1 /*
2 * Copyright (c) 1997, 2009, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 // A Generation models a heap area for similarly-aged objects.
26 // It will contain one ore more spaces holding the actual objects.
27 //
28 // The Generation class hierarchy:
29 //
30 // Generation - abstract base class
31 // - DefNewGeneration - allocation area (copy collected)
32 // - ParNewGeneration - a DefNewGeneration that is collected by
33 // several threads
34 // - CardGeneration - abstract class adding offset array behavior
35 // - OneContigSpaceCardGeneration - abstract class holding a single
36 // contiguous space with card marking
37 // - TenuredGeneration - tenured (old object) space (markSweepCompact)
38 // - CompactingPermGenGen - reflective object area (klasses, methods, symbols, ...)
39 // - ConcurrentMarkSweepGeneration - Mostly Concurrent Mark Sweep Generation
40 // (Detlefs-Printezis refinement of
41 // Boehm-Demers-Schenker)
42 //
43 // The system configurations currently allowed are:
44 //
45 // DefNewGeneration + TenuredGeneration + PermGeneration
46 // DefNewGeneration + ConcurrentMarkSweepGeneration + ConcurrentMarkSweepPermGen
47 //
48 // ParNewGeneration + TenuredGeneration + PermGeneration
49 // ParNewGeneration + ConcurrentMarkSweepGeneration + ConcurrentMarkSweepPermGen
50 //
51
52 class DefNewGeneration;
53 class GenerationSpec;
54 class CompactibleSpace;
55 class ContiguousSpace;
56 class CompactPoint;
57 class OopsInGenClosure;
58 class OopClosure;
59 class ScanClosure;
60 class FastScanClosure;
61 class GenCollectedHeap;
62 class GenRemSet;
63 class GCStats;
64
65 // A "ScratchBlock" represents a block of memory in one generation usable by
66 // another. It represents "num_words" free words, starting at and including
67 // the address of "this".
68 struct ScratchBlock {
69 ScratchBlock* next;
70 size_t num_words;
71 HeapWord scratch_space[1]; // Actually, of size "num_words-2" (assuming
72 // first two fields are word-sized.)
73 };
74
75
76 class Generation: public CHeapObj {
77 friend class VMStructs;
78 private:
79 jlong _time_of_last_gc; // time when last gc on this generation happened (ms)
80 MemRegion _prev_used_region; // for collectors that want to "remember" a value for
81 // used region at some specific point during collection.
82
83 protected:
84 // Minimum and maximum addresses for memory reserved (not necessarily
85 // committed) for generation.
86 // Used by card marking code. Must not overlap with address ranges of
87 // other generations.
88 MemRegion _reserved;
89
90 // Memory area reserved for generation
91 VirtualSpace _virtual_space;
92
93 // Level in the generation hierarchy.
94 int _level;
95
96 // ("Weak") Reference processing support
97 ReferenceProcessor* _ref_processor;
98
99 // Performance Counters
100 CollectorCounters* _gc_counters;
101
102 // Statistics for garbage collection
103 GCStats* _gc_stats;
104
105 // Returns the next generation in the configuration, or else NULL if this
106 // is the highest generation.
107 Generation* next_gen() const;
108
109 // Initialize the generation.
110 Generation(ReservedSpace rs, size_t initial_byte_size, int level);
111
112 // Apply "cl->do_oop" to (the address of) (exactly) all the ref fields in
113 // "sp" that point into younger generations.
114 // The iteration is only over objects allocated at the start of the
115 // iterations; objects allocated as a result of applying the closure are
116 // not included.
117 void younger_refs_in_space_iterate(Space* sp, OopsInGenClosure* cl);
118
119 public:
120 // The set of possible generation kinds.
121 enum Name {
122 ASParNew,
123 ASConcurrentMarkSweep,
124 DefNew,
125 ParNew,
126 MarkSweepCompact,
127 ConcurrentMarkSweep,
128 Other
129 };
130
131 enum SomePublicConstants {
132 // Generations are GenGrain-aligned and have size that are multiples of
133 // GenGrain.
