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 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) strong roots processing.
82 SubTasksDone* _gen_process_strong_tasks;
83 SubTasksDone* gen_process_strong_tasks() { return _gen_process_strong_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 // Directs each generation up to and including "collectedGen" to recompute
90 // its desired size.
91 void compute_new_generation_sizes(int collectedGen);
92
93 // Helper functions for allocation
94 HeapWord* attempt_allocation(size_t size,
95 bool is_tlab,
96 bool first_only);
97
98 // Helper function for two callbacks below.
99 // Considers collection of the first max_level+1 generations.
100 void do_collection(bool full,
101 bool clear_all_soft_refs,
102 size_t size,
103 bool is_tlab,
104 int max_level);
105
106 // Callback from VM_GenCollectForAllocation operation.
107 // This function does everything necessary/possible to satisfy an
108 // allocation request that failed in the youngest generation that should
109 // have handled it (including collection, expansion, etc.)
110 HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab);
111
112 // Callback from VM_GenCollectFull operation.
113 // Perform a full collection of the first max_level+1 generations.
114 virtual void do_full_collection(bool clear_all_soft_refs);
115 void do_full_collection(bool clear_all_soft_refs, int max_level);
116
117 // Does the "cause" of GC indicate that
118 // we absolutely __must__ clear soft refs?
119 bool must_clear_all_soft_refs();
120
121 public:
122 GenCollectedHeap(GenCollectorPolicy *policy);
123
124 GCStats* gc_stats(int level) const;
125
126 // Returns JNI_OK on success
127 virtual jint initialize();
128 char* allocate(size_t alignment,
129 size_t* _total_reserved, int* _n_covered_regions,
130 ReservedSpace* heap_rs);
131
132 // Does operations required after initialization has been done.
133 void post_initialize();
134
135 // Initialize ("weak") refs processing support
136 virtual void ref_processing_init();
137
138 virtual CollectedHeap::Name kind() const {
139 return CollectedHeap::GenCollectedHeap;
140 }
141
142 // The generational collector policy.
143 GenCollectorPolicy* gen_policy() const { return _gen_policy; }
144 virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) gen_policy(); }
145
146 // Adaptive size policy
147 virtual AdaptiveSizePolicy* size_policy() {
148 return gen_policy()->size_policy();
149 }
150
151 // return the (conservative) maximum heap alignment
152 static size_t max_heap_alignment() {
153 return Generation::GenGrain;
154 }
155
156 size_t capacity() const;
157 size_t used() const;
158
159 // Save the "used_region" for generations level and lower.
160 void save_used_regions(int level);
161
162 size_t max_capacity() const;
163
164 HeapWord* mem_allocate(size_t size,
165 bool* gc_overhead_limit_was_exceeded);
166
167 // We may support a shared contiguous allocation area, if the youngest
168 // generation does.
169 bool supports_inline_contig_alloc() const;
170 HeapWord** top_addr() const;
171 HeapWord** end_addr() const;
172
173 // Return an estimate of the maximum allocation that could be performed
174 // without triggering any collection activity. In a generational
175 // collector, for example, this is probably the largest allocation that
176 // could be supported in the youngest generation. It is "unsafe" because
177 // no locks are taken; the result should be treated as an approximation,
178 // not a guarantee.
179 size_t unsafe_max_alloc();
180
181 // Does this heap support heap inspection? (+PrintClassHistogram)
182 virtual bool supports_heap_inspection() const { return true; }
183
184 // Perform a full collection of the heap; intended for use in implementing
185 // "System.gc". This implies as full a collection as the CollectedHeap
186 // supports. Caller does not hold the Heap_lock on entry.
187 void collect(GCCause::Cause cause);
188
189 // The same as above but assume that the caller holds the Heap_lock.
190 void collect_locked(GCCause::Cause cause);
191
192 // Perform a full collection of the first max_level+1 generations.
193 // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry.
194 void collect(GCCause::Cause cause, int max_level);
195
196 // Returns "TRUE" iff "p" points into the committed areas of the heap.
