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_GC_SHARED_SPACE_HPP
26 #define SHARE_GC_SHARED_SPACE_HPP
27
28 #include "gc/shared/blockOffsetTable.hpp"
29 #include "gc/shared/cardTable.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/markWord.hpp"
35 #include "runtime/mutexLocker.hpp"
36 #include "utilities/align.hpp"
37 #include "utilities/macros.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 CardTableRS;
52 class DirtyCardToOopClosure;
53 class SlidingForwarding;
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 Space():
74 _bottom(NULL), _end(NULL) { }
75
76 public:
77 // Accessors
78 HeapWord* bottom() const { return _bottom; }
79 HeapWord* end() const { return _end; }
80 virtual void set_bottom(HeapWord* value) { _bottom = value; }
81 virtual void set_end(HeapWord* value) { _end = value; }
82
83 virtual HeapWord* saved_mark_word() const { return _saved_mark_word; }
84
85 void set_saved_mark_word(HeapWord* p) { _saved_mark_word = p; }
86
87 // Returns true if this object has been allocated since a
88 // generation's "save_marks" call.
89 virtual bool obj_allocated_since_save_marks(const oop obj) const {
90 return cast_from_oop<HeapWord*>(obj) >= saved_mark_word();
91 }
92
93 // Returns a subregion of the space containing only the allocated objects in
94 // the space.
95 virtual MemRegion used_region() const = 0;
96
97 // Returns a region that is guaranteed to contain (at least) all objects
98 // allocated at the time of the last call to "save_marks". If the space
99 // initializes its DirtyCardToOopClosure's specifying the "contig" option
100 // (that is, if the space is contiguous), then this region must contain only
101 // such objects: the memregion will be from the bottom of the region to the
102 // saved mark. Otherwise, the "obj_allocated_since_save_marks" method of
103 // the space must distinguish between objects in the region allocated before
104 // and after the call to save marks.
105 MemRegion used_region_at_save_marks() const {
106 return MemRegion(bottom(), saved_mark_word());
107 }
108
109 // Initialization.
110 // "initialize" should be called once on a space, before it is used for
111 // any purpose. The "mr" arguments gives the bounds of the space, and
112 // the "clear_space" argument should be true unless the memory in "mr" is
113 // known to be zeroed.
114 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
115
116 // The "clear" method must be called on a region that may have
117 // had allocation performed in it, but is now to be considered empty.
118 virtual void clear(bool mangle_space);
119
120 // For detecting GC bugs. Should only be called at GC boundaries, since
121 // some unused space may be used as scratch space during GC's.
122 // We also call this when expanding a space to satisfy an allocation
123 // request. See bug #4668531
124 virtual void mangle_unused_area() = 0;
125 virtual void mangle_unused_area_complete() = 0;
126
127 // Testers
128 bool is_empty() const { return used() == 0; }
129 bool not_empty() const { return used() > 0; }
130
131 // Returns true iff the given the space contains the
132 // given address as part of an allocated object. For
133 // certain kinds of spaces, this might be a potentially
134 // expensive operation. To prevent performance problems
135 // on account of its inadvertent use in product jvm's,
136 // we restrict its use to assertion checks only.
137 bool is_in(const void* p) const {
138 return used_region().contains(p);
139 }
140 bool is_in(oop obj) const {
141 return is_in((void*)obj);
142 }
143
144 // Returns true iff the given reserved memory of the space contains the
145 // given address.
146 bool is_in_reserved(const void* p) const { return _bottom <= p && p < _end; }
147
148 // Returns true iff the given block is not allocated.
149 virtual bool is_free_block(const HeapWord* p) const = 0;
150
151 // Test whether p is double-aligned
152 static bool is_aligned(void* p) {
153 return ::is_aligned(p, sizeof(double));
154 }
155
156 // Size computations. Sizes are in bytes.
