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 public:
371 CompactibleSpace() :
372 _compaction_top(NULL), _next_compaction_space(NULL) {}
373
374 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
375 virtual void clear(bool mangle_space);
376
377 // Used temporarily during a compaction phase to hold the value
378 // top should have when compaction is complete.
379 HeapWord* compaction_top() const { return _compaction_top; }
380
381 void set_compaction_top(HeapWord* value) {
382 assert(value == NULL || (value >= bottom() && value <= end()),
383 "should point inside space");
384 _compaction_top = value;
385 }
386
387 // Perform operations on the space needed after a compaction
388 // has been performed.
389 virtual void reset_after_compaction() = 0;
390
391 // Returns the next space (in the current generation) to be compacted in
392 // the global compaction order. Also is used to select the next
393 // space into which to compact.
394
395 virtual CompactibleSpace* next_compaction_space() const {
396 return _next_compaction_space;
397 }
398
399 void set_next_compaction_space(CompactibleSpace* csp) {
400 _next_compaction_space = csp;
401 }
402
403 // MarkSweep support phase2
404
405 // Start the process of compaction of the current space: compute
406 // post-compaction addresses, and insert forwarding pointers. The fields
407 // "cp->gen" and "cp->compaction_space" are the generation and space into
408 // which we are currently compacting. This call updates "cp" as necessary,
409 // and leaves the "compaction_top" of the final value of
410 // "cp->compaction_space" up-to-date. Offset tables may be updated in
411 // this phase as if the final copy had occurred; if so, "cp->threshold"
412 // indicates when the next such action should be taken.
413 virtual void prepare_for_compaction(CompactPoint* cp) = 0;
414 // MarkSweep support phase3
415 virtual void adjust_pointers();
416 // MarkSweep support phase4
417 virtual void compact();
418
419 // The maximum percentage of objects that can be dead in the compacted
420 // live part of a compacted space ("deadwood" support.)
421 virtual size_t allowed_dead_ratio() const { return 0; };
422
423 // Some contiguous spaces may maintain some data structures that should
424 // be updated whenever an allocation crosses a boundary. This function
425 // returns the first such boundary.
426 // (The default implementation returns the end of the space, so the
427 // boundary is never crossed.)
428 virtual HeapWord* initialize_threshold() { return end(); }
429
430 // "q" is an object of the given "size" that should be forwarded;
431 // "cp" names the generation ("gen") and containing "this" (which must
432 // also equal "cp->space"). "compact_top" is where in "this" the
433 // next object should be forwarded to. If there is room in "this" for
434 // the object, insert an appropriate forwarding pointer in "q".
435 // If not, go to the next compaction space (there must
436 // be one, since compaction must succeed -- we go to the first space of
437 // the previous generation if necessary, updating "cp"), reset compact_top
438 // and then forward. In either case, returns the new value of "compact_top".
439 // If the forwarding crosses "cp->threshold", invokes the "cross_threshold"
440 // function of the then-current compaction space, and updates "cp->threshold
441 // accordingly".
442 virtual HeapWord* forward(oop q, size_t size, CompactPoint* cp,
443 HeapWord* compact_top);
444
445 // Return a size with adjustments as required of the space.
446 virtual size_t adjust_object_size_v(size_t size) const { return size; }
447
448 protected:
449 // Used during compaction.
450 HeapWord* _first_dead;
451 HeapWord* _end_of_live;
452
453 // Minimum size of a free block.
454 virtual size_t minimum_free_block_size() const { return 0; }
455
456 // This the function is invoked when an allocation of an object covering
457 // "start" to "end occurs crosses the threshold; returns the next
458 // threshold. (The default implementation does nothing.)
459 virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* the_end) {
460 return end();
461 }
462
463 // Requires "allowed_deadspace_words > 0", that "q" is the start of a
464 // free block of the given "word_len", and that "q", were it an object,
465 // would not move if forwarded. If the size allows, fill the free
466 // block with an object, to prevent excessive compaction. Returns "true"
467 // iff the free region was made deadspace, and modifies
468 // "allowed_deadspace_words" to reflect the number of available deadspace
469 // words remaining after this operation.
470 bool insert_deadspace(size_t& allowed_deadspace_words, HeapWord* q,
471 size_t word_len);
472
473 // Below are template functions for scan_and_* algorithms (avoiding virtual calls).
