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 class FlexibleWorkGang;
35
36 // A "GenCollectedHeap" is a SharedHeap that uses generational
37 // collection. It has two generations, young and old.
38 class GenCollectedHeap : public SharedHeap {
39 friend class GenCollectorPolicy;
40 friend class Generation;
41 friend class DefNewGeneration;
42 friend class TenuredGeneration;
43 friend class ConcurrentMarkSweepGeneration;
44 friend class CMSCollector;
45 friend class GenMarkSweep;
46 friend class VM_GenCollectForAllocation;
47 friend class VM_GenCollectFull;
48 friend class VM_GenCollectFullConcurrent;
49 friend class VM_GC_HeapInspection;
50 friend class VM_HeapDumper;
51 friend class HeapInspection;
52 friend class GCCauseSetter;
53 friend class VMStructs;
54 public:
55 enum SomeConstants {
56 max_gens = 10
57 };
58
59 friend class VM_PopulateDumpSharedSpace;
60
61 protected:
62 // Fields:
63 static GenCollectedHeap* _gch;
64
65 private:
66 int _n_gens;
67
68 Generation* _young_gen;
69 Generation* _old_gen;
70
71 // The singleton Gen Remembered Set.
72 GenRemSet* _rem_set;
73
74 // The generational collector policy.
75 GenCollectorPolicy* _gen_policy;
76
77 // Indicates that the most recent previous incremental collection failed.
78 // The flag is cleared when an action is taken that might clear the
79 // condition that caused that incremental collection to fail.
80 bool _incremental_collection_failed;
81
82 // In support of ExplicitGCInvokesConcurrent functionality
83 unsigned int _full_collections_completed;
84
85 // Data structure for claiming the (potentially) parallel tasks in
86 // (gen-specific) roots processing.
87 SubTasksDone* _process_strong_tasks;
88
89 // Collects the given generation.
90 void collect_generation(Generation* gen, bool full, size_t size, bool is_tlab,
91 bool run_verification, bool clear_soft_refs,
92 bool restore_marks_for_biased_locking);
93
94 // In block contents verification, the number of header words to skip
95 NOT_PRODUCT(static size_t _skip_header_HeapWords;)
96
97 FlexibleWorkGang* _workers;
98
99 protected:
100 // Helper functions for allocation
101 HeapWord* attempt_allocation(size_t size,
102 bool is_tlab,
103 bool first_only);
104
105 // Helper function for two callbacks below.
106 // Considers collection of the first max_level+1 generations.
107 void do_collection(bool full,
108 bool clear_all_soft_refs,
109 size_t size,
110 bool is_tlab,
111 int max_level);
112
113 // Callback from VM_GenCollectForAllocation operation.
114 // This function does everything necessary/possible to satisfy an
115 // allocation request that failed in the youngest generation that should
116 // have handled it (including collection, expansion, etc.)
117 HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab);
118
119 // Callback from VM_GenCollectFull operation.
120 // Perform a full collection of the first max_level+1 generations.
121 virtual void do_full_collection(bool clear_all_soft_refs);
122 void do_full_collection(bool clear_all_soft_refs, int max_level);
123
124 // Does the "cause" of GC indicate that
125 // we absolutely __must__ clear soft refs?
126 bool must_clear_all_soft_refs();
127
128 public:
129 GenCollectedHeap(GenCollectorPolicy *policy);
130
131 FlexibleWorkGang* workers() const { return _workers; }
132
133 GCStats* gc_stats(int level) const;
134
135 // Returns JNI_OK on success
136 virtual jint initialize();
137
138 // Reserve aligned space for the heap as needed by the contained generations.
139 char* allocate(size_t alignment, ReservedSpace* heap_rs);
140
141 // Does operations required after initialization has been done.
142 void post_initialize();
143
144 // Initialize ("weak") refs processing support
145 virtual void ref_processing_init();
146
147 virtual CollectedHeap::Name kind() const {
148 return CollectedHeap::GenCollectedHeap;
149 }
150
151 Generation* young_gen() const { return _young_gen; }
152 Generation* old_gen() const { return _old_gen; }
153
154 // The generational collector policy.
155 GenCollectorPolicy* gen_policy() const { return _gen_policy; }
156
157 virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) gen_policy(); }
158
159 // Adaptive size policy
160 virtual AdaptiveSizePolicy* size_policy() {
161 return gen_policy()->size_policy();
162 }
163
164 // Return the (conservative) maximum heap alignment
165 static size_t conservative_max_heap_alignment() {
166 return Generation::GenGrain;
167 }
168
169 size_t capacity() const;
170 size_t used() const;
171
172 // Save the "used_region" for generations level and lower.
