1 /*
2 * Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved.
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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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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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 StrongRootsScope;
34 class SubTasksDone;
35 class WorkGang;
36
37 // The set of potentially parallel tasks in root scanning.
38 enum GCH_strong_roots_tasks {
39 GCH_PS_Universe_oops_do,
40 GCH_PS_JNIHandles_oops_do,
41 GCH_PS_ObjectSynchronizer_oops_do,
42 GCH_PS_FlatProfiler_oops_do,
43 GCH_PS_Management_oops_do,
44 GCH_PS_SystemDictionary_oops_do,
45 GCH_PS_ClassLoaderDataGraph_oops_do,
46 GCH_PS_jvmti_oops_do,
47 GCH_PS_CodeCache_oops_do,
48 GCH_PS_aot_oops_do,
49 GCH_PS_younger_gens,
50 // Leave this one last.
51 GCH_PS_NumElements
52 };
53
54 // A "GenCollectedHeap" is a CollectedHeap that uses generational
55 // collection. It has two generations, young and old.
56 class GenCollectedHeap : public CollectedHeap {
57 friend class GenCollectorPolicy;
58 friend class Generation;
59 friend class DefNewGeneration;
60 friend class TenuredGeneration;
61 friend class ConcurrentMarkSweepGeneration;
62 friend class CMSCollector;
63 friend class GenMarkSweep;
64 friend class VM_GenCollectForAllocation;
65 friend class VM_GenCollectFull;
66 friend class VM_GenCollectFullConcurrent;
67 friend class VM_GC_HeapInspection;
68 friend class VM_HeapDumper;
69 friend class HeapInspection;
70 friend class GCCauseSetter;
71 friend class VMStructs;
72 public:
73 friend class VM_PopulateDumpSharedSpace;
74
75 enum GenerationType {
76 YoungGen,
77 OldGen
78 };
79
80 private:
81 Generation* _young_gen;
82 Generation* _old_gen;
83
84 // The singleton CardTable Remembered Set.
85 CardTableRS* _rem_set;
86
87 // The generational collector policy.
88 GenCollectorPolicy* _gen_policy;
89
90 // Indicates that the most recent previous incremental collection failed.
91 // The flag is cleared when an action is taken that might clear the
92 // condition that caused that incremental collection to fail.
93 bool _incremental_collection_failed;
94
95 // In support of ExplicitGCInvokesConcurrent functionality
96 unsigned int _full_collections_completed;
97
98 // Collects the given generation.
99 void collect_generation(Generation* gen, bool full, size_t size, bool is_tlab,
100 bool run_verification, bool clear_soft_refs,
101 bool restore_marks_for_biased_locking);
102
103 protected:
104 // Data structure for claiming the (potentially) parallel tasks in
105 // (gen-specific) roots processing.
106 SubTasksDone* _process_strong_tasks;
107
108 // Helper functions for allocation
109 HeapWord* attempt_allocation(size_t size,
110 bool is_tlab,
111 bool first_only);
112
113 // Helper function for two callbacks below.
114 // Considers collection of the first max_level+1 generations.
115 void do_collection(bool full,
116 bool clear_all_soft_refs,
117 size_t size,
118 bool is_tlab,
119 GenerationType max_generation);
120
121 // Callback from VM_GenCollectForAllocation operation.
122 // This function does everything necessary/possible to satisfy an
123 // allocation request that failed in the youngest generation that should
124 // have handled it (including collection, expansion, etc.)
125 HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab);
126
127 // Callback from VM_GenCollectFull operation.
128 // Perform a full collection of the first max_level+1 generations.
129 virtual void do_full_collection(bool clear_all_soft_refs);
130 void do_full_collection(bool clear_all_soft_refs, GenerationType max_generation);
131
132 // Does the "cause" of GC indicate that
133 // we absolutely __must__ clear soft refs?
134 bool must_clear_all_soft_refs();
135
136 public:
137 GenCollectedHeap(GenCollectorPolicy *policy);
138
139 // Returns JNI_OK on success
140 virtual jint initialize();
141
142 // Reserve aligned space for the heap as needed by the contained generations.
143 char* allocate(size_t alignment, ReservedSpace* heap_rs);
144
145 // Does operations required after initialization has been done.
