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 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_GenCollectForPermanentAllocation;
47 friend class VM_GenCollectFull;
48 friend class VM_GenCollectFullConcurrent;
49 friend class VM_GC_HeapInspection;
50 friend class VM_HeapDumper;
51 friend class HeapInspection;
52 friend class GCCauseSetter;
53 friend class VMStructs;
54 public:
55 enum SomeConstants {
56 max_gens = 10
57 };
58
59 friend class VM_PopulateDumpSharedSpace;
60
61 protected:
62 // Fields:
63 static GenCollectedHeap* _gch;
64
65 private:
66 int _n_gens;
67 Generation* _gens[max_gens];
68 GenerationSpec** _gen_specs;
69
70 // The generational collector policy.
71 GenCollectorPolicy* _gen_policy;
72
73 // If a generation would bail out of an incremental collection,
74 // it sets this flag. If the flag is set, satisfy_failed_allocation
75 // will attempt allocating in all generations before doing a full GC.
76 bool _incremental_collection_will_fail;
77 bool _last_incremental_collection_failed;
78
79 // In support of ExplicitGCInvokesConcurrent functionality
80 unsigned int _full_collections_completed;
81
82 // Data structure for claiming the (potentially) parallel tasks in
83 // (gen-specific) strong roots processing.
84 SubTasksDone* _gen_process_strong_tasks;
85 SubTasksDone* gen_process_strong_tasks() { return _gen_process_strong_tasks; }
86
87 // In block contents verification, the number of header words to skip
88 NOT_PRODUCT(static size_t _skip_header_HeapWords;)
89
90 // GC is not allowed during the dump of the shared classes. Keep track
91 // of this in order to provide an reasonable error message when terminating.
92 bool _preloading_shared_classes;
93
94 protected:
95 // Directs each generation up to and including "collectedGen" to recompute
96 // its desired size.
97 void compute_new_generation_sizes(int collectedGen);
98
99 // Helper functions for allocation
100 HeapWord* attempt_allocation(size_t size,
101 bool is_tlab,
102 bool first_only);
103
104 // Helper function for two callbacks below.
105 // Considers collection of the first max_level+1 generations.
106 void do_collection(bool full,
107 bool clear_all_soft_refs,
108 size_t size,
109 bool is_tlab,
110 int max_level);
111
112 // Callback from VM_GenCollectForAllocation operation.
113 // This function does everything necessary/possible to satisfy an
114 // allocation request that failed in the youngest generation that should
115 // have handled it (including collection, expansion, etc.)
116 HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab);
117
118 // Callback from VM_GenCollectFull operation.
119 // Perform a full collection of the first max_level+1 generations.
120 void do_full_collection(bool clear_all_soft_refs, int max_level);
121
122 // Does the "cause" of GC indicate that
123 // we absolutely __must__ clear soft refs?
124 bool must_clear_all_soft_refs();
125
126 public:
127 GenCollectedHeap(GenCollectorPolicy *policy);
128
129 GCStats* gc_stats(int level) const;
130
131 // Returns JNI_OK on success
132 virtual jint initialize();
133 char* allocate(size_t alignment, PermanentGenerationSpec* perm_gen_spec,
134 size_t* _total_reserved, int* _n_covered_regions,
135 ReservedSpace* heap_rs);
136
137 // Does operations required after initialization has been done.
138 void post_initialize();
139
140 // Initialize ("weak") refs processing support
141 virtual void ref_processing_init();
142
143 virtual CollectedHeap::Name kind() const {
144 return CollectedHeap::GenCollectedHeap;
145 }
146
147 // The generational collector policy.
148 GenCollectorPolicy* gen_policy() const { return _gen_policy; }
149
150 // Adaptive size policy
151 virtual AdaptiveSizePolicy* size_policy() {
152 return gen_policy()->size_policy();
153 }
154
155 size_t capacity() const;
156 size_t used() const;
157
158 // Save the "used_region" for generations level and lower,
159 // and, if perm is true, for perm gen.
160 void save_used_regions(int level, bool perm);
161
162 size_t max_capacity() const;
163
164 HeapWord* mem_allocate(size_t size,
165 bool is_large_noref,
166 bool is_tlab,
167 bool* gc_overhead_limit_was_exceeded);
168
169 // We may support a shared contiguous allocation area, if the youngest
170 // generation does.
171 bool supports_inline_contig_alloc() const;
172 HeapWord** top_addr() const;
173 HeapWord** end_addr() const;
174
175 // Return an estimate of the maximum allocation that could be performed
176 // without triggering any collection activity. In a generational
177 // collector, for example, this is probably the largest allocation that
178 // could be supported in the youngest generation. It is "unsafe" because
179 // no locks are taken; the result should be treated as an approximation,
180 // not a guarantee.
