // Returns a region that is guaranteed to contain (at least) all objects 106 // allocated at the time of the last call to "save_marks". If the space 107 // initializes its DirtyCardToOopClosure's specifying the "contig" option 108 // (that is, if the space is contiguous), then this region must contain only 109 // such objects: the memregion will be from the bottom of the region to the 110 // saved mark. Otherwise, the "obj_allocated_since_save_marks" method of 111 // the space must distinguish between objects in the region allocated before 112 // and after the call to save marks. 113 MemRegion used_region_at_save_marks() const { 114 return MemRegion(bottom(), saved_mark_word()); 115 } 116 117 // Initialization. 118 // "initialize" should be called once on a space, before it is used for 119 // any purpose. The "mr" arguments gives the bounds of the space, and 120 // the "clear_space" argument should be true unless the memory in "mr" is 121 // known to be zeroed. 122 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space); 123 124 // The "clear" method must be called on a region that may have 125 // had allocation performed in it, but is now to be considered empty. 126 virtual void clear(bool mangle_space); 127 128 // For detecting GC bugs. Should only be called at GC boundaries, since 129 // some unused space may be used as scratch space during GC's. 130 // We also call this when expanding a space to satisfy an allocation 131 // request. See bug #4668531 132 virtual void mangle_unused_area() = 0; 133 virtual void mangle_unused_area_complete() = 0; 134 135 // Testers 136 bool is_empty() const { return used() == 0; } 137 bool not_empty() const { return used() > 0; } 138 139 // Returns true iff the given the space contains the 140 // given address as part of an allocated object. For 141 // certain kinds of spaces, this might be a potentially 142 // expensive operation. To prevent performance problems 143 // on account of its inadvertent use in product jvm's, 144 // we restrict its use to assertion checks only. 145 bool is_in(const void* p) const { 146 return used_region().contains(p); 147 } 148 149 // Returns true iff the given reserved memory of the space contains the 150 // given address. 151 bool is_in_reserved(const void* p) const { return _bottom <= p && p < _end; } 152 153 // Returns true iff the given block is not allocated. 154 virtual bool is_free_block(const HeapWord* p) const = 0; 155 156 // Test whether p is double-aligned 157 static bool is_aligned(void* p) { 158 return ::is_aligned(p, sizeof(double)); 159 } 160 161 // Size computations. Sizes are in bytes. 162 size_t capacity() const { return byte_size(bottom(), end()); } 163 virtual size_t used() const = 0; 164 virtual size_t free() const = 0; 165 166 // Iterate over all the ref-containing fields of all objects in the 167 // space, calling "cl.do_oop" on each. Fields in objects allocated by 168 // applications of the closure are not included in the iteration. 169 virtual void oop_iterate(ExtendedOopClosure* cl); 170 171 // Iterate over all objects in the space, calling "cl.do_object" on 172 // each. Objects allocated by applications of the closure are not 173 // included in the iteration. 174 virtual void object_iterate(ObjectClosure* blk) = 0; 175 // Similar to object_iterate() except only iterates over 176 // objects whose internal references point to objects in the space. 177 virtual void safe_object_iterate(ObjectClosure* blk) = 0; 178 179 // Create and return a new dirty card to oop closure. Can be 180 // overridden to return the appropriate type of closure 181 // depending on the type of space in which the closure will 182 // operate. ResourceArea allocated. 