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_MEMORY_SPACE_HPP
26 #define SHARE_VM_MEMORY_SPACE_HPP
27
28 #include "memory/allocation.hpp"
29 #include "memory/blockOffsetTable.hpp"
30 #include "memory/cardTableModRefBS.hpp"
31 #include "memory/iterator.hpp"
32 #include "memory/memRegion.hpp"
33 #include "memory/watermark.hpp"
34 #include "oops/markOop.hpp"
35 #include "runtime/mutexLocker.hpp"
36 #include "utilities/macros.hpp"
37 #include "utilities/workgroup.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 GenRemSet;
52 class CardTableRS;
53 class DirtyCardToOopClosure;
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 // A sequential tasks done structure. This supports
74 // parallel GC, where we have threads dynamically
75 // claiming sub-tasks from a larger parallel task.
76 SequentialSubTasksDone _par_seq_tasks;
77
78 Space():
79 _bottom(NULL), _end(NULL) { }
80
81 public:
82 // Accessors
83 HeapWord* bottom() const { return _bottom; }
84 HeapWord* end() const { return _end; }
85 virtual void set_bottom(HeapWord* value) { _bottom = value; }
86 virtual void set_end(HeapWord* value) { _end = value; }
87
88 virtual HeapWord* saved_mark_word() const { return _saved_mark_word; }
89
90 void set_saved_mark_word(HeapWord* p) { _saved_mark_word = p; }
91
92 // Returns true if this object has been allocated since a
93 // generation's "save_marks" call.
94 virtual bool obj_allocated_since_save_marks(const oop obj) const {
95 return (HeapWord*)obj >= saved_mark_word();
96 }
97
98 virtual MemRegionClosure* preconsumptionDirtyCardClosure() const {
99 return NULL;
100 }
101
102 // Returns a subregion of the space containing only the allocated objects in
103 // the space.
104 virtual MemRegion used_region() const = 0;
105
106 // Returns a region that is guaranteed to contain (at least) all objects
107 // allocated at the time of the last call to "save_marks". If the space
108 // initializes its DirtyCardToOopClosure's specifying the "contig" option
109 // (that is, if the space is contiguous), then this region must contain only
110 // such objects: the memregion will be from the bottom of the region to the
111 // saved mark. Otherwise, the "obj_allocated_since_save_marks" method of
112 // the space must distinguish between objects in the region allocated before
113 // and after the call to save marks.
114 MemRegion used_region_at_save_marks() const {
115 return MemRegion(bottom(), saved_mark_word());
116 }
117
118 // Initialization.
119 // "initialize" should be called once on a space, before it is used for
120 // any purpose. The "mr" arguments gives the bounds of the space, and
121 // the "clear_space" argument should be true unless the memory in "mr" is
122 // known to be zeroed.
123 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
124
125 // The "clear" method must be called on a region that may have
126 // had allocation performed in it, but is now to be considered empty.
127 virtual void clear(bool mangle_space);
128
129 // For detecting GC bugs. Should only be called at GC boundaries, since
130 // some unused space may be used as scratch space during GC's.
131 // We also call this when expanding a space to satisfy an allocation
132 // request. See bug #4668531
133 virtual void mangle_unused_area() = 0;
134 virtual void mangle_unused_area_complete() = 0;
135
136 // Testers
137 bool is_empty() const { return used() == 0; }
138 bool not_empty() const { return used() > 0; }
139
140 // Returns true iff the given the space contains the
141 // given address as part of an allocated object. For
142 // certain kinds of spaces, this might be a potentially
143 // expensive operation. To prevent performance problems
144 // on account of its inadvertent use in product jvm's,
145 // we restrict its use to assertion checks only.
146 bool is_in(const void* p) const {
147 return used_region().contains(p);
148 }
149
150 // Returns true iff the given reserved memory of the space contains the
151 // given address.
152 bool is_in_reserved(const void* p) const { return _bottom <= p && p < _end; }
153
154 // Returns true iff the given block is not allocated.
