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 "gc_interface/collectedHeap.hpp"
30 #include "memory/collectorPolicy.hpp"
31 #include "memory/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 int max_level);
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, int max_level);
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(int level) 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 // The generational collector policy.
146 GenCollectorPolicy* gen_policy() const { return _gen_policy; }
147
148 virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) gen_policy(); }
149
150 // Adaptive size policy
151 virtual AdaptiveSizePolicy* size_policy() {
152 return gen_policy()->size_policy();
153 }
154
155 // Return the (conservative) maximum heap alignment
156 static size_t conservative_max_heap_alignment() {
157 return Generation::GenGrain;
158 }
159
160 size_t capacity() const;
161 size_t used() const;
162
163 // Save the "used_region" for generations level and lower.
164 void save_used_regions(int level);
165
166 size_t max_capacity() const;
167
168 HeapWord* mem_allocate(size_t size,
169 bool* gc_overhead_limit_was_exceeded);
170
171 // We may support a shared contiguous allocation area, if the youngest
172 // generation does.
173 bool supports_inline_contig_alloc() const;
174 HeapWord** top_addr() const;
175 HeapWord** end_addr() const;
176
177 // Perform a full collection of the heap; intended for use in implementing
178 // "System.gc". This implies as full a collection as the CollectedHeap
179 // supports. Caller does not hold the Heap_lock on entry.
180 void collect(GCCause::Cause cause);
181
182 // The same as above but assume that the caller holds the Heap_lock.
183 void collect_locked(GCCause::Cause cause);
184
185 // Perform a full collection of the first max_level+1 generations.
186 // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry.
187 void collect(GCCause::Cause cause, int max_level);
188
189 // Returns "TRUE" iff "p" points into the committed areas of the heap.
190 // The methods is_in(), is_in_closed_subset() and is_in_youngest() may
191 // be expensive to compute in general, so, to prevent
192 // their inadvertent use in product jvm's, we restrict their use to
193 // assertion checking or verification only.
194 bool is_in(const void* p) const;
195
196 // override
197 bool is_in_closed_subset(const void* p) const {
198 if (UseConcMarkSweepGC) {
199 return is_in_reserved(p);
200 } else {
201 return is_in(p);
202 }
203 }
204
205 // Returns true if the reference is to an object in the reserved space
206 // for the young generation.
207 // Assumes the the young gen address range is less than that of the old gen.
208 bool is_in_young(oop p);
209
210 #ifdef ASSERT
211 bool is_in_partial_collection(const void* p);
212 #endif
213
214 virtual bool is_scavengable(const void* addr) {
215 return is_in_young((oop)addr);
216 }
217
218 // Iteration functions.
219 void oop_iterate_no_header(OopClosure* cl);
220 void oop_iterate(ExtendedOopClosure* cl);
221 void object_iterate(ObjectClosure* cl);
222 void safe_object_iterate(ObjectClosure* cl);
223 Space* space_containing(const void* addr) const;
224
225 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
226 // each address in the (reserved) heap is a member of exactly
227 // one block. The defining characteristic of a block is that it is
228 // possible to find its size, and thus to progress forward to the next
229 // block. (Blocks may be of different sizes.) Thus, blocks may
230 // represent Java objects, or they might be free blocks in a
231 // free-list-based heap (or subheap), as long as the two kinds are
232 // distinguishable and the size of each is determinable.
233
234 // Returns the address of the start of the "block" that contains the
235 // address "addr". We say "blocks" instead of "object" since some heaps
236 // may not pack objects densely; a chunk may either be an object or a
237 // non-object.
238 virtual HeapWord* block_start(const void* addr) const;
239
240 // Requires "addr" to be the start of a chunk, and returns its size.
241 // "addr + size" is required to be the start of a new chunk, or the end
242 // of the active area of the heap. Assumes (and verifies in non-product
243 // builds) that addr is in the allocated part of the heap and is
244 // the start of a chunk.
