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