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_GC_SHARED_GENCOLLECTEDHEAP_HPP
26 #define SHARE_VM_GC_SHARED_GENCOLLECTEDHEAP_HPP
27
28 #include "gc/shared/collectedHeap.hpp"
29 #include "gc/shared/collectorPolicy.hpp"
30 #include "gc/shared/generation.hpp"
31 #include "gc/shared/softRefGenPolicy.hpp"
32
33 class AdaptiveSizePolicy;
34 class StrongRootsScope;
35 class SubTasksDone;
36 class WorkGang;
37
38 // A "GenCollectedHeap" is a CollectedHeap that uses generational
39 // collection. It has two generations, young and old.
40 class GenCollectedHeap : public CollectedHeap {
41 friend class GenCollectorPolicy;
42 friend class Generation;
43 friend class DefNewGeneration;
44 friend class TenuredGeneration;
45 friend class ConcurrentMarkSweepGeneration;
46 friend class CMSCollector;
47 friend class GenMarkSweep;
48 friend class VM_GenCollectForAllocation;
49 friend class VM_GenCollectFull;
50 friend class VM_GenCollectFullConcurrent;
51 friend class VM_GC_HeapInspection;
52 friend class VM_HeapDumper;
53 friend class HeapInspection;
54 friend class GCCauseSetter;
55 friend class VMStructs;
56 public:
57 friend class VM_PopulateDumpSharedSpace;
58
59 enum GenerationType {
60 YoungGen,
61 OldGen
62 };
63
64 private:
65 Generation* _young_gen;
66 Generation* _old_gen;
67
68 // The singleton CardTable Remembered Set.
69 CardTableRS* _rem_set;
70
71 // The generational collector policy.
72 GenCollectorPolicy* _gen_policy;
73
74 SoftRefGenPolicy _soft_ref_gen_policy;
75
76 // The sizing of the heap is controlled by a sizing policy.
77 AdaptiveSizePolicy* _size_policy;
78
79 // Indicates that the most recent previous incremental collection failed.
80 // The flag is cleared when an action is taken that might clear the
81 // condition that caused that incremental collection to fail.
82 bool _incremental_collection_failed;
83
84 // In support of ExplicitGCInvokesConcurrent functionality
85 unsigned int _full_collections_completed;
86
87 // Collects the given generation.
88 void collect_generation(Generation* gen, bool full, size_t size, bool is_tlab,
89 bool run_verification, bool clear_soft_refs,
90 bool restore_marks_for_biased_locking);
91
92 // Reserve aligned space for the heap as needed by the contained generations.
93 char* allocate(size_t alignment, ReservedSpace* heap_rs);
94
95 // Initialize ("weak") refs processing support
96 void ref_processing_init();
97
98 protected:
99
100 // The set of potentially parallel tasks in root scanning.
101 enum GCH_strong_roots_tasks {
102 GCH_PS_Universe_oops_do,
103 GCH_PS_JNIHandles_oops_do,
104 GCH_PS_ObjectSynchronizer_oops_do,
105 GCH_PS_FlatProfiler_oops_do,
106 GCH_PS_Management_oops_do,
107 GCH_PS_SystemDictionary_oops_do,
108 GCH_PS_ClassLoaderDataGraph_oops_do,
109 GCH_PS_jvmti_oops_do,
110 GCH_PS_CodeCache_oops_do,
111 GCH_PS_aot_oops_do,
112 GCH_PS_younger_gens,
113 // Leave this one last.
114 GCH_PS_NumElements
115 };
116
117 // Data structure for claiming the (potentially) parallel tasks in
118 // (gen-specific) roots processing.
119 SubTasksDone* _process_strong_tasks;
120
121 GCMemoryManager* _young_manager;
122 GCMemoryManager* _old_manager;
123
124 // Helper functions for allocation
125 HeapWord* attempt_allocation(size_t size,
126 bool is_tlab,
127 bool first_only);
128
129 // Helper function for two callbacks below.
130 // Considers collection of the first max_level+1 generations.
131 void do_collection(bool full,
132 bool clear_all_soft_refs,
133 size_t size,
134 bool is_tlab,
135 GenerationType max_generation);
136
137 // Callback from VM_GenCollectForAllocation operation.
138 // This function does everything necessary/possible to satisfy an
139 // allocation request that failed in the youngest generation that should
140 // have handled it (including collection, expansion, etc.)
141 HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab);
142
143 // Callback from VM_GenCollectFull operation.
144 // Perform a full collection of the first max_level+1 generations.