245 virtual size_t block_size(const HeapWord* addr) const;
246
247 // Requires "addr" to be the start of a block, and returns "TRUE" iff
248 // the block is an object. Assumes (and verifies in non-product
249 // builds) that addr is in the allocated part of the heap and is
250 // the start of a chunk.
251 virtual bool block_is_obj(const HeapWord* addr) const;
252
253 // Section on TLAB's.
254 virtual bool supports_tlab_allocation() const;
255 virtual size_t tlab_capacity(Thread* thr) const;
256 virtual size_t tlab_used(Thread* thr) const;
257 virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
258 virtual HeapWord* allocate_new_tlab(size_t size);
259
260 // Can a compiler initialize a new object without store barriers?
261 // This permission only extends from the creation of a new object
262 // via a TLAB up to the first subsequent safepoint.
263 virtual bool can_elide_tlab_store_barriers() const {
264 return true;
265 }
266
267 virtual bool card_mark_must_follow_store() const {
268 return UseConcMarkSweepGC;
269 }
270
271 // We don't need barriers for stores to objects in the
272 // young gen and, a fortiori, for initializing stores to
273 // objects therein. This applies to DefNew+Tenured and ParNew+CMS
274 // only and may need to be re-examined in case other
275 // kinds of collectors are implemented in the future.
276 virtual bool can_elide_initializing_store_barrier(oop new_obj) {
277 return is_in_young(new_obj);
278 }
279
280 // The "requestor" generation is performing some garbage collection
281 // action for which it would be useful to have scratch space. The
282 // requestor promises to allocate no more than "max_alloc_words" in any
283 // older generation (via promotion say.) Any blocks of space that can
284 // be provided are returned as a list of ScratchBlocks, sorted by
285 // decreasing size.
286 ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words);
287 // Allow each generation to reset any scratch space that it has
288 // contributed as it needs.
289 void release_scratch();
290
291 // Ensure parsability: override
292 virtual void ensure_parsability(bool retire_tlabs);
293
294 // Time in ms since the longest time a collector ran in
295 // in any generation.
296 virtual jlong millis_since_last_gc();
297
298 // Total number of full collections completed.
299 unsigned int total_full_collections_completed() {
300 assert(_full_collections_completed <= _total_full_collections,
301 "Can't complete more collections than were started");
302 return _full_collections_completed;
303 }
304
305 // Update above counter, as appropriate, at the end of a stop-world GC cycle
306 unsigned int update_full_collections_completed();
307 // Update above counter, as appropriate, at the end of a concurrent GC cycle
308 unsigned int update_full_collections_completed(unsigned int count);
309
310 // Update "time of last gc" for all generations to "now".
311 void update_time_of_last_gc(jlong now) {
312 _young_gen->update_time_of_last_gc(now);
313 _old_gen->update_time_of_last_gc(now);
314 }
315
316 // Update the gc statistics for each generation.
317 // "level" is the level of the latest collection.
318 void update_gc_stats(int current_level, bool full) {
319 _young_gen->update_gc_stats(current_level, full);
320 _old_gen->update_gc_stats(current_level, full);
321 }
322
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 // Return "true" if all generations have reached the
355 // maximal committed limit that they can reach, without a garbage
356 // collection.
357 virtual bool is_maximal_no_gc() const;
358
359 // This function returns the "GenRemSet" object that allows us to scan
360 // generations in a fully generational heap.
361 GenRemSet* rem_set() { return _rem_set; }
362
363 // Convenience function to be used in situations where the heap type can be
364 // asserted to be this type.
365 static GenCollectedHeap* heap();
366
367 void set_par_threads(uint t);
368 void set_n_termination(uint t);
369
370 // Invoke the "do_oop" method of one of the closures "not_older_gens"
371 // or "older_gens" on root locations for the generation at
372 // "level". (The "older_gens" closure is used for scanning references
373 // from older generations; "not_older_gens" is used everywhere else.)
