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
54 // A Space describes a heap area. Class Space is an abstract
55 // base class.
56 //
57 // Space supports allocation, size computation and GC support is provided.
58 //
59 // Invariant: bottom() and end() are on page_size boundaries and
60 // bottom() <= top() <= end()
61 // top() is inclusive and end() is exclusive.
62
63 class Space: public CHeapObj<mtGC> {
64 friend class VMStructs;
65 protected:
66 HeapWord* _bottom;
67 HeapWord* _end;
68
69 // Used in support of save_marks()
70 HeapWord* _saved_mark_word;
71
72 // A sequential tasks done structure. This supports
73 // parallel GC, where we have threads dynamically
74 // claiming sub-tasks from a larger parallel task.
75 SequentialSubTasksDone _par_seq_tasks;
76
77 Space():
78 _bottom(NULL), _end(NULL) { }
79
80 public:
81 // Accessors
82 HeapWord* bottom() const { return _bottom; }
83 HeapWord* end() const { return _end; }
84 virtual void set_bottom(HeapWord* value) { _bottom = value; }
85 virtual void set_end(HeapWord* value) { _end = value; }
86
87 virtual HeapWord* saved_mark_word() const { return _saved_mark_word; }
88
89 void set_saved_mark_word(HeapWord* p) { _saved_mark_word = p; }
90
91 // Returns true if this object has been allocated since a
92 // generation's "save_marks" call.
93 virtual bool obj_allocated_since_save_marks(const oop obj) const {
94 return (HeapWord*)obj >= saved_mark_word();
95 }
96
97 virtual MemRegionClosure* preconsumptionDirtyCardClosure() const {
98 return NULL;
99 }
100
101 // Returns a subregion of the space containing only the allocated objects in
102 // the space.
103 virtual MemRegion used_region() const = 0;
104
105 // Returns a region that is guaranteed to contain (at least) all objects
106 // allocated at the time of the last call to "save_marks". If the space
107 // initializes its DirtyCardToOopClosure's specifying the "contig" option
108 // (that is, if the space is contiguous), then this region must contain only
109 // such objects: the memregion will be from the bottom of the region to the
110 // saved mark. Otherwise, the "obj_allocated_since_save_marks" method of
111 // the space must distinguish between objects in the region allocated before
112 // and after the call to save marks.
113 MemRegion used_region_at_save_marks() const {
114 return MemRegion(bottom(), saved_mark_word());
115 }
116
117 // Initialization.
118 // "initialize" should be called once on a space, before it is used for
119 // any purpose. The "mr" arguments gives the bounds of the space, and
120 // the "clear_space" argument should be true unless the memory in "mr" is
121 // known to be zeroed.
122 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
123
124 // The "clear" method must be called on a region that may have
125 // had allocation performed in it, but is now to be considered empty.
126 virtual void clear(bool mangle_space);
127
128 // For detecting GC bugs. Should only be called at GC boundaries, since
129 // some unused space may be used as scratch space during GC's.
130 // We also call this when expanding a space to satisfy an allocation
131 // request. See bug #4668531
132 virtual void mangle_unused_area() = 0;
133 virtual void mangle_unused_area_complete() = 0;
134
135 // Testers
136 bool is_empty() const { return used() == 0; }
137 bool not_empty() const { return used() > 0; }
138
139 // Returns true iff the given the space contains the
140 // given address as part of an allocated object. For
141 // certain kinds of spaces, this might be a potentially
142 // expensive operation. To prevent performance problems
143 // on account of its inadvertent use in product jvm's,
144 // we restrict its use to assertion checks only.
145 bool is_in(const void* p) const {
146 return used_region().contains(p);
147 }
148 bool is_in(oop obj) const {
149 return is_in((void*)obj);
150 }
151
152 // Returns true iff the given reserved memory of the space contains the
153 // given address.
154 bool is_in_reserved(const void* p) const { return _bottom <= p && p < _end; }
155
156 // Returns true iff the given block is not allocated.
157 virtual bool is_free_block(const HeapWord* p) const = 0;
158
159 // Test whether p is double-aligned
160 static bool is_aligned(void* p) {
161 return ::is_aligned(p, sizeof(double));
162 }
163
164 // Size computations. Sizes are in bytes.