134 // Note: on ARM we add 1 bit for card_table_base to be properly aligned
135 // (we expect its low byte to be zero - see implementation of post_barrier)
136 LogOfGenGrain = 16 ARM_ONLY(+1),
137 GenGrain = 1 << LogOfGenGrain
138 };
139
140 // allocate and initialize ("weak") refs processing support
141 virtual void ref_processor_init();
142 void set_ref_processor(ReferenceProcessor* rp) {
143 assert(_ref_processor == NULL, "clobbering existing _ref_processor");
144 _ref_processor = rp;
145 }
146
147 virtual Generation::Name kind() { return Generation::Other; }
148 GenerationSpec* spec();
149
150 // This properly belongs in the collector, but for now this
151 // will do.
152 virtual bool refs_discovery_is_atomic() const { return true; }
153 virtual bool refs_discovery_is_mt() const { return false; }
154
155 // Space enquiries (results in bytes)
156 virtual size_t capacity() const = 0; // The maximum number of object bytes the
157 // generation can currently hold.
158 virtual size_t used() const = 0; // The number of used bytes in the gen.
159 virtual size_t free() const = 0; // The number of free bytes in the gen.
160
161 // Support for java.lang.Runtime.maxMemory(); see CollectedHeap.
162 // Returns the total number of bytes available in a generation
163 // for the allocation of objects.
164 virtual size_t max_capacity() const;
165
166 // If this is a young generation, the maximum number of bytes that can be
167 // allocated in this generation before a GC is triggered.
168 virtual size_t capacity_before_gc() const { return 0; }
169
170 // The largest number of contiguous free bytes in the generation,
171 // including expansion (Assumes called at a safepoint.)
172 virtual size_t contiguous_available() const = 0;
173 // The largest number of contiguous free bytes in this or any higher generation.
174 virtual size_t max_contiguous_available() const;
175
176 // Returns true if promotions of the specified amount can
177 // be attempted safely (without a vm failure).
178 // Promotion of the full amount is not guaranteed but
179 // can be attempted.
180 // younger_handles_promotion_failure
181 // is true if the younger generation handles a promotion
182 // failure.
183 virtual bool promotion_attempt_is_safe(size_t promotion_in_bytes,
184 bool younger_handles_promotion_failure) const;
185
186 // For a non-young generation, this interface can be used to inform a
187 // generation that a promotion attempt into that generation failed.
188 // Typically used to enable diagnostic output for post-mortem analysis,
189 // but other uses of the interface are not ruled out.
190 virtual void promotion_failure_occurred() { /* does nothing */ }
191
192 // Return an estimate of the maximum allocation that could be performed
193 // in the generation without triggering any collection or expansion
194 // activity. It is "unsafe" because no locks are taken; the result
195 // should be treated as an approximation, not a guarantee, for use in
196 // heuristic resizing decisions.
197 virtual size_t unsafe_max_alloc_nogc() const = 0;
198
199 // Returns true if this generation cannot be expanded further
200 // without a GC. Override as appropriate.
201 virtual bool is_maximal_no_gc() const {
202 return _virtual_space.uncommitted_size() == 0;
203 }
204
205 MemRegion reserved() const { return _reserved; }
206
207 // Returns a region guaranteed to contain all the objects in the
208 // generation.
209 virtual MemRegion used_region() const { return _reserved; }
210
211 MemRegion prev_used_region() const { return _prev_used_region; }
212 virtual void save_used_region() { _prev_used_region = used_region(); }
213
214 // Returns "TRUE" iff "p" points into an allocated object in the generation.
215 // For some kinds of generations, this may be an expensive operation.
216 // To avoid performance problems stemming from its inadvertent use in
217 // product jvm's, we restrict its use to assertion checking or
218 // verification only.
219 virtual bool is_in(const void* p) const;
220
221 /* Returns "TRUE" iff "p" points into the reserved area of the generation. */
222 bool is_in_reserved(const void* p) const {
223 return _reserved.contains(p);
224 }
225
226 // Check that the generation kind is DefNewGeneration or a sub
227 // class of DefNewGeneration and return a DefNewGeneration*
228 DefNewGeneration* as_DefNewGeneration();
229
230 // If some space in the generation contains the given "addr", return a
231 // pointer to that space, else return "NULL".