157 size_t capacity() const { return byte_size(bottom(), end()); }
158 virtual size_t used() const = 0;
159 virtual size_t free() const = 0;
160
161 // Iterate over all the ref-containing fields of all objects in the
162 // space, calling "cl.do_oop" on each. Fields in objects allocated by
163 // applications of the closure are not included in the iteration.
164 virtual void oop_iterate(OopIterateClosure* cl);
165
166 // Iterate over all objects in the space, calling "cl.do_object" on
167 // each. Objects allocated by applications of the closure are not
168 // included in the iteration.
169 virtual void object_iterate(ObjectClosure* blk) = 0;
170
171 // Create and return a new dirty card to oop closure. Can be
172 // overridden to return the appropriate type of closure
173 // depending on the type of space in which the closure will
174 // operate. ResourceArea allocated.
175 virtual DirtyCardToOopClosure* new_dcto_cl(OopIterateClosure* cl,
176 CardTable::PrecisionStyle precision,
177 HeapWord* boundary);
178
179 // If "p" is in the space, returns the address of the start of the
180 // "block" that contains "p". We say "block" instead of "object" since
181 // some heaps may not pack objects densely; a chunk may either be an
182 // object or a non-object. If "p" is not in the space, return NULL.
183 virtual HeapWord* block_start_const(const void* p) const = 0;
184
185 // The non-const version may have benevolent side effects on the data
186 // structure supporting these calls, possibly speeding up future calls.
187 // The default implementation, however, is simply to call the const
188 // version.
189 virtual HeapWord* block_start(const void* p);
190
191 // Requires "addr" to be the start of a chunk, and returns its size.
192 // "addr + size" is required to be the start of a new chunk, or the end
193 // of the active area of the heap.
194 virtual size_t block_size(const HeapWord* addr) const = 0;
195
196 // Requires "addr" to be the start of a block, and returns "TRUE" iff
197 // the block is an object.
198 virtual bool block_is_obj(const HeapWord* addr) const = 0;
199
200 // Requires "addr" to be the start of a block, and returns "TRUE" iff
201 // the block is an object and the object is alive.
202 virtual bool obj_is_alive(const HeapWord* addr) const;
203
204 // Allocation (return NULL if full). Assumes the caller has established
205 // mutually exclusive access to the space.
206 virtual HeapWord* allocate(size_t word_size) = 0;
207
208 // Allocation (return NULL if full). Enforces mutual exclusion internally.
209 virtual HeapWord* par_allocate(size_t word_size) = 0;
210
211 #if INCLUDE_SERIALGC
212 // Mark-sweep-compact support: all spaces can update pointers to objects
213 // moving as a part of compaction.
214 virtual void adjust_pointers() = 0;
215 #endif
216
217 virtual void print() const;
218 virtual void print_on(outputStream* st) const;
219 virtual void print_short() const;
220 virtual void print_short_on(outputStream* st) const;
221
222
223 // IF "this" is a ContiguousSpace, return it, else return NULL.
224 virtual ContiguousSpace* toContiguousSpace() {
225 return NULL;
226 }
227
228 // Debugging
229 virtual void verify() const = 0;
230 };
231
232 // A MemRegionClosure (ResourceObj) whose "do_MemRegion" function applies an
233 // OopClosure to (the addresses of) all the ref-containing fields that could
234 // be modified by virtue of the given MemRegion being dirty. (Note that
235 // because of the imprecise nature of the write barrier, this may iterate
236 // over oops beyond the region.)
237 // This base type for dirty card to oop closures handles memory regions
238 // in non-contiguous spaces with no boundaries, and should be sub-classed
239 // to support other space types. See ContiguousDCTOC for a sub-class
240 // that works with ContiguousSpaces.
241
242 class DirtyCardToOopClosure: public MemRegionClosureRO {
243 protected:
244 OopIterateClosure* _cl;
245 Space* _sp;
246 CardTable::PrecisionStyle _precision;
247 HeapWord* _boundary; // If non-NULL, process only non-NULL oops
248 // pointing below boundary.
