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_GENERATION_HPP
26 #define SHARE_VM_MEMORY_GENERATION_HPP
27
28 #include "gc_implementation/shared/collectorCounters.hpp"
29 #include "memory/allocation.hpp"
30 #include "memory/memRegion.hpp"
31 #include "memory/referenceProcessor.hpp"
32 #include "memory/universe.hpp"
33 #include "memory/watermark.hpp"
34 #include "runtime/mutex.hpp"
35 #include "runtime/perfData.hpp"
36 #include "runtime/virtualspace.hpp"
37
38 // A Generation models a heap area for similarly-aged objects.
39 // It will contain one ore more spaces holding the actual objects.
40 //
41 // The Generation class hierarchy:
42 //
43 // Generation - abstract base class
44 // - DefNewGeneration - allocation area (copy collected)
45 // - ParNewGeneration - a DefNewGeneration that is collected by
46 // several threads
47 // - CardGeneration - abstract class adding offset array behavior
48 // - OneContigSpaceCardGeneration - abstract class holding a single
49 // contiguous space with card marking
50 // - TenuredGeneration - tenured (old object) space (markSweepCompact)
51 // - ConcurrentMarkSweepGeneration - Mostly Concurrent Mark Sweep Generation
52 // (Detlefs-Printezis refinement of
53 // Boehm-Demers-Schenker)
54 //
55 // The system configurations currently allowed are:
56 //
57 // DefNewGeneration + TenuredGeneration
58 // DefNewGeneration + ConcurrentMarkSweepGeneration
59 //
60 // ParNewGeneration + TenuredGeneration
61 // ParNewGeneration + ConcurrentMarkSweepGeneration
62 //
63
64 class DefNewGeneration;
65 class GenerationSpec;
66 class CompactibleSpace;
67 class ContiguousSpace;
68 class CompactPoint;
69 class OopsInGenClosure;
70 class OopClosure;
71 class ScanClosure;
72 class FastScanClosure;
73 class GenCollectedHeap;
74 class GenRemSet;
75 class GCStats;
76
77 // A "ScratchBlock" represents a block of memory in one generation usable by
78 // another. It represents "num_words" free words, starting at and including
79 // the address of "this".
80 struct ScratchBlock {
81 ScratchBlock* next;
82 size_t num_words;
83 HeapWord scratch_space[1]; // Actually, of size "num_words-2" (assuming
84 // first two fields are word-sized.)
85 };
86
87
88 class Generation: public CHeapObj<mtGC> {
89 friend class VMStructs;
90 private:
91 jlong _time_of_last_gc; // time when last gc on this generation happened (ms)
92 MemRegion _prev_used_region; // for collectors that want to "remember" a value for
93 // used region at some specific point during collection.
94
95 protected:
96 // Minimum and maximum addresses for memory reserved (not necessarily
97 // committed) for generation.
98 // Used by card marking code. Must not overlap with address ranges of
99 // other generations.
100 MemRegion _reserved;
101
102 // Memory area reserved for generation
103 VirtualSpace _virtual_space;
104
105 // ("Weak") Reference processing support
106 ReferenceProcessor* _ref_processor;
107
108 // Performance Counters
109 CollectorCounters* _gc_counters;
110
111 // Statistics for garbage collection
112 GCStats* _gc_stats;
113
114 // Initialize the generation.
115 Generation(ReservedSpace rs, size_t initial_byte_size);
116
117 // Apply "cl->do_oop" to (the address of) (exactly) all the ref fields in
118 // "sp" that point into younger generations.
119 // The iteration is only over objects allocated at the start of the
120 // iterations; objects allocated as a result of applying the closure are
121 // not included.
122 void younger_refs_in_space_iterate(Space* sp, OopsInGenClosure* cl);
123
124 public:
125 // The set of possible generation kinds.
126 enum Name {
127 DefNew,
128 ParNew,
129 MarkSweepCompact,
130 ConcurrentMarkSweep,
131 Other
132 };
133
134 enum Type {
135 Young,
136 Old
137 };
138
139 enum SomePublicConstants {
140 // Generations are GenGrain-aligned and have size that are multiples of
141 // GenGrain.
