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_GENCOLLECTEDHEAP_HPP
26 #define SHARE_VM_MEMORY_GENCOLLECTEDHEAP_HPP
27
28 #include "gc_implementation/shared/adaptiveSizePolicy.hpp"
29 #include "memory/collectorPolicy.hpp"
30 #include "memory/generation.hpp"
31 #include "memory/sharedHeap.hpp"
32
33 class SubTasksDone;
34
35 // A "GenCollectedHeap" is a SharedHeap that uses generational
36 // collection. It is represented with a sequence of Generation's.
37 class GenCollectedHeap : public SharedHeap {
38 friend class GenCollectorPolicy;
39 friend class Generation;
40 friend class DefNewGeneration;
41 friend class TenuredGeneration;
42 friend class ConcurrentMarkSweepGeneration;
43 friend class CMSCollector;
44 friend class GenMarkSweep;
45 friend class VM_GenCollectForAllocation;
46 friend class VM_GenCollectFull;
47 friend class VM_GenCollectFullConcurrent;
48 friend class VM_GC_HeapInspection;
49 friend class VM_HeapDumper;
50 friend class HeapInspection;
51 friend class GCCauseSetter;
52 friend class VMStructs;
53 public:
54 enum SomeConstants {
55 max_gens = 10
56 };
57
58 friend class VM_PopulateDumpSharedSpace;
59
60 protected:
61 // Fields:
62 static GenCollectedHeap* _gch;
63
64 private:
65 int _n_gens;
66 Generation* _gens[max_gens];
67 GenerationSpec** _gen_specs;
68
69 // The generational collector policy.
70 GenCollectorPolicy* _gen_policy;
71
72 // Indicates that the most recent previous incremental collection failed.
73 // The flag is cleared when an action is taken that might clear the
74 // condition that caused that incremental collection to fail.
75 bool _incremental_collection_failed;
76
77 // In support of ExplicitGCInvokesConcurrent functionality
78 unsigned int _full_collections_completed;
79
80 // Data structure for claiming the (potentially) parallel tasks in
81 // (gen-specific) roots processing.
82 SubTasksDone* _gen_process_roots_tasks;
83 SubTasksDone* gen_process_roots_tasks() { return _gen_process_roots_tasks; }
84
85 // In block contents verification, the number of header words to skip
86 NOT_PRODUCT(static size_t _skip_header_HeapWords;)
87
88 protected:
89 // Helper functions for allocation
90 HeapWord* attempt_allocation(size_t size,
91 bool is_tlab,
92 bool first_only);
93
94 // Helper function for two callbacks below.
95 // Considers collection of the first max_level+1 generations.
96 void do_collection(bool full,
97 bool clear_all_soft_refs,
98 size_t size,
99 bool is_tlab,
100 int max_level);
101
102 // Callback from VM_GenCollectForAllocation operation.
103 // This function does everything necessary/possible to satisfy an
104 // allocation request that failed in the youngest generation that should
105 // have handled it (including collection, expansion, etc.)
106 HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab);
107
108 // Callback from VM_GenCollectFull operation.
109 // Perform a full collection of the first max_level+1 generations.
110 virtual void do_full_collection(bool clear_all_soft_refs);
111 void do_full_collection(bool clear_all_soft_refs, int max_level);
112
113 // Does the "cause" of GC indicate that
114 // we absolutely __must__ clear soft refs?
115 bool must_clear_all_soft_refs();
116
117 public:
118 GenCollectedHeap(GenCollectorPolicy *policy);
119
120 GCStats* gc_stats(int level) const;
121
122 // Returns JNI_OK on success
123 virtual jint initialize();
124 char* allocate(size_t alignment, size_t* _total_reserved, ReservedSpace* heap_rs);
125
126 // Does operations required after initialization has been done.
127 void post_initialize();
128
129 // Initialize ("weak") refs processing support
130 virtual void ref_processing_init();
131
132 virtual CollectedHeap::Name kind() const {
133 return CollectedHeap::GenCollectedHeap;
134 }
135
136 // The generational collector policy.
137 GenCollectorPolicy* gen_policy() const { return _gen_policy; }
138 virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) gen_policy(); }
139
140 // Adaptive size policy
141 virtual AdaptiveSizePolicy* size_policy() {
142 return gen_policy()->size_policy();
143 }
144
145 // Return the (conservative) maximum heap alignment
146 static size_t conservative_max_heap_alignment() {
147 return Generation::GenGrain;
148 }
149
150 size_t capacity() const;
151 size_t used() const;
152
153 // Save the "used_region" for generations level and lower.
154 void save_used_regions(int level);
155
156 size_t max_capacity() const;
157
158 HeapWord* mem_allocate(size_t size,
159 bool* gc_overhead_limit_was_exceeded);
160
161 // We may support a shared contiguous allocation area, if the youngest
162 // generation does.