249 HeapWord* _min_done; // ObjHeadPreciseArray precision requires
250 // a downwards traversal; this is the
251 // lowest location already done (or,
252 // alternatively, the lowest address that
253 // shouldn't be done again. NULL means infinity.)
254 NOT_PRODUCT(HeapWord* _last_bottom;)
255 NOT_PRODUCT(HeapWord* _last_explicit_min_done;)
256
257 // Get the actual top of the area on which the closure will
258 // operate, given where the top is assumed to be (the end of the
259 // memory region passed to do_MemRegion) and where the object
260 // at the top is assumed to start. For example, an object may
261 // start at the top but actually extend past the assumed top,
262 // in which case the top becomes the end of the object.
263 virtual HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj);
264
265 // Walk the given memory region from bottom to (actual) top
266 // looking for objects and applying the oop closure (_cl) to
267 // them. The base implementation of this treats the area as
268 // blocks, where a block may or may not be an object. Sub-
269 // classes should override this to provide more accurate
270 // or possibly more efficient walking.
271 virtual void walk_mem_region(MemRegion mr, HeapWord* bottom, HeapWord* top);
272
273 public:
274 DirtyCardToOopClosure(Space* sp, OopIterateClosure* cl,
275 CardTable::PrecisionStyle precision,
276 HeapWord* boundary) :
277 _cl(cl), _sp(sp), _precision(precision), _boundary(boundary),
278 _min_done(NULL) {
279 NOT_PRODUCT(_last_bottom = NULL);
280 NOT_PRODUCT(_last_explicit_min_done = NULL);
281 }
282
283 void do_MemRegion(MemRegion mr);
284
285 void set_min_done(HeapWord* min_done) {
286 _min_done = min_done;
287 NOT_PRODUCT(_last_explicit_min_done = _min_done);
288 }
289 #ifndef PRODUCT
290 void set_last_bottom(HeapWord* last_bottom) {
291 _last_bottom = last_bottom;
292 }
293 #endif
294 };
295
296 // A structure to represent a point at which objects are being copied
297 // during compaction.
298 class CompactPoint : public StackObj {
299 public:
300 Generation* gen;
301 CompactibleSpace* space;
302 HeapWord* threshold;
303
304 CompactPoint(Generation* g = NULL) :
305 gen(g), space(NULL), threshold(0) {}
306 };
307
308 // A space that supports compaction operations. This is usually, but not
309 // necessarily, a space that is normally contiguous. But, for example, a
310 // free-list-based space whose normal collection is a mark-sweep without
311 // compaction could still support compaction in full GC's.
312 //
313 // The compaction operations are implemented by the
314 // scan_and_{adjust_pointers,compact,forward} function templates.
315 // The following are, non-virtual, auxiliary functions used by these function templates:
316 // - scan_limit()
317 // - scanned_block_is_obj()
318 // - scanned_block_size()
319 // - adjust_obj_size()
320 // - obj_size()
321 // These functions are to be used exclusively by the scan_and_* function templates,
322 // and must be defined for all (non-abstract) subclasses of CompactibleSpace.
323 //
324 // NOTE: Any subclasses to CompactibleSpace wanting to change/define the behavior
325 // in any of the auxiliary functions must also override the corresponding
326 // prepare_for_compaction/adjust_pointers/compact functions using them.
327 // If not, such changes will not be used or have no effect on the compaction operations.
328 //
329 // This translates to the following dependencies:
330 // Overrides/definitions of
331 // - scan_limit
332 // - scanned_block_is_obj
333 // - scanned_block_size
334 // require override/definition of prepare_for_compaction().
335 // Similar dependencies exist between
336 // - adjust_obj_size and adjust_pointers()
337 // - obj_size and compact().