232 virtual Space* space_containing(const void* addr) const;
233
234 // Iteration - do not use for time critical operations
235 virtual void space_iterate(SpaceClosure* blk, bool usedOnly = false) = 0;
236
237 // Returns the first space, if any, in the generation that can participate
238 // in compaction, or else "NULL".
239 virtual CompactibleSpace* first_compaction_space() const = 0;
240
241 // Returns "true" iff this generation should be used to allocate an
242 // object of the given size. Young generations might
243 // wish to exclude very large objects, for example, since, if allocated
244 // often, they would greatly increase the frequency of young-gen
245 // collection.
246 virtual bool should_allocate(size_t word_size, bool is_tlab) {
247 bool result = false;
248 size_t overflow_limit = (size_t)1 << (BitsPerSize_t - LogHeapWordSize);
249 if (!is_tlab || supports_tlab_allocation()) {
250 result = (word_size > 0) && (word_size < overflow_limit);
251 }
252 return result;
253 }
254
255 // Allocate and returns a block of the requested size, or returns "NULL".
256 // Assumes the caller has done any necessary locking.
257 virtual HeapWord* allocate(size_t word_size, bool is_tlab) = 0;
258
259 // Like "allocate", but performs any necessary locking internally.
260 virtual HeapWord* par_allocate(size_t word_size, bool is_tlab) = 0;
261
262 // A 'younger' gen has reached an allocation limit, and uses this to notify
263 // the next older gen. The return value is a new limit, or NULL if none. The
264 // caller must do the necessary locking.
265 virtual HeapWord* allocation_limit_reached(Space* space, HeapWord* top,
266 size_t word_size) {
267 return NULL;
268 }
269
270 // Some generation may offer a region for shared, contiguous allocation,
271 // via inlined code (by exporting the address of the top and end fields
272 // defining the extent of the contiguous allocation region.)
273
274 // This function returns "true" iff the heap supports this kind of
275 // allocation. (More precisely, this means the style of allocation that
276 // increments *top_addr()" with a CAS.) (Default is "no".)
277 // A generation that supports this allocation style must use lock-free
278 // allocation for *all* allocation, since there are times when lock free
279 // allocation will be concurrent with plain "allocate" calls.
280 virtual bool supports_inline_contig_alloc() const { return false; }
281
282 // These functions return the addresses of the fields that define the
283 // boundaries of the contiguous allocation area. (These fields should be
284 // physicall near to one another.)
285 virtual HeapWord** top_addr() const { return NULL; }
286 virtual HeapWord** end_addr() const { return NULL; }
287
288 // Thread-local allocation buffers
289 virtual bool supports_tlab_allocation() const { return false; }
290 virtual size_t tlab_capacity() const {
291 guarantee(false, "Generation doesn't support thread local allocation buffers");
292 return 0;
293 }
294 virtual size_t unsafe_max_tlab_alloc() const {
295 guarantee(false, "Generation doesn't support thread local allocation buffers");
296 return 0;
297 }
298
299 // "obj" is the address of an object in a younger generation. Allocate space
300 // for "obj" in the current (or some higher) generation, and copy "obj" into
301 // the newly allocated space, if possible, returning the result (or NULL if
302 // the allocation failed).
303 //
304 // The "obj_size" argument is just obj->size(), passed along so the caller can
305 // avoid repeating the virtual call to retrieve it.
306 virtual oop promote(oop obj, size_t obj_size);
307
308 // Thread "thread_num" (0 <= i < ParalleGCThreads) wants to promote
309 // object "obj", whose original mark word was "m", and whose size is
310 // "word_sz". If possible, allocate space for "obj", copy obj into it
311 // (taking care to copy "m" into the mark word when done, since the mark
312 // word of "obj" may have been overwritten with a forwarding pointer, and
313 // also taking care to copy the klass pointer *last*. Returns the new
314 // object if successful, or else NULL.
