Mon, 23 Mar 2020 17:57:13 +0000
8231779: crash HeapWord*ParallelScavengeHeap::failed_mem_allocate
Reviewed-by: dlong, tschatzl, pliden
1 /*
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25 #ifndef SHARE_VM_MEMORY_GENERATION_HPP
26 #define SHARE_VM_MEMORY_GENERATION_HPP
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"
38 // A Generation models a heap area for similarly-aged objects.
39 // It will contain one ore more spaces holding the actual objects.
40 //
41 // The Generation class hierarchy:
42 //
43 // Generation - abstract base class
44 // - DefNewGeneration - allocation area (copy collected)
45 // - ParNewGeneration - a DefNewGeneration that is collected by
46 // several threads
47 // - CardGeneration - abstract class adding offset array behavior
48 // - OneContigSpaceCardGeneration - abstract class holding a single
49 // contiguous space with card marking
50 // - TenuredGeneration - tenured (old object) space (markSweepCompact)
51 // - ConcurrentMarkSweepGeneration - Mostly Concurrent Mark Sweep Generation
52 // (Detlefs-Printezis refinement of
53 // Boehm-Demers-Schenker)
54 //
55 // The system configurations currently allowed are:
56 //
57 // DefNewGeneration + TenuredGeneration
58 // DefNewGeneration + ConcurrentMarkSweepGeneration
59 //
60 // ParNewGeneration + TenuredGeneration
61 // ParNewGeneration + ConcurrentMarkSweepGeneration
62 //
64 class DefNewGeneration;
65 class GenerationSpec;
66 class CompactibleSpace;
67 class ContiguousSpace;
68 class CompactPoint;
69 class OopsInGenClosure;
70 class OopClosure;
71 class ScanClosure;
72 class FastScanClosure;
73 class GenCollectedHeap;
74 class GenRemSet;
75 class GCStats;
77 // A "ScratchBlock" represents a block of memory in one generation usable by
78 // another. It represents "num_words" free words, starting at and including
79 // the address of "this".
80 struct ScratchBlock {
81 ScratchBlock* next;
82 size_t num_words;
83 HeapWord scratch_space[1]; // Actually, of size "num_words-2" (assuming
84 // first two fields are word-sized.)
85 };
88 class Generation: public CHeapObj<mtGC> {
89 friend class VMStructs;
90 private:
91 jlong _time_of_last_gc; // time when last gc on this generation happened (ms)
92 MemRegion _prev_used_region; // for collectors that want to "remember" a value for
93 // used region at some specific point during collection.
95 protected:
96 // Minimum and maximum addresses for memory reserved (not necessarily
97 // committed) for generation.
98 // Used by card marking code. Must not overlap with address ranges of
99 // other generations.
100 MemRegion _reserved;
102 // Memory area reserved for generation
103 VirtualSpace _virtual_space;
105 // Level in the generation hierarchy.
106 int _level;
108 // ("Weak") Reference processing support
109 ReferenceProcessor* _ref_processor;
111 // Performance Counters
112 CollectorCounters* _gc_counters;
114 // Statistics for garbage collection
115 GCStats* _gc_stats;
117 // Returns the next generation in the configuration, or else NULL if this
118 // is the highest generation.
119 Generation* next_gen() const;
121 // Initialize the generation.
122 Generation(ReservedSpace rs, size_t initial_byte_size, int level);
124 // Apply "cl->do_oop" to (the address of) (exactly) all the ref fields in
125 // "sp" that point into younger generations.
126 // The iteration is only over objects allocated at the start of the
127 // iterations; objects allocated as a result of applying the closure are
128 // not included.
129 void younger_refs_in_space_iterate(Space* sp, OopsInGenClosure* cl);
131 public:
132 // The set of possible generation kinds.
133 enum Name {
134 ASParNew,
135 ASConcurrentMarkSweep,
136 DefNew,
137 ParNew,
138 MarkSweepCompact,
139 ConcurrentMarkSweep,
140 Other
141 };
143 enum SomePublicConstants {
144 // Generations are GenGrain-aligned and have size that are multiples of
145 // GenGrain.
