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