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_MEMORY_SPACE_HPP 26 #define SHARE_VM_MEMORY_SPACE_HPP 27 28 #include "memory/allocation.hpp" 29 #include "memory/blockOffsetTable.hpp" 30 #include "memory/cardTableModRefBS.hpp" 31 #include "memory/iterator.hpp" 32 #include "memory/memRegion.hpp" 33 #include "memory/watermark.hpp" 34 #include "oops/markOop.hpp" 35 #include "runtime/mutexLocker.hpp" 36 #include "utilities/macros.hpp" 37 #include "utilities/workgroup.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 GenRemSet; 52 class CardTableRS; 53 class DirtyCardToOopClosure; 54 55 // A Space describes a heap area. Class Space is an abstract 56 // base class. 57 // 58 // Space supports allocation, size computation and GC support is provided. 59 // 60 // Invariant: bottom() and end() are on page_size boundaries and 61 // bottom() <= top() <= end() 62 // top() is inclusive and end() is exclusive. 63 64 class Space: public CHeapObj<mtGC> { 65 friend class VMStructs; 66 protected: 67 HeapWord* _bottom; 68 HeapWord* _end; 69 70 // Used in support of save_marks() 71 HeapWord* _saved_mark_word; 72 73 // A sequential tasks done structure. This supports 74 // parallel GC, where we have threads dynamically 75 // claiming sub-tasks from a larger parallel task. 76 SequentialSubTasksDone _par_seq_tasks; 77 78 Space(): 79 _bottom(NULL), _end(NULL) { } 80 81 public: 82 // Accessors 83 HeapWord* bottom() const { return _bottom; } 84 HeapWord* end() const { return _end; } 85 virtual void set_bottom(HeapWord* value) { _bottom = value; } 86 virtual void set_end(HeapWord* value) { _end = value; } 87 88 virtual HeapWord* saved_mark_word() const { return _saved_mark_word; } 89 90 void set_saved_mark_word(HeapWord* p) { _saved_mark_word = p; } 91 92 // Returns true if this object has been allocated since a 93 // generation's "save_marks" call. 94 virtual bool obj_allocated_since_save_marks(const oop obj) const { 95 return (HeapWord*)obj >= saved_mark_word(); 96 } 97 98 virtual MemRegionClosure* preconsumptionDirtyCardClosure() const { 99 return NULL; 100 } 101 102 // Returns a subregion of the space containing only the allocated objects in 103 // the space. 104 virtual MemRegion used_region() const = 0; 105 106 // Returns a region that is guaranteed to contain (at least) all objects 107 // allocated at the time of the last call to "save_marks". If the space 108 // initializes its DirtyCardToOopClosure's specifying the "contig" option 109 // (that is, if the space is contiguous), then this region must contain only 110 // such objects: the memregion will be from the bottom of the region to the 111 // saved mark. Otherwise, the "obj_allocated_since_save_marks" method of 112 // the space must distinguish between objects in the region allocated before 113 // and after the call to save marks. 114 MemRegion used_region_at_save_marks() const { 115 return MemRegion(bottom(), saved_mark_word()); 116 } 117 118 // Initialization. 119 // "initialize" should be called once on a space, before it is used for 120 // any purpose. The "mr" arguments gives the bounds of the space, and 121 // the "clear_space" argument should be true unless the memory in "mr" is 122 // known to be zeroed. 123 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space); 124 125 // The "clear" method must be called on a region that may have 126 // had allocation performed in it, but is now to be considered empty. 127 virtual void clear(bool mangle_space); 128 129 // For detecting GC bugs. Should only be called at GC boundaries, since 130 // some unused space may be used as scratch space during GC's. 131 // We also call this when expanding a space to satisfy an allocation 132 // request. See bug #4668531 133 virtual void mangle_unused_area() = 0; 134 virtual void mangle_unused_area_complete() = 0; 135 136 // Testers 137 bool is_empty() const { return used() == 0; } 138 bool not_empty() const { return used() > 0; } 139 140 // Returns true iff the given the space contains the 141 // given address as part of an allocated object. For 142 // certain kinds of spaces, this might be a potentially 143 // expensive operation. To prevent performance problems 144 // on account of its inadvertent use in product jvm's, 145 // we restrict its use to assertion checks only. 146 bool is_in(const void* p) const { 147 return used_region().contains(p); 148 } 149 150 // Returns true iff the given reserved memory of the space contains the 151 // given address. 