183 virtual DirtyCardToOopClosure* new_dcto_cl(ExtendedOopClosure* cl, 184 CardTableModRefBS::PrecisionStyle precision, 185 HeapWord* boundary, 186 bool parallel); 187 188 // If "p" is in the space, returns the address of the start of the 189 // "block" that contains "p". We say "block" instead of "object" since 190 // some heaps may not pack objects densely; a chunk may either be an 191 // object or a non-object. If "p" is not in the space, return NULL. 192 virtual HeapWord* block_start_const(const void* p) const = 0; 193 194 // The non-const version may have benevolent side effects on the data 195 // structure supporting these calls, possibly speeding up future calls. 196 // The default implementation, however, is simply to call the const 197 // version. 198 virtual HeapWord* block_start(const void* p); 199 200 // Requires "addr" to be the start of a chunk, and returns its size. 201 // "addr + size" is required to be the start of a new chunk, or the end 202 // of the active area of the heap. 203 virtual size_t block_size(const HeapWord* addr) const = 0; 204 205 // Requires "addr" to be the start of a block, and returns "TRUE" iff 206 // the block is an object. 207 virtual bool block_is_obj(const HeapWord* addr) const = 0; 208 209 // Requires "addr" to be the start of a block, and returns "TRUE" iff 210 // the block is an object and the object is alive. 211 virtual bool obj_is_alive(const HeapWord* addr) const; 212 213 // Allocation (return NULL if full). Assumes the caller has established 214 // mutually exclusive access to the space. 215 virtual HeapWord* allocate(size_t word_size) = 0; 216 217 // Allocation (return NULL if full). Enforces mutual exclusion internally. 218 virtual HeapWord* par_allocate(size_t word_size) = 0; 219 220 // Mark-sweep-compact support: all spaces can update pointers to objects 221 // moving as a part of compaction. 222 virtual void adjust_pointers() = 0; 223 224 virtual void print() const; 225 virtual void print_on(outputStream* st) const; 226 virtual void print_short() const; 227 virtual void print_short_on(outputStream* st) const; 228 229 230 // Accessor for parallel sequential tasks. 231 SequentialSubTasksDone* par_seq_tasks() { return &_par_seq_tasks; } 232 233 // IF "this" is a ContiguousSpace, return it, else return NULL. 234 virtual ContiguousSpace* toContiguousSpace() { 235 return NULL; 236 } 237 238 // Debugging 239 virtual void verify() const = 0; 240 }; 241 242 // A MemRegionClosure (ResourceObj) whose "do_MemRegion" function applies an 243 // OopClosure to (the addresses of) all the ref-containing fields that could 244 // be modified by virtue of the given MemRegion being dirty. (Note that 245 // because of the imprecise nature of the write barrier, this may iterate 246 // over oops beyond the region.) 247 // This base type for dirty card to oop closures handles memory regions 248 // in non-contiguous spaces with no boundaries, and should be sub-classed 249 // to support other space types. See ContiguousDCTOC for a sub-class 250 // that works with ContiguousSpaces. 251 252 class DirtyCardToOopClosure: public MemRegionClosureRO { 253 protected: 254 ExtendedOopClosure* _cl; 255 Space* _sp; 256 CardTableModRefBS::PrecisionStyle _precision; 257 HeapWord* _boundary; // If non-NULL, process only non-NULL oops 258 // pointing below boundary. 259 HeapWord* _min_done; // ObjHeadPreciseArray precision requires 260 // a downwards traversal; this is the 261 // lowest location already done (or, 262 // alternatively, the lowest address that 263 // shouldn't be done again. NULL means infinity.) 264 NOT_PRODUCT(HeapWord* _last_bottom;) 265 NOT_PRODUCT(HeapWord* _last_explicit_min_done;) 266 267 // Get the actual top of the area on which the closure will 268 // operate, given where the top is assumed to be (the end of the 269 // memory region passed to do_MemRegion) and where the object 270 // at the top is assumed to start. For example, an object may 271 // start at the top but actually extend past the assumed top, 272 // in which case the top becomes the end of the object. 273 virtual HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj); 274 275 // Walk the given memory region from bottom to (actual) top 276 // looking for objects and applying the oop closure (_cl) to 277 // them. The base implementation of this treats the area as 278 // blocks, where a block may or may not be an object. Sub- 279 // classes should override this to provide more accurate 280 // or possibly more efficient walking. 