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