1 #ifdef USE_PRAGMA_IDENT_HDR
2 #pragma ident "@(#)generation.hpp 1.195 07/05/17 15:55:02 JVM"
3 #endif
4 /*
5 * Copyright 1997-2008 Sun Microsystems, Inc. All Rights Reserved.
6 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
7 *
8 * This code is free software; you can redistribute it and/or modify it
9 * under the terms of the GNU General Public License version 2 only, as
10 * published by the Free Software Foundation.
11 *
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13 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
15 * version 2 for more details (a copy is included in the LICENSE file that
16 * accompanied this code).
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19 * 2 along with this work; if not, write to the Free Software Foundation,
20 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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22 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
23 * CA 95054 USA or visit www.sun.com if you need additional information or
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26 */
27
28 // A Generation models a heap area for similarly-aged objects.
29 // It will contain one ore more spaces holding the actual objects.
30 //
31 // The Generation class hierarchy:
32 //
33 // Generation - abstract base class
34 // - DefNewGeneration - allocation area (copy collected)
35 // - ParNewGeneration - a DefNewGeneration that is collected by
36 // several threads
37 // - CardGeneration - abstract class adding offset array behavior
38 // - OneContigSpaceCardGeneration - abstract class holding a single
39 // contiguous space with card marking
40 // - TenuredGeneration - tenured (old object) space (markSweepCompact)
41 // - CompactingPermGenGen - reflective object area (klasses, methods, symbols, ...)
42 // - ConcurrentMarkSweepGeneration - Mostly Concurrent Mark Sweep Generation
43 // (Detlefs-Printezis refinement of
44 // Boehm-Demers-Schenker)
45 //
46 // The system configurations currently allowed are:
47 //
48 // DefNewGeneration + TenuredGeneration + PermGeneration
49 // DefNewGeneration + ConcurrentMarkSweepGeneration + ConcurrentMarkSweepPermGen
50 //
51 // ParNewGeneration + TenuredGeneration + PermGeneration
52 // ParNewGeneration + ConcurrentMarkSweepGeneration + ConcurrentMarkSweepPermGen
53 //
54
55 class DefNewGeneration;
56 class GenerationSpec;
57 class CompactibleSpace;
58 class ContiguousSpace;
59 class CompactPoint;
60 class OopsInGenClosure;
61 class OopClosure;
62 class ScanClosure;
63 class FastScanClosure;
64 class GenCollectedHeap;
65 class GenRemSet;
66 class GCStats;
67
68 // A "ScratchBlock" represents a block of memory in one generation usable by
69 // another. It represents "num_words" free words, starting at and including
70 // the address of "this".
71 struct ScratchBlock {
72 ScratchBlock* next;
73 size_t num_words;
74 HeapWord scratch_space[1]; // Actually, of size "num_words-2" (assuming
75 // first two fields are word-sized.)
76 };
77
78
79 class Generation: public CHeapObj {
80 friend class VMStructs;
81 private:
82 jlong _time_of_last_gc; // time when last gc on this generation happened (ms)
83 MemRegion _prev_used_region; // for collectors that want to "remember" a value for
84 // used region at some specific point during collection.
85
86 protected:
87 // Minimum and maximum addresses for memory reserved (not necessarily
88 // committed) for generation.
89 // Used by card marking code. Must not overlap with address ranges of
90 // other generations.
91 MemRegion _reserved;
92
93 // Memory area reserved for generation
94 VirtualSpace _virtual_space;
95
96 // Level in the generation hierarchy.
97 int _level;
98
99 // ("Weak") Reference processing support
100 ReferenceProcessor* _ref_processor;
101
102 // Performance Counters
103 CollectorCounters* _gc_counters;
104
105 // Statistics for garbage collection
106 GCStats* _gc_stats;
107
108 // Returns the next generation in the configuration, or else NULL if this
109 // is the highest generation.
110 Generation* next_gen() const;
111
112 // Initialize the generation.
113 Generation(ReservedSpace rs, size_t initial_byte_size, int level);
114
115 // Apply "cl->do_oop" to (the address of) (exactly) all the ref fields in
116 // "sp" that point into younger generations.