165 size_t capacity() const { return byte_size(bottom(), end()); }
166 virtual size_t used() const = 0;
167 virtual size_t free() const = 0;
168
169 // Iterate over all the ref-containing fields of all objects in the
170 // space, calling "cl.do_oop" on each. Fields in objects allocated by
171 // applications of the closure are not included in the iteration.
172 virtual void oop_iterate(OopIterateClosure* cl);
173
174 // Iterate over all objects in the space, calling "cl.do_object" on
175 // each. Objects allocated by applications of the closure are not
176 // included in the iteration.
177 virtual void object_iterate(ObjectClosure* blk) = 0;
178
179 // Create and return a new dirty card to oop closure. Can be
180 // overridden to return the appropriate type of closure
181 // depending on the type of space in which the closure will
182 // operate. ResourceArea allocated.
183 virtual DirtyCardToOopClosure* new_dcto_cl(OopIterateClosure* cl,
184 CardTable::PrecisionStyle precision,
185 HeapWord* boundary,
186 bool parallel);
187
188 // If "p" is in the space, returns the address of the start of the
189 // "block" that contains "p". We say "block" instead of "object" since
190 // some heaps may not pack objects densely; a chunk may either be an
191 // object or a non-object. If "p" is not in the space, return NULL.
192 virtual HeapWord* block_start_const(const void* p) const = 0;
193
194 // The non-const version may have benevolent side effects on the data
195 // structure supporting these calls, possibly speeding up future calls.
196 // The default implementation, however, is simply to call the const
197 // version.
198 virtual HeapWord* block_start(const void* p);
199
200 // Requires "addr" to be the start of a chunk, and returns its size.
201 // "addr + size" is required to be the start of a new chunk, or the end
202 // of the active area of the heap.
203 virtual size_t block_size(const HeapWord* addr) const = 0;
204
205 // Requires "addr" to be the start of a block, and returns "TRUE" iff
206 // the block is an object.
207 virtual bool block_is_obj(const HeapWord* addr) const = 0;
208
209 // Requires "addr" to be the start of a block, and returns "TRUE" iff
210 // the block is an object and the object is alive.
211 virtual bool obj_is_alive(const HeapWord* addr) const;
212
213 // Allocation (return NULL if full). Assumes the caller has established
214 // mutually exclusive access to the space.
215 virtual HeapWord* allocate(size_t word_size) = 0;
216
217 // Allocation (return NULL if full). Enforces mutual exclusion internally.
218 virtual HeapWord* par_allocate(size_t word_size) = 0;
219
220 #if INCLUDE_SERIALGC
221 // Mark-sweep-compact support: all spaces can update pointers to objects
222 // moving as a part of compaction.
223 virtual void adjust_pointers() = 0;
224 #endif
225
226 virtual void print() const;
227 virtual void print_on(outputStream* st) const;
228 virtual void print_short() const;
229 virtual void print_short_on(outputStream* st) const;
230
231
232 // Accessor for parallel sequential tasks.
233 SequentialSubTasksDone* par_seq_tasks() { return &_par_seq_tasks; }
234
235 // IF "this" is a ContiguousSpace, return it, else return NULL.
236 virtual ContiguousSpace* toContiguousSpace() {
237 return NULL;
238 }
239
240 // Debugging
241 virtual void verify() const = 0;
242 };
243
244 // A MemRegionClosure (ResourceObj) whose "do_MemRegion" function applies an
245 // OopClosure to (the addresses of) all the ref-containing fields that could
246 // be modified by virtue of the given MemRegion being dirty. (Note that
247 // because of the imprecise nature of the write barrier, this may iterate
248 // over oops beyond the region.)
249 // This base type for dirty card to oop closures handles memory regions
250 // in non-contiguous spaces with no boundaries, and should be sub-classed
251 // to support other space types. See ContiguousDCTOC for a sub-class
252 // that works with ContiguousSpaces.
253
254 class DirtyCardToOopClosure: public MemRegionClosureRO {
255 protected:
256 OopIterateClosure* _cl;
257 Space* _sp;
258 CardTable::PrecisionStyle _precision;
259 HeapWord* _boundary; // If non-NULL, process only non-NULL oops
260 // pointing below boundary.