315 virtual oop par_promote(int thread_num,
316 oop obj, markOop m, size_t word_sz);
317
318 // Undo, if possible, the most recent par_promote_alloc allocation by
319 // "thread_num" ("obj", of "word_sz").
320 virtual void par_promote_alloc_undo(int thread_num,
321 HeapWord* obj, size_t word_sz);
322
323 // Informs the current generation that all par_promote_alloc's in the
324 // collection have been completed; any supporting data structures can be
325 // reset. Default is to do nothing.
326 virtual void par_promote_alloc_done(int thread_num) {}
327
328 // Informs the current generation that all oop_since_save_marks_iterates
329 // performed by "thread_num" in the current collection, if any, have been
330 // completed; any supporting data structures can be reset. Default is to
331 // do nothing.
332 virtual void par_oop_since_save_marks_iterate_done(int thread_num) {}
333
334 // This generation will collect all younger generations
335 // during a full collection.
336 virtual bool full_collects_younger_generations() const { return false; }
337
338 // This generation does in-place marking, meaning that mark words
339 // are mutated during the marking phase and presumably reinitialized
340 // to a canonical value after the GC. This is currently used by the
341 // biased locking implementation to determine whether additional
342 // work is required during the GC prologue and epilogue.
343 virtual bool performs_in_place_marking() const { return true; }
344
345 // Returns "true" iff collect() should subsequently be called on this
346 // this generation. See comment below.
347 // This is a generic implementation which can be overridden.
348 //
349 // Note: in the current (1.4) implementation, when genCollectedHeap's
350 // incremental_collection_will_fail flag is set, all allocations are
351 // slow path (the only fast-path place to allocate is DefNew, which
352 // will be full if the flag is set).
353 // Thus, older generations which collect younger generations should
354 // test this flag and collect if it is set.
355 virtual bool should_collect(bool full,
356 size_t word_size,
357 bool is_tlab) {
358 return (full || should_allocate(word_size, is_tlab));
359 }
360
361 // Perform a garbage collection.
362 // If full is true attempt a full garbage collection of this generation.
363 // Otherwise, attempting to (at least) free enough space to support an
364 // allocation of the given "word_size".
365 virtual void collect(bool full,
366 bool clear_all_soft_refs,
367 size_t word_size,
368 bool is_tlab) = 0;
369
370 // Perform a heap collection, attempting to create (at least) enough
371 // space to support an allocation of the given "word_size". If
372 // successful, perform the allocation and return the resulting
373 // "oop" (initializing the allocated block). If the allocation is
374 // still unsuccessful, return "NULL".
375 virtual HeapWord* expand_and_allocate(size_t word_size,
376 bool is_tlab,
377 bool parallel = false) = 0;
378
379 // Some generations may require some cleanup or preparation actions before
380 // allowing a collection. The default is to do nothing.
381 virtual void gc_prologue(bool full) {};
382
383 // Some generations may require some cleanup actions after a collection.
384 // The default is to do nothing.
385 virtual void gc_epilogue(bool full) {};
386
387 // Save the high water marks for the used space in a generation.
388 virtual void record_spaces_top() {};
389
390 // Some generations may need to be "fixed-up" after some allocation
391 // activity to make them parsable again. The default is to do nothing.
392 virtual void ensure_parsability() {};
393
394 // Time (in ms) when we were last collected or now if a collection is
395 // in progress.
396 virtual jlong time_of_last_gc(jlong now) {
397 // XXX See note in genCollectedHeap::millis_since_last_gc()
398 NOT_PRODUCT(
399 if (now < _time_of_last_gc) {
400 warning("time warp: %d to %d", _time_of_last_gc, now);
401 }
402 )
403 return _time_of_last_gc;
404 }
405
406 virtual void update_time_of_last_gc(jlong now) {
407 _time_of_last_gc = now;
408 }
409
410 // Generations may keep statistics about collection. This
411 // method updates those statistics. current_level is
412 // the level of the collection that has most recently
413 // occurred. This allows the generation to decide what
414 // statistics are valid to collect. For example, the
415 // generation can decide to gather the amount of promoted data
416 // if the collection of the younger generations has completed.
