1 /* 2 * Copyright (c) 1997, 2012, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #ifndef SHARE_VM_MEMORY_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 "runtime/prefetch.hpp" 37 #include "utilities/macros.hpp" 38 #include "utilities/workgroup.hpp" 39 #ifdef TARGET_OS_FAMILY_linux 40 # include "os_linux.inline.hpp" 41 #endif 42 #ifdef TARGET_OS_FAMILY_solaris 43 # include "os_solaris.inline.hpp" 44 #endif 45 #ifdef TARGET_OS_FAMILY_windows 46 # include "os_windows.inline.hpp" 47 #endif 48 #ifdef TARGET_OS_FAMILY_bsd 49 # include "os_bsd.inline.hpp" 50 #endif 51 52 // A space is an abstraction for the "storage units" backing 53 // up the generation abstraction. It includes specific 54 // implementations for keeping track of free and used space, 55 // for iterating over objects and free blocks, etc. 56 57 // Here's the Space hierarchy: 58 // 59 // - Space -- an abstract base class describing a heap area 60 // - CompactibleSpace -- a space supporting compaction 61 // - CompactibleFreeListSpace -- (used for CMS generation) 62 // - ContiguousSpace -- a compactible space in which all free space 63 // is contiguous 64 // - EdenSpace -- contiguous space used as nursery 65 // - ConcEdenSpace -- contiguous space with a 'soft end safe' allocation 66 // - OffsetTableContigSpace -- contiguous space with a block offset array 67 // that allows "fast" block_start calls 68 // - TenuredSpace -- (used for TenuredGeneration) 69 70 // Forward decls. 71 class Space; 72 class BlockOffsetArray; 73 class BlockOffsetArrayContigSpace; 74 class Generation; 75 class CompactibleSpace; 76 class BlockOffsetTable; 77 class GenRemSet; 78 class CardTableRS; 79 class DirtyCardToOopClosure; 80 81 // An oop closure that is circumscribed by a filtering memory region. 82 class SpaceMemRegionOopsIterClosure: public ExtendedOopClosure { 83 private: 84 ExtendedOopClosure* _cl; 85 MemRegion _mr; 86 protected: 87 template <class T> void do_oop_work(T* p) { 88 if (_mr.contains(p)) { 89 _cl->do_oop(p); 90 } 91 } 92 public: 93 SpaceMemRegionOopsIterClosure(ExtendedOopClosure* cl, MemRegion mr): 94 _cl(cl), _mr(mr) {} 95 virtual void do_oop(oop* p); 96 virtual void do_oop(narrowOop* p); 97 virtual bool do_metadata() { 98 // _cl is of type ExtendedOopClosure instead of OopClosure, so that we can check this. 99 assert(!_cl->do_metadata(), "I've checked all call paths, this shouldn't happen."); 100 return false; 101 } 102 virtual void do_klass(Klass* k) { ShouldNotReachHere(); } 103 virtual void do_class_loader_data(ClassLoaderData* cld) { ShouldNotReachHere(); } 104 }; 105 106 // A Space describes a heap area. Class Space is an abstract 107 // base class. 108 // 109 // Space supports allocation, size computation and GC support is provided. 110 // 111 // Invariant: bottom() and end() are on page_size boundaries and 112 // bottom() <= top() <= end() 113 // top() is inclusive and end() is exclusive. 114 115 class Space: public CHeapObj<mtGC> { 116 friend class VMStructs; 117 protected: 118 HeapWord* _bottom; 119 HeapWord* _end; 120 121 // Used in support of save_marks() 122 HeapWord* _saved_mark_word; 123 124 MemRegionClosure* _preconsumptionDirtyCardClosure; 125 126 // A sequential tasks done structure. This supports 127 // parallel GC, where we have threads dynamically 128 // claiming sub-tasks from a larger parallel task. 129 SequentialSubTasksDone _par_seq_tasks; 130 131 Space(): 132 _bottom(NULL), _end(NULL), _preconsumptionDirtyCardClosure(NULL) { } 133 134 public: 135 // Accessors 136 HeapWord* bottom() const { return _bottom; } 137 HeapWord* end() const { return _end; } 138 virtual void set_bottom(HeapWord* value) { _bottom = value; } 139 virtual void set_end(HeapWord* value) { _end = value; } 140 141 virtual HeapWord* saved_mark_word() const { return _saved_mark_word; } 142 143 void set_saved_mark_word(HeapWord* p) { _saved_mark_word = p; } 144 145 MemRegionClosure* preconsumptionDirtyCardClosure() const { 146 return _preconsumptionDirtyCardClosure; 147 } 148 void setPreconsumptionDirtyCardClosure(MemRegionClosure* cl) { 149 _preconsumptionDirtyCardClosure = cl; 150 } 151 152 // Returns a subregion of the space containing all the objects in 153 // the space. 154 virtual MemRegion used_region() const { return MemRegion(bottom(), end()); } 155 156 // Returns a region that is guaranteed to contain (at least) all objects 157 // allocated at the time of the last call to "save_marks". If the space 158 // initializes its DirtyCardToOopClosure's specifying the "contig" option 159 // (that is, if the space is contiguous), then this region must contain only 160 // such objects: the memregion will be from the bottom of the region to the 161 // saved mark. Otherwise, the "obj_allocated_since_save_marks" method of 162 // the space must distinguish between objects in the region allocated before 163 // and after the call to save marks. 164 virtual MemRegion used_region_at_save_marks() const { 165 return MemRegion(bottom(), saved_mark_word()); 166 } 167 168 // Initialization. 169 // "initialize" should be called once on a space, before it is used for 170 // any purpose. The "mr" arguments gives the bounds of the space, and 171 // the "clear_space" argument should be true unless the memory in "mr" is 172 // known to be zeroed. 