374 // If "younger_gens_as_roots" is false, younger generations are
375 // not scanned as roots; in this case, the caller must be arranging to
376 // scan the younger generations itself. (For example, a generation might
377 // explicitly mark reachable objects in younger generations, to avoid
378 // excess storage retention.)
379 // The "so" argument determines which of the roots
380 // the closure is applied to:
381 // "SO_None" does none;
382 enum ScanningOption {
383 SO_None = 0x0,
384 SO_AllCodeCache = 0x8,
385 SO_ScavengeCodeCache = 0x10
386 };
387
388 private:
389 void process_roots(StrongRootsScope* scope,
390 ScanningOption so,
391 OopClosure* strong_roots,
392 OopClosure* weak_roots,
393 CLDClosure* strong_cld_closure,
394 CLDClosure* weak_cld_closure,
395 CodeBlobClosure* code_roots);
396
397 public:
398 static const bool StrongAndWeakRoots = false;
399 static const bool StrongRootsOnly = true;
400
401 void gen_process_roots(StrongRootsScope* scpe,
402 int level,
403 bool younger_gens_as_roots,
404 ScanningOption so,
405 bool only_strong_roots,
406 OopsInGenClosure* not_older_gens,
407 OopsInGenClosure* older_gens,
408 CLDClosure* cld_closure);
409
410 // Apply "root_closure" to all the weak roots of the system.
411 // These include JNI weak roots, string table,
412 // and referents of reachable weak refs.
413 void gen_process_weak_roots(OopClosure* root_closure);
414
415 // Set the saved marks of generations, if that makes sense.
416 // In particular, if any generation might iterate over the oops
417 // in other generations, it should call this method.
418 void save_marks();
419
420 // Apply "cur->do_oop" or "older->do_oop" to all the oops in objects
421 // allocated since the last call to save_marks in generations at or above
422 // "level". The "cur" closure is
423 // applied to references in the generation at "level", and the "older"
424 // closure to older generations.
425 #define GCH_SINCE_SAVE_MARKS_ITERATE_DECL(OopClosureType, nv_suffix) \
426 void oop_since_save_marks_iterate(int level, \
427 OopClosureType* cur, \
428 OopClosureType* older);
429
430 ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DECL)
431
432 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DECL
433
434 // Returns "true" iff no allocations have occurred in any generation at
435 // "level" or above since the last
436 // call to "save_marks".
437 bool no_allocs_since_save_marks(int level);
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 // Assumes a 2-generation system; the first disjunct remembers if an
445 // incremental collection failed, even when we thought (second disjunct)
446 // that it would not.
447 assert(heap()->collector_policy()->is_generation_policy(),
448 "the following definition may not be suitable for an n(>2)-generation system");
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 private:
474 // Accessor for memory state verification support
475 NOT_PRODUCT(
476 static size_t skip_header_HeapWords() { return _skip_header_HeapWords; }
477 )
478
479 // Override
480 void check_for_non_bad_heap_word_value(HeapWord* addr,
481 size_t size) PRODUCT_RETURN;
482
483 // For use by mark-sweep. As implemented, mark-sweep-compact is global
484 // in an essential way: compaction is performed across generations, by
485 // iterating over spaces.
486 void prepare_for_compaction();
487
488 // Perform a full collection of the first max_level+1 generations.
489 // This is the low level interface used by the public versions of
490 // collect() and collect_locked(). Caller holds the Heap_lock on entry.
491 void collect_locked(GCCause::Cause cause, int max_level);
492
493 // Returns success or failure.
494 bool create_cms_collector();
495
496 // In support of ExplicitGCInvokesConcurrent functionality
497 bool should_do_concurrent_full_gc(GCCause::Cause cause);
498 void collect_mostly_concurrent(GCCause::Cause cause);
499
500 // Save the tops of the spaces in all generations
501 void record_gen_tops_before_GC() PRODUCT_RETURN;
502
503 protected:
504 void gc_prologue(bool full);
505 void gc_epilogue(bool full);
506 };
507
508 #endif // SHARE_VM_MEMORY_GENCOLLECTEDHEAP_HPP