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/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/markOop.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(ExtendedOopClosure* 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 // Similar to object_iterate() except only iterates over
179 // objects whose internal references point to objects in the space.
180 virtual void safe_object_iterate(ObjectClosure* blk) = 0;
181
182 // Create and return a new dirty card to oop closure. Can be
183 // overridden to return the appropriate type of closure
184 // depending on the type of space in which the closure will
185 // operate. ResourceArea allocated.
186 virtual DirtyCardToOopClosure* new_dcto_cl(ExtendedOopClosure* cl,
187 CardTable::PrecisionStyle precision,
188 HeapWord* boundary,
189 bool parallel);
190
191 // If "p" is in the space, returns the address of the start of the
192 // "block" that contains "p". We say "block" instead of "object" since
193 // some heaps may not pack objects densely; a chunk may either be an
194 // object or a non-object. If "p" is not in the space, return NULL.
195 virtual HeapWord* block_start_const(const void* p) const = 0;
196
197 // The non-const version may have benevolent side effects on the data
198 // structure supporting these calls, possibly speeding up future calls.
199 // The default implementation, however, is simply to call the const
200 // version.
201 virtual HeapWord* block_start(const void* p);
202
203 // Requires "addr" to be the start of a chunk, and returns its size.
204 // "addr + size" is required to be the start of a new chunk, or the end
205 // of the active area of the heap.
206 virtual size_t block_size(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.
210 virtual bool block_is_obj(const HeapWord* addr) const = 0;
211
212 // Requires "addr" to be the start of a block, and returns "TRUE" iff
213 // the block is an object and the object is alive.
214 virtual bool obj_is_alive(const HeapWord* addr) const;
215
216 // Allocation (return NULL if full). Assumes the caller has established
217 // mutually exclusive access to the space.
218 virtual HeapWord* allocate(size_t word_size) = 0;
219
220 // Allocation (return NULL if full). Enforces mutual exclusion internally.
221 virtual HeapWord* par_allocate(size_t word_size) = 0;
222
223 #if INCLUDE_SERIALGC
224 // Mark-sweep-compact support: all spaces can update pointers to objects
225 // moving as a part of compaction.
226 virtual void adjust_pointers() = 0;
227 #endif
228
229 virtual void print() const;
230 virtual void print_on(outputStream* st) const;
231 virtual void print_short() const;
232 virtual void print_short_on(outputStream* st) const;
233
234
235 // Accessor for parallel sequential tasks.
236 SequentialSubTasksDone* par_seq_tasks() { return &_par_seq_tasks; }
237
238 // IF "this" is a ContiguousSpace, return it, else return NULL.
239 virtual ContiguousSpace* toContiguousSpace() {
240 return NULL;
241 }
242
243 // Debugging
244 virtual void verify() const = 0;
245 };
246
247 // A MemRegionClosure (ResourceObj) whose "do_MemRegion" function applies an
248 // OopClosure to (the addresses of) all the ref-containing fields that could
249 // be modified by virtue of the given MemRegion being dirty. (Note that
250 // because of the imprecise nature of the write barrier, this may iterate
251 // over oops beyond the region.)
252 // This base type for dirty card to oop closures handles memory regions
253 // in non-contiguous spaces with no boundaries, and should be sub-classed
254 // to support other space types. See ContiguousDCTOC for a sub-class
255 // that works with ContiguousSpaces.
256
257 class DirtyCardToOopClosure: public MemRegionClosureRO {
258 protected:
259 ExtendedOopClosure* _cl;
260 Space* _sp;
261 CardTable::PrecisionStyle _precision;
262 HeapWord* _boundary; // If non-NULL, process only non-NULL oops
263 // pointing below boundary.
264 HeapWord* _min_done; // ObjHeadPreciseArray precision requires
265 // a downwards traversal; this is the
266 // lowest location already done (or,
267 // alternatively, the lowest address that
268 // shouldn't be done again. NULL means infinity.)
269 NOT_PRODUCT(HeapWord* _last_bottom;)
270 NOT_PRODUCT(HeapWord* _last_explicit_min_done;)
271
272 // Get the actual top of the area on which the closure will
273 // operate, given where the top is assumed to be (the end of the
274 // memory region passed to do_MemRegion) and where the object
275 // at the top is assumed to start. For example, an object may
276 // start at the top but actually extend past the assumed top,
277 // in which case the top becomes the end of the object.