261 HeapWord* _min_done; // ObjHeadPreciseArray precision requires
262 // a downwards traversal; this is the
263 // lowest location already done (or,
264 // alternatively, the lowest address that
265 // shouldn't be done again. NULL means infinity.)
266 NOT_PRODUCT(HeapWord* _last_bottom;)
267 NOT_PRODUCT(HeapWord* _last_explicit_min_done;)
268
269 // Get the actual top of the area on which the closure will
270 // operate, given where the top is assumed to be (the end of the
271 // memory region passed to do_MemRegion) and where the object
272 // at the top is assumed to start. For example, an object may
273 // start at the top but actually extend past the assumed top,
274 // in which case the top becomes the end of the object.
275 virtual HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj);
276
277 // Walk the given memory region from bottom to (actual) top
278 // looking for objects and applying the oop closure (_cl) to
279 // them. The base implementation of this treats the area as
280 // blocks, where a block may or may not be an object. Sub-
281 // classes should override this to provide more accurate
282 // or possibly more efficient walking.
283 virtual void walk_mem_region(MemRegion mr, HeapWord* bottom, HeapWord* top);
284
285 public:
286 DirtyCardToOopClosure(Space* sp, OopIterateClosure* cl,
287 CardTable::PrecisionStyle precision,
288 HeapWord* boundary) :
289 _cl(cl), _sp(sp), _precision(precision), _boundary(boundary),
290 _min_done(NULL) {
291 NOT_PRODUCT(_last_bottom = NULL);
292 NOT_PRODUCT(_last_explicit_min_done = NULL);
293 }
294
295 void do_MemRegion(MemRegion mr);
296
297 void set_min_done(HeapWord* min_done) {
298 _min_done = min_done;
299 NOT_PRODUCT(_last_explicit_min_done = _min_done);
300 }
301 #ifndef PRODUCT
302 void set_last_bottom(HeapWord* last_bottom) {
303 _last_bottom = last_bottom;
304 }
305 #endif
306 };
307
308 // A structure to represent a point at which objects are being copied
309 // during compaction.
310 class CompactPoint : public StackObj {
311 public:
312 Generation* gen;
313 CompactibleSpace* space;
314 HeapWord* threshold;
315
316 CompactPoint(Generation* g = NULL) :
317 gen(g), space(NULL), threshold(0) {}
318 };
319
320 // A space that supports compaction operations. This is usually, but not
321 // necessarily, a space that is normally contiguous. But, for example, a
322 // free-list-based space whose normal collection is a mark-sweep without
323 // compaction could still support compaction in full GC's.
324 //
325 // The compaction operations are implemented by the
326 // scan_and_{adjust_pointers,compact,forward} function templates.
327 // The following are, non-virtual, auxiliary functions used by these function templates:
328 // - scan_limit()
329 // - scanned_block_is_obj()
330 // - scanned_block_size()
331 // - adjust_obj_size()
332 // - obj_size()
333 // These functions are to be used exclusively by the scan_and_* function templates,
334 // and must be defined for all (non-abstract) subclasses of CompactibleSpace.
335 //
336 // NOTE: Any subclasses to CompactibleSpace wanting to change/define the behavior
337 // in any of the auxiliary functions must also override the corresponding
338 // prepare_for_compaction/adjust_pointers/compact functions using them.
339 // If not, such changes will not be used or have no effect on the compaction operations.
340 //
341 // This translates to the following dependencies:
342 // Overrides/definitions of
343 // - scan_limit
344 // - scanned_block_is_obj
345 // - scanned_block_size
346 // require override/definition of prepare_for_compaction().
347 // Similar dependencies exist between
348 // - adjust_obj_size and adjust_pointers()
349 // - obj_size and compact().
350 //
351 // Additionally, this also means that changes to block_size() or block_is_obj() that
352 // should be effective during the compaction operations must provide a corresponding
353 // definition of scanned_block_size/scanned_block_is_obj respectively.
