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