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 TenuredGeneration;
66 friend class VMStructs;
67 protected:
68 HeapWord* _bottom;
69 HeapWord* _end;
70
71 // Used in support of save_marks()
72 HeapWord* _saved_mark_word;
73
74 // A sequential tasks done structure. This supports
75 // parallel GC, where we have threads dynamically
76 // claiming sub-tasks from a larger parallel task.
77 SequentialSubTasksDone _par_seq_tasks;
78
79 Space():
80 _bottom(NULL), _end(NULL) { }
81
82 public:
83 // Accessors
84 HeapWord* bottom() const { return _bottom; }
85 HeapWord* end() const { return _end; }
86 virtual void set_bottom(HeapWord* value) { _bottom = value; }
87 virtual void set_end(HeapWord* value) { _end = value; }
88
89 virtual HeapWord* saved_mark_word() const { return _saved_mark_word; }
90
91 void set_saved_mark_word(HeapWord* p) { _saved_mark_word = p; }
92
93 // Returns true if this object has been allocated since a
94 // generation's "save_marks" call.
95 virtual bool obj_allocated_since_save_marks(const oop obj) const {
96 return (HeapWord*)obj >= saved_mark_word();
97 }
98
99 virtual MemRegionClosure* preconsumptionDirtyCardClosure() const {
100 return NULL;
101 }
102
103 // Returns a subregion of the space containing only the allocated objects in
104 // the space.
105 virtual MemRegion used_region() const = 0;
106
107 // Returns a region that is guaranteed to contain (at least) all objects
108 // allocated at the time of the last call to "save_marks". If the space
109 // initializes its DirtyCardToOopClosure's specifying the "contig" option
110 // (that is, if the space is contiguous), then this region must contain only
111 // such objects: the memregion will be from the bottom of the region to the
112 // saved mark. Otherwise, the "obj_allocated_since_save_marks" method of
113 // the space must distinguish between objects in the region allocated before
114 // and after the call to save marks.
115 MemRegion used_region_at_save_marks() const {
116 return MemRegion(bottom(), saved_mark_word());
117 }
118
119 // Initialization.
120 // "initialize" should be called once on a space, before it is used for
121 // any purpose. The "mr" arguments gives the bounds of the space, and
122 // the "clear_space" argument should be true unless the memory in "mr" is
123 // known to be zeroed.
124 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
125
126 // The "clear" method must be called on a region that may have
127 // had allocation performed in it, but is now to be considered empty.
128 virtual void clear(bool mangle_space);
129
130 // For detecting GC bugs. Should only be called at GC boundaries, since
131 // some unused space may be used as scratch space during GC's.
132 // Default implementation does nothing. We also call this when expanding
133 // a space to satisfy an allocation request. See bug #4668531
134 virtual void mangle_unused_area() {}
135 virtual void mangle_unused_area_complete() {}
136 virtual void mangle_region(MemRegion mr) {}
137
138 // Testers
139 bool is_empty() const { return used() == 0; }
140 bool not_empty() const { return used() > 0; }
141
142 // Returns true iff the given the space contains the
143 // given address as part of an allocated object. For
144 // certain kinds of spaces, this might be a potentially
145 // expensive operation. To prevent performance problems
146 // on account of its inadvertent use in product jvm's,
147 // we restrict its use to assertion checks only.
148 bool is_in(const void* p) const {
149 return used_region().contains(p);
150 }
151
152 // Returns true iff the given reserved memory of the space contains the
153 // given address.
154 bool is_in_reserved(const void* p) const { return _bottom <= p && p < _end; }
155
156 // Returns true iff the given block is not allocated.
157 virtual bool is_free_block(const HeapWord* p) const = 0;
158
159 // Test whether p is double-aligned
160 static bool is_aligned(void* p) {
161 return ((intptr_t)p & (sizeof(double)-1)) == 0;
162 }
163
164 // Size computations. Sizes are in bytes.
165 size_t capacity() const { return byte_size(bottom(), end()); }
166 virtual size_t used() const = 0;
167 virtual size_t free() const = 0;
168
169 // Iterate over all the ref-containing fields of all objects in the
170 // space, calling "cl.do_oop" on each. Fields in objects allocated by
171 // applications of the closure are not included in the iteration.
