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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/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 // Collects the given generation.
82 void collect_generation(Generation* gen, bool full, size_t size, bool is_tlab,
83 bool run_verification, bool clear_soft_refs,
84 bool restore_marks_for_biased_locking);
85
86 // Reserve aligned space for the heap as needed by the contained generations.
87 char* allocate(size_t alignment, ReservedSpace* heap_rs);
88
89 // Initialize ("weak") refs processing support
90 void ref_processing_init();
91
92 protected:
93
94 // The set of potentially parallel tasks in root scanning.
95 enum GCH_strong_roots_tasks {
96 GCH_PS_Universe_oops_do,
97 GCH_PS_JNIHandles_oops_do,
98 GCH_PS_ObjectSynchronizer_oops_do,
99 GCH_PS_FlatProfiler_oops_do,
100 GCH_PS_Management_oops_do,
101 GCH_PS_SystemDictionary_oops_do,
102 GCH_PS_ClassLoaderDataGraph_oops_do,
103 GCH_PS_jvmti_oops_do,
104 GCH_PS_CodeCache_oops_do,
105 GCH_PS_aot_oops_do,
106 GCH_PS_younger_gens,
107 // Leave this one last.
108 GCH_PS_NumElements
109 };
110
111 // Data structure for claiming the (potentially) parallel tasks in
112 // (gen-specific) roots processing.
113 SubTasksDone* _process_strong_tasks;
114
115 GCMemoryManager* _young_manager;
116 GCMemoryManager* _old_manager;
117
118 // Helper functions for allocation
119 HeapWord* attempt_allocation(size_t size,
120 bool is_tlab,
121 bool first_only);
122
123 // Helper function for two callbacks below.
124 // Considers collection of the first max_level+1 generations.
125 void do_collection(bool full,
126 bool clear_all_soft_refs,
127 size_t size,
128 bool is_tlab,
129 GenerationType max_generation);
130
131 // Callback from VM_GenCollectForAllocation operation.
132 // This function does everything necessary/possible to satisfy an
133 // allocation request that failed in the youngest generation that should
134 // have handled it (including collection, expansion, etc.)
135 HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab);
136
137 // Callback from VM_GenCollectFull operation.
138 // Perform a full collection of the first max_level+1 generations.
139 virtual void do_full_collection(bool clear_all_soft_refs);
140 void do_full_collection(bool clear_all_soft_refs, GenerationType max_generation);
141
142 // Does the "cause" of GC indicate that
143 // we absolutely __must__ clear soft refs?
144 bool must_clear_all_soft_refs();
145
146 GenCollectedHeap(GenCollectorPolicy *policy);
147
148 virtual void check_gen_kinds() = 0;
149
150 public:
151
152 // Returns JNI_OK on success
153 virtual jint initialize();
154
155 // Does operations required after initialization has been done.
156 void post_initialize();
157
158 Generation* young_gen() const { return _young_gen; }
159 Generation* old_gen() const { return _old_gen; }
160
161 bool is_young_gen(const Generation* gen) const { return gen == _young_gen; }
162 bool is_old_gen(const Generation* gen) const { return gen == _old_gen; }
163
164 // The generational collector policy.
165 GenCollectorPolicy* gen_policy() const { return _gen_policy; }
166
167 virtual CollectorPolicy* collector_policy() const { return gen_policy(); }
168
169 // Adaptive size policy
170 virtual AdaptiveSizePolicy* size_policy() {
171 return gen_policy()->size_policy();
172 }
173
174 // Return the (conservative) maximum heap alignment
175 static size_t conservative_max_heap_alignment() {
176 return Generation::GenGrain;
177 }
178
179 size_t capacity() const;
180 size_t used() const;
181
182 // Save the "used_region" for both generations.
183 void save_used_regions();
184
185 size_t max_capacity() const;
186
187 HeapWord* mem_allocate(size_t size, bool* gc_overhead_limit_was_exceeded);
188
189 // We may support a shared contiguous allocation area, if the youngest
190 // generation does.