145 virtual void do_full_collection(bool clear_all_soft_refs);
146 void do_full_collection(bool clear_all_soft_refs, GenerationType max_generation);
147
148 // Does the "cause" of GC indicate that
149 // we absolutely __must__ clear soft refs?
150 bool must_clear_all_soft_refs();
151
152 GenCollectedHeap(GenCollectorPolicy *policy);
153
154 virtual void check_gen_kinds() = 0;
155
156 public:
157
158 // Returns JNI_OK on success
159 virtual jint initialize();
160
161 void initialize_size_policy(size_t init_eden_size,
162 size_t init_promo_size,
163 size_t init_survivor_size);
164
165 // Does operations required after initialization has been done.
166 void post_initialize();
167
168 Generation* young_gen() const { return _young_gen; }
169 Generation* old_gen() const { return _old_gen; }
170
171 bool is_young_gen(const Generation* gen) const { return gen == _young_gen; }
172 bool is_old_gen(const Generation* gen) const { return gen == _old_gen; }
173
174 // The generational collector policy.
175 GenCollectorPolicy* gen_policy() const { return _gen_policy; }
176
177 virtual CollectorPolicy* collector_policy() const { return gen_policy(); }
178
179 virtual SoftRefPolicy* soft_ref_policy() { return &_soft_ref_gen_policy; }
180
181 // Adaptive size policy
182 virtual AdaptiveSizePolicy* size_policy() {
183 return _size_policy;
184 }
185
186 // Return the (conservative) maximum heap alignment
187 static size_t conservative_max_heap_alignment() {
188 return Generation::GenGrain;
189 }
190
191 size_t capacity() const;
192 size_t used() const;
193
194 // Save the "used_region" for both generations.
195 void save_used_regions();
196
197 size_t max_capacity() const;
198
199 HeapWord* mem_allocate(size_t size, bool* gc_overhead_limit_was_exceeded);
200
201 // We may support a shared contiguous allocation area, if the youngest
202 // generation does.
203 bool supports_inline_contig_alloc() const;
204 HeapWord* volatile* top_addr() const;
205 HeapWord** end_addr() const;
206
207 // Perform a full collection of the heap; intended for use in implementing
208 // "System.gc". This implies as full a collection as the CollectedHeap
209 // supports. Caller does not hold the Heap_lock on entry.
210 virtual void collect(GCCause::Cause cause);
211
212 // The same as above but assume that the caller holds the Heap_lock.
213 void collect_locked(GCCause::Cause cause);
214
215 // Perform a full collection of generations up to and including max_generation.
216 // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry.
217 void collect(GCCause::Cause cause, GenerationType max_generation);
218
219 // Returns "TRUE" iff "p" points into the committed areas of the heap.
220 // The methods is_in(), is_in_closed_subset() and is_in_youngest() may
221 // be expensive to compute in general, so, to prevent
222 // their inadvertent use in product jvm's, we restrict their use to
223 // assertion checking or verification only.
224 bool is_in(const void* p) const;
225
226 // Returns true if the reference is to an object in the reserved space
227 // for the young generation.
228 // Assumes the the young gen address range is less than that of the old gen.
229 bool is_in_young(oop p);
230
231 #ifdef ASSERT
232 bool is_in_partial_collection(const void* p);
233 #endif
234
235 virtual bool is_scavengable(oop obj) {
236 return is_in_young(obj);
237 }
238
239 // Optimized nmethod scanning support routines
240 virtual void register_nmethod(nmethod* nm);
241 virtual void verify_nmethod(nmethod* nmethod);
242
243 // Iteration functions.
244 void oop_iterate_no_header(OopClosure* cl);
245 void oop_iterate(ExtendedOopClosure* cl);
246 void object_iterate(ObjectClosure* cl);
247 void safe_object_iterate(ObjectClosure* cl);
248 Space* space_containing(const void* addr) const;
249
250 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
251 // each address in the (reserved) heap is a member of exactly
252 // one block. The defining characteristic of a block is that it is
253 // possible to find its size, and thus to progress forward to the next
254 // block. (Blocks may be of different sizes.) Thus, blocks may
255 // represent Java objects, or they might be free blocks in a
256 // free-list-based heap (or subheap), as long as the two kinds are
257 // distinguishable and the size of each is determinable.
258
259 // Returns the address of the start of the "block" that contains the
260 // address "addr". We say "blocks" instead of "object" since some heaps
261 // may not pack objects densely; a chunk may either be an object or a
262 // non-object.
263 virtual HeapWord* block_start(const void* addr) const;
264
265 // Requires "addr" to be the start of a chunk, and returns its size.