354 class CompactibleSpace: public Space {
355 friend class VMStructs;
356 friend class CompactibleFreeListSpace;
357 private:
358 HeapWord* _compaction_top;
359 CompactibleSpace* _next_compaction_space;
360
361 // Auxiliary functions for scan_and_{forward,adjust_pointers,compact} support.
362 inline size_t adjust_obj_size(size_t size) const {
363 return size;
364 }
365
366 inline size_t obj_size(const HeapWord* addr) const;
367
368 template <class SpaceType>
369 static inline void verify_up_to_first_dead(SpaceType* space) NOT_DEBUG_RETURN;
370
371 template <class SpaceType>
372 static inline void clear_empty_region(SpaceType* space);
373
374 public:
375 CompactibleSpace() :
376 _compaction_top(NULL), _next_compaction_space(NULL) {}
377
378 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
379 virtual void clear(bool mangle_space);
380
381 // Used temporarily during a compaction phase to hold the value
382 // top should have when compaction is complete.
383 HeapWord* compaction_top() const { return _compaction_top; }
384
385 void set_compaction_top(HeapWord* value) {
386 assert(value == NULL || (value >= bottom() && value <= end()),
387 "should point inside space");
388 _compaction_top = value;
389 }
390
391 // Perform operations on the space needed after a compaction
392 // has been performed.
393 virtual void reset_after_compaction() = 0;
394
395 // Returns the next space (in the current generation) to be compacted in
396 // the global compaction order. Also is used to select the next
397 // space into which to compact.
398
399 virtual CompactibleSpace* next_compaction_space() const {
400 return _next_compaction_space;
401 }
402
403 void set_next_compaction_space(CompactibleSpace* csp) {
404 _next_compaction_space = csp;
405 }
406
407 #if INCLUDE_SERIALGC
408 // MarkSweep support phase2
409
410 // Start the process of compaction of the current space: compute
411 // post-compaction addresses, and insert forwarding pointers. The fields
412 // "cp->gen" and "cp->compaction_space" are the generation and space into
413 // which we are currently compacting. This call updates "cp" as necessary,
414 // and leaves the "compaction_top" of the final value of
415 // "cp->compaction_space" up-to-date. Offset tables may be updated in
416 // this phase as if the final copy had occurred; if so, "cp->threshold"
417 // indicates when the next such action should be taken.
418 virtual void prepare_for_compaction(CompactPoint* cp) = 0;
419 // MarkSweep support phase3
420 virtual void adjust_pointers();
421 // MarkSweep support phase4
422 virtual void compact();
423 #endif // INCLUDE_SERIALGC
424
425 // The maximum percentage of objects that can be dead in the compacted
426 // live part of a compacted space ("deadwood" support.)
427 virtual size_t allowed_dead_ratio() const { return 0; };
428
429 // Some contiguous spaces may maintain some data structures that should
430 // be updated whenever an allocation crosses a boundary. This function
431 // returns the first such boundary.
432 // (The default implementation returns the end of the space, so the
433 // boundary is never crossed.)
434 virtual HeapWord* initialize_threshold() { return end(); }
435
436 // "q" is an object of the given "size" that should be forwarded;
437 // "cp" names the generation ("gen") and containing "this" (which must
438 // also equal "cp->space"). "compact_top" is where in "this" the
439 // next object should be forwarded to. If there is room in "this" for
440 // the object, insert an appropriate forwarding pointer in "q".
441 // If not, go to the next compaction space (there must
442 // be one, since compaction must succeed -- we go to the first space of
443 // the previous generation if necessary, updating "cp"), reset compact_top
444 // and then forward. In either case, returns the new value of "compact_top".
445 // If the forwarding crosses "cp->threshold", invokes the "cross_threshold"
446 // function of the then-current compaction space, and updates "cp->threshold
447 // accordingly".
448 virtual HeapWord* forward(oop q, size_t size, CompactPoint* cp,
449 HeapWord* compact_top);
450
451 // Return a size with adjustments as required of the space.
452 virtual size_t adjust_object_size_v(size_t size) const { return size; }
453
454 void set_first_dead(HeapWord* value) { _first_dead = value; }
455 void set_end_of_live(HeapWord* value) { _end_of_live = value; }
456
457 protected:
458 // Used during compaction.
459 HeapWord* _first_dead;
460 HeapWord* _end_of_live;
461
462 // Minimum size of a free block.
