1 /*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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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 public:
366 CompactibleSpace() :
367 _compaction_top(NULL), _next_compaction_space(NULL) {}
368
369 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
370 virtual void clear(bool mangle_space);
371
372 // Used temporarily during a compaction phase to hold the value
373 // top should have when compaction is complete.
374 HeapWord* compaction_top() const { return _compaction_top; }
375
376 void set_compaction_top(HeapWord* value) {
377 assert(value == NULL || (value >= bottom() && value <= end()),
378 "should point inside space");
379 _compaction_top = value;
380 }
381
382 // Perform operations on the space needed after a compaction
383 // has been performed.
384 virtual void reset_after_compaction() = 0;
385
386 // Returns the next space (in the current generation) to be compacted in
387 // the global compaction order. Also is used to select the next
388 // space into which to compact.
389
390 virtual CompactibleSpace* next_compaction_space() const {
391 return _next_compaction_space;
392 }
393
394 void set_next_compaction_space(CompactibleSpace* csp) {
395 _next_compaction_space = csp;
396 }
397
398 // MarkSweep support phase2
399
400 // Start the process of compaction of the current space: compute
401 // post-compaction addresses, and insert forwarding pointers. The fields
402 // "cp->gen" and "cp->compaction_space" are the generation and space into
403 // which we are currently compacting. This call updates "cp" as necessary,
404 // and leaves the "compaction_top" of the final value of
405 // "cp->compaction_space" up-to-date. Offset tables may be updated in
406 // this phase as if the final copy had occurred; if so, "cp->threshold"
407 // indicates when the next such action should be taken.
408 virtual void prepare_for_compaction(CompactPoint* cp) = 0;
409 // MarkSweep support phase3
410 virtual void adjust_pointers();
411 // MarkSweep support phase4
412 virtual void compact();
413
414 // The maximum percentage of objects that can be dead in the compacted
415 // live part of a compacted space ("deadwood" support.)
416 virtual size_t allowed_dead_ratio() const { return 0; };
417
418 // Some contiguous spaces may maintain some data structures that should
419 // be updated whenever an allocation crosses a boundary. This function
420 // returns the first such boundary.
421 // (The default implementation returns the end of the space, so the
422 // boundary is never crossed.)
423 virtual HeapWord* initialize_threshold() { return end(); }
424
425 // "q" is an object of the given "size" that should be forwarded;
426 // "cp" names the generation ("gen") and containing "this" (which must
427 // also equal "cp->space"). "compact_top" is where in "this" the
428 // next object should be forwarded to. If there is room in "this" for
429 // the object, insert an appropriate forwarding pointer in "q".
430 // If not, go to the next compaction space (there must
431 // be one, since compaction must succeed -- we go to the first space of
432 // the previous generation if necessary, updating "cp"), reset compact_top
433 // and then forward. In either case, returns the new value of "compact_top".
434 // If the forwarding crosses "cp->threshold", invokes the "cross_threshold"
435 // function of the then-current compaction space, and updates "cp->threshold
436 // accordingly".
437 virtual HeapWord* forward(oop q, size_t size, CompactPoint* cp,
438 HeapWord* compact_top);
439
440 // Return a size with adjustments as required of the space.
441 virtual size_t adjust_object_size_v(size_t size) const { return size; }
442
443 protected:
444 // Used during compaction.
445 HeapWord* _first_dead;
446 HeapWord* _end_of_live;
447
448 // Minimum size of a free block.
449 virtual size_t minimum_free_block_size() const { return 0; }
450
451 // This the function is invoked when an allocation of an object covering
452 // "start" to "end occurs crosses the threshold; returns the next
453 // threshold. (The default implementation does nothing.)
454 virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* the_end) {
455 return end();
456 }
457
458 // Requires "allowed_deadspace_words > 0", that "q" is the start of a
459 // free block of the given "word_len", and that "q", were it an object,
460 // would not move if forwarded. If the size allows, fill the free
461 // block with an object, to prevent excessive compaction. Returns "true"
462 // iff the free region was made deadspace, and modifies
463 // "allowed_deadspace_words" to reflect the number of available deadspace
464 // words remaining after this operation.
465 bool insert_deadspace(size_t& allowed_deadspace_words, HeapWord* q,
466 size_t word_len);
467
468 // Below are template functions for scan_and_* algorithms (avoiding virtual calls).
