1 /*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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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 is represented with a sequence of Generation's.
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 enum SomeConstants {
55 max_gens = 10
56 };
57
58 friend class VM_PopulateDumpSharedSpace;
59
60 protected:
61 // Fields:
62 static GenCollectedHeap* _gch;
63
64 private:
65 int _n_gens;
66 Generation* _gens[max_gens];
67 GenerationSpec** _gen_specs;
68
69 // The generational collector policy.
70 GenCollectorPolicy* _gen_policy;
71
72 // Indicates that the most recent previous incremental collection failed.
73 // The flag is cleared when an action is taken that might clear the
74 // condition that caused that incremental collection to fail.
75 bool _incremental_collection_failed;
76
77 // In support of ExplicitGCInvokesConcurrent functionality
78 unsigned int _full_collections_completed;
79
80 // Data structure for claiming the (potentially) parallel tasks in
81 // (gen-specific) strong roots processing.
82 SubTasksDone* _gen_process_strong_tasks;
83 SubTasksDone* gen_process_strong_tasks() { return _gen_process_strong_tasks; }
84
85 // In block contents verification, the number of header words to skip
86 NOT_PRODUCT(static size_t _skip_header_HeapWords;)
87
88 protected:
89 // Helper functions for allocation
90 HeapWord* attempt_allocation(size_t size,
91 bool is_tlab,
92 bool first_only);
93
94 // Helper function for two callbacks below.
95 // Considers collection of the first max_level+1 generations.
96 void do_collection(bool full,
97 bool clear_all_soft_refs,
98 size_t size,
99 bool is_tlab,
100 int max_level);
101
102 // Callback from VM_GenCollectForAllocation operation.
103 // This function does everything necessary/possible to satisfy an
104 // allocation request that failed in the youngest generation that should
105 // have handled it (including collection, expansion, etc.)
106 HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab);
107
108 // Callback from VM_GenCollectFull operation.
109 // Perform a full collection of the first max_level+1 generations.
110 virtual void do_full_collection(bool clear_all_soft_refs);
111 void do_full_collection(bool clear_all_soft_refs, int max_level);
112
113 // Does the "cause" of GC indicate that
114 // we absolutely __must__ clear soft refs?
115 bool must_clear_all_soft_refs();
116
117 public:
118 GenCollectedHeap(GenCollectorPolicy *policy);
119
120 GCStats* gc_stats(int level) const;
121
122 // Returns JNI_OK on success
123 virtual jint initialize();
124 char* allocate(size_t alignment,
125 size_t* _total_reserved, int* _n_covered_regions,
126 ReservedSpace* heap_rs);
127
128 // Does operations required after initialization has been done.
129 void post_initialize();
130
131 // Initialize ("weak") refs processing support
132 virtual void ref_processing_init();
133
134 virtual CollectedHeap::Name kind() const {
135 return CollectedHeap::GenCollectedHeap;
136 }
137
138 // The generational collector policy.
139 GenCollectorPolicy* gen_policy() const { return _gen_policy; }
140 virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) gen_policy(); }
141
142 // Adaptive size policy
143 virtual AdaptiveSizePolicy* size_policy() {
144 return gen_policy()->size_policy();
145 }
146
147 // Return the (conservative) maximum heap alignment
148 static size_t conservative_max_heap_alignment() {
149 return Generation::GenGrain;
150 }
151
152 size_t capacity() const;
153 size_t used() const;
154
155 // Save the "used_region" for generations level and lower.
156 void save_used_regions(int level);
157
158 size_t max_capacity() const;
159
160 HeapWord* mem_allocate(size_t size,
161 bool* gc_overhead_limit_was_exceeded);
162
163 // We may support a shared contiguous allocation area, if the youngest
164 // generation does.
165 bool supports_inline_contig_alloc() const;
166 HeapWord** top_addr() const;
167 HeapWord** end_addr() const;
168
169 // Does this heap support heap inspection? (+PrintClassHistogram)
170 virtual bool supports_heap_inspection() const { return true; }
171
172 // Perform a full collection of the heap; intended for use in implementing
173 // "System.gc". This implies as full a collection as the CollectedHeap
174 // supports. Caller does not hold the Heap_lock on entry.
175 void collect(GCCause::Cause cause);
176
177 // The same as above but assume that the caller holds the Heap_lock.
178 void collect_locked(GCCause::Cause cause);
179
180 // Perform a full collection of the first max_level+1 generations.
