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 // Level in the generation hierarchy.
106 int _level;
107
108 // ("Weak") Reference processing support
109 ReferenceProcessor* _ref_processor;
110
111 // Performance Counters
112 CollectorCounters* _gc_counters;
113
114 // Statistics for garbage collection
115 GCStats* _gc_stats;
116
117 // Returns the next generation in the configuration, or else NULL if this
118 // is the highest generation.
119 Generation* next_gen() const;
120
121 // Initialize the generation.
122 Generation(ReservedSpace rs, size_t initial_byte_size, int level);
123
124 // Apply "cl->do_oop" to (the address of) (exactly) all the ref fields in
125 // "sp" that point into younger generations.
126 // The iteration is only over objects allocated at the start of the
127 // iterations; objects allocated as a result of applying the closure are
128 // not included.
129 void younger_refs_in_space_iterate(Space* sp, OopsInGenClosure* cl);
130
131 public:
132 // The set of possible generation kinds.
133 enum Name {
134 DefNew,
135 ParNew,
136 MarkSweepCompact,
137 ConcurrentMarkSweep,
138 Other
139 };
140
141 enum SomePublicConstants {
142 // Generations are GenGrain-aligned and have size that are multiples of
143 // GenGrain.
144 // Note: on ARM we add 1 bit for card_table_base to be properly aligned
145 // (we expect its low byte to be zero - see implementation of post_barrier)
146 LogOfGenGrain = 16 ARM_ONLY(+1),
147 GenGrain = 1 << LogOfGenGrain
148 };
149
150 // allocate and initialize ("weak") refs processing support
151 virtual void ref_processor_init();
152 void set_ref_processor(ReferenceProcessor* rp) {
153 assert(_ref_processor == NULL, "clobbering existing _ref_processor");
154 _ref_processor = rp;
155 }
156
157 virtual Generation::Name kind() { return Generation::Other; }
158 GenerationSpec* spec();
159
160 // This properly belongs in the collector, but for now this
161 // will do.
162 virtual bool refs_discovery_is_atomic() const { return true; }
163 virtual bool refs_discovery_is_mt() const { return false; }
164
165 // Space enquiries (results in bytes)
166 virtual size_t capacity() const = 0; // The maximum number of object bytes the
167 // generation can currently hold.
168 virtual size_t used() const = 0; // The number of used bytes in the gen.
169 virtual size_t free() const = 0; // The number of free bytes in the gen.
170
171 // Support for java.lang.Runtime.maxMemory(); see CollectedHeap.
172 // Returns the total number of bytes available in a generation
173 // for the allocation of objects.
174 virtual size_t max_capacity() const;
175
176 // If this is a young generation, the maximum number of bytes that can be
177 // allocated in this generation before a GC is triggered.
178 virtual size_t capacity_before_gc() const { return 0; }
179
180 // The largest number of contiguous free bytes in the generation,
181 // including expansion (Assumes called at a safepoint.)
182 virtual size_t contiguous_available() const = 0;
183 // The largest number of contiguous free bytes in this or any higher generation.
184 virtual size_t max_contiguous_available() const;
185
186 // Returns true if promotions of the specified amount are
187 // likely to succeed without a promotion failure.
188 // Promotion of the full amount is not guaranteed but
189 // might be attempted in the worst case.
190 virtual bool promotion_attempt_is_safe(size_t max_promotion_in_bytes) const;
191
192 // For a non-young generation, this interface can be used to inform a
193 // generation that a promotion attempt into that generation failed.
194 // Typically used to enable diagnostic output for post-mortem analysis,
195 // but other uses of the interface are not ruled out.
196 virtual void promotion_failure_occurred() { /* does nothing */ }
197
198 // Return an estimate of the maximum allocation that could be performed
199 // in the generation without triggering any collection or expansion
200 // activity. It is "unsafe" because no locks are taken; the result
201 // should be treated as an approximation, not a guarantee, for use in
202 // heuristic resizing decisions.
203 virtual size_t unsafe_max_alloc_nogc() const = 0;
204
205 // Returns true if this generation cannot be expanded further
206 // without a GC. Override as appropriate.
207 virtual bool is_maximal_no_gc() const {
208 return _virtual_space.uncommitted_size() == 0;
209 }
210
211 MemRegion reserved() const { return _reserved; }
212
213 // Returns a region guaranteed to contain all the objects in the
214 // generation.