146 // Note: on ARM we add 1 bit for card_table_base to be properly aligned
147 // (we expect its low byte to be zero - see implementation of post_barrier)
148 LogOfGenGrain = 16 ARM32_ONLY(+1),
149 GenGrain = 1 << LogOfGenGrain
150 };
152 // allocate and initialize ("weak") refs processing support
153 virtual void ref_processor_init();
154 void set_ref_processor(ReferenceProcessor* rp) {
155 assert(_ref_processor == NULL, "clobbering existing _ref_processor");
156 _ref_processor = rp;
157 }
159 virtual Generation::Name kind() { return Generation::Other; }
160 GenerationSpec* spec();
162 // This properly belongs in the collector, but for now this
163 // will do.
164 virtual bool refs_discovery_is_atomic() const { return true; }
165 virtual bool refs_discovery_is_mt() const { return false; }
167 // Space enquiries (results in bytes)
168 virtual size_t capacity() const = 0; // The maximum number of object bytes the
169 // generation can currently hold.
170 virtual size_t used() const = 0; // The number of used bytes in the gen.
171 virtual size_t used_stable() const; // The number of used bytes for memory monitoring tools.
172 virtual size_t free() const = 0; // The number of free bytes in the gen.
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;
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; }
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;
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;
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 */ }
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;
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 }
214 MemRegion reserved() const { return _reserved; }
216 // Returns a region guaranteed to contain all the objects in the
217 // generation.
218 virtual MemRegion used_region() const { return _reserved; }
220 MemRegion prev_used_region() const { return _prev_used_region; }
221 virtual void save_used_region() { _prev_used_region = used_region(); }
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;
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 }
235 // Check that the generation kind is DefNewGeneration or a sub
236 // class of DefNewGeneration and return a DefNewGeneration*
237 DefNewGeneration* as_DefNewGeneration();
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;
243 // Iteration - do not use for time critical operations
244 virtual void space_iterate(SpaceClosure* blk, bool usedOnly = false) = 0;
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;
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 }
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;
268 // Like "allocate", but performs any necessary locking internally.
269 virtual HeapWord* par_allocate(size_t word_size, bool is_tlab) = 0;
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 }
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.)
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; }
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; }
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 tlab_used() 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 }
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);
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);
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);
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) {}
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) {}
347 // This generation will collect all younger generations
348 // during a full collection.
349 virtual bool full_collects_younger_generations() const { return false; }
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; }
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 }
374 // Returns true if the collection is likely to be safely
375 // completed. Even if this method returns true, a collection
376 // may not be guaranteed to succeed, and the system should be
377 // able to safely unwind and recover from that failure, albeit
378 // at some additional cost.
379 virtual bool collection_attempt_is_safe() {
380 guarantee(false, "Are you sure you want to call this method?");
381 return true;
382 }
384 // Perform a garbage collection.
385 // If full is true attempt a full garbage collection of this generation.
386 // Otherwise, attempting to (at least) free enough space to support an
387 // allocation of the given "word_size".
388 virtual void collect(bool full,
389 bool clear_all_soft_refs,
390 size_t word_size,
391 bool is_tlab) = 0;
393 // Perform a heap collection, attempting to create (at least) enough
394 // space to support an allocation of the given "word_size". If
395 // successful, perform the allocation and return the resulting
396 // "oop" (initializing the allocated block). If the allocation is
397 // still unsuccessful, return "NULL".
398 virtual HeapWord* expand_and_allocate(size_t word_size,
399 bool is_tlab,
400 bool parallel = false) = 0;
402 // Some generations may require some cleanup or preparation actions before
403 // allowing a collection. The default is to do nothing.
404 virtual void gc_prologue(bool full) {};
406 // Some generations may require some cleanup actions after a collection.
407 // The default is to do nothing.
408 virtual void gc_epilogue(bool full) {};
410 // Save the high water marks for the used space in a generation.
411 virtual void record_spaces_top() {};
413 // Some generations may need to be "fixed-up" after some allocation
414 // activity to make them parsable again. The default is to do nothing.
415 virtual void ensure_parsability() {};
417 // Time (in ms) when we were last collected or now if a collection is
418 // in progress.
