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