173 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space); 174 175 // The "clear" method must be called on a region that may have 176 // had allocation performed in it, but is now to be considered empty. 177 virtual void clear(bool mangle_space); 178 179 // For detecting GC bugs. Should only be called at GC boundaries, since 180 // some unused space may be used as scratch space during GC's. 181 // Default implementation does nothing. We also call this when expanding 182 // a space to satisfy an allocation request. See bug #4668531 183 virtual void mangle_unused_area() {} 184 virtual void mangle_unused_area_complete() {} 185 virtual void mangle_region(MemRegion mr) {} 186 187 // Testers 188 bool is_empty() const { return used() == 0; } 189 bool not_empty() const { return used() > 0; } 190 191 // Returns true iff the given the space contains the 192 // given address as part of an allocated object. For 193 // certain kinds of spaces, this might be a potentially 194 // expensive operation. To prevent performance problems 195 // on account of its inadvertent use in product jvm's, 196 // we restrict its use to assertion checks only. 197 virtual bool is_in(const void* p) const = 0; 198 199 // Returns true iff the given reserved memory of the space contains the 200 // given address. 201 bool is_in_reserved(const void* p) const { return _bottom <= p && p < _end; } 202 203 // Returns true iff the given block is not allocated. 204 virtual bool is_free_block(const HeapWord* p) const = 0; 205 206 // Test whether p is double-aligned 207 static bool is_aligned(void* p) { 208 return ((intptr_t)p & (sizeof(double)-1)) == 0; 209 } 210 211 // Size computations. Sizes are in bytes. 212 size_t capacity() const { return byte_size(bottom(), end()); } 213 virtual size_t used() const = 0; 214 virtual size_t free() const = 0; 215 216 // Iterate over all the ref-containing fields of all objects in the 217 // space, calling "cl.do_oop" on each. Fields in objects allocated by 218 // applications of the closure are not included in the iteration. 219 virtual void oop_iterate(ExtendedOopClosure* cl); 220 221 // Same as above, restricted to the intersection of a memory region and 222 // the space. Fields in objects allocated by applications of the closure 223 // are not included in the iteration. 224 virtual void oop_iterate(MemRegion mr, ExtendedOopClosure* cl) = 0; 225 226 // Iterate over all objects in the space, calling "cl.do_object" on 227 // each. Objects allocated by applications of the closure are not 228 // included in the iteration. 229 virtual void object_iterate(ObjectClosure* blk) = 0; 230 // Similar to object_iterate() except only iterates over 231 // objects whose internal references point to objects in the space. 232 virtual void safe_object_iterate(ObjectClosure* blk) = 0; 233 234 // Iterate over all objects that intersect with mr, calling "cl->do_object" 235 // on each. There is an exception to this: if this closure has already 236 // been invoked on an object, it may skip such objects in some cases. This is 237 // Most likely to happen in an "upwards" (ascending address) iteration of 238 // MemRegions. 239 virtual void object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl); 240 241 // Iterate over as many initialized objects in the space as possible, 242 // calling "cl.do_object_careful" on each. Return NULL if all objects 243 // in the space (at the start of the iteration) were iterated over. 244 // Return an address indicating the extent of the iteration in the 245 // event that the iteration had to return because of finding an 246 // uninitialized object in the space, or if the closure "cl" 247 // signaled early termination. 248 virtual HeapWord* object_iterate_careful(ObjectClosureCareful* cl); 249 virtual HeapWord* object_iterate_careful_m(MemRegion mr, 250 ObjectClosureCareful* cl); 251 252 // Create and return a new dirty card to oop closure. Can be 253 // overridden to return the appropriate type of closure 254 // depending on the type of space in which the closure will 255 // operate. ResourceArea allocated. 256 virtual DirtyCardToOopClosure* new_dcto_cl(ExtendedOopClosure* cl, 257 CardTableModRefBS::PrecisionStyle precision, 258 HeapWord* boundary = NULL); 259 260 // If "p" is in the space, returns the address of the start of the 261 // "block" that contains "p". We say "block" instead of "object" since 262 // some heaps may not pack objects densely; a chunk may either be an 263 // object or a non-object. If "p" is not in the space, return NULL. 264 virtual HeapWord* block_start_const(const void* p) const = 0; 265 266 // The non-const version may have benevolent side effects on the data 267 // structure supporting these calls, possibly speeding up future calls. 268 // The default implementation, however, is simply to call the const 269 // version. 270 inline virtual HeapWord* block_start(const void* p); 271 272 // Requires "addr" to be the start of a chunk, and returns its size. 273 // "addr + size" is required to be the start of a new chunk, or the end 274 // of the active area of the heap. 275 virtual size_t block_size(const HeapWord* addr) const = 0; 276 277 // Requires "addr" to be the start of a block, and returns "TRUE" iff 278 // the block is an object. 