1 /*
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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 // Here's the Space hierarchy:
45 //
46 // - Space -- an abstract base class describing a heap area
47 // - CompactibleSpace -- a space supporting compaction
48 // - CompactibleFreeListSpace -- (used for CMS generation)
49 // - G1OffsetTableContigSpace -- G1 version of OffsetTableContigSpace
50 // - ContiguousSpace -- a compactible space in which all free space
51 // is contiguous
52 // - EdenSpace -- contiguous space used as nursery
53 // - ConcEdenSpace -- contiguous space with a 'soft end safe' allocation
54 // - OffsetTableContigSpace -- contiguous space with a block offset array
55 // that allows "fast" block_start calls
56 // - TenuredSpace -- (used for TenuredGeneration)
57
58 // Forward decls.
59 class Space;
60 class BlockOffsetArray;
61 class BlockOffsetArrayContigSpace;
62 class Generation;
63 class CompactibleSpace;
64 class BlockOffsetTable;
65 class GenRemSet;
66 class CardTableRS;
67 class DirtyCardToOopClosure;
68
69 // A Space describes a heap area. Class Space is an abstract
70 // base class.
71 //
72 // Space supports allocation, size computation and GC support is provided.
73 //
74 // Invariant: bottom() and end() are on page_size boundaries and
75 // bottom() <= top() <= end()
76 // top() is inclusive and end() is exclusive.
77
78 class Space: public CHeapObj<mtGC> {
79 friend class VMStructs;
80 protected:
81 HeapWord* _bottom;
82 HeapWord* _end;
83
84 // Used in support of save_marks()
85 HeapWord* _saved_mark_word;
86
87 MemRegionClosure* _preconsumptionDirtyCardClosure;
88
89 // A sequential tasks done structure. This supports
90 // parallel GC, where we have threads dynamically
91 // claiming sub-tasks from a larger parallel task.
92 SequentialSubTasksDone _par_seq_tasks;
93
94 Space():
95 _bottom(NULL), _end(NULL), _preconsumptionDirtyCardClosure(NULL) { }
96
97 public:
98 // Accessors
99 HeapWord* bottom() const { return _bottom; }
100 HeapWord* end() const { return _end; }
101 virtual void set_bottom(HeapWord* value) { _bottom = value; }
102 virtual void set_end(HeapWord* value) { _end = value; }
103
104 virtual HeapWord* saved_mark_word() const { return _saved_mark_word; }
105
106 void set_saved_mark_word(HeapWord* p) { _saved_mark_word = p; }
107
108 // Returns true if this object has been allocated since a
109 // generation's "save_marks" call.
110 virtual bool obj_allocated_since_save_marks(const oop obj) const {
111 return (HeapWord*)obj >= saved_mark_word();
112 }
113
114 MemRegionClosure* preconsumptionDirtyCardClosure() const {
115 return _preconsumptionDirtyCardClosure;
116 }
117 void setPreconsumptionDirtyCardClosure(MemRegionClosure* cl) {
118 _preconsumptionDirtyCardClosure = cl;
119 }
120
121 // Returns a subregion of the space containing only the allocated objects in
122 // the space.
123 virtual MemRegion used_region() const = 0;
124
125 // Returns a region that is guaranteed to contain (at least) all objects
126 // allocated at the time of the last call to "save_marks". If the space
127 // initializes its DirtyCardToOopClosure's specifying the "contig" option
128 // (that is, if the space is contiguous), then this region must contain only
129 // such objects: the memregion will be from the bottom of the region to the
130 // saved mark. Otherwise, the "obj_allocated_since_save_marks" method of
131 // the space must distinguish between objects in the region allocated before
132 // and after the call to save marks.
133 MemRegion used_region_at_save_marks() const {
134 return MemRegion(bottom(), saved_mark_word());
135 }
136
137 // Initialization.
138 // "initialize" should be called once on a space, before it is used for
139 // any purpose. The "mr" arguments gives the bounds of the space, and
140 // the "clear_space" argument should be true unless the memory in "mr" is
141 // known to be zeroed.