152 bool is_in_reserved(const void* p) const { return _bottom <= p && p < _end; } 153 154 // Returns true iff the given block is not allocated. 155 virtual bool is_free_block(const HeapWord* p) const = 0; 156 157 // Test whether p is double-aligned 158 static bool is_aligned(void* p) { 159 return ((intptr_t)p & (sizeof(double)-1)) == 0; 160 } 161 162 // Size computations. Sizes are in bytes. 163 size_t capacity() const { return byte_size(bottom(), end()); } 164 virtual size_t used() const = 0; 165 virtual size_t free() const = 0; 166 167 // Iterate over all the ref-containing fields of all objects in the 168 // space, calling "cl.do_oop" on each. Fields in objects allocated by 169 // applications of the closure are not included in the iteration. 170 virtual void oop_iterate(ExtendedOopClosure* cl); 171 172 // Iterate over all objects in the space, calling "cl.do_object" on 173 // each. Objects allocated by applications of the closure are not 174 // included in the iteration. 175 virtual void object_iterate(ObjectClosure* blk) = 0; 176 // Similar to object_iterate() except only iterates over 177 // objects whose internal references point to objects in the space. 178 virtual void safe_object_iterate(ObjectClosure* blk) = 0; 179 180 // Create and return a new dirty card to oop closure. Can be 181 // overridden to return the appropriate type of closure 182 // depending on the type of space in which the closure will 183 // operate. ResourceArea allocated. 184 virtual DirtyCardToOopClosure* new_dcto_cl(ExtendedOopClosure* cl, 185 CardTableModRefBS::PrecisionStyle precision, 186 HeapWord* boundary = NULL); 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 // PrintHeapAtGC support 225 virtual void print() const; 226 virtual void print_on(outputStream* st) const; 227 virtual void print_short() const; 228 virtual void print_short_on(outputStream* st) const; 229 230 231 // Accessor for parallel sequential tasks. 232 SequentialSubTasksDone* par_seq_tasks() { return &_par_seq_tasks; } 233 234 // IF "this" is a ContiguousSpace, return it, else return NULL. 235 virtual ContiguousSpace* toContiguousSpace() { 236 return NULL; 237 } 238 239 // Debugging 240 virtual void verify() const = 0; 241 }; 242 243 // A MemRegionClosure (ResourceObj) whose "do_MemRegion" function applies an 244 // OopClosure to (the addresses of) all the ref-containing fields that could 245 // be modified by virtue of the given MemRegion being dirty. (Note that 246 // because of the imprecise nature of the write barrier, this may iterate 247 // over oops beyond the region.) 248 // This base type for dirty card to oop closures handles memory regions 249 // in non-contiguous spaces with no boundaries, and should be sub-classed 250 // to support other space types. See ContiguousDCTOC for a sub-class 251 // that works with ContiguousSpaces. 252 253 class DirtyCardToOopClosure: public MemRegionClosureRO { 254 protected: 255 ExtendedOopClosure* _cl; 256 Space* _sp; 257 CardTableModRefBS::PrecisionStyle _precision; 258 HeapWord* _boundary; // If non-NULL, process only non-NULL oops 259 // pointing below boundary. 260 HeapWord* _min_done; // ObjHeadPreciseArray precision requires 261 // a downwards traversal; this is the 262 // lowest location already done (or, 263 // alternatively, the lowest address that 264 // shouldn't be done again. NULL means infinity.) 265 NOT_PRODUCT(HeapWord* _last_bottom;) 266 NOT_PRODUCT(HeapWord* _last_explicit_min_done;) 267 268 // Get the actual top of the area on which the closure will 269 // operate, given where the top is assumed to be (the end of the 270 // memory region passed to do_MemRegion) and where the object 271 // at the top is assumed to start. For example, an object may 272 // start at the top but actually extend past the assumed top, 273 // in which case the top becomes the end of the object. 