172 virtual void oop_iterate(ExtendedOopClosure* cl);
173
174 // Iterate over all objects in the space, calling "cl.do_object" on
175 // each. Objects allocated by applications of the closure are not
176 // included in the iteration.
177 virtual void object_iterate(ObjectClosure* blk) = 0;
178 // Similar to object_iterate() except only iterates over
179 // objects whose internal references point to objects in the space.
180 virtual void safe_object_iterate(ObjectClosure* blk) = 0;
181
182 // Create and return a new dirty card to oop closure. Can be
183 // overridden to return the appropriate type of closure
184 // depending on the type of space in which the closure will
185 // operate. ResourceArea allocated.
186 virtual DirtyCardToOopClosure* new_dcto_cl(ExtendedOopClosure* cl,
187 CardTableModRefBS::PrecisionStyle precision,
188 HeapWord* boundary = NULL);
189
190 // If "p" is in the space, returns the address of the start of the
191 // "block" that contains "p". We say "block" instead of "object" since
192 // some heaps may not pack objects densely; a chunk may either be an
193 // object or a non-object. If "p" is not in the space, return NULL.
194 virtual HeapWord* block_start_const(const void* p) const = 0;
195
196 // The non-const version may have benevolent side effects on the data
197 // structure supporting these calls, possibly speeding up future calls.
198 // The default implementation, however, is simply to call the const
199 // version.
200 inline virtual HeapWord* block_start(const void* p);
201
202 // Requires "addr" to be the start of a chunk, and returns its size.
203 // "addr + size" is required to be the start of a new chunk, or the end
204 // of the active area of the heap.
205 virtual size_t block_size(const HeapWord* addr) const = 0;
206
207 // Requires "addr" to be the start of a block, and returns "TRUE" iff
208 // the block is an object.
209 virtual bool block_is_obj(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 and the object is alive.
213 virtual bool obj_is_alive(const HeapWord* addr) const;
214
215 // Allocation (return NULL if full). Assumes the caller has established
216 // mutually exclusive access to the space.
217 virtual HeapWord* allocate(size_t word_size) = 0;
218
219 // Allocation (return NULL if full). Enforces mutual exclusion internally.
220 virtual HeapWord* par_allocate(size_t word_size) = 0;
221
222 // Mark-sweep-compact support: all spaces can update pointers to objects
223 // moving as a part of compaction.
224 virtual void adjust_pointers() = 0;
225
226 // PrintHeapAtGC support
227 virtual void print() const;
228 virtual void print_on(outputStream* st) const;
229 virtual void print_short() const;
230 virtual void print_short_on(outputStream* st) const;
231
232
233 // Accessor for parallel sequential tasks.
234 SequentialSubTasksDone* par_seq_tasks() { return &_par_seq_tasks; }
235
236 // IF "this" is a ContiguousSpace, return it, else return NULL.
237 virtual ContiguousSpace* toContiguousSpace() {
238 return NULL;
239 }
240
241 // Debugging
242 virtual void verify() const = 0;
243 };
244
245 // A MemRegionClosure (ResourceObj) whose "do_MemRegion" function applies an
246 // OopClosure to (the addresses of) all the ref-containing fields that could
247 // be modified by virtue of the given MemRegion being dirty. (Note that
248 // because of the imprecise nature of the write barrier, this may iterate
249 // over oops beyond the region.)
250 // This base type for dirty card to oop closures handles memory regions
251 // in non-contiguous spaces with no boundaries, and should be sub-classed
252 // to support other space types. See ContiguousDCTOC for a sub-class
253 // that works with ContiguousSpaces.
254
255 class DirtyCardToOopClosure: public MemRegionClosureRO {
256 protected:
257 ExtendedOopClosure* _cl;
258 Space* _sp;
259 CardTableModRefBS::PrecisionStyle _precision;
260 HeapWord* _boundary; // If non-NULL, process only non-NULL oops
261 // pointing below boundary.
262 HeapWord* _min_done; // ObjHeadPreciseArray precision requires
263 // a downwards traversal; this is the
264 // lowest location already done (or,
265 // alternatively, the lowest address that
266 // shouldn't be done again. NULL means infinity.)
267 NOT_PRODUCT(HeapWord* _last_bottom;)
268 NOT_PRODUCT(HeapWord* _last_explicit_min_done;)
269
270 // Get the actual top of the area on which the closure will
271 // operate, given where the top is assumed to be (the end of the
272 // memory region passed to do_MemRegion) and where the object
273 // at the top is assumed to start. For example, an object may
274 // start at the top but actually extend past the assumed top,
275 // in which case the top becomes the end of the object.