155 virtual bool is_free_block(const HeapWord* p) const = 0;
156
157 // Test whether p is double-aligned
158 static bool is_aligned(void* p) {
159 return ((intptr_t)p & (sizeof(double)-1)) == 0;
160 }
161
162 // Size computations. Sizes are in bytes.
163 size_t capacity() const { return byte_size(bottom(), end()); }
164 virtual size_t used() const = 0;
165 virtual size_t free() const = 0;
166
167 // Iterate over all the ref-containing fields of all objects in the
168 // space, calling "cl.do_oop" on each. Fields in objects allocated by
169 // applications of the closure are not included in the iteration.
170 virtual void oop_iterate(ExtendedOopClosure* cl);
171
172 // Iterate over all objects in the space, calling "cl.do_object" on
173 // each. Objects allocated by applications of the closure are not
174 // included in the iteration.
175 virtual void object_iterate(ObjectClosure* blk) = 0;
176 // Similar to object_iterate() except only iterates over
177 // objects whose internal references point to objects in the space.
178 virtual void safe_object_iterate(ObjectClosure* blk) = 0;
179
180 // Create and return a new dirty card to oop closure. Can be
181 // overridden to return the appropriate type of closure
182 // depending on the type of space in which the closure will
183 // operate. ResourceArea allocated.
184 virtual DirtyCardToOopClosure* new_dcto_cl(ExtendedOopClosure* cl,
185 CardTableModRefBS::PrecisionStyle precision,
186 HeapWord* boundary = NULL);
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 inline 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 // Mark-sweep-compact support: all spaces can update pointers to objects
221 // moving as a part of compaction.
222 virtual void adjust_pointers() = 0;
223
224 // PrintHeapAtGC support
225 virtual void print() const;
226 virtual void print_on(outputStream* st) const;
227 virtual void print_short() const;
228 virtual void print_short_on(outputStream* st) const;
229
230
231 // Accessor for parallel sequential tasks.
232 SequentialSubTasksDone* par_seq_tasks() { return &_par_seq_tasks; }
233
234 // IF "this" is a ContiguousSpace, return it, else return NULL.
235 virtual ContiguousSpace* toContiguousSpace() {
236 return NULL;
237 }
238
239 // Debugging
240 virtual void verify() const = 0;
241 };
242
243 // A MemRegionClosure (ResourceObj) whose "do_MemRegion" function applies an
244 // OopClosure to (the addresses of) all the ref-containing fields that could
245 // be modified by virtue of the given MemRegion being dirty. (Note that
246 // because of the imprecise nature of the write barrier, this may iterate
247 // over oops beyond the region.)
248 // This base type for dirty card to oop closures handles memory regions
249 // in non-contiguous spaces with no boundaries, and should be sub-classed
250 // to support other space types. See ContiguousDCTOC for a sub-class
251 // that works with ContiguousSpaces.
252
253 class DirtyCardToOopClosure: public MemRegionClosureRO {
254 protected:
255 ExtendedOopClosure* _cl;
256 Space* _sp;
257 CardTableModRefBS::PrecisionStyle _precision;
258 HeapWord* _boundary; // If non-NULL, process only non-NULL oops
259 // pointing below boundary.
260 HeapWord* _min_done; // ObjHeadPreciseArray precision requires
261 // a downwards traversal; this is the
262 // lowest location already done (or,
263 // alternatively, the lowest address that
264 // shouldn't be done again. NULL means infinity.)
265 NOT_PRODUCT(HeapWord* _last_bottom;)
266 NOT_PRODUCT(HeapWord* _last_explicit_min_done;)
267
268 // Get the actual top of the area on which the closure will
269 // operate, given where the top is assumed to be (the end of the
270 // memory region passed to do_MemRegion) and where the object
271 // at the top is assumed to start. For example, an object may
272 // start at the top but actually extend past the assumed top,
273 // in which case the top becomes the end of the object.
