1 /* 2 * Copyright (c) 1997, 2016, 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 virtual void print() const; 224 virtual void print_on(outputStream* st) const; 225 virtual void print_short() const; 226 virtual void print_short_on(outputStream* st) const; 227 228 229 // Accessor for parallel sequential tasks. 230 SequentialSubTasksDone* par_seq_tasks() { return &_par_seq_tasks; } 231 232 // IF "this" is a ContiguousSpace, return it, else return NULL. 233 virtual ContiguousSpace* toContiguousSpace() { 234 return NULL; 235 } 236 237 // Debugging 238 virtual void verify() const = 0; 239 }; 240 241 // A MemRegionClosure (ResourceObj) whose "do_MemRegion" function applies an 242 // OopClosure to (the addresses of) all the ref-containing fields that could 243 // be modified by virtue of the given MemRegion being dirty. (Note that 244 // because of the imprecise nature of the write barrier, this may iterate 245 // over oops beyond the region.) 246 // This base type for dirty card to oop closures handles memory regions 247 // in non-contiguous spaces with no boundaries, and should be sub-classed 248 // to support other space types. See ContiguousDCTOC for a sub-class 249 // that works with ContiguousSpaces. 250 251 class DirtyCardToOopClosure: public MemRegionClosureRO { 252 protected: 253 ExtendedOopClosure* _cl; 254 Space* _sp; 255 CardTableModRefBS::PrecisionStyle _precision; 256 HeapWord* _boundary; // If non-NULL, process only non-NULL oops 257 // pointing below boundary. 258 HeapWord* _min_done; // ObjHeadPreciseArray precision requires 259 // a downwards traversal; this is the 260 // lowest location already done (or, 261 // alternatively, the lowest address that 262 // shouldn't be done again. NULL means infinity.) 263 NOT_PRODUCT(HeapWord* _last_bottom;) 264 NOT_PRODUCT(HeapWord* _last_explicit_min_done;) 265 266 // Get the actual top of the area on which the closure will 267 // operate, given where the top is assumed to be (the end of the 268 // memory region passed to do_MemRegion) and where the object 269 // at the top is assumed to start. For example, an object may 270 // start at the top but actually extend past the assumed top, 271 // in which case the top becomes the end of the object. 272 virtual HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj); 273 274 // Walk the given memory region from bottom to (actual) top 275 // looking for objects and applying the oop closure (_cl) to 276 // them. The base implementation of this treats the area as 277 // blocks, where a block may or may not be an object. Sub- 278 // classes should override this to provide more accurate 279 // or possibly more efficient walking. 280 virtual void walk_mem_region(MemRegion mr, HeapWord* bottom, HeapWord* top); 281 282 public: 283 DirtyCardToOopClosure(Space* sp, ExtendedOopClosure* cl, 284 CardTableModRefBS::PrecisionStyle precision, 285 HeapWord* boundary) : 286 _sp(sp), _cl(cl), _precision(precision), _boundary(boundary), 287 _min_done(NULL) { 288 NOT_PRODUCT(_last_bottom = NULL); 289 NOT_PRODUCT(_last_explicit_min_done = NULL); 290 } 291 292 void do_MemRegion(MemRegion mr); 293 294 void set_min_done(HeapWord* min_done) { 295 _min_done = min_done; 296 NOT_PRODUCT(_last_explicit_min_done = _min_done); 297 } 298 #ifndef PRODUCT 299 void set_last_bottom(HeapWord* last_bottom) { 300 _last_bottom = last_bottom; 301 } 302 #endif 303 }; 304 305 // A structure to represent a point at which objects are being copied 306 // during compaction. 307 class CompactPoint : public StackObj { 308 public: 309 Generation* gen; 310 CompactibleSpace* space; 311 HeapWord* threshold; 312 313 CompactPoint(Generation* g = NULL) : 314 gen(g), space(NULL), threshold(0) {} 315 }; 316 317 // A space that supports compaction operations. This is usually, but not 318 // necessarily, a space that is normally contiguous. But, for example, a 319 // free-list-based space whose normal collection is a mark-sweep without 320 // compaction could still support compaction in full GC's. 321 // 322 // The compaction operations are implemented by the 323 // scan_and_{adjust_pointers,compact,forward} function templates. 324 // The following are, non-virtual, auxiliary functions used by these function templates: 325 // - scan_limit() 326 // - scanned_block_is_obj() 327 // - scanned_block_size() 328 // - adjust_obj_size() 329 // - obj_size() 330 // These functions are to be used exclusively by the scan_and_* function templates, 331 // and must be defined for all (non-abstract) subclasses of CompactibleSpace. 