276 virtual HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj);
277
278 // Walk the given memory region from bottom to (actual) top
279 // looking for objects and applying the oop closure (_cl) to
280 // them. The base implementation of this treats the area as
281 // blocks, where a block may or may not be an object. Sub-
282 // classes should override this to provide more accurate
283 // or possibly more efficient walking.
284 virtual void walk_mem_region(MemRegion mr, HeapWord* bottom, HeapWord* top);
285
286 public:
287 DirtyCardToOopClosure(Space* sp, ExtendedOopClosure* cl,
288 CardTableModRefBS::PrecisionStyle precision,
289 HeapWord* boundary) :
290 _sp(sp), _cl(cl), _precision(precision), _boundary(boundary),
291 _min_done(NULL) {
292 NOT_PRODUCT(_last_bottom = NULL);
293 NOT_PRODUCT(_last_explicit_min_done = NULL);
294 }
295
296 void do_MemRegion(MemRegion mr);
297
298 void set_min_done(HeapWord* min_done) {
299 _min_done = min_done;
300 NOT_PRODUCT(_last_explicit_min_done = _min_done);
301 }
302 #ifndef PRODUCT
303 void set_last_bottom(HeapWord* last_bottom) {
304 _last_bottom = last_bottom;
305 }
306 #endif
307 };
308
309 // A structure to represent a point at which objects are being copied
310 // during compaction.
311 class CompactPoint : public StackObj {
312 public:
313 Generation* gen;
314 CompactibleSpace* space;
315 HeapWord* threshold;
316
317 CompactPoint(Generation* g = NULL) :
318 gen(g), space(NULL), threshold(0) {}
319 };
320
321 // A space that supports compaction operations. This is usually, but not
322 // necessarily, a space that is normally contiguous. But, for example, a
323 // free-list-based space whose normal collection is a mark-sweep without
324 // compaction could still support compaction in full GC's.
325 //
326 // The compaction operations are implemented by the
327 // scan_and_{adjust_pointers,compact,forward} function templates.
328 // The following are, non-virtual, auxiliary functions used by these function templates:
329 // - scan_limit()
330 // - scanned_block_is_obj()
331 // - scanned_block_size()
332 // - adjust_obj_size()
333 // - obj_size()
334 // These functions are to be used exclusively by the scan_and_* function templates,
335 // and must be defined for all (non-abstract) subclasses of CompactibleSpace.
336 //
337 // NOTE: Any subclasses to CompactibleSpace wanting to change/define the behavior
338 // in any of the auxiliary functions must also override the corresponding
339 // prepare_for_compaction/adjust_pointers/compact functions using them.
340 // If not, such changes will not be used or have no effect on the compaction operations.
341 //
342 // This translates to the following dependencies:
343 // Overrides/definitions of
344 // - scan_limit
345 // - scanned_block_is_obj
346 // - scanned_block_size
347 // require override/definition of prepare_for_compaction().
348 // Similar dependencies exist between
349 // - adjust_obj_size and adjust_pointers()
350 // - obj_size and compact().
351 //
352 // Additionally, this also means that changes to block_size() or block_is_obj() that
353 // should be effective during the compaction operations must provide a corresponding
354 // definition of scanned_block_size/scanned_block_is_obj respectively.
355 class CompactibleSpace: public Space {
356 friend class VMStructs;
357 friend class CompactibleFreeListSpace;
358 private:
359 HeapWord* _compaction_top;
360 CompactibleSpace* _next_compaction_space;
361
362 // Auxiliary functions for scan_and_{forward,adjust_pointers,compact} support.
363 inline size_t adjust_obj_size(size_t size) const {
364 return size;
365 }
366
367 inline size_t obj_size(const HeapWord* addr) const {
368 return oop(addr)->size();
369 }
370
371 public:
372 CompactibleSpace() :
373 _compaction_top(NULL), _next_compaction_space(NULL) {}
374
375 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
376 virtual void clear(bool mangle_space);
377
378 // Used temporarily during a compaction phase to hold the value
379 // top should have when compaction is complete.
