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 has two generations, young and old.
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 friend class VM_PopulateDumpSharedSpace;
55
56 protected:
57 // Fields:
58 static GenCollectedHeap* _gch;
59
60 private:
61 Generation* _young_gen;
62 Generation* _old_gen;
63
64 // The singleton Gen Remembered Set.
65 GenRemSet* _rem_set;
66
67 // The generational collector policy.
68 GenCollectorPolicy* _gen_policy;
69
70 // Indicates that the most recent previous incremental collection failed.
71 // The flag is cleared when an action is taken that might clear the
72 // condition that caused that incremental collection to fail.
73 bool _incremental_collection_failed;
74
75 // In support of ExplicitGCInvokesConcurrent functionality
76 unsigned int _full_collections_completed;
77
78 // Data structure for claiming the (potentially) parallel tasks in
79 // (gen-specific) roots processing.
80 SubTasksDone* _process_strong_tasks;
81
82 // Collects the given generation.
83 void collect_generation(Generation* gen, bool full, size_t size, bool is_tlab,
84 bool run_verification, bool clear_soft_refs,
85 bool restore_marks_for_biased_locking);
86
87 // In block contents verification, the number of header words to skip
88 NOT_PRODUCT(static size_t _skip_header_HeapWords;)
89
90 protected:
91 // Helper functions for allocation
92 HeapWord* attempt_allocation(size_t size,
93 bool is_tlab,
94 bool first_only);
95
96 // Helper function for two callbacks below.
97 // Considers collection of the first max_level+1 generations.
98 void do_collection(bool full,
99 bool clear_all_soft_refs,
100 size_t size,
101 bool is_tlab,
102 int max_level);
103
104 // Callback from VM_GenCollectForAllocation operation.
105 // This function does everything necessary/possible to satisfy an
106 // allocation request that failed in the youngest generation that should
107 // have handled it (including collection, expansion, etc.)
108 HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab);
109
110 // Callback from VM_GenCollectFull operation.
111 // Perform a full collection of the first max_level+1 generations.
112 virtual void do_full_collection(bool clear_all_soft_refs);
113 void do_full_collection(bool clear_all_soft_refs, int max_level);
114
115 // Does the "cause" of GC indicate that
116 // we absolutely __must__ clear soft refs?
117 bool must_clear_all_soft_refs();
118
119 public:
120 GenCollectedHeap(GenCollectorPolicy *policy);
121
122 GCStats* gc_stats(int level) const;
123
124 // Returns JNI_OK on success
125 virtual jint initialize();
126
127 // Reserve aligned space for the heap as needed by the contained generations.
128 char* allocate(size_t alignment, ReservedSpace* heap_rs);
129
130 // Does operations required after initialization has been done.
131 void post_initialize();
132
133 // Initialize ("weak") refs processing support
134 virtual void ref_processing_init();
135
136 virtual CollectedHeap::Name kind() const {
137 return CollectedHeap::GenCollectedHeap;
138 }
139
140 Generation* young_gen() const { return _young_gen; }
141 Generation* old_gen() const { return _old_gen; }
142
143 // The generational collector policy.
144 GenCollectorPolicy* gen_policy() const { return _gen_policy; }
145
146 virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) gen_policy(); }
147
148 // Adaptive size policy
149 virtual AdaptiveSizePolicy* size_policy() {
150 return gen_policy()->size_policy();
151 }
152
153 // Return the (conservative) maximum heap alignment
154 static size_t conservative_max_heap_alignment() {
155 return Generation::GenGrain;
156 }
157
158 size_t capacity() const;
159 size_t used() const;
160
161 // Save the "used_region" for generations level and lower.
162 void save_used_regions(int level);
163
164 size_t max_capacity() const;
165
166 HeapWord* mem_allocate(size_t size,
167 bool* gc_overhead_limit_was_exceeded);
168
169 // We may support a shared contiguous allocation area, if the youngest
170 // generation does.
171 bool supports_inline_contig_alloc() const;
172 HeapWord** top_addr() const;
173 HeapWord** end_addr() const;
174
175 // Does this heap support heap inspection? (+PrintClassHistogram)
176 virtual bool supports_heap_inspection() const { return true; }
177
178 // Perform a full collection of the heap; intended for use in implementing
179 // "System.gc". This implies as full a collection as the CollectedHeap
180 // supports. Caller does not hold the Heap_lock on entry.
