1 /* 2 * Copyright (c) 1997, 2015, 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/macros.hpp" 37 38 // A space is an abstraction for the "storage units" backing 39 // up the generation abstraction. It includes specific 40 // implementations for keeping track of free and used space, 41 // for iterating over objects and free blocks, etc. 42 43 // Forward decls. 44 class Space; 45 class BlockOffsetArray; 46 class BlockOffsetArrayContigSpace; 47 class Generation; 48 class CompactibleSpace; 49 class BlockOffsetTable; 50 class CardTableRS; 51 class DirtyCardToOopClosure; 52 53 // A Space describes a heap area. Class Space is an abstract 54 // base class. 55 // 56 // Space supports allocation, size computation and GC support is provided. 57 // 58 // Invariant: bottom() and end() are on page_size boundaries and 59 // bottom() <= top() <= end() 60 // top() is inclusive and end() is exclusive. 61 62 class Space: public CHeapObj<mtGC> { 63 friend class VMStructs; 64 protected: 65 HeapWord* _bottom; 66 HeapWord* _end; 67 68 // Used in support of save_marks() 69 HeapWord* _saved_mark_word; 70 71 // A sequential tasks done structure. This supports 72 // parallel GC, where we have threads dynamically 73 // claiming sub-tasks from a larger parallel task. 74 SequentialSubTasksDone _par_seq_tasks; 75 76 Space(): 77 _bottom(NULL), _end(NULL) { } 78 79 public: 80 // Accessors 81 HeapWord* bottom() const { return _bottom; } 82 HeapWord* end() const { return _end; } 83 virtual void set_bottom(HeapWord* value) { _bottom = value; } 84 virtual void set_end(HeapWord* value) { _end = value; } 85 86 virtual HeapWord* saved_mark_word() const { return _saved_mark_word; } 87 88 void set_saved_mark_word(HeapWord* p) { _saved_mark_word = p; } 89 90 // Returns true if this object has been allocated since a 91 // generation's "save_marks" call. 92 virtual bool obj_allocated_since_save_marks(const oop obj) const { 93 return (HeapWord*)obj >= saved_mark_word(); 94 } 95 96 virtual MemRegionClosure* preconsumptionDirtyCardClosure() const { 97 return NULL; 98 } 99 100 // Returns a subregion of the space containing only the allocated objects in 101 // the space. 102 virtual MemRegion used_region() const = 0; 103 104 // Returns a region that is guaranteed to contain (at least) all objects 105 // allocated at the time of the last call to "save_marks". If the space 106 // initializes its DirtyCardToOopClosure's specifying the "contig" option 107 // (that is, if the space is contiguous), then this region must contain only 108 // such objects: the memregion will be from the bottom of the region to the 109 // saved mark. Otherwise, the "obj_allocated_since_save_marks" method of 110 // the space must distinguish between objects in the region allocated before 111 // and after the call to save marks. 112 MemRegion used_region_at_save_marks() const { 113 return MemRegion(bottom(), saved_mark_word()); 114 } 115 116 // Initialization. 117 // "initialize" should be called once on a space, before it is used for 118 // any purpose. The "mr" arguments gives the bounds of the space, and 119 // the "clear_space" argument should be true unless the memory in "mr" is 120 // known to be zeroed. 121 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space); 122 123 // The "clear" method must be called on a region that may have 124 // had allocation performed in it, but is now to be considered empty. 125 virtual void clear(bool mangle_space); 126 127 // For detecting GC bugs. Should only be called at GC boundaries, since 128 // some unused space may be used as scratch space during GC's. 129 // We also call this when expanding a space to satisfy an allocation 130 // request. See bug #4668531 131 virtual void mangle_unused_area() = 0; 132 virtual void mangle_unused_area_complete() = 0; 133 134 // Testers 135 bool is_empty() const { return used() == 0; } 136 bool not_empty() const { return used() > 0; } 137 138 // Returns true iff the given the space contains the 139 // given address as part of an allocated object. For 140 // certain kinds of spaces, this might be a potentially 141 // expensive operation. To prevent performance problems 142 // on account of its inadvertent use in product jvm's, 143 // we restrict its use to assertion checks only. 144 bool is_in(const void* p) const { 145 return used_region().contains(p); 146 } 147 148 // Returns true iff the given reserved memory of the space contains the 149 // given address. 