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