173 void save_used_regions(int level);
174
175 size_t max_capacity() const;
176
177 HeapWord* mem_allocate(size_t size,
178 bool* gc_overhead_limit_was_exceeded);
179
180 // We may support a shared contiguous allocation area, if the youngest
181 // generation does.
182 bool supports_inline_contig_alloc() const;
183 HeapWord** top_addr() const;
184 HeapWord** end_addr() const;
185
186 // Does this heap support heap inspection? (+PrintClassHistogram)
187 virtual bool supports_heap_inspection() const { return true; }
188
189 // Perform a full collection of the heap; intended for use in implementing
190 // "System.gc". This implies as full a collection as the CollectedHeap
191 // supports. Caller does not hold the Heap_lock on entry.
192 void collect(GCCause::Cause cause);
193
194 // The same as above but assume that the caller holds the Heap_lock.
195 void collect_locked(GCCause::Cause cause);
196
197 // Perform a full collection of the first max_level+1 generations.
198 // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry.
199 void collect(GCCause::Cause cause, int max_level);
200
201 // Returns "TRUE" iff "p" points into the committed areas of the heap.
202 // The methods is_in(), is_in_closed_subset() and is_in_youngest() may
203 // be expensive to compute in general, so, to prevent
204 // their inadvertent use in product jvm's, we restrict their use to
205 // assertion checking or verification only.
206 bool is_in(const void* p) const;
207
208 // override
209 bool is_in_closed_subset(const void* p) const {
210 if (UseConcMarkSweepGC) {
211 return is_in_reserved(p);
212 } else {
213 return is_in(p);
214 }
215 }
216
217 // Returns true if the reference is to an object in the reserved space
218 // for the young generation.
219 // Assumes the the young gen address range is less than that of the old gen.
220 bool is_in_young(oop p);
221
222 #ifdef ASSERT
223 bool is_in_partial_collection(const void* p);
224 #endif
225
226 virtual bool is_scavengable(const void* addr) {
227 return is_in_young((oop)addr);
228 }
229
230 // Iteration functions.
231 void oop_iterate(ExtendedOopClosure* cl);
232 void object_iterate(ObjectClosure* cl);
233 void safe_object_iterate(ObjectClosure* cl);
234 Space* space_containing(const void* addr) const;
235
236 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
237 // each address in the (reserved) heap is a member of exactly
238 // one block. The defining characteristic of a block is that it is
239 // possible to find its size, and thus to progress forward to the next
240 // block. (Blocks may be of different sizes.) Thus, blocks may
241 // represent Java objects, or they might be free blocks in a
242 // free-list-based heap (or subheap), as long as the two kinds are
243 // distinguishable and the size of each is determinable.
244
245 // Returns the address of the start of the "block" that contains the
246 // address "addr". We say "blocks" instead of "object" since some heaps
247 // may not pack objects densely; a chunk may either be an object or a
248 // non-object.
249 virtual HeapWord* block_start(const void* addr) const;
250
251 // Requires "addr" to be the start of a chunk, and returns its size.
252 // "addr + size" is required to be the start of a new chunk, or the end
253 // of the active area of the heap. Assumes (and verifies in non-product
254 // builds) that addr is in the allocated part of the heap and is
255 // the start of a chunk.
256 virtual size_t block_size(const HeapWord* addr) const;
257
258 // Requires "addr" to be the start of a block, and returns "TRUE" iff
259 // the block is an object. Assumes (and verifies in non-product
260 // builds) that addr is in the allocated part of the heap and is
261 // the start of a chunk.
262 virtual bool block_is_obj(const HeapWord* addr) const;
263
264 // Section on TLAB's.
265 virtual bool supports_tlab_allocation() const;
266 virtual size_t tlab_capacity(Thread* thr) const;
267 virtual size_t tlab_used(Thread* thr) const;
268 virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
269 virtual HeapWord* allocate_new_tlab(size_t size);
270
271 // Can a compiler initialize a new object without store barriers?
272 // This permission only extends from the creation of a new object
273 // via a TLAB up to the first subsequent safepoint.
274 virtual bool can_elide_tlab_store_barriers() const {
275 return true;
276 }
277
278 virtual bool card_mark_must_follow_store() const {
279 return UseConcMarkSweepGC;
280 }
281
282 // We don't need barriers for stores to objects in the
283 // young gen and, a fortiori, for initializing stores to
284 // objects therein. This applies to DefNew+Tenured and ParNew+CMS
285 // only and may need to be re-examined in case other
286 // kinds of collectors are implemented in the future.
287 virtual bool can_elide_initializing_store_barrier(oop new_obj) {
288 // We wanted to assert that:-
289 // assert(UseSerialGC || UseConcMarkSweepGC,
290 // "Check can_elide_initializing_store_barrier() for this collector");
291 // but unfortunately the flag UseSerialGC need not necessarily always
292 // be set when DefNew+Tenured are being used.