278 virtual HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj);
279
280 // Walk the given memory region from bottom to (actual) top
281 // looking for objects and applying the oop closure (_cl) to
282 // them. The base implementation of this treats the area as
283 // blocks, where a block may or may not be an object. Sub-
284 // classes should override this to provide more accurate
285 // or possibly more efficient walking.
286 virtual void walk_mem_region(MemRegion mr, HeapWord* bottom, HeapWord* top);
287
288 public:
289 DirtyCardToOopClosure(Space* sp, ExtendedOopClosure* cl,
290 CardTable::PrecisionStyle precision,
291 HeapWord* boundary) :
292 _sp(sp), _cl(cl), _precision(precision), _boundary(boundary),
293 _min_done(NULL) {
294 NOT_PRODUCT(_last_bottom = NULL);
295 NOT_PRODUCT(_last_explicit_min_done = NULL);
296 }
297
298 void do_MemRegion(MemRegion mr);
299
300 void set_min_done(HeapWord* min_done) {
301 _min_done = min_done;
302 NOT_PRODUCT(_last_explicit_min_done = _min_done);
303 }
304 #ifndef PRODUCT
305 void set_last_bottom(HeapWord* last_bottom) {
306 _last_bottom = last_bottom;
307 }
308 #endif
309 };
310
311 // A structure to represent a point at which objects are being copied
312 // during compaction.
313 class CompactPoint : public StackObj {
314 public:
315 Generation* gen;
316 CompactibleSpace* space;
317 HeapWord* threshold;
318
319 CompactPoint(Generation* g = NULL) :
320 gen(g), space(NULL), threshold(0) {}
321 };
322
323 // A space that supports compaction operations. This is usually, but not
324 // necessarily, a space that is normally contiguous. But, for example, a
325 // free-list-based space whose normal collection is a mark-sweep without
326 // compaction could still support compaction in full GC's.
327 //
328 // The compaction operations are implemented by the
329 // scan_and_{adjust_pointers,compact,forward} function templates.
330 // The following are, non-virtual, auxiliary functions used by these function templates:
331 // - scan_limit()
332 // - scanned_block_is_obj()
333 // - scanned_block_size()
334 // - adjust_obj_size()
335 // - obj_size()
336 // These functions are to be used exclusively by the scan_and_* function templates,
337 // and must be defined for all (non-abstract) subclasses of CompactibleSpace.
338 //
339 // NOTE: Any subclasses to CompactibleSpace wanting to change/define the behavior
340 // in any of the auxiliary functions must also override the corresponding
341 // prepare_for_compaction/adjust_pointers/compact functions using them.
342 // If not, such changes will not be used or have no effect on the compaction operations.
343 //
344 // This translates to the following dependencies:
345 // Overrides/definitions of
346 // - scan_limit
347 // - scanned_block_is_obj
348 // - scanned_block_size
349 // require override/definition of prepare_for_compaction().
350 // Similar dependencies exist between
351 // - adjust_obj_size and adjust_pointers()
352 // - obj_size and compact().
353 //
354 // Additionally, this also means that changes to block_size() or block_is_obj() that
355 // should be effective during the compaction operations must provide a corresponding
356 // definition of scanned_block_size/scanned_block_is_obj respectively.
357 class CompactibleSpace: public Space {
358 friend class VMStructs;
359 friend class CompactibleFreeListSpace;
360 private:
361 HeapWord* _compaction_top;
362 CompactibleSpace* _next_compaction_space;
363
364 // Auxiliary functions for scan_and_{forward,adjust_pointers,compact} support.
365 inline size_t adjust_obj_size(size_t size) const {
366 return size;
367 }
368
369 inline size_t obj_size(const HeapWord* addr) const;
370
371 template <class SpaceType>
372 static inline void verify_up_to_first_dead(SpaceType* space) NOT_DEBUG_RETURN;
373
374 template <class SpaceType>
375 static inline void clear_empty_region(SpaceType* space);
376
377 public:
378 CompactibleSpace() :
379 _compaction_top(NULL), _next_compaction_space(NULL) {}
380
381 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
382 virtual void clear(bool mangle_space);
383
384 // Used temporarily during a compaction phase to hold the value
385 // top should have when compaction is complete.
