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 protected:
91 // In block contents verification, the number of header words to skip
92 NOT_PRODUCT(static size_t _skip_header_HeapWords;)
93
94 WorkGang* _workers;
95
96 protected:
97 // Helper functions for allocation
98 HeapWord* attempt_allocation(size_t size,
99 bool is_tlab,
100 bool first_only);
101
102 // Helper function for two callbacks below.
103 // Considers collection of the first max_level+1 generations.
104 void do_collection(bool full,
105 bool clear_all_soft_refs,
106 size_t size,
107 bool is_tlab,
108 GenerationType max_generation);
109
110 // Callback from VM_GenCollectForAllocation operation.
111 // This function does everything necessary/possible to satisfy an
112 // allocation request that failed in the youngest generation that should
113 // have handled it (including collection, expansion, etc.)
114 HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab);
115
116 // Callback from VM_GenCollectFull operation.
117 // Perform a full collection of the first max_level+1 generations.
118 virtual void do_full_collection(bool clear_all_soft_refs);
119 void do_full_collection(bool clear_all_soft_refs, GenerationType max_generation);
120
121 // Does the "cause" of GC indicate that
122 // we absolutely __must__ clear soft refs?
123 bool must_clear_all_soft_refs();
124
125 virtual CardTableModRefBSForCTRS* create_barrier_set(MemRegion heap);
126
127 public:
128 GenCollectedHeap(GenCollectorPolicy *policy);
129
130 WorkGang* workers() const { return _workers; }
131
132 // Returns JNI_OK on success
133 virtual jint initialize();
134
135 // Reserve aligned space for the heap as needed by the contained generations.
136 char* allocate(size_t alignment, ReservedSpace* heap_rs);
137
138 // Does operations required after initialization has been done.
139 void post_initialize();
140
141 // Initialize ("weak") refs processing support
142 virtual void ref_processing_init();
143
144 virtual Name kind() const {
145 return CollectedHeap::GenCollectedHeap;
146 }
147
148 virtual const char* name() const {
149 return "Serial";
150 }
151
152 Generation* young_gen() const { return _young_gen; }
153 Generation* old_gen() const { return _old_gen; }
154
155 bool is_young_gen(const Generation* gen) const { return gen == _young_gen; }
156 bool is_old_gen(const Generation* gen) const { return gen == _old_gen; }
157
158 // The generational collector policy.
159 GenCollectorPolicy* gen_policy() const { return _gen_policy; }
160
161 virtual CollectorPolicy* collector_policy() const { return gen_policy(); }
162
163 // Adaptive size policy
164 virtual AdaptiveSizePolicy* size_policy() {
165 return gen_policy()->size_policy();
166 }
167
168 // Return the (conservative) maximum heap alignment
169 static size_t conservative_max_heap_alignment() {
170 return Generation::GenGrain;
171 }
172
173 size_t capacity() const;
174 size_t used() const;
175
176 // Save the "used_region" for both generations.
177 void save_used_regions();
178
179 size_t max_capacity() const;
180
181 HeapWord* mem_allocate(size_t size, bool* gc_overhead_limit_was_exceeded);
182
183 // We may support a shared contiguous allocation area, if the youngest
184 // generation does.
185 bool supports_inline_contig_alloc() const;
186 HeapWord* volatile* top_addr() const;
187 HeapWord** end_addr() const;
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 virtual 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 generations up to and including max_generation.
198 // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry.
199 void collect(GCCause::Cause cause, GenerationType max_generation);
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 virtual bool is_in_closed_subset(const void* p) const {
210 return is_in(p);
211 }
212
213 // Returns true if the reference is to an object in the reserved space
214 // for the young generation.
215 // Assumes the the young gen address range is less than that of the old gen.
216 bool is_in_young(oop p);
217
218 #ifdef ASSERT
219 bool is_in_partial_collection(const void* p);
220 #endif
221
222 virtual bool is_scavengable(const void* addr) {
223 return is_in_young((oop)addr);
224 }
225
226 // Iteration functions.
227 void oop_iterate_no_header(OopClosure* cl);
228 void oop_iterate(ExtendedOopClosure* cl);
229 void object_iterate(ObjectClosure* cl);
230 void safe_object_iterate(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 tlab_used(Thread* thr) const;
265 virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
266 virtual HeapWord* allocate_new_tlab(size_t size);
267
268 // Can a compiler initialize a new object without store barriers?