117 // The iteration is only over objects allocated at the start of the
118 // iterations; objects allocated as a result of applying the closure are
119 // not included.
120 void younger_refs_in_space_iterate(Space* sp, OopsInGenClosure* cl);
121
122 public:
123 // The set of possible generation kinds.
124 enum Name {
125 ASParNew,
126 ASConcurrentMarkSweep,
127 DefNew,
128 ParNew,
129 MarkSweepCompact,
130 ConcurrentMarkSweep,
131 Other
132 };
133
134 enum SomePublicConstants {
135 // Generations are GenGrain-aligned and have size that are multiples of
136 // GenGrain.
137 LogOfGenGrain = 16,
138 GenGrain = 1 << LogOfGenGrain
139 };
140
141 // allocate and initialize ("weak") refs processing support
142 virtual void ref_processor_init();
143 void set_ref_processor(ReferenceProcessor* rp) {
144 assert(_ref_processor == NULL, "clobbering existing _ref_processor");
145 _ref_processor = rp;
146 }
147
148 virtual Generation::Name kind() { return Generation::Other; }
149 GenerationSpec* spec();
150
151 // This properly belongs in the collector, but for now this
152 // will do.
153 virtual bool refs_discovery_is_atomic() const { return true; }
154 virtual bool refs_discovery_is_mt() const { return false; }
155
156 // Space enquiries (results in bytes)
157 virtual size_t capacity() const = 0; // The maximum number of object bytes the
158 // generation can currently hold.
159 virtual size_t used() const = 0; // The number of used bytes in the gen.
160 virtual size_t free() const = 0; // The number of free bytes in the gen.
161
162 // Support for java.lang.Runtime.maxMemory(); see CollectedHeap.
163 // Returns the total number of bytes available in a generation
164 // for the allocation of objects.
165 virtual size_t max_capacity() const;
166
167 // If this is a young generation, the maximum number of bytes that can be
168 // allocated in this generation before a GC is triggered.
169 virtual size_t capacity_before_gc() const { return 0; }
170
171 // The largest number of contiguous free bytes in the generation,
172 // including expansion (Assumes called at a safepoint.)
173 virtual size_t contiguous_available() const = 0;
174 // The largest number of contiguous free bytes in this or any higher generation.
175 virtual size_t max_contiguous_available() const;
176
177 // Returns true if promotions of the specified amount can
178 // be attempted safely (without a vm failure).
179 // Promotion of the full amount is not guaranteed but
180 // can be attempted.
181 // younger_handles_promotion_failure
182 // is true if the younger generation handles a promotion
183 // failure.
184 virtual bool promotion_attempt_is_safe(size_t promotion_in_bytes,
185 bool younger_handles_promotion_failure) const;
186
187 // Return an estimate of the maximum allocation that could be performed
188 // in the generation without triggering any collection or expansion
189 // activity. It is "unsafe" because no locks are taken; the result
190 // should be treated as an approximation, not a guarantee, for use in
191 // heuristic resizing decisions.
192 virtual size_t unsafe_max_alloc_nogc() const = 0;
193
194 // Returns true if this generation cannot be expanded further
195 // without a GC. Override as appropriate.
196 virtual bool is_maximal_no_gc() const {
197 return _virtual_space.uncommitted_size() == 0;
198 }
199
200 MemRegion reserved() const { return _reserved; }
201
202 // Returns a region guaranteed to contain all the objects in the
203 // generation.
204 virtual MemRegion used_region() const { return _reserved; }
205
206 MemRegion prev_used_region() const { return _prev_used_region; }
207 virtual void save_used_region() { _prev_used_region = used_region(); }
208
209 // Returns "TRUE" iff "p" points into an allocated object in the generation.
210 // For some kinds of generations, this may be an expensive operation.
211 // To avoid performance problems stemming from its inadvertent use in
212 // product jvm's, we restrict its use to assertion checking or
213 // verification only.