142 // Note: on ARM we add 1 bit for card_table_base to be properly aligned
143 // (we expect its low byte to be zero - see implementation of post_barrier)
144 LogOfGenGrain = 16 ARM_ONLY(+1),
145 GenGrain = 1 << LogOfGenGrain
146 };
147
148 // allocate and initialize ("weak") refs processing support
149 virtual void ref_processor_init();
150 void set_ref_processor(ReferenceProcessor* rp) {
151 assert(_ref_processor == NULL, "clobbering existing _ref_processor");
152 _ref_processor = rp;
153 }
154
155 virtual Generation::Name kind() { return Generation::Other; }
156 GenerationSpec* spec();
157
158 // This properly belongs in the collector, but for now this
159 // will do.
160 virtual bool refs_discovery_is_atomic() const { return true; }
161 virtual bool refs_discovery_is_mt() const { return false; }
162
163 // Space enquiries (results in bytes)
164 virtual size_t capacity() const = 0; // The maximum number of object bytes the
165 // generation can currently hold.
166 virtual size_t used() const = 0; // The number of used bytes in the gen.
167 virtual size_t free() const = 0; // The number of free bytes in the gen.
168
169 // Support for java.lang.Runtime.maxMemory(); see CollectedHeap.
170 // Returns the total number of bytes available in a generation
171 // for the allocation of objects.
172 virtual size_t max_capacity() const;
173
174 // If this is a young generation, the maximum number of bytes that can be
175 // allocated in this generation before a GC is triggered.
176 virtual size_t capacity_before_gc() const { return 0; }
177
178 // The largest number of contiguous free bytes in the generation,
179 // including expansion (Assumes called at a safepoint.)
180 virtual size_t contiguous_available() const = 0;
181 // The largest number of contiguous free bytes in this or any higher generation.
182 virtual size_t max_contiguous_available() const;
183
184 // Returns true if promotions of the specified amount are
185 // likely to succeed without a promotion failure.
186 // Promotion of the full amount is not guaranteed but
187 // might be attempted in the worst case.
188 virtual bool promotion_attempt_is_safe(size_t max_promotion_in_bytes) const;
189
190 // For a non-young generation, this interface can be used to inform a
191 // generation that a promotion attempt into that generation failed.
192 // Typically used to enable diagnostic output for post-mortem analysis,
193 // but other uses of the interface are not ruled out.
194 virtual void promotion_failure_occurred() { /* does nothing */ }
195
196 // Return an estimate of the maximum allocation that could be performed
197 // in the generation without triggering any collection or expansion
198 // activity. It is "unsafe" because no locks are taken; the result
199 // should be treated as an approximation, not a guarantee, for use in
200 // heuristic resizing decisions.
201 virtual size_t unsafe_max_alloc_nogc() const = 0;
202
203 // Returns true if this generation cannot be expanded further
204 // without a GC. Override as appropriate.
205 virtual bool is_maximal_no_gc() const {
206 return _virtual_space.uncommitted_size() == 0;
207 }
208
209 MemRegion reserved() const { return _reserved; }
210
211 // Returns a region guaranteed to contain all the objects in the
212 // generation.
213 virtual MemRegion used_region() const { return _reserved; }
214
215 MemRegion prev_used_region() const { return _prev_used_region; }
216 virtual void save_used_region() { _prev_used_region = used_region(); }
217
218 // Returns "TRUE" iff "p" points into the committed areas in the generation.
219 // For some kinds of generations, this may be an expensive operation.
220 // To avoid performance problems stemming from its inadvertent use in
221 // product jvm's, we restrict its use to assertion checking or
222 // verification only.
223 virtual bool is_in(const void* p) const;
224
225 /* Returns "TRUE" iff "p" points into the reserved area of the generation. */
226 bool is_in_reserved(const void* p) const {
227 return _reserved.contains(p);
228 }
229
230 // Check that the generation kind is DefNewGeneration or a sub
231 // class of DefNewGeneration and return a DefNewGeneration*
232 DefNewGeneration* as_DefNewGeneration();
233
234 // If some space in the generation contains the given "addr", return a
235 // pointer to that space, else return "NULL".