332 // 333 // NOTE: Any subclasses to CompactibleSpace wanting to change/define the behavior 334 // in any of the auxiliary functions must also override the corresponding 335 // prepare_for_compaction/adjust_pointers/compact functions using them. 336 // If not, such changes will not be used or have no effect on the compaction operations. 337 // 338 // This translates to the following dependencies: 339 // Overrides/definitions of 340 // - scan_limit 341 // - scanned_block_is_obj 342 // - scanned_block_size 343 // require override/definition of prepare_for_compaction(). 344 // Similar dependencies exist between 345 // - adjust_obj_size and adjust_pointers() 346 // - obj_size and compact(). 347 // 348 // Additionally, this also means that changes to block_size() or block_is_obj() that 349 // should be effective during the compaction operations must provide a corresponding 350 // definition of scanned_block_size/scanned_block_is_obj respectively. 351 class CompactibleSpace: public Space { 352 friend class VMStructs; 353 friend class CompactibleFreeListSpace; 354 private: 355 HeapWord* _compaction_top; 356 CompactibleSpace* _next_compaction_space; 357 358 // Auxiliary functions for scan_and_{forward,adjust_pointers,compact} support. 359 inline size_t adjust_obj_size(size_t size) const { 360 return size; 361 } 362 363 inline size_t obj_size(const HeapWord* addr) const; 364 365 void verify_up_to_first_dead() PRODUCT_RETURN; 366 367 public: 368 CompactibleSpace() : 369 _compaction_top(NULL), _next_compaction_space(NULL) {} 370 371 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space); 372 virtual void clear(bool mangle_space); 373 374 // Used temporarily during a compaction phase to hold the value 375 // top should have when compaction is complete. 376 HeapWord* compaction_top() const { return _compaction_top; } 377 378 void set_compaction_top(HeapWord* value) { 379 assert(value == NULL || (value >= bottom() && value <= end()), 380 "should point inside space"); 381 _compaction_top = value; 382 } 383 384 // Perform operations on the space needed after a compaction 385 // has been performed. 386 virtual void reset_after_compaction() = 0; 387 388 // Returns the next space (in the current generation) to be compacted in 389 // the global compaction order. Also is used to select the next 390 // space into which to compact. 391 392 virtual CompactibleSpace* next_compaction_space() const { 393 return _next_compaction_space; 394 } 395 396 void set_next_compaction_space(CompactibleSpace* csp) { 397 _next_compaction_space = csp; 398 } 399 400 // MarkSweep support phase2 401 402 // Start the process of compaction of the current space: compute 403 // post-compaction addresses, and insert forwarding pointers. The fields 404 // "cp->gen" and "cp->compaction_space" are the generation and space into 405 // which we are currently compacting. This call updates "cp" as necessary, 406 // and leaves the "compaction_top" of the final value of 407 // "cp->compaction_space" up-to-date. Offset tables may be updated in 408 // this phase as if the final copy had occurred; if so, "cp->threshold" 409 // indicates when the next such action should be taken. 410 virtual void prepare_for_compaction(CompactPoint* cp) = 0; 411 // MarkSweep support phase3 412 virtual void adjust_pointers(); 413 // MarkSweep support phase4 414 virtual void compact(); 415 416 // The maximum percentage of objects that can be dead in the compacted 417 // live part of a compacted space ("deadwood" support.) 418 virtual size_t allowed_dead_ratio() const { return 0; }; 419 420 // Some contiguous spaces may maintain some data structures that should 421 // be updated whenever an allocation crosses a boundary. This function 422 // returns the first such boundary. 423 // (The default implementation returns the end of the space, so the 424 // boundary is never crossed.) 425 virtual HeapWord* initialize_threshold() { return end(); } 426 427 // "q" is an object of the given "size" that should be forwarded; 428 // "cp" names the generation ("gen") and containing "this" (which must 429 // also equal "cp->space"). "compact_top" is where in "this" the 430 // next object should be forwarded to. If there is room in "this" for 431 // the object, insert an appropriate forwarding pointer in "q". 