197 // The methods is_in(), is_in_closed_subset() and is_in_youngest() may
198 // be expensive to compute in general, so, to prevent
199 // their inadvertent use in product jvm's, we restrict their use to
200 // assertion checking or verification only.
201 bool is_in(const void* p) const;
202
203 // override
204 bool is_in_closed_subset(const void* p) const {
205 if (UseConcMarkSweepGC) {
206 return is_in_reserved(p);
207 } else {
208 return is_in(p);
209 }
210 }
211
212 // Returns true if the reference is to an object in the reserved space
213 // for the young generation.
214 // Assumes the the young gen address range is less than that of the old gen.
215 bool is_in_young(oop p);
216
217 #ifdef ASSERT
218 virtual bool is_in_partial_collection(const void* p);
219 #endif
220
221 virtual bool is_scavengable(const void* addr) {
222 return is_in_young((oop)addr);
223 }
224
225 // Iteration functions.
226 void oop_iterate(ExtendedOopClosure* cl);
227 void oop_iterate(MemRegion mr, ExtendedOopClosure* cl);
228 void object_iterate(ObjectClosure* cl);
229 void safe_object_iterate(ObjectClosure* cl);
230 void object_iterate_since_last_GC(ObjectClosure* cl);
231 Space* space_containing(const void* addr) const;
232
233 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
234 // each address in the (reserved) heap is a member of exactly
235 // one block. The defining characteristic of a block is that it is
236 // possible to find its size, and thus to progress forward to the next
237 // block. (Blocks may be of different sizes.) Thus, blocks may
238 // represent Java objects, or they might be free blocks in a
239 // free-list-based heap (or subheap), as long as the two kinds are
240 // distinguishable and the size of each is determinable.
241
242 // Returns the address of the start of the "block" that contains the
243 // address "addr". We say "blocks" instead of "object" since some heaps
244 // may not pack objects densely; a chunk may either be an object or a
245 // non-object.
246 virtual HeapWord* block_start(const void* addr) const;
247
248 // Requires "addr" to be the start of a chunk, and returns its size.
249 // "addr + size" is required to be the start of a new chunk, or the end
250 // of the active area of the heap. Assumes (and verifies in non-product
251 // builds) that addr is in the allocated part of the heap and is
252 // the start of a chunk.
253 virtual size_t block_size(const HeapWord* addr) const;
254
255 // Requires "addr" to be the start of a block, and returns "TRUE" iff
256 // the block is an object. Assumes (and verifies in non-product
257 // builds) that addr is in the allocated part of the heap and is
258 // the start of a chunk.
259 virtual bool block_is_obj(const HeapWord* addr) const;
260
261 // Section on TLAB's.
262 virtual bool supports_tlab_allocation() const;
263 virtual size_t tlab_capacity(Thread* thr) const;
264 virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
265 virtual HeapWord* allocate_new_tlab(size_t size);
266
267 // Can a compiler initialize a new object without store barriers?
268 // This permission only extends from the creation of a new object
269 // via a TLAB up to the first subsequent safepoint.
270 virtual bool can_elide_tlab_store_barriers() const {
271 return true;
272 }
273
274 virtual bool card_mark_must_follow_store() const {
275 return UseConcMarkSweepGC;
276 }
277
278 // We don't need barriers for stores to objects in the
279 // young gen and, a fortiori, for initializing stores to
280 // objects therein. This applies to {DefNew,ParNew}+{Tenured,CMS}
281 // only and may need to be re-examined in case other
282 // kinds of collectors are implemented in the future.
283 virtual bool can_elide_initializing_store_barrier(oop new_obj) {
284 // We wanted to assert that:-
285 // assert(UseParNewGC || UseSerialGC || UseConcMarkSweepGC,
286 // "Check can_elide_initializing_store_barrier() for this collector");
287 // but unfortunately the flag UseSerialGC need not necessarily always
288 // be set when DefNew+Tenured are being used.
289 return is_in_young(new_obj);
290 }
291
292 // The "requestor" generation is performing some garbage collection
293 // action for which it would be useful to have scratch space. The
294 // requestor promises to allocate no more than "max_alloc_words" in any
295 // older generation (via promotion say.) Any blocks of space that can
296 // be provided are returned as a list of ScratchBlocks, sorted by
297 // decreasing size.