281 virtual void walk_mem_region(MemRegion mr, HeapWord* bottom, HeapWord* top); 282 283 public: 284 DirtyCardToOopClosure(Space* sp, ExtendedOopClosure* cl, 285 CardTableModRefBS::PrecisionStyle precision, 286 HeapWord* boundary) : 287 _sp(sp), _cl(cl), _precision(precision), _boundary(boundary), 288 _min_done(NULL) { 289 NOT_PRODUCT(_last_bottom = NULL); 290 NOT_PRODUCT(_last_explicit_min_done = NULL); 291 } 292 293 void do_MemRegion(MemRegion mr); 294 295 void set_min_done(HeapWord* min_done) { 296 _min_done = min_done; 297 NOT_PRODUCT(_last_explicit_min_done = _min_done); 298 } 299 #ifndef PRODUCT 300 void set_last_bottom(HeapWord* last_bottom) { 301 _last_bottom = last_bottom; 302 } 303 #endif 304 }; 305 306 // A structure to represent a point at which objects are being copied 307 // during compaction. 308 class CompactPoint : public StackObj { 309 public: 310 Generation* gen; 311 CompactibleSpace* space; 312 HeapWord* threshold; 313 314 CompactPoint(Generation* g = NULL) : 315 gen(g), space(NULL), threshold(0) {} 316 }; 317 318 // A space that supports compaction operations. This is usually, but not 319 // necessarily, a space that is normally contiguous. But, for example, a 320 // free-list-based space whose normal collection is a mark-sweep without 321 // compaction could still support compaction in full GC's. 322 // 323 // The compaction operations are implemented by the 324 // scan_and_{adjust_pointers,compact,forward} function templates. 325 // The following are, non-virtual, auxiliary functions used by these function templates: 326 // - scan_limit() 327 // - scanned_block_is_obj() 328 // - scanned_block_size() 329 // - adjust_obj_size() 330 // - obj_size() 331 // These functions are to be used exclusively by the scan_and_* function templates, 332 // and must be defined for all (non-abstract) subclasses of CompactibleSpace. 333 // 334 // NOTE: Any subclasses to CompactibleSpace wanting to change/define the behavior 335 // in any of the auxiliary functions must also override the corresponding 336 // prepare_for_compaction/adjust_pointers/compact functions using them. 337 // If not, such changes will not be used or have no effect on the compaction operations. 338 // 339 // This translates to the following dependencies: 340 // Overrides/definitions of 341 // - scan_limit 342 // - scanned_block_is_obj 343 // - scanned_block_size 344 // require override/definition of prepare_for_compaction(). 345 // Similar dependencies exist between 346 // - adjust_obj_size and adjust_pointers() 347 // - obj_size and compact(). 348 // 349 // Additionally, this also means that changes to block_size() or block_is_obj() that 350 // should be effective during the compaction operations must provide a corresponding 351 // definition of scanned_block_size/scanned_block_is_obj respectively. 352 class CompactibleSpace: public Space { 353 friend class VMStructs; 354 friend class CompactibleFreeListSpace; 355 private: 356 HeapWord* _compaction_top; 357 CompactibleSpace* _next_compaction_space; 358 359 // Auxiliary functions for scan_and_{forward,adjust_pointers,compact} support. 360 inline size_t adjust_obj_size(size_t size) const { 361 return size; 362 } 363 364 inline size_t obj_size(const HeapWord* addr) const; 365 366 template <class SpaceType> 367 static inline void verify_up_to_first_dead(SpaceType* space) NOT_DEBUG_RETURN; 368 369 template <class SpaceType> 370 static inline void clear_empty_region(SpaceType* space); 371 372 public: 373 CompactibleSpace() : 374 _compaction_top(NULL), _next_compaction_space(NULL) {} 375 376 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space); 377 virtual void clear(bool mangle_space); 378 379 // Used temporarily during a compaction phase to hold the value 380 // top should have when compaction is complete. 