142 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
143
144 // The "clear" method must be called on a region that may have
145 // had allocation performed in it, but is now to be considered empty.
146 virtual void clear(bool mangle_space);
147
148 // For detecting GC bugs. Should only be called at GC boundaries, since
149 // some unused space may be used as scratch space during GC's.
150 // Default implementation does nothing. We also call this when expanding
151 // a space to satisfy an allocation request. See bug #4668531
152 virtual void mangle_unused_area() {}
153 virtual void mangle_unused_area_complete() {}
154 virtual void mangle_region(MemRegion mr) {}
155
156 // Testers
157 bool is_empty() const { return used() == 0; }
158 bool not_empty() const { return used() > 0; }
159
160 // Returns true iff the given the space contains the
161 // given address as part of an allocated object. For
162 // certain kinds of spaces, this might be a potentially
163 // expensive operation. To prevent performance problems
164 // on account of its inadvertent use in product jvm's,
165 // we restrict its use to assertion checks only.
166 bool is_in(const void* p) const {
167 return used_region().contains(p);
168 }
169
170 // Returns true iff the given reserved memory of the space contains the
171 // given address.
172 bool is_in_reserved(const void* p) const { return _bottom <= p && p < _end; }
173
174 // Returns true iff the given block is not allocated.
175 virtual bool is_free_block(const HeapWord* p) const = 0;
176
177 // Test whether p is double-aligned
178 static bool is_aligned(void* p) {
179 return ((intptr_t)p & (sizeof(double)-1)) == 0;
180 }
181
182 // Size computations. Sizes are in bytes.
183 size_t capacity() const { return byte_size(bottom(), end()); }
184 virtual size_t used() const = 0;
185 virtual size_t free() const = 0;
186
187 // Iterate over all the ref-containing fields of all objects in the
188 // space, calling "cl.do_oop" on each. Fields in objects allocated by
189 // applications of the closure are not included in the iteration.
190 virtual void oop_iterate(ExtendedOopClosure* cl);
191
192 // Iterate over all objects in the space, calling "cl.do_object" on
193 // each. Objects allocated by applications of the closure are not
194 // included in the iteration.
195 virtual void object_iterate(ObjectClosure* blk) = 0;
196 // Similar to object_iterate() except only iterates over
197 // objects whose internal references point to objects in the space.
198 virtual void safe_object_iterate(ObjectClosure* blk) = 0;
199
200 // Create and return a new dirty card to oop closure. Can be
201 // overridden to return the appropriate type of closure
202 // depending on the type of space in which the closure will
203 // operate. ResourceArea allocated.
204 virtual DirtyCardToOopClosure* new_dcto_cl(ExtendedOopClosure* cl,
205 CardTableModRefBS::PrecisionStyle precision,
206 HeapWord* boundary = NULL);
207
208 // If "p" is in the space, returns the address of the start of the
209 // "block" that contains "p". We say "block" instead of "object" since
210 // some heaps may not pack objects densely; a chunk may either be an
211 // object or a non-object. If "p" is not in the space, return NULL.
212 virtual HeapWord* block_start_const(const void* p) const = 0;
213
214 // The non-const version may have benevolent side effects on the data
215 // structure supporting these calls, possibly speeding up future calls.
216 // The default implementation, however, is simply to call the const
217 // version.
218 inline virtual HeapWord* block_start(const void* p);
219
220 // Requires "addr" to be the start of a chunk, and returns its size.
221 // "addr + size" is required to be the start of a new chunk, or the end
222 // of the active area of the heap.
223 virtual size_t block_size(const HeapWord* addr) const = 0;
224
225 // Requires "addr" to be the start of a block, and returns "TRUE" iff
226 // the block is an object.
227 virtual bool block_is_obj(const HeapWord* addr) const = 0;
228
229 // Requires "addr" to be the start of a block, and returns "TRUE" iff
230 // the block is an object and the object is alive.
231 virtual bool obj_is_alive(const HeapWord* addr) const;
232
233 // Allocation (return NULL if full). Assumes the caller has established
234 // mutually exclusive access to the space.
