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