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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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 // 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 enum GenerationType {
59 YoungGen,
60 OldGen
61 };
62
63 private:
64 Generation* _young_gen;
65 Generation* _old_gen;
66
67 // The singleton CardTable Remembered Set.
68 CardTableRS* _rem_set;
69
70 // The generational collector policy.
71 GenCollectorPolicy* _gen_policy;
72
73 // Indicates that the most recent previous incremental collection failed.
74 // The flag is cleared when an action is taken that might clear the
75 // condition that caused that incremental collection to fail.
76 bool _incremental_collection_failed;
77
78 // In support of ExplicitGCInvokesConcurrent functionality
79 unsigned int _full_collections_completed;
80
81 // Data structure for claiming the (potentially) parallel tasks in
82 // (gen-specific) roots processing.
83 SubTasksDone* _process_strong_tasks;
84
85 // Collects the given generation.
86 void collect_generation(Generation* gen, bool full, size_t size, bool is_tlab,
87 bool run_verification, bool clear_soft_refs,
88 bool restore_marks_for_biased_locking);
89
90 protected:
91 // In block contents verification, the number of header words to skip
92 NOT_PRODUCT(static size_t _skip_header_HeapWords;)
93
94 WorkGang* _workers;
95
96 protected:
97 // Helper functions for allocation
98 HeapWord* attempt_allocation(size_t size,
99 bool is_tlab,
100 bool first_only);
101
102 // Helper function for two callbacks below.
103 // Considers collection of the first max_level+1 generations.
104 void do_collection(bool full,
105 bool clear_all_soft_refs,
106 size_t size,
107 bool is_tlab,
108 GenerationType max_generation);
109
110 // Callback from VM_GenCollectForAllocation operation.
111 // This function does everything necessary/possible to satisfy an
112 // allocation request that failed in the youngest generation that should
113 // have handled it (including collection, expansion, etc.)
114 HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab);
115
116 // Callback from VM_GenCollectFull operation.
117 // Perform a full collection of the first max_level+1 generations.
118 virtual void do_full_collection(bool clear_all_soft_refs);
119 void do_full_collection(bool clear_all_soft_refs, GenerationType max_generation);
120
121 // Does the "cause" of GC indicate that
122 // we absolutely __must__ clear soft refs?
123 bool must_clear_all_soft_refs();
124
125 public:
126 GenCollectedHeap(GenCollectorPolicy *policy);
127
128 WorkGang* workers() const { return _workers; }
129
130 // Returns JNI_OK on success
131 virtual jint initialize();
132
133 // Reserve aligned space for the heap as needed by the contained generations.
134 char* allocate(size_t alignment, ReservedSpace* heap_rs);
135
136 // Does operations required after initialization has been done.
137 void post_initialize();
138
139 // Initialize ("weak") refs processing support
140 virtual void ref_processing_init();
141
142 virtual Name kind() const {
143 return CollectedHeap::GenCollectedHeap;
144 }
145
146 virtual const char* name() const {
147 if (UseConcMarkSweepGC) {
148 return "Concurrent Mark Sweep";
149 } else {
150 return "Serial";
151 }
152 }
153
154 Generation* young_gen() const { return _young_gen; }
155 Generation* old_gen() const { return _old_gen; }
156
157 bool is_young_gen(const Generation* gen) const { return gen == _young_gen; }
158 bool is_old_gen(const Generation* gen) const { return gen == _old_gen; }
159
160 // The generational collector policy.
161 GenCollectorPolicy* gen_policy() const { return _gen_policy; }
162
163 virtual CollectorPolicy* collector_policy() const { return gen_policy(); }
164
165 // Adaptive size policy
166 virtual AdaptiveSizePolicy* size_policy() {
167 return gen_policy()->size_policy();
168 }
169
170 // Return the (conservative) maximum heap alignment
171 static size_t conservative_max_heap_alignment() {
172 return Generation::GenGrain;
173 }
174
175 size_t capacity() const;
176 size_t used() const;
177
178 // Save the "used_region" for both generations.
179 void save_used_regions();
180
181 size_t max_capacity() const;
182
183 HeapWord* mem_allocate(size_t size, bool* gc_overhead_limit_was_exceeded);
184
185 // We may support a shared contiguous allocation area, if the youngest
186 // generation does.
