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
33 class FlexibleWorkGang;
34 class StrongRootsScope;
35 class SubTasksDone;
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 private:
59 Generation* _young_gen;
60 Generation* _old_gen;
61
62 // The singleton Gen Remembered Set.
63 GenRemSet* _rem_set;
64
65 // The generational collector policy.
66 GenCollectorPolicy* _gen_policy;
67
68 // Indicates that the most recent previous incremental collection failed.
69 // The flag is cleared when an action is taken that might clear the
70 // condition that caused that incremental collection to fail.
71 bool _incremental_collection_failed;
72
73 // In support of ExplicitGCInvokesConcurrent functionality
74 unsigned int _full_collections_completed;
75
76 // Data structure for claiming the (potentially) parallel tasks in
77 // (gen-specific) roots processing.
78 SubTasksDone* _process_strong_tasks;
79
80 // Collects the given generation.
81 void collect_generation(Generation* gen, bool full, size_t size, bool is_tlab,
82 bool run_verification, bool clear_soft_refs,
83 bool restore_marks_for_biased_locking);
84
85 // In block contents verification, the number of header words to skip
86 NOT_PRODUCT(static size_t _skip_header_HeapWords;)
87
88 FlexibleWorkGang* _workers;
89
90 protected:
91 // Helper functions for allocation
92 HeapWord* attempt_allocation(size_t size,
93 bool is_tlab,
94 bool first_only);
95
96 // Helper function for two callbacks below.
97 // Considers collection of the first max_level+1 generations.
98 void do_collection(bool full,
99 bool clear_all_soft_refs,
100 size_t size,
101 bool is_tlab,
102 Generation::Type max_generation);
103
104 // Callback from VM_GenCollectForAllocation operation.
105 // This function does everything necessary/possible to satisfy an
106 // allocation request that failed in the youngest generation that should
107 // have handled it (including collection, expansion, etc.)
108 HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab);
109
110 // Callback from VM_GenCollectFull operation.
111 // Perform a full collection of the first max_level+1 generations.
112 virtual void do_full_collection(bool clear_all_soft_refs);
113 void do_full_collection(bool clear_all_soft_refs, Generation::Type max_generation);
114
115 // Does the "cause" of GC indicate that
116 // we absolutely __must__ clear soft refs?
117 bool must_clear_all_soft_refs();
118
119 public:
120 GenCollectedHeap(GenCollectorPolicy *policy);
121
122 FlexibleWorkGang* workers() const { return _workers; }
123
124 GCStats* gc_stats(Generation* generation) const;
125
126 // Returns JNI_OK on success
127 virtual jint initialize();
128
129 // Reserve aligned space for the heap as needed by the contained generations.
130 char* allocate(size_t alignment, ReservedSpace* heap_rs);
131
132 // Does operations required after initialization has been done.
133 void post_initialize();
134
135 // Initialize ("weak") refs processing support
136 virtual void ref_processing_init();
137
138 virtual Name kind() const {
139 return CollectedHeap::GenCollectedHeap;
140 }
141
142 Generation* young_gen() const { return _young_gen; }
143 Generation* old_gen() const { return _old_gen; }
144
145 bool is_young_gen(const Generation* gen) const { return gen == _young_gen; }
146 bool is_old_gen(const Generation* gen) const { return gen == _old_gen; }
147
148 // The generational collector policy.
149 GenCollectorPolicy* gen_policy() const { return _gen_policy; }
150
151 virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) gen_policy(); }
152
153 // Adaptive size policy
154 virtual AdaptiveSizePolicy* size_policy() {
155 return gen_policy()->size_policy();
156 }
157
158 // Return the (conservative) maximum heap alignment
159 static size_t conservative_max_heap_alignment() {
160 return Generation::GenGrain;
161 }
162
163 size_t capacity() const;
164 size_t used() const;
165
166 // Save the "used_region" for both generations.
167 void save_used_regions();
168
169 size_t max_capacity() const;
170
171 HeapWord* mem_allocate(size_t size,
172 bool* gc_overhead_limit_was_exceeded);
173
174 // We may support a shared contiguous allocation area, if the youngest
175 // generation does.