191 bool supports_inline_contig_alloc() const;
192 HeapWord* volatile* top_addr() const;
193 HeapWord** end_addr() const;
194
195 // Perform a full collection of the heap; intended for use in implementing
196 // "System.gc". This implies as full a collection as the CollectedHeap
197 // supports. Caller does not hold the Heap_lock on entry.
198 virtual void collect(GCCause::Cause cause);
199
200 // The same as above but assume that the caller holds the Heap_lock.
201 void collect_locked(GCCause::Cause cause);
202
203 // Perform a full collection of generations up to and including max_generation.
204 // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry.
205 void collect(GCCause::Cause cause, GenerationType max_generation);
206
207 // Returns "TRUE" iff "p" points into the committed areas of the heap.
208 // The methods is_in(), is_in_closed_subset() and is_in_youngest() may
209 // be expensive to compute in general, so, to prevent
210 // their inadvertent use in product jvm's, we restrict their use to
211 // assertion checking or verification only.
212 bool is_in(const void* p) const;
213
214 // Returns true if the reference is to an object in the reserved space
215 // for the young generation.
216 // Assumes the the young gen address range is less than that of the old gen.
217 bool is_in_young(oop p);
218
219 #ifdef ASSERT
220 bool is_in_partial_collection(const void* p);
221 #endif
222
223 virtual bool is_scavengable(oop obj) {
224 return is_in_young(obj);
225 }
226
227 // Optimized nmethod scanning support routines
228 virtual void register_nmethod(nmethod* nm);
229 virtual void verify_nmethod(nmethod* nmethod);
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 // We don't need barriers for stores to objects in the
281 // young gen and, a fortiori, for initializing stores to
282 // objects therein. This applies to DefNew+Tenured and ParNew+CMS
283 // only and may need to be re-examined in case other
284 // kinds of collectors are implemented in the future.
285 virtual bool can_elide_initializing_store_barrier(oop new_obj) {
286 return is_in_young(new_obj);
287 }
288
289 // The "requestor" generation is performing some garbage collection
290 // action for which it would be useful to have scratch space. The
291 // requestor promises to allocate no more than "max_alloc_words" in any
292 // older generation (via promotion say.) Any blocks of space that can
293 // be provided are returned as a list of ScratchBlocks, sorted by
294 // decreasing size.
295 ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words);
296 // Allow each generation to reset any scratch space that it has
297 // contributed as it needs.
298 void release_scratch();
299
300 // Ensure parsability: override
301 virtual void ensure_parsability(bool retire_tlabs);
302
303 // Time in ms since the longest time a collector ran in
304 // in any generation.
305 virtual jlong millis_since_last_gc();
306
307 // Total number of full collections completed.
308 unsigned int total_full_collections_completed() {
309 assert(_full_collections_completed <= _total_full_collections,
310 "Can't complete more collections than were started");
311 return _full_collections_completed;
312 }
313
314 // Update above counter, as appropriate, at the end of a stop-world GC cycle
315 unsigned int update_full_collections_completed();
316 // Update above counter, as appropriate, at the end of a concurrent GC cycle
317 unsigned int update_full_collections_completed(unsigned int count);
318
319 // Update "time of last gc" for all generations to "now".
320 void update_time_of_last_gc(jlong now) {
321 _young_gen->update_time_of_last_gc(now);
322 _old_gen->update_time_of_last_gc(now);
323 }
324
325 // Update the gc statistics for each generation.
326 void update_gc_stats(Generation* current_generation, bool full) {
327 _old_gen->update_gc_stats(current_generation, full);
328 }
329
330 bool no_gc_in_progress() { return !is_gc_active(); }
331
332 // Override.
333 void prepare_for_verify();
334
335 // Override.
336 void verify(VerifyOption option);
337
338 // Override.