274 virtual HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj);
275
276 // Walk the given memory region from bottom to (actual) top
277 // looking for objects and applying the oop closure (_cl) to
278 // them. The base implementation of this treats the area as
279 // blocks, where a block may or may not be an object. Sub-
280 // classes should override this to provide more accurate
281 // or possibly more efficient walking.
282 virtual void walk_mem_region(MemRegion mr, HeapWord* bottom, HeapWord* top);
283
284 public:
285 DirtyCardToOopClosure(Space* sp, ExtendedOopClosure* cl,
286 CardTableModRefBS::PrecisionStyle precision,
287 HeapWord* boundary) :
288 _sp(sp), _cl(cl), _precision(precision), _boundary(boundary),
289 _min_done(NULL) {
290 NOT_PRODUCT(_last_bottom = NULL);
291 NOT_PRODUCT(_last_explicit_min_done = NULL);
292 }
293
294 void do_MemRegion(MemRegion mr);
295
296 void set_min_done(HeapWord* min_done) {
297 _min_done = min_done;
298 NOT_PRODUCT(_last_explicit_min_done = _min_done);
299 }
300 #ifndef PRODUCT
301 void set_last_bottom(HeapWord* last_bottom) {
302 _last_bottom = last_bottom;
303 }
304 #endif
305 };
306
307 // A structure to represent a point at which objects are being copied
308 // during compaction.
309 class CompactPoint : public StackObj {
310 public:
311 Generation* gen;
312 CompactibleSpace* space;
313 HeapWord* threshold;
314
315 CompactPoint(Generation* g = NULL) :
316 gen(g), space(NULL), threshold(0) {}
317 };
318
319 // A space that supports compaction operations. This is usually, but not
320 // necessarily, a space that is normally contiguous. But, for example, a
321 // free-list-based space whose normal collection is a mark-sweep without
322 // compaction could still support compaction in full GC's.
323 //
324 // The compaction operations are implemented by the
325 // scan_and_{adjust_pointers,compact,forward} function templates.
326 // The following are, non-virtual, auxiliary functions used by these function templates:
327 // - scan_limit()
328 // - scanned_block_is_obj()
329 // - scanned_block_size()
330 // - adjust_obj_size()
331 // - obj_size()
332 // These functions are to be used exclusively by the scan_and_* function templates,
333 // and must be defined for all (non-abstract) subclasses of CompactibleSpace.
334 //
335 // NOTE: Any subclasses to CompactibleSpace wanting to change/define the behavior
336 // in any of the auxiliary functions must also override the corresponding
337 // prepare_for_compaction/adjust_pointers/compact functions using them.
338 // If not, such changes will not be used or have no effect on the compaction operations.
339 //
340 // This translates to the following dependencies:
341 // Overrides/definitions of
342 // - scan_limit
343 // - scanned_block_is_obj
344 // - scanned_block_size
345 // require override/definition of prepare_for_compaction().
346 // Similar dependencies exist between
347 // - adjust_obj_size and adjust_pointers()
348 // - obj_size and compact().
349 //
350 // Additionally, this also means that changes to block_size() or block_is_obj() that
351 // should be effective during the compaction operations must provide a corresponding
352 // definition of scanned_block_size/scanned_block_is_obj respectively.
353 class CompactibleSpace: public Space {
354 friend class VMStructs;
355 friend class CompactibleFreeListSpace;
356 private:
357 HeapWord* _compaction_top;
358 CompactibleSpace* _next_compaction_space;
359
360 // Auxiliary functions for scan_and_{forward,adjust_pointers,compact} support.
361 inline size_t adjust_obj_size(size_t size) const {
362 return size;
363 }
364
365 inline size_t obj_size(const HeapWord* addr) const {
366 return oop(addr)->size();
367 }
368
369 public:
370 CompactibleSpace() :
371 _compaction_top(NULL), _next_compaction_space(NULL) {}
372
373 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
374 virtual void clear(bool mangle_space);
375
376 // Used temporarily during a compaction phase to hold the value
377 // top should have when compaction is complete.