381 HeapWord* compaction_top() const { return _compaction_top; } 382 383 void set_compaction_top(HeapWord* value) { 384 assert(value == NULL || (value >= bottom() && value <= end()), 385 "should point inside space"); 386 _compaction_top = value; 387 } 388 389 // Perform operations on the space needed after a compaction 390 // has been performed. 391 virtual void reset_after_compaction() = 0; 392 393 // Returns the next space (in the current generation) to be compacted in 394 // the global compaction order. Also is used to select the next 395 // space into which to compact. 396 397 virtual CompactibleSpace* next_compaction_space() const { 398 return _next_compaction_space; 399 } 400 401 void set_next_compaction_space(CompactibleSpace* csp) { 402 _next_compaction_space = csp; 403 } 404 405 // MarkSweep support phase2 406 407 // Start the process of compaction of the current space: compute 408 // post-compaction addresses, and insert forwarding pointers. The fields 409 // "cp->gen" and "cp->compaction_space" are the generation and space into 410 // which we are currently compacting. This call updates "cp" as necessary, 411 // and leaves the "compaction_top" of the final value of 412 // "cp->compaction_space" up-to-date. Offset tables may be updated in 413 // this phase as if the final copy had occurred; if so, "cp->threshold" 414 // indicates when the next such action should be taken. 415 virtual void prepare_for_compaction(CompactPoint* cp) = 0; 416 // MarkSweep support phase3 417 virtual void adjust_pointers(); 418 // MarkSweep support phase4 419 virtual void compact(); 420 421 // The maximum percentage of objects that can be dead in the compacted 422 // live part of a compacted space ("deadwood" support.) 423 virtual size_t allowed_dead_ratio() const { return 0; }; 424 425 // Some contiguous spaces may maintain some data structures that should 426 // be updated whenever an allocation crosses a boundary. This function 427 // returns the first such boundary. 428 // (The default implementation returns the end of the space, so the 429 // boundary is never crossed.) 430 virtual HeapWord* initialize_threshold() { return end(); } 431 432 // "q" is an object of the given "size" that should be forwarded; 433 // "cp" names the generation ("gen") and containing "this" (which must 434 // also equal "cp->space"). "compact_top" is where in "this" the 435 // next object should be forwarded to. If there is room in "this" for 436 // the object, insert an appropriate forwarding pointer in "q". 437 // If not, go to the next compaction space (there must 438 // be one, since compaction must succeed -- we go to the first space of 439 // the previous generation if necessary, updating "cp"), reset compact_top 440 // and then forward. In either case, returns the new value of "compact_top". 441 // If the forwarding crosses "cp->threshold", invokes the "cross_threshold" 442 // function of the then-current compaction space, and updates "cp->threshold 443 // accordingly". 444 virtual HeapWord* forward(oop q, size_t size, CompactPoint* cp, 445 HeapWord* compact_top); 446 447 // Return a size with adjustments as required of the space. 448 virtual size_t adjust_object_size_v(size_t size) const { return size; } 449 450 void set_first_dead(HeapWord* value) { _first_dead = value; } 451 void set_end_of_live(HeapWord* value) { _end_of_live = value; } 452 453 protected: 454 // Used during compaction. 455 HeapWord* _first_dead; 456 HeapWord* _end_of_live; 457 458 // Minimum size of a free block. 459 virtual size_t minimum_free_block_size() const { return 0; } 460 461 // This the function is invoked when an allocation of an object covering 462 // "start" to "end occurs crosses the threshold; returns the next 463 // threshold. (The default implementation does nothing.) 464 virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* the_end) { 465 return end(); 466 } 467 468 // Below are template functions for scan_and_* algorithms (avoiding virtual calls). 