386 HeapWord* compaction_top() const { return _compaction_top; }
387
388 void set_compaction_top(HeapWord* value) {
389 assert(value == NULL || (value >= bottom() && value <= end()),
390 "should point inside space");
391 _compaction_top = value;
392 }
393
394 // Perform operations on the space needed after a compaction
395 // has been performed.
396 virtual void reset_after_compaction() = 0;
397
398 // Returns the next space (in the current generation) to be compacted in
399 // the global compaction order. Also is used to select the next
400 // space into which to compact.
401
402 virtual CompactibleSpace* next_compaction_space() const {
403 return _next_compaction_space;
404 }
405
406 void set_next_compaction_space(CompactibleSpace* csp) {
407 _next_compaction_space = csp;
408 }
409
410 #if INCLUDE_SERIALGC
411 // MarkSweep support phase2
412
413 // Start the process of compaction of the current space: compute
414 // post-compaction addresses, and insert forwarding pointers. The fields
415 // "cp->gen" and "cp->compaction_space" are the generation and space into
416 // which we are currently compacting. This call updates "cp" as necessary,
417 // and leaves the "compaction_top" of the final value of
418 // "cp->compaction_space" up-to-date. Offset tables may be updated in
419 // this phase as if the final copy had occurred; if so, "cp->threshold"
420 // indicates when the next such action should be taken.
421 virtual void prepare_for_compaction(CompactPoint* cp) = 0;
422 // MarkSweep support phase3
423 virtual void adjust_pointers();
424 // MarkSweep support phase4
425 virtual void compact();
426 #endif // INCLUDE_SERIALGC
427
428 // The maximum percentage of objects that can be dead in the compacted
429 // live part of a compacted space ("deadwood" support.)
430 virtual size_t allowed_dead_ratio() const { return 0; };
431
432 // Some contiguous spaces may maintain some data structures that should
433 // be updated whenever an allocation crosses a boundary. This function
434 // returns the first such boundary.
435 // (The default implementation returns the end of the space, so the
436 // boundary is never crossed.)
437 virtual HeapWord* initialize_threshold() { return end(); }
438
439 // "q" is an object of the given "size" that should be forwarded;
440 // "cp" names the generation ("gen") and containing "this" (which must
441 // also equal "cp->space"). "compact_top" is where in "this" the
442 // next object should be forwarded to. If there is room in "this" for
443 // the object, insert an appropriate forwarding pointer in "q".
444 // If not, go to the next compaction space (there must
445 // be one, since compaction must succeed -- we go to the first space of
446 // the previous generation if necessary, updating "cp"), reset compact_top
447 // and then forward. In either case, returns the new value of "compact_top".
448 // If the forwarding crosses "cp->threshold", invokes the "cross_threshold"
449 // function of the then-current compaction space, and updates "cp->threshold
450 // accordingly".
451 virtual HeapWord* forward(oop q, size_t size, CompactPoint* cp,
452 HeapWord* compact_top);
453
454 // Return a size with adjustments as required of the space.
455 virtual size_t adjust_object_size_v(size_t size) const { return size; }
456
457 void set_first_dead(HeapWord* value) { _first_dead = value; }
458 void set_end_of_live(HeapWord* value) { _end_of_live = value; }
459
460 protected:
461 // Used during compaction.
462 HeapWord* _first_dead;
463 HeapWord* _end_of_live;
464
465 // Minimum size of a free block.
466 virtual size_t minimum_free_block_size() const { return 0; }
467
468 // This the function is invoked when an allocation of an object covering
469 // "start" to "end occurs crosses the threshold; returns the next
470 // threshold. (The default implementation does nothing.)
471 virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* the_end) {
472 return end();
473 }
474
475 // Below are template functions for scan_and_* algorithms (avoiding virtual calls).
476 // The space argument should be a subclass of CompactibleSpace, implementing
477 // scan_limit(), scanned_block_is_obj(), and scanned_block_size(),
478 // and possibly also overriding obj_size(), and adjust_obj_size().