176 bool supports_inline_contig_alloc() const;
177 HeapWord** top_addr() const;
178 HeapWord** end_addr() const;
179
180 // Perform a full collection of the heap; intended for use in implementing
181 // "System.gc". This implies as full a collection as the CollectedHeap
182 // supports. Caller does not hold the Heap_lock on entry.
183 void collect(GCCause::Cause cause);
184
185 // The same as above but assume that the caller holds the Heap_lock.
186 void collect_locked(GCCause::Cause cause);
187
188 // Perform a full collection of generations up to and including max_generation.
189 // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry.
190 void collect(GCCause::Cause cause, Generation::Type max_generation);
191
192 // Returns "TRUE" iff "p" points into the committed areas of the heap.
193 // The methods is_in(), is_in_closed_subset() and is_in_youngest() may
194 // be expensive to compute in general, so, to prevent
195 // their inadvertent use in product jvm's, we restrict their use to
196 // assertion checking or verification only.
197 bool is_in(const void* p) const;
198
199 // override
200 bool is_in_closed_subset(const void* p) const {
201 if (UseConcMarkSweepGC) {
202 return is_in_reserved(p);
203 } else {
204 return is_in(p);
205 }
206 }
207
208 // Returns true if the reference is to an object in the reserved space
209 // for the young generation.
210 // Assumes the the young gen address range is less than that of the old gen.
211 bool is_in_young(oop p);
212
213 #ifdef ASSERT
214 bool is_in_partial_collection(const void* p);
215 #endif
216
217 virtual bool is_scavengable(const void* addr) {
218 return is_in_young((oop)addr);
219 }
220
221 // Iteration functions.
222 void oop_iterate_no_header(OopClosure* cl);
223 void oop_iterate(ExtendedOopClosure* cl);
224 void object_iterate(ObjectClosure* cl);
225 void safe_object_iterate(ObjectClosure* cl);
226 Space* space_containing(const void* addr) const;
227
228 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
229 // each address in the (reserved) heap is a member of exactly
230 // one block. The defining characteristic of a block is that it is
231 // possible to find its size, and thus to progress forward to the next
232 // block. (Blocks may be of different sizes.) Thus, blocks may
233 // represent Java objects, or they might be free blocks in a
234 // free-list-based heap (or subheap), as long as the two kinds are
235 // distinguishable and the size of each is determinable.
236
237 // Returns the address of the start of the "block" that contains the
238 // address "addr". We say "blocks" instead of "object" since some heaps
239 // may not pack objects densely; a chunk may either be an object or a
240 // non-object.
241 virtual HeapWord* block_start(const void* addr) const;
242
243 // Requires "addr" to be the start of a chunk, and returns its size.
244 // "addr + size" is required to be the start of a new chunk, or the end
245 // of the active area of the heap. Assumes (and verifies in non-product
246 // builds) that addr is in the allocated part of the heap and is
247 // the start of a chunk.
248 virtual size_t block_size(const HeapWord* addr) const;
249
250 // Requires "addr" to be the start of a block, and returns "TRUE" iff
251 // the block is an object. Assumes (and verifies in non-product
252 // builds) that addr is in the allocated part of the heap and is
253 // the start of a chunk.
254 virtual bool block_is_obj(const HeapWord* addr) const;
255
256 // Section on TLAB's.
257 virtual bool supports_tlab_allocation() const;
258 virtual size_t tlab_capacity(Thread* thr) const;
259 virtual size_t tlab_used(Thread* thr) const;
260 virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
261 virtual HeapWord* allocate_new_tlab(size_t size);
262
263 // Can a compiler initialize a new object without store barriers?
264 // This permission only extends from the creation of a new object
265 // via a TLAB up to the first subsequent safepoint.