181 void collect(GCCause::Cause cause);
182
183 // The same as above but assume that the caller holds the Heap_lock.
184 void collect_locked(GCCause::Cause cause);
185
186 // Perform a full collection of the first max_level+1 generations.
187 // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry.
188 void collect(GCCause::Cause cause, int max_level);
189
190 // Returns "TRUE" iff "p" points into the committed areas of the heap.
191 // The methods is_in(), is_in_closed_subset() and is_in_youngest() may
192 // be expensive to compute in general, so, to prevent
193 // their inadvertent use in product jvm's, we restrict their use to
194 // assertion checking or verification only.
195 bool is_in(const void* p) const;
196
197 // override
198 bool is_in_closed_subset(const void* p) const {
199 if (UseConcMarkSweepGC) {
200 return is_in_reserved(p);
201 } else {
202 return is_in(p);
203 }
204 }
205
206 // Returns true if the reference is to an object in the reserved space
207 // for the young generation.
208 // Assumes the the young gen address range is less than that of the old gen.
209 bool is_in_young(oop p);
210
211 #ifdef ASSERT
212 virtual bool is_in_partial_collection(const void* p);
213 #endif
214
215 virtual bool is_scavengable(const void* addr) {
216 return is_in_young((oop)addr);
217 }
218
219 // Iteration functions.
220 void oop_iterate(ExtendedOopClosure* cl);
221 void object_iterate(ObjectClosure* cl);
222 void safe_object_iterate(ObjectClosure* cl);
223 Space* space_containing(const void* addr) const;
224
225 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
226 // each address in the (reserved) heap is a member of exactly
227 // one block. The defining characteristic of a block is that it is
228 // possible to find its size, and thus to progress forward to the next
229 // block. (Blocks may be of different sizes.) Thus, blocks may
230 // represent Java objects, or they might be free blocks in a
231 // free-list-based heap (or subheap), as long as the two kinds are
232 // distinguishable and the size of each is determinable.
233
234 // Returns the address of the start of the "block" that contains the
235 // address "addr". We say "blocks" instead of "object" since some heaps
236 // may not pack objects densely; a chunk may either be an object or a
237 // non-object.
238 virtual HeapWord* block_start(const void* addr) const;
239
240 // Requires "addr" to be the start of a chunk, and returns its size.
241 // "addr + size" is required to be the start of a new chunk, or the end
242 // of the active area of the heap. Assumes (and verifies in non-product
243 // builds) that addr is in the allocated part of the heap and is
244 // the start of a chunk.
245 virtual size_t block_size(const HeapWord* addr) const;
246
247 // Requires "addr" to be the start of a block, and returns "TRUE" iff
248 // the block is an object. Assumes (and verifies in non-product
249 // builds) that addr is in the allocated part of the heap and is
250 // the start of a chunk.
251 virtual bool block_is_obj(const HeapWord* addr) const;
252
253 // Section on TLAB's.
254 virtual bool supports_tlab_allocation() const;
255 virtual size_t tlab_capacity(Thread* thr) const;
256 virtual size_t tlab_used(Thread* thr) const;
257 virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
258 virtual HeapWord* allocate_new_tlab(size_t size);
259
260 // Can a compiler initialize a new object without store barriers?
261 // This permission only extends from the creation of a new object
262 // via a TLAB up to the first subsequent safepoint.
263 virtual bool can_elide_tlab_store_barriers() const {
264 return true;
265 }
266
267 virtual bool card_mark_must_follow_store() const {
268 return UseConcMarkSweepGC;
269 }
270
271 // We don't need barriers for stores to objects in the
272 // young gen and, a fortiori, for initializing stores to
273 // objects therein. This applies to DefNew+Tenured and ParNew+CMS
274 // only and may need to be re-examined in case other
275 // kinds of collectors are implemented in the future.
276 virtual bool can_elide_initializing_store_barrier(oop new_obj) {
277 // We wanted to assert that:-
278 // assert(UseSerialGC || UseConcMarkSweepGC,
279 // "Check can_elide_initializing_store_barrier() for this collector");
280 // but unfortunately the flag UseSerialGC need not necessarily always
281 // be set when DefNew+Tenured are being used.
282 return is_in_young(new_obj);
283 }
284
285 // The "requestor" generation is performing some garbage collection
286 // action for which it would be useful to have scratch space. The
287 // requestor promises to allocate no more than "max_alloc_words" in any
288 // older generation (via promotion say.) Any blocks of space that can
289 // be provided are returned as a list of ScratchBlocks, sorted by
290 // decreasing size.