298 ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words);
299 // Allow each generation to reset any scratch space that it has
300 // contributed as it needs.
301 void release_scratch();
302
303 // Ensure parsability: override
304 virtual void ensure_parsability(bool retire_tlabs);
305
306 // Time in ms since the longest time a collector ran in
307 // in any generation.
308 virtual jlong millis_since_last_gc();
309
310 // Total number of full collections completed.
311 unsigned int total_full_collections_completed() {
312 assert(_full_collections_completed <= _total_full_collections,
313 "Can't complete more collections than were started");
314 return _full_collections_completed;
315 }
316
317 // Update above counter, as appropriate, at the end of a stop-world GC cycle
318 unsigned int update_full_collections_completed();
319 // Update above counter, as appropriate, at the end of a concurrent GC cycle
320 unsigned int update_full_collections_completed(unsigned int count);
321
322 // Update "time of last gc" for all constituent generations
323 // to "now".
324 void update_time_of_last_gc(jlong now) {
325 for (int i = 0; i < _n_gens; i++) {
326 _gens[i]->update_time_of_last_gc(now);
327 }
328 }
329
330 // Update the gc statistics for each generation.
331 // "level" is the level of the lastest collection
332 void update_gc_stats(int current_level, bool full) {
333 for (int i = 0; i < _n_gens; i++) {
334 _gens[i]->update_gc_stats(current_level, full);
335 }
336 }
337
338 // Override.
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 void space_iterate(SpaceClosure* cl);
371
372 // Return "true" if all generations have reached the
373 // maximal committed limit that they can reach, without a garbage
374 // collection.
375 virtual bool is_maximal_no_gc() const;
376
377 // Return the generation before "gen", or else NULL.
378 Generation* prev_gen(Generation* gen) const {
379 int l = gen->level();
380 if (l == 0) return NULL;
381 else return _gens[l-1];
382 }
383
384 // Return the generation after "gen", or else NULL.
385 Generation* next_gen(Generation* gen) const {
386 int l = gen->level() + 1;
387 if (l == _n_gens) return NULL;
388 else return _gens[l];
389 }
390
391 Generation* get_gen(int i) const {
392 if (i >= 0 && i < _n_gens)
393 return _gens[i];
394 else
395 return NULL;
396 }
397
398 int n_gens() const {
399 assert(_n_gens == gen_policy()->number_of_generations(), "Sanity");
400 return _n_gens;
401 }
402
403 // Convenience function to be used in situations where the heap type can be
404 // asserted to be this type.
405 static GenCollectedHeap* heap();
406
407 void set_par_threads(uint t);
408
409 // Invoke the "do_oop" method of one of the closures "not_older_gens"
410 // or "older_gens" on root locations for the generation at
411 // "level". (The "older_gens" closure is used for scanning references
412 // from older generations; "not_older_gens" is used everywhere else.)
413 // If "younger_gens_as_roots" is false, younger generations are
414 // not scanned as roots; in this case, the caller must be arranging to
415 // scan the younger generations itself. (For example, a generation might
416 // explicitly mark reachable objects in younger generations, to avoid
417 // excess storage retention.)
418 // The "so" argument determines which of the roots
419 // the closure is applied to:
420 // "SO_None" does none;
421 // "SO_AllClasses" applies the closure to all entries in the SystemDictionary;
422 // "SO_SystemClasses" to all the "system" classes and loaders;
423 // "SO_Strings" applies the closure to all entries in the StringTable.
424 void gen_process_strong_roots(int level,
425 bool younger_gens_as_roots,
426 // The remaining arguments are in an order
427 // consistent with SharedHeap::process_strong_roots:
428 bool activate_scope,
429 bool is_scavenging,
430 SharedHeap::ScanningOption so,
431 OopsInGenClosure* not_older_gens,
432 bool do_code_roots,
433 OopsInGenClosure* older_gens,
434 KlassClosure* klass_closure);
435
436 // Apply "blk" to all the weak roots of the system. These include
437 // JNI weak roots, the code cache, system dictionary, symbol table,
438 // string table, and referents of reachable weak refs.