274 virtual HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj); 275 276 // Walk the given memory region from bottom to (actual) top 277 // looking for objects and applying the oop closure (_cl) to 278 // them. The base implementation of this treats the area as 279 // blocks, where a block may or may not be an object. Sub- 280 // classes should override this to provide more accurate 281 // or possibly more efficient walking. 282 virtual void walk_mem_region(MemRegion mr, HeapWord* bottom, HeapWord* top); 283 284 public: 285 DirtyCardToOopClosure(Space* sp, ExtendedOopClosure* cl, 286 CardTableModRefBS::PrecisionStyle precision, 287 HeapWord* boundary) : 288 _sp(sp), _cl(cl), _precision(precision), _boundary(boundary), 289 _min_done(NULL) { 290 NOT_PRODUCT(_last_bottom = NULL); 291 NOT_PRODUCT(_last_explicit_min_done = NULL); 292 } 293 294 void do_MemRegion(MemRegion mr); 295 296 void set_min_done(HeapWord* min_done) { 297 _min_done = min_done; 298 NOT_PRODUCT(_last_explicit_min_done = _min_done); 299 } 300 #ifndef PRODUCT 301 void set_last_bottom(HeapWord* last_bottom) { 302 _last_bottom = last_bottom; 303 } 304 #endif 305 }; 306 307 // A structure to represent a point at which objects are being copied 308 // during compaction. 309 class CompactPoint : public StackObj { 310 public: 311 Generation* gen; 312 CompactibleSpace* space; 313 HeapWord* threshold; 314 315 CompactPoint(Generation* g = NULL) : 316 gen(g), space(NULL), threshold(0) {} 317 }; 318 319 // A space that supports compaction operations. This is usually, but not 320 // necessarily, a space that is normally contiguous. But, for example, a 321 // free-list-based space whose normal collection is a mark-sweep without 322 // compaction could still support compaction in full GC's. 323 // 324 // The compaction operations are implemented by the 325 // scan_and_{adjust_pointers,compact,forward} function templates. 326 // The following are, non-virtual, auxiliary functions used by these function templates: 327 // - scan_limit() 328 // - scanned_block_is_obj() 329 // - scanned_block_size() 330 // - adjust_obj_size() 331 // - obj_size() 332 // These functions are to be used exclusively by the scan_and_* function templates, 333 // and must be defined for all (non-abstract) subclasses of CompactibleSpace. 334 // 335 // NOTE: Any subclasses to CompactibleSpace wanting to change/define the behavior 336 // in any of the auxiliary functions must also override the corresponding 337 // prepare_for_compaction/adjust_pointers/compact functions using them. 338 // If not, such changes will not be used or have no effect on the compaction operations. 339 // 340 // This translates to the following dependencies: 341 // Overrides/definitions of 342 // - scan_limit 343 // - scanned_block_is_obj 344 // - scanned_block_size 345 // require override/definition of prepare_for_compaction(). 346 // Similar dependencies exist between 347 // - adjust_obj_size and adjust_pointers() 348 // - obj_size and compact(). 349 // 350 // Additionally, this also means that changes to block_size() or block_is_obj() that 351 // should be effective during the compaction operations must provide a corresponding 352 // definition of scanned_block_size/scanned_block_is_obj respectively. 353 class CompactibleSpace: public Space { 354 friend class VMStructs; 355 friend class CompactibleFreeListSpace; 356 private: 357 HeapWord* _compaction_top; 358 CompactibleSpace* _next_compaction_space; 359 360 // Auxiliary functions for scan_and_{forward,adjust_pointers,compact} support. 361 inline size_t adjust_obj_size(size_t size) const { 362 return size; 363 } 364 365 inline size_t obj_size(const HeapWord* addr) const { 366 return oop(addr)->size(); 367 } 368 369 public: 370 CompactibleSpace() : 371 _compaction_top(NULL), _next_compaction_space(NULL) {} 372 373 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space); 374 virtual void clear(bool mangle_space); 375 376 // Used temporarily during a compaction phase to hold the value 377 // top should have when compaction is complete. 