235 virtual HeapWord* allocate(size_t word_size) = 0;
236
237 // Allocation (return NULL if full). Enforces mutual exclusion internally.
238 virtual HeapWord* par_allocate(size_t word_size) = 0;
239
240 // Mark-sweep-compact support: all spaces can update pointers to objects
241 // moving as a part of compaction.
242 virtual void adjust_pointers();
243
244 // PrintHeapAtGC support
245 virtual void print() const;
246 virtual void print_on(outputStream* st) const;
247 virtual void print_short() const;
248 virtual void print_short_on(outputStream* st) const;
249
250
251 // Accessor for parallel sequential tasks.
252 SequentialSubTasksDone* par_seq_tasks() { return &_par_seq_tasks; }
253
254 // IF "this" is a ContiguousSpace, return it, else return NULL.
255 virtual ContiguousSpace* toContiguousSpace() {
256 return NULL;
257 }
258
259 // Debugging
260 virtual void verify() const = 0;
261 };
262
263 // A MemRegionClosure (ResourceObj) whose "do_MemRegion" function applies an
264 // OopClosure to (the addresses of) all the ref-containing fields that could
265 // be modified by virtue of the given MemRegion being dirty. (Note that
266 // because of the imprecise nature of the write barrier, this may iterate
267 // over oops beyond the region.)
268 // This base type for dirty card to oop closures handles memory regions
269 // in non-contiguous spaces with no boundaries, and should be sub-classed
270 // to support other space types. See ContiguousDCTOC for a sub-class
271 // that works with ContiguousSpaces.
272
273 class DirtyCardToOopClosure: public MemRegionClosureRO {
274 protected:
275 ExtendedOopClosure* _cl;
276 Space* _sp;
277 CardTableModRefBS::PrecisionStyle _precision;
278 HeapWord* _boundary; // If non-NULL, process only non-NULL oops
279 // pointing below boundary.
280 HeapWord* _min_done; // ObjHeadPreciseArray precision requires
281 // a downwards traversal; this is the
282 // lowest location already done (or,
283 // alternatively, the lowest address that
284 // shouldn't be done again. NULL means infinity.)
285 NOT_PRODUCT(HeapWord* _last_bottom;)
286 NOT_PRODUCT(HeapWord* _last_explicit_min_done;)
287
288 // Get the actual top of the area on which the closure will
289 // operate, given where the top is assumed to be (the end of the
290 // memory region passed to do_MemRegion) and where the object
291 // at the top is assumed to start. For example, an object may
292 // start at the top but actually extend past the assumed top,
293 // in which case the top becomes the end of the object.
294 virtual HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj);
295
296 // Walk the given memory region from bottom to (actual) top
297 // looking for objects and applying the oop closure (_cl) to
298 // them. The base implementation of this treats the area as
299 // blocks, where a block may or may not be an object. Sub-
300 // classes should override this to provide more accurate
301 // or possibly more efficient walking.
302 virtual void walk_mem_region(MemRegion mr, HeapWord* bottom, HeapWord* top);
303
304 public:
305 DirtyCardToOopClosure(Space* sp, ExtendedOopClosure* cl,
306 CardTableModRefBS::PrecisionStyle precision,
307 HeapWord* boundary) :
308 _sp(sp), _cl(cl), _precision(precision), _boundary(boundary),
309 _min_done(NULL) {
310 NOT_PRODUCT(_last_bottom = NULL);
311 NOT_PRODUCT(_last_explicit_min_done = NULL);
312 }
313
314 void do_MemRegion(MemRegion mr);
315
316 void set_min_done(HeapWord* min_done) {
317 _min_done = min_done;
318 NOT_PRODUCT(_last_explicit_min_done = _min_done);
319 }
320 #ifndef PRODUCT
321 void set_last_bottom(HeapWord* last_bottom) {
322 _last_bottom = last_bottom;
323 }
324 #endif
325 };
326
327 // A structure to represent a point at which objects are being copied
328 // during compaction.