479 // These functions should avoid virtual calls whenever possible.
480
481 #if INCLUDE_SERIALGC
482 // Frequently calls adjust_obj_size().
483 template <class SpaceType>
484 static inline void scan_and_adjust_pointers(SpaceType* space);
485 #endif
486
487 // Frequently calls obj_size().
488 template <class SpaceType>
489 static inline void scan_and_compact(SpaceType* space);
490
491 // Frequently calls scanned_block_is_obj() and scanned_block_size().
492 // Requires the scan_limit() function.
493 template <class SpaceType>
494 static inline void scan_and_forward(SpaceType* space, CompactPoint* cp);
495 };
496
497 class GenSpaceMangler;
498
499 // A space in which the free area is contiguous. It therefore supports
500 // faster allocation, and compaction.
501 class ContiguousSpace: public CompactibleSpace {
502 friend class VMStructs;
503 // Allow scan_and_forward function to call (private) overrides for auxiliary functions on this class
504 template <typename SpaceType>
505 friend void CompactibleSpace::scan_and_forward(SpaceType* space, CompactPoint* cp);
506
507 private:
508 // Auxiliary functions for scan_and_forward support.
509 // See comments for CompactibleSpace for more information.
510 inline HeapWord* scan_limit() const {
511 return top();
512 }
513
514 inline bool scanned_block_is_obj(const HeapWord* addr) const {
515 return true; // Always true, since scan_limit is top
516 }
517
518 inline size_t scanned_block_size(const HeapWord* addr) const;
519
520 protected:
521 HeapWord* _top;
522 HeapWord* _concurrent_iteration_safe_limit;
523 // A helper for mangling the unused area of the space in debug builds.
524 GenSpaceMangler* _mangler;
525
526 GenSpaceMangler* mangler() { return _mangler; }
527
528 // Allocation helpers (return NULL if full).
529 inline HeapWord* allocate_impl(size_t word_size);
530 inline HeapWord* par_allocate_impl(size_t word_size);
531
532 public:
533 ContiguousSpace();
534 ~ContiguousSpace();
535
536 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
537 virtual void clear(bool mangle_space);
538
539 // Accessors
540 HeapWord* top() const { return _top; }
541 void set_top(HeapWord* value) { _top = value; }
542
543 void set_saved_mark() { _saved_mark_word = top(); }
544 void reset_saved_mark() { _saved_mark_word = bottom(); }
545
546 bool saved_mark_at_top() const { return saved_mark_word() == top(); }
547
548 // In debug mode mangle (write it with a particular bit
549 // pattern) the unused part of a space.
550
551 // Used to save the an address in a space for later use during mangling.
552 void set_top_for_allocations(HeapWord* v) PRODUCT_RETURN;
553 // Used to save the space's current top for later use during mangling.
554 void set_top_for_allocations() PRODUCT_RETURN;
555
556 // Mangle regions in the space from the current top up to the
557 // previously mangled part of the space.
558 void mangle_unused_area() PRODUCT_RETURN;
559 // Mangle [top, end)
560 void mangle_unused_area_complete() PRODUCT_RETURN;
561
562 // Do some sparse checking on the area that should have been mangled.
563 void check_mangled_unused_area(HeapWord* limit) PRODUCT_RETURN;
564 // Check the complete area that should have been mangled.
565 // This code may be NULL depending on the macro DEBUG_MANGLING.
566 void check_mangled_unused_area_complete() PRODUCT_RETURN;
567
568 // Size computations: sizes in bytes.
569 size_t capacity() const { return byte_size(bottom(), end()); }
570 size_t used() const { return byte_size(bottom(), top()); }
571 size_t free() const { return byte_size(top(), end()); }
572
573 virtual bool is_free_block(const HeapWord* p) const;
574
575 // In a contiguous space we have a more obvious bound on what parts
576 // contain objects.
577 MemRegion used_region() const { return MemRegion(bottom(), top()); }
578
579 // Allocation (return NULL if full)
580 virtual HeapWord* allocate(size_t word_size);
581 virtual HeapWord* par_allocate(size_t word_size);
582 HeapWord* allocate_aligned(size_t word_size);
583
584 // Iteration
585 void oop_iterate(ExtendedOopClosure* cl);
586 void object_iterate(ObjectClosure* blk);
587 // For contiguous spaces this method will iterate safely over objects
588 // in the space (i.e., between bottom and top) when at a safepoint.