163 bool supports_inline_contig_alloc() const;
164 HeapWord** top_addr() const;
165 HeapWord** end_addr() const;
166
167 // Does this heap support heap inspection? (+PrintClassHistogram)
168 virtual bool supports_heap_inspection() const { return true; }
169
170 // Perform a full collection of the heap; intended for use in implementing
171 // "System.gc". This implies as full a collection as the CollectedHeap
172 // supports. Caller does not hold the Heap_lock on entry.
173 void collect(GCCause::Cause cause);
174
175 // The same as above but assume that the caller holds the Heap_lock.
176 void collect_locked(GCCause::Cause cause);
177
178 // Perform a full collection of the first max_level+1 generations.
179 // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry.
180 void collect(GCCause::Cause cause, int max_level);
181
182 // Returns "TRUE" iff "p" points into the committed areas of the heap.
183 // The methods is_in(), is_in_closed_subset() and is_in_youngest() may
184 // be expensive to compute in general, so, to prevent
185 // their inadvertent use in product jvm's, we restrict their use to
186 // assertion checking or verification only.
187 bool is_in(const void* p) const;
188
189 // override
190 bool is_in_closed_subset(const void* p) const {
191 if (UseConcMarkSweepGC) {
192 return is_in_reserved(p);
193 } else {
194 return is_in(p);
195 }
196 }
197
198 // Returns true if the reference is to an object in the reserved space
199 // for the young generation.
200 // Assumes the the young gen address range is less than that of the old gen.
201 bool is_in_young(oop p);
202
203 #ifdef ASSERT
204 virtual bool is_in_partial_collection(const void* p);
205 #endif
206
207 virtual bool is_scavengable(const void* addr) {
208 return is_in_young((oop)addr);
209 }
210
211 // Iteration functions.
212 void oop_iterate(ExtendedOopClosure* cl);
213 void object_iterate(ObjectClosure* cl);
214 void safe_object_iterate(ObjectClosure* cl);
215 Space* space_containing(const void* addr) const;
216
217 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
218 // each address in the (reserved) heap is a member of exactly
219 // one block. The defining characteristic of a block is that it is
220 // possible to find its size, and thus to progress forward to the next
221 // block. (Blocks may be of different sizes.) Thus, blocks may
222 // represent Java objects, or they might be free blocks in a
223 // free-list-based heap (or subheap), as long as the two kinds are
224 // distinguishable and the size of each is determinable.
225
226 // Returns the address of the start of the "block" that contains the
227 // address "addr". We say "blocks" instead of "object" since some heaps
228 // may not pack objects densely; a chunk may either be an object or a
229 // non-object.
230 virtual HeapWord* block_start(const void* addr) const;
231
232 // Requires "addr" to be the start of a chunk, and returns its size.
233 // "addr + size" is required to be the start of a new chunk, or the end
234 // of the active area of the heap. Assumes (and verifies in non-product
235 // builds) that addr is in the allocated part of the heap and is
236 // the start of a chunk.
237 virtual size_t block_size(const HeapWord* addr) const;
238
239 // Requires "addr" to be the start of a block, and returns "TRUE" iff
240 // the block is an object. Assumes (and verifies in non-product
241 // builds) that addr is in the allocated part of the heap and is
242 // the start of a chunk.
243 virtual bool block_is_obj(const HeapWord* addr) const;
244
245 // Section on TLAB's.
246 virtual bool supports_tlab_allocation() const;
247 virtual size_t tlab_capacity(Thread* thr) const;
248 virtual size_t tlab_used(Thread* thr) const;
249 virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
250 virtual HeapWord* allocate_new_tlab(size_t size);
251
252 // Can a compiler initialize a new object without store barriers?
253 // This permission only extends from the creation of a new object
254 // via a TLAB up to the first subsequent safepoint.
255 virtual bool can_elide_tlab_store_barriers() const {
256 return true;
257 }
258
259 virtual bool card_mark_must_follow_store() const {
260 return UseConcMarkSweepGC;
261 }
262
263 // We don't need barriers for stores to objects in the
264 // young gen and, a fortiori, for initializing stores to
265 // objects therein. This applies to DefNew+Tenured and ParNew+CMS
266 // only and may need to be re-examined in case other
267 // kinds of collectors are implemented in the future.
268 virtual bool can_elide_initializing_store_barrier(oop new_obj) {
269 // We wanted to assert that:-
270 // assert(UseSerialGC || UseConcMarkSweepGC,
271 // "Check can_elide_initializing_store_barrier() for this collector");
272 // but unfortunately the flag UseSerialGC need not necessarily always
273 // be set when DefNew+Tenured are being used.