146 void post_initialize();
147
148 #ifdef ASSERT
149 virtual void check_gen_kinds();
150 #endif
151
152 // Initialize ("weak") refs processing support
153 virtual void ref_processing_init();
154
155 virtual Name kind() const {
156 return CollectedHeap::GenCollectedHeap;
157 }
158
159 virtual const char* name() const {
160 return "Serial";
161 }
162
163 Generation* young_gen() const { return _young_gen; }
164 Generation* old_gen() const { return _old_gen; }
165
166 bool is_young_gen(const Generation* gen) const { return gen == _young_gen; }
167 bool is_old_gen(const Generation* gen) const { return gen == _old_gen; }
168
169 // The generational collector policy.
170 GenCollectorPolicy* gen_policy() const { return _gen_policy; }
171
172 virtual CollectorPolicy* collector_policy() const { return gen_policy(); }
173
174 // Adaptive size policy
175 virtual AdaptiveSizePolicy* size_policy() {
176 return gen_policy()->size_policy();
177 }
178
179 // Return the (conservative) maximum heap alignment
180 static size_t conservative_max_heap_alignment() {
181 return Generation::GenGrain;
182 }
183
184 size_t capacity() const;
185 size_t used() const;
186
187 // Save the "used_region" for both generations.
188 void save_used_regions();
189
190 size_t max_capacity() const;
191
192 HeapWord* mem_allocate(size_t size, bool* gc_overhead_limit_was_exceeded);
193
194 // We may support a shared contiguous allocation area, if the youngest
195 // generation does.
196 bool supports_inline_contig_alloc() const;
197 HeapWord* volatile* top_addr() const;
198 HeapWord** end_addr() const;
199
200 // Perform a full collection of the heap; intended for use in implementing
201 // "System.gc". This implies as full a collection as the CollectedHeap
202 // supports. Caller does not hold the Heap_lock on entry.
203 virtual void collect(GCCause::Cause cause);
204
205 // The same as above but assume that the caller holds the Heap_lock.
206 void collect_locked(GCCause::Cause cause);
207
208 // Perform a full collection of generations up to and including max_generation.
209 // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry.
210 void collect(GCCause::Cause cause, GenerationType max_generation);
211
212 // Returns "TRUE" iff "p" points into the committed areas of the heap.
213 // The methods is_in(), is_in_closed_subset() and is_in_youngest() may
214 // be expensive to compute in general, so, to prevent
215 // their inadvertent use in product jvm's, we restrict their use to
216 // assertion checking or verification only.
217 bool is_in(const void* p) const;
218
219 // override
220 virtual bool is_in_closed_subset(const void* p) const {
221 return is_in(p);
222 }
223
224 // Returns true if the reference is to an object in the reserved space
225 // for the young generation.
226 // Assumes the the young gen address range is less than that of the old gen.
227 bool is_in_young(oop p);
228
229 #ifdef ASSERT
230 bool is_in_partial_collection(const void* p);
231 #endif
232
233 virtual bool is_scavengable(const void* addr) {
234 return is_in_young((oop)addr);
235 }
236
237 // Iteration functions.
238 void oop_iterate_no_header(OopClosure* cl);
239 void oop_iterate(ExtendedOopClosure* cl);
240 void object_iterate(ObjectClosure* cl);
241 void safe_object_iterate(ObjectClosure* cl);
242 Space* space_containing(const void* addr) const;
243
244 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
245 // each address in the (reserved) heap is a member of exactly
246 // one block. The defining characteristic of a block is that it is
247 // possible to find its size, and thus to progress forward to the next
248 // block. (Blocks may be of different sizes.) Thus, blocks may
249 // represent Java objects, or they might be free blocks in a
250 // free-list-based heap (or subheap), as long as the two kinds are
251 // distinguishable and the size of each is determinable.
252
253 // Returns the address of the start of the "block" that contains the
254 // address "addr". We say "blocks" instead of "object" since some heaps
255 // may not pack objects densely; a chunk may either be an object or a
256 // non-object.
257 virtual HeapWord* block_start(const void* addr) const;
258
259 // Requires "addr" to be the start of a chunk, and returns its size.
260 // "addr + size" is required to be the start of a new chunk, or the end
261 // of the active area of the heap. Assumes (and verifies in non-product
262 // builds) that addr is in the allocated part of the heap and is
263 // the start of a chunk.
264 virtual size_t block_size(const HeapWord* addr) const;
265
266 // Requires "addr" to be the start of a block, and returns "TRUE" iff
267 // the block is an object. Assumes (and verifies in non-product
268 // builds) that addr is in the allocated part of the heap and is
269 // the start of a chunk.