181 // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry.
182 void collect(GCCause::Cause cause, int max_level);
183
184 // Returns "TRUE" iff "p" points into the committed areas of the heap.
185 // The methods is_in(), is_in_closed_subset() and is_in_youngest() may
186 // be expensive to compute in general, so, to prevent
187 // their inadvertent use in product jvm's, we restrict their use to
188 // assertion checking or verification only.
189 bool is_in(const void* p) const;
190
191 // override
192 bool is_in_closed_subset(const void* p) const {
193 if (UseConcMarkSweepGC) {
194 return is_in_reserved(p);
195 } else {
196 return is_in(p);
197 }
198 }
199
200 // Returns true if the reference is to an object in the reserved space
201 // for the young generation.
202 // Assumes the the young gen address range is less than that of the old gen.
203 bool is_in_young(oop p);
204
205 #ifdef ASSERT
206 virtual bool is_in_partial_collection(const void* p);
207 #endif
208
209 virtual bool is_scavengable(const void* addr) {
210 return is_in_young((oop)addr);
211 }
212
213 // Iteration functions.
214 void oop_iterate(ExtendedOopClosure* cl);
215 void object_iterate(ObjectClosure* cl);
216 void safe_object_iterate(ObjectClosure* cl);
217 Space* space_containing(const void* addr) const;
218
219 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
220 // each address in the (reserved) heap is a member of exactly
221 // one block. The defining characteristic of a block is that it is
222 // possible to find its size, and thus to progress forward to the next
223 // block. (Blocks may be of different sizes.) Thus, blocks may
224 // represent Java objects, or they might be free blocks in a
225 // free-list-based heap (or subheap), as long as the two kinds are
226 // distinguishable and the size of each is determinable.
227
228 // Returns the address of the start of the "block" that contains the
229 // address "addr". We say "blocks" instead of "object" since some heaps
230 // may not pack objects densely; a chunk may either be an object or a
231 // non-object.
232 virtual HeapWord* block_start(const void* addr) const;
233
234 // Requires "addr" to be the start of a chunk, and returns its size.
235 // "addr + size" is required to be the start of a new chunk, or the end
236 // of the active area of the heap. Assumes (and verifies in non-product
237 // builds) that addr is in the allocated part of the heap and is
238 // the start of a chunk.
239 virtual size_t block_size(const HeapWord* addr) const;
240
241 // Requires "addr" to be the start of a block, and returns "TRUE" iff
242 // the block is an object. 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 bool block_is_obj(const HeapWord* addr) const;
246
247 // Section on TLAB's.
248 virtual bool supports_tlab_allocation() const;
249 virtual size_t tlab_capacity(Thread* thr) const;
250 virtual size_t tlab_used(Thread* thr) const;
251 virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
252 virtual HeapWord* allocate_new_tlab(size_t size);
253
254 // Can a compiler initialize a new object without store barriers?
255 // This permission only extends from the creation of a new object
256 // via a TLAB up to the first subsequent safepoint.
257 virtual bool can_elide_tlab_store_barriers() const {
258 return true;
259 }
260
261 virtual bool card_mark_must_follow_store() const {
262 return UseConcMarkSweepGC;
263 }
264
265 // We don't need barriers for stores to objects in the
266 // young gen and, a fortiori, for initializing stores to
267 // objects therein. This applies to {DefNew,ParNew}+{Tenured,CMS}
268 // only and may need to be re-examined in case other
269 // kinds of collectors are implemented in the future.
270 virtual bool can_elide_initializing_store_barrier(oop new_obj) {
271 // We wanted to assert that:-
272 // assert(UseParNewGC || UseSerialGC || UseConcMarkSweepGC,
273 // "Check can_elide_initializing_store_barrier() for this collector");
274 // but unfortunately the flag UseSerialGC need not necessarily always
275 // be set when DefNew+Tenured are being used.
276 return is_in_young(new_obj);
277 }
278
279 // The "requestor" generation is performing some garbage collection
280 // action for which it would be useful to have scratch space. The
281 // requestor promises to allocate no more than "max_alloc_words" in any
282 // older generation (via promotion say.) Any blocks of space that can
283 // be provided are returned as a list of ScratchBlocks, sorted by
284 // decreasing size.
285 ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words);
286 // Allow each generation to reset any scratch space that it has
287 // contributed as it needs.