474 // The space argument should be a subclass of CompactibleSpace, implementing
475 // scan_limit(), scanned_block_is_obj(), and scanned_block_size(),
476 // and possibly also overriding obj_size(), and adjust_obj_size().
477 // These functions should avoid virtual calls whenever possible.
478
479 // Frequently calls adjust_obj_size().
480 template <class SpaceType>
481 static inline void scan_and_adjust_pointers(SpaceType* space);
482
483 // Frequently calls obj_size().
484 template <class SpaceType>
485 static inline void scan_and_compact(SpaceType* space);
486
487 // Frequently calls scanned_block_is_obj() and scanned_block_size().
488 // Requires the scan_limit() function.
489 template <class SpaceType>
490 static inline void scan_and_forward(SpaceType* space, CompactPoint* cp);
491 };
492
493 class GenSpaceMangler;
494
495 // A space in which the free area is contiguous. It therefore supports
496 // faster allocation, and compaction.
497 class ContiguousSpace: public CompactibleSpace {
498 friend class VMStructs;
499 // Allow scan_and_forward function to call (private) overrides for auxiliary functions on this class
500 template <typename SpaceType>
501 friend void CompactibleSpace::scan_and_forward(SpaceType* space, CompactPoint* cp);
502
503 private:
504 // Auxiliary functions for scan_and_forward support.
505 // See comments for CompactibleSpace for more information.
506 inline HeapWord* scan_limit() const {
507 return top();
508 }
509
510 inline bool scanned_block_is_obj(const HeapWord* addr) const {
511 return true; // Always true, since scan_limit is top
512 }
513
514 inline size_t scanned_block_size(const HeapWord* addr) const {
515 return oop(addr)->size();
516 }
517
518 protected:
519 HeapWord* _top;
520 HeapWord* _concurrent_iteration_safe_limit;
521 // A helper for mangling the unused area of the space in debug builds.
522 GenSpaceMangler* _mangler;
523
524 GenSpaceMangler* mangler() { return _mangler; }
525
526 // Allocation helpers (return NULL if full).
527 inline HeapWord* allocate_impl(size_t word_size);
528 inline HeapWord* par_allocate_impl(size_t word_size);
529
530 public:
531 ContiguousSpace();
532 ~ContiguousSpace();
533
534 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
535 virtual void clear(bool mangle_space);
536
537 // Accessors
538 HeapWord* top() const { return _top; }
539 void set_top(HeapWord* value) { _top = value; }
540
541 void set_saved_mark() { _saved_mark_word = top(); }
542 void reset_saved_mark() { _saved_mark_word = bottom(); }
543
544 WaterMark bottom_mark() { return WaterMark(this, bottom()); }
545 WaterMark top_mark() { return WaterMark(this, top()); }
546 WaterMark saved_mark() { return WaterMark(this, saved_mark_word()); }
547 bool saved_mark_at_top() const { return saved_mark_word() == top(); }
548
549 // In debug mode mangle (write it with a particular bit
550 // pattern) the unused part of a space.
551
552 // Used to save the an address in a space for later use during mangling.
553 void set_top_for_allocations(HeapWord* v) PRODUCT_RETURN;
554 // Used to save the space's current top for later use during mangling.
555 void set_top_for_allocations() PRODUCT_RETURN;
556
557 // Mangle regions in the space from the current top up to the
558 // previously mangled part of the space.
559 void mangle_unused_area() PRODUCT_RETURN;
560 // Mangle [top, end)
561 void mangle_unused_area_complete() PRODUCT_RETURN;
562
563 // Do some sparse checking on the area that should have been mangled.
564 void check_mangled_unused_area(HeapWord* limit) PRODUCT_RETURN;
565 // Check the complete area that should have been mangled.
566 // This code may be NULL depending on the macro DEBUG_MANGLING.
567 void check_mangled_unused_area_complete() PRODUCT_RETURN;
568
569 // Size computations: sizes in bytes.
570 size_t capacity() const { return byte_size(bottom(), end()); }
571 size_t used() const { return byte_size(bottom(), top()); }
572 size_t free() const { return byte_size(top(), end()); }
573
574 virtual bool is_free_block(const HeapWord* p) const;
575
576 // In a contiguous space we have a more obvious bound on what parts
577 // contain objects.