378 HeapWord* compaction_top() const { return _compaction_top; }
379
380 void set_compaction_top(HeapWord* value) {
381 assert(value == NULL || (value >= bottom() && value <= end()),
382 "should point inside space");
383 _compaction_top = value;
384 }
385
386 // Perform operations on the space needed after a compaction
387 // has been performed.
388 virtual void reset_after_compaction() = 0;
389
390 // Returns the next space (in the current generation) to be compacted in
391 // the global compaction order. Also is used to select the next
392 // space into which to compact.
393
394 virtual CompactibleSpace* next_compaction_space() const {
395 return _next_compaction_space;
396 }
397
398 void set_next_compaction_space(CompactibleSpace* csp) {
399 _next_compaction_space = csp;
400 }
401
402 // MarkSweep support phase2
403
404 // Start the process of compaction of the current space: compute
405 // post-compaction addresses, and insert forwarding pointers. The fields
406 // "cp->gen" and "cp->compaction_space" are the generation and space into
407 // which we are currently compacting. This call updates "cp" as necessary,
408 // and leaves the "compaction_top" of the final value of
409 // "cp->compaction_space" up-to-date. Offset tables may be updated in
410 // this phase as if the final copy had occurred; if so, "cp->threshold"
411 // indicates when the next such action should be taken.
412 virtual void prepare_for_compaction(CompactPoint* cp) = 0;
413 // MarkSweep support phase3
414 virtual void adjust_pointers();
415 // MarkSweep support phase4
416 virtual void compact();
417
418 // The maximum percentage of objects that can be dead in the compacted
419 // live part of a compacted space ("deadwood" support.)
420 virtual size_t allowed_dead_ratio() const { return 0; };
421
422 // Some contiguous spaces may maintain some data structures that should
423 // be updated whenever an allocation crosses a boundary. This function
424 // returns the first such boundary.
425 // (The default implementation returns the end of the space, so the
426 // boundary is never crossed.)
427 virtual HeapWord* initialize_threshold() { return end(); }
428
429 // "q" is an object of the given "size" that should be forwarded;
430 // "cp" names the generation ("gen") and containing "this" (which must
431 // also equal "cp->space"). "compact_top" is where in "this" the
432 // next object should be forwarded to. If there is room in "this" for
433 // the object, insert an appropriate forwarding pointer in "q".
434 // If not, go to the next compaction space (there must
435 // be one, since compaction must succeed -- we go to the first space of
436 // the previous generation if necessary, updating "cp"), reset compact_top
437 // and then forward. In either case, returns the new value of "compact_top".
438 // If the forwarding crosses "cp->threshold", invokes the "cross_threshold"
439 // function of the then-current compaction space, and updates "cp->threshold
440 // accordingly".
441 virtual HeapWord* forward(oop q, size_t size, CompactPoint* cp,
442 HeapWord* compact_top);
443
444 // Return a size with adjustments as required of the space.
445 virtual size_t adjust_object_size_v(size_t size) const { return size; }
446
447 protected:
448 // Used during compaction.
449 HeapWord* _first_dead;
450 HeapWord* _end_of_live;
451
452 // Minimum size of a free block.
453 virtual size_t minimum_free_block_size() const { return 0; }
454
455 // This the function is invoked when an allocation of an object covering
456 // "start" to "end occurs crosses the threshold; returns the next
457 // threshold. (The default implementation does nothing.)
458 virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* the_end) {
459 return end();
460 }
461
462 // Requires "allowed_deadspace_words > 0", that "q" is the start of a
463 // free block of the given "word_len", and that "q", were it an object,
464 // would not move if forwarded. If the size allows, fill the free
465 // block with an object, to prevent excessive compaction. Returns "true"
466 // iff the free region was made deadspace, and modifies
467 // "allowed_deadspace_words" to reflect the number of available deadspace
468 // words remaining after this operation.
469 bool insert_deadspace(size_t& allowed_deadspace_words, HeapWord* q,
470 size_t word_len);
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 // Frequently calls adjust_obj_size().