150 bool is_in_reserved(const void* p) const { return _bottom <= p && p < _end; } 151 152 // Returns true iff the given block is not allocated. 153 virtual bool is_free_block(const HeapWord* p) const = 0; 154 155 // Test whether p is double-aligned 156 static bool is_aligned(void* p) { 157 return ((intptr_t)p & (sizeof(double)-1)) == 0; 158 } 159 160 // Size computations. Sizes are in bytes. 161 size_t capacity() const { return byte_size(bottom(), end()); } 162 virtual size_t used() const = 0; 163 virtual size_t free() const = 0; 164 165 // Iterate over all the ref-containing fields of all objects in the 166 // space, calling "cl.do_oop" on each. Fields in objects allocated by 167 // applications of the closure are not included in the iteration. 168 virtual void oop_iterate(ExtendedOopClosure* cl); 169 170 // Iterate over all objects in the space, calling "cl.do_object" on 171 // each. Objects allocated by applications of the closure are not 172 // included in the iteration. 173 virtual void object_iterate(ObjectClosure* blk) = 0; 174 // Similar to object_iterate() except only iterates over 175 // objects whose internal references point to objects in the space. 176 virtual void safe_object_iterate(ObjectClosure* blk) = 0; 177 178 // Create and return a new dirty card to oop closure. Can be 179 // overridden to return the appropriate type of closure 180 // depending on the type of space in which the closure will 181 // operate. ResourceArea allocated. 182 virtual DirtyCardToOopClosure* new_dcto_cl(ExtendedOopClosure* cl, 183 CardTableModRefBS::PrecisionStyle precision, 184 HeapWord* boundary, 185 bool parallel); 186 187 // If "p" is in the space, returns the address of the start of the 188 // "block" that contains "p". We say "block" instead of "object" since 189 // some heaps may not pack objects densely; a chunk may either be an 190 // object or a non-object. If "p" is not in the space, return NULL. 191 virtual HeapWord* block_start_const(const void* p) const = 0; 192 193 // The non-const version may have benevolent side effects on the data 194 // structure supporting these calls, possibly speeding up future calls. 195 // The default implementation, however, is simply to call the const 196 // version. 197 virtual HeapWord* block_start(const void* p); 198 199 // Requires "addr" to be the start of a chunk, and returns its size. 200 // "addr + size" is required to be the start of a new chunk, or the end 201 // of the active area of the heap. 202 virtual size_t block_size(const HeapWord* addr) const = 0; 203 204 // Requires "addr" to be the start of a block, and returns "TRUE" iff 205 // the block is an object. 206 virtual bool block_is_obj(const HeapWord* addr) const = 0; 207 208 // Requires "addr" to be the start of a block, and returns "TRUE" iff 209 // the block is an object and the object is alive. 210 virtual bool obj_is_alive(const HeapWord* addr) const; 211 212 // Allocation (return NULL if full). Assumes the caller has established 213 // mutually exclusive access to the space. 214 virtual HeapWord* allocate(size_t word_size) = 0; 215 216 // Allocation (return NULL if full). Enforces mutual exclusion internally. 217 virtual HeapWord* par_allocate(size_t word_size) = 0; 218 219 // Mark-sweep-compact support: all spaces can update pointers to objects 220 // moving as a part of compaction. 221 virtual void adjust_pointers() = 0; 222 223 // PrintHeapAtGC support 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 return oop(addr)->size(); 366 } 367 368 public: 369 CompactibleSpace() : 370 _compaction_top(NULL), _next_compaction_space(NULL) {} 371 372 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space); 373 virtual void clear(bool mangle_space); 374 375 // Used temporarily during a compaction phase to hold the value 376 // top should have when compaction is complete. 