279 virtual bool block_is_obj(const HeapWord* addr) const = 0; 280 281 // Requires "addr" to be the start of a block, and returns "TRUE" iff 282 // the block is an object and the object is alive. 283 virtual bool obj_is_alive(const HeapWord* addr) const; 284 285 // Allocation (return NULL if full). Assumes the caller has established 286 // mutually exclusive access to the space. 287 virtual HeapWord* allocate(size_t word_size) = 0; 288 289 // Allocation (return NULL if full). Enforces mutual exclusion internally. 290 virtual HeapWord* par_allocate(size_t word_size) = 0; 291 292 // Returns true if this object has been allocated since a 293 // generation's "save_marks" call. 294 virtual bool obj_allocated_since_save_marks(const oop obj) const = 0; 295 296 // Mark-sweep-compact support: all spaces can update pointers to objects 297 // moving as a part of compaction. 298 virtual void adjust_pointers(); 299 300 // PrintHeapAtGC support 301 virtual void print() const; 302 virtual void print_on(outputStream* st) const; 303 virtual void print_short() const; 304 virtual void print_short_on(outputStream* st) const; 305 306 307 // Accessor for parallel sequential tasks. 308 SequentialSubTasksDone* par_seq_tasks() { return &_par_seq_tasks; } 309 310 // IF "this" is a ContiguousSpace, return it, else return NULL. 311 virtual ContiguousSpace* toContiguousSpace() { 312 return NULL; 313 } 314 315 // Debugging 316 virtual void verify() const = 0; 317 }; 318 319 // A MemRegionClosure (ResourceObj) whose "do_MemRegion" function applies an 320 // OopClosure to (the addresses of) all the ref-containing fields that could 321 // be modified by virtue of the given MemRegion being dirty. (Note that 322 // because of the imprecise nature of the write barrier, this may iterate 323 // over oops beyond the region.) 324 // This base type for dirty card to oop closures handles memory regions 325 // in non-contiguous spaces with no boundaries, and should be sub-classed 326 // to support other space types. See ContiguousDCTOC for a sub-class 327 // that works with ContiguousSpaces. 328 329 class DirtyCardToOopClosure: public MemRegionClosureRO { 330 protected: 331 ExtendedOopClosure* _cl; 332 Space* _sp; 333 CardTableModRefBS::PrecisionStyle _precision; 334 HeapWord* _boundary; // If non-NULL, process only non-NULL oops 335 // pointing below boundary. 336 HeapWord* _min_done; // ObjHeadPreciseArray precision requires 337 // a downwards traversal; this is the 338 // lowest location already done (or, 339 // alternatively, the lowest address that 340 // shouldn't be done again. NULL means infinity.) 341 NOT_PRODUCT(HeapWord* _last_bottom;) 342 NOT_PRODUCT(HeapWord* _last_explicit_min_done;) 343 344 // Get the actual top of the area on which the closure will 345 // operate, given where the top is assumed to be (the end of the 346 // memory region passed to do_MemRegion) and where the object 347 // at the top is assumed to start. For example, an object may 348 // start at the top but actually extend past the assumed top, 349 // in which case the top becomes the end of the object. 350 virtual HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj); 351 352 // Walk the given memory region from bottom to (actual) top 353 // looking for objects and applying the oop closure (_cl) to 354 // them. The base implementation of this treats the area as 355 // blocks, where a block may or may not be an object. Sub- 356 // classes should override this to provide more accurate 357 // or possibly more efficient walking. 358 virtual void walk_mem_region(MemRegion mr, HeapWord* bottom, HeapWord* top); 359 360 public: 361 DirtyCardToOopClosure(Space* sp, ExtendedOopClosure* cl, 362 CardTableModRefBS::PrecisionStyle precision, 363 HeapWord* boundary) : 364 _sp(sp), _cl(cl), _precision(precision), _boundary(boundary), 365 _min_done(NULL) { 366 NOT_PRODUCT(_last_bottom = NULL); 367 NOT_PRODUCT(_last_explicit_min_done = NULL); 368 } 369 370 void do_MemRegion(MemRegion mr); 371 372 void set_min_done(HeapWord* min_done) { 373 _min_done = min_done; 374 NOT_PRODUCT(_last_explicit_min_done = _min_done); 375 } 376 #ifndef PRODUCT 377 void set_last_bottom(HeapWord* last_bottom) { 378 _last_bottom = last_bottom; 379 } 380 #endif 381 }; 382 383 // A structure to represent a point at which objects are being copied 384 // during compaction. 385 class CompactPoint : public StackObj { 386 public: 387 Generation* gen; 388 CompactibleSpace* space; 389 HeapWord* threshold; 390 CompactPoint(Generation* _gen, CompactibleSpace* _space, 391 HeapWord* _threshold) : 392 gen(_gen), space(_space), threshold(_threshold) {} 393 }; 394 395 396 // A space that supports compaction operations. This is usually, but not 397 // necessarily, a space that is normally contiguous. But, for example, a 398 // free-list-based space whose normal collection is a mark-sweep without 399 // compaction could still support compaction in full GC's. 400 401 class CompactibleSpace: public Space { 402 friend class VMStructs; 403 friend class CompactibleFreeListSpace; 404 private: 405 HeapWord* _compaction_top; 406 CompactibleSpace* _next_compaction_space; 407 408 public: 409 CompactibleSpace() : 410 _compaction_top(NULL), _next_compaction_space(NULL) {} 411 412 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space); 413 virtual void clear(bool mangle_space); 414 415 // Used temporarily during a compaction phase to hold the value 416 // top should have when compaction is complete. 