293 return is_in_young(new_obj);
294 }
295
296 // The "requestor" generation is performing some garbage collection
297 // action for which it would be useful to have scratch space. The
298 // requestor promises to allocate no more than "max_alloc_words" in any
299 // older generation (via promotion say.) Any blocks of space that can
300 // be provided are returned as a list of ScratchBlocks, sorted by
301 // decreasing size.
302 ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words);
303 // Allow each generation to reset any scratch space that it has
304 // contributed as it needs.
305 void release_scratch();
306
307 // Ensure parsability: override
308 virtual void ensure_parsability(bool retire_tlabs);
309
310 // Time in ms since the longest time a collector ran in
311 // in any generation.
312 virtual jlong millis_since_last_gc();
313
314 // Total number of full collections completed.
315 unsigned int total_full_collections_completed() {
316 assert(_full_collections_completed <= _total_full_collections,
317 "Can't complete more collections than were started");
318 return _full_collections_completed;
319 }
320
321 // Update above counter, as appropriate, at the end of a stop-world GC cycle
322 unsigned int update_full_collections_completed();
323 // Update above counter, as appropriate, at the end of a concurrent GC cycle
324 unsigned int update_full_collections_completed(unsigned int count);
325
326 // Update "time of last gc" for all generations to "now".
327 void update_time_of_last_gc(jlong now) {
328 _young_gen->update_time_of_last_gc(now);
329 _old_gen->update_time_of_last_gc(now);
330 }
331
332 // Update the gc statistics for each generation.
333 // "level" is the level of the latest collection.
334 void update_gc_stats(int current_level, bool full) {
335 _young_gen->update_gc_stats(current_level, full);
336 _old_gen->update_gc_stats(current_level, full);
337 }
338
339 bool no_gc_in_progress() { return !is_gc_active(); }
340
341 // Override.
342 void prepare_for_verify();
343
344 // Override.
345 void verify(bool silent, VerifyOption option);
346
347 // Override.
348 virtual void print_on(outputStream* st) const;
349 virtual void print_gc_threads_on(outputStream* st) const;
350 virtual void gc_threads_do(ThreadClosure* tc) const;
351 virtual void print_tracing_info() const;
352 virtual void print_on_error(outputStream* st) const;
353
354 // PrintGC, PrintGCDetails support
355 void print_heap_change(size_t prev_used) const;
356
357 // The functions below are helper functions that a subclass of
358 // "CollectedHeap" can use in the implementation of its virtual
359 // functions.
360
361 class GenClosure : public StackObj {
362 public:
363 virtual void do_generation(Generation* gen) = 0;
364 };
365
366 // Apply "cl.do_generation" to all generations in the heap
367 // If "old_to_young" determines the order.
368 void generation_iterate(GenClosure* cl, bool old_to_young);
369
370 // Return "true" if all generations have reached the
371 // maximal committed limit that they can reach, without a garbage
372 // collection.
373 virtual bool is_maximal_no_gc() const;
374
375 int n_gens() const {
376 assert(_n_gens == gen_policy()->number_of_generations(), "Sanity");
377 return _n_gens;
378 }
379
380 // This function returns the "GenRemSet" object that allows us to scan
381 // generations in a fully generational heap.
382 GenRemSet* rem_set() { return _rem_set; }
383
384 // Convenience function to be used in situations where the heap type can be
385 // asserted to be this type.
386 static GenCollectedHeap* heap();
387
388 void set_par_threads(uint t);
389 void set_n_termination(uint t);
390
391 // Invoke the "do_oop" method of one of the closures "not_older_gens"
392 // or "older_gens" on root locations for the generation at
393 // "level". (The "older_gens" closure is used for scanning references
394 // from older generations; "not_older_gens" is used everywhere else.)
395 // If "younger_gens_as_roots" is false, younger generations are
396 // not scanned as roots; in this case, the caller must be arranging to
397 // scan the younger generations itself. (For example, a generation might
398 // explicitly mark reachable objects in younger generations, to avoid
399 // excess storage retention.)