479 template <class SpaceType>
480 static inline void scan_and_adjust_pointers(SpaceType* space);
481
482 // Frequently calls obj_size().
483 template <class SpaceType>
484 static inline void scan_and_compact(SpaceType* space);
485
486 // Frequently calls scanned_block_is_obj() and scanned_block_size().
487 // Requires the scan_limit() function.
488 template <class SpaceType>
489 static inline void scan_and_forward(SpaceType* space, CompactPoint* cp);
490 };
491
492 class GenSpaceMangler;
493
494 // A space in which the free area is contiguous. It therefore supports
495 // faster allocation, and compaction.
496 class ContiguousSpace: public CompactibleSpace {
497 friend class VMStructs;
498 // Allow scan_and_forward function to call (private) overrides for auxiliary functions on this class
499 template <typename SpaceType>
500 friend void CompactibleSpace::scan_and_forward(SpaceType* space, CompactPoint* cp);
501
502 private:
503 // Auxiliary functions for scan_and_forward support.
504 // See comments for CompactibleSpace for more information.
505 inline HeapWord* scan_limit() const {
506 return top();
507 }
508
509 inline bool scanned_block_is_obj(const HeapWord* addr) const {
510 return true; // Always true, since scan_limit is top
511 }
512
513 inline size_t scanned_block_size(const HeapWord* addr) const {
514 return oop(addr)->size();
515 }
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 WaterMark bottom_mark() { return WaterMark(this, bottom()); }
544 WaterMark top_mark() { return WaterMark(this, top()); }
545 WaterMark saved_mark() { return WaterMark(this, saved_mark_word()); }
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_ALL_GCS
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_ALL_GCS
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 CardTableModRefBS::PrecisionStyle precision,
632 HeapWord* boundary = NULL);
633
634 // Apply "blk->do_oop" to the addresses of all reference fields in objects
635 // starting with the _saved_mark_word, which was noted during a generation's
636 // save_marks and is required to denote the head of an object.
637 // Fields in objects allocated by applications of the closure
638 // *are* included in the iteration.
639 // Updates _saved_mark_word to point to just after the last object
640 // iterated over.
641 #define ContigSpace_OOP_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
642 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk);
643
644 ALL_SINCE_SAVE_MARKS_CLOSURES(ContigSpace_OOP_SINCE_SAVE_MARKS_DECL)
645 #undef ContigSpace_OOP_SINCE_SAVE_MARKS_DECL
646
647 // Same as object_iterate, but starting from "mark", which is required
648 // to denote the start of an object. Objects allocated by
649 // applications of the closure *are* included in the iteration.
650 virtual void object_iterate_from(WaterMark mark, ObjectClosure* blk);
651
652 // Very inefficient implementation.
653 virtual HeapWord* block_start_const(const void* p) const;
654 size_t block_size(const HeapWord* p) const;
655 // If a block is in the allocated area, it is an object.
656 bool block_is_obj(const HeapWord* p) const { return p < top(); }
657
658 // Addresses for inlined allocation
659 HeapWord** top_addr() { return &_top; }
660 HeapWord** end_addr() { return &_end; }
661
662 // Overrides for more efficient compaction support.
663 void prepare_for_compaction(CompactPoint* cp);
664
665 // PrintHeapAtGC support.
666 virtual void print_on(outputStream* st) const;
667
668 // Checked dynamic downcasts.
669 virtual ContiguousSpace* toContiguousSpace() {
670 return this;
671 }
672
673 // Debugging
674 virtual void verify() const;
675
676 // Used to increase collection frequency. "factor" of 0 means entire
677 // space.
678 void allocate_temporary_filler(int factor);
679 };
680
681
682 // A dirty card to oop closure that does filtering.
683 // It knows how to filter out objects that are outside of the _boundary.
684 class Filtering_DCTOC : public DirtyCardToOopClosure {
685 protected:
686 // Override.