377 HeapWord* compaction_top() const { return _compaction_top; } 378 379 void set_compaction_top(HeapWord* value) { 380 assert(value == NULL || (value >= bottom() && value <= end()), 381 "should point inside space"); 382 _compaction_top = value; 383 } 384 385 // Perform operations on the space needed after a compaction 386 // has been performed. 387 virtual void reset_after_compaction() = 0; 388 389 // Returns the next space (in the current generation) to be compacted in 390 // the global compaction order. Also is used to select the next 391 // space into which to compact. 392 393 virtual CompactibleSpace* next_compaction_space() const { 394 return _next_compaction_space; 395 } 396 397 void set_next_compaction_space(CompactibleSpace* csp) { 398 _next_compaction_space = csp; 399 } 400 401 // MarkSweep support phase2 402 403 // Start the process of compaction of the current space: compute 404 // post-compaction addresses, and insert forwarding pointers. The fields 405 // "cp->gen" and "cp->compaction_space" are the generation and space into 406 // which we are currently compacting. This call updates "cp" as necessary, 407 // and leaves the "compaction_top" of the final value of 408 // "cp->compaction_space" up-to-date. Offset tables may be updated in 409 // this phase as if the final copy had occurred; if so, "cp->threshold" 410 // indicates when the next such action should be taken. 411 virtual void prepare_for_compaction(CompactPoint* cp) = 0; 412 // MarkSweep support phase3 413 virtual void adjust_pointers(); 414 // MarkSweep support phase4 415 virtual void compact(); 416 417 // The maximum percentage of objects that can be dead in the compacted 418 // live part of a compacted space ("deadwood" support.) 419 virtual size_t allowed_dead_ratio() const { return 0; }; 420 421 // Some contiguous spaces may maintain some data structures that should 422 // be updated whenever an allocation crosses a boundary. This function 423 // returns the first such boundary. 424 // (The default implementation returns the end of the space, so the 425 // boundary is never crossed.) 426 virtual HeapWord* initialize_threshold() { return end(); } 427 428 // "q" is an object of the given "size" that should be forwarded; 429 // "cp" names the generation ("gen") and containing "this" (which must 430 // also equal "cp->space"). "compact_top" is where in "this" the 431 // next object should be forwarded to. If there is room in "this" for 432 // the object, insert an appropriate forwarding pointer in "q". 433 // If not, go to the next compaction space (there must 434 // be one, since compaction must succeed -- we go to the first space of 435 // the previous generation if necessary, updating "cp"), reset compact_top 436 // and then forward. In either case, returns the new value of "compact_top". 437 // If the forwarding crosses "cp->threshold", invokes the "cross_threshold" 438 // function of the then-current compaction space, and updates "cp->threshold 439 // accordingly". 440 virtual HeapWord* forward(oop q, size_t size, CompactPoint* cp, 441 HeapWord* compact_top); 442 443 // Return a size with adjustments as required of the space. 444 virtual size_t adjust_object_size_v(size_t size) const { return size; } 445 446 protected: 447 // Used during compaction. 448 HeapWord* _first_dead; 449 HeapWord* _end_of_live; 450 451 // Minimum size of a free block. 452 virtual size_t minimum_free_block_size() const { return 0; } 453 454 // This the function is invoked when an allocation of an object covering 455 // "start" to "end occurs crosses the threshold; returns the next 456 // threshold. (The default implementation does nothing.) 457 virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* the_end) { 458 return end(); 459 } 460 461 // Requires "allowed_deadspace_words > 0", that "q" is the start of a 462 // free block of the given "word_len", and that "q", were it an object, 463 // would not move if forwarded. If the size allows, fill the free 464 // block with an object, to prevent excessive compaction. Returns "true" 465 // iff the free region was made deadspace, and modifies 466 // "allowed_deadspace_words" to reflect the number of available deadspace 467 // words remaining after this operation. 