380 HeapWord* compaction_top() const { return _compaction_top; }
381
382 void set_compaction_top(HeapWord* value) {
383 assert(value == NULL || (value >= bottom() && value <= end()),
384 "should point inside space");
385 _compaction_top = value;
386 }
387
388 // Perform operations on the space needed after a compaction
389 // has been performed.
390 virtual void reset_after_compaction() = 0;
391
392 // Returns the next space (in the current generation) to be compacted in
393 // the global compaction order. Also is used to select the next
394 // space into which to compact.
395
396 virtual CompactibleSpace* next_compaction_space() const {
397 return _next_compaction_space;
398 }
399
400 void set_next_compaction_space(CompactibleSpace* csp) {
401 _next_compaction_space = csp;
402 }
403
404 // MarkSweep support phase2
405
406 // Start the process of compaction of the current space: compute
407 // post-compaction addresses, and insert forwarding pointers. The fields
408 // "cp->gen" and "cp->compaction_space" are the generation and space into
409 // which we are currently compacting. This call updates "cp" as necessary,
410 // and leaves the "compaction_top" of the final value of
411 // "cp->compaction_space" up-to-date. Offset tables may be updated in
412 // this phase as if the final copy had occurred; if so, "cp->threshold"
413 // indicates when the next such action should be taken.
414 virtual void prepare_for_compaction(CompactPoint* cp) = 0;
415 // MarkSweep support phase3
416 virtual void adjust_pointers();
417 // MarkSweep support phase4
418 virtual void compact();
419
420 // The maximum percentage of objects that can be dead in the compacted
421 // live part of a compacted space ("deadwood" support.)
422 virtual size_t allowed_dead_ratio() const { return 0; };
423
424 // Some contiguous spaces may maintain some data structures that should
425 // be updated whenever an allocation crosses a boundary. This function
426 // returns the first such boundary.
427 // (The default implementation returns the end of the space, so the
428 // boundary is never crossed.)
429 virtual HeapWord* initialize_threshold() { return end(); }
430
431 // "q" is an object of the given "size" that should be forwarded;
432 // "cp" names the generation ("gen") and containing "this" (which must
433 // also equal "cp->space"). "compact_top" is where in "this" the
434 // next object should be forwarded to. If there is room in "this" for
435 // the object, insert an appropriate forwarding pointer in "q".
436 // If not, go to the next compaction space (there must
437 // be one, since compaction must succeed -- we go to the first space of
438 // the previous generation if necessary, updating "cp"), reset compact_top
439 // and then forward. In either case, returns the new value of "compact_top".
440 // If the forwarding crosses "cp->threshold", invokes the "cross_threshold"
441 // function of the then-current compaction space, and updates "cp->threshold
442 // accordingly".
443 virtual HeapWord* forward(oop q, size_t size, CompactPoint* cp,
444 HeapWord* compact_top);
445
446 // Return a size with adjustments as required of the space.
447 virtual size_t adjust_object_size_v(size_t size) const { return size; }
448
449 protected:
450 // Used during compaction.
451 HeapWord* _first_dead;
452 HeapWord* _end_of_live;
453
454 // Minimum size of a free block.
455 virtual size_t minimum_free_block_size() const { return 0; }
456
457 // This the function is invoked when an allocation of an object covering
458 // "start" to "end occurs crosses the threshold; returns the next
459 // threshold. (The default implementation does nothing.)
460 virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* the_end) {
461 return end();
462 }
463
464 // Requires "allowed_deadspace_words > 0", that "q" is the start of a
465 // free block of the given "word_len", and that "q", were it an object,
466 // would not move if forwarded. If the size allows, fill the free
467 // block with an object, to prevent excessive compaction. Returns "true"
468 // iff the free region was made deadspace, and modifies
469 // "allowed_deadspace_words" to reflect the number of available deadspace
470 // words remaining after this operation.
471 bool insert_deadspace(size_t& allowed_deadspace_words, HeapWord* q,
472 size_t word_len);
473
474 // Below are template functions for scan_and_* algorithms (avoiding virtual calls).
475 // The space argument should be a subclass of CompactibleSpace, implementing
476 // scan_limit(), scanned_block_is_obj(), and scanned_block_size(),
477 // and possibly also overriding obj_size(), and adjust_obj_size().
478 // These functions should avoid virtual calls whenever possible.
479
480 // Frequently calls adjust_obj_size().