214 virtual bool is_in(const void* p) const;
215
216 /* Returns "TRUE" iff "p" points into the reserved area of the generation. */
217 bool is_in_reserved(const void* p) const {
218 return _reserved.contains(p);
219 }
220
221 // Check that the generation kind is DefNewGeneration or a sub
222 // class of DefNewGeneration and return a DefNewGeneration*
223 DefNewGeneration* as_DefNewGeneration();
224
225 // If some space in the generation contains the given "addr", return a
226 // pointer to that space, else return "NULL".
227 virtual Space* space_containing(const void* addr) const;
228
229 // Iteration - do not use for time critical operations
230 virtual void space_iterate(SpaceClosure* blk, bool usedOnly = false) = 0;
231
232 // Returns the first space, if any, in the generation that can participate
233 // in compaction, or else "NULL".
234 virtual CompactibleSpace* first_compaction_space() const = 0;
235
236 // Returns "true" iff this generation should be used to allocate an
237 // object of the given size. Young generations might
238 // wish to exclude very large objects, for example, since, if allocated
239 // often, they would greatly increase the frequency of young-gen
240 // collection.
241 virtual bool should_allocate(size_t word_size, bool is_tlab) {
242 bool result = false;
243 size_t overflow_limit = (size_t)1 << (BitsPerSize_t - LogHeapWordSize);
244 if (!is_tlab || supports_tlab_allocation()) {
245 result = (word_size > 0) && (word_size < overflow_limit);
246 }
247 return result;
248 }
249
250 // Allocate and returns a block of the requested size, or returns "NULL".
251 // Assumes the caller has done any necessary locking.
252 virtual HeapWord* allocate(size_t word_size, bool is_tlab) = 0;
253
254 // Like "allocate", but performs any necessary locking internally.
255 virtual HeapWord* par_allocate(size_t word_size, bool is_tlab) = 0;
256
257 // A 'younger' gen has reached an allocation limit, and uses this to notify
258 // the next older gen. The return value is a new limit, or NULL if none. The
259 // caller must do the necessary locking.
260 virtual HeapWord* allocation_limit_reached(Space* space, HeapWord* top,
261 size_t word_size) {
262 return NULL;
263 }
264
265 // Some generation may offer a region for shared, contiguous allocation,
266 // via inlined code (by exporting the address of the top and end fields
267 // defining the extent of the contiguous allocation region.)
268
269 // This function returns "true" iff the heap supports this kind of
270 // allocation. (More precisely, this means the style of allocation that
271 // increments *top_addr()" with a CAS.) (Default is "no".)
272 // A generation that supports this allocation style must use lock-free
273 // allocation for *all* allocation, since there are times when lock free
274 // allocation will be concurrent with plain "allocate" calls.
275 virtual bool supports_inline_contig_alloc() const { return false; }
276
277 // These functions return the addresses of the fields that define the
278 // boundaries of the contiguous allocation area. (These fields should be
279 // physicall near to one another.)
280 virtual HeapWord** top_addr() const { return NULL; }
281 virtual HeapWord** end_addr() const { return NULL; }
282
283 // Thread-local allocation buffers
284 virtual bool supports_tlab_allocation() const { return false; }
285 virtual size_t tlab_capacity() const {
286 guarantee(false, "Generation doesn't support thread local allocation buffers");
287 return 0;
288 }
289 virtual size_t unsafe_max_tlab_alloc() const {
290 guarantee(false, "Generation doesn't support thread local allocation buffers");
291 return 0;
292 }
293
294 // "obj" is the address of an object in a younger generation. Allocate space
295 // for "obj" in the current (or some higher) generation, and copy "obj" into
296 // the newly allocated space, if possible, returning the result (or NULL if
297 // the allocation failed).
298 //
299 // The "obj_size" argument is just obj->size(), passed along so the caller can
300 // avoid repeating the virtual call to retrieve it.
301 virtual oop promote(oop obj, size_t obj_size);
302
303 // Thread "thread_num" (0 <= i < ParalleGCThreads) wants to promote
304 // object "obj", whose original mark word was "m", and whose size is
305 // "word_sz". If possible, allocate space for "obj", copy obj into it
306 // (taking care to copy "m" into the mark word when done, since the mark
307 // word of "obj" may have been overwritten with a forwarding pointer, and
308 // also taking care to copy the klass pointer *last*. Returns the new
309 // object if successful, or else NULL.