215 virtual MemRegion used_region() const { return _reserved; }
216
217 MemRegion prev_used_region() const { return _prev_used_region; }
218 virtual void save_used_region() { _prev_used_region = used_region(); }
219
220 // Returns "TRUE" iff "p" points into the committed areas in the generation.
221 // For some kinds of generations, this may be an expensive operation.
222 // To avoid performance problems stemming from its inadvertent use in
223 // product jvm's, we restrict its use to assertion checking or
224 // verification only.
225 virtual bool is_in(const void* p) const;
226
227 /* Returns "TRUE" iff "p" points into the reserved area of the generation. */
228 bool is_in_reserved(const void* p) const {
229 return _reserved.contains(p);
230 }
231
232 // Check that the generation kind is DefNewGeneration or a sub
233 // class of DefNewGeneration and return a DefNewGeneration*
234 DefNewGeneration* as_DefNewGeneration();
235
236 // If some space in the generation contains the given "addr", return a
237 // pointer to that space, else return "NULL".
238 virtual Space* space_containing(const void* addr) const;
239
240 // Iteration - do not use for time critical operations
241 virtual void space_iterate(SpaceClosure* blk, bool usedOnly = false) = 0;
242
243 // Returns the first space, if any, in the generation that can participate
244 // in compaction, or else "NULL".
245 virtual CompactibleSpace* first_compaction_space() const = 0;
246
247 // Returns "true" iff this generation should be used to allocate an
248 // object of the given size. Young generations might
249 // wish to exclude very large objects, for example, since, if allocated
250 // often, they would greatly increase the frequency of young-gen
251 // collection.
252 virtual bool should_allocate(size_t word_size, bool is_tlab) {
253 bool result = false;
254 size_t overflow_limit = (size_t)1 << (BitsPerSize_t - LogHeapWordSize);
255 if (!is_tlab || supports_tlab_allocation()) {
256 result = (word_size > 0) && (word_size < overflow_limit);
257 }
258 return result;
259 }
260
261 // Allocate and returns a block of the requested size, or returns "NULL".
262 // Assumes the caller has done any necessary locking.
263 virtual HeapWord* allocate(size_t word_size, bool is_tlab) = 0;
264
265 // Like "allocate", but performs any necessary locking internally.
266 virtual HeapWord* par_allocate(size_t word_size, bool is_tlab) = 0;
267
268 // A 'younger' gen has reached an allocation limit, and uses this to notify
269 // the next older gen. The return value is a new limit, or NULL if none. The
270 // caller must do the necessary locking.
271 virtual HeapWord* allocation_limit_reached(Space* space, HeapWord* top,
272 size_t word_size) {
273 return NULL;
274 }
275
276 // Some generation may offer a region for shared, contiguous allocation,
277 // via inlined code (by exporting the address of the top and end fields
278 // defining the extent of the contiguous allocation region.)
279
280 // This function returns "true" iff the heap supports this kind of
281 // allocation. (More precisely, this means the style of allocation that
282 // increments *top_addr()" with a CAS.) (Default is "no".)
283 // A generation that supports this allocation style must use lock-free
284 // allocation for *all* allocation, since there are times when lock free
285 // allocation will be concurrent with plain "allocate" calls.
286 virtual bool supports_inline_contig_alloc() const { return false; }
287
288 // These functions return the addresses of the fields that define the
289 // boundaries of the contiguous allocation area. (These fields should be
290 // physically near to one another.)
291 virtual HeapWord** top_addr() const { return NULL; }
292 virtual HeapWord** end_addr() const { return NULL; }
293
294 // Thread-local allocation buffers
295 virtual bool supports_tlab_allocation() const { return false; }
296 virtual size_t tlab_capacity() const {
297 guarantee(false, "Generation doesn't support thread local allocation buffers");
298 return 0;
299 }
300 virtual size_t tlab_used() const {
301 guarantee(false, "Generation doesn't support thread local allocation buffers");
302 return 0;
303 }
304 virtual size_t unsafe_max_tlab_alloc() const {
305 guarantee(false, "Generation doesn't support thread local allocation buffers");
306 return 0;
307 }
308
309 // "obj" is the address of an object in a younger generation. Allocate space
310 // for "obj" in the current (or some higher) generation, and copy "obj" into
311 // the newly allocated space, if possible, returning the result (or NULL if
312 // the allocation failed).