236 virtual Space* space_containing(const void* addr) const;
237
238 // Iteration - do not use for time critical operations
239 virtual void space_iterate(SpaceClosure* blk, bool usedOnly = false) = 0;
240
241 // Returns the first space, if any, in the generation that can participate
242 // in compaction, or else "NULL".
243 virtual CompactibleSpace* first_compaction_space() const = 0;
244
245 // Returns "true" iff this generation should be used to allocate an
246 // object of the given size. Young generations might
247 // wish to exclude very large objects, for example, since, if allocated
248 // often, they would greatly increase the frequency of young-gen
249 // collection.
250 virtual bool should_allocate(size_t word_size, bool is_tlab) {
251 bool result = false;
252 size_t overflow_limit = (size_t)1 << (BitsPerSize_t - LogHeapWordSize);
253 if (!is_tlab || supports_tlab_allocation()) {
254 result = (word_size > 0) && (word_size < overflow_limit);
255 }
256 return result;
257 }
258
259 // Allocate and returns a block of the requested size, or returns "NULL".
260 // Assumes the caller has done any necessary locking.
261 virtual HeapWord* allocate(size_t word_size, bool is_tlab) = 0;
262
263 // Like "allocate", but performs any necessary locking internally.
264 virtual HeapWord* par_allocate(size_t word_size, bool is_tlab) = 0;
265
266 // A 'younger' gen has reached an allocation limit, and uses this to notify
267 // the next older gen. The return value is a new limit, or NULL if none. The
268 // caller must do the necessary locking.
269 virtual HeapWord* allocation_limit_reached(Space* space, HeapWord* top,
270 size_t word_size) {
271 return NULL;
272 }
273
274 // Some generation may offer a region for shared, contiguous allocation,
275 // via inlined code (by exporting the address of the top and end fields
276 // defining the extent of the contiguous allocation region.)
277
278 // This function returns "true" iff the heap supports this kind of
279 // allocation. (More precisely, this means the style of allocation that
280 // increments *top_addr()" with a CAS.) (Default is "no".)
281 // A generation that supports this allocation style must use lock-free
282 // allocation for *all* allocation, since there are times when lock free
283 // allocation will be concurrent with plain "allocate" calls.
284 virtual bool supports_inline_contig_alloc() const { return false; }
285
286 // These functions return the addresses of the fields that define the
287 // boundaries of the contiguous allocation area. (These fields should be
288 // physically near to one another.)
289 virtual HeapWord** top_addr() const { return NULL; }
290 virtual HeapWord** end_addr() const { return NULL; }
291
292 // Thread-local allocation buffers
293 virtual bool supports_tlab_allocation() const { return false; }
294 virtual size_t tlab_capacity() const {
295 guarantee(false, "Generation doesn't support thread local allocation buffers");
296 return 0;
297 }
298 virtual size_t tlab_used() const {
299 guarantee(false, "Generation doesn't support thread local allocation buffers");
300 return 0;
301 }
302 virtual size_t unsafe_max_tlab_alloc() const {
303 guarantee(false, "Generation doesn't support thread local allocation buffers");
304 return 0;
305 }
306
307 // "obj" is the address of an object in a younger generation. Allocate space
308 // for "obj" in the current (or some higher) generation, and copy "obj" into
309 // the newly allocated space, if possible, returning the result (or NULL if
310 // the allocation failed).
311 //
312 // The "obj_size" argument is just obj->size(), passed along so the caller can
313 // avoid repeating the virtual call to retrieve it.
314 virtual oop promote(oop obj, size_t obj_size);
315
316 // Thread "thread_num" (0 <= i < ParalleGCThreads) wants to promote
317 // object "obj", whose original mark word was "m", and whose size is
318 // "word_sz". If possible, allocate space for "obj", copy obj into it
319 // (taking care to copy "m" into the mark word when done, since the mark
320 // word of "obj" may have been overwritten with a forwarding pointer, and
321 // also taking care to copy the klass pointer *last*. Returns the new
322 // object if successful, or else NULL.
323 virtual oop par_promote(int thread_num,
324 oop obj, markOop m, size_t word_sz);
325
326 // Undo, if possible, the most recent par_promote_alloc allocation by
327 // "thread_num" ("obj", of "word_sz").