468 bool insert_deadspace(size_t& allowed_deadspace_words, HeapWord* q, 469 size_t word_len); 470 471 // Below are template functions for scan_and_* algorithms (avoiding virtual calls). 472 // The space argument should be a subclass of CompactibleSpace, implementing 473 // scan_limit(), scanned_block_is_obj(), and scanned_block_size(), 474 // and possibly also overriding obj_size(), and adjust_obj_size(). 475 // These functions should avoid virtual calls whenever possible. 476 477 // Frequently calls adjust_obj_size(). 478 template <class SpaceType> 479 static inline void scan_and_adjust_pointers(SpaceType* space); 480 481 // Frequently calls obj_size(). 482 template <class SpaceType> 483 static inline void scan_and_compact(SpaceType* space); 484 485 // Frequently calls scanned_block_is_obj() and scanned_block_size(). 486 // Requires the scan_limit() function. 487 template <class SpaceType> 488 static inline void scan_and_forward(SpaceType* space, CompactPoint* cp); 489 }; 490 491 class GenSpaceMangler; 492 493 // A space in which the free area is contiguous. It therefore supports 494 // faster allocation, and compaction. 495 class ContiguousSpace: public CompactibleSpace { 496 friend class VMStructs; 497 // Allow scan_and_forward function to call (private) overrides for auxiliary functions on this class 498 template <typename SpaceType> 499 friend void CompactibleSpace::scan_and_forward(SpaceType* space, CompactPoint* cp); 500 501 private: 502 // Auxiliary functions for scan_and_forward support. 503 // See comments for CompactibleSpace for more information. 504 inline HeapWord* scan_limit() const { 505 return top(); 506 } 507 508 inline bool scanned_block_is_obj(const HeapWord* addr) const { 509 return true; // Always true, since scan_limit is top 510 } 511 512 inline size_t scanned_block_size(const HeapWord* addr) const { 513 return oop(addr)->size(); 514 } 515 516 protected: 517 HeapWord* _top; 518 HeapWord* _concurrent_iteration_safe_limit; 519 // A helper for mangling the unused area of the space in debug builds. 520 GenSpaceMangler* _mangler; 521 522 GenSpaceMangler* mangler() { return _mangler; } 523 524 // Allocation helpers (return NULL if full). 525 inline HeapWord* allocate_impl(size_t word_size); 526 inline HeapWord* par_allocate_impl(size_t word_size); 527 528 public: 529 ContiguousSpace(); 530 ~ContiguousSpace(); 531 532 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space); 533 virtual void clear(bool mangle_space); 534 535 // Accessors 536 HeapWord* top() const { return _top; } 537 void set_top(HeapWord* value) { _top = value; } 538 539 void set_saved_mark() { _saved_mark_word = top(); } 540 void reset_saved_mark() { _saved_mark_word = bottom(); } 541 542 bool saved_mark_at_top() const { return saved_mark_word() == top(); } 543 544 // In debug mode mangle (write it with a particular bit 545 // pattern) the unused part of a space. 546 547 // Used to save the an address in a space for later use during mangling. 548 void set_top_for_allocations(HeapWord* v) PRODUCT_RETURN; 549 // Used to save the space's current top for later use during mangling. 550 void set_top_for_allocations() PRODUCT_RETURN; 551 552 // Mangle regions in the space from the current top up to the 553 // previously mangled part of the space. 554 void mangle_unused_area() PRODUCT_RETURN; 555 // Mangle [top, end) 556 void mangle_unused_area_complete() PRODUCT_RETURN; 557 558 // Do some sparse checking on the area that should have been mangled. 559 void check_mangled_unused_area(HeapWord* limit) PRODUCT_RETURN; 560 // Check the complete area that should have been mangled. 561 // This code may be NULL depending on the macro DEBUG_MANGLING. 562 void check_mangled_unused_area_complete() PRODUCT_RETURN; 563 564 // Size computations: sizes in bytes. 565 size_t capacity() const { return byte_size(bottom(), end()); } 566 size_t used() const { return byte_size(bottom(), top()); } 567 size_t free() const { return byte_size(top(), end()); } 568 569 virtual bool is_free_block(const HeapWord* p) const; 570 571 // In a contiguous space we have a more obvious bound on what parts 572 // contain objects. 