417 HeapWord* compaction_top() const { return _compaction_top; } 418 419 void set_compaction_top(HeapWord* value) { 420 assert(value == NULL || (value >= bottom() && value <= end()), 421 "should point inside space"); 422 _compaction_top = value; 423 } 424 425 // Perform operations on the space needed after a compaction 426 // has been performed. 427 virtual void reset_after_compaction() {} 428 429 // Returns the next space (in the current generation) to be compacted in 430 // the global compaction order. Also is used to select the next 431 // space into which to compact. 432 433 virtual CompactibleSpace* next_compaction_space() const { 434 return _next_compaction_space; 435 } 436 437 void set_next_compaction_space(CompactibleSpace* csp) { 438 _next_compaction_space = csp; 439 } 440 441 // MarkSweep support phase2 442 443 // Start the process of compaction of the current space: compute 444 // post-compaction addresses, and insert forwarding pointers. The fields 445 // "cp->gen" and "cp->compaction_space" are the generation and space into 446 // which we are currently compacting. This call updates "cp" as necessary, 447 // and leaves the "compaction_top" of the final value of 448 // "cp->compaction_space" up-to-date. Offset tables may be updated in 449 // this phase as if the final copy had occurred; if so, "cp->threshold" 450 // indicates when the next such action should be taken. 451 virtual void prepare_for_compaction(CompactPoint* cp); 452 // MarkSweep support phase3 453 virtual void adjust_pointers(); 454 // MarkSweep support phase4 455 virtual void compact(); 456 457 // The maximum percentage of objects that can be dead in the compacted 458 // live part of a compacted space ("deadwood" support.) 459 virtual size_t allowed_dead_ratio() const { return 0; }; 460 461 // Some contiguous spaces may maintain some data structures that should 462 // be updated whenever an allocation crosses a boundary. This function 463 // returns the first such boundary. 464 // (The default implementation returns the end of the space, so the 465 // boundary is never crossed.) 466 virtual HeapWord* initialize_threshold() { return end(); } 467 468 // "q" is an object of the given "size" that should be forwarded; 469 // "cp" names the generation ("gen") and containing "this" (which must 470 // also equal "cp->space"). "compact_top" is where in "this" the 471 // next object should be forwarded to. If there is room in "this" for 472 // the object, insert an appropriate forwarding pointer in "q". 473 // If not, go to the next compaction space (there must 474 // be one, since compaction must succeed -- we go to the first space of 475 // the previous generation if necessary, updating "cp"), reset compact_top 476 // and then forward. In either case, returns the new value of "compact_top". 477 // If the forwarding crosses "cp->threshold", invokes the "cross_threshold" 478 // function of the then-current compaction space, and updates "cp->threshold 479 // accordingly". 480 virtual HeapWord* forward(oop q, size_t size, CompactPoint* cp, 481 HeapWord* compact_top); 482 483 // Return a size with adjustments as required of the space. 484 virtual size_t adjust_object_size_v(size_t size) const { return size; } 485 486 protected: 487 // Used during compaction. 488 HeapWord* _first_dead; 489 HeapWord* _end_of_live; 490 491 // Minimum size of a free block. 492 virtual size_t minimum_free_block_size() const = 0; 493 494 // This the function is invoked when an allocation of an object covering 495 // "start" to "end occurs crosses the threshold; returns the next 496 // threshold. (The default implementation does nothing.) 497 virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* the_end) { 498 return end(); 499 } 500 501 // Requires "allowed_deadspace_words > 0", that "q" is the start of a 502 // free block of the given "word_len", and that "q", were it an object, 503 // would not move if forwarded. If the size allows, fill the free 504 // block with an object, to prevent excessive compaction. Returns "true" 505 // iff the free region was made deadspace, and modifies 506 // "allowed_deadspace_words" to reflect the number of available deadspace 507 // words remaining after this operation. 508 bool insert_deadspace(size_t& allowed_deadspace_words, HeapWord* q, 509 size_t word_len); 510 }; 511 512 #define SCAN_AND_FORWARD(cp,scan_limit,block_is_obj,block_size) { \ 513 /* Compute the new addresses for the live objects and store it in the mark \ 514 * Used by universe::mark_sweep_phase2() \ 515 */ \ 516 HeapWord* compact_top; /* This is where we are currently compacting to. */ \ 517 \ 518 /* We're sure to be here before any objects are compacted into this \ 519 * space, so this is a good time to initialize this: \ 520 */ \ 521 set_compaction_top(bottom()); \ 522 \ 523 if (cp->space == NULL) { \ 524 assert(cp->gen != NULL, "need a generation"); \ 525 assert(cp->threshold == NULL, "just checking"); \ 526 assert(cp->gen->first_compaction_space() == this, "just checking"); \ 527 cp->space = cp->gen->first_compaction_space(); \ 528 compact_top = cp->space->bottom(); \ 529 cp->space->set_compaction_top(compact_top); \ 530 cp->threshold = cp->space->initialize_threshold(); \ 531 } else { \ 532 compact_top = cp->space->compaction_top(); \ 533 } \ 534 \ 535 /* We allow some amount of garbage towards the bottom of the space, so \ 536 * we don't start compacting before there is a significant gain to be made.