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