378 HeapWord* compaction_top() const { return _compaction_top; } 379 380 void set_compaction_top(HeapWord* value) { 381 assert(value == NULL || (value >= bottom() && value <= end()), 382 "should point inside space"); 383 _compaction_top = value; 384 } 385 386 // Perform operations on the space needed after a compaction 387 // has been performed. 388 virtual void reset_after_compaction() = 0; 389 390 // Returns the next space (in the current generation) to be compacted in 391 // the global compaction order. Also is used to select the next 392 // space into which to compact. 393 394 virtual CompactibleSpace* next_compaction_space() const { 395 return _next_compaction_space; 396 } 397 398 void set_next_compaction_space(CompactibleSpace* csp) { 399 _next_compaction_space = csp; 400 } 401 402 // MarkSweep support phase2 403 404 // Start the process of compaction of the current space: compute 405 // post-compaction addresses, and insert forwarding pointers. The fields 406 // "cp->gen" and "cp->compaction_space" are the generation and space into 407 // which we are currently compacting. This call updates "cp" as necessary, 408 // and leaves the "compaction_top" of the final value of 409 // "cp->compaction_space" up-to-date. Offset tables may be updated in 410 // this phase as if the final copy had occurred; if so, "cp->threshold" 411 // indicates when the next such action should be taken. 412 virtual void prepare_for_compaction(CompactPoint* cp) = 0; 413 // MarkSweep support phase3 414 virtual void adjust_pointers(); 415 // MarkSweep support phase4 416 virtual void compact(); 417 418 // The maximum percentage of objects that can be dead in the compacted 419 // live part of a compacted space ("deadwood" support.) 420 virtual size_t allowed_dead_ratio() const { return 0; }; 421 422 // Some contiguous spaces may maintain some data structures that should 423 // be updated whenever an allocation crosses a boundary. This function 424 // returns the first such boundary. 425 // (The default implementation returns the end of the space, so the 426 // boundary is never crossed.) 427 virtual HeapWord* initialize_threshold() { return end(); } 428 429 // "q" is an object of the given "size" that should be forwarded; 430 // "cp" names the generation ("gen") and containing "this" (which must 431 // also equal "cp->space"). "compact_top" is where in "this" the 432 // next object should be forwarded to. If there is room in "this" for 433 // the object, insert an appropriate forwarding pointer in "q". 434 // If not, go to the next compaction space (there must 435 // be one, since compaction must succeed -- we go to the first space of 436 // the previous generation if necessary, updating "cp"), reset compact_top 437 // and then forward. In either case, returns the new value of "compact_top". 438 // If the forwarding crosses "cp->threshold", invokes the "cross_threshold" 439 // function of the then-current compaction space, and updates "cp->threshold 440 // accordingly". 441 virtual HeapWord* forward(oop q, size_t size, CompactPoint* cp, 442 HeapWord* compact_top); 443 444 // Return a size with adjustments as required of the space. 445 virtual size_t adjust_object_size_v(size_t size) const { return size; } 446 447 protected: 448 // Used during compaction. 449 HeapWord* _first_dead; 450 HeapWord* _end_of_live; 451 452 // Minimum size of a free block. 453 virtual size_t minimum_free_block_size() const { return 0; } 454 455 // This the function is invoked when an allocation of an object covering 456 // "start" to "end occurs crosses the threshold; returns the next 457 // threshold. (The default implementation does nothing.) 458 virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* the_end) { 459 return end(); 460 } 461 462 // Requires "allowed_deadspace_words > 0", that "q" is the start of a 463 // free block of the given "word_len", and that "q", were it an object, 464 // would not move if forwarded. If the size allows, fill the free 465 // block with an object, to prevent excessive compaction. Returns "true" 466 // iff the free region was made deadspace, and modifies 467 // "allowed_deadspace_words" to reflect the number of available deadspace 468 // words remaining after this operation. 