187 bool supports_inline_contig_alloc() const;
188 HeapWord* volatile* top_addr() const;
189 HeapWord** end_addr() const;
190
191 // Perform a full collection of the heap; intended for use in implementing
192 // "System.gc". This implies as full a collection as the CollectedHeap
193 // supports. Caller does not hold the Heap_lock on entry.
194 virtual void collect(GCCause::Cause cause);
195
196 // The same as above but assume that the caller holds the Heap_lock.
197 void collect_locked(GCCause::Cause cause);
198
199 // Perform a full collection of generations up to and including max_generation.
200 // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry.
201 void collect(GCCause::Cause cause, GenerationType max_generation);
202
203 // Returns "TRUE" iff "p" points into the committed areas of the heap.
204 // The methods is_in(), is_in_closed_subset() and is_in_youngest() may
205 // be expensive to compute in general, so, to prevent
206 // their inadvertent use in product jvm's, we restrict their use to
207 // assertion checking or verification only.
208 bool is_in(const void* p) const;
209
210 // override
211 bool is_in_closed_subset(const void* p) const {
212 if (UseConcMarkSweepGC) {
213 return is_in_reserved(p);
214 } else {
215 return is_in(p);
216 }
217 }
218
219 // Returns true if the reference is to an object in the reserved space
220 // for the young generation.
221 // Assumes the the young gen address range is less than that of the old gen.
222 bool is_in_young(oop p);
223
224 #ifdef ASSERT
225 bool is_in_partial_collection(const void* p);
226 #endif
227
228 virtual bool is_scavengable(const void* addr) {
229 return is_in_young((oop)addr);
230 }
231
232 // Iteration functions.
233 void oop_iterate_no_header(OopClosure* cl);
234 void oop_iterate(ExtendedOopClosure* cl);
235 void object_iterate(ObjectClosure* cl);
236 void safe_object_iterate(ObjectClosure* cl);
237 Space* space_containing(const void* addr) const;
238
239 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
240 // each address in the (reserved) heap is a member of exactly
241 // one block. The defining characteristic of a block is that it is
242 // possible to find its size, and thus to progress forward to the next
243 // block. (Blocks may be of different sizes.) Thus, blocks may
244 // represent Java objects, or they might be free blocks in a
245 // free-list-based heap (or subheap), as long as the two kinds are
246 // distinguishable and the size of each is determinable.
247
248 // Returns the address of the start of the "block" that contains the
249 // address "addr". We say "blocks" instead of "object" since some heaps
250 // may not pack objects densely; a chunk may either be an object or a
251 // non-object.
252 virtual HeapWord* block_start(const void* addr) const;
253
254 // Requires "addr" to be the start of a chunk, and returns its size.
255 // "addr + size" is required to be the start of a new chunk, or the end
256 // of the active area of the heap. Assumes (and verifies in non-product
257 // builds) that addr is in the allocated part of the heap and is
258 // the start of a chunk.
259 virtual size_t block_size(const HeapWord* addr) const;
260
261 // Requires "addr" to be the start of a block, and returns "TRUE" iff
262 // the block is an object. Assumes (and verifies in non-product
263 // builds) that addr is in the allocated part of the heap and is
264 // the start of a chunk.
265 virtual bool block_is_obj(const HeapWord* addr) const;
266
267 // Section on TLAB's.
268 virtual bool supports_tlab_allocation() const;
269 virtual size_t tlab_capacity(Thread* thr) const;
270 virtual size_t tlab_used(Thread* thr) const;
271 virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
272 virtual HeapWord* allocate_new_tlab(size_t size);
273
274 // Can a compiler initialize a new object without store barriers?
275 // This permission only extends from the creation of a new object
276 // via a TLAB up to the first subsequent safepoint.
277 virtual bool can_elide_tlab_store_barriers() const {
278 return true;
279 }
280
281 virtual bool card_mark_must_follow_store() const {
282 return UseConcMarkSweepGC;
283 }
284
285 // We don't need barriers for stores to objects in the
286 // young gen and, a fortiori, for initializing stores to
287 // objects therein. This applies to DefNew+Tenured and ParNew+CMS
288 // only and may need to be re-examined in case other
289 // kinds of collectors are implemented in the future.