269 // This permission only extends from the creation of a new object
270 // via a TLAB up to the first subsequent safepoint.
271 virtual bool can_elide_tlab_store_barriers() const {
272 return true;
273 }
274
275 virtual bool card_mark_must_follow_store() const {
276 return false;
277 }
278
279 // We don't need barriers for stores to objects in the
280 // young gen and, a fortiori, for initializing stores to
281 // objects therein. This applies to DefNew+Tenured and ParNew+CMS
282 // only and may need to be re-examined in case other
283 // kinds of collectors are implemented in the future.
284 virtual bool can_elide_initializing_store_barrier(oop new_obj) {
285 return is_in_young(new_obj);
286 }
287
288 // The "requestor" generation is performing some garbage collection
289 // action for which it would be useful to have scratch space. The
290 // requestor promises to allocate no more than "max_alloc_words" in any
291 // older generation (via promotion say.) Any blocks of space that can
292 // be provided are returned as a list of ScratchBlocks, sorted by
293 // decreasing size.
294 ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words);
295 // Allow each generation to reset any scratch space that it has
296 // contributed as it needs.
297 void release_scratch();
298
299 // Ensure parsability: override
300 virtual void ensure_parsability(bool retire_tlabs);
301
302 // Time in ms since the longest time a collector ran in
303 // in any generation.
304 virtual jlong millis_since_last_gc();
305
306 // Total number of full collections completed.
307 unsigned int total_full_collections_completed() {
308 assert(_full_collections_completed <= _total_full_collections,
309 "Can't complete more collections than were started");
310 return _full_collections_completed;
311 }
312
313 // Update above counter, as appropriate, at the end of a stop-world GC cycle
314 unsigned int update_full_collections_completed();
315 // Update above counter, as appropriate, at the end of a concurrent GC cycle
316 unsigned int update_full_collections_completed(unsigned int count);
317
318 // Update "time of last gc" for all generations to "now".
319 void update_time_of_last_gc(jlong now) {
320 _young_gen->update_time_of_last_gc(now);
321 _old_gen->update_time_of_last_gc(now);
322 }
323
324 // Update the gc statistics for each generation.
325 void update_gc_stats(Generation* current_generation, bool full) {
326 _old_gen->update_gc_stats(current_generation, full);
327 }
328
329 bool no_gc_in_progress() { return !is_gc_active(); }
330
331 // Override.
332 void prepare_for_verify();
333
334 // Override.
335 void verify(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 void print_heap_change(size_t young_prev_used, size_t old_prev_used) const;
345
346 // The functions below are helper functions that a subclass of
347 // "CollectedHeap" can use in the implementation of its virtual
348 // functions.
349
350 class GenClosure : public StackObj {
351 public:
352 virtual void do_generation(Generation* gen) = 0;
353 };
354
355 // Apply "cl.do_generation" to all generations in the heap
356 // If "old_to_young" determines the order.
357 void generation_iterate(GenClosure* cl, bool old_to_young);
358
359 // Return "true" if all generations have reached the
360 // maximal committed limit that they can reach, without a garbage
361 // collection.
362 virtual bool is_maximal_no_gc() const;
363
364 // This function returns the CardTableRS object that allows us to scan
365 // generations in a fully generational heap.
366 CardTableRS* rem_set() { return _rem_set; }
367
368 // Convenience function to be used in situations where the heap type can be
369 // asserted to be this type.
370 static GenCollectedHeap* heap();
371
372 // The ScanningOption determines which of the roots
373 // the closure is applied to:
374 // "SO_None" does none;
375 enum ScanningOption {
376 SO_None = 0x0,
377 SO_AllCodeCache = 0x8,
378 SO_ScavengeCodeCache = 0x10
379 };
380
381 private:
382 void process_roots(StrongRootsScope* scope,
383 ScanningOption so,
384 OopClosure* strong_roots,
385 OopClosure* weak_roots,
386 CLDClosure* strong_cld_closure,
387 CLDClosure* weak_cld_closure,
388 CodeBlobToOopClosure* code_roots);
389
390 void process_string_table_roots(StrongRootsScope* scope,
391 OopClosure* root_closure);
392
393 public:
394 void young_process_roots(StrongRootsScope* scope,
395 OopsInGenClosure* root_closure,
396 OopsInGenClosure* old_gen_closure,
397 CLDClosure* cld_closure);
398
399 // If "young_gen_as_roots" is false, younger generations are
400 // not scanned as roots; in this case, the caller must be arranging to
401 // scan the younger generations itself. (For example, a generation might
402 // explicitly mark reachable objects in younger generations, to avoid
403 // excess storage retention.)