469 // The space argument should be a subclass of CompactibleSpace, implementing
470 // scan_limit(), scanned_block_is_obj(), and scanned_block_size(),
471 // and possibly also overriding obj_size(), and adjust_obj_size().
472 // These functions should avoid virtual calls whenever possible.
473
474 // Frequently calls adjust_obj_size().
475 template <class SpaceType>
476 static inline void scan_and_adjust_pointers(SpaceType* space);
477
478 // Frequently calls obj_size().
479 template <class SpaceType>
480 static inline void scan_and_compact(SpaceType* space);
481
482 // Frequently calls scanned_block_is_obj() and scanned_block_size().
483 // Requires the scan_limit() function.
484 template <class SpaceType>
485 static inline void scan_and_forward(SpaceType* space, CompactPoint* cp);
486 };
487
488 class GenSpaceMangler;
489
490 // A space in which the free area is contiguous. It therefore supports
491 // faster allocation, and compaction.
492 class ContiguousSpace: public CompactibleSpace {
493 friend class VMStructs;
494 // Allow scan_and_forward function to call (private) overrides for auxiliary functions on this class
495 template <typename SpaceType>
496 friend void CompactibleSpace::scan_and_forward(SpaceType* space, CompactPoint* cp);
497
498 private:
499 // Auxiliary functions for scan_and_forward support.
500 // See comments for CompactibleSpace for more information.
501 inline HeapWord* scan_limit() const {
502 return top();
503 }
504
505 inline bool scanned_block_is_obj(const HeapWord* addr) const {
506 return true; // Always true, since scan_limit is top
507 }
508
509 inline size_t scanned_block_size(const HeapWord* addr) const;
510
511 protected:
512 HeapWord* _top;
513 HeapWord* _concurrent_iteration_safe_limit;
514 // A helper for mangling the unused area of the space in debug builds.
515 GenSpaceMangler* _mangler;
516
517 GenSpaceMangler* mangler() { return _mangler; }
518
519 // Allocation helpers (return NULL if full).
520 inline HeapWord* allocate_impl(size_t word_size);
521 inline HeapWord* par_allocate_impl(size_t word_size);
522
523 public:
524 ContiguousSpace();
525 ~ContiguousSpace();
526
527 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
528 virtual void clear(bool mangle_space);
529
530 // Accessors
531 HeapWord* top() const { return _top; }
532 void set_top(HeapWord* value) { _top = value; }
533
534 void set_saved_mark() { _saved_mark_word = top(); }
535 void reset_saved_mark() { _saved_mark_word = bottom(); }
536
537 bool saved_mark_at_top() const { return saved_mark_word() == top(); }
538
539 // In debug mode mangle (write it with a particular bit
540 // pattern) the unused part of a space.
541
542 // Used to save the an address in a space for later use during mangling.
543 void set_top_for_allocations(HeapWord* v) PRODUCT_RETURN;
544 // Used to save the space's current top for later use during mangling.
545 void set_top_for_allocations() PRODUCT_RETURN;
546
547 // Mangle regions in the space from the current top up to the
548 // previously mangled part of the space.
549 void mangle_unused_area() PRODUCT_RETURN;
550 // Mangle [top, end)
551 void mangle_unused_area_complete() PRODUCT_RETURN;
552
553 // Do some sparse checking on the area that should have been mangled.
554 void check_mangled_unused_area(HeapWord* limit) PRODUCT_RETURN;
555 // Check the complete area that should have been mangled.
556 // This code may be NULL depending on the macro DEBUG_MANGLING.
557 void check_mangled_unused_area_complete() PRODUCT_RETURN;
558
559 // Size computations: sizes in bytes.
560 size_t capacity() const { return byte_size(bottom(), end()); }
561 size_t used() const { return byte_size(bottom(), top()); }
562 size_t free() const { return byte_size(top(), end()); }
563
564 virtual bool is_free_block(const HeapWord* p) const;
565
566 // In a contiguous space we have a more obvious bound on what parts
567 // contain objects.