463 virtual size_t minimum_free_block_size() const { return 0; }
464
465 // This the function is invoked when an allocation of an object covering
466 // "start" to "end occurs crosses the threshold; returns the next
467 // threshold. (The default implementation does nothing.)
468 virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* the_end) {
469 return end();
470 }
471
472 // Below are template functions for scan_and_* algorithms (avoiding virtual calls).
473 // The space argument should be a subclass of CompactibleSpace, implementing
474 // scan_limit(), scanned_block_is_obj(), and scanned_block_size(),
475 // and possibly also overriding obj_size(), and adjust_obj_size().
476 // These functions should avoid virtual calls whenever possible.
477
478 #if INCLUDE_SERIALGC
479 // Frequently calls adjust_obj_size().
480 template <class SpaceType>
481 static inline void scan_and_adjust_pointers(SpaceType* space);
482 #endif
483
484 // Frequently calls obj_size().
485 template <class SpaceType>
486 static inline void scan_and_compact(SpaceType* space);
487
488 // Frequently calls scanned_block_is_obj() and scanned_block_size().
489 // Requires the scan_limit() function.
490 template <class SpaceType>
491 static inline void scan_and_forward(SpaceType* space, CompactPoint* cp);
492 };
493
494 class GenSpaceMangler;
495
496 // A space in which the free area is contiguous. It therefore supports
497 // faster allocation, and compaction.
498 class ContiguousSpace: public CompactibleSpace {
499 friend class VMStructs;
500 // Allow scan_and_forward function to call (private) overrides for auxiliary functions on this class
501 template <typename SpaceType>
502 friend void CompactibleSpace::scan_and_forward(SpaceType* space, CompactPoint* cp);
503
504 private:
505 // Auxiliary functions for scan_and_forward support.
506 // See comments for CompactibleSpace for more information.
507 inline HeapWord* scan_limit() const {
508 return top();
509 }
510
511 inline bool scanned_block_is_obj(const HeapWord* addr) const {
512 return true; // Always true, since scan_limit is top
513 }
514
515 inline size_t scanned_block_size(const HeapWord* addr) const;
516
517 protected:
518 HeapWord* _top;
519 HeapWord* _concurrent_iteration_safe_limit;
520 // A helper for mangling the unused area of the space in debug builds.
521 GenSpaceMangler* _mangler;
522
523 GenSpaceMangler* mangler() { return _mangler; }
524
525 // Allocation helpers (return NULL if full).
526 inline HeapWord* allocate_impl(size_t word_size);
527 inline HeapWord* par_allocate_impl(size_t word_size);
528
529 public:
530 ContiguousSpace();
531 ~ContiguousSpace();
532
533 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
534 virtual void clear(bool mangle_space);
535
536 // Accessors
537 HeapWord* top() const { return _top; }
538 void set_top(HeapWord* value) { _top = value; }
539
540 void set_saved_mark() { _saved_mark_word = top(); }
541 void reset_saved_mark() { _saved_mark_word = bottom(); }
542
543 bool saved_mark_at_top() const { return saved_mark_word() == top(); }
544
545 // In debug mode mangle (write it with a particular bit
546 // pattern) the unused part of a space.
547
548 // Used to save the an address in a space for later use during mangling.
549 void set_top_for_allocations(HeapWord* v) PRODUCT_RETURN;
550 // Used to save the space's current top for later use during mangling.
551 void set_top_for_allocations() PRODUCT_RETURN;
552
553 // Mangle regions in the space from the current top up to the
554 // previously mangled part of the space.
555 void mangle_unused_area() PRODUCT_RETURN;
556 // Mangle [top, end)
557 void mangle_unused_area_complete() PRODUCT_RETURN;
558
559 // Do some sparse checking on the area that should have been mangled.
560 void check_mangled_unused_area(HeapWord* limit) PRODUCT_RETURN;
561 // Check the complete area that should have been mangled.
562 // This code may be NULL depending on the macro DEBUG_MANGLING.
563 void check_mangled_unused_area_complete() PRODUCT_RETURN;
564
565 // Size computations: sizes in bytes.
