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