481 template <class SpaceType>
482 static inline void scan_and_adjust_pointers(SpaceType* space);
483
484 // Frequently calls obj_size().
485 template <class SpaceType>
486 static inline void scan_and_compact(SpaceType* space);
487
488 // Frequently calls scanned_block_is_obj() and scanned_block_size().
489 // Requires the scan_limit() function.
490 template <class SpaceType>
491 static inline void scan_and_forward(SpaceType* space, CompactPoint* cp);
492 };
493
494 class GenSpaceMangler;
495
496 // A space in which the free area is contiguous. It therefore supports
497 // faster allocation, and compaction.
498 class ContiguousSpace: public CompactibleSpace {
499 friend class VMStructs;
500 // Allow scan_and_forward function to call (private) overrides for auxiliary functions on this class
501 template <typename SpaceType>
502 friend void CompactibleSpace::scan_and_forward(SpaceType* space, CompactPoint* cp);
503
504 private:
505 // Auxiliary functions for scan_and_forward support.
506 // See comments for CompactibleSpace for more information.
507 inline HeapWord* scan_limit() const {
508 return top();
509 }
510
511 inline bool scanned_block_is_obj(const HeapWord* addr) const {
512 return true; // Always true, since scan_limit is top
513 }
514
515 inline size_t scanned_block_size(const HeapWord* addr) const {
516 return oop(addr)->size();
517 }
518
519 protected:
520 HeapWord* _top;
521 HeapWord* _concurrent_iteration_safe_limit;
522 // A helper for mangling the unused area of the space in debug builds.
523 GenSpaceMangler* _mangler;
524
525 GenSpaceMangler* mangler() { return _mangler; }
526
527 // Allocation helpers (return NULL if full).
528 inline HeapWord* allocate_impl(size_t word_size);
529 inline HeapWord* par_allocate_impl(size_t word_size);
530
531 public:
532 ContiguousSpace();
533 ~ContiguousSpace();
534
535 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
536 virtual void clear(bool mangle_space);
537
538 // Accessors
539 HeapWord* top() const { return _top; }
540 void set_top(HeapWord* value) { _top = value; }
541
542 void set_saved_mark() { _saved_mark_word = top(); }
543 void reset_saved_mark() { _saved_mark_word = bottom(); }
544
545 WaterMark bottom_mark() { return WaterMark(this, bottom()); }
546 WaterMark top_mark() { return WaterMark(this, top()); }
547 WaterMark saved_mark() { return WaterMark(this, saved_mark_word()); }
548 bool saved_mark_at_top() const { return saved_mark_word() == top(); }
549
550 // In debug mode mangle (write it with a particular bit
551 // pattern) the unused part of a space.
552
553 // Used to save the an address in a space for later use during mangling.
554 void set_top_for_allocations(HeapWord* v) PRODUCT_RETURN;
555 // Used to save the space's current top for later use during mangling.
556 void set_top_for_allocations() PRODUCT_RETURN;
557
558 // Mangle regions in the space from the current top up to the
559 // previously mangled part of the space.
560 void mangle_unused_area() PRODUCT_RETURN;
561 // Mangle [top, end)
562 void mangle_unused_area_complete() PRODUCT_RETURN;
563 // Mangle the given MemRegion.
564 void mangle_region(MemRegion mr) PRODUCT_RETURN;
565
566 // Do some sparse checking on the area that should have been mangled.
567 void check_mangled_unused_area(HeapWord* limit) PRODUCT_RETURN;
568 // Check the complete area that should have been mangled.
569 // This code may be NULL depending on the macro DEBUG_MANGLING.
570 void check_mangled_unused_area_complete() PRODUCT_RETURN;
571
572 // Size computations: sizes in bytes.
573 size_t capacity() const { return byte_size(bottom(), end()); }
574 size_t used() const { return byte_size(bottom(), top()); }
575 size_t free() const { return byte_size(top(), end()); }
576
577 virtual bool is_free_block(const HeapWord* p) const;
578
579 // In a contiguous space we have a more obvious bound on what parts
580 // contain objects.