329 class CompactPoint : public StackObj {
330 public:
331 Generation* gen;
332 CompactibleSpace* space;
333 HeapWord* threshold;
334
335 CompactPoint(Generation* _gen) :
336 gen(_gen), space(NULL), threshold(0) {}
337 };
338
339
340 // A space that supports compaction operations. This is usually, but not
341 // necessarily, a space that is normally contiguous. But, for example, a
342 // free-list-based space whose normal collection is a mark-sweep without
343 // compaction could still support compaction in full GC's.
344
345 class CompactibleSpace: public Space {
346 friend class VMStructs;
347 friend class CompactibleFreeListSpace;
348 private:
349 HeapWord* _compaction_top;
350 CompactibleSpace* _next_compaction_space;
351
352 public:
353 CompactibleSpace() :
354 _compaction_top(NULL), _next_compaction_space(NULL) {}
355
356 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
357 virtual void clear(bool mangle_space);
358
359 // Used temporarily during a compaction phase to hold the value
360 // top should have when compaction is complete.
361 HeapWord* compaction_top() const { return _compaction_top; }
362
363 void set_compaction_top(HeapWord* value) {
364 assert(value == NULL || (value >= bottom() && value <= end()),
365 "should point inside space");
366 _compaction_top = value;
367 }
368
369 // Perform operations on the space needed after a compaction
370 // has been performed.
371 virtual void reset_after_compaction() = 0;
372
373 // Returns the next space (in the current generation) to be compacted in
374 // the global compaction order. Also is used to select the next
375 // space into which to compact.
376
377 virtual CompactibleSpace* next_compaction_space() const {
378 return _next_compaction_space;
379 }
380
381 void set_next_compaction_space(CompactibleSpace* csp) {
382 _next_compaction_space = csp;
383 }
384
385 // MarkSweep support phase2
386
387 // Start the process of compaction of the current space: compute
388 // post-compaction addresses, and insert forwarding pointers. The fields
389 // "cp->gen" and "cp->compaction_space" are the generation and space into
390 // which we are currently compacting. This call updates "cp" as necessary,
391 // and leaves the "compaction_top" of the final value of
392 // "cp->compaction_space" up-to-date. Offset tables may be updated in
393 // this phase as if the final copy had occurred; if so, "cp->threshold"
394 // indicates when the next such action should be taken.
395 virtual void prepare_for_compaction(CompactPoint* cp) = 0;
396 // MarkSweep support phase3
397 virtual void adjust_pointers();
398 // MarkSweep support phase4
399 virtual void compact();
400
401 // The maximum percentage of objects that can be dead in the compacted
402 // live part of a compacted space ("deadwood" support.)
403 virtual size_t allowed_dead_ratio() const { return 0; };
404
405 // Some contiguous spaces may maintain some data structures that should
406 // be updated whenever an allocation crosses a boundary. This function
407 // returns the first such boundary.
408 // (The default implementation returns the end of the space, so the
409 // boundary is never crossed.)
410 virtual HeapWord* initialize_threshold() { return end(); }
411
412 // "q" is an object of the given "size" that should be forwarded;
413 // "cp" names the generation ("gen") and containing "this" (which must
414 // also equal "cp->space"). "compact_top" is where in "this" the
415 // next object should be forwarded to. If there is room in "this" for
416 // the object, insert an appropriate forwarding pointer in "q".
417 // If not, go to the next compaction space (there must
418 // be one, since compaction must succeed -- we go to the first space of
419 // the previous generation if necessary, updating "cp"), reset compact_top
420 // and then forward. In either case, returns the new value of "compact_top".
421 // If the forwarding crosses "cp->threshold", invokes the "cross_threshold"
422 // function of the then-current compaction space, and updates "cp->threshold
423 // accordingly".
424 virtual HeapWord* forward(oop q, size_t size, CompactPoint* cp,
425 HeapWord* compact_top);
426
427 // Return a size with adjustments as required of the space.
428 virtual size_t adjust_object_size_v(size_t size) const { return size; }
429
430 // Functions for scan_and_{forward,adjust_pointers,compact} support.
431 inline bool scanned_block_is_obj(const HeapWord* addr) const {
432 // Perform virtual call. This is currently not a problem since this
433 // function is only used in an assert (from scan_and_adjust_pointers).