578 MemRegion used_region() const { return MemRegion(bottom(), top()); }
579
580 // Allocation (return NULL if full)
581 virtual HeapWord* allocate(size_t word_size);
582 virtual HeapWord* par_allocate(size_t word_size);
583 HeapWord* allocate_aligned(size_t word_size);
584
585 // Iteration
586 void oop_iterate(ExtendedOopClosure* cl);
587 void object_iterate(ObjectClosure* blk);
588 // For contiguous spaces this method will iterate safely over objects
589 // in the space (i.e., between bottom and top) when at a safepoint.
590 void safe_object_iterate(ObjectClosure* blk);
591
592 // Iterate over as many initialized objects in the space as possible,
593 // calling "cl.do_object_careful" on each. Return NULL if all objects
594 // in the space (at the start of the iteration) were iterated over.
595 // Return an address indicating the extent of the iteration in the
596 // event that the iteration had to return because of finding an
597 // uninitialized object in the space, or if the closure "cl"
598 // signaled early termination.
599 HeapWord* object_iterate_careful(ObjectClosureCareful* cl);
600 HeapWord* concurrent_iteration_safe_limit() {
601 assert(_concurrent_iteration_safe_limit <= top(),
602 "_concurrent_iteration_safe_limit update missed");
603 return _concurrent_iteration_safe_limit;
604 }
605 // changes the safe limit, all objects from bottom() to the new
606 // limit should be properly initialized
607 void set_concurrent_iteration_safe_limit(HeapWord* new_limit) {
608 assert(new_limit <= top(), "uninitialized objects in the safe range");
609 _concurrent_iteration_safe_limit = new_limit;
610 }
611
612
613 #if INCLUDE_ALL_GCS
614 // In support of parallel oop_iterate.
615 #define ContigSpace_PAR_OOP_ITERATE_DECL(OopClosureType, nv_suffix) \
616 void par_oop_iterate(MemRegion mr, OopClosureType* blk);
617
618 ALL_PAR_OOP_ITERATE_CLOSURES(ContigSpace_PAR_OOP_ITERATE_DECL)
619 #undef ContigSpace_PAR_OOP_ITERATE_DECL
620 #endif // INCLUDE_ALL_GCS
621
622 // Compaction support
623 virtual void reset_after_compaction() {
624 assert(compaction_top() >= bottom() && compaction_top() <= end(), "should point inside space");
625 set_top(compaction_top());
626 // set new iteration safe limit
627 set_concurrent_iteration_safe_limit(compaction_top());
628 }
629
630 // Override.
631 DirtyCardToOopClosure* new_dcto_cl(ExtendedOopClosure* cl,
632 CardTableModRefBS::PrecisionStyle precision,
633 HeapWord* boundary,
634 bool parallel);
635
636 // Apply "blk->do_oop" to the addresses of all reference fields in objects
637 // starting with the _saved_mark_word, which was noted during a generation's
638 // save_marks and is required to denote the head of an object.
639 // Fields in objects allocated by applications of the closure
640 // *are* included in the iteration.
641 // Updates _saved_mark_word to point to just after the last object
642 // iterated over.
643 #define ContigSpace_OOP_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
644 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk);
645
646 ALL_SINCE_SAVE_MARKS_CLOSURES(ContigSpace_OOP_SINCE_SAVE_MARKS_DECL)
647 #undef ContigSpace_OOP_SINCE_SAVE_MARKS_DECL
648
649 // Same as object_iterate, but starting from "mark", which is required
650 // to denote the start of an object. Objects allocated by
651 // applications of the closure *are* included in the iteration.
652 virtual void object_iterate_from(WaterMark mark, ObjectClosure* blk);
653
654 // Very inefficient implementation.
655 virtual HeapWord* block_start_const(const void* p) const;
656 size_t block_size(const HeapWord* p) const;
657 // If a block is in the allocated area, it is an object.
658 bool block_is_obj(const HeapWord* p) const { return p < top(); }
659
660 // Addresses for inlined allocation
661 HeapWord** top_addr() { return &_top; }
662 HeapWord** end_addr() { return &_end; }
663
664 // Overrides for more efficient compaction support.
665 void prepare_for_compaction(CompactPoint* cp);
666
667 // PrintHeapAtGC support.
668 virtual void print_on(outputStream* st) const;
669
670 // Checked dynamic downcasts.
671 virtual ContiguousSpace* toContiguousSpace() {
672 return this;
673 }
674
675 // Debugging
676 virtual void verify() const;
677
678 // Used to increase collection frequency. "factor" of 0 means entire
679 // space.