266 // "addr + size" is required to be the start of a new chunk, or the end
267 // of the active area of the heap. Assumes (and verifies in non-product
268 // builds) that addr is in the allocated part of the heap and is
269 // the start of a chunk.
270 virtual size_t block_size(const HeapWord* addr) const;
271
272 // Requires "addr" to be the start of a block, and returns "TRUE" iff
273 // the block is an object. Assumes (and verifies in non-product
274 // builds) that addr is in the allocated part of the heap and is
275 // the start of a chunk.
276 virtual bool block_is_obj(const HeapWord* addr) const;
277
278 // Section on TLAB's.
279 virtual bool supports_tlab_allocation() const;
280 virtual size_t tlab_capacity(Thread* thr) const;
281 virtual size_t tlab_used(Thread* thr) const;
282 virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
283 virtual HeapWord* allocate_new_tlab(size_t size);
284
285 // The "requestor" generation is performing some garbage collection
286 // action for which it would be useful to have scratch space. The
287 // requestor promises to allocate no more than "max_alloc_words" in any
288 // older generation (via promotion say.) Any blocks of space that can
289 // be provided are returned as a list of ScratchBlocks, sorted by
290 // decreasing size.
291 ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words);
292 // Allow each generation to reset any scratch space that it has
293 // contributed as it needs.
294 void release_scratch();
295
296 // Ensure parsability: override
297 virtual void ensure_parsability(bool retire_tlabs);
298
299 // Time in ms since the longest time a collector ran in
300 // in any generation.
301 virtual jlong millis_since_last_gc();
302
303 // Total number of full collections completed.
304 unsigned int total_full_collections_completed() {
305 assert(_full_collections_completed <= _total_full_collections,
306 "Can't complete more collections than were started");
307 return _full_collections_completed;
308 }
309
310 // Update above counter, as appropriate, at the end of a stop-world GC cycle
311 unsigned int update_full_collections_completed();
312 // Update above counter, as appropriate, at the end of a concurrent GC cycle
313 unsigned int update_full_collections_completed(unsigned int count);
314
315 // Update "time of last gc" for all generations to "now".
316 void update_time_of_last_gc(jlong now) {
317 _young_gen->update_time_of_last_gc(now);
318 _old_gen->update_time_of_last_gc(now);
319 }
320
321 // Update the gc statistics for each generation.
322 void update_gc_stats(Generation* current_generation, bool full) {
323 _old_gen->update_gc_stats(current_generation, full);
324 }
325
326 bool no_gc_in_progress() { return !is_gc_active(); }
327
328 // Override.
329 void prepare_for_verify();
330
331 // Override.
332 void verify(VerifyOption option);
333
334 // Override.
335 virtual void print_on(outputStream* st) const;
336 virtual void print_gc_threads_on(outputStream* st) const;
337 virtual void gc_threads_do(ThreadClosure* tc) const;
338 virtual void print_tracing_info() const;
339
340 void print_heap_change(size_t young_prev_used, size_t old_prev_used) const;
341
342 // The functions below are helper functions that a subclass of
343 // "CollectedHeap" can use in the implementation of its virtual
344 // functions.
345
346 class GenClosure : public StackObj {
347 public:
348 virtual void do_generation(Generation* gen) = 0;
349 };
350
351 // Apply "cl.do_generation" to all generations in the heap
352 // If "old_to_young" determines the order.
353 void generation_iterate(GenClosure* cl, bool old_to_young);
354
355 // Return "true" if all generations have reached the
356 // maximal committed limit that they can reach, without a garbage
357 // collection.
358 virtual bool is_maximal_no_gc() const;
359
360 // This function returns the CardTableRS object that allows us to scan
361 // generations in a fully generational heap.
362 CardTableRS* rem_set() { return _rem_set; }
363
364 // Convenience function to be used in situations where the heap type can be
365 // asserted to be this type.