581 MemRegion used_region() const { return MemRegion(bottom(), top()); }
582
583 // Allocation (return NULL if full)
584 virtual HeapWord* allocate(size_t word_size);
585 virtual HeapWord* par_allocate(size_t word_size);
586 HeapWord* allocate_aligned(size_t word_size);
587
588 // Iteration
589 void oop_iterate(ExtendedOopClosure* cl);
590 void object_iterate(ObjectClosure* blk);
591 // For contiguous spaces this method will iterate safely over objects
592 // in the space (i.e., between bottom and top) when at a safepoint.
593 void safe_object_iterate(ObjectClosure* blk);
594
595 // Iterate over as many initialized objects in the space as possible,
596 // calling "cl.do_object_careful" on each. Return NULL if all objects
597 // in the space (at the start of the iteration) were iterated over.
598 // Return an address indicating the extent of the iteration in the
599 // event that the iteration had to return because of finding an
600 // uninitialized object in the space, or if the closure "cl"
601 // signaled early termination.
602 HeapWord* object_iterate_careful(ObjectClosureCareful* cl);
603 HeapWord* concurrent_iteration_safe_limit() {
604 assert(_concurrent_iteration_safe_limit <= top(),
605 "_concurrent_iteration_safe_limit update missed");
606 return _concurrent_iteration_safe_limit;
607 }
608 // changes the safe limit, all objects from bottom() to the new
609 // limit should be properly initialized
610 void set_concurrent_iteration_safe_limit(HeapWord* new_limit) {
611 assert(new_limit <= top(), "uninitialized objects in the safe range");
612 _concurrent_iteration_safe_limit = new_limit;
613 }
614
615
616 #if INCLUDE_ALL_GCS
617 // In support of parallel oop_iterate.
618 #define ContigSpace_PAR_OOP_ITERATE_DECL(OopClosureType, nv_suffix) \
619 void par_oop_iterate(MemRegion mr, OopClosureType* blk);
620
621 ALL_PAR_OOP_ITERATE_CLOSURES(ContigSpace_PAR_OOP_ITERATE_DECL)
622 #undef ContigSpace_PAR_OOP_ITERATE_DECL
623 #endif // INCLUDE_ALL_GCS
624
625 // Compaction support
626 virtual void reset_after_compaction() {
627 assert(compaction_top() >= bottom() && compaction_top() <= end(), "should point inside space");
628 set_top(compaction_top());
629 // set new iteration safe limit
630 set_concurrent_iteration_safe_limit(compaction_top());
631 }
632
633 // Override.
634 DirtyCardToOopClosure* new_dcto_cl(ExtendedOopClosure* cl,
635 CardTableModRefBS::PrecisionStyle precision,
636 HeapWord* boundary = NULL);
637
638 // Apply "blk->do_oop" to the addresses of all reference fields in objects
639 // starting with the _saved_mark_word, which was noted during a generation's
640 // save_marks and is required to denote the head of an object.
641 // Fields in objects allocated by applications of the closure
642 // *are* included in the iteration.
643 // Updates _saved_mark_word to point to just after the last object
644 // iterated over.
645 #define ContigSpace_OOP_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
646 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk);
647
648 ALL_SINCE_SAVE_MARKS_CLOSURES(ContigSpace_OOP_SINCE_SAVE_MARKS_DECL)
649 #undef ContigSpace_OOP_SINCE_SAVE_MARKS_DECL
650
651 // Same as object_iterate, but starting from "mark", which is required
652 // to denote the start of an object. Objects allocated by
653 // applications of the closure *are* included in the iteration.
654 virtual void object_iterate_from(WaterMark mark, ObjectClosure* blk);
655
656 // Very inefficient implementation.
657 virtual HeapWord* block_start_const(const void* p) const;
658 size_t block_size(const HeapWord* p) const;
659 // If a block is in the allocated area, it is an object.
660 bool block_is_obj(const HeapWord* p) const { return p < top(); }
661
662 // Addresses for inlined allocation
663 HeapWord** top_addr() { return &_top; }
664 HeapWord** end_addr() { return &_end; }
665
666 // Overrides for more efficient compaction support.
667 void prepare_for_compaction(CompactPoint* cp);
668
669 // PrintHeapAtGC support.
670 virtual void print_on(outputStream* st) const;
671
672 // Checked dynamic downcasts.
673 virtual ContiguousSpace* toContiguousSpace() {
674 return this;
675 }
676
677 // Debugging
678 virtual void verify() const;
679
680 // Used to increase collection frequency. "factor" of 0 means entire
681 // space.