266 virtual bool can_elide_tlab_store_barriers() const {
267 return true;
268 }
269
270 virtual bool card_mark_must_follow_store() const {
271 return UseConcMarkSweepGC;
272 }
273
274 // We don't need barriers for stores to objects in the
275 // young gen and, a fortiori, for initializing stores to
276 // objects therein. This applies to DefNew+Tenured and ParNew+CMS
277 // only and may need to be re-examined in case other
278 // kinds of collectors are implemented in the future.
279 virtual bool can_elide_initializing_store_barrier(oop new_obj) {
280 return is_in_young(new_obj);
281 }
282
283 // The "requestor" generation is performing some garbage collection
284 // action for which it would be useful to have scratch space. The
285 // requestor promises to allocate no more than "max_alloc_words" in any
286 // older generation (via promotion say.) Any blocks of space that can
287 // be provided are returned as a list of ScratchBlocks, sorted by
288 // decreasing size.
289 ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words);
290 // Allow each generation to reset any scratch space that it has
291 // contributed as it needs.
292 void release_scratch();
293
294 // Ensure parsability: override
295 virtual void ensure_parsability(bool retire_tlabs);
296
297 // Time in ms since the longest time a collector ran in
298 // in any generation.
299 virtual jlong millis_since_last_gc();
300
301 // Total number of full collections completed.
302 unsigned int total_full_collections_completed() {
303 assert(_full_collections_completed <= _total_full_collections,
304 "Can't complete more collections than were started");
305 return _full_collections_completed;
306 }
307
308 // Update above counter, as appropriate, at the end of a stop-world GC cycle
309 unsigned int update_full_collections_completed();
310 // Update above counter, as appropriate, at the end of a concurrent GC cycle
311 unsigned int update_full_collections_completed(unsigned int count);
312
313 // Update "time of last gc" for all generations to "now".
314 void update_time_of_last_gc(jlong now) {
315 _young_gen->update_time_of_last_gc(now);
316 _old_gen->update_time_of_last_gc(now);
317 }
318
319 // Update the gc statistics for each generation.
320 void update_gc_stats(Generation* current_generation, bool full) {
321 _old_gen->update_gc_stats(current_generation, full);
322 }
323
324 bool no_gc_in_progress() { return !is_gc_active(); }
325
326 // Override.
327 void prepare_for_verify();
328
329 // Override.
330 void verify(bool silent, VerifyOption option);
331
332 // Override.
333 virtual void print_on(outputStream* st) const;
334 virtual void print_gc_threads_on(outputStream* st) const;
335 virtual void gc_threads_do(ThreadClosure* tc) const;
336 virtual void print_tracing_info() const;
337 virtual void print_on_error(outputStream* st) const;
338
339 // PrintGC, PrintGCDetails support
340 void print_heap_change(size_t 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 "GenRemSet" object that allows us to scan
361 // generations in a fully generational heap.
362 GenRemSet* 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 // Invoke the "do_oop" method of one of the closures "not_older_gens"
369 // or "older_gens" on root locations for the generations depending on
370 // the type. (The "older_gens" closure is used for scanning references
371 // from older generations; "not_older_gens" is used everywhere else.)
372 // If "younger_gens_as_roots" is false, younger generations are
373 // not scanned as roots; in this case, the caller must be arranging to
374 // scan the younger generations itself. (For example, a generation might
375 // explicitly mark reachable objects in younger generations, to avoid
376 // excess storage retention.)
377 // The "so" argument determines which of the roots
378 // the closure is applied to:
379 // "SO_None" does none;
380 enum ScanningOption {
381 SO_None = 0x0,
382 SO_AllCodeCache = 0x8,
383 SO_ScavengeCodeCache = 0x10
384 };
385
386 private:
387 void process_roots(StrongRootsScope* scope,
388 ScanningOption so,
389 OopClosure* strong_roots,
390 OopClosure* weak_roots,
391 CLDClosure* strong_cld_closure,
392 CLDClosure* weak_cld_closure,
393 CodeBlobClosure* code_roots);
394
395 public:
396 static const bool StrongAndWeakRoots = false;
397 static const bool StrongRootsOnly = true;
398
399 void gen_process_roots(StrongRootsScope* scope,
400 Generation::Type type,
401 bool younger_gens_as_roots,
402 ScanningOption so,
403 bool only_strong_roots,
404 OopsInGenClosure* not_older_gens,
405 OopsInGenClosure* older_gens,
406 CLDClosure* cld_closure);
407
408 // Apply "root_closure" to all the weak roots of the system.