417 GCStats* gc_stats() const { return _gc_stats; }
418 virtual void update_gc_stats(int current_level, bool full) {}
419
420 // Mark sweep support phase2
421 virtual void prepare_for_compaction(CompactPoint* cp);
422 // Mark sweep support phase3
423 virtual void pre_adjust_pointers() {ShouldNotReachHere();}
424 virtual void adjust_pointers();
425 // Mark sweep support phase4
426 virtual void compact();
427 virtual void post_compact() {ShouldNotReachHere();}
428
429 // Support for CMS's rescan. In this general form we return a pointer
430 // to an abstract object that can be used, based on specific previously
431 // decided protocols, to exchange information between generations,
432 // information that may be useful for speeding up certain types of
433 // garbage collectors. A NULL value indicates to the client that
434 // no data recording is expected by the provider. The data-recorder is
435 // expected to be GC worker thread-local, with the worker index
436 // indicated by "thr_num".
437 virtual void* get_data_recorder(int thr_num) { return NULL; }
438
439 // Some generations may require some cleanup actions before allowing
440 // a verification.
441 virtual void prepare_for_verify() {};
442
443 // Accessing "marks".
444
445 // This function gives a generation a chance to note a point between
446 // collections. For example, a contiguous generation might note the
447 // beginning allocation point post-collection, which might allow some later
448 // operations to be optimized.
449 virtual void save_marks() {}
450
451 // This function allows generations to initialize any "saved marks". That
452 // is, should only be called when the generation is empty.
453 virtual void reset_saved_marks() {}
454
455 // This function is "true" iff any no allocations have occurred in the
456 // generation since the last call to "save_marks".
457 virtual bool no_allocs_since_save_marks() = 0;
458
459 // Apply "cl->apply" to (the addresses of) all reference fields in objects
460 // allocated in the current generation since the last call to "save_marks".
461 // If more objects are allocated in this generation as a result of applying
462 // the closure, iterates over reference fields in those objects as well.
463 // Calls "save_marks" at the end of the iteration.
464 // General signature...
465 virtual void oop_since_save_marks_iterate_v(OopsInGenClosure* cl) = 0;
466 // ...and specializations for de-virtualization. (The general
467 // implemention of the _nv versions call the virtual version.
468 // Note that the _nv suffix is not really semantically necessary,
469 // but it avoids some not-so-useful warnings on Solaris.)
470 #define Generation_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
471 virtual void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \
472 oop_since_save_marks_iterate_v((OopsInGenClosure*)cl); \
473 }
474 SPECIALIZED_SINCE_SAVE_MARKS_CLOSURES(Generation_SINCE_SAVE_MARKS_DECL)
475
476 #undef Generation_SINCE_SAVE_MARKS_DECL
477
478 // The "requestor" generation is performing some garbage collection
479 // action for which it would be useful to have scratch space. If
480 // the target is not the requestor, no gc actions will be required
481 // of the target. The requestor promises to allocate no more than
482 // "max_alloc_words" in the target generation (via promotion say,
483 // if the requestor is a young generation and the target is older).
484 // If the target generation can provide any scratch space, it adds
485 // it to "list", leaving "list" pointing to the head of the
486 // augmented list. The default is to offer no space.
487 virtual void contribute_scratch(ScratchBlock*& list, Generation* requestor,
488 size_t max_alloc_words) {}
489
490 // Give each generation an opportunity to do clean up for any
491 // contributed scratch.
492 virtual void reset_scratch() {};
493
494 // When an older generation has been collected, and perhaps resized,
495 // this method will be invoked on all younger generations (from older to
496 // younger), allowing them to resize themselves as appropriate.
497 virtual void compute_new_size() = 0;
498
499 // Printing
500 virtual const char* name() const = 0;
501 virtual const char* short_name() const = 0;
502
503 int level() const { return _level; }
504
505 // Attributes
506
507 // True iff the given generation may only be the youngest generation.
508 virtual bool must_be_youngest() const = 0;
509 // True iff the given generation may only be the oldest generation.
510 virtual bool must_be_oldest() const = 0;
511
512 // Reference Processing accessor
513 ReferenceProcessor* const ref_processor() { return _ref_processor; }
514
515 // Iteration.