432 // If not, go to the next compaction space (there must 433 // be one, since compaction must succeed -- we go to the first space of 434 // the previous generation if necessary, updating "cp"), reset compact_top 435 // and then forward. In either case, returns the new value of "compact_top". 436 // If the forwarding crosses "cp->threshold", invokes the "cross_threshold" 437 // function of the then-current compaction space, and updates "cp->threshold 438 // accordingly". 439 virtual HeapWord* forward(oop q, size_t size, CompactPoint* cp, 440 HeapWord* compact_top); 441 442 // Return a size with adjustments as required of the space. 443 virtual size_t adjust_object_size_v(size_t size) const { return size; } 444 445 protected: 446 // Used during compaction. 447 HeapWord* _first_dead; 448 HeapWord* _end_of_live; 449 450 // Minimum size of a free block. 451 virtual size_t minimum_free_block_size() const { return 0; } 452 453 // This the function is invoked when an allocation of an object covering 454 // "start" to "end occurs crosses the threshold; returns the next 455 // threshold. (The default implementation does nothing.) 456 virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* the_end) { 457 return end(); 458 } 459 460 // Below are template functions for scan_and_* algorithms (avoiding virtual calls). 461 // The space argument should be a subclass of CompactibleSpace, implementing 462 // scan_limit(), scanned_block_is_obj(), and scanned_block_size(), 463 // and possibly also overriding obj_size(), and adjust_obj_size(). 464 // These functions should avoid virtual calls whenever possible. 465 466 // Frequently calls adjust_obj_size(). 467 template <class SpaceType> 468 static inline void scan_and_adjust_pointers(SpaceType* space); 469 470 // Frequently calls obj_size(). 471 template <class SpaceType> 472 static inline void scan_and_compact(SpaceType* space); 473 474 // Frequently calls scanned_block_is_obj() and scanned_block_size(). 475 // Requires the scan_limit() function. 476 template <class SpaceType> 477 static inline void scan_and_forward(SpaceType* space, CompactPoint* cp); 478 }; 479 480 class GenSpaceMangler; 481 482 // A space in which the free area is contiguous. It therefore supports 483 // faster allocation, and compaction. 484 class ContiguousSpace: public CompactibleSpace { 485 friend class VMStructs; 486 // Allow scan_and_forward function to call (private) overrides for auxiliary functions on this class 487 template <typename SpaceType> 488 friend void CompactibleSpace::scan_and_forward(SpaceType* space, CompactPoint* cp); 489 490 private: 491 // Auxiliary functions for scan_and_forward support. 492 // See comments for CompactibleSpace for more information. 493 inline HeapWord* scan_limit() const { 494 return top(); 495 } 496 497 inline bool scanned_block_is_obj(const HeapWord* addr) const { 498 return true; // Always true, since scan_limit is top 499 } 500 501 inline size_t scanned_block_size(const HeapWord* addr) const; 502 503 protected: 504 HeapWord* _top; 505 HeapWord* _concurrent_iteration_safe_limit; 506 // A helper for mangling the unused area of the space in debug builds. 507 GenSpaceMangler* _mangler; 508 509 GenSpaceMangler* mangler() { return _mangler; } 510 511 // Allocation helpers (return NULL if full). 512 inline HeapWord* allocate_impl(size_t word_size); 513 inline HeapWord* par_allocate_impl(size_t word_size); 514 515 public: 516 ContiguousSpace(); 517 ~ContiguousSpace(); 518 519 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space); 520 virtual void clear(bool mangle_space); 521 522 // Accessors 523 HeapWord* top() const { return _top; } 524 void set_top(HeapWord* value) { _top = value; } 525 526 void set_saved_mark() { _saved_mark_word = top(); } 527 void reset_saved_mark() { _saved_mark_word = bottom(); } 528 529 bool saved_mark_at_top() const { return saved_mark_word() == top(); } 530 531 // In debug mode mangle (write it with a particular bit 532 // pattern) the unused part of a space. 533 534 // Used to save the an address in a space for later use during mangling. 535 void set_top_for_allocations(HeapWord* v) PRODUCT_RETURN; 536 // Used to save the space's current top for later use during mangling. 537 void set_top_for_allocations() PRODUCT_RETURN; 538 539 // Mangle regions in the space from the current top up to the 540 // previously mangled part of the space. 541 void mangle_unused_area() PRODUCT_RETURN; 542 // Mangle [top, end) 543 void mangle_unused_area_complete() PRODUCT_RETURN; 544 545 // Do some sparse checking on the area that should have been mangled. 