568 MemRegion used_region() const { return MemRegion(bottom(), top()); }
569
570 // Allocation (return NULL if full)
571 virtual HeapWord* allocate(size_t word_size);
572 virtual HeapWord* par_allocate(size_t word_size);
573 HeapWord* allocate_aligned(size_t word_size);
574
575 // Iteration
576 void oop_iterate(ExtendedOopClosure* cl);
577 void object_iterate(ObjectClosure* blk);
578 // For contiguous spaces this method will iterate safely over objects
579 // in the space (i.e., between bottom and top) when at a safepoint.
580 void safe_object_iterate(ObjectClosure* blk);
581
582 // Iterate over as many initialized objects in the space as possible,
583 // calling "cl.do_object_careful" on each. Return NULL if all objects
584 // in the space (at the start of the iteration) were iterated over.
585 // Return an address indicating the extent of the iteration in the
586 // event that the iteration had to return because of finding an
587 // uninitialized object in the space, or if the closure "cl"
588 // signaled early termination.
589 HeapWord* object_iterate_careful(ObjectClosureCareful* cl);
590 HeapWord* concurrent_iteration_safe_limit() {
591 assert(_concurrent_iteration_safe_limit <= top(),
592 "_concurrent_iteration_safe_limit update missed");
593 return _concurrent_iteration_safe_limit;
594 }
595 // changes the safe limit, all objects from bottom() to the new
596 // limit should be properly initialized
597 void set_concurrent_iteration_safe_limit(HeapWord* new_limit) {
598 assert(new_limit <= top(), "uninitialized objects in the safe range");
599 _concurrent_iteration_safe_limit = new_limit;
600 }
601
602
603 #if INCLUDE_ALL_GCS
604 // In support of parallel oop_iterate.
605 #define ContigSpace_PAR_OOP_ITERATE_DECL(OopClosureType, nv_suffix) \
606 void par_oop_iterate(MemRegion mr, OopClosureType* blk);
607
608 ALL_PAR_OOP_ITERATE_CLOSURES(ContigSpace_PAR_OOP_ITERATE_DECL)
609 #undef ContigSpace_PAR_OOP_ITERATE_DECL
610 #endif // INCLUDE_ALL_GCS
611
612 // Compaction support
613 virtual void reset_after_compaction() {
614 assert(compaction_top() >= bottom() && compaction_top() <= end(), "should point inside space");
615 set_top(compaction_top());
616 // set new iteration safe limit
617 set_concurrent_iteration_safe_limit(compaction_top());
618 }
619
620 // Override.
621 DirtyCardToOopClosure* new_dcto_cl(ExtendedOopClosure* cl,
622 CardTableModRefBS::PrecisionStyle precision,
623 HeapWord* boundary,
624 bool parallel);
625
626 // Apply "blk->do_oop" to the addresses of all reference fields in objects
627 // starting with the _saved_mark_word, which was noted during a generation's
628 // save_marks and is required to denote the head of an object.
629 // Fields in objects allocated by applications of the closure
630 // *are* included in the iteration.
631 // Updates _saved_mark_word to point to just after the last object
632 // iterated over.
633 #define ContigSpace_OOP_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
634 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk);
635
636 ALL_SINCE_SAVE_MARKS_CLOSURES(ContigSpace_OOP_SINCE_SAVE_MARKS_DECL)
637 #undef ContigSpace_OOP_SINCE_SAVE_MARKS_DECL
638
639 // Same as object_iterate, but starting from "mark", which is required
640 // to denote the start of an object. Objects allocated by
641 // applications of the closure *are* included in the iteration.
642 virtual void object_iterate_from(HeapWord* mark, ObjectClosure* blk);
643
644 // Very inefficient implementation.
645 virtual HeapWord* block_start_const(const void* p) const;
646 size_t block_size(const HeapWord* p) const;
647 // If a block is in the allocated area, it is an object.
648 bool block_is_obj(const HeapWord* p) const { return p < top(); }
649
650 // Addresses for inlined allocation
651 HeapWord** top_addr() { return &_top; }
652 HeapWord** end_addr() { return &_end; }
653
654 // Overrides for more efficient compaction support.
655 void prepare_for_compaction(CompactPoint* cp);
656
657 virtual void print_on(outputStream* st) const;
658
659 // Checked dynamic downcasts.
660 virtual ContiguousSpace* toContiguousSpace() {
661 return this;
662 }
663
664 // Debugging
665 virtual void verify() const;
666
667 // Used to increase collection frequency. "factor" of 0 means entire
668 // space.