589 void safe_object_iterate(ObjectClosure* blk);
590
591 // Iterate over as many initialized objects in the space as possible,
592 // calling "cl.do_object_careful" on each. Return NULL if all objects
593 // in the space (at the start of the iteration) were iterated over.
594 // Return an address indicating the extent of the iteration in the
595 // event that the iteration had to return because of finding an
596 // uninitialized object in the space, or if the closure "cl"
597 // signaled early termination.
598 HeapWord* object_iterate_careful(ObjectClosureCareful* cl);
599 HeapWord* concurrent_iteration_safe_limit() {
600 assert(_concurrent_iteration_safe_limit <= top(),
601 "_concurrent_iteration_safe_limit update missed");
602 return _concurrent_iteration_safe_limit;
603 }
604 // changes the safe limit, all objects from bottom() to the new
605 // limit should be properly initialized
606 void set_concurrent_iteration_safe_limit(HeapWord* new_limit) {
607 assert(new_limit <= top(), "uninitialized objects in the safe range");
608 _concurrent_iteration_safe_limit = new_limit;
609 }
610
611
612 #if INCLUDE_CMSGC
613 // In support of parallel oop_iterate.
614 #define ContigSpace_PAR_OOP_ITERATE_DECL(OopClosureType, nv_suffix) \
615 void par_oop_iterate(MemRegion mr, OopClosureType* blk);
616
617 ALL_PAR_OOP_ITERATE_CLOSURES(ContigSpace_PAR_OOP_ITERATE_DECL)
618 #undef ContigSpace_PAR_OOP_ITERATE_DECL
619 #endif // INCLUDE_CMSGC
620
621 // Compaction support
622 virtual void reset_after_compaction() {
623 assert(compaction_top() >= bottom() && compaction_top() <= end(), "should point inside space");
624 set_top(compaction_top());
625 // set new iteration safe limit
626 set_concurrent_iteration_safe_limit(compaction_top());
627 }
628
629 // Override.
630 DirtyCardToOopClosure* new_dcto_cl(ExtendedOopClosure* cl,
631 CardTable::PrecisionStyle precision,
632 HeapWord* boundary,
633 bool parallel);
634
635 // Apply "blk->do_oop" to the addresses of all reference fields in objects
636 // starting with the _saved_mark_word, which was noted during a generation's
637 // save_marks and is required to denote the head of an object.
638 // Fields in objects allocated by applications of the closure
639 // *are* included in the iteration.
640 // Updates _saved_mark_word to point to just after the last object
641 // iterated over.
642 template <typename OopClosureType>
643 void oop_since_save_marks_iterate(OopClosureType* blk);
644
645 // Same as object_iterate, but starting from "mark", which is required
646 // to denote the start of an object. Objects allocated by
647 // applications of the closure *are* included in the iteration.
648 virtual void object_iterate_from(HeapWord* mark, ObjectClosure* blk);
649
650 // Very inefficient implementation.
651 virtual HeapWord* block_start_const(const void* p) const;
652 size_t block_size(const HeapWord* p) const;
653 // If a block is in the allocated area, it is an object.
654 bool block_is_obj(const HeapWord* p) const { return p < top(); }
655
656 // Addresses for inlined allocation
657 HeapWord** top_addr() { return &_top; }
658 HeapWord** end_addr() { return &_end; }
659
660 #if INCLUDE_SERIALGC
661 // Overrides for more efficient compaction support.
662 void prepare_for_compaction(CompactPoint* cp);
663 #endif
664
665 virtual void print_on(outputStream* st) const;
666
667 // Checked dynamic downcasts.
668 virtual ContiguousSpace* toContiguousSpace() {
669 return this;
670 }
671
672 // Debugging
673 virtual void verify() const;
674
675 // Used to increase collection frequency. "factor" of 0 means entire
676 // space.
677 void allocate_temporary_filler(int factor);
678 };
679
680
681 // A dirty card to oop closure that does filtering.