338 //
339 // Additionally, this also means that changes to block_size() or block_is_obj() that
340 // should be effective during the compaction operations must provide a corresponding
341 // definition of scanned_block_size/scanned_block_is_obj respectively.
342 class CompactibleSpace: public Space {
343 friend class VMStructs;
344 private:
345 HeapWord* _compaction_top;
346 CompactibleSpace* _next_compaction_space;
347
348 // Auxiliary functions for scan_and_{forward,adjust_pointers,compact} support.
349 inline size_t adjust_obj_size(size_t size) const {
350 return size;
351 }
352
353 inline size_t obj_size(const HeapWord* addr) const;
354
355 template <class SpaceType>
356 static inline void verify_up_to_first_dead(SpaceType* space) NOT_DEBUG_RETURN;
357
358 template <class SpaceType>
359 static inline void clear_empty_region(SpaceType* space);
360
361 public:
362 CompactibleSpace() :
363 _compaction_top(NULL), _next_compaction_space(NULL) {}
364
365 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
366 virtual void clear(bool mangle_space);
367
368 // Used temporarily during a compaction phase to hold the value
369 // top should have when compaction is complete.
370 HeapWord* compaction_top() const { return _compaction_top; }
371
372 void set_compaction_top(HeapWord* value) {
373 assert(value == NULL || (value >= bottom() && value <= end()),
374 "should point inside space");
375 _compaction_top = value;
376 }
377
378 // Perform operations on the space needed after a compaction
379 // has been performed.
380 virtual void reset_after_compaction() = 0;
381
382 // Returns the next space (in the current generation) to be compacted in
383 // the global compaction order. Also is used to select the next
384 // space into which to compact.
385
386 virtual CompactibleSpace* next_compaction_space() const {
387 return _next_compaction_space;
388 }
389
390 void set_next_compaction_space(CompactibleSpace* csp) {
391 _next_compaction_space = csp;
392 }
393
394 #if INCLUDE_SERIALGC
395 // MarkSweep support phase2
396
397 // Start the process of compaction of the current space: compute
398 // post-compaction addresses, and insert forwarding pointers. The fields
399 // "cp->gen" and "cp->compaction_space" are the generation and space into
400 // which we are currently compacting. This call updates "cp" as necessary,
401 // and leaves the "compaction_top" of the final value of
402 // "cp->compaction_space" up-to-date. Offset tables may be updated in
403 // this phase as if the final copy had occurred; if so, "cp->threshold"
404 // indicates when the next such action should be taken.
405 virtual void prepare_for_compaction(CompactPoint* cp) = 0;
406 // MarkSweep support phase3
407 virtual void adjust_pointers();
408 // MarkSweep support phase4
409 virtual void compact();
410 #endif // INCLUDE_SERIALGC
411
412 // The maximum percentage of objects that can be dead in the compacted
413 // live part of a compacted space ("deadwood" support.)
414 virtual size_t allowed_dead_ratio() const { return 0; };
415
416 // Some contiguous spaces may maintain some data structures that should
417 // be updated whenever an allocation crosses a boundary. This function
418 // returns the first such boundary.
419 // (The default implementation returns the end of the space, so the
420 // boundary is never crossed.)
421 virtual HeapWord* initialize_threshold() { return end(); }
422
423 // "q" is an object of the given "size" that should be forwarded;
424 // "cp" names the generation ("gen") and containing "this" (which must
425 // also equal "cp->space"). "compact_top" is where in "this" the
426 // next object should be forwarded to. If there is room in "this" for
427 // the object, insert an appropriate forwarding pointer in "q".
428 // If not, go to the next compaction space (there must
429 // be one, since compaction must succeed -- we go to the first space of
430 // the previous generation if necessary, updating "cp"), reset compact_top
431 // and then forward. In either case, returns the new value of "compact_top".
432 // If the forwarding crosses "cp->threshold", invokes the "cross_threshold"
433 // function of the then-current compaction space, and updates "cp->threshold
434 // accordingly".