313 //
314 // The "obj_size" argument is just obj->size(), passed along so the caller can
315 // avoid repeating the virtual call to retrieve it.
316 virtual oop promote(oop obj, size_t obj_size);
317
318 // Thread "thread_num" (0 <= i < ParalleGCThreads) wants to promote
319 // object "obj", whose original mark word was "m", and whose size is
320 // "word_sz". If possible, allocate space for "obj", copy obj into it
321 // (taking care to copy "m" into the mark word when done, since the mark
322 // word of "obj" may have been overwritten with a forwarding pointer, and
323 // also taking care to copy the klass pointer *last*. Returns the new
324 // object if successful, or else NULL.
325 virtual oop par_promote(int thread_num,
326 oop obj, markOop m, size_t word_sz);
327
328 // Undo, if possible, the most recent par_promote_alloc allocation by
329 // "thread_num" ("obj", of "word_sz").
330 virtual void par_promote_alloc_undo(int thread_num,
331 HeapWord* obj, size_t word_sz);
332
333 // Informs the current generation that all par_promote_alloc's in the
334 // collection have been completed; any supporting data structures can be
335 // reset. Default is to do nothing.
336 virtual void par_promote_alloc_done(int thread_num) {}
337
338 // Informs the current generation that all oop_since_save_marks_iterates
339 // performed by "thread_num" in the current collection, if any, have been
340 // completed; any supporting data structures can be reset. Default is to
341 // do nothing.
342 virtual void par_oop_since_save_marks_iterate_done(int thread_num) {}
343
344 // This generation will collect all younger generations
345 // during a full collection.
346 virtual bool full_collects_younger_generations() const { return false; }
347
348 // This generation does in-place marking, meaning that mark words
349 // are mutated during the marking phase and presumably reinitialized
350 // to a canonical value after the GC. This is currently used by the
351 // biased locking implementation to determine whether additional
352 // work is required during the GC prologue and epilogue.
353 virtual bool performs_in_place_marking() const { return true; }
354
355 // Returns "true" iff collect() should subsequently be called on this
356 // this generation. See comment below.
357 // This is a generic implementation which can be overridden.
358 //
359 // Note: in the current (1.4) implementation, when genCollectedHeap's
360 // incremental_collection_will_fail flag is set, all allocations are
361 // slow path (the only fast-path place to allocate is DefNew, which
362 // will be full if the flag is set).
363 // Thus, older generations which collect younger generations should
364 // test this flag and collect if it is set.
365 virtual bool should_collect(bool full,
366 size_t word_size,
367 bool is_tlab) {
368 return (full || should_allocate(word_size, is_tlab));
369 }
370
371 // Returns true if the collection is likely to be safely
372 // completed. Even if this method returns true, a collection
373 // may not be guaranteed to succeed, and the system should be
374 // able to safely unwind and recover from that failure, albeit
375 // at some additional cost.
376 virtual bool collection_attempt_is_safe() {
377 guarantee(false, "Are you sure you want to call this method?");
378 return true;
379 }
380
381 // Perform a garbage collection.
382 // If full is true attempt a full garbage collection of this generation.
383 // Otherwise, attempting to (at least) free enough space to support an
384 // allocation of the given "word_size".
385 virtual void collect(bool full,
386 bool clear_all_soft_refs,
387 size_t word_size,
388 bool is_tlab) = 0;
389
390 // Perform a heap collection, attempting to create (at least) enough
391 // space to support an allocation of the given "word_size". If
392 // successful, perform the allocation and return the resulting
393 // "oop" (initializing the allocated block). If the allocation is
394 // still unsuccessful, return "NULL".
395 virtual HeapWord* expand_and_allocate(size_t word_size,
396 bool is_tlab,
397 bool parallel = false) = 0;
398
399 // Some generations may require some cleanup or preparation actions before
400 // allowing a collection. The default is to do nothing.
401 virtual void gc_prologue(bool full) {};
402
403 // Some generations may require some cleanup actions after a collection.
404 // The default is to do nothing.
405 virtual void gc_epilogue(bool full) {};
406
407 // Save the high water marks for the used space in a generation.
408 virtual void record_spaces_top() {};
409
410 // Some generations may need to be "fixed-up" after some allocation
411 // activity to make them parsable again. The default is to do nothing.
412 virtual void ensure_parsability() {};
413
414 // Time (in ms) when we were last collected or now if a collection is
415 // in progress.
