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() : gen(NULL), space(NULL), threshold(0) {}
335
336 CompactPoint(Generation* _gen, CompactibleSpace* _space,
337 HeapWord* _threshold) :
338 gen(_gen), space(_space), threshold(_threshold) {}
339 };
340
341
342 // A space that supports compaction operations. This is usually, but not
343 // necessarily, a space that is normally contiguous. But, for example, a
344 // free-list-based space whose normal collection is a mark-sweep without
345 // compaction could still support compaction in full GC's.
346
347 class CompactibleSpace: public Space {
348 friend class VMStructs;
349 friend class CompactibleFreeListSpace;
350 private:
351 HeapWord* _compaction_top;
352 CompactibleSpace* _next_compaction_space;
353
354 public:
355 CompactibleSpace() :
356 _compaction_top(NULL), _next_compaction_space(NULL) {}
357
358 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
359 virtual void clear(bool mangle_space);
360
361 // Used temporarily during a compaction phase to hold the value
362 // top should have when compaction is complete.
363 HeapWord* compaction_top() const { return _compaction_top; }
364
365 void set_compaction_top(HeapWord* value) {
366 assert(value == NULL || (value >= bottom() && value <= end()),
367 "should point inside space");
368 _compaction_top = value;
369 }
370
371 // Perform operations on the space needed after a compaction
372 // has been performed.
373 virtual void reset_after_compaction() = 0;
374
375 // Returns the next space (in the current generation) to be compacted in
376 // the global compaction order. Also is used to select the next
377 // space into which to compact.
378
379 virtual CompactibleSpace* next_compaction_space() const {
380 return _next_compaction_space;
381 }
382
383 void set_next_compaction_space(CompactibleSpace* csp) {
384 _next_compaction_space = csp;
385 }
386
387 // MarkSweep support phase2
388
389 // Start the process of compaction of the current space: compute
390 // post-compaction addresses, and insert forwarding pointers. The fields
391 // "cp->gen" and "cp->compaction_space" are the generation and space into
392 // which we are currently compacting. This call updates "cp" as necessary,
393 // and leaves the "compaction_top" of the final value of
394 // "cp->compaction_space" up-to-date. Offset tables may be updated in
395 // this phase as if the final copy had occurred; if so, "cp->threshold"
396 // indicates when the next such action should be taken.
397 virtual void prepare_for_compaction(CompactPoint* cp);
398 // MarkSweep support phase3
399 virtual void adjust_pointers();
400 // MarkSweep support phase4
401 virtual void compact();
402
403 // The maximum percentage of objects that can be dead in the compacted
404 // live part of a compacted space ("deadwood" support.)
405 virtual size_t allowed_dead_ratio() const { return 0; };
406
407 // Some contiguous spaces may maintain some data structures that should
408 // be updated whenever an allocation crosses a boundary. This function
409 // returns the first such boundary.
410 // (The default implementation returns the end of the space, so the
411 // boundary is never crossed.)
412 virtual HeapWord* initialize_threshold() { return end(); }
413
414 // "q" is an object of the given "size" that should be forwarded;
415 // "cp" names the generation ("gen") and containing "this" (which must
416 // also equal "cp->space"). "compact_top" is where in "this" the
417 // next object should be forwarded to. If there is room in "this" for
418 // the object, insert an appropriate forwarding pointer in "q".
419 // If not, go to the next compaction space (there must
420 // be one, since compaction must succeed -- we go to the first space of
421 // the previous generation if necessary, updating "cp"), reset compact_top
422 // and then forward. In either case, returns the new value of "compact_top".
423 // If the forwarding crosses "cp->threshold", invokes the "cross_threshold"
424 // function of the then-current compaction space, and updates "cp->threshold
425 // accordingly".
426 virtual HeapWord* forward(oop q, size_t size, CompactPoint* cp,
427 HeapWord* compact_top);
428
429 // Return a size with adjustments as required of the space.
430 virtual size_t adjust_object_size_v(size_t size) const { return size; }
431
432 protected:
433 // Used during compaction.
434 HeapWord* _first_dead;
435 HeapWord* _end_of_live;
436
437 // Minimum size of a free block.
438 virtual size_t minimum_free_block_size() const { return 0; }
439
440 // This the function is invoked when an allocation of an object covering
441 // "start" to "end occurs crosses the threshold; returns the next
442 // threshold. (The default implementation does nothing.)
443 virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* the_end) {
444 return end();
445 }
446
447 // Requires "allowed_deadspace_words > 0", that "q" is the start of a
448 // free block of the given "word_len", and that "q", were it an object,
449 // would not move if forwarded. If the size allows, fill the free
450 // block with an object, to prevent excessive compaction. Returns "true"
451 // iff the free region was made deadspace, and modifies
452 // "allowed_deadspace_words" to reflect the number of available deadspace
453 // words remaining after this operation.