669 void allocate_temporary_filler(int factor);
670 };
671
672
673 // A dirty card to oop closure that does filtering.
674 // It knows how to filter out objects that are outside of the _boundary.
675 class Filtering_DCTOC : public DirtyCardToOopClosure {
676 protected:
677 // Override.
678 void walk_mem_region(MemRegion mr,
679 HeapWord* bottom, HeapWord* top);
680
681 // Walk the given memory region, from bottom to top, applying
682 // the given oop closure to (possibly) all objects found. The
683 // given oop closure may or may not be the same as the oop
684 // closure with which this closure was created, as it may
685 // be a filtering closure which makes use of the _boundary.
686 // We offer two signatures, so the FilteringClosure static type is
687 // apparent.
688 virtual void walk_mem_region_with_cl(MemRegion mr,
689 HeapWord* bottom, HeapWord* top,
690 ExtendedOopClosure* cl) = 0;
691 virtual void walk_mem_region_with_cl(MemRegion mr,
692 HeapWord* bottom, HeapWord* top,
693 FilteringClosure* cl) = 0;
694
695 public:
696 Filtering_DCTOC(Space* sp, ExtendedOopClosure* cl,
697 CardTableModRefBS::PrecisionStyle precision,
698 HeapWord* boundary) :
699 DirtyCardToOopClosure(sp, cl, precision, boundary) {}
700 };
701
702 // A dirty card to oop closure for contiguous spaces
703 // (ContiguousSpace and sub-classes).
704 // It is a FilteringClosure, as defined above, and it knows:
705 //
706 // 1. That the actual top of any area in a memory region
707 // contained by the space is bounded by the end of the contiguous
708 // region of the space.
709 // 2. That the space is really made up of objects and not just
710 // blocks.
711
712 class ContiguousSpaceDCTOC : public Filtering_DCTOC {
713 protected:
714 // Overrides.
715 HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj);
716
717 virtual void walk_mem_region_with_cl(MemRegion mr,
718 HeapWord* bottom, HeapWord* top,
719 ExtendedOopClosure* cl);
720 virtual void walk_mem_region_with_cl(MemRegion mr,
721 HeapWord* bottom, HeapWord* top,
722 FilteringClosure* cl);
723
724 public:
725 ContiguousSpaceDCTOC(ContiguousSpace* sp, ExtendedOopClosure* cl,
726 CardTableModRefBS::PrecisionStyle precision,
727 HeapWord* boundary) :
728 Filtering_DCTOC(sp, cl, precision, boundary)
729 {}
730 };
731
732 // A ContigSpace that Supports an efficient "block_start" operation via
733 // a BlockOffsetArray (whose BlockOffsetSharedArray may be shared with
734 // other spaces.) This is the abstract base class for old generation
735 // (tenured) spaces.
736
737 class OffsetTableContigSpace: public ContiguousSpace {
738 friend class VMStructs;
739 protected:
740 BlockOffsetArrayContigSpace _offsets;
741 Mutex _par_alloc_lock;
742
743 public:
744 // Constructor
745 OffsetTableContigSpace(BlockOffsetSharedArray* sharedOffsetArray,
746 MemRegion mr);
747
748 void set_bottom(HeapWord* value);
749 void set_end(HeapWord* value);
750
751 void clear(bool mangle_space);
752
753 inline HeapWord* block_start_const(const void* p) const;
754
755 // Add offset table update.
756 virtual inline HeapWord* allocate(size_t word_size);
757 inline HeapWord* par_allocate(size_t word_size);
758
759 // MarkSweep support phase3
760 virtual HeapWord* initialize_threshold();
761 virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* end);
762
763 virtual void print_on(outputStream* st) const;
764
765 // Debugging
766 void verify() const;
767 };
768
769
770 // Class TenuredSpace is used by TenuredGeneration
771
772 class TenuredSpace: public OffsetTableContigSpace {
773 friend class VMStructs;
774 protected:
775 // Mark sweep support
776 size_t allowed_dead_ratio() const;
777 public:
778 // Constructor
779 TenuredSpace(BlockOffsetSharedArray* sharedOffsetArray,
780 MemRegion mr) :
781 OffsetTableContigSpace(sharedOffsetArray, mr) {}
782 };
783 #endif // SHARE_VM_GC_SHARED_SPACE_HPP