270 virtual bool block_is_obj(const HeapWord* addr) const;
271
272 // Section on TLAB's.
273 virtual bool supports_tlab_allocation() const;
274 virtual size_t tlab_capacity(Thread* thr) const;
275 virtual size_t tlab_used(Thread* thr) const;
276 virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
277 virtual HeapWord* allocate_new_tlab(size_t size);
278
279 // Can a compiler initialize a new object without store barriers?
280 // This permission only extends from the creation of a new object
281 // via a TLAB up to the first subsequent safepoint.
282 virtual bool can_elide_tlab_store_barriers() const {
283 return true;
284 }
285
286 virtual bool card_mark_must_follow_store() const {
287 return false;
288 }
289
290 // We don't need barriers for stores to objects in the
291 // young gen and, a fortiori, for initializing stores to
292 // objects therein. This applies to DefNew+Tenured and ParNew+CMS
293 // only and may need to be re-examined in case other
294 // kinds of collectors are implemented in the future.
295 virtual bool can_elide_initializing_store_barrier(oop new_obj) {
296 return is_in_young(new_obj);
297 }
298
299 // The "requestor" generation is performing some garbage collection
300 // action for which it would be useful to have scratch space. The
301 // requestor promises to allocate no more than "max_alloc_words" in any
302 // older generation (via promotion say.) Any blocks of space that can
303 // be provided are returned as a list of ScratchBlocks, sorted by
304 // decreasing size.
305 ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words);
306 // Allow each generation to reset any scratch space that it has
307 // contributed as it needs.
308 void release_scratch();
309
310 // Ensure parsability: override
311 virtual void ensure_parsability(bool retire_tlabs);
312
313 // Time in ms since the longest time a collector ran in
314 // in any generation.
315 virtual jlong millis_since_last_gc();
316
317 // Total number of full collections completed.
318 unsigned int total_full_collections_completed() {
319 assert(_full_collections_completed <= _total_full_collections,
320 "Can't complete more collections than were started");
321 return _full_collections_completed;
322 }
323
324 // Update above counter, as appropriate, at the end of a stop-world GC cycle
325 unsigned int update_full_collections_completed();
326 // Update above counter, as appropriate, at the end of a concurrent GC cycle
327 unsigned int update_full_collections_completed(unsigned int count);
328
329 // Update "time of last gc" for all generations to "now".
330 void update_time_of_last_gc(jlong now) {
331 _young_gen->update_time_of_last_gc(now);
332 _old_gen->update_time_of_last_gc(now);
333 }
334
335 // Update the gc statistics for each generation.
336 void update_gc_stats(Generation* current_generation, bool full) {
337 _old_gen->update_gc_stats(current_generation, full);
338 }
339
340 bool no_gc_in_progress() { return !is_gc_active(); }
341
342 // Override.
343 void prepare_for_verify();
344
345 // Override.
346 void verify(VerifyOption option);
347
348 // Override.
349 virtual void print_on(outputStream* st) const;
350 virtual void print_gc_threads_on(outputStream* st) const;
351 virtual void gc_threads_do(ThreadClosure* tc) const;
352 virtual void print_tracing_info() const;
353
354 void print_heap_change(size_t young_prev_used, size_t old_prev_used) const;
355
356 // The functions below are helper functions that a subclass of
357 // "CollectedHeap" can use in the implementation of its virtual
358 // functions.
359
360 class GenClosure : public StackObj {
361 public:
362 virtual void do_generation(Generation* gen) = 0;
363 };
364
365 // Apply "cl.do_generation" to all generations in the heap
366 // If "old_to_young" determines the order.
367 void generation_iterate(GenClosure* cl, bool old_to_young);
368
369 // Return "true" if all generations have reached the
370 // maximal committed limit that they can reach, without a garbage
371 // collection.
372 virtual bool is_maximal_no_gc() const;
373
374 // This function returns the CardTableRS object that allows us to scan
375 // generations in a fully generational heap.
376 CardTableRS* rem_set() { return _rem_set; }
377
378 // Convenience function to be used in situations where the heap type can be
379 // asserted to be this type.