\ 537 * Occasionally, we want to ensure a full compaction, which is determined \ 538 * by the MarkSweepAlwaysCompactCount parameter. \ 539 */ \ 540 uint invocations = MarkSweep::total_invocations(); \ 541 bool skip_dead = ((invocations % MarkSweepAlwaysCompactCount) != 0); \ 542 \ 543 size_t allowed_deadspace = 0; \ 544 if (skip_dead) { \ 545 const size_t ratio = allowed_dead_ratio(); \ 546 allowed_deadspace = (capacity() * ratio / 100) / HeapWordSize; \ 547 } \ 548 \ 549 HeapWord* q = bottom(); \ 550 HeapWord* t = scan_limit(); \ 551 \ 552 HeapWord* end_of_live= q; /* One byte beyond the last byte of the last \ 553 live object. */ \ 554 HeapWord* first_dead = end();/* The first dead object. */ \ 555 LiveRange* liveRange = NULL; /* The current live range, recorded in the \ 556 first header of preceding free area. */ \ 557 _first_dead = first_dead; \ 558 \ 559 const intx interval = PrefetchScanIntervalInBytes; \ 560 \ 561 while (q < t) { \ 562 assert(!block_is_obj(q) || \ 563 oop(q)->mark()->is_marked() || oop(q)->mark()->is_unlocked() || \ 564 oop(q)->mark()->has_bias_pattern(), \ 565 "these are the only valid states during a mark sweep"); \ 566 if (block_is_obj(q) && oop(q)->is_gc_marked()) { \ 567 /* prefetch beyond q */ \ 568 Prefetch::write(q, interval); \ 569 size_t size = block_size(q); \ 570 compact_top = cp->space->forward(oop(q), size, cp, compact_top); \ 571 q += size; \ 572 end_of_live = q; \ 573 } else { \ 574 /* run over all the contiguous dead objects */ \ 575 HeapWord* end = q; \ 576 do { \ 577 /* prefetch beyond end */ \ 578 Prefetch::write(end, interval); \ 579 end += block_size(end); \ 580 } while (end < t && (!block_is_obj(end) || !oop(end)->is_gc_marked()));\ 581 \ 582 /* see if we might want to pretend this object is alive so that \ 583 * we don't have to compact quite as often. \ 584 */ \ 585 if (allowed_deadspace > 0 && q == compact_top) { \ 586 size_t sz = pointer_delta(end, q); \ 587 if (insert_deadspace(allowed_deadspace, q, sz)) { \ 588 compact_top = cp->space->forward(oop(q), sz, cp, compact_top); \ 589 q = end; \ 590 end_of_live = end; \ 591 continue; \ 592 } \ 593 } \ 594 \ 595 /* otherwise, it really is a free region. */ \ 596 \ 597 /* for the previous LiveRange, record the end of the live objects. */ \ 598 if (liveRange) { \ 599 liveRange->set_end(q); \ 600 } \ 601 \ 602 /* record the current LiveRange object. \ 603 * liveRange->start() is overlaid on the mark word. \ 604 */ \ 605 liveRange = (LiveRange*)q; \ 606 liveRange->set_start(end); \ 607 liveRange->set_end(end); \ 608 \ 609 /* see if this is the first dead region. */ \ 610 if (q < first_dead) { \ 611 first_dead = q; \ 612 } \ 613 \ 614 /* move on to the next object */ \ 615 q = end; \ 616 } \ 617 } \ 618 \ 619 assert(q == t, "just checking"); \ 620 if (liveRange != NULL) { \ 621 liveRange->set_end(q); \ 622 } \ 623 _end_of_live = end_of_live; \ 624 if (end_of_live < first_dead) { \ 625 first_dead = end_of_live; \ 626 } \ 627 _first_dead = first_dead; \ 628 \ 629 /* save the compaction_top of the compaction space. */ \ 630 cp->space->set_compaction_top(compact_top); \ 631 } 632 633 #define SCAN_AND_ADJUST_POINTERS(adjust_obj_size) { \ 634 /* adjust all the interior pointers to point at the new locations of objects \ 635 * Used by MarkSweep::mark_sweep_phase3() */ \ 636 \ 637 HeapWord* q = bottom(); \ 638 HeapWord* t = _end_of_live; /* Established by "prepare_for_compaction". */ \ 639 \ 640 assert(_first_dead <= _end_of_live, "Stands to reason, no?"); \ 641 \ 642 if (q < t && _first_dead > q && \ 643 !oop(q)->is_gc_marked()) { \ 644 /* we have a chunk of the space which hasn't moved and we've \ 645 * reinitialized the mark word during the previous pass, so we can't \ 646 * use is_gc_marked for the traversal. */ \ 647 HeapWord* end = _first_dead; \ 648 \ 649 while (q < end) { \ 650 /* I originally tried to conjoin "block_start(q) == q" to the \ 651 * assertion below, but that doesn't work, because you can't \ 652 * accurately traverse previous objects to get to the current one \ 653 * after their pointers have been \ 654 * updated, until the actual compaction is done. dld, 4/00 */ \ 655 assert(block_is_obj(q), \ 656 "should be at block boundaries, and should be looking at objs"); \ 657 \ 658 /* point all the oops to the new location */ \ 659 size_t size = oop(q)->adjust_pointers(); \ 660 size = adjust_obj_size(size); \ 661 \ 662 q += size; \ 663 } \ 664 \ 665 if (_first_dead == t) { \ 666 q = t; \ 667 } else { \ 668 /* $$$ This is funky. Using this to read the previously written \ 669 * LiveRange. See also use below. */ \ 670 q = (HeapWord*)oop(_first_dead)->mark()->decode_pointer(); \ 671 } \ 672 } \ 673 \ 674 const intx interval = PrefetchScanIntervalInBytes; \ 675 \ 676 debug_only(HeapWord* prev_q = NULL); \ 677 while (q < t) { \ 678 /* prefetch beyond q */ \ 679 Prefetch::write(q, interval); \ 680 if (oop(q)->is_gc_marked()) { \ 681 /* q is alive */ \ 682 /* point all the oops to the new location */ \ 683 size_t size = oop(q)->adjust_pointers(); \ 684 size = adjust_obj_size(size); \ 