434 return block_is_obj(addr);
435 }
436
437 inline size_t adjust_obj_size(size_t size) const {
438 return size;
439 }
440
441 inline size_t obj_size(const HeapWord* addr) const {
442 return oop(addr)->size();
443 }
444
445 protected:
446 // Used during compaction.
447 HeapWord* _first_dead;
448 HeapWord* _end_of_live;
449
450 // Minimum size of a free block.
451 virtual size_t minimum_free_block_size() const { return 0; }
452
453 // This the function is invoked when an allocation of an object covering
454 // "start" to "end occurs crosses the threshold; returns the next
455 // threshold. (The default implementation does nothing.)
456 virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* the_end) {
457 return end();
458 }
459
460 // Requires "allowed_deadspace_words > 0", that "q" is the start of a
461 // free block of the given "word_len", and that "q", were it an object,
462 // would not move if forwarded. If the size allows, fill the free
463 // block with an object, to prevent excessive compaction. Returns "true"
464 // iff the free region was made deadspace, and modifies
465 // "allowed_deadspace_words" to reflect the number of available deadspace
466 // words remaining after this operation.
467 bool insert_deadspace(size_t& allowed_deadspace_words, HeapWord* q,
468 size_t word_len);
469
470 // Below are template functions for scan_and_* algorithms (avoiding virtual calls).
471 // The space argument should be a subclass of CompactibleSpace, implementing
472 // scan_limit(), scanned_block_is_obj(), and scanned_block_size(),
473 // and possibly also overriding obj_size(), and adjust_obj_size().
474 // These functions should avoid virtual calls whenever possible.
475
476 // Frequently calls adjust_obj_size(). (Asserts on scanned_block_is_obj().)
477 template <class SpaceType>
478 static inline void scan_and_adjust_pointers(SpaceType* space);
479
480 // Frequently calls obj_size().
481 template <class SpaceType>
482 static inline void scan_and_compact(SpaceType* space);
483
484 // Frequently calls scanned_block_is_obj() and scanned_block_size().
485 // Requires the scan_limit() function.
486 template <class SpaceType>
487 static inline void scan_and_forward(SpaceType* space, CompactPoint* cp);
488 };
489
490 class GenSpaceMangler;
491
492 // A space in which the free area is contiguous. It therefore supports
493 // faster allocation, and compaction.
494 class ContiguousSpace: public CompactibleSpace {
495 friend class OneContigSpaceCardGeneration;
496 friend class VMStructs;
497 protected:
498 HeapWord* _top;
499 HeapWord* _concurrent_iteration_safe_limit;
500 // A helper for mangling the unused area of the space in debug builds.
501 GenSpaceMangler* _mangler;
502
503 GenSpaceMangler* mangler() { return _mangler; }
504
505 // Allocation helpers (return NULL if full).
506 inline HeapWord* allocate_impl(size_t word_size, HeapWord* end_value);
507 inline HeapWord* par_allocate_impl(size_t word_size, HeapWord* end_value);
508
509 public:
510 ContiguousSpace();
511 ~ContiguousSpace();
512
513 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
514 virtual void clear(bool mangle_space);
515
516 // Accessors
517 HeapWord* top() const { return _top; }
518 void set_top(HeapWord* value) { _top = value; }
519
520 void set_saved_mark() { _saved_mark_word = top(); }
521 void reset_saved_mark() { _saved_mark_word = bottom(); }
522
523 WaterMark bottom_mark() { return WaterMark(this, bottom()); }
524 WaterMark top_mark() { return WaterMark(this, top()); }
525 WaterMark saved_mark() { return WaterMark(this, saved_mark_word()); }
526 bool saved_mark_at_top() const { return saved_mark_word() == top(); }
527
528 // In debug mode mangle (write it with a particular bit
529 // pattern) the unused part of a space.
530
531 // Used to save the an address in a space for later use during mangling.
532 void set_top_for_allocations(HeapWord* v) PRODUCT_RETURN;
533 // Used to save the space's current top for later use during mangling.