400 // The "so" argument determines which of the roots
401 // the closure is applied to:
402 // "SO_None" does none;
403 enum ScanningOption {
404 SO_None = 0x0,
405 SO_AllCodeCache = 0x8,
406 SO_ScavengeCodeCache = 0x10
407 };
408
409 private:
410 void process_roots(bool activate_scope,
411 ScanningOption so,
412 OopClosure* strong_roots,
413 OopClosure* weak_roots,
414 CLDClosure* strong_cld_closure,
415 CLDClosure* weak_cld_closure,
416 CodeBlobClosure* code_roots);
417
418 void gen_process_roots(int level,
419 bool younger_gens_as_roots,
420 bool activate_scope,
421 ScanningOption so,
422 OopsInGenClosure* not_older_gens,
423 OopsInGenClosure* weak_roots,
424 OopsInGenClosure* older_gens,
425 CLDClosure* cld_closure,
426 CLDClosure* weak_cld_closure,
427 CodeBlobClosure* code_closure);
428
429 public:
430 static const bool StrongAndWeakRoots = false;
431 static const bool StrongRootsOnly = true;
432
433 void gen_process_roots(int level,
434 bool younger_gens_as_roots,
435 bool activate_scope,
436 ScanningOption so,
437 bool only_strong_roots,
438 OopsInGenClosure* not_older_gens,
439 OopsInGenClosure* older_gens,
440 CLDClosure* cld_closure);
441
442 // Apply "root_closure" to all the weak roots of the system.
443 // These include JNI weak roots, string table,
444 // and referents of reachable weak refs.
445 void gen_process_weak_roots(OopClosure* root_closure);
446
447 // Set the saved marks of generations, if that makes sense.
448 // In particular, if any generation might iterate over the oops
449 // in other generations, it should call this method.
450 void save_marks();
451
452 // Apply "cur->do_oop" or "older->do_oop" to all the oops in objects
453 // allocated since the last call to save_marks in generations at or above
454 // "level". The "cur" closure is
455 // applied to references in the generation at "level", and the "older"
456 // closure to older generations.
457 #define GCH_SINCE_SAVE_MARKS_ITERATE_DECL(OopClosureType, nv_suffix) \
458 void oop_since_save_marks_iterate(int level, \
459 OopClosureType* cur, \
460 OopClosureType* older);
461
462 ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DECL)
463
464 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DECL
465
466 // Returns "true" iff no allocations have occurred in any generation at
467 // "level" or above since the last
468 // call to "save_marks".
469 bool no_allocs_since_save_marks(int level);
470
471 // Returns true if an incremental collection is likely to fail.
472 // We optionally consult the young gen, if asked to do so;
473 // otherwise we base our answer on whether the previous incremental
474 // collection attempt failed with no corrective action as of yet.
475 bool incremental_collection_will_fail(bool consult_young) {
476 // Assumes a 2-generation system; the first disjunct remembers if an
477 // incremental collection failed, even when we thought (second disjunct)
478 // that it would not.
479 assert(heap()->collector_policy()->is_generation_policy(),
480 "the following definition may not be suitable for an n(>2)-generation system");
481 return incremental_collection_failed() ||
482 (consult_young && !_young_gen->collection_attempt_is_safe());
483 }
484
485 // If a generation bails out of an incremental collection,
486 // it sets this flag.
487 bool incremental_collection_failed() const {
488 return _incremental_collection_failed;
489 }
490 void set_incremental_collection_failed() {
491 _incremental_collection_failed = true;
492 }
493 void clear_incremental_collection_failed() {
494 _incremental_collection_failed = false;
495 }
496
497 // Promotion of obj into gen failed. Try to promote obj to higher
498 // gens in ascending order; return the new location of obj if successful.
499 // Otherwise, try expand-and-allocate for obj in both the young and old
500 // generation; return the new location of obj if successful. Otherwise, return NULL.
501 oop handle_failed_promotion(Generation* old_gen,
502 oop obj,
503 size_t obj_size);
504
505 private:
506 // Accessor for memory state verification support
507 NOT_PRODUCT(
508 static size_t skip_header_HeapWords() { return _skip_header_HeapWords; }
509 )
510
511 // Override
512 void check_for_non_bad_heap_word_value(HeapWord* addr,
513 size_t size) PRODUCT_RETURN;
514
515 // For use by mark-sweep. As implemented, mark-sweep-compact is global
516 // in an essential way: compaction is performed across generations, by
517 // iterating over spaces.
518 void prepare_for_compaction();
519
520 // Perform a full collection of the first max_level+1 generations.
521 // This is the low level interface used by the public versions of
522 // collect() and collect_locked(). Caller holds the Heap_lock on entry.
523 void collect_locked(GCCause::Cause cause, int max_level);
524
525 // Returns success or failure.
526 bool create_cms_collector();
527
528 // In support of ExplicitGCInvokesConcurrent functionality
529 bool should_do_concurrent_full_gc(GCCause::Cause cause);
530 void collect_mostly_concurrent(GCCause::Cause cause);
531
532 // Save the tops of the spaces in all generations
533 void record_gen_tops_before_GC() PRODUCT_RETURN;
534
535 protected:
536 void gc_prologue(bool full);
537 void gc_epilogue(bool full);
538 };
539
540 #endif // SHARE_VM_MEMORY_GENCOLLECTEDHEAP_HPP