328 virtual void par_promote_alloc_undo(int thread_num,
329 HeapWord* obj, size_t word_sz);
330
331 // Informs the current generation that all par_promote_alloc's in the
332 // collection have been completed; any supporting data structures can be
333 // reset. Default is to do nothing.
334 virtual void par_promote_alloc_done(int thread_num) {}
335
336 // Informs the current generation that all oop_since_save_marks_iterates
337 // performed by "thread_num" in the current collection, if any, have been
338 // completed; any supporting data structures can be reset. Default is to
339 // do nothing.
340 virtual void par_oop_since_save_marks_iterate_done(int thread_num) {}
341
342 // This generation will collect all younger generations
343 // during a full collection.
344 virtual bool full_collects_younger_generations() const { return false; }
345
346 // This generation does in-place marking, meaning that mark words
347 // are mutated during the marking phase and presumably reinitialized
348 // to a canonical value after the GC. This is currently used by the
349 // biased locking implementation to determine whether additional
350 // work is required during the GC prologue and epilogue.
351 virtual bool performs_in_place_marking() const { return true; }
352
353 // Returns "true" iff collect() should subsequently be called on this
354 // this generation. See comment below.
355 // This is a generic implementation which can be overridden.
356 //
357 // Note: in the current (1.4) implementation, when genCollectedHeap's
358 // incremental_collection_will_fail flag is set, all allocations are
359 // slow path (the only fast-path place to allocate is DefNew, which
360 // will be full if the flag is set).
361 // Thus, older generations which collect younger generations should
362 // test this flag and collect if it is set.
363 virtual bool should_collect(bool full,
364 size_t word_size,
365 bool is_tlab) {
366 return (full || should_allocate(word_size, is_tlab));
367 }
368
369 // Returns true if the collection is likely to be safely
370 // completed. Even if this method returns true, a collection
371 // may not be guaranteed to succeed, and the system should be
372 // able to safely unwind and recover from that failure, albeit
373 // at some additional cost.
374 virtual bool collection_attempt_is_safe() {
375 guarantee(false, "Are you sure you want to call this method?");
376 return true;
377 }
378
379 // Perform a garbage collection.
380 // If full is true attempt a full garbage collection of this generation.
381 // Otherwise, attempting to (at least) free enough space to support an
382 // allocation of the given "word_size".
383 virtual void collect(bool full,
384 bool clear_all_soft_refs,
385 size_t word_size,
386 bool is_tlab) = 0;
387
388 // Perform a heap collection, attempting to create (at least) enough
389 // space to support an allocation of the given "word_size". If
390 // successful, perform the allocation and return the resulting
391 // "oop" (initializing the allocated block). If the allocation is
392 // still unsuccessful, return "NULL".
393 virtual HeapWord* expand_and_allocate(size_t word_size,
394 bool is_tlab,
395 bool parallel = false) = 0;
396
397 // Some generations may require some cleanup or preparation actions before
398 // allowing a collection. The default is to do nothing.
399 virtual void gc_prologue(bool full) {};
400
401 // Some generations may require some cleanup actions after a collection.
402 // The default is to do nothing.
403 virtual void gc_epilogue(bool full) {};
404
405 // Save the high water marks for the used space in a generation.
406 virtual void record_spaces_top() {};
407
408 // Some generations may need to be "fixed-up" after some allocation
409 // activity to make them parsable again. The default is to do nothing.
410 virtual void ensure_parsability() {};
411
412 // Time (in ms) when we were last collected or now if a collection is
413 // in progress.
414 virtual jlong time_of_last_gc(jlong now) {
415 // Both _time_of_last_gc and now are set using a time source
416 // that guarantees monotonically non-decreasing values provided
417 // the underlying platform provides such a source. So we still
418 // have to guard against non-monotonicity.
419 NOT_PRODUCT(
420 if (now < _time_of_last_gc) {
421 warning("time warp: "INT64_FORMAT" to "INT64_FORMAT, (int64_t)_time_of_last_gc, (int64_t)now);
422 }
423 )
424 return _time_of_last_gc;
425 }
426
427 virtual void update_time_of_last_gc(jlong now) {
428 _time_of_last_gc = now;
429 }
430
431 // Generations may keep statistics about collection. This
432 // method updates those statistics. current_level is
433 // the level of the collection that has most recently
434 // occurred. This allows the generation to decide what
435 // statistics are valid to collect. For example, the
436 // generation can decide to gather the amount of promoted data
437 // if the collection of the younger generations has completed.