454 bool insert_deadspace(size_t& allowed_deadspace_words, HeapWord* q,
455 size_t word_len);
456 };
457
458 class GenSpaceMangler;
459
460 // A space in which the free area is contiguous. It therefore supports
461 // faster allocation, and compaction.
462 class ContiguousSpace: public CompactibleSpace {
463 friend class OneContigSpaceCardGeneration;
464 friend class VMStructs;
465 protected:
466 HeapWord* _top;
467 HeapWord* _concurrent_iteration_safe_limit;
468 // A helper for mangling the unused area of the space in debug builds.
469 GenSpaceMangler* _mangler;
470
471 GenSpaceMangler* mangler() { return _mangler; }
472
473 // Allocation helpers (return NULL if full).
474 inline HeapWord* allocate_impl(size_t word_size, HeapWord* end_value);
475 inline HeapWord* par_allocate_impl(size_t word_size, HeapWord* end_value);
476
477 public:
478 ContiguousSpace();
479 ~ContiguousSpace();
480
481 virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
482 virtual void clear(bool mangle_space);
483
484 // Accessors
485 HeapWord* top() const { return _top; }
486 void set_top(HeapWord* value) { _top = value; }
487
488 void set_saved_mark() { _saved_mark_word = top(); }
489 void reset_saved_mark() { _saved_mark_word = bottom(); }
490
491 WaterMark bottom_mark() { return WaterMark(this, bottom()); }
492 WaterMark top_mark() { return WaterMark(this, top()); }
493 WaterMark saved_mark() { return WaterMark(this, saved_mark_word()); }
494 bool saved_mark_at_top() const { return saved_mark_word() == top(); }
495
496 // In debug mode mangle (write it with a particular bit
497 // pattern) the unused part of a space.
498
499 // Used to save the an address in a space for later use during mangling.
500 void set_top_for_allocations(HeapWord* v) PRODUCT_RETURN;
501 // Used to save the space's current top for later use during mangling.
502 void set_top_for_allocations() PRODUCT_RETURN;
503
504 // Mangle regions in the space from the current top up to the
505 // previously mangled part of the space.
506 void mangle_unused_area() PRODUCT_RETURN;
507 // Mangle [top, end)
508 void mangle_unused_area_complete() PRODUCT_RETURN;
509 // Mangle the given MemRegion.
510 void mangle_region(MemRegion mr) PRODUCT_RETURN;
511
512 // Do some sparse checking on the area that should have been mangled.
513 void check_mangled_unused_area(HeapWord* limit) PRODUCT_RETURN;
514 // Check the complete area that should have been mangled.
515 // This code may be NULL depending on the macro DEBUG_MANGLING.
516 void check_mangled_unused_area_complete() PRODUCT_RETURN;
517
518 // Size computations: sizes in bytes.
519 size_t capacity() const { return byte_size(bottom(), end()); }
520 size_t used() const { return byte_size(bottom(), top()); }
521 size_t free() const { return byte_size(top(), end()); }
522
523 virtual bool is_free_block(const HeapWord* p) const;
524
525 // In a contiguous space we have a more obvious bound on what parts
526 // contain objects.
527 MemRegion used_region() const { return MemRegion(bottom(), top()); }
528
529 // Allocation (return NULL if full)
530 virtual HeapWord* allocate(size_t word_size);
531 virtual HeapWord* par_allocate(size_t word_size);
532
533 // Iteration
534 void oop_iterate(ExtendedOopClosure* cl);
535 void object_iterate(ObjectClosure* blk);
536 // For contiguous spaces this method will iterate safely over objects
537 // in the space (i.e., between bottom and top) when at a safepoint.
538 void safe_object_iterate(ObjectClosure* blk);
539
540 // Iterate over as many initialized objects in the space as possible,
541 // calling "cl.do_object_careful" on each. Return NULL if all objects
542 // in the space (at the start of the iteration) were iterated over.
543 // Return an address indicating the extent of the iteration in the
544 // event that the iteration had to return because of finding an
545 // uninitialized object in the space, or if the closure "cl"
546 // signaled early termination.
