1 /*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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24
25 #ifndef SHARE_VM_GC_SHARED_SPACE_HPP
26 #define SHARE_VM_GC_SHARED_SPACE_HPP
27
28 #include "gc/shared/blockOffsetTable.hpp"
29 #include "gc/shared/cardTableModRefBS.hpp"
30 #include "gc/shared/watermark.hpp"
31 #include "gc/shared/workgroup.hpp"
32 #include "memory/allocation.hpp"
33 #include "memory/iterator.hpp"
34 #include "memory/memRegion.hpp"
35 #include "oops/markOop.hpp"
36 #include "runtime/mutexLocker.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 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,
187 bool parallel);
188
189 // If "p" is in the space, returns the address of the start of the
190 // "block" that contains "p". We say "block" instead of "object" since
191 // some heaps may not pack objects densely; a chunk may either be an
192 // object or a non-object. If "p" is not in the space, return NULL.
193 virtual HeapWord* block_start_const(const void* p) const = 0;
194
195 // The non-const version may have benevolent side effects on the data
196 // structure supporting these calls, possibly speeding up future calls.
197 // The default implementation, however, is simply to call the const
198 // version.
199 virtual HeapWord* block_start(const void* p);
200
201 // Requires "addr" to be the start of a chunk, and returns its size.
202 // "addr + size" is required to be the start of a new chunk, or the end
203 // of the active area of the heap.
204 virtual size_t block_size(const HeapWord* addr) const = 0;
205
206 // Requires "addr" to be the start of a block, and returns "TRUE" iff
207 // the block is an object.
208 virtual bool block_is_obj(const HeapWord* addr) const = 0;
209
210 // Requires "addr" to be the start of a block, and returns "TRUE" iff
211 // the block is an object and the object is alive.
212 virtual bool obj_is_alive(const HeapWord* addr) const;
213
214 // Allocation (return NULL if full). Assumes the caller has established
215 // mutually exclusive access to the space.
216 virtual HeapWord* allocate(size_t word_size) = 0;
217
218 // Allocation (return NULL if full). Enforces mutual exclusion internally.
219 virtual HeapWord* par_allocate(size_t word_size) = 0;
220
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
225 // PrintHeapAtGC support
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 ExtendedOopClosure* _cl;
257 Space* _sp;
258 CardTableModRefBS::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, ExtendedOopClosure* cl,
287 CardTableModRefBS::PrecisionStyle precision,
288 HeapWord* boundary) :
289 _sp(sp), _cl(cl), _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 return oop(addr)->size();
368 }
369
370 inline oop make_oop(HeapWord* addr) const {
371 return oop(addr);
372 }
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 // MarkSweep support phase2
408
409 // Start the process of compaction of the current space: compute
410 // post-compaction addresses, and insert forwarding pointers. The fields
411 // "cp->gen" and "cp->compaction_space" are the generation and space into
412 // which we are currently compacting. This call updates "cp" as necessary,
413 // and leaves the "compaction_top" of the final value of
414 // "cp->compaction_space" up-to-date. Offset tables may be updated in
415 // this phase as if the final copy had occurred; if so, "cp->threshold"
416 // indicates when the next such action should be taken.
417 virtual void prepare_for_compaction(CompactPoint* cp) = 0;
418 // MarkSweep support phase3
419 virtual void adjust_pointers();
420 // MarkSweep support phase4
421 virtual void compact();
422
423 // The maximum percentage of objects that can be dead in the compacted
424 // live part of a compacted space ("deadwood" support.)
425 virtual size_t allowed_dead_ratio() const { return 0; };
426
427 // Some contiguous spaces may maintain some data structures that should
428 // be updated whenever an allocation crosses a boundary. This function
429 // returns the first such boundary.
430 // (The default implementation returns the end of the space, so the
431 // boundary is never crossed.)
432 virtual HeapWord* initialize_threshold() { return end(); }
433
434 // "q" is an object of the given "size" that should be forwarded;
435 // "cp" names the generation ("gen") and containing "this" (which must
436 // also equal "cp->space"). "compact_top" is where in "this" the
437 // next object should be forwarded to. If there is room in "this" for
438 // the object, insert an appropriate forwarding pointer in "q".
439 // If not, go to the next compaction space (there must
440 // be one, since compaction must succeed -- we go to the first space of
441 // the previous generation if necessary, updating "cp"), reset compact_top
442 // and then forward. In either case, returns the new value of "compact_top".
443 // If the forwarding crosses "cp->threshold", invokes the "cross_threshold"
444 // function of the then-current compaction space, and updates "cp->threshold
445 // accordingly".
446 virtual HeapWord* forward(oop q, size_t size, CompactPoint* cp,
447 HeapWord* compact_top);
448
449 virtual oop compact_oop(HeapWord* addr) const {
450 return oop(addr);
451 }
452
453 // Return a size with adjustments as required of the space.