310 virtual oop par_promote(int thread_num,
311 oop obj, markOop m, size_t word_sz);
312
313 // Undo, if possible, the most recent par_promote_alloc allocation by
314 // "thread_num" ("obj", of "word_sz").
315 virtual void par_promote_alloc_undo(int thread_num,
316 HeapWord* obj, size_t word_sz);
317
318 // Informs the current generation that all par_promote_alloc's in the
319 // collection have been completed; any supporting data structures can be
320 // reset. Default is to do nothing.
321 virtual void par_promote_alloc_done(int thread_num) {}
322
323 // Informs the current generation that all oop_since_save_marks_iterates
324 // performed by "thread_num" in the current collection, if any, have been
325 // completed; any supporting data structures can be reset. Default is to
326 // do nothing.
327 virtual void par_oop_since_save_marks_iterate_done(int thread_num) {}
328
329 // This generation will collect all younger generations
330 // during a full collection.
331 virtual bool full_collects_younger_generations() const { return false; }
332
333 // This generation does in-place marking, meaning that mark words
334 // are mutated during the marking phase and presumably reinitialized
335 // to a canonical value after the GC. This is currently used by the
336 // biased locking implementation to determine whether additional
337 // work is required during the GC prologue and epilogue.
338 virtual bool performs_in_place_marking() const { return true; }
339
340 // Returns "true" iff collect() should subsequently be called on this
341 // this generation. See comment below.
342 // This is a generic implementation which can be overridden.
343 //
344 // Note: in the current (1.4) implementation, when genCollectedHeap's
345 // incremental_collection_will_fail flag is set, all allocations are
346 // slow path (the only fast-path place to allocate is DefNew, which
347 // will be full if the flag is set).
348 // Thus, older generations which collect younger generations should
349 // test this flag and collect if it is set.
350 virtual bool should_collect(bool full,
351 size_t word_size,
352 bool is_tlab) {
353 return (full || should_allocate(word_size, is_tlab));
354 }
355
356 // Perform a garbage collection.
357 // If full is true attempt a full garbage collection of this generation.
358 // Otherwise, attempting to (at least) free enough space to support an
359 // allocation of the given "word_size".
360 virtual void collect(bool full,
361 bool clear_all_soft_refs,
362 size_t word_size,
363 bool is_tlab) = 0;
364
365 // Perform a heap collection, attempting to create (at least) enough
366 // space to support an allocation of the given "word_size". If
367 // successful, perform the allocation and return the resulting
368 // "oop" (initializing the allocated block). If the allocation is
369 // still unsuccessful, return "NULL".
370 virtual HeapWord* expand_and_allocate(size_t word_size,
371 bool is_tlab,
372 bool parallel = false) = 0;
373
374 // Some generations may require some cleanup or preparation actions before
375 // allowing a collection. The default is to do nothing.
376 virtual void gc_prologue(bool full) {};
377
378 // Some generations may require some cleanup actions after a collection.
379 // The default is to do nothing.
380 virtual void gc_epilogue(bool full) {};
381
382 // Save the high water marks for the used space in a generation.
383 virtual void record_spaces_top() {};
384
385 // Some generations may need to be "fixed-up" after some allocation
386 // activity to make them parsable again. The default is to do nothing.
387 virtual void ensure_parsability() {};
388
389 // Time (in ms) when we were last collected or now if a collection is
390 // in progress.
391 virtual jlong time_of_last_gc(jlong now) {
392 // XXX See note in genCollectedHeap::millis_since_last_gc()
393 NOT_PRODUCT(
394 if (now < _time_of_last_gc) {
395 warning("time warp: %d to %d", _time_of_last_gc, now);
396 }
397 )
398 return _time_of_last_gc;
399 }
400
401 virtual void update_time_of_last_gc(jlong now) {
402 _time_of_last_gc = now;
403 }
404
405 // Generations may keep statistics about collection. This
406 // method updates those statistics. current_level is
407 // the level of the collection that has most recently
408 // occurred. This allows the generation to decide what
409 // statistics are valid to collect. For example, the
410 // generation can decide to gather the amount of promoted data
411 // if the collection of the younger generations has completed.