290 virtual bool can_elide_initializing_store_barrier(oop new_obj) {
291 return is_in_young(new_obj);
292 }
293
294 // The "requestor" generation is performing some garbage collection
295 // action for which it would be useful to have scratch space. The
296 // requestor promises to allocate no more than "max_alloc_words" in any
297 // older generation (via promotion say.) Any blocks of space that can
298 // be provided are returned as a list of ScratchBlocks, sorted by
299 // decreasing size.
300 ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words);
301 // Allow each generation to reset any scratch space that it has
302 // contributed as it needs.
303 void release_scratch();
304
305 // Ensure parsability: override
306 virtual void ensure_parsability(bool retire_tlabs);
307
308 // Time in ms since the longest time a collector ran in
309 // in any generation.
310 virtual jlong millis_since_last_gc();
311
312 // Total number of full collections completed.
313 unsigned int total_full_collections_completed() {
314 assert(_full_collections_completed <= _total_full_collections,
315 "Can't complete more collections than were started");
316 return _full_collections_completed;
317 }
318
319 // Update above counter, as appropriate, at the end of a stop-world GC cycle
320 unsigned int update_full_collections_completed();
321 // Update above counter, as appropriate, at the end of a concurrent GC cycle
322 unsigned int update_full_collections_completed(unsigned int count);
323
324 // Update "time of last gc" for all generations to "now".
325 void update_time_of_last_gc(jlong now) {
326 _young_gen->update_time_of_last_gc(now);
327 _old_gen->update_time_of_last_gc(now);
328 }
329
330 // Update the gc statistics for each generation.
331 void update_gc_stats(Generation* current_generation, bool full) {
332 _old_gen->update_gc_stats(current_generation, full);
333 }
334
335 bool no_gc_in_progress() { return !is_gc_active(); }
336
337 // Override.
338 void prepare_for_verify();
339
340 // Override.
341 void verify(VerifyOption option);
342
343 // Override.
344 virtual void print_on(outputStream* st) const;
345 virtual void print_gc_threads_on(outputStream* st) const;
346 virtual void gc_threads_do(ThreadClosure* tc) const;
347 virtual void print_tracing_info() const;
348 virtual void print_on_error(outputStream* st) const;
349
350 void print_heap_change(size_t young_prev_used, size_t old_prev_used) const;
351
352 // The functions below are helper functions that a subclass of
353 // "CollectedHeap" can use in the implementation of its virtual
354 // functions.
355
356 class GenClosure : public StackObj {
357 public:
358 virtual void do_generation(Generation* gen) = 0;
359 };
360
361 // Apply "cl.do_generation" to all generations in the heap
362 // If "old_to_young" determines the order.
363 void generation_iterate(GenClosure* cl, bool old_to_young);
364
365 // Return "true" if all generations have reached the
366 // maximal committed limit that they can reach, without a garbage
367 // collection.
368 virtual bool is_maximal_no_gc() const;
369
370 // This function returns the CardTableRS object that allows us to scan
371 // generations in a fully generational heap.
372 CardTableRS* rem_set() { return _rem_set; }
373
374 // Convenience function to be used in situations where the heap type can be
375 // asserted to be this type.
376 static GenCollectedHeap* heap();
377
378 // The ScanningOption determines which of the roots
379 // the closure is applied to:
380 // "SO_None" does none;
381 enum ScanningOption {
382 SO_None = 0x0,
383 SO_AllCodeCache = 0x8,
384 SO_ScavengeCodeCache = 0x10
385 };
386
387 private:
388 void process_roots(StrongRootsScope* scope,
389 ScanningOption so,
390 OopClosure* strong_roots,
391 OopClosure* weak_roots,
392 CLDClosure* strong_cld_closure,
393 CLDClosure* weak_cld_closure,
394 CodeBlobToOopClosure* code_roots);
395
396 void process_string_table_roots(StrongRootsScope* scope,
397 OopClosure* root_closure);
398
399 public:
400 void young_process_roots(StrongRootsScope* scope,
401 OopsInGenClosure* root_closure,
402 OopsInGenClosure* old_gen_closure,
403 CLDClosure* cld_closure);
404
405 // If "young_gen_as_roots" is false, younger generations are
406 // not scanned as roots; in this case, the caller must be arranging to
407 // scan the younger generations itself. (For example, a generation might
408 // explicitly mark reachable objects in younger generations, to avoid
409 // excess storage retention.)