409 // These include JNI weak roots, string table,
410 // and referents of reachable weak refs.
411 void gen_process_weak_roots(OopClosure* root_closure);
412
413 // Set the saved marks of generations, if that makes sense.
414 // In particular, if any generation might iterate over the oops
415 // in other generations, it should call this method.
416 void save_marks();
417
418 // Apply "cur->do_oop" or "older->do_oop" to all the oops in objects
419 // allocated since the last call to save_marks in generations at or above
420 // "level". The "cur" closure is
421 // applied to references in the generation at "level", and the "older"
422 // closure to older generations.
423 #define GCH_SINCE_SAVE_MARKS_ITERATE_DECL(OopClosureType, nv_suffix) \
424 void oop_since_save_marks_iterate(Generation::Type start_gen, \
425 OopClosureType* cur, \
426 OopClosureType* older);
427
428 ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DECL)
429
430 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DECL
431
432 // Returns "true" iff no allocations have occurred since the last
433 // call to "save_marks".
434 bool no_allocs_since_save_marks(bool include_young);
435
436 // Returns true if an incremental collection is likely to fail.
437 // We optionally consult the young gen, if asked to do so;
438 // otherwise we base our answer on whether the previous incremental
439 // collection attempt failed with no corrective action as of yet.
440 bool incremental_collection_will_fail(bool consult_young) {
441 // The first disjunct remembers if an incremental collection failed, even
442 // when we thought (second disjunct) that it would not.
443 return incremental_collection_failed() ||
444 (consult_young && !_young_gen->collection_attempt_is_safe());
445 }
446
447 // If a generation bails out of an incremental collection,
448 // it sets this flag.
449 bool incremental_collection_failed() const {
450 return _incremental_collection_failed;
451 }
452 void set_incremental_collection_failed() {
453 _incremental_collection_failed = true;
454 }
455 void clear_incremental_collection_failed() {
456 _incremental_collection_failed = false;
457 }
458
459 // Promotion of obj into gen failed. Try to promote obj to higher
460 // gens in ascending order; return the new location of obj if successful.
461 // Otherwise, try expand-and-allocate for obj in both the young and old
462 // generation; return the new location of obj if successful. Otherwise, return NULL.
463 oop handle_failed_promotion(Generation* old_gen,
464 oop obj,
465 size_t obj_size);
466
467 private:
468 // Accessor for memory state verification support
469 NOT_PRODUCT(
470 static size_t skip_header_HeapWords() { return _skip_header_HeapWords; }
471 )
472
473 // Override
474 void check_for_non_bad_heap_word_value(HeapWord* addr,
475 size_t size) PRODUCT_RETURN;
476
477 // For use by mark-sweep. As implemented, mark-sweep-compact is global
478 // in an essential way: compaction is performed across generations, by
479 // iterating over spaces.
480 void prepare_for_compaction();
481
482 // Perform a full collection of the generations up to and including max_generation.
483 // This is the low level interface used by the public versions of
484 // collect() and collect_locked(). Caller holds the Heap_lock on entry.
485 void collect_locked(GCCause::Cause cause, Generation::Type max_generation);
486
487 // Returns success or failure.
488 bool create_cms_collector();
489
490 // In support of ExplicitGCInvokesConcurrent functionality
491 bool should_do_concurrent_full_gc(GCCause::Cause cause);
492 void collect_mostly_concurrent(GCCause::Cause cause);
493
494 // Save the tops of the spaces in all generations
495 void record_gen_tops_before_GC() PRODUCT_RETURN;
496
497 protected:
498 void gc_prologue(bool full);
499 void gc_epilogue(bool full);
500 };
501
502 #endif // SHARE_VM_GC_SHARED_GENCOLLECTEDHEAP_HPP