1 /*
2 * Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved.
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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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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24
25 #ifndef SHARE_VM_GC_SHARED_GENCOLLECTEDHEAP_HPP
26 #define SHARE_VM_GC_SHARED_GENCOLLECTEDHEAP_HPP
27
28 #include "gc/shared/adaptiveSizePolicy.hpp"
29 #include "gc/shared/collectedHeap.hpp"
30 #include "gc/shared/collectorPolicy.hpp"
31 #include "gc/shared/generation.hpp"
32
33 class StrongRootsScope;
34 class SubTasksDone;
35 class WorkGang;
36
37 // A "GenCollectedHeap" is a CollectedHeap that uses generational
38 // collection. It has two generations, young and old.
39 class GenCollectedHeap : public CollectedHeap {
40 friend class GenCollectorPolicy;
41 friend class Generation;
42 friend class DefNewGeneration;
43 friend class TenuredGeneration;
44 friend class ConcurrentMarkSweepGeneration;
45 friend class CMSCollector;
46 friend class GenMarkSweep;
47 friend class VM_GenCollectForAllocation;
48 friend class VM_GenCollectFull;
49 friend class VM_GenCollectFullConcurrent;
50 friend class VM_GC_HeapInspection;
51 friend class VM_HeapDumper;
52 friend class HeapInspection;
53 friend class GCCauseSetter;
54 friend class VMStructs;
55 public:
56 friend class VM_PopulateDumpSharedSpace;
57
58 enum GenerationType {
59 YoungGen,
60 OldGen
61 };
62
63 private:
64 Generation* _young_gen;
65 Generation* _old_gen;
66
67 // The singleton CardTable Remembered Set.
68 CardTableRS* _rem_set;
69
70 // The generational collector policy.
71 GenCollectorPolicy* _gen_policy;
72
73 // Indicates that the most recent previous incremental collection failed.
74 // The flag is cleared when an action is taken that might clear the
75 // condition that caused that incremental collection to fail.
76 bool _incremental_collection_failed;
77
78 // In support of ExplicitGCInvokesConcurrent functionality
79 unsigned int _full_collections_completed;
80
81 // Data structure for claiming the (potentially) parallel tasks in
82 // (gen-specific) roots processing.
83 SubTasksDone* _process_strong_tasks;
84
85 // Collects the given generation.
86 void collect_generation(Generation* gen, bool full, size_t size, bool is_tlab,
87 bool run_verification, bool clear_soft_refs,
88 bool restore_marks_for_biased_locking);
89
90 // In block contents verification, the number of header words to skip
91 NOT_PRODUCT(static size_t _skip_header_HeapWords;)
92
93 WorkGang* _workers;
94
95 protected:
96 // Helper functions for allocation
97 HeapWord* attempt_allocation(size_t size,
98 bool is_tlab,
99 bool first_only);
100
101 // Helper function for two callbacks below.
102 // Considers collection of the first max_level+1 generations.
103 void do_collection(bool full,
104 bool clear_all_soft_refs,
105 size_t size,
106 bool is_tlab,
107 GenerationType max_generation);
108
109 // Callback from VM_GenCollectForAllocation operation.
110 // This function does everything necessary/possible to satisfy an
111 // allocation request that failed in the youngest generation that should
112 // have handled it (including collection, expansion, etc.)
113 HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab);
114
115 // Callback from VM_GenCollectFull operation.
116 // Perform a full collection of the first max_level+1 generations.
117 virtual void do_full_collection(bool clear_all_soft_refs);
118 void do_full_collection(bool clear_all_soft_refs, GenerationType max_generation);
119
120 // Does the "cause" of GC indicate that
121 // we absolutely __must__ clear soft refs?
122 bool must_clear_all_soft_refs();
123
124 public:
125 GenCollectedHeap(GenCollectorPolicy *policy);
126
127 WorkGang* workers() const { return _workers; }
128
129 // Returns JNI_OK on success
130 virtual jint initialize();
131
132 // Reserve aligned space for the heap as needed by the contained generations.
133 char* allocate(size_t alignment, 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 Name kind() const {
142 return CollectedHeap::GenCollectedHeap;
143 }
144
145 virtual const char* name() const {
146 if (UseConcMarkSweepGC) {
147 return "Concurrent Mark Sweep";
148 } else {
149 return "Serial";
150 }
151 }
152
153 Generation* young_gen() const { return _young_gen; }
154 Generation* old_gen() const { return _old_gen; }
155
156 bool is_young_gen(const Generation* gen) const { return gen == _young_gen; }
157 bool is_old_gen(const Generation* gen) const { return gen == _old_gen; }
158
159 // The generational collector policy.