546 void check_mangled_unused_area(HeapWord* limit) PRODUCT_RETURN; 547 // Check the complete area that should have been mangled. 548 // This code may be NULL depending on the macro DEBUG_MANGLING. 549 void check_mangled_unused_area_complete() PRODUCT_RETURN; 550 551 // Size computations: sizes in bytes. 552 size_t capacity() const { return byte_size(bottom(), end()); } 553 size_t used() const { return byte_size(bottom(), top()); } 554 size_t free() const { return byte_size(top(), end()); } 555 556 virtual bool is_free_block(const HeapWord* p) const; 557 558 // In a contiguous space we have a more obvious bound on what parts 559 // contain objects. 560 MemRegion used_region() const { return MemRegion(bottom(), top()); } 561 562 // Allocation (return NULL if full) 563 virtual HeapWord* allocate(size_t word_size); 564 virtual HeapWord* par_allocate(size_t word_size); 565 HeapWord* allocate_aligned(size_t word_size); 566 567 // Iteration 568 void oop_iterate(ExtendedOopClosure* cl); 569 void object_iterate(ObjectClosure* blk); 570 // For contiguous spaces this method will iterate safely over objects 571 // in the space (i.e., between bottom and top) when at a safepoint. 572 void safe_object_iterate(ObjectClosure* blk); 573 574 // Iterate over as many initialized objects in the space as possible, 575 // calling "cl.do_object_careful" on each. Return NULL if all objects 576 // in the space (at the start of the iteration) were iterated over. 577 // Return an address indicating the extent of the iteration in the 578 // event that the iteration had to return because of finding an 579 // uninitialized object in the space, or if the closure "cl" 580 // signaled early termination. 581 HeapWord* object_iterate_careful(ObjectClosureCareful* cl); 582 HeapWord* concurrent_iteration_safe_limit() { 583 assert(_concurrent_iteration_safe_limit <= top(), 584 "_concurrent_iteration_safe_limit update missed"); 585 return _concurrent_iteration_safe_limit; 586 } 587 // changes the safe limit, all objects from bottom() to the new 588 // limit should be properly initialized 589 void set_concurrent_iteration_safe_limit(HeapWord* new_limit) { 590 assert(new_limit <= top(), "uninitialized objects in the safe range"); 591 _concurrent_iteration_safe_limit = new_limit; 592 } 593 594 595 #if INCLUDE_ALL_GCS 596 // In support of parallel oop_iterate. 597 #define ContigSpace_PAR_OOP_ITERATE_DECL(OopClosureType, nv_suffix) \ 598 void par_oop_iterate(MemRegion mr, OopClosureType* blk); 599 600 ALL_PAR_OOP_ITERATE_CLOSURES(ContigSpace_PAR_OOP_ITERATE_DECL) 601 #undef ContigSpace_PAR_OOP_ITERATE_DECL 602 #endif // INCLUDE_ALL_GCS 603 604 // Compaction support 605 virtual void reset_after_compaction() { 606 assert(compaction_top() >= bottom() && compaction_top() <= end(), "should point inside space"); 607 set_top(compaction_top()); 608 // set new iteration safe limit 609 set_concurrent_iteration_safe_limit(compaction_top()); 610 } 611 612 // Override. 613 DirtyCardToOopClosure* new_dcto_cl(ExtendedOopClosure* cl, 614 CardTableModRefBS::PrecisionStyle precision, 615 HeapWord* boundary, 616 bool parallel); 617 618 // Apply "blk->do_oop" to the addresses of all reference fields in objects 619 // starting with the _saved_mark_word, which was noted during a generation's 620 // save_marks and is required to denote the head of an object. 621 // Fields in objects allocated by applications of the closure 622 // *are* included in the iteration. 623 // Updates _saved_mark_word to point to just after the last object 624 // iterated over. 625 #define ContigSpace_OOP_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \ 626 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk); 627 628 ALL_SINCE_SAVE_MARKS_CLOSURES(ContigSpace_OOP_SINCE_SAVE_MARKS_DECL) 629 #undef ContigSpace_OOP_SINCE_SAVE_MARKS_DECL 630 631 // Same as object_iterate, but starting from "mark", which is required 632 // to denote the start of an object. Objects allocated by 633 // applications of the closure *are* included in the iteration. 634 virtual void object_iterate_from(HeapWord* mark, ObjectClosure* blk); 635 636 // Very inefficient implementation. 637 virtual HeapWord* block_start_const(const void* p) const; 638 size_t block_size(const HeapWord* p) const; 639 // If a block is in the allocated area, it is an object. 