412 GCStats* gc_stats() const { return _gc_stats; }
413 virtual void update_gc_stats(int current_level, bool full) {}
414
415 // Mark sweep support phase2
416 virtual void prepare_for_compaction(CompactPoint* cp);
417 // Mark sweep support phase3
418 virtual void pre_adjust_pointers() {ShouldNotReachHere();}
419 virtual void adjust_pointers();
420 // Mark sweep support phase4
421 virtual void compact();
422 virtual void post_compact() {ShouldNotReachHere();}
423
424 // Support for CMS's rescan. In this general form we return a pointer
425 // to an abstract object that can be used, based on specific previously
426 // decided protocols, to exchange information between generations,
427 // information that may be useful for speeding up certain types of
428 // garbage collectors. A NULL value indicates to the client that
429 // no data recording is expected by the provider. The data-recorder is
430 // expected to be GC worker thread-local, with the worker index
431 // indicated by "thr_num".
432 virtual void* get_data_recorder(int thr_num) { return NULL; }
433
434 // Some generations may require some cleanup actions before allowing
435 // a verification.
436 virtual void prepare_for_verify() {};
437
438 // Accessing "marks".
439
440 // This function gives a generation a chance to note a point between
441 // collections. For example, a contiguous generation might note the
442 // beginning allocation point post-collection, which might allow some later
443 // operations to be optimized.
444 virtual void save_marks() {}
445
446 // This function allows generations to initialize any "saved marks". That
447 // is, should only be called when the generation is empty.
448 virtual void reset_saved_marks() {}
449
450 // This function is "true" iff any no allocations have occurred in the
451 // generation since the last call to "save_marks".
452 virtual bool no_allocs_since_save_marks() = 0;
453
454 // Apply "cl->apply" to (the addresses of) all reference fields in objects
455 // allocated in the current generation since the last call to "save_marks".
456 // If more objects are allocated in this generation as a result of applying
457 // the closure, iterates over reference fields in those objects as well.
458 // Calls "save_marks" at the end of the iteration.
459 // General signature...
460 virtual void oop_since_save_marks_iterate_v(OopsInGenClosure* cl) = 0;
461 // ...and specializations for de-virtualization. (The general
462 // implemention of the _nv versions call the virtual version.
463 // Note that the _nv suffix is not really semantically necessary,
464 // but it avoids some not-so-useful warnings on Solaris.)
465 #define Generation_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
466 virtual void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \
467 oop_since_save_marks_iterate_v((OopsInGenClosure*)cl); \
468 }
469 SPECIALIZED_SINCE_SAVE_MARKS_CLOSURES(Generation_SINCE_SAVE_MARKS_DECL)
470
471 #undef Generation_SINCE_SAVE_MARKS_DECL
472
473 // The "requestor" generation is performing some garbage collection
474 // action for which it would be useful to have scratch space. If
475 // the target is not the requestor, no gc actions will be required
476 // of the target. The requestor promises to allocate no more than
477 // "max_alloc_words" in the target generation (via promotion say,
478 // if the requestor is a young generation and the target is older).
479 // If the target generation can provide any scratch space, it adds
480 // it to "list", leaving "list" pointing to the head of the
481 // augmented list. The default is to offer no space.
482 virtual void contribute_scratch(ScratchBlock*& list, Generation* requestor,
483 size_t max_alloc_words) {}
484
485 // Give each generation an opportunity to do clean up for any
486 // contributed scratch.
487 virtual void reset_scratch() {};
488
489 // When an older generation has been collected, and perhaps resized,
490 // this method will be invoked on all younger generations (from older to
491 // younger), allowing them to resize themselves as appropriate.
492 virtual void compute_new_size() = 0;
493
494 // Printing
495 virtual const char* name() const = 0;
496 virtual const char* short_name() const = 0;
497
498 int level() const { return _level; }
499
500 // Attributes
501
502 // True iff the given generation may only be the youngest generation.