160 GenCollectorPolicy* gen_policy() const { return _gen_policy; }
161
162 virtual CollectorPolicy* collector_policy() const { return gen_policy(); }
163
164 // Adaptive size policy
165 virtual AdaptiveSizePolicy* size_policy() {
166 return gen_policy()->size_policy();
167 }
168
169 // Return the (conservative) maximum heap alignment
170 static size_t conservative_max_heap_alignment() {
171 return Generation::GenGrain;
172 }
173
174 size_t capacity() const;
175 size_t used() const;
176
177 // Save the "used_region" for both generations.
178 void save_used_regions();
179
180 size_t max_capacity() const;
181
182 HeapWord* mem_allocate(size_t size, bool* gc_overhead_limit_was_exceeded);
183
184 // We may support a shared contiguous allocation area, if the youngest
185 // generation does.
186 bool supports_inline_contig_alloc() const;
187 HeapWord** top_addr() const;
188 HeapWord** end_addr() const;
189
190 // Perform a full collection of the heap; intended for use in implementing
191 // "System.gc". This implies as full a collection as the CollectedHeap
192 // supports. Caller does not hold the Heap_lock on entry.
193 void collect(GCCause::Cause cause);
194
195 // The same as above but assume that the caller holds the Heap_lock.
196 void collect_locked(GCCause::Cause cause);
197
198 // Perform a full collection of generations up to and including max_generation.
199 // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry.
200 void collect(GCCause::Cause cause, GenerationType max_generation);
201
202 // Returns "TRUE" iff "p" points into the committed areas of the heap.
203 // The methods is_in(), is_in_closed_subset() and is_in_youngest() may
204 // be expensive to compute in general, so, to prevent
205 // their inadvertent use in product jvm's, we restrict their use to
206 // assertion checking or verification only.
207 bool is_in(const void* p) const;
208
209 // override
210 bool is_in_closed_subset(const void* p) const {
211 if (UseConcMarkSweepGC) {
212 return is_in_reserved(p);
213 } else {
214 return is_in(p);
215 }
216 }
217
218 // Returns true if the reference is to an object in the reserved space
219 // for the young generation.
220 // Assumes the the young gen address range is less than that of the old gen.
221 bool is_in_young(oop p);
222
223 #ifdef ASSERT
224 bool is_in_partial_collection(const void* p);
225 #endif
226
227 virtual bool is_scavengable(const void* addr) {
228 return is_in_young((oop)addr);
229 }
230
231 // Iteration functions.
232 void oop_iterate_no_header(OopClosure* cl);
233 void oop_iterate(ExtendedOopClosure* cl);
234 void object_iterate(ObjectClosure* cl);
235 void safe_object_iterate(ObjectClosure* cl);
236 Space* space_containing(const void* addr) const;
237
238 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
239 // each address in the (reserved) heap is a member of exactly
240 // one block. The defining characteristic of a block is that it is
241 // possible to find its size, and thus to progress forward to the next
242 // block. (Blocks may be of different sizes.) Thus, blocks may
243 // represent Java objects, or they might be free blocks in a
244 // free-list-based heap (or subheap), as long as the two kinds are
245 // distinguishable and the size of each is determinable.
246
247 // Returns the address of the start of the "block" that contains the
248 // address "addr". We say "blocks" instead of "object" since some heaps
249 // may not pack objects densely; a chunk may either be an object or a
250 // non-object.
251 virtual HeapWord* block_start(const void* addr) const;
252
253 // Requires "addr" to be the start of a chunk, and returns its size.
254 // "addr + size" is required to be the start of a new chunk, or the end
255 // of the active area of the heap. Assumes (and verifies in non-product
256 // builds) that addr is in the allocated part of the heap and is
257 // the start of a chunk.
258 virtual size_t block_size(const HeapWord* addr) const;
259
260 // Requires "addr" to be the start of a block, and returns "TRUE" iff
261 // the block is an object. Assumes (and verifies in non-product
262 // builds) that addr is in the allocated part of the heap and is
263 // the start of a chunk.
264 virtual bool block_is_obj(const HeapWord* addr) const;
265
266 // Section on TLAB's.
267 virtual bool supports_tlab_allocation() const;
268 virtual size_t tlab_capacity(Thread* thr) const;
269 virtual size_t tlab_used(Thread* thr) const;
270 virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
271 virtual HeapWord* allocate_new_tlab(size_t size);
272
273 // Can a compiler initialize a new object without store barriers?
274 // This permission only extends from the creation of a new object
275 // via a TLAB up to the first subsequent safepoint.