516
517 // Iterate over all the ref-containing fields of all objects in the
518 // generation, calling "cl.do_oop" on each.
519 virtual void oop_iterate(OopClosure* cl);
520
521 // Same as above, restricted to the intersection of a memory region and
522 // the generation.
523 virtual void oop_iterate(MemRegion mr, OopClosure* cl);
524
525 // Iterate over all objects in the generation, calling "cl.do_object" on
526 // each.
527 virtual void object_iterate(ObjectClosure* cl);
528
529 // Iterate over all safe objects in the generation, calling "cl.do_object" on
530 // each. An object is safe if its references point to other objects in
531 // the heap. This defaults to object_iterate() unless overridden.
532 virtual void safe_object_iterate(ObjectClosure* cl);
533
534 // Iterate over all objects allocated in the generation since the last
535 // collection, calling "cl.do_object" on each. The generation must have
536 // been initialized properly to support this function, or else this call
537 // will fail.
538 virtual void object_iterate_since_last_GC(ObjectClosure* cl) = 0;
539
540 // Apply "cl->do_oop" to (the address of) all and only all the ref fields
541 // in the current generation that contain pointers to objects in younger
542 // generations. Objects allocated since the last "save_marks" call are
543 // excluded.
544 virtual void younger_refs_iterate(OopsInGenClosure* cl) = 0;
545
546 // Inform a generation that it longer contains references to objects
547 // in any younger generation. [e.g. Because younger gens are empty,
548 // clear the card table.]
549 virtual void clear_remembered_set() { }
550
551 // Inform a generation that some of its objects have moved. [e.g. The
552 // generation's spaces were compacted, invalidating the card table.]
553 virtual void invalidate_remembered_set() { }
554
555 // Block abstraction.
556
557 // Returns the address of the start of the "block" that contains the
558 // address "addr". We say "blocks" instead of "object" since some heaps
559 // may not pack objects densely; a chunk may either be an object or a
560 // non-object.
561 virtual HeapWord* block_start(const void* addr) const;
562
563 // Requires "addr" to be the start of a chunk, and returns its size.
564 // "addr + size" is required to be the start of a new chunk, or the end
565 // of the active area of the heap.
566 virtual size_t block_size(const HeapWord* addr) const ;
567
568 // Requires "addr" to be the start of a block, and returns "TRUE" iff
569 // the block is an object.
570 virtual bool block_is_obj(const HeapWord* addr) const;
571
572
573 // PrintGC, PrintGCDetails support
574 void print_heap_change(size_t prev_used) const;
575
576 // PrintHeapAtGC support
577 virtual void print() const;
578 virtual void print_on(outputStream* st) const;
579
580 virtual void verify(bool allow_dirty) = 0;
581
582 struct StatRecord {
583 int invocations;
584 elapsedTimer accumulated_time;
585 StatRecord() :
586 invocations(0),
587 accumulated_time(elapsedTimer()) {}
588 };
589 private:
590 StatRecord _stat_record;
591 public:
592 StatRecord* stat_record() { return &_stat_record; }
593
594 virtual void print_summary_info();
595 virtual void print_summary_info_on(outputStream* st);
596
597 // Performance Counter support
598 virtual void update_counters() = 0;
599 virtual CollectorCounters* counters() { return _gc_counters; }
600 };
601
602 // Class CardGeneration is a generation that is covered by a card table,
603 // and uses a card-size block-offset array to implement block_start.
604
605 // class BlockOffsetArray;
606 // class BlockOffsetArrayContigSpace;
607 class BlockOffsetSharedArray;
608
609 class CardGeneration: public Generation {
610 friend class VMStructs;
611 protected:
612 // This is shared with other generations.
613 GenRemSet* _rs;
614 // This is local to this generation.
615 BlockOffsetSharedArray* _bts;
616
617 CardGeneration(ReservedSpace rs, size_t initial_byte_size, int level,
618 GenRemSet* remset);
619
620 public:
621
622 // Attempt to expand the generation by "bytes". Expand by at a
623 // minimum "expand_bytes". Return true if some amount (not
624 // necessarily the full "bytes") was done.