291 ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words);
292 // Allow each generation to reset any scratch space that it has
293 // contributed as it needs.
294 void release_scratch();
295
296 // Ensure parsability: override
297 virtual void ensure_parsability(bool retire_tlabs);
298
299 // Time in ms since the longest time a collector ran in
300 // in any generation.
301 virtual jlong millis_since_last_gc();
302
303 // Total number of full collections completed.
304 unsigned int total_full_collections_completed() {
305 assert(_full_collections_completed <= _total_full_collections,
306 "Can't complete more collections than were started");
307 return _full_collections_completed;
308 }
309
310 // Update above counter, as appropriate, at the end of a stop-world GC cycle
311 unsigned int update_full_collections_completed();
312 // Update above counter, as appropriate, at the end of a concurrent GC cycle
313 unsigned int update_full_collections_completed(unsigned int count);
314
315 // Update "time of last gc" for all generations to "now".
316 void update_time_of_last_gc(jlong now) {
317 _young_gen->update_time_of_last_gc(now);
318 _old_gen->update_time_of_last_gc(now);
319 }
320
321 // Update the gc statistics for each generation.
322 // "level" is the level of the latest collection.
323 void update_gc_stats(int current_level, bool full) {
324 _young_gen->update_gc_stats(current_level, full);
325 _old_gen->update_gc_stats(current_level, full);
326 }
327
328 // Override.
329 bool no_gc_in_progress() { return !is_gc_active(); }
330
331 // Override.
332 void prepare_for_verify();
333
334 // Override.
335 void verify(bool silent, VerifyOption option);
336
337 // Override.
338 virtual void print_on(outputStream* st) const;
339 virtual void print_gc_threads_on(outputStream* st) const;
340 virtual void gc_threads_do(ThreadClosure* tc) const;
341 virtual void print_tracing_info() const;
342 virtual void print_on_error(outputStream* st) const;
343
344 // PrintGC, PrintGCDetails support
345 void print_heap_change(size_t prev_used) const;
346
347 // The functions below are helper functions that a subclass of
348 // "CollectedHeap" can use in the implementation of its virtual
349 // functions.
350
351 class GenClosure : public StackObj {
352 public:
353 virtual void do_generation(Generation* gen) = 0;
354 };
355
356 // Apply "cl.do_generation" to all generations in the heap
357 // If "old_to_young" determines the order.
358 void generation_iterate(GenClosure* cl, bool old_to_young);
359
360 void space_iterate(SpaceClosure* cl);
361
362 // Return "true" if all generations have reached the
363 // maximal committed limit that they can reach, without a garbage
364 // collection.
365 virtual bool is_maximal_no_gc() const;
366
367 // This function returns the "GenRemSet" object that allows us to scan
368 // generations in a fully generational heap.
369 GenRemSet* rem_set() { return _rem_set; }
370
371 // Convenience function to be used in situations where the heap type can be
372 // asserted to be this type.
373 static GenCollectedHeap* heap();
374
375 void set_par_threads(uint t);
376 void set_n_termination(uint t);
377
378 // Invoke the "do_oop" method of one of the closures "not_older_gens"
379 // or "older_gens" on root locations for the generation at
380 // "level". (The "older_gens" closure is used for scanning references
381 // from older generations; "not_older_gens" is used everywhere else.)
382 // If "younger_gens_as_roots" is false, younger generations are
383 // not scanned as roots; in this case, the caller must be arranging to
384 // scan the younger generations itself. (For example, a generation might
385 // explicitly mark reachable objects in younger generations, to avoid
386 // excess storage retention.)
387 // The "so" argument determines which of the roots
388 // the closure is applied to:
389 // "SO_None" does none;
390 enum ScanningOption {
391 SO_None = 0x0,
392 SO_AllCodeCache = 0x8,
393 SO_ScavengeCodeCache = 0x10
394 };
395
396 private:
397 void process_roots(bool activate_scope,
398 ScanningOption so,
399 OopClosure* strong_roots,
400 OopClosure* weak_roots,
401 CLDClosure* strong_cld_closure,
402 CLDClosure* weak_cld_closure,
403 CodeBlobClosure* code_roots);
404
405 void gen_process_roots(int level,
406 bool younger_gens_as_roots,
407 bool activate_scope,
408 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 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 && !_young_gen->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