276 virtual bool can_elide_tlab_store_barriers() const {
277 return true;
278 }
279
280 virtual bool card_mark_must_follow_store() const {
281 return UseConcMarkSweepGC;
282 }
283
284 virtual bool needs_reference_pending_list_locker_thread() const {
285 return UseConcMarkSweepGC;
286 }
287
288 // We don't need barriers for stores to objects in the
289 // young gen and, a fortiori, for initializing stores to
290 // objects therein. This applies to DefNew+Tenured and ParNew+CMS
291 // only and may need to be re-examined in case other
292 // kinds of collectors are implemented in the future.
293 virtual bool can_elide_initializing_store_barrier(oop new_obj) {
294 return is_in_young(new_obj);
295 }
296
297 // The "requestor" generation is performing some garbage collection
298 // action for which it would be useful to have scratch space. The
299 // requestor promises to allocate no more than "max_alloc_words" in any
300 // older generation (via promotion say.) Any blocks of space that can
301 // be provided are returned as a list of ScratchBlocks, sorted by
302 // decreasing size.
303 ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words);
304 // Allow each generation to reset any scratch space that it has
305 // contributed as it needs.
306 void release_scratch();
307
308 // Ensure parsability: override
309 virtual void ensure_parsability(bool retire_tlabs);
310
311 // Time in ms since the longest time a collector ran in
312 // in any generation.
313 virtual jlong millis_since_last_gc();
314
315 // Total number of full collections completed.
316 unsigned int total_full_collections_completed() {
317 assert(_full_collections_completed <= _total_full_collections,
318 "Can't complete more collections than were started");
319 return _full_collections_completed;
320 }
321
322 // Update above counter, as appropriate, at the end of a stop-world GC cycle
323 unsigned int update_full_collections_completed();
324 // Update above counter, as appropriate, at the end of a concurrent GC cycle
325 unsigned int update_full_collections_completed(unsigned int count);
326
327 // Update "time of last gc" for all generations to "now".
328 void update_time_of_last_gc(jlong now) {
329 _young_gen->update_time_of_last_gc(now);
330 _old_gen->update_time_of_last_gc(now);
331 }
332
333 // Update the gc statistics for each generation.
334 void update_gc_stats(Generation* current_generation, bool full) {
335 _old_gen->update_gc_stats(current_generation, full);
336 }
337
338 bool no_gc_in_progress() { return !is_gc_active(); }
339
340 // Override.
341 void prepare_for_verify();
342
343 // Override.
344 void verify(VerifyOption option);
345
346 // Override.
347 virtual void print_on(outputStream* st) const;
348 virtual void print_gc_threads_on(outputStream* st) const;
349 virtual void gc_threads_do(ThreadClosure* tc) const;
350 virtual void print_tracing_info() const;
351 virtual void print_on_error(outputStream* st) const;
352
353 void print_heap_change(size_t young_prev_used, size_t old_prev_used) const;
354
355 // The functions below are helper functions that a subclass of
356 // "CollectedHeap" can use in the implementation of its virtual
357 // functions.
358
359 class GenClosure : public StackObj {
360 public:
361 virtual void do_generation(Generation* gen) = 0;
362 };
363
364 // Apply "cl.do_generation" to all generations in the heap
365 // If "old_to_young" determines the order.
366 void generation_iterate(GenClosure* cl, bool old_to_young);
367
368 // Return "true" if all generations have reached the
369 // maximal committed limit that they can reach, without a garbage
370 // collection.
371 virtual bool is_maximal_no_gc() const;
372
373 // This function returns the CardTableRS object that allows us to scan
374 // generations in a fully generational heap.
375 CardTableRS* rem_set() { return _rem_set; }
376
377 // Convenience function to be used in situations where the heap type can be
378 // asserted to be this type.
379 static GenCollectedHeap* heap();
380
381 // Invoke the "do_oop" method of one of the closures "not_older_gens"
382 // or "older_gens" on root locations for the generations depending on
383 // the type. (The "older_gens" closure is used for scanning references
384 // from older generations; "not_older_gens" is used everywhere else.)
385 // If "younger_gens_as_roots" is false, younger generations are
386 // not scanned as roots; in this case, the caller must be arranging to
387 // scan the younger generations itself. (For example, a generation might
388 // explicitly mark reachable objects in younger generations, to avoid
389 // excess storage retention.)