274 return is_in_young(new_obj);
275 }
276
277 // The "requestor" generation is performing some garbage collection
278 // action for which it would be useful to have scratch space. The
279 // requestor promises to allocate no more than "max_alloc_words" in any
280 // older generation (via promotion say.) Any blocks of space that can
281 // be provided are returned as a list of ScratchBlocks, sorted by
282 // decreasing size.
283 ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words);
284 // Allow each generation to reset any scratch space that it has
285 // contributed as it needs.
286 void release_scratch();
287
288 // Ensure parsability: override
289 virtual void ensure_parsability(bool retire_tlabs);
290
291 // Time in ms since the longest time a collector ran in
292 // in any generation.
293 virtual jlong millis_since_last_gc();
294
295 // Total number of full collections completed.
296 unsigned int total_full_collections_completed() {
297 assert(_full_collections_completed <= _total_full_collections,
298 "Can't complete more collections than were started");
299 return _full_collections_completed;
300 }
301
302 // Update above counter, as appropriate, at the end of a stop-world GC cycle
303 unsigned int update_full_collections_completed();
304 // Update above counter, as appropriate, at the end of a concurrent GC cycle
305 unsigned int update_full_collections_completed(unsigned int count);
306
307 // Update "time of last gc" for all constituent generations
308 // to "now".
309 void update_time_of_last_gc(jlong now) {
310 for (int i = 0; i < _n_gens; i++) {
311 _gens[i]->update_time_of_last_gc(now);
312 }
313 }
314
315 // Update the gc statistics for each generation.
316 // "level" is the level of the latest collection.
317 void update_gc_stats(int current_level, bool full) {
318 for (int i = 0; i < _n_gens; i++) {
319 _gens[i]->update_gc_stats(current_level, full);
320 }
321 }
322
323 // Override.
324 bool no_gc_in_progress() { return !is_gc_active(); }
325
326 // Override.
327 void prepare_for_verify();
328
329 // Override.
330 void verify(bool silent, VerifyOption option);
331
332 // Override.
333 virtual void print_on(outputStream* st) const;
334 virtual void print_gc_threads_on(outputStream* st) const;
335 virtual void gc_threads_do(ThreadClosure* tc) const;
336 virtual void print_tracing_info() const;
337 virtual void print_on_error(outputStream* st) const;
338
339 // PrintGC, PrintGCDetails support
340 void print_heap_change(size_t prev_used) const;
341
342 // The functions below are helper functions that a subclass of
343 // "CollectedHeap" can use in the implementation of its virtual
344 // functions.
345
346 class GenClosure : public StackObj {
347 public:
348 virtual void do_generation(Generation* gen) = 0;
349 };
350
351 // Apply "cl.do_generation" to all generations in the heap
352 // If "old_to_young" determines the order.
353 void generation_iterate(GenClosure* cl, bool old_to_young);
354
355 void space_iterate(SpaceClosure* cl);
356
357 // Return "true" if all generations have reached the
358 // maximal committed limit that they can reach, without a garbage
359 // collection.
360 virtual bool is_maximal_no_gc() const;
361
362 // Return the generation before "gen".
363 Generation* prev_gen(Generation* gen) const {
364 int l = gen->level();
365 guarantee(l > 0, "Out of bounds");
366 return _gens[l-1];
367 }
368
369 // Return the generation after "gen".
370 Generation* next_gen(Generation* gen) const {
371 int l = gen->level() + 1;
372 guarantee(l < _n_gens, "Out of bounds");
373 return _gens[l];
374 }
375
376 Generation* get_gen(int i) const {
377 guarantee(i >= 0 && i < _n_gens, "Out of bounds");
378 return _gens[i];
379 }
380
381 int n_gens() const {
382 assert(_n_gens == gen_policy()->number_of_generations(), "Sanity");
383 return _n_gens;
384 }
385
386 // Convenience function to be used in situations where the heap type can be
387 // asserted to be this type.
388 static GenCollectedHeap* heap();
389
390 void set_par_threads(uint t);
391
392 // Invoke the "do_oop" method of one of the closures "not_older_gens"
393 // or "older_gens" on root locations for the generation at
394 // "level". (The "older_gens" closure is used for scanning references
395 // from older generations; "not_older_gens" is used everywhere else.)
396 // If "younger_gens_as_roots" is false, younger generations are
397 // not scanned as roots; in this case, the caller must be arranging to
398 // scan the younger generations itself. (For example, a generation might
399 // explicitly mark reachable objects in younger generations, to avoid
400 // excess storage retention.)