469 bool insert_deadspace(size_t& allowed_deadspace_words, HeapWord* q, 470 size_t word_len); 471 472 // Below are template functions for scan_and_* algorithms (avoiding virtual calls). 473 // The space argument should be a subclass of CompactibleSpace, implementing 474 // scan_limit(), scanned_block_is_obj(), and scanned_block_size(), 475 // and possibly also overriding obj_size(), and adjust_obj_size(). 476 // These functions should avoid virtual calls whenever possible. 477 478 // Frequently calls adjust_obj_size(). 479 template <class SpaceType> 480 static inline void scan_and_adjust_pointers(SpaceType* space); 481 482 // Frequently calls obj_size(). 483 template <class SpaceType> 484 static inline void scan_and_compact(SpaceType* space); 485 486 // Frequently calls scanned_block_is_obj() and scanned_block_size(). 487 // Requires the scan_limit() function. 488 template <class SpaceType> 489 static inline void scan_and_forward(SpaceType* space, CompactPoint* cp); 490 }; 491 492 class GenSpaceMangler; 493 494 // A space in which the free area is contiguous. It therefore supports 495 // faster allocation, and compaction. 496 class ContiguousSpace: public CompactibleSpace { 497 friend class VMStructs; 498 // Allow scan_and_forward function to call (private) overrides for auxiliary functions on this class 499 template <typename SpaceType> 500 friend void CompactibleSpace::scan_and_forward(SpaceType* space, CompactPoint* cp); 501 502 private: 503 // Auxiliary functions for scan_and_forward support. 504 // See comments for CompactibleSpace for more information. 505 inline HeapWord* scan_limit() const { 506 return top(); 507 } 508 509 inline bool scanned_block_is_obj(const HeapWord* addr) const { 510 return true; // Always true, since scan_limit is top 511 } 512 513 inline size_t scanned_block_size(const HeapWord* addr) const { 514 return oop(addr)->size(); 515 } 516 517 protected: 518 HeapWord* _top; 519 HeapWord* _concurrent_iteration_safe_limit; 520 // A helper for mangling the unused area of the space in debug builds. 521 GenSpaceMangler* _mangler; 522 523 GenSpaceMangler* mangler() { return _mangler; } 524 525 // Allocation helpers (return NULL if full). 526 inline HeapWord* allocate_impl(size_t word_size); 527 inline HeapWord* par_allocate_impl(size_t word_size); 528 529 public: 530 ContiguousSpace(); 531 ~ContiguousSpace(); 532 533 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space); 534 virtual void clear(bool mangle_space); 535 536 // Accessors 537 HeapWord* top() const { return _top; } 538 void set_top(HeapWord* value) { _top = value; } 539 540 void set_saved_mark() { _saved_mark_word = top(); } 541 void reset_saved_mark() { _saved_mark_word = bottom(); } 542 543 WaterMark bottom_mark() { return WaterMark(this, bottom()); } 544 WaterMark top_mark() { return WaterMark(this, top()); } 545 WaterMark saved_mark() { return WaterMark(this, saved_mark_word()); } 546 bool saved_mark_at_top() const { return saved_mark_word() == top(); } 547 548 // In debug mode mangle (write it with a particular bit 549 // pattern) the unused part of a space. 550 551 // Used to save the an address in a space for later use during mangling. 552 void set_top_for_allocations(HeapWord* v) PRODUCT_RETURN; 553 // Used to save the space's current top for later use during mangling. 554 void set_top_for_allocations() PRODUCT_RETURN; 555 556 // Mangle regions in the space from the current top up to the 557 // previously mangled part of the space. 558 void mangle_unused_area() PRODUCT_RETURN; 559 // Mangle [top, end) 560 void mangle_unused_area_complete() PRODUCT_RETURN; 561 562 // Do some sparse checking on the area that should have been mangled. 563 void check_mangled_unused_area(HeapWord* limit) PRODUCT_RETURN; 564 // Check the complete area that should have been mangled. 565 // This code may be NULL depending on the macro DEBUG_MANGLING. 566 void check_mangled_unused_area_complete() PRODUCT_RETURN; 567 568 // Size computations: sizes in bytes. 569 size_t capacity() const { return byte_size(bottom(), end()); } 570 size_t used() const { return byte_size(bottom(), top()); } 571 size_t free() const { return byte_size(top(), end()); } 572 573 virtual bool is_free_block(const HeapWord* p) const; 574 575 // In a contiguous space we have a more obvious bound on what parts 576 // contain objects. 