685 debug_only(prev_q = q); \ 686 q += size; \ 687 } else { \ 688 /* q is not a live object, so its mark should point at the next \ 689 * live object */ \ 690 debug_only(prev_q = q); \ 691 q = (HeapWord*) oop(q)->mark()->decode_pointer(); \ 692 assert(q > prev_q, "we should be moving forward through memory"); \ 693 } \ 694 } \ 695 \ 696 assert(q == t, "just checking"); \ 697 } 698 699 #define SCAN_AND_COMPACT(obj_size) { \ 700 /* Copy all live objects to their new location \ 701 * Used by MarkSweep::mark_sweep_phase4() */ \ 702 \ 703 HeapWord* q = bottom(); \ 704 HeapWord* const t = _end_of_live; \ 705 debug_only(HeapWord* prev_q = NULL); \ 706 \ 707 if (q < t && _first_dead > q && \ 708 !oop(q)->is_gc_marked()) { \ 709 debug_only( \ 710 /* we have a chunk of the space which hasn't moved and we've reinitialized \ 711 * the mark word during the previous pass, so we can't use is_gc_marked for \ 712 * the traversal. */ \ 713 HeapWord* const end = _first_dead; \ 714 \ 715 while (q < end) { \ 716 size_t size = obj_size(q); \ 717 assert(!oop(q)->is_gc_marked(), \ 718 "should be unmarked (special dense prefix handling)"); \ 719 debug_only(prev_q = q); \ 720 q += size; \ 721 } \ 722 ) /* debug_only */ \ 723 \ 724 if (_first_dead == t) { \ 725 q = t; \ 726 } else { \ 727 /* $$$ Funky */ \ 728 q = (HeapWord*) oop(_first_dead)->mark()->decode_pointer(); \ 729 } \ 730 } \ 731 \ 732 const intx scan_interval = PrefetchScanIntervalInBytes; \ 733 const intx copy_interval = PrefetchCopyIntervalInBytes; \ 734 while (q < t) { \ 735 if (!oop(q)->is_gc_marked()) { \ 736 /* mark is pointer to next marked oop */ \ 737 debug_only(prev_q = q); \ 738 q = (HeapWord*) oop(q)->mark()->decode_pointer(); \ 739 assert(q > prev_q, "we should be moving forward through memory"); \ 740 } else { \ 741 /* prefetch beyond q */ \ 742 Prefetch::read(q, scan_interval); \ 743 \ 744 /* size and destination */ \ 745 size_t size = obj_size(q); \ 746 HeapWord* compaction_top = (HeapWord*)oop(q)->forwardee(); \ 747 \ 748 /* prefetch beyond compaction_top */ \ 749 Prefetch::write(compaction_top, copy_interval); \ 750 \ 751 /* copy object and reinit its mark */ \ 752 assert(q != compaction_top, "everything in this pass should be moving"); \ 753 Copy::aligned_conjoint_words(q, compaction_top, size); \ 754 oop(compaction_top)->init_mark(); \ 755 assert(oop(compaction_top)->klass() != NULL, "should have a class"); \ 756 \ 757 debug_only(prev_q = q); \ 758 q += size; \ 759 } \ 760 } \ 761 \ 762 /* Let's remember if we were empty before we did the compaction. */ \ 763 bool was_empty = used_region().is_empty(); \ 764 /* Reset space after compaction is complete */ \ 765 reset_after_compaction(); \ 766 /* We do this clear, below, since it has overloaded meanings for some */ \ 767 /* space subtypes. For example, OffsetTableContigSpace's that were */ \ 768 /* compacted into will have had their offset table thresholds updated */ \ 769 /* continuously, but those that weren't need to have their thresholds */ \ 770 /* re-initialized. Also mangles unused area for debugging. */ \ 771 if (used_region().is_empty()) { \ 772 if (!was_empty) clear(SpaceDecorator::Mangle); \ 773 } else { \ 774 if (ZapUnusedHeapArea) mangle_unused_area(); \ 775 } \ 776 } 777 778 class GenSpaceMangler; 779 780 // A space in which the free area is contiguous. It therefore supports 781 // faster allocation, and compaction. 782 class ContiguousSpace: public CompactibleSpace { 783 friend class OneContigSpaceCardGeneration; 784 friend class VMStructs; 785 protected: 786 HeapWord* _top; 787 HeapWord* _concurrent_iteration_safe_limit; 788 // A helper for mangling the unused area of the space in debug builds. 789 GenSpaceMangler* _mangler; 790 791 GenSpaceMangler* mangler() { return _mangler; } 792 793 // Allocation helpers (return NULL if full). 794 inline HeapWord* allocate_impl(size_t word_size, HeapWord* end_value); 795 inline HeapWord* par_allocate_impl(size_t word_size, HeapWord* end_value); 796 797 public: 798 ContiguousSpace(); 799 ~ContiguousSpace(); 800 801 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space); 802 virtual void clear(bool mangle_space); 803 804 // Accessors 805 HeapWord* top() const { return _top; } 806 void set_top(HeapWord* value) { _top = value; } 807 808 virtual void set_saved_mark() { _saved_mark_word = top(); } 809 void reset_saved_mark() { _saved_mark_word = bottom(); } 810 811 WaterMark bottom_mark() { return WaterMark(this, bottom()); } 812 WaterMark top_mark() { return WaterMark(this, top()); } 813 WaterMark saved_mark() { return WaterMark(this, saved_mark_word()); } 814 bool saved_mark_at_top() const { return saved_mark_word() == top(); } 815 816 // In debug mode mangle (write it with a particular bit 817 // pattern) the unused part of a space. 818 819 // Used to save the an address in a space for later use during mangling. 820 void set_top_for_allocations(HeapWord* v) PRODUCT_RETURN; 821 // Used to save the space's current top for later use during mangling. 822 void set_top_for_allocations() PRODUCT_RETURN; 823 824 // Mangle regions in the space from the current top up to the 825 // previously mangled part of the space. 826 void mangle_unused_area() PRODUCT_RETURN; 827 // Mangle [top, end) 828 void mangle_unused_area_complete() PRODUCT_RETURN; 829 // Mangle the given MemRegion. 