435 virtual HeapWord* forward(oop q, size_t size, CompactPoint* cp,
436 HeapWord* compact_top, SlidingForwarding* const forwarding);
437
438 // Return a size with adjustments as required of the space.
439 virtual size_t adjust_object_size_v(size_t size) const { return size; }
440
441 void set_first_dead(HeapWord* value) { _first_dead = value; }
442 void set_end_of_live(HeapWord* value) { _end_of_live = value; }
443
444 protected:
445 // Used during compaction.
446 HeapWord* _first_dead;
447 HeapWord* _end_of_live;
448
449 // This the function is invoked when an allocation of an object covering
450 // "start" to "end occurs crosses the threshold; returns the next
451 // threshold. (The default implementation does nothing.)
452 virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* the_end) {
453 return end();
454 }
455
456 // Below are template functions for scan_and_* algorithms (avoiding virtual calls).
457 // The space argument should be a subclass of CompactibleSpace, implementing
458 // scan_limit(), scanned_block_is_obj(), and scanned_block_size(),
459 // and possibly also overriding obj_size(), and adjust_obj_size().
460 // These functions should avoid virtual calls whenever possible.
461
462 #if INCLUDE_SERIALGC
463 // Frequently calls adjust_obj_size().
464 template <class SpaceType>
465 static inline void scan_and_adjust_pointers(SpaceType* space);
466 #endif
467
468 // Frequently calls obj_size().
469 template <class SpaceType>
470 static inline void scan_and_compact(SpaceType* space);
471
472 // Frequently calls scanned_block_is_obj() and scanned_block_size().
473 // Requires the scan_limit() function.
474 template <class SpaceType>
475 static inline void scan_and_forward(SpaceType* space, CompactPoint* cp);
476 };
477
478 class GenSpaceMangler;
479
480 // A space in which the free area is contiguous. It therefore supports
481 // faster allocation, and compaction.
482 class ContiguousSpace: public CompactibleSpace {
483 friend class VMStructs;
484 // Allow scan_and_forward function to call (private) overrides for auxiliary functions on this class
485 template <typename SpaceType>
486 friend void CompactibleSpace::scan_and_forward(SpaceType* space, CompactPoint* cp);
487
488 private:
489 // Auxiliary functions for scan_and_forward support.
490 // See comments for CompactibleSpace for more information.
491 inline HeapWord* scan_limit() const {
492 return top();
493 }
494
495 inline bool scanned_block_is_obj(const HeapWord* addr) const {
496 return true; // Always true, since scan_limit is top
497 }
498
499 inline size_t scanned_block_size(const HeapWord* addr) const;
500
501 protected:
502 HeapWord* _top;
503 // A helper for mangling the unused area of the space in debug builds.
504 GenSpaceMangler* _mangler;
505
506 GenSpaceMangler* mangler() { return _mangler; }
507
508 // Allocation helpers (return NULL if full).
509 inline HeapWord* allocate_impl(size_t word_size);
510 inline HeapWord* par_allocate_impl(size_t word_size);
511
512 public:
513 ContiguousSpace();
514 ~ContiguousSpace();
515
516 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
517 virtual void clear(bool mangle_space);
518
519 // Accessors
520 HeapWord* top() const { return _top; }
521 void set_top(HeapWord* value) { _top = value; }
522
523 void set_saved_mark() { _saved_mark_word = top(); }
524 void reset_saved_mark() { _saved_mark_word = bottom(); }
525
526 bool saved_mark_at_top() const { return saved_mark_word() == top(); }
527
528 // In debug mode mangle (write it with a particular bit
529 // pattern) the unused part of a space.
530
531 // Used to save the an address in a space for later use during mangling.
532 void set_top_for_allocations(HeapWord* v) PRODUCT_RETURN;
533 // Used to save the space's current top for later use during mangling.
