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