566 size_t capacity() const { return byte_size(bottom(), end()); }
567 size_t used() const { return byte_size(bottom(), top()); }
568 size_t free() const { return byte_size(top(), end()); }
569
570 virtual bool is_free_block(const HeapWord* p) const;
571
572 // In a contiguous space we have a more obvious bound on what parts
573 // contain objects.
574 MemRegion used_region() const { return MemRegion(bottom(), top()); }
575
576 // Allocation (return NULL if full)
577 virtual HeapWord* allocate(size_t word_size);
578 virtual HeapWord* par_allocate(size_t word_size);
579 HeapWord* allocate_aligned(size_t word_size);
580
581 // Iteration
582 void oop_iterate(OopIterateClosure* cl);
583 void object_iterate(ObjectClosure* blk);
584
585 // Iterate over as many initialized objects in the space as possible,
586 // calling "cl.do_object_careful" on each. Return NULL if all objects
587 // in the space (at the start of the iteration) were iterated over.
588 // Return an address indicating the extent of the iteration in the
589 // event that the iteration had to return because of finding an
590 // uninitialized object in the space, or if the closure "cl"
591 // signaled early termination.
592 HeapWord* object_iterate_careful(ObjectClosureCareful* cl);
593 HeapWord* concurrent_iteration_safe_limit() {
594 assert(_concurrent_iteration_safe_limit <= top(),
595 "_concurrent_iteration_safe_limit update missed");
596 return _concurrent_iteration_safe_limit;
597 }
598 // changes the safe limit, all objects from bottom() to the new
599 // limit should be properly initialized
600 void set_concurrent_iteration_safe_limit(HeapWord* new_limit) {
601 assert(new_limit <= top(), "uninitialized objects in the safe range");
602 _concurrent_iteration_safe_limit = new_limit;
603 }
604
605 // In support of parallel oop_iterate.
606 template <typename OopClosureType>
607 void par_oop_iterate(MemRegion mr, OopClosureType* blk);
608
609 // Compaction support
610 virtual void reset_after_compaction() {
611 assert(compaction_top() >= bottom() && compaction_top() <= end(), "should point inside space");
612 set_top(compaction_top());
613 // set new iteration safe limit
614 set_concurrent_iteration_safe_limit(compaction_top());
615 }
616
617 // Override.
618 DirtyCardToOopClosure* new_dcto_cl(OopIterateClosure* cl,
619 CardTable::PrecisionStyle precision,
620 HeapWord* boundary,
621 bool parallel);
622
623 // Apply "blk->do_oop" to the addresses of all reference fields in objects
624 // starting with the _saved_mark_word, which was noted during a generation's
625 // save_marks and is required to denote the head of an object.
626 // Fields in objects allocated by applications of the closure
627 // *are* included in the iteration.
628 // Updates _saved_mark_word to point to just after the last object
629 // iterated over.
630 template <typename OopClosureType>
631 void oop_since_save_marks_iterate(OopClosureType* blk);
632
633 // Same as object_iterate, but starting from "mark", which is required
634 // to denote the start of an object. Objects allocated by
635 // applications of the closure *are* included in the iteration.
636 virtual void object_iterate_from(HeapWord* mark, ObjectClosure* blk);
637
638 // Very inefficient implementation.
639 virtual HeapWord* block_start_const(const void* p) const;
640 size_t block_size(const HeapWord* p) const;
641 // If a block is in the allocated area, it is an object.
642 bool block_is_obj(const HeapWord* p) const { return p < top(); }
643
644 // Addresses for inlined allocation
645 HeapWord** top_addr() { return &_top; }
646 HeapWord** end_addr() { return &_end; }
647
648 #if INCLUDE_SERIALGC
649 // Overrides for more efficient compaction support.
650 void prepare_for_compaction(CompactPoint* cp);
651 #endif
652
653 virtual void print_on(outputStream* st) const;
654
655 // Checked dynamic downcasts.
656 virtual ContiguousSpace* toContiguousSpace() {
657 return this;
658 }
659
660 // Debugging
661 virtual void verify() const;
662
663 // Used to increase collection frequency. "factor" of 0 means entire
664 // space.
665 void allocate_temporary_filler(int factor);
666 };
667
668
669 // A dirty card to oop closure that does filtering.