380 static GenCollectedHeap* heap();
381
382 // The ScanningOption determines which of the roots
383 // the closure is applied to:
384 // "SO_None" does none;
385 enum ScanningOption {
386 SO_None = 0x0,
387 SO_AllCodeCache = 0x8,
388 SO_ScavengeCodeCache = 0x10
389 };
390
391 protected:
392 void process_roots(StrongRootsScope* scope,
393 ScanningOption so,
394 OopClosure* strong_roots,
395 OopClosure* weak_roots,
396 CLDClosure* strong_cld_closure,
397 CLDClosure* weak_cld_closure,
398 CodeBlobToOopClosure* code_roots);
399
400 void process_string_table_roots(StrongRootsScope* scope,
401 OopClosure* root_closure);
402
403 public:
404 void young_process_roots(StrongRootsScope* scope,
405 OopsInGenClosure* root_closure,
406 OopsInGenClosure* old_gen_closure,
407 CLDClosure* cld_closure);
408
409 void full_process_roots(StrongRootsScope* scope,
410 bool is_adjust_phase,
411 ScanningOption so,
412 bool only_strong_roots,
413 OopsInGenClosure* root_closure,
414 CLDClosure* cld_closure);
415
416 // Apply "root_closure" to all the weak roots of the system.
417 // These include JNI weak roots, string table,
418 // and referents of reachable weak refs.
419 void gen_process_weak_roots(OopClosure* root_closure);
420
421 // Set the saved marks of generations, if that makes sense.
422 // In particular, if any generation might iterate over the oops
423 // in other generations, it should call this method.
424 void save_marks();
425
426 // Apply "cur->do_oop" or "older->do_oop" to all the oops in objects
427 // allocated since the last call to save_marks in generations at or above
428 // "level". The "cur" closure is
429 // applied to references in the generation at "level", and the "older"
430 // closure to older generations.
431 #define GCH_SINCE_SAVE_MARKS_ITERATE_DECL(OopClosureType, nv_suffix) \
432 void oop_since_save_marks_iterate(GenerationType start_gen, \
433 OopClosureType* cur, \
434 OopClosureType* older);
435
436 ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DECL)
437
438 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DECL
439
440 // Returns "true" iff no allocations have occurred since the last
441 // call to "save_marks".
442 bool no_allocs_since_save_marks();
443
444 // Returns true if an incremental collection is likely to fail.
445 // We optionally consult the young gen, if asked to do so;
446 // otherwise we base our answer on whether the previous incremental
447 // collection attempt failed with no corrective action as of yet.
448 bool incremental_collection_will_fail(bool consult_young) {
449 // The first disjunct remembers if an incremental collection failed, even
450 // when we thought (second disjunct) that it would not.
451 return incremental_collection_failed() ||
452 (consult_young && !_young_gen->collection_attempt_is_safe());
453 }
454
455 // If a generation bails out of an incremental collection,
456 // it sets this flag.
457 bool incremental_collection_failed() const {
458 return _incremental_collection_failed;
459 }
460 void set_incremental_collection_failed() {
461 _incremental_collection_failed = true;
462 }
463 void clear_incremental_collection_failed() {
464 _incremental_collection_failed = false;
465 }
466
467 // Promotion of obj into gen failed. Try to promote obj to higher
468 // gens in ascending order; return the new location of obj if successful.
469 // Otherwise, try expand-and-allocate for obj in both the young and old
470 // generation; return the new location of obj if successful. Otherwise, return NULL.
471 oop handle_failed_promotion(Generation* old_gen,
472 oop obj,
473 size_t obj_size);
474
475
476 protected:
477 // In block contents verification, the number of header words to skip
478 NOT_PRODUCT(static size_t _skip_header_HeapWords;)
479
480 // Accessor for memory state verification support
481 NOT_PRODUCT(
482 static size_t skip_header_HeapWords() { return _skip_header_HeapWords; }
483 )
484
485 private:
486 // Override
487 void check_for_non_bad_heap_word_value(HeapWord* addr,
488 size_t size) PRODUCT_RETURN;
489
490 // For use by mark-sweep. As implemented, mark-sweep-compact is global
491 // in an essential way: compaction is performed across generations, by
492 // iterating over spaces.
493 void prepare_for_compaction();
494
495 // Perform a full collection of the generations up to and including max_generation.
496 // This is the low level interface used by the public versions of
497 // collect() and collect_locked(). Caller holds the Heap_lock on entry.
498 void collect_locked(GCCause::Cause cause, GenerationType max_generation);
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
509 #endif // SHARE_VM_GC_SHARED_GENCOLLECTEDHEAP_HPP