454 virtual size_t adjust_object_size_v(size_t size) const { return size; }
455
456 protected:
457 // Used during compaction.
458 HeapWord* _first_dead;
459 HeapWord* _end_of_live;
460
461 // Minimum size of a free block.
462 virtual size_t minimum_free_block_size() const { return 0; }
463
464 // This the function is invoked when an allocation of an object covering
465 // "start" to "end occurs crosses the threshold; returns the next
466 // threshold. (The default implementation does nothing.)
467 virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* the_end) {
468 return end();
469 }
470
471 // Requires "allowed_deadspace_words > 0", that "q" is the start of a
472 // free block of the given "word_len", and that "q", were it an object,
473 // would not move if forwarded. If the size allows, fill the free
474 // block with an object, to prevent excessive compaction. Returns "true"
475 // iff the free region was made deadspace, and modifies
476 // "allowed_deadspace_words" to reflect the number of available deadspace
477 // words remaining after this operation.
478 bool insert_deadspace(size_t& allowed_deadspace_words, HeapWord* q,
479 size_t word_len);
480
481 // Below are template functions for scan_and_* algorithms (avoiding virtual calls).
482 // The space argument should be a subclass of CompactibleSpace, implementing
483 // scan_limit(), scanned_block_is_obj(), and scanned_block_size(),
484 // and possibly also overriding obj_size(), and adjust_obj_size().
485 // These functions should avoid virtual calls whenever possible.
486
487 // Frequently calls adjust_obj_size().
488 template <class SpaceType>
489 static inline void scan_and_adjust_pointers(SpaceType* space);
490
491 // Frequently calls obj_size().
492 template <class SpaceType>
493 static inline void scan_and_compact(SpaceType* space);
494
495 // Frequently calls scanned_block_is_obj() and scanned_block_size().
496 // Requires the scan_limit() function.
497 template <class SpaceType>
498 static inline void scan_and_forward(SpaceType* space, CompactPoint* cp);
499 };
500
501 class GenSpaceMangler;
502
503 // A space in which the free area is contiguous. It therefore supports
504 // faster allocation, and compaction.
505 class ContiguousSpace: public CompactibleSpace {
506 friend class VMStructs;
507 // Allow scan_and_forward function to call (private) overrides for auxiliary functions on this class
508 template <typename SpaceType>
509 friend void CompactibleSpace::scan_and_forward(SpaceType* space, CompactPoint* cp);
510
511 private:
512 // Auxiliary functions for scan_and_forward support.
513 // See comments for CompactibleSpace for more information.
514 inline HeapWord* scan_limit() const {
515 return top();
516 }
517
518 inline bool scanned_block_is_obj(const HeapWord* addr) const {
519 return true; // Always true, since scan_limit is top
520 }
521
522 inline size_t scanned_block_size(const HeapWord* addr) const {
523 return oop(addr)->size();
524 }
525
526 protected:
527 HeapWord* _top;
528 HeapWord* _concurrent_iteration_safe_limit;
529 // A helper for mangling the unused area of the space in debug builds.
530 GenSpaceMangler* _mangler;
531
532 GenSpaceMangler* mangler() { return _mangler; }
533
534 // Allocation helpers (return NULL if full).
535 inline HeapWord* allocate_impl(size_t word_size);
536 inline HeapWord* par_allocate_impl(size_t word_size);
537
538 public:
539 ContiguousSpace();
540 ~ContiguousSpace();
541
542 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
543 virtual void clear(bool mangle_space);
544
545 // Accessors
546 HeapWord* top() const { return _top; }
547 void set_top(HeapWord* value) { _top = value; }
548
549 void set_saved_mark() { _saved_mark_word = top(); }
550 void reset_saved_mark() { _saved_mark_word = bottom(); }
551
552 WaterMark bottom_mark() { return WaterMark(this, bottom()); }
553 WaterMark top_mark() { return WaterMark(this, top()); }
554 WaterMark saved_mark() { return WaterMark(this, saved_mark_word()); }
555 bool saved_mark_at_top() const { return saved_mark_word() == top(); }
556
557 // In debug mode mangle (write it with a particular bit
558 // pattern) the unused part of a space.
559
560 // Used to save the an address in a space for later use during mangling.
561 void set_top_for_allocations(HeapWord* v) PRODUCT_RETURN;
562 // Used to save the space's current top for later use during mangling.
563 void set_top_for_allocations() PRODUCT_RETURN;
564
565 // Mangle regions in the space from the current top up to the
566 // previously mangled part of the space.
567 void mangle_unused_area() PRODUCT_RETURN;
568 // Mangle [top, end)
569 void mangle_unused_area_complete() PRODUCT_RETURN;
570
571 // Do some sparse checking on the area that should have been mangled.