503 virtual bool must_be_youngest() const = 0;
504 // True iff the given generation may only be the oldest generation.
505 virtual bool must_be_oldest() const = 0;
506
507 // Reference Processing accessor
508 ReferenceProcessor* const ref_processor() { return _ref_processor; }
509
510 // Iteration.
511
512 // Iterate over all the ref-containing fields of all objects in the
513 // generation, calling "cl.do_oop" on each.
514 virtual void oop_iterate(OopClosure* cl);
515
516 // Same as above, restricted to the intersection of a memory region and
517 // the generation.
518 virtual void oop_iterate(MemRegion mr, OopClosure* cl);
519
520 // Iterate over all objects in the generation, calling "cl.do_object" on
521 // each.
522 virtual void object_iterate(ObjectClosure* cl);
523
524 // Iterate over all objects allocated in the generation since the last
525 // collection, calling "cl.do_object" on each. The generation must have
526 // been initialized properly to support this function, or else this call
527 // will fail.
528 virtual void object_iterate_since_last_GC(ObjectClosure* cl) = 0;
529
530 // Apply "cl->do_oop" to (the address of) all and only all the ref fields
531 // in the current generation that contain pointers to objects in younger
532 // generations. Objects allocated since the last "save_marks" call are
533 // excluded.
534 virtual void younger_refs_iterate(OopsInGenClosure* cl) = 0;
535
536 // Inform a generation that it longer contains references to objects
537 // in any younger generation. [e.g. Because younger gens are empty,
538 // clear the card table.]
539 virtual void clear_remembered_set() { }
540
541 // Inform a generation that some of its objects have moved. [e.g. The
542 // generation's spaces were compacted, invalidating the card table.]
543 virtual void invalidate_remembered_set() { }
544
545 // Block abstraction.
546
547 // Returns the address of the start of the "block" that contains the
548 // address "addr". We say "blocks" instead of "object" since some heaps
549 // may not pack objects densely; a chunk may either be an object or a
550 // non-object.
551 virtual HeapWord* block_start(const void* addr) const;
552
553 // Requires "addr" to be the start of a chunk, and returns its size.
554 // "addr + size" is required to be the start of a new chunk, or the end
555 // of the active area of the heap.
556 virtual size_t block_size(const HeapWord* addr) const ;
557
558 // Requires "addr" to be the start of a block, and returns "TRUE" iff
559 // the block is an object.
560 virtual bool block_is_obj(const HeapWord* addr) const;
561
562
563 // PrintGC, PrintGCDetails support
564 void print_heap_change(size_t prev_used) const;
565
566 // PrintHeapAtGC support
567 virtual void print() const;
568 virtual void print_on(outputStream* st) const;
569
570 virtual void verify(bool allow_dirty) = 0;
571
572 struct StatRecord {
573 int invocations;
574 elapsedTimer accumulated_time;
575 StatRecord() :
576 invocations(0),
577 accumulated_time(elapsedTimer()) {}
578 };
579 private:
580 StatRecord _stat_record;
581 public:
582 StatRecord* stat_record() { return &_stat_record; }
583
584 virtual void print_summary_info();
585 virtual void print_summary_info_on(outputStream* st);
586
587 // Performance Counter support
588 virtual void update_counters() = 0;
589 virtual CollectorCounters* counters() { return _gc_counters; }
590 };
591
592 // Class CardGeneration is a generation that is covered by a card table,
593 // and uses a card-size block-offset array to implement block_start.
594
595 // class BlockOffsetArray;
596 // class BlockOffsetArrayContigSpace;
597 class BlockOffsetSharedArray;
598
599 class CardGeneration: public Generation {
600 friend class VMStructs;
601 protected:
602 // This is shared with other generations.
603 GenRemSet* _rs;
604 // This is local to this generation.
605 BlockOffsetSharedArray* _bts;
606
607 CardGeneration(ReservedSpace rs, size_t initial_byte_size, int level,
608 GenRemSet* remset);
609
610 public:
611
612 // Attempt to expand the generation by "bytes". Expand by at a
613 // minimum "expand_bytes". Return true if some amount (not
614 // necessarily the full "bytes") was done.