390 // The "so" argument determines which of the roots
391 // the closure is applied to:
392 // "SO_None" does none;
393 enum ScanningOption {
394 SO_None = 0x0,
395 SO_AllCodeCache = 0x8,
396 SO_ScavengeCodeCache = 0x10
397 };
398
399 private:
400 void process_roots(StrongRootsScope* scope,
401 ScanningOption so,
402 OopClosure* strong_roots,
403 OopClosure* weak_roots,
404 CLDClosure* strong_cld_closure,
405 CLDClosure* weak_cld_closure,
406 CodeBlobToOopClosure* code_roots);
407
408 public:
409 static const bool StrongAndWeakRoots = false;
410 static const bool StrongRootsOnly = true;
411
412 void gen_process_roots(StrongRootsScope* scope,
413 GenerationType type,
414 bool young_gen_as_roots,
415 ScanningOption so,
416 bool only_strong_roots,
417 OopsInGenClosure* not_older_gens,
418 OopsInGenClosure* older_gens,
419 CLDClosure* cld_closure);
420
421 // Apply "root_closure" to all the weak roots of the system.
422 // These include JNI weak roots, string table,
423 // and referents of reachable weak refs.
424 void gen_process_weak_roots(OopClosure* root_closure);
425
426 // Set the saved marks of generations, if that makes sense.
427 // In particular, if any generation might iterate over the oops
428 // in other generations, it should call this method.
429 void save_marks();
430
431 // Apply "cur->do_oop" or "older->do_oop" to all the oops in objects
432 // allocated since the last call to save_marks in generations at or above
433 // "level". The "cur" closure is
434 // applied to references in the generation at "level", and the "older"
435 // closure to older generations.
436 #define GCH_SINCE_SAVE_MARKS_ITERATE_DECL(OopClosureType, nv_suffix) \
437 void oop_since_save_marks_iterate(GenerationType start_gen, \
438 OopClosureType* cur, \
439 OopClosureType* older);
440
441 ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DECL)
442
443 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DECL
444
445 // Returns "true" iff no allocations have occurred since the last
446 // call to "save_marks".
447 bool no_allocs_since_save_marks();
448
449 // Returns true if an incremental collection is likely to fail.
450 // We optionally consult the young gen, if asked to do so;
451 // otherwise we base our answer on whether the previous incremental
452 // collection attempt failed with no corrective action as of yet.
453 bool incremental_collection_will_fail(bool consult_young) {
454 // The first disjunct remembers if an incremental collection failed, even
455 // when we thought (second disjunct) that it would not.
456 return incremental_collection_failed() ||
457 (consult_young && !_young_gen->collection_attempt_is_safe());
458 }
459
460 // If a generation bails out of an incremental collection,
461 // it sets this flag.
462 bool incremental_collection_failed() const {
463 return _incremental_collection_failed;
464 }
465 void set_incremental_collection_failed() {
466 _incremental_collection_failed = true;
467 }
468 void clear_incremental_collection_failed() {
469 _incremental_collection_failed = false;
470 }
471
472 // Promotion of obj into gen failed. Try to promote obj to higher
473 // gens in ascending order; return the new location of obj if successful.
474 // Otherwise, try expand-and-allocate for obj in both the young and old
475 // generation; return the new location of obj if successful. Otherwise, return NULL.
476 oop handle_failed_promotion(Generation* old_gen,
477 oop obj,
478 size_t obj_size);
479
480 private:
481 // Accessor for memory state verification support
482 NOT_PRODUCT(
483 static size_t skip_header_HeapWords() { return _skip_header_HeapWords; }
484 )
485
486 // Override
487 void check_for_non_bad_heap_word_value(HeapWord* addr,
488 size_t size) PRODUCT_RETURN;
489
490 // For use by mark-sweep. As implemented, mark-sweep-compact is global
491 // in an essential way: compaction is performed across generations, by
492 // iterating over spaces.
493 void prepare_for_compaction();
494
495 // Perform a full collection of the generations up to and including max_generation.
496 // This is the low level interface used by the public versions of
497 // collect() and collect_locked(). Caller holds the Heap_lock on entry.
498 void collect_locked(GCCause::Cause cause, GenerationType max_generation);
499
500 // Returns success or failure.
501 bool create_cms_collector();
502
503 // In support of ExplicitGCInvokesConcurrent functionality
504 bool should_do_concurrent_full_gc(GCCause::Cause cause);
505 void collect_mostly_concurrent(GCCause::Cause cause);
506
507 // Save the tops of the spaces in all generations
508 void record_gen_tops_before_GC() PRODUCT_RETURN;
509
510 protected:
511 void gc_prologue(bool full);
512 void gc_epilogue(bool full);
513
514 public:
515 void stop();
516 };
517
518 #endif // SHARE_VM_GC_SHARED_GENCOLLECTEDHEAP_HPP