288 void release_scratch();
289
290 // Ensure parsability: override
291 virtual void ensure_parsability(bool retire_tlabs);
292
293 // Time in ms since the longest time a collector ran in
294 // in any generation.
295 virtual jlong millis_since_last_gc();
296
297 // Total number of full collections completed.
298 unsigned int total_full_collections_completed() {
299 assert(_full_collections_completed <= _total_full_collections,
300 "Can't complete more collections than were started");
301 return _full_collections_completed;
302 }
303
304 // Update above counter, as appropriate, at the end of a stop-world GC cycle
305 unsigned int update_full_collections_completed();
306 // Update above counter, as appropriate, at the end of a concurrent GC cycle
307 unsigned int update_full_collections_completed(unsigned int count);
308
309 // Update "time of last gc" for all constituent generations
310 // to "now".
311 void update_time_of_last_gc(jlong now) {
312 for (int i = 0; i < _n_gens; i++) {
313 _gens[i]->update_time_of_last_gc(now);
314 }
315 }
316
317 // Update the gc statistics for each generation.
318 // "level" is the level of the latest collection.
319 void update_gc_stats(int current_level, bool full) {
320 for (int i = 0; i < _n_gens; i++) {
321 _gens[i]->update_gc_stats(current_level, full);
322 }
323 }
324
325 // Override.
326 bool no_gc_in_progress() { return !is_gc_active(); }
327
328 // Override.
329 void prepare_for_verify();
330
331 // Override.
332 void verify(bool silent, VerifyOption option);
333
334 // Override.
335 virtual void print_on(outputStream* st) const;
336 virtual void print_gc_threads_on(outputStream* st) const;
337 virtual void gc_threads_do(ThreadClosure* tc) const;
338 virtual void print_tracing_info() const;
339 virtual void print_on_error(outputStream* st) const;
340
341 // PrintGC, PrintGCDetails support
342 void print_heap_change(size_t prev_used) const;
343
344 // The functions below are helper functions that a subclass of
345 // "CollectedHeap" can use in the implementation of its virtual
346 // functions.
347
348 class GenClosure : public StackObj {
349 public:
350 virtual void do_generation(Generation* gen) = 0;
351 };
352
353 // Apply "cl.do_generation" to all generations in the heap
354 // If "old_to_young" determines the order.
355 void generation_iterate(GenClosure* cl, bool old_to_young);
356
357 void space_iterate(SpaceClosure* cl);
358
359 // Return "true" if all generations have reached the
360 // maximal committed limit that they can reach, without a garbage
361 // collection.
362 virtual bool is_maximal_no_gc() const;
363
364 // Return the generation before "gen".
365 Generation* prev_gen(Generation* gen) const {
366 int l = gen->level();
367 guarantee(l > 0, "Out of bounds");
368 return _gens[l-1];
369 }
370
371 // Return the generation after "gen".
372 Generation* next_gen(Generation* gen) const {
373 int l = gen->level() + 1;
374 guarantee(l < _n_gens, "Out of bounds");
375 return _gens[l];
376 }
377
378 Generation* get_gen(int i) const {
379 guarantee(i >= 0 && i < _n_gens, "Out of bounds");
380 return _gens[i];
381 }
382
383 int n_gens() const {
384 assert(_n_gens == gen_policy()->number_of_generations(), "Sanity");
385 return _n_gens;
386 }
387
388 // Convenience function to be used in situations where the heap type can be
389 // asserted to be this type.
390 static GenCollectedHeap* heap();
391
392 void set_par_threads(uint t);
393
394 // Invoke the "do_oop" method of one of the closures "not_older_gens"
395 // or "older_gens" on root locations for the generation at
396 // "level". (The "older_gens" closure is used for scanning references
397 // from older generations; "not_older_gens" is used everywhere else.)
398 // If "younger_gens_as_roots" is false, younger generations are
399 // not scanned as roots; in this case, the caller must be arranging to
400 // scan the younger generations itself. (For example, a generation might
401 // explicitly mark reachable objects in younger generations, to avoid
402 // excess storage retention.)
403 // The "so" argument determines which of the roots
404 // the closure is applied to:
405 // "SO_None" does none;
406 // "SO_AllClasses" applies the closure to all entries in the SystemDictionary;
407 // "SO_SystemClasses" to all the "system" classes and loaders;
408 // "SO_Strings" applies the closure to all entries in the StringTable.