670 // It knows how to filter out objects that are outside of the _boundary.
671 class FilteringDCTOC : public DirtyCardToOopClosure {
672 protected:
673 // Override.
674 void walk_mem_region(MemRegion mr,
675 HeapWord* bottom, HeapWord* top);
676
677 // Walk the given memory region, from bottom to top, applying
678 // the given oop closure to (possibly) all objects found. The
679 // given oop closure may or may not be the same as the oop
680 // closure with which this closure was created, as it may
681 // be a filtering closure which makes use of the _boundary.
682 // We offer two signatures, so the FilteringClosure static type is
683 // apparent.
684 virtual void walk_mem_region_with_cl(MemRegion mr,
685 HeapWord* bottom, HeapWord* top,
686 OopIterateClosure* cl) = 0;
687 virtual void walk_mem_region_with_cl(MemRegion mr,
688 HeapWord* bottom, HeapWord* top,
689 FilteringClosure* cl) = 0;
690
691 public:
692 FilteringDCTOC(Space* sp, OopIterateClosure* cl,
693 CardTable::PrecisionStyle precision,
694 HeapWord* boundary) :
695 DirtyCardToOopClosure(sp, cl, precision, boundary) {}
696 };
697
698 // A dirty card to oop closure for contiguous spaces
699 // (ContiguousSpace and sub-classes).
700 // It is a FilteringClosure, as defined above, and it knows:
701 //
702 // 1. That the actual top of any area in a memory region
703 // contained by the space is bounded by the end of the contiguous
704 // region of the space.
705 // 2. That the space is really made up of objects and not just
706 // blocks.
707
708 class ContiguousSpaceDCTOC : public FilteringDCTOC {
709 protected:
710 // Overrides.
711 HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj);
712
713 virtual void walk_mem_region_with_cl(MemRegion mr,
714 HeapWord* bottom, HeapWord* top,
715 OopIterateClosure* cl);
716 virtual void walk_mem_region_with_cl(MemRegion mr,
717 HeapWord* bottom, HeapWord* top,
718 FilteringClosure* cl);
719
720 public:
721 ContiguousSpaceDCTOC(ContiguousSpace* sp, OopIterateClosure* cl,
722 CardTable::PrecisionStyle precision,
723 HeapWord* boundary) :
724 FilteringDCTOC(sp, cl, precision, boundary)
725 {}
726 };
727
728 // A ContigSpace that Supports an efficient "block_start" operation via
729 // a BlockOffsetArray (whose BlockOffsetSharedArray may be shared with
730 // other spaces.) This is the abstract base class for old generation
731 // (tenured) spaces.
732
733 class OffsetTableContigSpace: public ContiguousSpace {
734 friend class VMStructs;
735 protected:
736 BlockOffsetArrayContigSpace _offsets;
737 Mutex _par_alloc_lock;
738
739 public:
740 // Constructor
741 OffsetTableContigSpace(BlockOffsetSharedArray* sharedOffsetArray,
742 MemRegion mr);
743
744 void set_bottom(HeapWord* value);
745 void set_end(HeapWord* value);
746
747 void clear(bool mangle_space);
748
749 inline HeapWord* block_start_const(const void* p) const;
750
751 // Add offset table update.
752 virtual inline HeapWord* allocate(size_t word_size);
753 inline HeapWord* par_allocate(size_t word_size);
754
755 // MarkSweep support phase3
756 virtual HeapWord* initialize_threshold();
757 virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* end);
758
759 virtual void print_on(outputStream* st) const;
760
761 // Debugging
762 void verify() const;
763 };
764
765
766 // Class TenuredSpace is used by TenuredGeneration
767
768 class TenuredSpace: public OffsetTableContigSpace {
769 friend class VMStructs;
770 protected:
771 // Mark sweep support
772 size_t allowed_dead_ratio() const;
773 public:
774 // Constructor
775 TenuredSpace(BlockOffsetSharedArray* sharedOffsetArray,
776 MemRegion mr) :
777 OffsetTableContigSpace(sharedOffsetArray, mr) {}
778 };
779 #endif // SHARE_GC_SHARED_SPACE_HPP