419 virtual jlong time_of_last_gc(jlong now) {
420 // Both _time_of_last_gc and now are set using a time source
421 // that guarantees monotonically non-decreasing values provided
422 // the underlying platform provides such a source. So we still
423 // have to guard against non-monotonicity.
424 NOT_PRODUCT(
425 if (now < _time_of_last_gc) {
426 warning("time warp: "INT64_FORMAT" to "INT64_FORMAT, (int64_t)_time_of_last_gc, (int64_t)now);
427 }
428 )
429 return _time_of_last_gc;
430 }
432 virtual void update_time_of_last_gc(jlong now) {
433 _time_of_last_gc = now;
434 }
436 // Generations may keep statistics about collection. This
437 // method updates those statistics. current_level is
438 // the level of the collection that has most recently
439 // occurred. This allows the generation to decide what
440 // statistics are valid to collect. For example, the
441 // generation can decide to gather the amount of promoted data
442 // if the collection of the younger generations has completed.
443 GCStats* gc_stats() const { return _gc_stats; }
444 virtual void update_gc_stats(int current_level, bool full) {}
446 // Mark sweep support phase2
447 virtual void prepare_for_compaction(CompactPoint* cp);
448 // Mark sweep support phase3
449 virtual void adjust_pointers();
450 // Mark sweep support phase4
451 virtual void compact();
452 virtual void post_compact() {ShouldNotReachHere();}
454 // Support for CMS's rescan. In this general form we return a pointer
455 // to an abstract object that can be used, based on specific previously
456 // decided protocols, to exchange information between generations,
457 // information that may be useful for speeding up certain types of
458 // garbage collectors. A NULL value indicates to the client that
459 // no data recording is expected by the provider. The data-recorder is
460 // expected to be GC worker thread-local, with the worker index
461 // indicated by "thr_num".
462 virtual void* get_data_recorder(int thr_num) { return NULL; }
463 virtual void sample_eden_chunk() {}
465 // Some generations may require some cleanup actions before allowing
466 // a verification.
467 virtual void prepare_for_verify() {};
469 // Accessing "marks".
471 // This function gives a generation a chance to note a point between
472 // collections. For example, a contiguous generation might note the
473 // beginning allocation point post-collection, which might allow some later
474 // operations to be optimized.
475 virtual void save_marks() {}
477 // This function allows generations to initialize any "saved marks". That
478 // is, should only be called when the generation is empty.
479 virtual void reset_saved_marks() {}
481 // This function is "true" iff any no allocations have occurred in the
482 // generation since the last call to "save_marks".
483 virtual bool no_allocs_since_save_marks() = 0;
485 // Apply "cl->apply" to (the addresses of) all reference fields in objects
486 // allocated in the current generation since the last call to "save_marks".
487 // If more objects are allocated in this generation as a result of applying
488 // the closure, iterates over reference fields in those objects as well.
489 // Calls "save_marks" at the end of the iteration.
490 // General signature...
491 virtual void oop_since_save_marks_iterate_v(OopsInGenClosure* cl) = 0;
492 // ...and specializations for de-virtualization. (The general
493 // implemention of the _nv versions call the virtual version.
494 // Note that the _nv suffix is not really semantically necessary,
495 // but it avoids some not-so-useful warnings on Solaris.)
496 #define Generation_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
497 virtual void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \
498 oop_since_save_marks_iterate_v((OopsInGenClosure*)cl); \
499 }
500 SPECIALIZED_SINCE_SAVE_MARKS_CLOSURES(Generation_SINCE_SAVE_MARKS_DECL)
502 #undef Generation_SINCE_SAVE_MARKS_DECL
504 // The "requestor" generation is performing some garbage collection
505 // action for which it would be useful to have scratch space. If
506 // the target is not the requestor, no gc actions will be required
507 // of the target. The requestor promises to allocate no more than
508 // "max_alloc_words" in the target generation (via promotion say,
509 // if the requestor is a young generation and the target is older).
510 // If the target generation can provide any scratch space, it adds
511 // it to "list", leaving "list" pointing to the head of the
512 // augmented list. The default is to offer no space.
513 virtual void contribute_scratch(ScratchBlock*& list, Generation* requestor,
514 size_t max_alloc_words) {}
516 // Give each generation an opportunity to do clean up for any
517 // contributed scratch.