682 void allocate_temporary_filler(int factor);
683 };
684
685
686 // A dirty card to oop closure that does filtering.
687 // It knows how to filter out objects that are outside of the _boundary.
688 class Filtering_DCTOC : public DirtyCardToOopClosure {
689 protected:
690 // Override.
691 void walk_mem_region(MemRegion mr,
692 HeapWord* bottom, HeapWord* top);
693
694 // Walk the given memory region, from bottom to top, applying
695 // the given oop closure to (possibly) all objects found. The
696 // given oop closure may or may not be the same as the oop
697 // closure with which this closure was created, as it may
698 // be a filtering closure which makes use of the _boundary.
699 // We offer two signatures, so the FilteringClosure static type is
700 // apparent.
701 virtual void walk_mem_region_with_cl(MemRegion mr,
702 HeapWord* bottom, HeapWord* top,
703 ExtendedOopClosure* cl) = 0;
704 virtual void walk_mem_region_with_cl(MemRegion mr,
705 HeapWord* bottom, HeapWord* top,
706 FilteringClosure* cl) = 0;
707
708 public:
709 Filtering_DCTOC(Space* sp, ExtendedOopClosure* cl,
710 CardTableModRefBS::PrecisionStyle precision,
711 HeapWord* boundary) :
712 DirtyCardToOopClosure(sp, cl, precision, boundary) {}
713 };
714
715 // A dirty card to oop closure for contiguous spaces
716 // (ContiguousSpace and sub-classes).
717 // It is a FilteringClosure, as defined above, and it knows:
718 //
719 // 1. That the actual top of any area in a memory region
720 // contained by the space is bounded by the end of the contiguous
721 // region of the space.
722 // 2. That the space is really made up of objects and not just
723 // blocks.
724
725 class ContiguousSpaceDCTOC : public Filtering_DCTOC {
726 protected:
727 // Overrides.
728 HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj);
729
730 virtual void walk_mem_region_with_cl(MemRegion mr,
731 HeapWord* bottom, HeapWord* top,
732 ExtendedOopClosure* cl);
733 virtual void walk_mem_region_with_cl(MemRegion mr,
734 HeapWord* bottom, HeapWord* top,
735 FilteringClosure* cl);
736
737 public:
738 ContiguousSpaceDCTOC(ContiguousSpace* sp, ExtendedOopClosure* cl,
739 CardTableModRefBS::PrecisionStyle precision,
740 HeapWord* boundary) :
741 Filtering_DCTOC(sp, cl, precision, boundary)
742 {}
743 };
744
745 // A ContigSpace that Supports an efficient "block_start" operation via
746 // a BlockOffsetArray (whose BlockOffsetSharedArray may be shared with
747 // other spaces.) This is the abstract base class for old generation
748 // (tenured) spaces.
749
750 class OffsetTableContigSpace: public ContiguousSpace {
751 friend class VMStructs;
752 protected:
753 BlockOffsetArrayContigSpace _offsets;
754 Mutex _par_alloc_lock;
755
756 public:
757 // Constructor
758 OffsetTableContigSpace(BlockOffsetSharedArray* sharedOffsetArray,
759 MemRegion mr);
760
761 void set_bottom(HeapWord* value);
762 void set_end(HeapWord* value);
763
764 void clear(bool mangle_space);
765
766 inline HeapWord* block_start_const(const void* p) const;
767
768 // Add offset table update.
769 virtual inline HeapWord* allocate(size_t word_size);
770 inline HeapWord* par_allocate(size_t word_size);
771
772 // MarkSweep support phase3
773 virtual HeapWord* initialize_threshold();
774 virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* end);
775
776 virtual void print_on(outputStream* st) const;
777
778 // Debugging
779 void verify() const;
780 };
781
782
783 // Class TenuredSpace is used by TenuredGeneration
784
785 class TenuredSpace: public OffsetTableContigSpace {
786 friend class VMStructs;
787 protected:
788 // Mark sweep support
789 size_t allowed_dead_ratio() const;
790 public:
791 // Constructor
792 TenuredSpace(BlockOffsetSharedArray* sharedOffsetArray,
793 MemRegion mr) :
794 OffsetTableContigSpace(sharedOffsetArray, mr) {}
795 };
796 #endif // SHARE_VM_MEMORY_SPACE_HPP