181 size_t unsafe_max_alloc();
182
183 // Does this heap support heap inspection? (+PrintClassHistogram)
184 virtual bool supports_heap_inspection() const { return true; }
185
186 // Perform a full collection of the heap; intended for use in implementing
187 // "System.gc". This implies as full a collection as the CollectedHeap
188 // supports. Caller does not hold the Heap_lock on entry.
189 void collect(GCCause::Cause cause);
190
191 // This interface assumes that it's being called by the
192 // vm thread. It collects the heap assuming that the
193 // heap lock is already held and that we are executing in
194 // the context of the vm thread.
195 void collect_as_vm_thread(GCCause::Cause cause);
196
197 // The same as above but assume that the caller holds the Heap_lock.
198 void collect_locked(GCCause::Cause cause);
199
200 // Perform a full collection of the first max_level+1 generations.
201 // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry.
202 void collect(GCCause::Cause cause, int max_level);
203
204 // Returns "TRUE" iff "p" points into the allocated area of the heap.
205 // The methods is_in(), is_in_closed_subset() and is_in_youngest() may
206 // be expensive to compute in general, so, to prevent
207 // their inadvertent use in product jvm's, we restrict their use to
208 // assertion checking or verification only.
209 bool is_in(const void* p) const;
210
211 // override
212 bool is_in_closed_subset(const void* p) const {
213 if (UseConcMarkSweepGC) {
214 return is_in_reserved(p);
215 } else {
216 return is_in(p);
217 }
218 }
219
220 // Returns "TRUE" iff "p" points into the youngest generation.
221 bool is_in_youngest(void* p);
222
223 // Iteration functions.
224 void oop_iterate(OopClosure* cl);
225 void oop_iterate(MemRegion mr, OopClosure* cl);
226 void object_iterate(ObjectClosure* cl);
227 void safe_object_iterate(ObjectClosure* cl);
228 void object_iterate_since_last_GC(ObjectClosure* cl);
229 Space* space_containing(const void* addr) const;
230
231 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
232 // each address in the (reserved) heap is a member of exactly
233 // one block. The defining characteristic of a block is that it is
234 // possible to find its size, and thus to progress forward to the next
235 // block. (Blocks may be of different sizes.) Thus, blocks may
236 // represent Java objects, or they might be free blocks in a
237 // free-list-based heap (or subheap), as long as the two kinds are
238 // distinguishable and the size of each is determinable.
239
240 // Returns the address of the start of the "block" that contains the
241 // address "addr". We say "blocks" instead of "object" since some heaps
242 // may not pack objects densely; a chunk may either be an object or a
243 // non-object.
244 virtual HeapWord* block_start(const void* addr) const;
245
246 // Requires "addr" to be the start of a chunk, and returns its size.
247 // "addr + size" is required to be the start of a new chunk, or the end
248 // of the active area of the heap. 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 size_t block_size(const HeapWord* addr) const;
252
253 // Requires "addr" to be the start of a block, and returns "TRUE" iff
254 // the block is an object. Assumes (and verifies in non-product
255 // builds) that addr is in the allocated part of the heap and is
256 // the start of a chunk.
257 virtual bool block_is_obj(const HeapWord* addr) const;
258
259 // Section on TLAB's.
260 virtual bool supports_tlab_allocation() const;
261 virtual size_t tlab_capacity(Thread* thr) const;
262 virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
263 virtual HeapWord* allocate_new_tlab(size_t size);
264
265 // Can a compiler initialize a new object without store barriers?
266 // This permission only extends from the creation of a new object
267 // via a TLAB up to the first subsequent safepoint.
268 virtual bool can_elide_tlab_store_barriers() const {
269 return true;
270 }
271
272 virtual bool card_mark_must_follow_store() const {
273 return UseConcMarkSweepGC;
274 }
275
276 // We don't need barriers for stores to objects in the
277 // young gen and, a fortiori, for initializing stores to
278 // objects therein. This applies to {DefNew,ParNew}+{Tenured,CMS}
279 // only and may need to be re-examined in case other
280 // kinds of collectors are implemented in the future.
281 virtual bool can_elide_initializing_store_barrier(oop new_obj) {
282 // We wanted to assert that:-
283 // assert(UseParNewGC || UseSerialGC || UseConcMarkSweepGC,
284 // "Check can_elide_initializing_store_barrier() for this collector");
285 // but unfortunately the flag UseSerialGC need not necessarily always
286 // be set when DefNew+Tenured are being used.
287 return is_in_youngest((void*)new_obj);
288 }
289
290 // Can a compiler elide a store barrier when it writes
291 // a permanent oop into the heap? Applies when the compiler
292 // is storing x to the heap, where x->is_perm() is true.
293 virtual bool can_elide_permanent_oop_store_barriers() const {
294 // CMS needs to see all, even intra-generational, ref updates.