366 static GenCollectedHeap* heap();
367
368 // The ScanningOption determines which of the roots
369 // the closure is applied to:
370 // "SO_None" does none;
371 enum ScanningOption {
372 SO_None = 0x0,
373 SO_AllCodeCache = 0x8,
374 SO_ScavengeCodeCache = 0x10
375 };
376
377 protected:
378 void process_roots(StrongRootsScope* scope,
379 ScanningOption so,
380 OopClosure* strong_roots,
381 OopClosure* weak_roots,
382 CLDClosure* strong_cld_closure,
383 CLDClosure* weak_cld_closure,
384 CodeBlobToOopClosure* code_roots);
385
386 void process_string_table_roots(StrongRootsScope* scope,
387 OopClosure* root_closure);
388
389 // Accessor for memory state verification support
390 NOT_PRODUCT(
391 virtual size_t skip_header_HeapWords() { return 0; }
392 )
393
394 virtual void gc_prologue(bool full);
395 virtual void gc_epilogue(bool full);
396
397 public:
398 void young_process_roots(StrongRootsScope* scope,
399 OopsInGenClosure* root_closure,
400 OopsInGenClosure* old_gen_closure,
401 CLDClosure* cld_closure);
402
403 void full_process_roots(StrongRootsScope* scope,
404 bool is_adjust_phase,
405 ScanningOption so,
406 bool only_strong_roots,
407 OopsInGenClosure* root_closure,
408 CLDClosure* cld_closure);
409
410 // Apply "root_closure" to all the weak roots of the system.
411 // These include JNI weak roots, string table,
412 // and referents of reachable weak refs.
413 void gen_process_weak_roots(OopClosure* root_closure);
414
415 // Set the saved marks of generations, if that makes sense.
416 // In particular, if any generation might iterate over the oops
417 // in other generations, it should call this method.
418 void save_marks();
419
420 // Apply "cur->do_oop" or "older->do_oop" to all the oops in objects
421 // allocated since the last call to save_marks in generations at or above
422 // "level". The "cur" closure is
423 // applied to references in the generation at "level", and the "older"
424 // closure to older generations.
425 #define GCH_SINCE_SAVE_MARKS_ITERATE_DECL(OopClosureType, nv_suffix) \
426 void oop_since_save_marks_iterate(GenerationType start_gen, \
427 OopClosureType* cur, \
428 OopClosureType* older);
429
430 ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DECL)
431
432 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DECL
433
434 // Returns "true" iff no allocations have occurred since the last
435 // call to "save_marks".
436 bool no_allocs_since_save_marks();
437
438 // Returns true if an incremental collection is likely to fail.
439 // We optionally consult the young gen, if asked to do so;
440 // otherwise we base our answer on whether the previous incremental
441 // collection attempt failed with no corrective action as of yet.
442 bool incremental_collection_will_fail(bool consult_young) {
443 // The first disjunct remembers if an incremental collection failed, even
444 // when we thought (second disjunct) that it would not.
445 return incremental_collection_failed() ||
446 (consult_young && !_young_gen->collection_attempt_is_safe());
447 }
448
449 // If a generation bails out of an incremental collection,
450 // it sets this flag.
451 bool incremental_collection_failed() const {
452 return _incremental_collection_failed;
453 }
454 void set_incremental_collection_failed() {
455 _incremental_collection_failed = true;
456 }
457 void clear_incremental_collection_failed() {
458 _incremental_collection_failed = false;
459 }
460
461 // Promotion of obj into gen failed. Try to promote obj to higher
462 // gens in ascending order; return the new location of obj if successful.
463 // Otherwise, try expand-and-allocate for obj in both the young and old
464 // generation; return the new location of obj if successful. Otherwise, return NULL.
465 oop handle_failed_promotion(Generation* old_gen,
466 oop obj,
467 size_t obj_size);
468
469
470 private:
471 // Return true if an allocation should be attempted in the older generation
472 // if it fails in the younger generation. Return false, otherwise.
473 bool should_try_older_generation_allocation(size_t word_size) const;
474
475 // Try to allocate space by expanding the heap.
476 HeapWord* expand_heap_and_allocate(size_t size, bool is_tlab);
477
478 HeapWord* mem_allocate_work(size_t size,
479 bool is_tlab,
480 bool* gc_overhead_limit_was_exceeded);
481
482 // Override
483 void check_for_non_bad_heap_word_value(HeapWord* addr,
484 size_t size) PRODUCT_RETURN;
485
486 // For use by mark-sweep. As implemented, mark-sweep-compact is global
487 // in an essential way: compaction is performed across generations, by
488 // iterating over spaces.
489 void prepare_for_compaction();
490
491 // Perform a full collection of the generations up to and including max_generation.
492 // This is the low level interface used by the public versions of
493 // collect() and collect_locked(). Caller holds the Heap_lock on entry.
494 void collect_locked(GCCause::Cause cause, GenerationType max_generation);
495
496 // Save the tops of the spaces in all generations
497 void record_gen_tops_before_GC() PRODUCT_RETURN;
498 };
499
500 #endif // SHARE_VM_GC_SHARED_GENCOLLECTEDHEAP_HPP