469 // The space argument should be a subclass of CompactibleSpace, implementing 470 // scan_limit(), scanned_block_is_obj(), and scanned_block_size(), 471 // and possibly also overriding obj_size(), and adjust_obj_size(). 472 // These functions should avoid virtual calls whenever possible. 473 474 // Frequently calls adjust_obj_size(). 475 template <class SpaceType> 476 static inline void scan_and_adjust_pointers(SpaceType* space); 477 478 // Frequently calls obj_size(). 479 template <class SpaceType> 480 static inline void scan_and_compact(SpaceType* space); 481 482 // Frequently calls scanned_block_is_obj() and scanned_block_size(). 483 // Requires the scan_limit() function. 484 template <class SpaceType> 485 static inline void scan_and_forward(SpaceType* space, CompactPoint* cp); 486 }; 487 488 class GenSpaceMangler; 489 490 // A space in which the free area is contiguous. It therefore supports 491 // faster allocation, and compaction. 492 class ContiguousSpace: public CompactibleSpace { 493 friend class VMStructs; 494 // Allow scan_and_forward function to call (private) overrides for auxiliary functions on this class 495 template <typename SpaceType> 496 friend void CompactibleSpace::scan_and_forward(SpaceType* space, CompactPoint* cp); 497 498 private: 499 // Auxiliary functions for scan_and_forward support. 500 // See comments for CompactibleSpace for more information. 501 inline HeapWord* scan_limit() const { 502 return top(); 503 } 504 505 inline bool scanned_block_is_obj(const HeapWord* addr) const { 506 return true; // Always true, since scan_limit is top 507 } 508 509 inline size_t scanned_block_size(const HeapWord* addr) const; 510 511 protected: 512 HeapWord* _top; 513 HeapWord* _concurrent_iteration_safe_limit; 514 // A helper for mangling the unused area of the space in debug builds. 515 GenSpaceMangler* _mangler; 516 517 GenSpaceMangler* mangler() { return _mangler; } 518 519 // Allocation helpers (return NULL if full). 520 inline HeapWord* allocate_impl(size_t word_size); 521 inline HeapWord* par_allocate_impl(size_t word_size); 522 523 public: 524 ContiguousSpace(); 525 ~ContiguousSpace(); 526 527 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space); 528 virtual void clear(bool mangle_space); 529 530 // Accessors 531 HeapWord* top() const { return _top; } 532 void set_top(HeapWord* value) { _top = value; } 533 534 void set_saved_mark() { _saved_mark_word = top(); } 535 void reset_saved_mark() { _saved_mark_word = bottom(); } 536 537 bool saved_mark_at_top() const { return saved_mark_word() == top(); } 538 539 // In debug mode mangle (write it with a particular bit 540 // pattern) the unused part of a space. 541 542 // Used to save the an address in a space for later use during mangling. 543 void set_top_for_allocations(HeapWord* v) PRODUCT_RETURN; 544 // Used to save the space's current top for later use during mangling. 545 void set_top_for_allocations() PRODUCT_RETURN; 546 547 // Mangle regions in the space from the current top up to the 548 // previously mangled part of the space. 549 void mangle_unused_area() PRODUCT_RETURN; 550 // Mangle [top, end) 551 void mangle_unused_area_complete() PRODUCT_RETURN; 552 553 // Do some sparse checking on the area that should have been mangled. 554 void check_mangled_unused_area(HeapWord* limit) PRODUCT_RETURN; 555 // Check the complete area that should have been mangled. 556 // This code may be NULL depending on the macro DEBUG_MANGLING. 557 void check_mangled_unused_area_complete() PRODUCT_RETURN; 558 559 // Size computations: sizes in bytes. 560 size_t capacity() const { return byte_size(bottom(), end()); } 561 size_t used() const { return byte_size(bottom(), top()); } 562 size_t free() const { return byte_size(top(), end()); } 563 564 virtual bool is_free_block(const HeapWord* p) const; 565 566 // In a contiguous space we have a more obvious bound on what parts 567 // contain objects. 