534 void set_top_for_allocations() PRODUCT_RETURN;
535
536 // Mangle regions in the space from the current top up to the
537 // previously mangled part of the space.
538 void mangle_unused_area() PRODUCT_RETURN;
539 // Mangle [top, end)
540 void mangle_unused_area_complete() PRODUCT_RETURN;
541
542 // Do some sparse checking on the area that should have been mangled.
543 void check_mangled_unused_area(HeapWord* limit) PRODUCT_RETURN;
544 // Check the complete area that should have been mangled.
545 // This code may be NULL depending on the macro DEBUG_MANGLING.
546 void check_mangled_unused_area_complete() PRODUCT_RETURN;
547
548 // Size computations: sizes in bytes.
549 size_t capacity() const { return byte_size(bottom(), end()); }
550 size_t used() const { return byte_size(bottom(), top()); }
551 size_t free() const { return byte_size(top(), end()); }
552
553 virtual bool is_free_block(const HeapWord* p) const;
554
555 // In a contiguous space we have a more obvious bound on what parts
556 // contain objects.
557 MemRegion used_region() const { return MemRegion(bottom(), top()); }
558
559 // Allocation (return NULL if full)
560 virtual HeapWord* allocate(size_t word_size);
561 virtual HeapWord* par_allocate(size_t word_size);
562
563 // Iteration
564 void oop_iterate(OopIterateClosure* cl);
565 void object_iterate(ObjectClosure* blk);
566
567 // Compaction support
568 virtual void reset_after_compaction() {
569 assert(compaction_top() >= bottom() && compaction_top() <= end(), "should point inside space");
570 set_top(compaction_top());
571 }
572
573 // Override.
574 DirtyCardToOopClosure* new_dcto_cl(OopIterateClosure* cl,
575 CardTable::PrecisionStyle precision,
576 HeapWord* boundary);
577
578 // Apply "blk->do_oop" to the addresses of all reference fields in objects
579 // starting with the _saved_mark_word, which was noted during a generation's
580 // save_marks and is required to denote the head of an object.
581 // Fields in objects allocated by applications of the closure
582 // *are* included in the iteration.
583 // Updates _saved_mark_word to point to just after the last object
584 // iterated over.
585 template <typename OopClosureType>
586 void oop_since_save_marks_iterate(OopClosureType* blk);
587
588 // Same as object_iterate, but starting from "mark", which is required
589 // to denote the start of an object. Objects allocated by
590 // applications of the closure *are* included in the iteration.
591 virtual void object_iterate_from(HeapWord* mark, ObjectClosure* blk);
592
593 // Very inefficient implementation.
594 virtual HeapWord* block_start_const(const void* p) const;
595 size_t block_size(const HeapWord* p) const;
596 // If a block is in the allocated area, it is an object.
597 bool block_is_obj(const HeapWord* p) const { return p < top(); }
598
599 // Addresses for inlined allocation
600 HeapWord** top_addr() { return &_top; }
601 HeapWord** end_addr() { return &_end; }
602
603 #if INCLUDE_SERIALGC
604 // Overrides for more efficient compaction support.
605 void prepare_for_compaction(CompactPoint* cp);
606 #endif
607
608 virtual void print_on(outputStream* st) const;
609
610 // Checked dynamic downcasts.
611 virtual ContiguousSpace* toContiguousSpace() {
612 return this;
613 }
614
615 // Debugging
616 virtual void verify() const;
617
618 // Used to increase collection frequency. "factor" of 0 means entire
619 // space.
620 void allocate_temporary_filler(int factor);
621 };
622
623
624 // A dirty card to oop closure that does filtering.
625 // It knows how to filter out objects that are outside of the _boundary.
626 class FilteringDCTOC : public DirtyCardToOopClosure {
627 protected:
628 // Override.