416 virtual jlong time_of_last_gc(jlong now) {
417 // Both _time_of_last_gc and now are set using a time source
418 // that guarantees monotonically non-decreasing values provided
419 // the underlying platform provides such a source. So we still
420 // have to guard against non-monotonicity.
421 NOT_PRODUCT(
422 if (now < _time_of_last_gc) {
423 warning("time warp: "INT64_FORMAT" to "INT64_FORMAT, (int64_t)_time_of_last_gc, (int64_t)now);
424 }
425 )
426 return _time_of_last_gc;
427 }
428
429 virtual void update_time_of_last_gc(jlong now) {
430 _time_of_last_gc = now;
431 }
432
433 // Generations may keep statistics about collection. This
434 // method updates those statistics. current_level is
435 // the level of the collection that has most recently
436 // occurred. This allows the generation to decide what
437 // statistics are valid to collect. For example, the
438 // generation can decide to gather the amount of promoted data
439 // if the collection of the younger generations has completed.
440 GCStats* gc_stats() const { return _gc_stats; }
441 virtual void update_gc_stats(int current_level, bool full) {}
442
443 // Mark sweep support phase2
444 virtual void prepare_for_compaction(CompactPoint* cp);
445 // Mark sweep support phase3
446 virtual void adjust_pointers();
447 // Mark sweep support phase4
448 virtual void compact();
449 virtual void post_compact() {ShouldNotReachHere();}
450
451 // Support for CMS's rescan. In this general form we return a pointer
452 // to an abstract object that can be used, based on specific previously
453 // decided protocols, to exchange information between generations,
454 // information that may be useful for speeding up certain types of
455 // garbage collectors. A NULL value indicates to the client that
456 // no data recording is expected by the provider. The data-recorder is
457 // expected to be GC worker thread-local, with the worker index
458 // indicated by "thr_num".
459 virtual void* get_data_recorder(int thr_num) { return NULL; }
460 virtual void sample_eden_chunk() {}
461
462 // Some generations may require some cleanup actions before allowing
463 // a verification.
464 virtual void prepare_for_verify() {};
465
466 // Accessing "marks".
467
468 // This function gives a generation a chance to note a point between
469 // collections. For example, a contiguous generation might note the
470 // beginning allocation point post-collection, which might allow some later
471 // operations to be optimized.
472 virtual void save_marks() {}
473
474 // This function allows generations to initialize any "saved marks". That
475 // is, should only be called when the generation is empty.
476 virtual void reset_saved_marks() {}
477
478 // This function is "true" iff any no allocations have occurred in the
479 // generation since the last call to "save_marks".
480 virtual bool no_allocs_since_save_marks() = 0;
481
482 // Apply "cl->apply" to (the addresses of) all reference fields in objects
483 // allocated in the current generation since the last call to "save_marks".
484 // If more objects are allocated in this generation as a result of applying
485 // the closure, iterates over reference fields in those objects as well.
486 // Calls "save_marks" at the end of the iteration.
487 // General signature...
488 virtual void oop_since_save_marks_iterate_v(OopsInGenClosure* cl) = 0;
489 // ...and specializations for de-virtualization. (The general
490 // implementation of the _nv versions call the virtual version.
491 // Note that the _nv suffix is not really semantically necessary,
492 // but it avoids some not-so-useful warnings on Solaris.)
493 #define Generation_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
494 virtual void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \
495 oop_since_save_marks_iterate_v((OopsInGenClosure*)cl); \
496 }
497 SPECIALIZED_SINCE_SAVE_MARKS_CLOSURES(Generation_SINCE_SAVE_MARKS_DECL)
498
499 #undef Generation_SINCE_SAVE_MARKS_DECL
500
501 // The "requestor" generation is performing some garbage collection
502 // action for which it would be useful to have scratch space. If
503 // the target is not the requestor, no gc actions will be required
504 // of the target. The requestor promises to allocate no more than
505 // "max_alloc_words" in the target generation (via promotion say,
506 // if the requestor is a young generation and the target is older).
507 // If the target generation can provide any scratch space, it adds
508 // it to "list", leaving "list" pointing to the head of the
509 // augmented list. The default is to offer no space.
510 virtual void contribute_scratch(ScratchBlock*& list, Generation* requestor,
511 size_t max_alloc_words) {}
512
513 // Give each generation an opportunity to do clean up for any
514 // contributed scratch.