568 MemRegion used_region() const { return MemRegion(bottom(), top()); } 569 570 // Allocation (return NULL if full) 571 virtual HeapWord* allocate(size_t word_size); 572 virtual HeapWord* par_allocate(size_t word_size); 573 HeapWord* allocate_aligned(size_t word_size); 574 575 // Iteration 576 void oop_iterate(ExtendedOopClosure* cl); 577 void object_iterate(ObjectClosure* blk); 578 // For contiguous spaces this method will iterate safely over objects 579 // in the space (i.e., between bottom and top) when at a safepoint. 580 void safe_object_iterate(ObjectClosure* blk); 581 582 // Iterate over as many initialized objects in the space as possible, 583 // calling "cl.do_object_careful" on each. Return NULL if all objects 584 // in the space (at the start of the iteration) were iterated over. 585 // Return an address indicating the extent of the iteration in the 586 // event that the iteration had to return because of finding an 587 // uninitialized object in the space, or if the closure "cl" 588 // signaled early termination. 589 HeapWord* object_iterate_careful(ObjectClosureCareful* cl); 590 HeapWord* concurrent_iteration_safe_limit() { 591 assert(_concurrent_iteration_safe_limit <= top(), 592 "_concurrent_iteration_safe_limit update missed"); 593 return _concurrent_iteration_safe_limit; 594 } 595 // changes the safe limit, all objects from bottom() to the new 596 // limit should be properly initialized 597 void set_concurrent_iteration_safe_limit(HeapWord* new_limit) { 598 assert(new_limit <= top(), "uninitialized objects in the safe range"); 599 _concurrent_iteration_safe_limit = new_limit; 600 } 601 602 603 #if INCLUDE_ALL_GCS 604 // In support of parallel oop_iterate. 605 #define ContigSpace_PAR_OOP_ITERATE_DECL(OopClosureType, nv_suffix) \ 606 void par_oop_iterate(MemRegion mr, OopClosureType* blk); 607 608 ALL_PAR_OOP_ITERATE_CLOSURES(ContigSpace_PAR_OOP_ITERATE_DECL) 609 #undef ContigSpace_PAR_OOP_ITERATE_DECL 610 #endif // INCLUDE_ALL_GCS 611 612 // Compaction support 613 virtual void reset_after_compaction() { 614 assert(compaction_top() >= bottom() && compaction_top() <= end(), "should point inside space"); 615 set_top(compaction_top()); 616 // set new iteration safe limit 617 set_concurrent_iteration_safe_limit(compaction_top()); 618 } 619 620 // Override. 621 DirtyCardToOopClosure* new_dcto_cl(ExtendedOopClosure* cl, 622 CardTableModRefBS::PrecisionStyle precision, 623 HeapWord* boundary, 624 bool parallel); 625 626 // Apply "blk->do_oop" to the addresses of all reference fields in objects 627 // starting with the _saved_mark_word, which was noted during a generation's 628 // save_marks and is required to denote the head of an object. 629 // Fields in objects allocated by applications of the closure 630 // *are* included in the iteration. 631 // Updates _saved_mark_word to point to just after the last object 632 // iterated over. 633 #define ContigSpace_OOP_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \ 634 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk); 635 636 ALL_SINCE_SAVE_MARKS_CLOSURES(ContigSpace_OOP_SINCE_SAVE_MARKS_DECL) 637 #undef ContigSpace_OOP_SINCE_SAVE_MARKS_DECL 638 639 // Same as object_iterate, but starting from "mark", which is required 640 // to denote the start of an object. Objects allocated by 641 // applications of the closure *are* included in the iteration. 642 virtual void object_iterate_from(HeapWord* mark, ObjectClosure* blk); 643 644 // Very inefficient implementation. 645 virtual HeapWord* block_start_const(const void* p) const; 646 size_t block_size(const HeapWord* p) const; 647 // If a block is in the allocated area, it is an object. 648 bool block_is_obj(const HeapWord* p) const { return p < top(); } 649 650 // Addresses for inlined allocation 651 HeapWord** top_addr() { return &_top; } 652 HeapWord** end_addr() { return &_end; } 653 654 // Overrides for more efficient compaction support. 655 void prepare_for_compaction(CompactPoint* cp); 656 657 virtual void print_on(outputStream* st) const; 658 659 // Checked dynamic downcasts. 