629 void walk_mem_region(MemRegion mr,
630 HeapWord* bottom, HeapWord* top);
631
632 // Walk the given memory region, from bottom to top, applying
633 // the given oop closure to (possibly) all objects found. The
634 // given oop closure may or may not be the same as the oop
635 // closure with which this closure was created, as it may
636 // be a filtering closure which makes use of the _boundary.
637 // We offer two signatures, so the FilteringClosure static type is
638 // apparent.
639 virtual void walk_mem_region_with_cl(MemRegion mr,
640 HeapWord* bottom, HeapWord* top,
641 OopIterateClosure* cl) = 0;
642 virtual void walk_mem_region_with_cl(MemRegion mr,
643 HeapWord* bottom, HeapWord* top,
644 FilteringClosure* cl) = 0;
645
646 public:
647 FilteringDCTOC(Space* sp, OopIterateClosure* cl,
648 CardTable::PrecisionStyle precision,
649 HeapWord* boundary) :
650 DirtyCardToOopClosure(sp, cl, precision, boundary) {}
651 };
652
653 // A dirty card to oop closure for contiguous spaces
654 // (ContiguousSpace and sub-classes).
655 // It is a FilteringClosure, as defined above, and it knows:
656 //
657 // 1. That the actual top of any area in a memory region
658 // contained by the space is bounded by the end of the contiguous
659 // region of the space.
660 // 2. That the space is really made up of objects and not just
661 // blocks.
662
663 class ContiguousSpaceDCTOC : public FilteringDCTOC {
664 protected:
665 // Overrides.
666 HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj);
667
668 virtual void walk_mem_region_with_cl(MemRegion mr,
669 HeapWord* bottom, HeapWord* top,
670 OopIterateClosure* cl);
671 virtual void walk_mem_region_with_cl(MemRegion mr,
672 HeapWord* bottom, HeapWord* top,
673 FilteringClosure* cl);
674
675 public:
676 ContiguousSpaceDCTOC(ContiguousSpace* sp, OopIterateClosure* cl,
677 CardTable::PrecisionStyle precision,
678 HeapWord* boundary) :
679 FilteringDCTOC(sp, cl, precision, boundary)
680 {}
681 };
682
683 // A ContigSpace that Supports an efficient "block_start" operation via
684 // a BlockOffsetArray (whose BlockOffsetSharedArray may be shared with
685 // other spaces.) This is the abstract base class for old generation
686 // (tenured) spaces.
687
688 class OffsetTableContigSpace: public ContiguousSpace {
689 friend class VMStructs;
690 protected:
691 BlockOffsetArrayContigSpace _offsets;
692 Mutex _par_alloc_lock;
693
694 public:
695 // Constructor
696 OffsetTableContigSpace(BlockOffsetSharedArray* sharedOffsetArray,
697 MemRegion mr);
698
699 void set_bottom(HeapWord* value);
700 void set_end(HeapWord* value);
701
702 void clear(bool mangle_space);
703
704 inline HeapWord* block_start_const(const void* p) const;
705
706 // Add offset table update.
707 virtual inline HeapWord* allocate(size_t word_size);
708 inline HeapWord* par_allocate(size_t word_size);
709
710 // MarkSweep support phase3
711 virtual HeapWord* initialize_threshold();
712 virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* end);
713
714 virtual void print_on(outputStream* st) const;
715
716 // Debugging
717 void verify() const;
718 };
719
720
721 // Class TenuredSpace is used by TenuredGeneration
722
723 class TenuredSpace: public OffsetTableContigSpace {
724 friend class VMStructs;
725 protected:
726 // Mark sweep support
727 size_t allowed_dead_ratio() const;
728 public:
729 // Constructor
730 TenuredSpace(BlockOffsetSharedArray* sharedOffsetArray,
731 MemRegion mr) :
732 OffsetTableContigSpace(sharedOffsetArray, mr) {}
733 };
734 #endif // SHARE_GC_SHARED_SPACE_HPP