339 virtual void print_on(outputStream* st) const;
340 virtual void print_gc_threads_on(outputStream* st) const;
341 virtual void gc_threads_do(ThreadClosure* tc) const;
342 virtual void print_tracing_info() 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 protected:
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 // Accessor for memory state verification support
394 NOT_PRODUCT(
395 virtual size_t skip_header_HeapWords() { return 0; }
396 )
397
398 virtual void gc_prologue(bool full);
399 virtual void gc_epilogue(bool full);
400
401 public:
402 void young_process_roots(StrongRootsScope* scope,
403 OopsInGenClosure* root_closure,
404 OopsInGenClosure* old_gen_closure,
405 CLDClosure* cld_closure);
406
407 void full_process_roots(StrongRootsScope* scope,
408 bool is_adjust_phase,
409 ScanningOption so,
410 bool only_strong_roots,
411 OopsInGenClosure* root_closure,
412 CLDClosure* cld_closure);
413
414 // Apply "root_closure" to all the weak roots of the system.
415 // These include JNI weak roots, string table,
416 // and referents of reachable weak refs.
417 void gen_process_weak_roots(OopClosure* root_closure);
418
419 // Set the saved marks of generations, if that makes sense.
420 // In particular, if any generation might iterate over the oops
421 // in other generations, it should call this method.
422 void save_marks();
423
424 // Apply "cur->do_oop" or "older->do_oop" to all the oops in objects
425 // allocated since the last call to save_marks in generations at or above
426 // "level". The "cur" closure is
427 // applied to references in the generation at "level", and the "older"
428 // closure to older generations.
429 #define GCH_SINCE_SAVE_MARKS_ITERATE_DECL(OopClosureType, nv_suffix) \
430 void oop_since_save_marks_iterate(GenerationType start_gen, \
431 OopClosureType* cur, \
432 OopClosureType* older);
433
434 ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DECL)
435
436 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DECL
437
438 // Returns "true" iff no allocations have occurred since the last
439 // call to "save_marks".
440 bool no_allocs_since_save_marks();
441
442 // Returns true if an incremental collection is likely to fail.
443 // We optionally consult the young gen, if asked to do so;
444 // otherwise we base our answer on whether the previous incremental
445 // collection attempt failed with no corrective action as of yet.
446 bool incremental_collection_will_fail(bool consult_young) {
447 // The first disjunct remembers if an incremental collection failed, even
448 // when we thought (second disjunct) that it would not.
449 return incremental_collection_failed() ||
450 (consult_young && !_young_gen->collection_attempt_is_safe());
451 }
452
453 // If a generation bails out of an incremental collection,
454 // it sets this flag.
455 bool incremental_collection_failed() const {
456 return _incremental_collection_failed;
457 }
458 void set_incremental_collection_failed() {
459 _incremental_collection_failed = true;
460 }
461 void clear_incremental_collection_failed() {
462 _incremental_collection_failed = false;
463 }
464
465 // Promotion of obj into gen failed. Try to promote obj to higher
466 // gens in ascending order; return the new location of obj if successful.
467 // Otherwise, try expand-and-allocate for obj in both the young and old
468 // generation; return the new location of obj if successful. Otherwise, return NULL.
469 oop handle_failed_promotion(Generation* old_gen,
470 oop obj,
471 size_t obj_size);
472
473
474 private:
475 // Override
476 void check_for_non_bad_heap_word_value(HeapWord* addr,
477 size_t size) PRODUCT_RETURN;
478
479 // For use by mark-sweep. As implemented, mark-sweep-compact is global
480 // in an essential way: compaction is performed across generations, by
481 // iterating over spaces.
482 void prepare_for_compaction();
483
484 // Perform a full collection of the generations up to and including max_generation.
485 // This is the low level interface used by the public versions of
486 // collect() and collect_locked(). Caller holds the Heap_lock on entry.
487 void collect_locked(GCCause::Cause cause, GenerationType max_generation);
488
489 // Save the tops of the spaces in all generations
490 void record_gen_tops_before_GC() PRODUCT_RETURN;
491 };
492
493 #endif // SHARE_VM_GC_SHARED_GENCOLLECTEDHEAP_HPP