615 virtual bool expand(size_t bytes, size_t expand_bytes);
616
617 virtual void clear_remembered_set();
618
619 virtual void invalidate_remembered_set();
620
621 virtual void prepare_for_verify();
622
623 // Grow generation with specified size (returns false if unable to grow)
624 virtual bool grow_by(size_t bytes) = 0;
625 // Grow generation to reserved size.
626 virtual bool grow_to_reserved() = 0;
627 };
628
629 // OneContigSpaceCardGeneration models a heap of old objects contained in a single
630 // contiguous space.
631 //
632 // Garbage collection is performed using mark-compact.
633
634 class OneContigSpaceCardGeneration: public CardGeneration {
635 friend class VMStructs;
636 // Abstractly, this is a subtype that gets access to protected fields.
637 friend class CompactingPermGen;
638 friend class VM_PopulateDumpSharedSpace;
639
640 protected:
641 size_t _min_heap_delta_bytes; // Minimum amount to expand.
642 ContiguousSpace* _the_space; // actual space holding objects
643 WaterMark _last_gc; // watermark between objects allocated before
644 // and after last GC.
645
646 // Grow generation with specified size (returns false if unable to grow)
647 virtual bool grow_by(size_t bytes);
648 // Grow generation to reserved size.
649 virtual bool grow_to_reserved();
650 // Shrink generation with specified size (returns false if unable to shrink)
651 void shrink_by(size_t bytes);
652
653 // Allocation failure
654 virtual bool expand(size_t bytes, size_t expand_bytes);
655 void shrink(size_t bytes);
656
657 // Accessing spaces
658 ContiguousSpace* the_space() const { return _the_space; }
659
660 public:
661 OneContigSpaceCardGeneration(ReservedSpace rs, size_t initial_byte_size,
662 size_t min_heap_delta_bytes,
663 int level, GenRemSet* remset,
664 ContiguousSpace* space) :
665 CardGeneration(rs, initial_byte_size, level, remset),
666 _the_space(space), _min_heap_delta_bytes(min_heap_delta_bytes)
667 {}
668
669 inline bool is_in(const void* p) const;
670
671 // Space enquiries
672 size_t capacity() const;
673 size_t used() const;
674 size_t free() const;
675
676 MemRegion used_region() const;
677
678 size_t unsafe_max_alloc_nogc() const;
679 size_t contiguous_available() const;
680
681 // Iteration
682 void object_iterate(ObjectClosure* blk);
683 void space_iterate(SpaceClosure* blk, bool usedOnly = false);
684 void object_iterate_since_last_GC(ObjectClosure* cl);
685
686 void younger_refs_iterate(OopsInGenClosure* blk);
687
688 inline CompactibleSpace* first_compaction_space() const;
689
690 virtual inline HeapWord* allocate(size_t word_size, bool is_tlab);
691 virtual inline HeapWord* par_allocate(size_t word_size, bool is_tlab);
692
693 // Accessing marks
694 inline WaterMark top_mark();
695 inline WaterMark bottom_mark();
696
697 #define OneContig_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
698 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl);
699 OneContig_SINCE_SAVE_MARKS_DECL(OopsInGenClosure,_v)
700 SPECIALIZED_SINCE_SAVE_MARKS_CLOSURES(OneContig_SINCE_SAVE_MARKS_DECL)
701
702 void save_marks();
703 void reset_saved_marks();
704 bool no_allocs_since_save_marks();
705
706 inline size_t block_size(const HeapWord* addr) const;
707
708 inline bool block_is_obj(const HeapWord* addr) const;
709
710 virtual void collect(bool full,
711 bool clear_all_soft_refs,
712 size_t size,
713 bool is_tlab);
714 HeapWord* expand_and_allocate(size_t size,
715 bool is_tlab,
716 bool parallel = false);
717
718 virtual void prepare_for_verify();
719
720 virtual void gc_epilogue(bool full);
721
722 virtual void record_spaces_top();
723
724 virtual void verify(bool allow_dirty);
725 virtual void print_on(outputStream* st) const;
726 };