515 virtual void reset_scratch() {};
516
517 // When an older generation has been collected, and perhaps resized,
518 // this method will be invoked on all younger generations (from older to
519 // younger), allowing them to resize themselves as appropriate.
520 virtual void compute_new_size() = 0;
521
522 // Printing
523 virtual const char* name() const = 0;
524 virtual const char* short_name() const = 0;
525
526 int level() const { return _level; }
527
528 // Attributes
529
530 // True iff the given generation may only be the youngest generation.
531 virtual bool must_be_youngest() const = 0;
532 // True iff the given generation may only be the oldest generation.
533 virtual bool must_be_oldest() const = 0;
534
535 // Reference Processing accessor
536 ReferenceProcessor* const ref_processor() { return _ref_processor; }
537
538 // Iteration.
539
540 // Iterate over all the ref-containing fields of all objects in the
541 // generation, calling "cl.do_oop" on each.
542 virtual void oop_iterate(ExtendedOopClosure* cl);
543
544 // Iterate over all objects in the generation, calling "cl.do_object" on
545 // each.
546 virtual void object_iterate(ObjectClosure* cl);
547
548 // Iterate over all safe objects in the generation, calling "cl.do_object" on
549 // each. An object is safe if its references point to other objects in
550 // the heap. This defaults to object_iterate() unless overridden.
551 virtual void safe_object_iterate(ObjectClosure* cl);
552
553 // Apply "cl->do_oop" to (the address of) all and only all the ref fields
554 // in the current generation that contain pointers to objects in younger
555 // generations. Objects allocated since the last "save_marks" call are
556 // excluded.
557 virtual void younger_refs_iterate(OopsInGenClosure* cl) = 0;
558
559 // Inform a generation that it longer contains references to objects
560 // in any younger generation. [e.g. Because younger gens are empty,
561 // clear the card table.]
562 virtual void clear_remembered_set() { }
563
564 // Inform a generation that some of its objects have moved. [e.g. The
565 // generation's spaces were compacted, invalidating the card table.]
566 virtual void invalidate_remembered_set() { }
567
568 // Block abstraction.
569
570 // Returns the address of the start of the "block" that contains the
571 // address "addr". We say "blocks" instead of "object" since some heaps
572 // may not pack objects densely; a chunk may either be an object or a
573 // non-object.
574 virtual HeapWord* block_start(const void* addr) const;
575
576 // Requires "addr" to be the start of a chunk, and returns its size.
577 // "addr + size" is required to be the start of a new chunk, or the end
578 // of the active area of the heap.
579 virtual size_t block_size(const HeapWord* addr) const ;
580
581 // Requires "addr" to be the start of a block, and returns "TRUE" iff
582 // the block is an object.
583 virtual bool block_is_obj(const HeapWord* addr) const;
584
585
586 // PrintGC, PrintGCDetails support
587 void print_heap_change(size_t prev_used) const;
588
589 // PrintHeapAtGC support
590 virtual void print() const;
591 virtual void print_on(outputStream* st) const;
592
593 virtual void verify() = 0;
594
595 struct StatRecord {
596 int invocations;
597 elapsedTimer accumulated_time;
598 StatRecord() :
599 invocations(0),
600 accumulated_time(elapsedTimer()) {}
601 };
602 private:
603 StatRecord _stat_record;
604 public:
605 StatRecord* stat_record() { return &_stat_record; }
606
607 virtual void print_summary_info();
608 virtual void print_summary_info_on(outputStream* st);
609
610 // Performance Counter support
611 virtual void update_counters() = 0;
612 virtual CollectorCounters* counters() { return _gc_counters; }
613 };
614
615 // Class CardGeneration is a generation that is covered by a card table,
616 // and uses a card-size block-offset array to implement block_start.
617
618 // class BlockOffsetArray;
619 // class BlockOffsetArrayContigSpace;
620 class BlockOffsetSharedArray;
621
622 class CardGeneration: public Generation {
623 friend class VMStructs;
624 protected:
625 // This is shared with other generations.
626 GenRemSet* _rs;
627 // This is local to this generation.
628 BlockOffsetSharedArray* _bts;
629
630 // current shrinking effect: this damps shrinking when the heap gets empty.
631 size_t _shrink_factor;
632
633 size_t _min_heap_delta_bytes; // Minimum amount to expand.
634
635 // Some statistics from before gc started.
636 // These are gathered in the gc_prologue (and should_collect)
637 // to control growing/shrinking policy in spite of promotions.