577 MemRegion used_region() const { return MemRegion(bottom(), top()); } 578 579 // Allocation (return NULL if full) 580 virtual HeapWord* allocate(size_t word_size); 581 virtual HeapWord* par_allocate(size_t word_size); 582 HeapWord* allocate_aligned(size_t word_size); 583 584 // Iteration 585 void oop_iterate(ExtendedOopClosure* cl); 586 void object_iterate(ObjectClosure* blk); 587 // For contiguous spaces this method will iterate safely over objects 588 // in the space (i.e., between bottom and top) when at a safepoint. 589 void safe_object_iterate(ObjectClosure* blk); 590 591 // Iterate over as many initialized objects in the space as possible, 592 // calling "cl.do_object_careful" on each. Return NULL if all objects 593 // in the space (at the start of the iteration) were iterated over. 594 // Return an address indicating the extent of the iteration in the 595 // event that the iteration had to return because of finding an 596 // uninitialized object in the space, or if the closure "cl" 597 // signaled early termination. 598 HeapWord* object_iterate_careful(ObjectClosureCareful* cl); 599 HeapWord* concurrent_iteration_safe_limit() { 600 assert(_concurrent_iteration_safe_limit <= top(), 601 "_concurrent_iteration_safe_limit update missed"); 602 return _concurrent_iteration_safe_limit; 603 } 604 // changes the safe limit, all objects from bottom() to the new 605 // limit should be properly initialized 606 void set_concurrent_iteration_safe_limit(HeapWord* new_limit) { 607 assert(new_limit <= top(), "uninitialized objects in the safe range"); 608 _concurrent_iteration_safe_limit = new_limit; 609 } 610 611 612 #if INCLUDE_ALL_GCS 613 // In support of parallel oop_iterate. 614 #define ContigSpace_PAR_OOP_ITERATE_DECL(OopClosureType, nv_suffix) \ 615 void par_oop_iterate(MemRegion mr, OopClosureType* blk); 616 617 ALL_PAR_OOP_ITERATE_CLOSURES(ContigSpace_PAR_OOP_ITERATE_DECL) 618 #undef ContigSpace_PAR_OOP_ITERATE_DECL 619 #endif // INCLUDE_ALL_GCS 620 621 // Compaction support 622 virtual void reset_after_compaction() { 623 assert(compaction_top() >= bottom() && compaction_top() <= end(), "should point inside space"); 624 set_top(compaction_top()); 625 // set new iteration safe limit 626 set_concurrent_iteration_safe_limit(compaction_top()); 627 } 628 629 // Override. 630 DirtyCardToOopClosure* new_dcto_cl(ExtendedOopClosure* cl, 631 CardTableModRefBS::PrecisionStyle precision, 632 HeapWord* boundary = NULL); 633 634 // Apply "blk->do_oop" to the addresses of all reference fields in objects 635 // starting with the _saved_mark_word, which was noted during a generation's 636 // save_marks and is required to denote the head of an object. 637 // Fields in objects allocated by applications of the closure 638 // *are* included in the iteration. 639 // Updates _saved_mark_word to point to just after the last object 640 // iterated over. 641 #define ContigSpace_OOP_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \ 642 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk); 643 644 ALL_SINCE_SAVE_MARKS_CLOSURES(ContigSpace_OOP_SINCE_SAVE_MARKS_DECL) 645 #undef ContigSpace_OOP_SINCE_SAVE_MARKS_DECL 646 647 // Same as object_iterate, but starting from "mark", which is required 648 // to denote the start of an object. Objects allocated by 649 // applications of the closure *are* included in the iteration. 650 virtual void object_iterate_from(WaterMark mark, ObjectClosure* blk); 651 652 // Very inefficient implementation. 653 virtual HeapWord* block_start_const(const void* p) const; 654 size_t block_size(const HeapWord* p) const; 655 // If a block is in the allocated area, it is an object. 656 bool block_is_obj(const HeapWord* p) const { return p < top(); } 657 658 // Addresses for inlined allocation 659 HeapWord** top_addr() { return &_top; } 660 HeapWord** end_addr() { return &_end; } 661 662 // Overrides for more efficient compaction support. 663 void prepare_for_compaction(CompactPoint* cp); 664 665 // PrintHeapAtGC support. 