573 MemRegion used_region() const { return MemRegion(bottom(), top()); } 574 575 // Allocation (return NULL if full) 576 virtual HeapWord* allocate(size_t word_size); 577 virtual HeapWord* par_allocate(size_t word_size); 578 HeapWord* allocate_aligned(size_t word_size); 579 580 // Iteration 581 void oop_iterate(ExtendedOopClosure* cl); 582 void object_iterate(ObjectClosure* blk); 583 // For contiguous spaces this method will iterate safely over objects 584 // in the space (i.e., between bottom and top) when at a safepoint. 585 void safe_object_iterate(ObjectClosure* blk); 586 587 // Iterate over as many initialized objects in the space as possible, 588 // calling "cl.do_object_careful" on each. Return NULL if all objects 589 // in the space (at the start of the iteration) were iterated over. 590 // Return an address indicating the extent of the iteration in the 591 // event that the iteration had to return because of finding an 592 // uninitialized object in the space, or if the closure "cl" 593 // signaled early termination. 594 HeapWord* object_iterate_careful(ObjectClosureCareful* cl); 595 HeapWord* concurrent_iteration_safe_limit() { 596 assert(_concurrent_iteration_safe_limit <= top(), 597 "_concurrent_iteration_safe_limit update missed"); 598 return _concurrent_iteration_safe_limit; 599 } 600 // changes the safe limit, all objects from bottom() to the new 601 // limit should be properly initialized 602 void set_concurrent_iteration_safe_limit(HeapWord* new_limit) { 603 assert(new_limit <= top(), "uninitialized objects in the safe range"); 604 _concurrent_iteration_safe_limit = new_limit; 605 } 606 607 608 #if INCLUDE_ALL_GCS 609 // In support of parallel oop_iterate. 610 #define ContigSpace_PAR_OOP_ITERATE_DECL(OopClosureType, nv_suffix) \ 611 void par_oop_iterate(MemRegion mr, OopClosureType* blk); 612 613 ALL_PAR_OOP_ITERATE_CLOSURES(ContigSpace_PAR_OOP_ITERATE_DECL) 614 #undef ContigSpace_PAR_OOP_ITERATE_DECL 615 #endif // INCLUDE_ALL_GCS 616 617 // Compaction support 618 virtual void reset_after_compaction() { 619 assert(compaction_top() >= bottom() && compaction_top() <= end(), "should point inside space"); 620 set_top(compaction_top()); 621 // set new iteration safe limit 622 set_concurrent_iteration_safe_limit(compaction_top()); 623 } 624 625 // Override. 626 DirtyCardToOopClosure* new_dcto_cl(ExtendedOopClosure* cl, 627 CardTableModRefBS::PrecisionStyle precision, 628 HeapWord* boundary, 629 bool parallel); 630 631 // Apply "blk->do_oop" to the addresses of all reference fields in objects 632 // starting with the _saved_mark_word, which was noted during a generation's 633 // save_marks and is required to denote the head of an object. 634 // Fields in objects allocated by applications of the closure 635 // *are* included in the iteration. 636 // Updates _saved_mark_word to point to just after the last object 637 // iterated over. 638 #define ContigSpace_OOP_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \ 639 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk); 640 641 ALL_SINCE_SAVE_MARKS_CLOSURES(ContigSpace_OOP_SINCE_SAVE_MARKS_DECL) 642 #undef ContigSpace_OOP_SINCE_SAVE_MARKS_DECL 643 644 // Same as object_iterate, but starting from "mark", which is required 645 // to denote the start of an object. Objects allocated by 646 // applications of the closure *are* included in the iteration. 647 virtual void object_iterate_from(HeapWord* mark, ObjectClosure* blk); 648 649 // Very inefficient implementation. 650 virtual HeapWord* block_start_const(const void* p) const; 651 size_t block_size(const HeapWord* p) const; 652 // If a block is in the allocated area, it is an object. 653 bool block_is_obj(const HeapWord* p) const { return p < top(); } 654 655 // Addresses for inlined allocation 656 HeapWord** top_addr() { return &_top; } 657 HeapWord** end_addr() { return &_end; } 658 659 // Overrides for more efficient compaction support. 660 void prepare_for_compaction(CompactPoint* cp); 661 662 // PrintHeapAtGC support. 