682 // It knows how to filter out objects that are outside of the _boundary.
683 class FilteringDCTOC : public DirtyCardToOopClosure {
684 protected:
685 // Override.
686 void walk_mem_region(MemRegion mr,
687 HeapWord* bottom, HeapWord* top);
688
689 // Walk the given memory region, from bottom to top, applying
690 // the given oop closure to (possibly) all objects found. The
691 // given oop closure may or may not be the same as the oop
692 // closure with which this closure was created, as it may
693 // be a filtering closure which makes use of the _boundary.
694 // We offer two signatures, so the FilteringClosure static type is
695 // apparent.
696 virtual void walk_mem_region_with_cl(MemRegion mr,
697 HeapWord* bottom, HeapWord* top,
698 ExtendedOopClosure* cl) = 0;
699 virtual void walk_mem_region_with_cl(MemRegion mr,
700 HeapWord* bottom, HeapWord* top,
701 FilteringClosure* cl) = 0;
702
703 public:
704 FilteringDCTOC(Space* sp, ExtendedOopClosure* cl,
705 CardTable::PrecisionStyle precision,
706 HeapWord* boundary) :
707 DirtyCardToOopClosure(sp, cl, precision, boundary) {}
708 };
709
710 // A dirty card to oop closure for contiguous spaces
711 // (ContiguousSpace and sub-classes).
712 // It is a FilteringClosure, as defined above, and it knows:
713 //
714 // 1. That the actual top of any area in a memory region
715 // contained by the space is bounded by the end of the contiguous
716 // region of the space.
717 // 2. That the space is really made up of objects and not just
718 // blocks.
719
720 class ContiguousSpaceDCTOC : public FilteringDCTOC {
721 protected:
722 // Overrides.
723 HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj);
724
725 virtual void walk_mem_region_with_cl(MemRegion mr,
726 HeapWord* bottom, HeapWord* top,
727 ExtendedOopClosure* cl);
728 virtual void walk_mem_region_with_cl(MemRegion mr,
729 HeapWord* bottom, HeapWord* top,
730 FilteringClosure* cl);
731
732 public:
733 ContiguousSpaceDCTOC(ContiguousSpace* sp, ExtendedOopClosure* cl,
734 CardTable::PrecisionStyle precision,
735 HeapWord* boundary) :
736 FilteringDCTOC(sp, cl, precision, boundary)
737 {}
738 };
739
740 // A ContigSpace that Supports an efficient "block_start" operation via
741 // a BlockOffsetArray (whose BlockOffsetSharedArray may be shared with
742 // other spaces.) This is the abstract base class for old generation
743 // (tenured) spaces.
744
745 class OffsetTableContigSpace: public ContiguousSpace {
746 friend class VMStructs;
747 protected:
748 BlockOffsetArrayContigSpace _offsets;
749 Mutex _par_alloc_lock;
750
751 public:
752 // Constructor
753 OffsetTableContigSpace(BlockOffsetSharedArray* sharedOffsetArray,
754 MemRegion mr);
755
756 void set_bottom(HeapWord* value);
757 void set_end(HeapWord* value);
758
759 void clear(bool mangle_space);
760
761 inline HeapWord* block_start_const(const void* p) const;
762
763 // Add offset table update.
764 virtual inline HeapWord* allocate(size_t word_size);
765 inline HeapWord* par_allocate(size_t word_size);
766
767 // MarkSweep support phase3
768 virtual HeapWord* initialize_threshold();
769 virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* end);
770
771 virtual void print_on(outputStream* st) const;
772
773 // Debugging
774 void verify() const;
775 };
776
777
778 // Class TenuredSpace is used by TenuredGeneration
779
780 class TenuredSpace: public OffsetTableContigSpace {
781 friend class VMStructs;
782 protected:
783 // Mark sweep support
784 size_t allowed_dead_ratio() const;
785 public:
786 // Constructor
787 TenuredSpace(BlockOffsetSharedArray* sharedOffsetArray,
788 MemRegion mr) :
789 OffsetTableContigSpace(sharedOffsetArray, mr) {}
790 };
791 #endif // SHARE_VM_GC_SHARED_SPACE_HPP