401 // The "so" argument determines which of the roots
402 // the closure is applied to:
403 // "SO_None" does none;
404 private:
405 void gen_process_roots(int level,
406 bool younger_gens_as_roots,
407 bool activate_scope,
408 SharedHeap::ScanningOption so,
409 OopsInGenClosure* not_older_gens,
410 OopsInGenClosure* weak_roots,
411 OopsInGenClosure* older_gens,
412 CLDClosure* cld_closure,
413 CLDClosure* weak_cld_closure,
414 CodeBlobClosure* code_closure);
415
416 public:
417 static const bool StrongAndWeakRoots = false;
418 static const bool StrongRootsOnly = true;
419
420 void gen_process_roots(int level,
421 bool younger_gens_as_roots,
422 bool activate_scope,
423 SharedHeap::ScanningOption so,
424 bool only_strong_roots,
425 OopsInGenClosure* not_older_gens,
426 OopsInGenClosure* older_gens,
427 CLDClosure* cld_closure);
428
429 // Apply "root_closure" to all the weak roots of the system.
430 // These include JNI weak roots, string table,
431 // and referents of reachable weak refs.
432 void gen_process_weak_roots(OopClosure* root_closure);
433
434 // Set the saved marks of generations, if that makes sense.
435 // In particular, if any generation might iterate over the oops
436 // in other generations, it should call this method.
437 void save_marks();
438
439 // Apply "cur->do_oop" or "older->do_oop" to all the oops in objects
440 // allocated since the last call to save_marks in generations at or above
441 // "level". The "cur" closure is
442 // applied to references in the generation at "level", and the "older"
443 // closure to older generations.
444 #define GCH_SINCE_SAVE_MARKS_ITERATE_DECL(OopClosureType, nv_suffix) \
445 void oop_since_save_marks_iterate(int level, \
446 OopClosureType* cur, \
447 OopClosureType* older);
448
449 ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DECL)
450
451 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DECL
452
453 // Returns "true" iff no allocations have occurred in any generation at
454 // "level" or above since the last
455 // call to "save_marks".
456 bool no_allocs_since_save_marks(int level);
457
458 // Returns true if an incremental collection is likely to fail.
459 // We optionally consult the young gen, if asked to do so;
460 // otherwise we base our answer on whether the previous incremental
461 // collection attempt failed with no corrective action as of yet.
462 bool incremental_collection_will_fail(bool consult_young) {
463 // Assumes a 2-generation system; the first disjunct remembers if an
464 // incremental collection failed, even when we thought (second disjunct)
465 // that it would not.
466 assert(heap()->collector_policy()->is_generation_policy(),
467 "the following definition may not be suitable for an n(>2)-generation system");
468 return incremental_collection_failed() ||
469 (consult_young && !get_gen(0)->collection_attempt_is_safe());
470 }
471
472 // If a generation bails out of an incremental collection,
473 // it sets this flag.
474 bool incremental_collection_failed() const {
475 return _incremental_collection_failed;
476 }
477 void set_incremental_collection_failed() {
478 _incremental_collection_failed = true;
479 }
480 void clear_incremental_collection_failed() {
481 _incremental_collection_failed = false;
482 }
483
484 // Promotion of obj into gen failed. Try to promote obj to higher
485 // gens in ascending order; return the new location of obj if successful.
486 // Otherwise, try expand-and-allocate for obj in both the young and old
487 // generation; return the new location of obj if successful. Otherwise, return NULL.
488 oop handle_failed_promotion(Generation* old_gen,
489 oop obj,
490 size_t obj_size);
491
492 private:
493 // Accessor for memory state verification support
494 NOT_PRODUCT(
495 static size_t skip_header_HeapWords() { return _skip_header_HeapWords; }
496 )
497
498 // Override
499 void check_for_non_bad_heap_word_value(HeapWord* addr,
500 size_t size) PRODUCT_RETURN;
501
502 // For use by mark-sweep. As implemented, mark-sweep-compact is global
503 // in an essential way: compaction is performed across generations, by
504 // iterating over spaces.
505 void prepare_for_compaction();
506
507 // Perform a full collection of the first max_level+1 generations.
508 // This is the low level interface used by the public versions of
509 // collect() and collect_locked(). Caller holds the Heap_lock on entry.
510 void collect_locked(GCCause::Cause cause, int max_level);
511
512 // Returns success or failure.
513 bool create_cms_collector();
514
515 // In support of ExplicitGCInvokesConcurrent functionality
516 bool should_do_concurrent_full_gc(GCCause::Cause cause);
517 void collect_mostly_concurrent(GCCause::Cause cause);
518
519 // Save the tops of the spaces in all generations
520 void record_gen_tops_before_GC() PRODUCT_RETURN;
521
522 protected:
523 virtual void gc_prologue(bool full);
524 virtual void gc_epilogue(bool full);
525 };
526
527 #endif // SHARE_VM_MEMORY_GENCOLLECTEDHEAP_HPP