518 virtual void reset_scratch() {};
520 // When an older generation has been collected, and perhaps resized,
521 // this method will be invoked on all younger generations (from older to
522 // younger), allowing them to resize themselves as appropriate.
523 virtual void compute_new_size() = 0;
525 // Printing
526 virtual const char* name() const = 0;
527 virtual const char* short_name() const = 0;
529 int level() const { return _level; }
531 // Attributes
533 // True iff the given generation may only be the youngest generation.
534 virtual bool must_be_youngest() const = 0;
535 // True iff the given generation may only be the oldest generation.
536 virtual bool must_be_oldest() const = 0;
538 // Reference Processing accessor
539 ReferenceProcessor* const ref_processor() { return _ref_processor; }
541 // Iteration.
543 // Iterate over all the ref-containing fields of all objects in the
544 // generation, calling "cl.do_oop" on each.
545 virtual void oop_iterate(ExtendedOopClosure* cl);
547 // Iterate over all objects in the generation, calling "cl.do_object" on
548 // each.
549 virtual void object_iterate(ObjectClosure* cl);
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);
556 // Apply "cl->do_oop" to (the address of) all and only all the ref fields
557 // in the current generation that contain pointers to objects in younger
558 // generations. Objects allocated since the last "save_marks" call are
559 // excluded.
560 virtual void younger_refs_iterate(OopsInGenClosure* cl) = 0;
562 // Inform a generation that it longer contains references to objects
563 // in any younger generation. [e.g. Because younger gens are empty,
564 // clear the card table.]
565 virtual void clear_remembered_set() { }
567 // Inform a generation that some of its objects have moved. [e.g. The
568 // generation's spaces were compacted, invalidating the card table.]
569 virtual void invalidate_remembered_set() { }
571 // Block abstraction.
573 // Returns the address of the start of the "block" that contains the
574 // address "addr". We say "blocks" instead of "object" since some heaps
575 // may not pack objects densely; a chunk may either be an object or a
576 // non-object.
577 virtual HeapWord* block_start(const void* addr) const;
579 // Requires "addr" to be the start of a chunk, and returns its size.
580 // "addr + size" is required to be the start of a new chunk, or the end
581 // of the active area of the heap.
582 virtual size_t block_size(const HeapWord* addr) const ;
584 // Requires "addr" to be the start of a block, and returns "TRUE" iff
585 // the block is an object.
586 virtual bool block_is_obj(const HeapWord* addr) const;
589 // PrintGC, PrintGCDetails support
590 void print_heap_change(size_t prev_used) const;
592 // PrintHeapAtGC support
593 virtual void print() const;
594 virtual void print_on(outputStream* st) const;
596 virtual void verify() = 0;
598 struct StatRecord {
599 int invocations;
600 elapsedTimer accumulated_time;
601 StatRecord() :
602 invocations(0),
603 accumulated_time(elapsedTimer()) {}
604 };
605 private:
606 StatRecord _stat_record;
607 public:
608 StatRecord* stat_record() { return &_stat_record; }
610 virtual void print_summary_info();
611 virtual void print_summary_info_on(outputStream* st);
613 // Performance Counter support
614 virtual void update_counters() = 0;
615 virtual CollectorCounters* counters() { return _gc_counters; }
616 };
618 // Class CardGeneration is a generation that is covered by a card table,
619 // and uses a card-size block-offset array to implement block_start.
621 // class BlockOffsetArray;
622 // class BlockOffsetArrayContigSpace;
623 class BlockOffsetSharedArray;
625 class CardGeneration: public Generation {
626 friend class VMStructs;
627 protected:
628 // This is shared with other generations.
629 GenRemSet* _rs;
630 // This is local to this generation.
631 BlockOffsetSharedArray* _bts;
633 // current shrinking effect: this damps shrinking when the heap gets empty.
634 size_t _shrink_factor;
636 size_t _min_heap_delta_bytes; // Minimum amount to expand.
638 // Some statistics from before gc started.
639 // These are gathered in the gc_prologue (and should_collect)
640 // to control growing/shrinking policy in spite of promotions.