830 void mangle_region(MemRegion mr) PRODUCT_RETURN; 831 832 // Do some sparse checking on the area that should have been mangled. 833 void check_mangled_unused_area(HeapWord* limit) PRODUCT_RETURN; 834 // Check the complete area that should have been mangled. 835 // This code may be NULL depending on the macro DEBUG_MANGLING. 836 void check_mangled_unused_area_complete() PRODUCT_RETURN; 837 838 // Size computations: sizes in bytes. 839 size_t capacity() const { return byte_size(bottom(), end()); } 840 size_t used() const { return byte_size(bottom(), top()); } 841 size_t free() const { return byte_size(top(), end()); } 842 843 // Override from space. 844 bool is_in(const void* p) const; 845 846 virtual bool is_free_block(const HeapWord* p) const; 847 848 // In a contiguous space we have a more obvious bound on what parts 849 // contain objects. 850 MemRegion used_region() const { return MemRegion(bottom(), top()); } 851 852 MemRegion used_region_at_save_marks() const { 853 return MemRegion(bottom(), saved_mark_word()); 854 } 855 856 // Allocation (return NULL if full) 857 virtual HeapWord* allocate(size_t word_size); 858 virtual HeapWord* par_allocate(size_t word_size); 859 860 virtual bool obj_allocated_since_save_marks(const oop obj) const { 861 return (HeapWord*)obj >= saved_mark_word(); 862 } 863 864 // Iteration 865 void oop_iterate(ExtendedOopClosure* cl); 866 void oop_iterate(MemRegion mr, ExtendedOopClosure* cl); 867 void object_iterate(ObjectClosure* blk); 868 // For contiguous spaces this method will iterate safely over objects 869 // in the space (i.e., between bottom and top) when at a safepoint. 870 void safe_object_iterate(ObjectClosure* blk); 871 void object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl); 872 // iterates on objects up to the safe limit 873 HeapWord* object_iterate_careful(ObjectClosureCareful* cl); 874 HeapWord* concurrent_iteration_safe_limit() { 875 assert(_concurrent_iteration_safe_limit <= top(), 876 "_concurrent_iteration_safe_limit update missed"); 877 return _concurrent_iteration_safe_limit; 878 } 879 // changes the safe limit, all objects from bottom() to the new 880 // limit should be properly initialized 881 void set_concurrent_iteration_safe_limit(HeapWord* new_limit) { 882 assert(new_limit <= top(), "uninitialized objects in the safe range"); 883 _concurrent_iteration_safe_limit = new_limit; 884 } 885 886 887 #if INCLUDE_ALL_GCS 888 // In support of parallel oop_iterate. 889 #define ContigSpace_PAR_OOP_ITERATE_DECL(OopClosureType, nv_suffix) \ 890 void par_oop_iterate(MemRegion mr, OopClosureType* blk); 891 892 ALL_PAR_OOP_ITERATE_CLOSURES(ContigSpace_PAR_OOP_ITERATE_DECL) 893 #undef ContigSpace_PAR_OOP_ITERATE_DECL 894 #endif // INCLUDE_ALL_GCS 895 896 // Compaction support 897 virtual void reset_after_compaction() { 898 assert(compaction_top() >= bottom() && compaction_top() <= end(), "should point inside space"); 899 set_top(compaction_top()); 900 // set new iteration safe limit 901 set_concurrent_iteration_safe_limit(compaction_top()); 902 } 903 virtual size_t minimum_free_block_size() const { return 0; } 904 905 // Override. 906 DirtyCardToOopClosure* new_dcto_cl(ExtendedOopClosure* cl, 907 CardTableModRefBS::PrecisionStyle precision, 908 HeapWord* boundary = NULL); 909 910 // Apply "blk->do_oop" to the addresses of all reference fields in objects 911 // starting with the _saved_mark_word, which was noted during a generation's 912 // save_marks and is required to denote the head of an object. 913 // Fields in objects allocated by applications of the closure 914 // *are* included in the iteration. 915 // Updates _saved_mark_word to point to just after the last object 916 // iterated over. 917 #define ContigSpace_OOP_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \ 918 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk); 919 920 ALL_SINCE_SAVE_MARKS_CLOSURES(ContigSpace_OOP_SINCE_SAVE_MARKS_DECL) 921 #undef ContigSpace_OOP_SINCE_SAVE_MARKS_DECL 922 923 // Same as object_iterate, but starting from "mark", which is required 924 // to denote the start of an object. Objects allocated by 925 // applications of the closure *are* included in the iteration. 926 virtual void object_iterate_from(WaterMark mark, ObjectClosure* blk); 927 928 // Very inefficient implementation. 929 virtual HeapWord* block_start_const(const void* p) const; 930 size_t block_size(const HeapWord* p) const; 931 // If a block is in the allocated area, it is an object. 932 bool block_is_obj(const HeapWord* p) const { return p < top(); } 933 934 // Addresses for inlined allocation 935 HeapWord** top_addr() { return &_top; } 936 HeapWord** end_addr() { return &_end; } 937 938 // Overrides for more efficient compaction support. 939 void prepare_for_compaction(CompactPoint* cp); 940 941 // PrintHeapAtGC support. 942 virtual void print_on(outputStream* st) const; 943 944 // Checked dynamic downcasts. 945 virtual ContiguousSpace* toContiguousSpace() { 946 return this; 947 } 948 949 // Debugging 950 virtual void verify() const; 951 952 // Used to increase collection frequency. "factor" of 0 means entire 953 // space. 954 void allocate_temporary_filler(int factor); 955 956 }; 957 958 959 // A dirty card to oop closure that does filtering. 