438 GCStats* gc_stats() const { return _gc_stats; }
439 virtual void update_gc_stats(Generation* current_generation, bool full) {}
440
441 // Mark sweep support phase2
442 virtual void prepare_for_compaction(CompactPoint* cp);
443 // Mark sweep support phase3
444 virtual void adjust_pointers();
445 // Mark sweep support phase4
446 virtual void compact();
447 virtual void post_compact() {ShouldNotReachHere();}
448
449 // Support for CMS's rescan. In this general form we return a pointer
450 // to an abstract object that can be used, based on specific previously
451 // decided protocols, to exchange information between generations,
452 // information that may be useful for speeding up certain types of
453 // garbage collectors. A NULL value indicates to the client that
454 // no data recording is expected by the provider. The data-recorder is
455 // expected to be GC worker thread-local, with the worker index
456 // indicated by "thr_num".
457 virtual void* get_data_recorder(int thr_num) { return NULL; }
458 virtual void sample_eden_chunk() {}
459
460 // Some generations may require some cleanup actions before allowing
461 // a verification.
462 virtual void prepare_for_verify() {};
463
464 // Accessing "marks".
465
466 // This function gives a generation a chance to note a point between
467 // collections. For example, a contiguous generation might note the
468 // beginning allocation point post-collection, which might allow some later
469 // operations to be optimized.
470 virtual void save_marks() {}
471
472 // This function allows generations to initialize any "saved marks". That
473 // is, should only be called when the generation is empty.
474 virtual void reset_saved_marks() {}
475
476 // This function is "true" iff any no allocations have occurred in the
477 // generation since the last call to "save_marks".
478 virtual bool no_allocs_since_save_marks() = 0;
479
480 // Apply "cl->apply" to (the addresses of) all reference fields in objects
481 // allocated in the current generation since the last call to "save_marks".
482 // If more objects are allocated in this generation as a result of applying
483 // the closure, iterates over reference fields in those objects as well.
484 // Calls "save_marks" at the end of the iteration.
485 // General signature...
486 virtual void oop_since_save_marks_iterate_v(OopsInGenClosure* cl) = 0;
487 // ...and specializations for de-virtualization. (The general
488 // implementation of the _nv versions call the virtual version.
489 // Note that the _nv suffix is not really semantically necessary,
490 // but it avoids some not-so-useful warnings on Solaris.)
491 #define Generation_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
492 virtual void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \
493 oop_since_save_marks_iterate_v((OopsInGenClosure*)cl); \
494 }
495 SPECIALIZED_SINCE_SAVE_MARKS_CLOSURES(Generation_SINCE_SAVE_MARKS_DECL)
496
497 #undef Generation_SINCE_SAVE_MARKS_DECL
498
499 // The "requestor" generation is performing some garbage collection
500 // action for which it would be useful to have scratch space. If
501 // the target is not the requestor, no gc actions will be required
502 // of the target. The requestor promises to allocate no more than
503 // "max_alloc_words" in the target generation (via promotion say,
504 // if the requestor is a young generation and the target is older).
505 // If the target generation can provide any scratch space, it adds
506 // it to "list", leaving "list" pointing to the head of the
507 // augmented list. The default is to offer no space.
508 virtual void contribute_scratch(ScratchBlock*& list, Generation* requestor,
509 size_t max_alloc_words) {}
510
511 // Give each generation an opportunity to do clean up for any
512 // contributed scratch.
513 virtual void reset_scratch() {};
514
515 // When an older generation has been collected, and perhaps resized,
516 // this method will be invoked on all younger generations (from older to
517 // younger), allowing them to resize themselves as appropriate.
518 virtual void compute_new_size() = 0;
519
520 // Printing
521 virtual const char* name() const = 0;
522 virtual const char* short_name() const = 0;
523
524 // Attributes
525
526 // True iff the given generation may only be the youngest generation.