638 size_t _capacity_at_prologue;
639 size_t _used_at_prologue;
640
641 CardGeneration(ReservedSpace rs, size_t initial_byte_size, int level,
642 GenRemSet* remset);
643
644 public:
645
646 // Attempt to expand the generation by "bytes". Expand by at a
647 // minimum "expand_bytes". Return true if some amount (not
648 // necessarily the full "bytes") was done.
649 virtual bool expand(size_t bytes, size_t expand_bytes);
650
651 // Shrink generation with specified size (returns false if unable to shrink)
652 virtual void shrink(size_t bytes) = 0;
653
654 virtual void compute_new_size();
655
656 virtual void clear_remembered_set();
657
658 virtual void invalidate_remembered_set();
659
660 virtual void prepare_for_verify();
661
662 // Grow generation with specified size (returns false if unable to grow)
663 virtual bool grow_by(size_t bytes) = 0;
664 // Grow generation to reserved size.
665 virtual bool grow_to_reserved() = 0;
666 };
667
668 // OneContigSpaceCardGeneration models a heap of old objects contained in a single
669 // contiguous space.
670 //
671 // Garbage collection is performed using mark-compact.
672
673 class OneContigSpaceCardGeneration: public CardGeneration {
674 friend class VMStructs;
675 // Abstractly, this is a subtype that gets access to protected fields.
676 friend class VM_PopulateDumpSharedSpace;
677
678 protected:
679 ContiguousSpace* _the_space; // actual space holding objects
680 WaterMark _last_gc; // watermark between objects allocated before
681 // and after last GC.
682
683 // Grow generation with specified size (returns false if unable to grow)
684 virtual bool grow_by(size_t bytes);
685 // Grow generation to reserved size.
686 virtual bool grow_to_reserved();
687 // Shrink generation with specified size (returns false if unable to shrink)
688 void shrink_by(size_t bytes);
689
690 // Allocation failure
691 virtual bool expand(size_t bytes, size_t expand_bytes);
692 void shrink(size_t bytes);
693
694 // Accessing spaces
695 ContiguousSpace* the_space() const { return _the_space; }
696
697 public:
698 OneContigSpaceCardGeneration(ReservedSpace rs, size_t initial_byte_size,
699 int level, GenRemSet* remset,
700 ContiguousSpace* space) :
701 CardGeneration(rs, initial_byte_size, level, remset),
702 _the_space(space)
703 {}
704
705 inline bool is_in(const void* p) const;
706
707 // Space enquiries
708 size_t capacity() const;
709 size_t used() const;
710 size_t free() const;
711
712 MemRegion used_region() const;
713
714 size_t unsafe_max_alloc_nogc() const;
715 size_t contiguous_available() const;
716
717 // Iteration
718 void object_iterate(ObjectClosure* blk);
719 void space_iterate(SpaceClosure* blk, bool usedOnly = false);
720
721 void younger_refs_iterate(OopsInGenClosure* blk);
722
723 inline CompactibleSpace* first_compaction_space() const;
724
725 virtual inline HeapWord* allocate(size_t word_size, bool is_tlab);
726 virtual inline HeapWord* par_allocate(size_t word_size, bool is_tlab);
727
728 // Accessing marks
729 inline WaterMark top_mark();
730 inline WaterMark bottom_mark();
731
732 #define OneContig_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
733 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl);
734 OneContig_SINCE_SAVE_MARKS_DECL(OopsInGenClosure,_v)
735 SPECIALIZED_SINCE_SAVE_MARKS_CLOSURES(OneContig_SINCE_SAVE_MARKS_DECL)
736
737 void save_marks();
738 void reset_saved_marks();
739 bool no_allocs_since_save_marks();
740
741 inline size_t block_size(const HeapWord* addr) const;
742
743 inline bool block_is_obj(const HeapWord* addr) const;
744
745 virtual void collect(bool full,
746 bool clear_all_soft_refs,
747 size_t size,
748 bool is_tlab);
749 HeapWord* expand_and_allocate(size_t size,
750 bool is_tlab,
751 bool parallel = false);
752
753 virtual void prepare_for_verify();
754
755 virtual void gc_epilogue(bool full);
756
757 virtual void record_spaces_top();
758
759 virtual void verify();
760 virtual void print_on(outputStream* st) const;
761 };
762
763 #endif // SHARE_VM_MEMORY_GENERATION_HPP