960 // It knows how to filter out objects that are outside of the _boundary. 961 class Filtering_DCTOC : public DirtyCardToOopClosure { 962 protected: 963 // Override. 964 void walk_mem_region(MemRegion mr, 965 HeapWord* bottom, HeapWord* top); 966 967 // Walk the given memory region, from bottom to top, applying 968 // the given oop closure to (possibly) all objects found. The 969 // given oop closure may or may not be the same as the oop 970 // closure with which this closure was created, as it may 971 // be a filtering closure which makes use of the _boundary. 972 // We offer two signatures, so the FilteringClosure static type is 973 // apparent. 974 virtual void walk_mem_region_with_cl(MemRegion mr, 975 HeapWord* bottom, HeapWord* top, 976 ExtendedOopClosure* cl) = 0; 977 virtual void walk_mem_region_with_cl(MemRegion mr, 978 HeapWord* bottom, HeapWord* top, 979 FilteringClosure* cl) = 0; 980 981 public: 982 Filtering_DCTOC(Space* sp, ExtendedOopClosure* cl, 983 CardTableModRefBS::PrecisionStyle precision, 984 HeapWord* boundary) : 985 DirtyCardToOopClosure(sp, cl, precision, boundary) {} 986 }; 987 988 // A dirty card to oop closure for contiguous spaces 989 // (ContiguousSpace and sub-classes). 990 // It is a FilteringClosure, as defined above, and it knows: 991 // 992 // 1. That the actual top of any area in a memory region 993 // contained by the space is bounded by the end of the contiguous 994 // region of the space. 995 // 2. That the space is really made up of objects and not just 996 // blocks. 997 998 class ContiguousSpaceDCTOC : public Filtering_DCTOC { 999 protected: 1000 // Overrides. 1001 HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj); 1002 1003 virtual void walk_mem_region_with_cl(MemRegion mr, 1004 HeapWord* bottom, HeapWord* top, 1005 ExtendedOopClosure* cl); 1006 virtual void walk_mem_region_with_cl(MemRegion mr, 1007 HeapWord* bottom, HeapWord* top, 1008 FilteringClosure* cl); 1009 1010 public: 1011 ContiguousSpaceDCTOC(ContiguousSpace* sp, ExtendedOopClosure* cl, 1012 CardTableModRefBS::PrecisionStyle precision, 1013 HeapWord* boundary) : 1014 Filtering_DCTOC(sp, cl, precision, boundary) 1015 {} 1016 }; 1017 1018 1019 // Class EdenSpace describes eden-space in new generation. 1020 1021 class DefNewGeneration; 1022 1023 class EdenSpace : public ContiguousSpace { 1024 friend class VMStructs; 1025 private: 1026 DefNewGeneration* _gen; 1027 1028 // _soft_end is used as a soft limit on allocation. As soft limits are 1029 // reached, the slow-path allocation code can invoke other actions and then 1030 // adjust _soft_end up to a new soft limit or to end(). 1031 HeapWord* _soft_end; 1032 1033 public: 1034 EdenSpace(DefNewGeneration* gen) : 1035 _gen(gen), _soft_end(NULL) {} 1036 1037 // Get/set just the 'soft' limit. 1038 HeapWord* soft_end() { return _soft_end; } 1039 HeapWord** soft_end_addr() { return &_soft_end; } 1040 void set_soft_end(HeapWord* value) { _soft_end = value; } 1041 1042 // Override. 1043 void clear(bool mangle_space); 1044 1045 // Set both the 'hard' and 'soft' limits (_end and _soft_end). 1046 void set_end(HeapWord* value) { 1047 set_soft_end(value); 1048 ContiguousSpace::set_end(value); 1049 } 1050 1051 // Allocation (return NULL if full) 1052 HeapWord* allocate(size_t word_size); 1053 HeapWord* par_allocate(size_t word_size); 1054 }; 1055 1056 // Class ConcEdenSpace extends EdenSpace for the sake of safe 1057 // allocation while soft-end is being modified concurrently 1058 1059 class ConcEdenSpace : public EdenSpace { 1060 public: 1061 ConcEdenSpace(DefNewGeneration* gen) : EdenSpace(gen) { } 1062 1063 // Allocation (return NULL if full) 1064 HeapWord* par_allocate(size_t word_size); 1065 }; 1066 1067 1068 // A ContigSpace that Supports an efficient "block_start" operation via 1069 // a BlockOffsetArray (whose BlockOffsetSharedArray may be shared with 1070 // other spaces.) This is the abstract base class for old generation 1071 // (tenured) spaces. 1072 1073 class OffsetTableContigSpace: public ContiguousSpace { 1074 friend class VMStructs; 1075 protected: 1076 BlockOffsetArrayContigSpace _offsets; 1077 Mutex _par_alloc_lock; 1078 1079 public: 1080 // Constructor 1081 OffsetTableContigSpace(BlockOffsetSharedArray* sharedOffsetArray, 1082 MemRegion mr); 1083 1084 void set_bottom(HeapWord* value); 1085 void set_end(HeapWord* value); 1086 1087 void clear(bool mangle_space); 1088 1089 inline HeapWord* block_start_const(const void* p) const; 1090 1091 // Add offset table update. 1092 virtual inline HeapWord* allocate(size_t word_size); 1093 inline HeapWord* par_allocate(size_t word_size); 1094 1095 // MarkSweep support phase3 1096 virtual HeapWord* initialize_threshold(); 1097 virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* end); 1098 1099 virtual void print_on(outputStream* st) const; 1100 1101 // Debugging 1102 void verify() const; 1103 }; 1104 1105 1106 // Class TenuredSpace is used by TenuredGeneration 1107 1108 class TenuredSpace: public OffsetTableContigSpace { 1109 friend class VMStructs; 1110 protected: 1111 // Mark sweep support 1112 size_t allowed_dead_ratio() const; 1113 public: 1114 // Constructor 1115 TenuredSpace(BlockOffsetSharedArray* sharedOffsetArray, 1116 MemRegion mr) : 1117 OffsetTableContigSpace(sharedOffsetArray, mr) {} 1118 }; 1119 #endif // SHARE_VM_MEMORY_SPACE_HPP