641 size_t _capacity_at_prologue;
642 size_t _used_at_prologue;
644 CardGeneration(ReservedSpace rs, size_t initial_byte_size, int level,
645 GenRemSet* remset);
647 public:
649 // Attempt to expand the generation by "bytes". Expand by at a
650 // minimum "expand_bytes". Return true if some amount (not
651 // necessarily the full "bytes") was done.
652 virtual bool expand(size_t bytes, size_t expand_bytes);
654 // Shrink generation with specified size (returns false if unable to shrink)
655 virtual void shrink(size_t bytes) = 0;
657 virtual void compute_new_size();
659 virtual void clear_remembered_set();
661 virtual void invalidate_remembered_set();
663 virtual void prepare_for_verify();
665 // Grow generation with specified size (returns false if unable to grow)
666 virtual bool grow_by(size_t bytes) = 0;
667 // Grow generation to reserved size.
668 virtual bool grow_to_reserved() = 0;
669 };
671 // OneContigSpaceCardGeneration models a heap of old objects contained in a single
672 // contiguous space.
673 //
674 // Garbage collection is performed using mark-compact.
676 class OneContigSpaceCardGeneration: public CardGeneration {
677 friend class VMStructs;
678 // Abstractly, this is a subtype that gets access to protected fields.
679 friend class VM_PopulateDumpSharedSpace;
681 protected:
682 ContiguousSpace* _the_space; // actual space holding objects
683 WaterMark _last_gc; // watermark between objects allocated before
684 // and after last GC.
686 // Grow generation with specified size (returns false if unable to grow)
687 virtual bool grow_by(size_t bytes);
688 // Grow generation to reserved size.
689 virtual bool grow_to_reserved();
690 // Shrink generation with specified size (returns false if unable to shrink)
691 void shrink_by(size_t bytes);
693 // Allocation failure
694 virtual bool expand(size_t bytes, size_t expand_bytes);
695 void shrink(size_t bytes);
697 // Accessing spaces
698 ContiguousSpace* the_space() const { return _the_space; }
700 public:
701 OneContigSpaceCardGeneration(ReservedSpace rs, size_t initial_byte_size,
702 int level, GenRemSet* remset,
703 ContiguousSpace* space) :
704 CardGeneration(rs, initial_byte_size, level, remset),
705 _the_space(space)
706 {}
708 inline bool is_in(const void* p) const;
710 // Space enquiries
711 size_t capacity() const;
712 size_t used() const;
713 size_t free() const;
715 MemRegion used_region() const;
717 size_t unsafe_max_alloc_nogc() const;
718 size_t contiguous_available() const;
720 // Iteration
721 void object_iterate(ObjectClosure* blk);
722 void space_iterate(SpaceClosure* blk, bool usedOnly = false);
724 void younger_refs_iterate(OopsInGenClosure* blk);
726 inline CompactibleSpace* first_compaction_space() const;
728 virtual inline HeapWord* allocate(size_t word_size, bool is_tlab);
729 virtual inline HeapWord* par_allocate(size_t word_size, bool is_tlab);
731 // Accessing marks
732 inline WaterMark top_mark();
733 inline WaterMark bottom_mark();
735 #define OneContig_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
736 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl);
737 OneContig_SINCE_SAVE_MARKS_DECL(OopsInGenClosure,_v)
738 SPECIALIZED_SINCE_SAVE_MARKS_CLOSURES(OneContig_SINCE_SAVE_MARKS_DECL)
740 void save_marks();
741 void reset_saved_marks();
742 bool no_allocs_since_save_marks();
744 inline size_t block_size(const HeapWord* addr) const;
746 inline bool block_is_obj(const HeapWord* addr) const;
748 virtual void collect(bool full,
749 bool clear_all_soft_refs,
750 size_t size,
751 bool is_tlab);
752 HeapWord* expand_and_allocate(size_t size,
753 bool is_tlab,
754 bool parallel = false);
756 virtual void prepare_for_verify();
758 virtual void gc_epilogue(bool full);
760 virtual void record_spaces_top();
762 virtual void verify();
763 virtual void print_on(outputStream* st) const;
764 };
766 #endif // SHARE_VM_MEMORY_GENERATION_HPP