572 void check_mangled_unused_area(HeapWord* limit) PRODUCT_RETURN;
573 // Check the complete area that should have been mangled.
574 // This code may be NULL depending on the macro DEBUG_MANGLING.
575 void check_mangled_unused_area_complete() PRODUCT_RETURN;
576
577 // Size computations: sizes in bytes.
578 size_t capacity() const { return byte_size(bottom(), end()); }
579 size_t used() const { return byte_size(bottom(), top()); }
580 size_t free() const { return byte_size(top(), end()); }
581
582 virtual bool is_free_block(const HeapWord* p) const;
583
584 // In a contiguous space we have a more obvious bound on what parts
585 // contain objects.
586 MemRegion used_region() const { return MemRegion(bottom(), top()); }
587
588 // Allocation (return NULL if full)
589 virtual HeapWord* allocate(size_t word_size);
590 virtual HeapWord* par_allocate(size_t word_size);
591 HeapWord* allocate_aligned(size_t word_size);
592
593 // Iteration
594 void oop_iterate(ExtendedOopClosure* cl);
595 virtual void object_iterate(ObjectClosure* blk);
596 // For contiguous spaces this method will iterate safely over objects
597 // in the space (i.e., between bottom and top) when at a safepoint.
598 void safe_object_iterate(ObjectClosure* blk);
599
600 // Iterate over as many initialized objects in the space as possible,
601 // calling "cl.do_object_careful" on each. Return NULL if all objects
602 // in the space (at the start of the iteration) were iterated over.
603 // Return an address indicating the extent of the iteration in the
604 // event that the iteration had to return because of finding an
605 // uninitialized object in the space, or if the closure "cl"
606 // signaled early termination.
607 HeapWord* object_iterate_careful(ObjectClosureCareful* cl);
608 HeapWord* concurrent_iteration_safe_limit() {
609 assert(_concurrent_iteration_safe_limit <= top(),
610 "_concurrent_iteration_safe_limit update missed");
611 return _concurrent_iteration_safe_limit;
612 }
613 // changes the safe limit, all objects from bottom() to the new
614 // limit should be properly initialized
615 void set_concurrent_iteration_safe_limit(HeapWord* new_limit) {
616 assert(new_limit <= top(), "uninitialized objects in the safe range");
617 _concurrent_iteration_safe_limit = new_limit;
618 }
619
620
621 #if INCLUDE_ALL_GCS
622 // In support of parallel oop_iterate.
623 #define ContigSpace_PAR_OOP_ITERATE_DECL(OopClosureType, nv_suffix) \
624 void par_oop_iterate(MemRegion mr, OopClosureType* blk);
625
626 ALL_PAR_OOP_ITERATE_CLOSURES(ContigSpace_PAR_OOP_ITERATE_DECL)
627 #undef ContigSpace_PAR_OOP_ITERATE_DECL
628 #endif // INCLUDE_ALL_GCS
629
630 // Compaction support
631 virtual void reset_after_compaction() {
632 assert(compaction_top() >= bottom() && compaction_top() <= end(), "should point inside space");
633 set_top(compaction_top());
634 // set new iteration safe limit
635 set_concurrent_iteration_safe_limit(compaction_top());
636 }
637
638 // Override.
639 DirtyCardToOopClosure* new_dcto_cl(ExtendedOopClosure* cl,
640 CardTableModRefBS::PrecisionStyle precision,
641 HeapWord* boundary,
642 bool parallel);
643
644 // Apply "blk->do_oop" to the addresses of all reference fields in objects
645 // starting with the _saved_mark_word, which was noted during a generation's
646 // save_marks and is required to denote the head of an object.
647 // Fields in objects allocated by applications of the closure
648 // *are* included in the iteration.
649 // Updates _saved_mark_word to point to just after the last object
650 // iterated over.
651 #define ContigSpace_OOP_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
652 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk);
653
654 ALL_SINCE_SAVE_MARKS_CLOSURES(ContigSpace_OOP_SINCE_SAVE_MARKS_DECL)
655 #undef ContigSpace_OOP_SINCE_SAVE_MARKS_DECL
656
657 // Same as object_iterate, but starting from "mark", which is required
658 // to denote the start of an object. Objects allocated by
659 // applications of the closure *are* included in the iteration.
660 virtual void object_iterate_from(WaterMark mark, ObjectClosure* blk);
661
662 // Very inefficient implementation.
663 virtual HeapWord* block_start_const(const void* p) const;
664 size_t block_size(const HeapWord* p) const;
665 // If a block is in the allocated area, it is an object.
666 bool block_is_obj(const HeapWord* p) const { return p < top(); }
667
668 // Addresses for inlined allocation
669 HeapWord** top_addr() { return &_top; }
670 HeapWord** end_addr() { return &_end; }
671
672 // Overrides for more efficient compaction support.