534 void set_top_for_allocations() PRODUCT_RETURN;
535
536 // Mangle regions in the space from the current top up to the
537 // previously mangled part of the space.
538 void mangle_unused_area() PRODUCT_RETURN;
539 // Mangle [top, end)
540 void mangle_unused_area_complete() PRODUCT_RETURN;
541 // Mangle the given MemRegion.
542 void mangle_region(MemRegion mr) PRODUCT_RETURN;
543
544 // Do some sparse checking on the area that should have been mangled.
545 void check_mangled_unused_area(HeapWord* limit) PRODUCT_RETURN;
546 // Check the complete area that should have been mangled.
547 // This code may be NULL depending on the macro DEBUG_MANGLING.
548 void check_mangled_unused_area_complete() PRODUCT_RETURN;
549
550 // Size computations: sizes in bytes.
551 size_t capacity() const { return byte_size(bottom(), end()); }
552 size_t used() const { return byte_size(bottom(), top()); }
553 size_t free() const { return byte_size(top(), end()); }
554
555 virtual bool is_free_block(const HeapWord* p) const;
556
557 // In a contiguous space we have a more obvious bound on what parts
558 // contain objects.
559 MemRegion used_region() const { return MemRegion(bottom(), top()); }
560
561 // Allocation (return NULL if full)
562 virtual HeapWord* allocate(size_t word_size);
563 virtual HeapWord* par_allocate(size_t word_size);
564 HeapWord* allocate_aligned(size_t word_size);
565
566 // Iteration
567 void oop_iterate(ExtendedOopClosure* cl);
568 void object_iterate(ObjectClosure* blk);
569 // For contiguous spaces this method will iterate safely over objects
570 // in the space (i.e., between bottom and top) when at a safepoint.
571 void safe_object_iterate(ObjectClosure* blk);
572
573 // Iterate over as many initialized objects in the space as possible,
574 // calling "cl.do_object_careful" on each. Return NULL if all objects
575 // in the space (at the start of the iteration) were iterated over.
576 // Return an address indicating the extent of the iteration in the
577 // event that the iteration had to return because of finding an
578 // uninitialized object in the space, or if the closure "cl"
579 // signaled early termination.
580 HeapWord* object_iterate_careful(ObjectClosureCareful* cl);
581 HeapWord* concurrent_iteration_safe_limit() {
582 assert(_concurrent_iteration_safe_limit <= top(),
583 "_concurrent_iteration_safe_limit update missed");
584 return _concurrent_iteration_safe_limit;
585 }
586 // changes the safe limit, all objects from bottom() to the new
587 // limit should be properly initialized
588 void set_concurrent_iteration_safe_limit(HeapWord* new_limit) {
589 assert(new_limit <= top(), "uninitialized objects in the safe range");
590 _concurrent_iteration_safe_limit = new_limit;
591 }
592
593
594 #if INCLUDE_ALL_GCS
595 // In support of parallel oop_iterate.
596 #define ContigSpace_PAR_OOP_ITERATE_DECL(OopClosureType, nv_suffix) \
597 void par_oop_iterate(MemRegion mr, OopClosureType* blk);
598
599 ALL_PAR_OOP_ITERATE_CLOSURES(ContigSpace_PAR_OOP_ITERATE_DECL)
600 #undef ContigSpace_PAR_OOP_ITERATE_DECL
601 #endif // INCLUDE_ALL_GCS
602
603 // Compaction support
604 virtual void reset_after_compaction() {
605 assert(compaction_top() >= bottom() && compaction_top() <= end(), "should point inside space");
606 set_top(compaction_top());
607 // set new iteration safe limit
608 set_concurrent_iteration_safe_limit(compaction_top());
609 }
610
611 // Override.
612 DirtyCardToOopClosure* new_dcto_cl(ExtendedOopClosure* cl,
613 CardTableModRefBS::PrecisionStyle precision,
614 HeapWord* boundary = NULL);
615
616 // Apply "blk->do_oop" to the addresses of all reference fields in objects
617 // starting with the _saved_mark_word, which was noted during a generation's
618 // save_marks and is required to denote the head of an object.
