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