527 virtual bool must_be_youngest() const = 0;
528 // True iff the given generation may only be the oldest generation.
529 virtual bool must_be_oldest() const = 0;
530
531 // Reference Processing accessor
532 ReferenceProcessor* const ref_processor() { return _ref_processor; }
533
534 // Iteration.
535
536 // Iterate over all the ref-containing fields of all objects in the
537 // generation, calling "cl.do_oop" on each.
538 virtual void oop_iterate(ExtendedOopClosure* cl);
539
540 // Iterate over all objects in the generation, calling "cl.do_object" on
541 // each.
542 virtual void object_iterate(ObjectClosure* cl);
543
544 // Iterate over all safe objects in the generation, calling "cl.do_object" on
545 // each. An object is safe if its references point to other objects in
546 // the heap. This defaults to object_iterate() unless overridden.
547 virtual void safe_object_iterate(ObjectClosure* cl);
548
549 // Apply "cl->do_oop" to (the address of) all and only all the ref fields
550 // in the current generation that contain pointers to objects in younger
551 // generations. Objects allocated since the last "save_marks" call are
552 // excluded.
553 virtual void younger_refs_iterate(OopsInGenClosure* cl) = 0;
554
555 // Inform a generation that it longer contains references to objects
556 // in any younger generation. [e.g. Because younger gens are empty,
557 // clear the card table.]
558 virtual void clear_remembered_set() { }
559
560 // Inform a generation that some of its objects have moved. [e.g. The
561 // generation's spaces were compacted, invalidating the card table.]
562 virtual void invalidate_remembered_set() { }
563
564 // Block abstraction.
565
566 // Returns the address of the start of the "block" that contains the
567 // address "addr". We say "blocks" instead of "object" since some heaps
568 // may not pack objects densely; a chunk may either be an object or a
569 // non-object.
570 virtual HeapWord* block_start(const void* addr) const;
571
572 // Requires "addr" to be the start of a chunk, and returns its size.
573 // "addr + size" is required to be the start of a new chunk, or the end
574 // of the active area of the heap.
575 virtual size_t block_size(const HeapWord* addr) const ;
576
577 // Requires "addr" to be the start of a block, and returns "TRUE" iff
578 // the block is an object.
579 virtual bool block_is_obj(const HeapWord* addr) const;
580
581
582 // PrintGC, PrintGCDetails support
583 void print_heap_change(size_t prev_used) const;
584
585 // PrintHeapAtGC support
586 virtual void print() const;
587 virtual void print_on(outputStream* st) const;
588
589 virtual void verify() = 0;
590
591 struct StatRecord {
592 int invocations;
593 elapsedTimer accumulated_time;
594 StatRecord() :
595 invocations(0),
596 accumulated_time(elapsedTimer()) {}
597 };
598 private:
599 StatRecord _stat_record;
600 public:
601 StatRecord* stat_record() { return &_stat_record; }
602
603 virtual void print_summary_info();
604 virtual void print_summary_info_on(outputStream* st);
605
606 // Performance Counter support
607 virtual void update_counters() = 0;
608 virtual CollectorCounters* counters() { return _gc_counters; }
609 };
610
611 // Class CardGeneration is a generation that is covered by a card table,
612 // and uses a card-size block-offset array to implement block_start.
613
614 // class BlockOffsetArray;
615 // class BlockOffsetArrayContigSpace;
616 class BlockOffsetSharedArray;
617
618 class CardGeneration: public Generation {
619 friend class VMStructs;
620 protected:
621 // This is shared with other generations.
622 GenRemSet* _rs;
623 // This is local to this generation.
624 BlockOffsetSharedArray* _bts;
625
626 // current shrinking effect: this damps shrinking when the heap gets empty.
627 size_t _shrink_factor;
628
629 size_t _min_heap_delta_bytes; // Minimum amount to expand.
630
631 // Some statistics from before gc started.
632 // These are gathered in the gc_prologue (and should_collect)
633 // to control growing/shrinking policy in spite of promotions.