619 // Fields in objects allocated by applications of the closure
620 // *are* included in the iteration.
621 // Updates _saved_mark_word to point to just after the last object
622 // iterated over.
623 #define ContigSpace_OOP_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
624 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk);
625
626 ALL_SINCE_SAVE_MARKS_CLOSURES(ContigSpace_OOP_SINCE_SAVE_MARKS_DECL)
627 #undef ContigSpace_OOP_SINCE_SAVE_MARKS_DECL
628
629 // Same as object_iterate, but starting from "mark", which is required
630 // to denote the start of an object. Objects allocated by
631 // applications of the closure *are* included in the iteration.
632 virtual void object_iterate_from(WaterMark mark, ObjectClosure* blk);
633
634 // Very inefficient implementation.
635 virtual HeapWord* block_start_const(const void* p) const;
636 size_t block_size(const HeapWord* p) const;
637 // If a block is in the allocated area, it is an object.
638 bool block_is_obj(const HeapWord* p) const { return p < top(); }
639
640 // Addresses for inlined allocation
641 HeapWord** top_addr() { return &_top; }
642 HeapWord** end_addr() { return &_end; }
643
644 // Overrides for more efficient compaction support.
645 void prepare_for_compaction(CompactPoint* cp);
646
647 // PrintHeapAtGC support.
648 virtual void print_on(outputStream* st) const;
649
650 // Checked dynamic downcasts.
651 virtual ContiguousSpace* toContiguousSpace() {
652 return this;
653 }
654
655 // Debugging
656 virtual void verify() const;
657
658 // Used to increase collection frequency. "factor" of 0 means entire
659 // space.
660 void allocate_temporary_filler(int factor);
661
662 // Functions for scan_and_{forward,adjust_pointers,compact} support.
663 inline HeapWord* scan_limit() const {
664 return top();
665 }
666
667 inline bool scanned_block_is_obj(const HeapWord* addr) const {
668 return true; // Always true, since scan_limit is top
669 }
670
671 inline size_t scanned_block_size(const HeapWord* addr) const {
672 return oop(addr)->size();
673 }
674 };
675
676
677 // A dirty card to oop closure that does filtering.
678 // It knows how to filter out objects that are outside of the _boundary.
679 class Filtering_DCTOC : public DirtyCardToOopClosure {
680 protected:
681 // Override.
682 void walk_mem_region(MemRegion mr,
683 HeapWord* bottom, HeapWord* top);
684
685 // Walk the given memory region, from bottom to top, applying
686 // the given oop closure to (possibly) all objects found. The
687 // given oop closure may or may not be the same as the oop
688 // closure with which this closure was created, as it may
689 // be a filtering closure which makes use of the _boundary.
690 // We offer two signatures, so the FilteringClosure static type is
691 // apparent.
692 virtual void walk_mem_region_with_cl(MemRegion mr,
693 HeapWord* bottom, HeapWord* top,
694 ExtendedOopClosure* cl) = 0;
695 virtual void walk_mem_region_with_cl(MemRegion mr,
696 HeapWord* bottom, HeapWord* top,
697 FilteringClosure* cl) = 0;
698
699 public:
700 Filtering_DCTOC(Space* sp, ExtendedOopClosure* cl,
701 CardTableModRefBS::PrecisionStyle precision,
702 HeapWord* boundary) :
703 DirtyCardToOopClosure(sp, cl, precision, boundary) {}
704 };
705
706 // A dirty card to oop closure for contiguous spaces
707 // (ContiguousSpace and sub-classes).
708 // It is a FilteringClosure, as defined above, and it knows:
709 //
710 // 1. That the actual top of any area in a memory region
711 // contained by the space is bounded by the end of the contiguous
712 // region of the space.
713 // 2. That the space is really made up of objects and not just
714 // blocks.
715
716 class ContiguousSpaceDCTOC : public Filtering_DCTOC {
717 protected:
718 // Overrides.