666 virtual void print_on(outputStream* st) const; 667 668 // Checked dynamic downcasts. 669 virtual ContiguousSpace* toContiguousSpace() { 670 return this; 671 } 672 673 // Debugging 674 virtual void verify() const; 675 676 // Used to increase collection frequency. "factor" of 0 means entire 677 // space. 678 void allocate_temporary_filler(int factor); 679 }; 680 681 682 // A dirty card to oop closure that does filtering. 683 // It knows how to filter out objects that are outside of the _boundary. 684 class Filtering_DCTOC : public DirtyCardToOopClosure { 685 protected: 686 // Override. 687 void walk_mem_region(MemRegion mr, 688 HeapWord* bottom, HeapWord* top); 689 690 // Walk the given memory region, from bottom to top, applying 691 // the given oop closure to (possibly) all objects found. The 692 // given oop closure may or may not be the same as the oop 693 // closure with which this closure was created, as it may 694 // be a filtering closure which makes use of the _boundary. 695 // We offer two signatures, so the FilteringClosure static type is 696 // apparent. 697 virtual void walk_mem_region_with_cl(MemRegion mr, 698 HeapWord* bottom, HeapWord* top, 699 ExtendedOopClosure* cl) = 0; 700 virtual void walk_mem_region_with_cl(MemRegion mr, 701 HeapWord* bottom, HeapWord* top, 702 FilteringClosure* cl) = 0; 703 704 public: 705 Filtering_DCTOC(Space* sp, ExtendedOopClosure* cl, 706 CardTableModRefBS::PrecisionStyle precision, 707 HeapWord* boundary) : 708 DirtyCardToOopClosure(sp, cl, precision, boundary) {} 709 }; 710 711 // A dirty card to oop closure for contiguous spaces 712 // (ContiguousSpace and sub-classes). 713 // It is a FilteringClosure, as defined above, and it knows: 714 // 715 // 1. That the actual top of any area in a memory region 716 // contained by the space is bounded by the end of the contiguous 717 // region of the space. 718 // 2. That the space is really made up of objects and not just 719 // blocks. 720 721 class ContiguousSpaceDCTOC : public Filtering_DCTOC { 722 protected: 723 // Overrides. 724 HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj); 725 726 virtual void walk_mem_region_with_cl(MemRegion mr, 727 HeapWord* bottom, HeapWord* top, 728 ExtendedOopClosure* cl); 729 virtual void walk_mem_region_with_cl(MemRegion mr, 730 HeapWord* bottom, HeapWord* top, 731 FilteringClosure* cl); 732 733 public: 734 ContiguousSpaceDCTOC(ContiguousSpace* sp, ExtendedOopClosure* cl, 735 CardTableModRefBS::PrecisionStyle precision, 736 HeapWord* boundary) : 737 Filtering_DCTOC(sp, cl, precision, boundary) 738 {} 739 }; 740 741 // A ContigSpace that Supports an efficient "block_start" operation via 742 // a BlockOffsetArray (whose BlockOffsetSharedArray may be shared with 743 // other spaces.) This is the abstract base class for old generation 744 // (tenured) spaces. 745 746 class OffsetTableContigSpace: public ContiguousSpace { 747 friend class VMStructs; 748 protected: 749 BlockOffsetArrayContigSpace _offsets; 750 Mutex _par_alloc_lock; 751 752 public: 753 // Constructor 754 OffsetTableContigSpace(BlockOffsetSharedArray* sharedOffsetArray, 755 MemRegion mr); 756 757 void set_bottom(HeapWord* value); 758 void set_end(HeapWord* value); 759 760 void clear(bool mangle_space); 761 762 inline HeapWord* block_start_const(const void* p) const; 763 764 // Add offset table update. 765 virtual inline HeapWord* allocate(size_t word_size); 766 inline HeapWord* par_allocate(size_t word_size); 767 768 // MarkSweep support phase3 769 virtual HeapWord* initialize_threshold(); 770 virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* end); 771 772 virtual void print_on(outputStream* st) const; 773 774 // Debugging 775 void verify() const; 776 }; 777 778 779 // Class TenuredSpace is used by TenuredGeneration 780 781 class TenuredSpace: public OffsetTableContigSpace { 782 friend class VMStructs; 783 protected: 784 // Mark sweep support 785 size_t allowed_dead_ratio() const; 786 public: 787 // Constructor 788 TenuredSpace(BlockOffsetSharedArray* sharedOffsetArray, 789 MemRegion mr) : 790 OffsetTableContigSpace(sharedOffsetArray, mr) {} 791 }; 792 #endif // SHARE_VM_MEMORY_SPACE_HPP