295 return !UseConcMarkSweepGC;
296 }
297
298 // The "requestor" generation is performing some garbage collection
299 // action for which it would be useful to have scratch space. The
300 // requestor promises to allocate no more than "max_alloc_words" in any
301 // older generation (via promotion say.) Any blocks of space that can
302 // be provided are returned as a list of ScratchBlocks, sorted by
303 // decreasing size.
304 ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words);
305 // Allow each generation to reset any scratch space that it has
306 // contributed as it needs.
307 void release_scratch();
308
309 size_t large_typearray_limit();
310
311 // Ensure parsability: override
312 virtual void ensure_parsability(bool retire_tlabs);
313
314 // Time in ms since the longest time a collector ran in
315 // in any generation.
316 virtual jlong millis_since_last_gc();
317
318 // Total number of full collections completed.
319 unsigned int total_full_collections_completed() {
320 assert(_full_collections_completed <= _total_full_collections,
321 "Can't complete more collections than were started");
322 return _full_collections_completed;
323 }
324
325 // Update above counter, as appropriate, at the end of a stop-world GC cycle
326 unsigned int update_full_collections_completed();
327 // Update above counter, as appropriate, at the end of a concurrent GC cycle
328 unsigned int update_full_collections_completed(unsigned int count);
329
330 // Update "time of last gc" for all constituent generations
331 // to "now".
332 void update_time_of_last_gc(jlong now) {
333 for (int i = 0; i < _n_gens; i++) {
334 _gens[i]->update_time_of_last_gc(now);
335 }
336 perm_gen()->update_time_of_last_gc(now);
337 }
338
339 // Update the gc statistics for each generation.
340 // "level" is the level of the lastest collection
341 void update_gc_stats(int current_level, bool full) {
342 for (int i = 0; i < _n_gens; i++) {
343 _gens[i]->update_gc_stats(current_level, full);
344 }
345 perm_gen()->update_gc_stats(current_level, full);
346 }
347
348 // Override.
349 bool no_gc_in_progress() { return !is_gc_active(); }
350
351 // Override.
352 void prepare_for_verify();
353
354 // Override.
355 void verify(bool allow_dirty, bool silent, bool /* option */);
356
357 // Override.
358 void print() const;
359 void print_on(outputStream* st) const;
360 virtual void print_gc_threads_on(outputStream* st) const;
361 virtual void gc_threads_do(ThreadClosure* tc) const;
362 virtual void print_tracing_info() const;
363
364 // PrintGC, PrintGCDetails support
365 void print_heap_change(size_t prev_used) const;
366 void print_perm_heap_change(size_t perm_prev_used) const;
367
368 // The functions below are helper functions that a subclass of
369 // "CollectedHeap" can use in the implementation of its virtual
370 // functions.
371
372 class GenClosure : public StackObj {
373 public:
374 virtual void do_generation(Generation* gen) = 0;
375 };
376
377 // Apply "cl.do_generation" to all generations in the heap (not including
378 // the permanent generation). If "old_to_young" determines the order.
379 void generation_iterate(GenClosure* cl, bool old_to_young);
380
381 void space_iterate(SpaceClosure* cl);
382
383 // Return "true" if all generations (but perm) have reached the
384 // maximal committed limit that they can reach, without a garbage
385 // collection.
386 virtual bool is_maximal_no_gc() const;
387
388 // Return the generation before "gen", or else NULL.
389 Generation* prev_gen(Generation* gen) const {
390 int l = gen->level();
391 if (l == 0) return NULL;
392 else return _gens[l-1];
393 }
394
395 // Return the generation after "gen", or else NULL.
396 Generation* next_gen(Generation* gen) const {
397 int l = gen->level() + 1;
398 if (l == _n_gens) return NULL;
399 else return _gens[l];
400 }
401
402 Generation* get_gen(int i) const {
403 if (i >= 0 && i < _n_gens)
404 return _gens[i];
405 else
406 return NULL;
407 }
408
409 int n_gens() const {
410 assert(_n_gens == gen_policy()->number_of_generations(), "Sanity");
411 return _n_gens;
412 }
413
414 // Convenience function to be used in situations where the heap type can be
415 // asserted to be this type.
416 static GenCollectedHeap* heap();
417
418 void set_par_threads(int t);
419
420
421 // Invoke the "do_oop" method of one of the closures "not_older_gens"
422 // or "older_gens" on root locations for the generation at
423 // "level". (The "older_gens" closure is used for scanning references
424 // from older generations; "not_older_gens" is used everywhere else.)