547 HeapWord* object_iterate_careful(ObjectClosureCareful* cl);
548 HeapWord* concurrent_iteration_safe_limit() {
549 assert(_concurrent_iteration_safe_limit <= top(),
550 "_concurrent_iteration_safe_limit update missed");
551 return _concurrent_iteration_safe_limit;
552 }
553 // changes the safe limit, all objects from bottom() to the new
554 // limit should be properly initialized
555 void set_concurrent_iteration_safe_limit(HeapWord* new_limit) {
556 assert(new_limit <= top(), "uninitialized objects in the safe range");
557 _concurrent_iteration_safe_limit = new_limit;
558 }
559
560
561 #if INCLUDE_ALL_GCS
562 // In support of parallel oop_iterate.
563 #define ContigSpace_PAR_OOP_ITERATE_DECL(OopClosureType, nv_suffix) \
564 void par_oop_iterate(MemRegion mr, OopClosureType* blk);
565
566 ALL_PAR_OOP_ITERATE_CLOSURES(ContigSpace_PAR_OOP_ITERATE_DECL)
567 #undef ContigSpace_PAR_OOP_ITERATE_DECL
568 #endif // INCLUDE_ALL_GCS
569
570 // Compaction support
571 virtual void reset_after_compaction() {
572 assert(compaction_top() >= bottom() && compaction_top() <= end(), "should point inside space");
573 set_top(compaction_top());
574 // set new iteration safe limit
575 set_concurrent_iteration_safe_limit(compaction_top());
576 }
577
578 // Override.
579 DirtyCardToOopClosure* new_dcto_cl(ExtendedOopClosure* cl,
580 CardTableModRefBS::PrecisionStyle precision,
581 HeapWord* boundary = NULL);
582
583 // Apply "blk->do_oop" to the addresses of all reference fields in objects
584 // starting with the _saved_mark_word, which was noted during a generation's
585 // save_marks and is required to denote the head of an object.
586 // Fields in objects allocated by applications of the closure
587 // *are* included in the iteration.
588 // Updates _saved_mark_word to point to just after the last object
589 // iterated over.
590 #define ContigSpace_OOP_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
591 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk);
592
593 ALL_SINCE_SAVE_MARKS_CLOSURES(ContigSpace_OOP_SINCE_SAVE_MARKS_DECL)
594 #undef ContigSpace_OOP_SINCE_SAVE_MARKS_DECL
595
596 // Same as object_iterate, but starting from "mark", which is required
597 // to denote the start of an object. Objects allocated by
598 // applications of the closure *are* included in the iteration.
599 virtual void object_iterate_from(WaterMark mark, ObjectClosure* blk);
600
601 // Very inefficient implementation.
602 virtual HeapWord* block_start_const(const void* p) const;
603 size_t block_size(const HeapWord* p) const;
604 // If a block is in the allocated area, it is an object.
605 bool block_is_obj(const HeapWord* p) const { return p < top(); }
606
607 // Addresses for inlined allocation
608 HeapWord** top_addr() { return &_top; }
609 HeapWord** end_addr() { return &_end; }
610
611 // Overrides for more efficient compaction support.
612 void prepare_for_compaction(CompactPoint* cp);
613
614 // PrintHeapAtGC support.
615 virtual void print_on(outputStream* st) const;
616
617 // Checked dynamic downcasts.
618 virtual ContiguousSpace* toContiguousSpace() {
619 return this;
620 }
621
622 // Debugging
623 virtual void verify() const;
624
625 // Used to increase collection frequency. "factor" of 0 means entire
626 // space.
627 void allocate_temporary_filler(int factor);
628
629 };
630
631
632 // A dirty card to oop closure that does filtering.
633 // It knows how to filter out objects that are outside of the _boundary.
634 class Filtering_DCTOC : public DirtyCardToOopClosure {
635 protected:
636 // Override.
637 void walk_mem_region(MemRegion mr,
638 HeapWord* bottom, HeapWord* top);
639
640 // Walk the given memory region, from bottom to top, applying
641 // the given oop closure to (possibly) all objects found. The
642 // given oop closure may or may not be the same as the oop
643 // closure with which this closure was created, as it may
644 // be a filtering closure which makes use of the _boundary.
645 // We offer two signatures, so the FilteringClosure static type is
646 // apparent.
647 virtual void walk_mem_region_with_cl(MemRegion mr,
648 HeapWord* bottom, HeapWord* top,
649 ExtendedOopClosure* cl) = 0;
650 virtual void walk_mem_region_with_cl(MemRegion mr,
651 HeapWord* bottom, HeapWord* top,
652 FilteringClosure* cl) = 0;
653
654 public:
655 Filtering_DCTOC(Space* sp, ExtendedOopClosure* cl,
656 CardTableModRefBS::PrecisionStyle precision,
657 HeapWord* boundary) :
658 DirtyCardToOopClosure(sp, cl, precision, boundary) {}
659 };
660
661 // A dirty card to oop closure for contiguous spaces
662 // (ContiguousSpace and sub-classes).