410 void cms_process_roots(StrongRootsScope* scope,
411 bool young_gen_as_roots,
412 ScanningOption so,
413 bool only_strong_roots,
414 OopsInGenClosure* root_closure,
415 CLDClosure* cld_closure);
416
417 void full_process_roots(StrongRootsScope* scope,
418 bool is_adjust_phase,
419 ScanningOption so,
420 bool only_strong_roots,
421 OopsInGenClosure* root_closure,
422 CLDClosure* cld_closure);
423
424 // Apply "root_closure" to all the weak roots of the system.
425 // These include JNI weak roots, string table,
426 // and referents of reachable weak refs.
427 void gen_process_weak_roots(OopClosure* root_closure);
428
429 // Set the saved marks of generations, if that makes sense.
430 // In particular, if any generation might iterate over the oops
431 // in other generations, it should call this method.
432 void save_marks();
433
434 // Apply "cur->do_oop" or "older->do_oop" to all the oops in objects
435 // allocated since the last call to save_marks in generations at or above
436 // "level". The "cur" closure is
437 // applied to references in the generation at "level", and the "older"
438 // closure to older generations.
439 #define GCH_SINCE_SAVE_MARKS_ITERATE_DECL(OopClosureType, nv_suffix) \
440 void oop_since_save_marks_iterate(GenerationType start_gen, \
441 OopClosureType* cur, \
442 OopClosureType* older);
443
444 ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DECL)
445
446 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DECL
447
448 // Returns "true" iff no allocations have occurred since the last
449 // call to "save_marks".
450 bool no_allocs_since_save_marks();
451
452 // Returns true if an incremental collection is likely to fail.
453 // We optionally consult the young gen, if asked to do so;
454 // otherwise we base our answer on whether the previous incremental
455 // collection attempt failed with no corrective action as of yet.
456 bool incremental_collection_will_fail(bool consult_young) {
457 // The first disjunct remembers if an incremental collection failed, even
458 // when we thought (second disjunct) that it would not.
459 return incremental_collection_failed() ||
460 (consult_young && !_young_gen->collection_attempt_is_safe());
461 }
462
463 // If a generation bails out of an incremental collection,
464 // it sets this flag.
465 bool incremental_collection_failed() const {
466 return _incremental_collection_failed;
467 }
468 void set_incremental_collection_failed() {
469 _incremental_collection_failed = true;
470 }
471 void clear_incremental_collection_failed() {
472 _incremental_collection_failed = false;
473 }
474
475 // Promotion of obj into gen failed. Try to promote obj to higher
476 // gens in ascending order; return the new location of obj if successful.
477 // Otherwise, try expand-and-allocate for obj in both the young and old
478 // generation; return the new location of obj if successful. Otherwise, return NULL.
479 oop handle_failed_promotion(Generation* old_gen,
480 oop obj,
481 size_t obj_size);
482
483 private:
484 // Accessor for memory state verification support
485 NOT_PRODUCT(
486 static size_t skip_header_HeapWords() { return _skip_header_HeapWords; }
487 )
488
489 // Override
490 void check_for_non_bad_heap_word_value(HeapWord* addr,
491 size_t size) PRODUCT_RETURN;
492
493 // For use by mark-sweep. As implemented, mark-sweep-compact is global
494 // in an essential way: compaction is performed across generations, by
495 // iterating over spaces.
496 void prepare_for_compaction();
497
498 // Perform a full collection of the generations up to and including max_generation.
499 // This is the low level interface used by the public versions of
500 // collect() and collect_locked(). Caller holds the Heap_lock on entry.
501 void collect_locked(GCCause::Cause cause, GenerationType max_generation);
502
503 // Save the tops of the spaces in all generations
504 void record_gen_tops_before_GC() PRODUCT_RETURN;
505
506 protected:
507 void gc_prologue(bool full);
508 void gc_epilogue(bool full);
509
510 };
511
512 #endif // SHARE_VM_GC_SHARED_GENCOLLECTEDHEAP_HPP