409 void gen_process_strong_roots(int level,
410 bool younger_gens_as_roots,
411 // The remaining arguments are in an order
412 // consistent with SharedHeap::process_strong_roots:
413 bool activate_scope,
414 SharedHeap::ScanningOption so,
415 OopsInGenClosure* not_older_gens,
416 OopsInGenClosure* older_gens,
417 KlassClosure* klass_closure);
418
419 // Apply "root_closure" to all the weak roots of the system.
420 // These include JNI weak roots, string table,
421 // and referents of reachable weak refs.
422 void gen_process_weak_roots(OopClosure* root_closure);
423
424 // Set the saved marks of generations, if that makes sense.
425 // In particular, if any generation might iterate over the oops
426 // in other generations, it should call this method.
427 void save_marks();
428
429 // Apply "cur->do_oop" or "older->do_oop" to all the oops in objects
430 // allocated since the last call to save_marks in generations at or above
431 // "level". The "cur" closure is
432 // applied to references in the generation at "level", and the "older"
433 // closure to older generations.
434 #define GCH_SINCE_SAVE_MARKS_ITERATE_DECL(OopClosureType, nv_suffix) \
435 void oop_since_save_marks_iterate(int level, \
436 OopClosureType* cur, \
437 OopClosureType* older);
438
439 ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DECL)
440
441 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DECL
442
443 // Returns "true" iff no allocations have occurred in any generation at
444 // "level" or above since the last
445 // call to "save_marks".
446 bool no_allocs_since_save_marks(int level);
447
448 // Returns true if an incremental collection is likely to fail.
449 // We optionally consult the young gen, if asked to do so;
450 // otherwise we base our answer on whether the previous incremental
451 // collection attempt failed with no corrective action as of yet.
452 bool incremental_collection_will_fail(bool consult_young) {
453 // Assumes a 2-generation system; the first disjunct remembers if an
454 // incremental collection failed, even when we thought (second disjunct)
455 // that it would not.
456 assert(heap()->collector_policy()->is_generation_policy(),
457 "the following definition may not be suitable for an n(>2)-generation system");
458 return incremental_collection_failed() ||
459 (consult_young && !get_gen(0)->collection_attempt_is_safe());
460 }
461
462 // If a generation bails out of an incremental collection,
463 // it sets this flag.
464 bool incremental_collection_failed() const {
465 return _incremental_collection_failed;
466 }
467 void set_incremental_collection_failed() {
468 _incremental_collection_failed = true;
469 }
470 void clear_incremental_collection_failed() {
471 _incremental_collection_failed = false;
472 }
473
474 // Promotion of obj into gen failed. Try to promote obj to higher
475 // gens in ascending order; return the new location of obj if successful.
476 // Otherwise, try expand-and-allocate for obj in both the young and old
477 // generation; return the new location of obj if successful. Otherwise, return NULL.
478 oop handle_failed_promotion(Generation* old_gen,
479 oop obj,
480 size_t obj_size);
481
482 private:
483 // Accessor for memory state verification support
484 NOT_PRODUCT(
485 static size_t skip_header_HeapWords() { return _skip_header_HeapWords; }
486 )
487
488 // Override
489 void check_for_non_bad_heap_word_value(HeapWord* addr,
490 size_t size) PRODUCT_RETURN;
491
492 // For use by mark-sweep. As implemented, mark-sweep-compact is global
493 // in an essential way: compaction is performed across generations, by
494 // iterating over spaces.
495 void prepare_for_compaction();
496
497 // Perform a full collection of the first max_level+1 generations.
498 // This is the low level interface used by the public versions of
499 // collect() and collect_locked(). Caller holds the Heap_lock on entry.
500 void collect_locked(GCCause::Cause cause, int max_level);
501
502 // Returns success or failure.
503 bool create_cms_collector();
504
505 // In support of ExplicitGCInvokesConcurrent functionality
506 bool should_do_concurrent_full_gc(GCCause::Cause cause);
507 void collect_mostly_concurrent(GCCause::Cause cause);
508
509 // Save the tops of the spaces in all generations
510 void record_gen_tops_before_GC() PRODUCT_RETURN;
511
512 protected:
513 virtual void gc_prologue(bool full);
514 virtual void gc_epilogue(bool full);
515 };
516
517 #endif // SHARE_VM_MEMORY_GENCOLLECTEDHEAP_HPP