640 bool block_is_obj(const HeapWord* p) const { return p < top(); } 641 642 // Addresses for inlined allocation 643 HeapWord** top_addr() { return &_top; } 644 HeapWord** end_addr() { return &_end; } 645 646 // Overrides for more efficient compaction support. 647 void prepare_for_compaction(CompactPoint* cp); 648 649 virtual void print_on(outputStream* st) const; 650 651 // Checked dynamic downcasts. 652 virtual ContiguousSpace* toContiguousSpace() { 653 return this; 654 } 655 656 // Debugging 657 virtual void verify() const; 658 659 // Used to increase collection frequency. "factor" of 0 means entire 660 // space. 661 void allocate_temporary_filler(int factor); 662 }; 663 664 665 // A dirty card to oop closure that does filtering. 666 // It knows how to filter out objects that are outside of the _boundary. 667 class FilteringDCTOC : public DirtyCardToOopClosure { 668 protected: 669 // Override. 670 void walk_mem_region(MemRegion mr, 671 HeapWord* bottom, HeapWord* top); 672 673 // Walk the given memory region, from bottom to top, applying 674 // the given oop closure to (possibly) all objects found. The 675 // given oop closure may or may not be the same as the oop 676 // closure with which this closure was created, as it may 677 // be a filtering closure which makes use of the _boundary. 678 // We offer two signatures, so the FilteringClosure static type is 679 // apparent. 680 virtual void walk_mem_region_with_cl(MemRegion mr, 681 HeapWord* bottom, HeapWord* top, 682 ExtendedOopClosure* cl) = 0; 683 virtual void walk_mem_region_with_cl(MemRegion mr, 684 HeapWord* bottom, HeapWord* top, 685 FilteringClosure* cl) = 0; 686 687 public: 688 FilteringDCTOC(Space* sp, ExtendedOopClosure* cl, 689 CardTableModRefBS::PrecisionStyle precision, 690 HeapWord* boundary) : 691 DirtyCardToOopClosure(sp, cl, precision, boundary) {} 692 }; 693 694 // A dirty card to oop closure for contiguous spaces 695 // (ContiguousSpace and sub-classes). 696 // It is a FilteringClosure, as defined above, and it knows: 697 // 698 // 1. That the actual top of any area in a memory region 699 // contained by the space is bounded by the end of the contiguous 700 // region of the space. 701 // 2. That the space is really made up of objects and not just 702 // blocks. 703 704 class ContiguousSpaceDCTOC : public FilteringDCTOC { 705 protected: 706 // Overrides. 707 HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj); 708 709 virtual void walk_mem_region_with_cl(MemRegion mr, 710 HeapWord* bottom, HeapWord* top, 711 ExtendedOopClosure* cl); 712 virtual void walk_mem_region_with_cl(MemRegion mr, 713 HeapWord* bottom, HeapWord* top, 714 FilteringClosure* cl); 715 716 public: 717 ContiguousSpaceDCTOC(ContiguousSpace* sp, ExtendedOopClosure* cl, 718 CardTableModRefBS::PrecisionStyle precision, 719 HeapWord* boundary) : 720 FilteringDCTOC(sp, cl, precision, boundary) 721 {} 722 }; 723 724 // A ContigSpace that Supports an efficient "block_start" operation via 725 // a BlockOffsetArray (whose BlockOffsetSharedArray may be shared with 726 // other spaces.) This is the abstract base class for old generation 727 // (tenured) spaces. 728 729 class OffsetTableContigSpace: public ContiguousSpace { 730 friend class VMStructs; 731 protected: 732 BlockOffsetArrayContigSpace _offsets; 733 Mutex _par_alloc_lock; 734 735 public: 736 // Constructor 737 OffsetTableContigSpace(BlockOffsetSharedArray* sharedOffsetArray, 738 MemRegion mr); 739 740 void set_bottom(HeapWord* value); 741 void set_end(HeapWord* value); 742 743 void clear(bool mangle_space); 744 745 inline HeapWord* block_start_const(const void* p) const; 746 747 // Add offset table update. 748 virtual inline HeapWord* allocate(size_t word_size); 749 inline HeapWord* par_allocate(size_t word_size); 750 751 // MarkSweep support phase3 752 virtual HeapWord* initialize_threshold(); 753 virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* end); 754 755 virtual void print_on(outputStream* st) const; 756 757 // Debugging 758 void verify() const; 759 }; 760 761 762 // Class TenuredSpace is used by TenuredGeneration 763 764 class TenuredSpace: public OffsetTableContigSpace { 765 friend class VMStructs; 766 protected: 767 // Mark sweep support 768 size_t allowed_dead_ratio() const; 769 public: 770 // Constructor 771 TenuredSpace(BlockOffsetSharedArray* sharedOffsetArray, 772 MemRegion mr) : 773 OffsetTableContigSpace(sharedOffsetArray, mr) {} 774 }; 775 #endif // SHARE_VM_GC_SHARED_SPACE_HPP