634 size_t _capacity_at_prologue;
635 size_t _used_at_prologue;
636
637 CardGeneration(ReservedSpace rs, size_t initial_byte_size, GenRemSet* remset);
638
639 public:
640
641 // Attempt to expand the generation by "bytes". Expand by at a
642 // minimum "expand_bytes". Return true if some amount (not
643 // necessarily the full "bytes") was done.
644 virtual bool expand(size_t bytes, size_t expand_bytes);
645
646 // Shrink generation with specified size (returns false if unable to shrink)
647 virtual void shrink(size_t bytes) = 0;
648
649 virtual void compute_new_size();
650
651 virtual void clear_remembered_set();
652
653 virtual void invalidate_remembered_set();
654
655 virtual void prepare_for_verify();
656
657 // Grow generation with specified size (returns false if unable to grow)
658 virtual bool grow_by(size_t bytes) = 0;
659 // Grow generation to reserved size.
660 virtual bool grow_to_reserved() = 0;
661 };
662
663 // OneContigSpaceCardGeneration models a heap of old objects contained in a single
664 // contiguous space.
665 //
666 // Garbage collection is performed using mark-compact.
667
668 class OneContigSpaceCardGeneration: public CardGeneration {
669 friend class VMStructs;
670 // Abstractly, this is a subtype that gets access to protected fields.
671 friend class VM_PopulateDumpSharedSpace;
672
673 protected:
674 ContiguousSpace* _the_space; // actual space holding objects
675 WaterMark _last_gc; // watermark between objects allocated before
676 // and after last GC.
677
678 // Grow generation with specified size (returns false if unable to grow)
679 virtual bool grow_by(size_t bytes);
680 // Grow generation to reserved size.
681 virtual bool grow_to_reserved();
682 // Shrink generation with specified size (returns false if unable to shrink)
683 void shrink_by(size_t bytes);
684
685 // Allocation failure
686 virtual bool expand(size_t bytes, size_t expand_bytes);
687 void shrink(size_t bytes);
688
689 // Accessing spaces
690 ContiguousSpace* the_space() const { return _the_space; }
691
692 public:
693 OneContigSpaceCardGeneration(ReservedSpace rs, size_t initial_byte_size,
694 GenRemSet* remset, ContiguousSpace* space) :
695 CardGeneration(rs, initial_byte_size, remset),
696 _the_space(space)
697 {}
698
699 inline bool is_in(const void* p) const;
700
701 // Space enquiries
702 size_t capacity() const;
703 size_t used() const;
704 size_t free() const;
705
706 MemRegion used_region() const;
707
708 size_t unsafe_max_alloc_nogc() const;
709 size_t contiguous_available() const;
710
711 // Iteration
712 void object_iterate(ObjectClosure* blk);
713 void space_iterate(SpaceClosure* blk, bool usedOnly = false);
714
715 void younger_refs_iterate(OopsInGenClosure* blk);
716
717 inline CompactibleSpace* first_compaction_space() const;
718
719 virtual inline HeapWord* allocate(size_t word_size, bool is_tlab);
720 virtual inline HeapWord* par_allocate(size_t word_size, bool is_tlab);
721
722 // Accessing marks
723 inline WaterMark top_mark();
724 inline WaterMark bottom_mark();
725
726 #define OneContig_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
727 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl);
728 OneContig_SINCE_SAVE_MARKS_DECL(OopsInGenClosure,_v)
729 SPECIALIZED_SINCE_SAVE_MARKS_CLOSURES(OneContig_SINCE_SAVE_MARKS_DECL)
730
731 void save_marks();
732 void reset_saved_marks();
733 bool no_allocs_since_save_marks();
734
735 inline size_t block_size(const HeapWord* addr) const;
736
737 inline bool block_is_obj(const HeapWord* addr) const;
738
739 virtual void collect(bool full,
740 bool clear_all_soft_refs,
741 size_t size,
742 bool is_tlab);
743 HeapWord* expand_and_allocate(size_t size,
744 bool is_tlab,
745 bool parallel = false);
746
747 virtual void prepare_for_verify();
748
749 virtual void gc_epilogue(bool full);
750
751 virtual void record_spaces_top();
752
753 virtual void verify();
754 virtual void print_on(outputStream* st) const;
755 };
756
757 #endif // SHARE_VM_MEMORY_GENERATION_HPP