663 virtual void print_on(outputStream* st) const; 664 665 // Checked dynamic downcasts. 666 virtual ContiguousSpace* toContiguousSpace() { 667 return this; 668 } 669 670 // Debugging 671 virtual void verify() const; 672 673 // Used to increase collection frequency. "factor" of 0 means entire 674 // space. 675 void allocate_temporary_filler(int factor); 676 }; 677 678 679 // A dirty card to oop closure that does filtering. 680 // It knows how to filter out objects that are outside of the _boundary. 681 class Filtering_DCTOC : public DirtyCardToOopClosure { 682 protected: 683 // Override. 684 void walk_mem_region(MemRegion mr, 685 HeapWord* bottom, HeapWord* top); 686 687 // Walk the given memory region, from bottom to top, applying 688 // the given oop closure to (possibly) all objects found. The 689 // given oop closure may or may not be the same as the oop 690 // closure with which this closure was created, as it may 691 // be a filtering closure which makes use of the _boundary. 692 // We offer two signatures, so the FilteringClosure static type is 693 // apparent. 694 virtual void walk_mem_region_with_cl(MemRegion mr, 695 HeapWord* bottom, HeapWord* top, 696 ExtendedOopClosure* cl) = 0; 697 virtual void walk_mem_region_with_cl(MemRegion mr, 698 HeapWord* bottom, HeapWord* top, 699 FilteringClosure* cl) = 0; 700 701 public: 702 Filtering_DCTOC(Space* sp, ExtendedOopClosure* cl, 703 CardTableModRefBS::PrecisionStyle precision, 704 HeapWord* boundary) : 705 DirtyCardToOopClosure(sp, cl, precision, boundary) {} 706 }; 707 708 // A dirty card to oop closure for contiguous spaces 709 // (ContiguousSpace and sub-classes). 710 // It is a FilteringClosure, as defined above, and it knows: 711 // 712 // 1. That the actual top of any area in a memory region 713 // contained by the space is bounded by the end of the contiguous 714 // region of the space. 715 // 2. That the space is really made up of objects and not just 716 // blocks. 717 718 class ContiguousSpaceDCTOC : public Filtering_DCTOC { 719 protected: 720 // Overrides. 721 HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj); 722 723 virtual void walk_mem_region_with_cl(MemRegion mr, 724 HeapWord* bottom, HeapWord* top, 725 ExtendedOopClosure* cl); 726 virtual void walk_mem_region_with_cl(MemRegion mr, 727 HeapWord* bottom, HeapWord* top, 728 FilteringClosure* cl); 729 730 public: 731 ContiguousSpaceDCTOC(ContiguousSpace* sp, ExtendedOopClosure* cl, 732 CardTableModRefBS::PrecisionStyle precision, 733 HeapWord* boundary) : 734 Filtering_DCTOC(sp, cl, precision, boundary) 735 {} 736 }; 737 738 // A ContigSpace that Supports an efficient "block_start" operation via 739 // a BlockOffsetArray (whose BlockOffsetSharedArray may be shared with 740 // other spaces.) This is the abstract base class for old generation 741 // (tenured) spaces. 742 743 class OffsetTableContigSpace: public ContiguousSpace { 744 friend class VMStructs; 745 protected: 746 BlockOffsetArrayContigSpace _offsets; 747 Mutex _par_alloc_lock; 748 749 public: 750 // Constructor 751 OffsetTableContigSpace(BlockOffsetSharedArray* sharedOffsetArray, 752 MemRegion mr); 753 754 void set_bottom(HeapWord* value); 755 void set_end(HeapWord* value); 756 757 void clear(bool mangle_space); 758 759 inline HeapWord* block_start_const(const void* p) const; 760 761 // Add offset table update. 762 virtual inline HeapWord* allocate(size_t word_size); 763 inline HeapWord* par_allocate(size_t word_size); 764 765 // MarkSweep support phase3 766 virtual HeapWord* initialize_threshold(); 767 virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* end); 768 769 virtual void print_on(outputStream* st) const; 770 771 // Debugging 772 void verify() const; 773 }; 774 775 776 // Class TenuredSpace is used by TenuredGeneration 777 778 class TenuredSpace: public OffsetTableContigSpace { 779 friend class VMStructs; 780 protected: 781 // Mark sweep support 782 size_t allowed_dead_ratio() const; 783 public: 784 // Constructor 785 TenuredSpace(BlockOffsetSharedArray* sharedOffsetArray, 786 MemRegion mr) : 787 OffsetTableContigSpace(sharedOffsetArray, mr) {} 788 }; 789 #endif // SHARE_VM_GC_SHARED_SPACE_HPP