425 // If "younger_gens_as_roots" is false, younger generations are
426 // not scanned as roots; in this case, the caller must be arranging to
427 // scan the younger generations itself. (For example, a generation might
428 // explicitly mark reachable objects in younger generations, to avoid
429 // excess storage retention.) If "collecting_perm_gen" is false, then
430 // roots that may only contain references to permGen objects are not
431 // scanned. The "so" argument determines which of the roots
432 // the closure is applied to:
433 // "SO_None" does none;
434 // "SO_AllClasses" applies the closure to all entries in the SystemDictionary;
435 // "SO_SystemClasses" to all the "system" classes and loaders;
436 // "SO_Symbols_and_Strings" applies the closure to all entries in
437 // SymbolsTable and StringTable.
438 void gen_process_strong_roots(int level,
439 bool younger_gens_as_roots,
440 // The remaining arguments are in an order
441 // consistent with SharedHeap::process_strong_roots:
442 bool activate_scope,
443 bool collecting_perm_gen,
444 SharedHeap::ScanningOption so,
445 OopsInGenClosure* not_older_gens,
446 bool do_code_roots,
447 OopsInGenClosure* older_gens);
448
449 // Apply "blk" to all the weak roots of the system. These include
450 // JNI weak roots, the code cache, system dictionary, symbol table,
451 // string table, and referents of reachable weak refs.
452 void gen_process_weak_roots(OopClosure* root_closure,
453 CodeBlobClosure* code_roots,
454 OopClosure* non_root_closure);
455
456 // Set the saved marks of generations, if that makes sense.
457 // In particular, if any generation might iterate over the oops
458 // in other generations, it should call this method.
459 void save_marks();
460
461 // Apply "cur->do_oop" or "older->do_oop" to all the oops in objects
462 // allocated since the last call to save_marks in generations at or above
463 // "level" (including the permanent generation.) The "cur" closure is
464 // applied to references in the generation at "level", and the "older"
465 // closure to older (and permanent) generations.
466 #define GCH_SINCE_SAVE_MARKS_ITERATE_DECL(OopClosureType, nv_suffix) \
467 void oop_since_save_marks_iterate(int level, \
468 OopClosureType* cur, \
469 OopClosureType* older);
470
471 ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DECL)
472
473 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DECL
474
475 // Returns "true" iff no allocations have occurred in any generation at
476 // "level" or above (including the permanent generation) since the last
477 // call to "save_marks".
478 bool no_allocs_since_save_marks(int level);
479
480 // If a generation bails out of an incremental collection,
481 // it sets this flag.
482 bool incremental_collection_will_fail() {
483 return _incremental_collection_will_fail;
484 }
485 void set_incremental_collection_will_fail() {
486 _incremental_collection_will_fail = true;
487 }
488 void clear_incremental_collection_will_fail() {
489 _incremental_collection_will_fail = false;
490 }
491
492 bool last_incremental_collection_failed() const {
493 return _last_incremental_collection_failed;
494 }
495 void set_last_incremental_collection_failed() {
496 _last_incremental_collection_failed = true;
497 }
498 void clear_last_incremental_collection_failed() {
499 _last_incremental_collection_failed = false;
500 }
501
502 // Promotion of obj into gen failed. Try to promote obj to higher non-perm
503 // gens in ascending order; return the new location of obj if successful.
504 // Otherwise, try expand-and-allocate for obj in each generation starting at
505 // gen; return the new location of obj if successful. Otherwise, return NULL.
506 oop handle_failed_promotion(Generation* gen,
507 oop obj,
508 size_t obj_size);
509
510 private:
511 // Accessor for memory state verification support
512 NOT_PRODUCT(
513 static size_t skip_header_HeapWords() { return _skip_header_HeapWords; }
514 )
515
516 // Override
517 void check_for_non_bad_heap_word_value(HeapWord* addr,
518 size_t size) PRODUCT_RETURN;
519
520 // For use by mark-sweep. As implemented, mark-sweep-compact is global
521 // in an essential way: compaction is performed across generations, by
522 // iterating over spaces.
523 void prepare_for_compaction();
524
525 // Perform a full collection of the first max_level+1 generations.
526 // This is the low level interface used by the public versions of
527 // collect() and collect_locked(). Caller holds the Heap_lock on entry.
528 void collect_locked(GCCause::Cause cause, int max_level);
529
530 // Returns success or failure.
531 bool create_cms_collector();
532
533 // In support of ExplicitGCInvokesConcurrent functionality
534 bool should_do_concurrent_full_gc(GCCause::Cause cause);
535 void collect_mostly_concurrent(GCCause::Cause cause);
536
537 // Save the tops of the spaces in all generations
538 void record_gen_tops_before_GC() PRODUCT_RETURN;
539
540 protected:
541 virtual void gc_prologue(bool full);
542 virtual void gc_epilogue(bool full);
543
544 public:
545 virtual void preload_and_dump(TRAPS) KERNEL_RETURN;
546 };
547
548 #endif // SHARE_VM_MEMORY_GENCOLLECTEDHEAP_HPP