625 virtual bool expand(size_t bytes, size_t expand_bytes);
626
627 virtual void clear_remembered_set();
628
629 virtual void invalidate_remembered_set();
630
631 virtual void prepare_for_verify();
632
633 // Grow generation with specified size (returns false if unable to grow)
634 virtual bool grow_by(size_t bytes) = 0;
635 // Grow generation to reserved size.
636 virtual bool grow_to_reserved() = 0;
637 };
638
639 // OneContigSpaceCardGeneration models a heap of old objects contained in a single
640 // contiguous space.
641 //
642 // Garbage collection is performed using mark-compact.
643
644 class OneContigSpaceCardGeneration: public CardGeneration {
645 friend class VMStructs;
646 // Abstractly, this is a subtype that gets access to protected fields.
647 friend class CompactingPermGen;
648 friend class VM_PopulateDumpSharedSpace;
649
650 protected:
651 size_t _min_heap_delta_bytes; // Minimum amount to expand.
652 ContiguousSpace* _the_space; // actual space holding objects
653 WaterMark _last_gc; // watermark between objects allocated before
654 // and after last GC.
655
656 // Grow generation with specified size (returns false if unable to grow)
657 virtual bool grow_by(size_t bytes);
658 // Grow generation to reserved size.
659 virtual bool grow_to_reserved();
660 // Shrink generation with specified size (returns false if unable to shrink)
661 void shrink_by(size_t bytes);
662
663 // Allocation failure
664 virtual bool expand(size_t bytes, size_t expand_bytes);
665 void shrink(size_t bytes);
666
667 // Accessing spaces
668 ContiguousSpace* the_space() const { return _the_space; }
669
670 public:
671 OneContigSpaceCardGeneration(ReservedSpace rs, size_t initial_byte_size,
672 size_t min_heap_delta_bytes,
673 int level, GenRemSet* remset,
674 ContiguousSpace* space) :
675 CardGeneration(rs, initial_byte_size, level, remset),
676 _the_space(space), _min_heap_delta_bytes(min_heap_delta_bytes)
677 {}
678
679 inline bool is_in(const void* p) const;
680
681 // Space enquiries
682 size_t capacity() const;
683 size_t used() const;
684 size_t free() const;
685
686 MemRegion used_region() const;
687
688 size_t unsafe_max_alloc_nogc() const;
689 size_t contiguous_available() const;
690
691 // Iteration
692 void object_iterate(ObjectClosure* blk);
693 void space_iterate(SpaceClosure* blk, bool usedOnly = false);
694 void object_iterate_since_last_GC(ObjectClosure* cl);
695
696 void younger_refs_iterate(OopsInGenClosure* blk);
697
698 inline CompactibleSpace* first_compaction_space() const;
699
700 virtual inline HeapWord* allocate(size_t word_size, bool is_tlab);
701 virtual inline HeapWord* par_allocate(size_t word_size, bool is_tlab);
702
703 // Accessing marks
704 inline WaterMark top_mark();
705 inline WaterMark bottom_mark();
706
707 #define OneContig_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
708 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl);
709 OneContig_SINCE_SAVE_MARKS_DECL(OopsInGenClosure,_v)
710 SPECIALIZED_SINCE_SAVE_MARKS_CLOSURES(OneContig_SINCE_SAVE_MARKS_DECL)
711
712 void save_marks();
713 void reset_saved_marks();
714 bool no_allocs_since_save_marks();
715
716 inline size_t block_size(const HeapWord* addr) const;
717
718 inline bool block_is_obj(const HeapWord* addr) const;
719
720 virtual void collect(bool full,
721 bool clear_all_soft_refs,
722 size_t size,
723 bool is_tlab);
724 HeapWord* expand_and_allocate(size_t size,
725 bool is_tlab,
726 bool parallel = false);
727
728 virtual void prepare_for_verify();
729
730 virtual void gc_epilogue(bool full);
731
732 virtual void record_spaces_top();
733
734 virtual void verify(bool allow_dirty);
735 virtual void print_on(outputStream* st) const;
736 };