719 HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj);
720
721 virtual void walk_mem_region_with_cl(MemRegion mr,
722 HeapWord* bottom, HeapWord* top,
723 ExtendedOopClosure* cl);
724 virtual void walk_mem_region_with_cl(MemRegion mr,
725 HeapWord* bottom, HeapWord* top,
726 FilteringClosure* cl);
727
728 public:
729 ContiguousSpaceDCTOC(ContiguousSpace* sp, ExtendedOopClosure* cl,
730 CardTableModRefBS::PrecisionStyle precision,
731 HeapWord* boundary) :
732 Filtering_DCTOC(sp, cl, precision, boundary)
733 {}
734 };
735
736
737 // Class EdenSpace describes eden-space in new generation.
738
739 class DefNewGeneration;
740
741 class EdenSpace : public ContiguousSpace {
742 friend class VMStructs;
743 private:
744 DefNewGeneration* _gen;
745
746 // _soft_end is used as a soft limit on allocation. As soft limits are
747 // reached, the slow-path allocation code can invoke other actions and then
748 // adjust _soft_end up to a new soft limit or to end().
749 HeapWord* _soft_end;
750
751 public:
752 EdenSpace(DefNewGeneration* gen) :
753 _gen(gen), _soft_end(NULL) {}
754
755 // Get/set just the 'soft' limit.
756 HeapWord* soft_end() { return _soft_end; }
757 HeapWord** soft_end_addr() { return &_soft_end; }
758 void set_soft_end(HeapWord* value) { _soft_end = value; }
759
760 // Override.
761 void clear(bool mangle_space);
762
763 // Set both the 'hard' and 'soft' limits (_end and _soft_end).
764 void set_end(HeapWord* value) {
765 set_soft_end(value);
766 ContiguousSpace::set_end(value);
767 }
768
769 // Allocation (return NULL if full)
770 HeapWord* allocate(size_t word_size);
771 HeapWord* par_allocate(size_t word_size);
772 };
773
774 // Class ConcEdenSpace extends EdenSpace for the sake of safe
775 // allocation while soft-end is being modified concurrently
776
777 class ConcEdenSpace : public EdenSpace {
778 public:
779 ConcEdenSpace(DefNewGeneration* gen) : EdenSpace(gen) { }
780
781 // Allocation (return NULL if full)
782 HeapWord* par_allocate(size_t word_size);
783 };
784
785
786 // A ContigSpace that Supports an efficient "block_start" operation via
787 // a BlockOffsetArray (whose BlockOffsetSharedArray may be shared with
788 // other spaces.) This is the abstract base class for old generation
789 // (tenured) spaces.
790
791 class OffsetTableContigSpace: public ContiguousSpace {
792 friend class VMStructs;
793 protected:
794 BlockOffsetArrayContigSpace _offsets;
795 Mutex _par_alloc_lock;
796
797 public:
798 // Constructor
799 OffsetTableContigSpace(BlockOffsetSharedArray* sharedOffsetArray,
800 MemRegion mr);
801
802 void set_bottom(HeapWord* value);
803 void set_end(HeapWord* value);
804
805 void clear(bool mangle_space);
806
807 inline HeapWord* block_start_const(const void* p) const;
808
809 // Add offset table update.
810 virtual inline HeapWord* allocate(size_t word_size);
811 inline HeapWord* par_allocate(size_t word_size);
812
813 // MarkSweep support phase3
814 virtual HeapWord* initialize_threshold();
815 virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* end);
816
817 virtual void print_on(outputStream* st) const;
818
819 // Debugging
820 void verify() const;
821 };
822
823
824 // Class TenuredSpace is used by TenuredGeneration
825
826 class TenuredSpace: public OffsetTableContigSpace {
827 friend class VMStructs;
828 protected:
829 // Mark sweep support
830 size_t allowed_dead_ratio() const;
831 public:
832 // Constructor
833 TenuredSpace(BlockOffsetSharedArray* sharedOffsetArray,
834 MemRegion mr) :
835 OffsetTableContigSpace(sharedOffsetArray, mr) {}
836 };
837 #endif // SHARE_VM_MEMORY_SPACE_HPP