687 void walk_mem_region(MemRegion mr,
688 HeapWord* bottom, HeapWord* top);
689
690 // Walk the given memory region, from bottom to top, applying
691 // the given oop closure to (possibly) all objects found. The
692 // given oop closure may or may not be the same as the oop
693 // closure with which this closure was created, as it may
694 // be a filtering closure which makes use of the _boundary.
695 // We offer two signatures, so the FilteringClosure static type is
696 // apparent.
697 virtual void walk_mem_region_with_cl(MemRegion mr,
698 HeapWord* bottom, HeapWord* top,
699 ExtendedOopClosure* cl) = 0;
700 virtual void walk_mem_region_with_cl(MemRegion mr,
701 HeapWord* bottom, HeapWord* top,
702 FilteringClosure* cl) = 0;
703
704 public:
705 Filtering_DCTOC(Space* sp, ExtendedOopClosure* cl,
706 CardTableModRefBS::PrecisionStyle precision,
707 HeapWord* boundary) :
708 DirtyCardToOopClosure(sp, cl, precision, boundary) {}
709 };
710
711 // A dirty card to oop closure for contiguous spaces
712 // (ContiguousSpace and sub-classes).
713 // It is a FilteringClosure, as defined above, and it knows:
714 //
715 // 1. That the actual top of any area in a memory region
716 // contained by the space is bounded by the end of the contiguous
717 // region of the space.
718 // 2. That the space is really made up of objects and not just
719 // blocks.
720
721 class ContiguousSpaceDCTOC : public Filtering_DCTOC {
722 protected:
723 // Overrides.
724 HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj);
725
726 virtual void walk_mem_region_with_cl(MemRegion mr,
727 HeapWord* bottom, HeapWord* top,
728 ExtendedOopClosure* cl);
729 virtual void walk_mem_region_with_cl(MemRegion mr,
730 HeapWord* bottom, HeapWord* top,
731 FilteringClosure* cl);
732
733 public:
734 ContiguousSpaceDCTOC(ContiguousSpace* sp, ExtendedOopClosure* cl,
735 CardTableModRefBS::PrecisionStyle precision,
736 HeapWord* boundary) :
737 Filtering_DCTOC(sp, cl, precision, boundary)
738 {}
739 };
740
741 // A ContigSpace that Supports an efficient "block_start" operation via
742 // a BlockOffsetArray (whose BlockOffsetSharedArray may be shared with
743 // other spaces.) This is the abstract base class for old generation
744 // (tenured) spaces.
745
746 class OffsetTableContigSpace: public ContiguousSpace {
747 friend class VMStructs;
748 protected:
749 BlockOffsetArrayContigSpace _offsets;
750 Mutex _par_alloc_lock;
751
752 public:
753 // Constructor
754 OffsetTableContigSpace(BlockOffsetSharedArray* sharedOffsetArray,
755 MemRegion mr);
756
757 void set_bottom(HeapWord* value);
758 void set_end(HeapWord* value);
759
760 void clear(bool mangle_space);
761
762 inline HeapWord* block_start_const(const void* p) const;
763
764 // Add offset table update.
765 virtual inline HeapWord* allocate(size_t word_size);
766 inline HeapWord* par_allocate(size_t word_size);
767
768 // MarkSweep support phase3
769 virtual HeapWord* initialize_threshold();
770 virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* end);
771
772 virtual void print_on(outputStream* st) const;
773
774 // Debugging
775 void verify() const;
776 };
777
778
779 // Class TenuredSpace is used by TenuredGeneration
780
781 class TenuredSpace: public OffsetTableContigSpace {
782 friend class VMStructs;
783 protected:
784 // Mark sweep support
785 size_t allowed_dead_ratio() const;
786 public:
787 // Constructor
788 TenuredSpace(BlockOffsetSharedArray* sharedOffsetArray,
789 MemRegion mr) :
790 OffsetTableContigSpace(sharedOffsetArray, mr) {}
791 };
792 #endif // SHARE_VM_MEMORY_SPACE_HPP