673 void prepare_for_compaction(CompactPoint* cp);
674
675 // PrintHeapAtGC support.
676 virtual void print_on(outputStream* st) const;
677
678 // Checked dynamic downcasts.
679 virtual ContiguousSpace* toContiguousSpace() {
680 return this;
681 }
682
683 // Debugging
684 virtual void verify() const;
685
686 // Used to increase collection frequency. "factor" of 0 means entire
687 // space.
688 void allocate_temporary_filler(int factor);
689 };
690
691
692 // A dirty card to oop closure that does filtering.
693 // It knows how to filter out objects that are outside of the _boundary.
694 class Filtering_DCTOC : public DirtyCardToOopClosure {
695 protected:
696 // Override.
697 void walk_mem_region(MemRegion mr,
698 HeapWord* bottom, HeapWord* top);
699
700 // Walk the given memory region, from bottom to top, applying
701 // the given oop closure to (possibly) all objects found. The
702 // given oop closure may or may not be the same as the oop
703 // closure with which this closure was created, as it may
704 // be a filtering closure which makes use of the _boundary.
705 // We offer two signatures, so the FilteringClosure static type is
706 // apparent.
707 virtual void walk_mem_region_with_cl(MemRegion mr,
708 HeapWord* bottom, HeapWord* top,
709 ExtendedOopClosure* cl) = 0;
710 virtual void walk_mem_region_with_cl(MemRegion mr,
711 HeapWord* bottom, HeapWord* top,
712 FilteringClosure* cl) = 0;
713
714 public:
715 Filtering_DCTOC(Space* sp, ExtendedOopClosure* cl,
716 CardTableModRefBS::PrecisionStyle precision,
717 HeapWord* boundary) :
718 DirtyCardToOopClosure(sp, cl, precision, boundary) {}
719 };
720
721 // A dirty card to oop closure for contiguous spaces
722 // (ContiguousSpace and sub-classes).
723 // It is a FilteringClosure, as defined above, and it knows:
724 //
725 // 1. That the actual top of any area in a memory region
726 // contained by the space is bounded by the end of the contiguous
727 // region of the space.
728 // 2. That the space is really made up of objects and not just
729 // blocks.
730
731 class ContiguousSpaceDCTOC : public Filtering_DCTOC {
732 protected:
733 // Overrides.
734 HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj);
735
736 virtual void walk_mem_region_with_cl(MemRegion mr,
737 HeapWord* bottom, HeapWord* top,
738 ExtendedOopClosure* cl);
739 virtual void walk_mem_region_with_cl(MemRegion mr,
740 HeapWord* bottom, HeapWord* top,
741 FilteringClosure* cl);
742
743 public:
744 ContiguousSpaceDCTOC(ContiguousSpace* sp, ExtendedOopClosure* cl,
745 CardTableModRefBS::PrecisionStyle precision,
746 HeapWord* boundary) :
747 Filtering_DCTOC(sp, cl, precision, boundary)
748 {}
749 };
750
751 // A ContigSpace that Supports an efficient "block_start" operation via
752 // a BlockOffsetArray (whose BlockOffsetSharedArray may be shared with
753 // other spaces.) This is the abstract base class for old generation
754 // (tenured) spaces.
755
756 class OffsetTableContigSpace: public ContiguousSpace {
757 friend class VMStructs;
758 protected:
759 BlockOffsetArrayContigSpace _offsets;
760 Mutex _par_alloc_lock;
761
762 public:
763 // Constructor
764 OffsetTableContigSpace(BlockOffsetSharedArray* sharedOffsetArray,
765 MemRegion mr);
766
767 void set_bottom(HeapWord* value);
768 void set_end(HeapWord* value);
769
770 void clear(bool mangle_space);
771
772 inline HeapWord* block_start_const(const void* p) const;
773
774 // Add offset table update.
775 virtual inline HeapWord* allocate(size_t word_size);
776 inline HeapWord* par_allocate(size_t word_size);
777
778 // MarkSweep support phase3
779 virtual HeapWord* initialize_threshold();
780 virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* end);
781
782 virtual void print_on(outputStream* st) const;
783
784 // Debugging
785 void verify() const;
786 };
787
788
789 // Class TenuredSpace is used by TenuredGeneration
790
791 class TenuredSpace: public OffsetTableContigSpace {
792 friend class VMStructs;
793 protected:
794 // Mark sweep support
795 size_t allowed_dead_ratio() const;
796 public:
797 // Constructor
798 TenuredSpace(BlockOffsetSharedArray* sharedOffsetArray,
799 MemRegion mr) :
800 OffsetTableContigSpace(sharedOffsetArray, mr) {}
801 };
802 #endif // SHARE_VM_GC_SHARED_SPACE_HPP