663 // It is a FilteringClosure, as defined above, and it knows:
664 //
665 // 1. That the actual top of any area in a memory region
666 // contained by the space is bounded by the end of the contiguous
667 // region of the space.
668 // 2. That the space is really made up of objects and not just
669 // blocks.
670
671 class ContiguousSpaceDCTOC : public Filtering_DCTOC {
672 protected:
673 // Overrides.
674 HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj);
675
676 virtual void walk_mem_region_with_cl(MemRegion mr,
677 HeapWord* bottom, HeapWord* top,
678 ExtendedOopClosure* cl);
679 virtual void walk_mem_region_with_cl(MemRegion mr,
680 HeapWord* bottom, HeapWord* top,
681 FilteringClosure* cl);
682
683 public:
684 ContiguousSpaceDCTOC(ContiguousSpace* sp, ExtendedOopClosure* cl,
685 CardTableModRefBS::PrecisionStyle precision,
686 HeapWord* boundary) :
687 Filtering_DCTOC(sp, cl, precision, boundary)
688 {}
689 };
690
691
692 // Class EdenSpace describes eden-space in new generation.
693
694 class DefNewGeneration;
695
696 class EdenSpace : public ContiguousSpace {
697 friend class VMStructs;
698 private:
699 DefNewGeneration* _gen;
700
701 // _soft_end is used as a soft limit on allocation. As soft limits are
702 // reached, the slow-path allocation code can invoke other actions and then
703 // adjust _soft_end up to a new soft limit or to end().
704 HeapWord* _soft_end;
705
706 public:
707 EdenSpace(DefNewGeneration* gen) :
708 _gen(gen), _soft_end(NULL) {}
709
710 // Get/set just the 'soft' limit.
711 HeapWord* soft_end() { return _soft_end; }
712 HeapWord** soft_end_addr() { return &_soft_end; }
713 void set_soft_end(HeapWord* value) { _soft_end = value; }
714
715 // Override.
716 void clear(bool mangle_space);
717
718 // Set both the 'hard' and 'soft' limits (_end and _soft_end).
719 void set_end(HeapWord* value) {
720 set_soft_end(value);
721 ContiguousSpace::set_end(value);
722 }
723
724 // Allocation (return NULL if full)
725 HeapWord* allocate(size_t word_size);
726 HeapWord* par_allocate(size_t word_size);
727 };
728
729 // Class ConcEdenSpace extends EdenSpace for the sake of safe
730 // allocation while soft-end is being modified concurrently
731
732 class ConcEdenSpace : public EdenSpace {
733 public:
734 ConcEdenSpace(DefNewGeneration* gen) : EdenSpace(gen) { }
735
736 // Allocation (return NULL if full)
737 HeapWord* par_allocate(size_t word_size);
738 };
739
740
741 // A ContigSpace that Supports an efficient "block_start" operation via
742 // a BlockOffsetArray (whose BlockOffsetSharedArray may be shared with
743 // other spaces.) This is the abstract base class for old generation
744 // (tenured) spaces.
745
746 class OffsetTableContigSpace: public ContiguousSpace {
747 friend class VMStructs;
748 protected:
749 BlockOffsetArrayContigSpace _offsets;
750 Mutex _par_alloc_lock;
751
752 public:
753 // Constructor
754 OffsetTableContigSpace(BlockOffsetSharedArray* sharedOffsetArray,
755 MemRegion mr);
756
757 void set_bottom(HeapWord* value);
758 void set_end(HeapWord* value);
759
760 void clear(bool mangle_space);
761
762 inline HeapWord* block_start_const(const void* p) const;
763
764 // Add offset table update.
765 virtual inline HeapWord* allocate(size_t word_size);
766 inline HeapWord* par_allocate(size_t word_size);
767
768 // MarkSweep support phase3
769 virtual HeapWord* initialize_threshold();
770 virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* end);
771
772 virtual void print_on(outputStream* st) const;
773
774 // Debugging
775 void verify() const;
776 };
777
778
779 // Class TenuredSpace is used by TenuredGeneration
780
781 class TenuredSpace: public OffsetTableContigSpace {
782 friend class VMStructs;
783 protected:
784 // Mark sweep support
785 size_t allowed_dead_ratio() const;
786 public:
787 // Constructor
788 TenuredSpace(BlockOffsetSharedArray* sharedOffsetArray,
789 MemRegion mr) :
790 OffsetTableContigSpace(sharedOffsetArray, mr) {}
791 };
792 #endif // SHARE_VM_MEMORY_SPACE_HPP