439 void gen_process_weak_roots(OopClosure* root_closure,
440 CodeBlobClosure* code_roots);
441
442 // Set the saved marks of generations, if that makes sense.
443 // In particular, if any generation might iterate over the oops
444 // in other generations, it should call this method.
445 void save_marks();
446
447 // Apply "cur->do_oop" or "older->do_oop" to all the oops in objects
448 // allocated since the last call to save_marks in generations at or above
449 // "level". The "cur" closure is
450 // applied to references in the generation at "level", and the "older"
451 // closure to older generations.
452 #define GCH_SINCE_SAVE_MARKS_ITERATE_DECL(OopClosureType, nv_suffix) \
453 void oop_since_save_marks_iterate(int level, \
454 OopClosureType* cur, \
455 OopClosureType* older);
456
457 ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DECL)
458
459 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DECL
460
461 // Returns "true" iff no allocations have occurred in any generation at
462 // "level" or above since the last
463 // call to "save_marks".
464 bool no_allocs_since_save_marks(int level);
465
466 // Returns true if an incremental collection is likely to fail.
467 // We optionally consult the young gen, if asked to do so;
468 // otherwise we base our answer on whether the previous incremental
469 // collection attempt failed with no corrective action as of yet.
470 bool incremental_collection_will_fail(bool consult_young) {
471 // Assumes a 2-generation system; the first disjunct remembers if an
472 // incremental collection failed, even when we thought (second disjunct)
473 // that it would not.
474 assert(heap()->collector_policy()->is_two_generation_policy(),
475 "the following definition may not be suitable for an n(>2)-generation system");
476 return incremental_collection_failed() ||
477 (consult_young && !get_gen(0)->collection_attempt_is_safe());
478 }
479
480 // If a generation bails out of an incremental collection,
481 // it sets this flag.
482 bool incremental_collection_failed() const {
483 return _incremental_collection_failed;
484 }
485 void set_incremental_collection_failed() {
486 _incremental_collection_failed = true;
487 }
488 void clear_incremental_collection_failed() {
489 _incremental_collection_failed = false;
490 }
491
492 // Promotion of obj into gen failed. Try to promote obj to higher
493 // gens in ascending order; return the new location of obj if successful.
494 // Otherwise, try expand-and-allocate for obj in each generation starting at
495 // gen; return the new location of obj if successful. Otherwise, return NULL.
496 oop handle_failed_promotion(Generation* gen,
497 oop obj,
498 size_t obj_size);
499
500 private:
501 // Accessor for memory state verification support
502 NOT_PRODUCT(
503 static size_t skip_header_HeapWords() { return _skip_header_HeapWords; }
504 )
505
506 // Override
507 void check_for_non_bad_heap_word_value(HeapWord* addr,
508 size_t size) PRODUCT_RETURN;
509
510 // For use by mark-sweep. As implemented, mark-sweep-compact is global
511 // in an essential way: compaction is performed across generations, by
512 // iterating over spaces.
513 void prepare_for_compaction();
514
515 // Perform a full collection of the first max_level+1 generations.
516 // This is the low level interface used by the public versions of
517 // collect() and collect_locked(). Caller holds the Heap_lock on entry.
518 void collect_locked(GCCause::Cause cause, int max_level);
519
520 // Returns success or failure.
521 bool create_cms_collector();
522
523 // In support of ExplicitGCInvokesConcurrent functionality
524 bool should_do_concurrent_full_gc(GCCause::Cause cause);
525 void collect_mostly_concurrent(GCCause::Cause cause);
526
527 // Save the tops of the spaces in all generations
528 void record_gen_tops_before_GC() PRODUCT_RETURN;
529
530 protected:
531 virtual void gc_prologue(bool full);
532 virtual void gc_epilogue(bool full);
533 };
534
535 #endif // SHARE_VM_MEMORY_GENCOLLECTEDHEAP_HPP