680 void allocate_temporary_filler(int factor);
681 };
682
683
684 // A dirty card to oop closure that does filtering.
685 // It knows how to filter out objects that are outside of the _boundary.
686 class Filtering_DCTOC : public DirtyCardToOopClosure {
687 protected:
688 // Override.
689 void walk_mem_region(MemRegion mr,
690 HeapWord* bottom, HeapWord* top);
691
692 // Walk the given memory region, from bottom to top, applying
693 // the given oop closure to (possibly) all objects found. The
694 // given oop closure may or may not be the same as the oop
695 // closure with which this closure was created, as it may
696 // be a filtering closure which makes use of the _boundary.
697 // We offer two signatures, so the FilteringClosure static type is
698 // apparent.
699 virtual void walk_mem_region_with_cl(MemRegion mr,
700 HeapWord* bottom, HeapWord* top,
701 ExtendedOopClosure* cl) = 0;
702 virtual void walk_mem_region_with_cl(MemRegion mr,
703 HeapWord* bottom, HeapWord* top,
704 FilteringClosure* cl) = 0;
705
706 public:
707 Filtering_DCTOC(Space* sp, ExtendedOopClosure* cl,
708 CardTableModRefBS::PrecisionStyle precision,
709 HeapWord* boundary) :
710 DirtyCardToOopClosure(sp, cl, precision, boundary) {}
711 };
712
713 // A dirty card to oop closure for contiguous spaces
714 // (ContiguousSpace and sub-classes).
715 // It is a FilteringClosure, as defined above, and it knows:
716 //
717 // 1. That the actual top of any area in a memory region
718 // contained by the space is bounded by the end of the contiguous
719 // region of the space.
720 // 2. That the space is really made up of objects and not just
721 // blocks.
722
723 class ContiguousSpaceDCTOC : public Filtering_DCTOC {
724 protected:
725 // Overrides.
726 HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj);
727
728 virtual void walk_mem_region_with_cl(MemRegion mr,
729 HeapWord* bottom, HeapWord* top,
730 ExtendedOopClosure* cl);
731 virtual void walk_mem_region_with_cl(MemRegion mr,
732 HeapWord* bottom, HeapWord* top,
733 FilteringClosure* cl);
734
735 public:
736 ContiguousSpaceDCTOC(ContiguousSpace* sp, ExtendedOopClosure* cl,
737 CardTableModRefBS::PrecisionStyle precision,
738 HeapWord* boundary) :
739 Filtering_DCTOC(sp, cl, precision, boundary)
740 {}
741 };
742
743 // A ContigSpace that Supports an efficient "block_start" operation via
744 // a BlockOffsetArray (whose BlockOffsetSharedArray may be shared with
745 // other spaces.) This is the abstract base class for old generation
746 // (tenured) spaces.
747
748 class OffsetTableContigSpace: public ContiguousSpace {
749 friend class VMStructs;
750 protected:
751 BlockOffsetArrayContigSpace _offsets;
752 Mutex _par_alloc_lock;
753
754 public:
755 // Constructor
756 OffsetTableContigSpace(BlockOffsetSharedArray* sharedOffsetArray,
757 MemRegion mr);
758
759 void set_bottom(HeapWord* value);
760 void set_end(HeapWord* value);
761
762 void clear(bool mangle_space);
763
764 inline HeapWord* block_start_const(const void* p) const;
765
766 // Add offset table update.
767 virtual inline HeapWord* allocate(size_t word_size);
768 inline HeapWord* par_allocate(size_t word_size);
769
770 // MarkSweep support phase3
771 virtual HeapWord* initialize_threshold();
772 virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* end);
773
774 virtual void print_on(outputStream* st) const;
775
776 // Debugging
777 void verify() const;
778 };
779
780
781 // Class TenuredSpace is used by TenuredGeneration
782
783 class TenuredSpace: public OffsetTableContigSpace {
784 friend class VMStructs;
785 protected:
786 // Mark sweep support
787 size_t allowed_dead_ratio() const;
788 public:
789 // Constructor
790 TenuredSpace(BlockOffsetSharedArray* sharedOffsetArray,
791 MemRegion mr) :
792 OffsetTableContigSpace(sharedOffsetArray, mr) {}
793 };
794 #endif // SHARE_VM_GC_SHARED_SPACE_HPP