660 virtual ContiguousSpace* toContiguousSpace() { 661 return this; 662 } 663 664 // Debugging 665 virtual void verify() const; 666 667 // Used to increase collection frequency. "factor" of 0 means entire 668 // space. 669 void allocate_temporary_filler(int factor); 670 }; 671 672 673 // A dirty card to oop closure that does filtering. 674 // It knows how to filter out objects that are outside of the _boundary. 675 class FilteringDCTOC : public DirtyCardToOopClosure { 676 protected: 677 // Override. 678 void walk_mem_region(MemRegion mr, 679 HeapWord* bottom, HeapWord* top); 680 681 // Walk the given memory region, from bottom to top, applying 682 // the given oop closure to (possibly) all objects found. The 683 // given oop closure may or may not be the same as the oop 684 // closure with which this closure was created, as it may 685 // be a filtering closure which makes use of the _boundary. 686 // We offer two signatures, so the FilteringClosure static type is 687 // apparent. 688 virtual void walk_mem_region_with_cl(MemRegion mr, 689 HeapWord* bottom, HeapWord* top, 690 ExtendedOopClosure* cl) = 0; 691 virtual void walk_mem_region_with_cl(MemRegion mr, 692 HeapWord* bottom, HeapWord* top, 693 FilteringClosure* cl) = 0; 694 695 public: 696 FilteringDCTOC(Space* sp, ExtendedOopClosure* cl, 697 CardTableModRefBS::PrecisionStyle precision, 698 HeapWord* boundary) : 699 DirtyCardToOopClosure(sp, cl, precision, boundary) {} 700 }; 701 702 // A dirty card to oop closure for contiguous spaces 703 // (ContiguousSpace and sub-classes). 704 // It is a FilteringClosure, as defined above, and it knows: 705 // 706 // 1. That the actual top of any area in a memory region 707 // contained by the space is bounded by the end of the contiguous 708 // region of the space. 709 // 2. That the space is really made up of objects and not just 710 // blocks. 711 712 class ContiguousSpaceDCTOC : public FilteringDCTOC { 713 protected: 714 // Overrides. 715 HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj); 716 717 virtual void walk_mem_region_with_cl(MemRegion mr, 718 HeapWord* bottom, HeapWord* top, 719 ExtendedOopClosure* cl); 720 virtual void walk_mem_region_with_cl(MemRegion mr, 721 HeapWord* bottom, HeapWord* top, 722 FilteringClosure* cl); 723 724 public: 725 ContiguousSpaceDCTOC(ContiguousSpace* sp, ExtendedOopClosure* cl, 726 CardTableModRefBS::PrecisionStyle precision, 727 HeapWord* boundary) : 728 FilteringDCTOC(sp, cl, precision, boundary) 729 {} 730 }; 731 732 // A ContigSpace that Supports an efficient "block_start" operation via 733 // a BlockOffsetArray (whose BlockOffsetSharedArray may be shared with 734 // other spaces.) This is the abstract base class for old generation 735 // (tenured) spaces. 736 737 class OffsetTableContigSpace: public ContiguousSpace { 738 friend class VMStructs; 739 protected: 740 BlockOffsetArrayContigSpace _offsets; 741 Mutex _par_alloc_lock; 742 743 public: 744 // Constructor 745 OffsetTableContigSpace(BlockOffsetSharedArray* sharedOffsetArray, 746 MemRegion mr); 747 748 void set_bottom(HeapWord* value); 749 void set_end(HeapWord* value); 750 751 void clear(bool mangle_space); 752 753 inline HeapWord* block_start_const(const void* p) const; 754 755 // Add offset table update. 756 virtual inline HeapWord* allocate(size_t word_size); 757 inline HeapWord* par_allocate(size_t word_size); 758 759 // MarkSweep support phase3 760 virtual HeapWord* initialize_threshold(); 761 virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* end); 762 763 virtual void print_on(outputStream* st) const; 764 765 // Debugging 766 void verify() const; 767 }; 768 769 770 // Class TenuredSpace is used by TenuredGeneration 771 772 class TenuredSpace: public OffsetTableContigSpace { 773 friend class VMStructs; 774 protected: 775 // Mark sweep support 776 size_t allowed_dead_ratio() const; 777 public: 778 // Constructor 779 TenuredSpace(BlockOffsetSharedArray* sharedOffsetArray, 780 MemRegion mr) : 781 OffsetTableContigSpace(sharedOffsetArray, mr) {} 782 }; 783 #endif // SHARE_VM_GC_SHARED_SPACE_HPP