404 void cms_process_roots(StrongRootsScope* scope,
405 bool young_gen_as_roots,
406 ScanningOption so,
407 bool only_strong_roots,
408 OopsInGenClosure* root_closure,
409 CLDClosure* cld_closure);
410
411 void full_process_roots(StrongRootsScope* scope,
412 bool is_adjust_phase,
413 ScanningOption so,
414 bool only_strong_roots,
415 OopsInGenClosure* root_closure,
416 CLDClosure* cld_closure);
417
418 // Apply "root_closure" to all the weak roots of the system.
419 // These include JNI weak roots, string table,
420 // and referents of reachable weak refs.
421 void gen_process_weak_roots(OopClosure* root_closure);
422
423 // Set the saved marks of generations, if that makes sense.
424 // In particular, if any generation might iterate over the oops
425 // in other generations, it should call this method.
426 void save_marks();
427
428 // Apply "cur->do_oop" or "older->do_oop" to all the oops in objects
429 // allocated since the last call to save_marks in generations at or above
430 // "level". The "cur" closure is
431 // applied to references in the generation at "level", and the "older"
432 // closure to older generations.
433 #define GCH_SINCE_SAVE_MARKS_ITERATE_DECL(OopClosureType, nv_suffix) \
434 void oop_since_save_marks_iterate(GenerationType start_gen, \
435 OopClosureType* cur, \
436 OopClosureType* older);
437
438 ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DECL)
439
440 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DECL
441
442 // Returns "true" iff no allocations have occurred since the last
443 // call to "save_marks".
444 bool no_allocs_since_save_marks();
445
446 // Returns true if an incremental collection is likely to fail.
447 // We optionally consult the young gen, if asked to do so;
448 // otherwise we base our answer on whether the previous incremental
449 // collection attempt failed with no corrective action as of yet.
450 bool incremental_collection_will_fail(bool consult_young) {
451 // The first disjunct remembers if an incremental collection failed, even
452 // when we thought (second disjunct) that it would not.
453 return incremental_collection_failed() ||
454 (consult_young && !_young_gen->collection_attempt_is_safe());
455 }
456
457 // If a generation bails out of an incremental collection,
458 // it sets this flag.
459 bool incremental_collection_failed() const {
460 return _incremental_collection_failed;
461 }
462 void set_incremental_collection_failed() {
463 _incremental_collection_failed = true;
464 }
465 void clear_incremental_collection_failed() {
466 _incremental_collection_failed = false;
467 }
468
469 // Promotion of obj into gen failed. Try to promote obj to higher
470 // gens in ascending order; return the new location of obj if successful.
471 // Otherwise, try expand-and-allocate for obj in both the young and old
472 // generation; return the new location of obj if successful. Otherwise, return NULL.
473 oop handle_failed_promotion(Generation* old_gen,
474 oop obj,
475 size_t obj_size);
476
477 private:
478 // Accessor for memory state verification support
479 NOT_PRODUCT(
480 static size_t skip_header_HeapWords() { return _skip_header_HeapWords; }
481 )
482
483 // Override
484 void check_for_non_bad_heap_word_value(HeapWord* addr,
485 size_t size) PRODUCT_RETURN;
486
487 // For use by mark-sweep. As implemented, mark-sweep-compact is global
488 // in an essential way: compaction is performed across generations, by
489 // iterating over spaces.
490 void prepare_for_compaction();
491
492 // Perform a full collection of the generations up to and including max_generation.
493 // This is the low level interface used by the public versions of
494 // collect() and collect_locked(). Caller holds the Heap_lock on entry.
495 void collect_locked(GCCause::Cause cause, GenerationType max_generation);
496
497 // Save the tops of the spaces in all generations
498 void record_gen_tops_before_GC() PRODUCT_RETURN;
499
500 protected:
501 void gc_prologue(bool full);
502 void gc_epilogue(bool full);
503
504 };
505
506 #endif // SHARE_VM_GC_SHARED_GENCOLLECTEDHEAP_HPP