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24
25 #ifndef SHARE_GC_SHARED_GENCOLLECTEDHEAP_HPP
26 #define SHARE_GC_SHARED_GENCOLLECTEDHEAP_HPP
27
28 #include "gc/shared/collectedHeap.hpp"
29 #include "gc/shared/generation.hpp"
30 #include "gc/shared/oopStorageParState.hpp"
31 #include "gc/shared/preGCValues.hpp"
32 #include "gc/shared/softRefGenPolicy.hpp"
33
34 class AdaptiveSizePolicy;
35 class CardTableRS;
36 class GCPolicyCounters;
37 class GenerationSpec;
38 class StrongRootsScope;
39 class SubTasksDone;
40 class WorkerThreads;
41
42 // A "GenCollectedHeap" is a CollectedHeap that uses generational
43 // collection. It has two generations, young and old.
44 class GenCollectedHeap : public CollectedHeap {
45 friend class Generation;
46 friend class DefNewGeneration;
47 friend class TenuredGeneration;
48 friend class GenMarkSweep;
49 friend class VM_GenCollectForAllocation;
50 friend class VM_GenCollectFull;
51 friend class VM_GC_HeapInspection;
52 friend class VM_HeapDumper;
53 friend class HeapInspection;
54 friend class GCCauseSetter;
55 friend class VMStructs;
56 public:
57 friend class VM_PopulateDumpSharedSpace;
58
59 enum GenerationType {
60 YoungGen,
61 OldGen
62 };
63
64 protected:
65 Generation* _young_gen;
66 Generation* _old_gen;
67
68 private:
69 GenerationSpec* _young_gen_spec;
70 GenerationSpec* _old_gen_spec;
71
72 // The singleton CardTable Remembered Set.
73 CardTableRS* _rem_set;
74
75 SoftRefGenPolicy _soft_ref_gen_policy;
76
77 // The sizing of the heap is controlled by a sizing policy.
78 AdaptiveSizePolicy* _size_policy;
79
80 GCPolicyCounters* _gc_policy_counters;
81
82 // Indicates that the most recent previous incremental collection failed.
83 // The flag is cleared when an action is taken that might clear the
84 // condition that caused that incremental collection to fail.
85 bool _incremental_collection_failed;
86
87 // In support of ExplicitGCInvokesConcurrent functionality
88 unsigned int _full_collections_completed;
89
90 // Collects the given generation.
91 void collect_generation(Generation* gen, bool full, size_t size, bool is_tlab,
92 bool run_verification, bool clear_soft_refs);
93
94 // Reserve aligned space for the heap as needed by the contained generations.
95 ReservedHeapSpace allocate(size_t alignment);
96
97 // Initialize ("weak") refs processing support
98 void ref_processing_init();
99
100 PreGenGCValues get_pre_gc_values() const;
101
102 protected:
103
104 GCMemoryManager* _young_manager;
105 GCMemoryManager* _old_manager;
106
107 // Helper functions for allocation
108 HeapWord* attempt_allocation(size_t size,
109 bool is_tlab,
110 bool first_only);
111
112 // Helper function for two callbacks below.
113 // Considers collection of the first max_level+1 generations.
114 void do_collection(bool full,
115 bool clear_all_soft_refs,
116 size_t size,
117 bool is_tlab,
118 GenerationType max_generation);
119
120 // Callback from VM_GenCollectForAllocation operation.
121 // This function does everything necessary/possible to satisfy an
122 // allocation request that failed in the youngest generation that should
123 // have handled it (including collection, expansion, etc.)
124 HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab);
125
126 // Callback from VM_GenCollectFull operation.
127 // Perform a full collection of the first max_level+1 generations.
128 void do_full_collection(bool clear_all_soft_refs) override;
129 void do_full_collection(bool clear_all_soft_refs, GenerationType max_generation);
130
131 // Does the "cause" of GC indicate that
132 // we absolutely __must__ clear soft refs?
133 bool must_clear_all_soft_refs();
134
135 GenCollectedHeap(Generation::Name young,
136 Generation::Name old,
137 const char* policy_counters_name);
138
139 public:
140
141 // Returns JNI_OK on success
142 jint initialize() override;
143 virtual CardTableRS* create_rem_set(const MemRegion& reserved_region);
144
145 void initialize_size_policy(size_t init_eden_size,
146 size_t init_promo_size,
147 size_t init_survivor_size);
148
149 // Does operations required after initialization has been done.
150 void post_initialize() override;
151
152 Generation* young_gen() const { return _young_gen; }
153 Generation* old_gen() const { return _old_gen; }
154
155 bool is_young_gen(const Generation* gen) const { return gen == _young_gen; }
156 bool is_old_gen(const Generation* gen) const { return gen == _old_gen; }
157
158 MemRegion reserved_region() const { return _reserved; }
159 bool is_in_reserved(const void* addr) const { return _reserved.contains(addr); }
160
161 GenerationSpec* young_gen_spec() const;
162 GenerationSpec* old_gen_spec() const;
163
164 SoftRefPolicy* soft_ref_policy() override { return &_soft_ref_gen_policy; }
165
166 // Adaptive size policy
167 virtual AdaptiveSizePolicy* size_policy() {
168 return _size_policy;
169 }
170
171 // Performance Counter support
172 GCPolicyCounters* counters() { return _gc_policy_counters; }
173
174 size_t capacity() const override;
175 size_t used() const override;
176
177 // Save the "used_region" for both generations.
178 void save_used_regions();
179
180 size_t max_capacity() const override;
181
182 HeapWord* mem_allocate(size_t size, bool* gc_overhead_limit_was_exceeded) override;
183
184 // Perform a full collection of the heap; intended for use in implementing
185 // "System.gc". This implies as full a collection as the CollectedHeap
186 // supports. Caller does not hold the Heap_lock on entry.
187 void collect(GCCause::Cause cause) override;
188
189 // Returns "TRUE" iff "p" points into the committed areas of the heap.
190 // The methods is_in() and is_in_youngest() may be expensive to compute
191 // in general, so, to prevent their inadvertent use in product jvm's, we
192 // restrict their use to assertion checking or verification only.
193 bool is_in(const void* p) const override;
194
195 // Returns true if p points into the reserved space for the young generation.
196 // Assumes the young gen address range is less than that of the old gen.
197 bool is_in_young(const void* p) const;
198
199 bool requires_barriers(stackChunkOop obj) const override;
200
201 #ifdef ASSERT
202 bool is_in_partial_collection(const void* p);
203 #endif
204
205 // Optimized nmethod scanning support routines
206 void register_nmethod(nmethod* nm) override;
207 void unregister_nmethod(nmethod* nm) override;
208 void verify_nmethod(nmethod* nm) override;
209
210 void prune_scavengable_nmethods();
211
212 // Iteration functions.
213 void oop_iterate(OopIterateClosure* cl);
214 void object_iterate(ObjectClosure* cl) override;
215 Space* space_containing(const void* addr) const;
216
217 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
218 // each address in the (reserved) heap is a member of exactly
219 // one block. The defining characteristic of a block is that it is
220 // possible to find its size, and thus to progress forward to the next
221 // block. (Blocks may be of different sizes.) Thus, blocks may
222 // represent Java objects, or they might be free blocks in a
223 // free-list-based heap (or subheap), as long as the two kinds are
224 // distinguishable and the size of each is determinable.
225
226 // Returns the address of the start of the "block" that contains the
227 // address "addr". We say "blocks" instead of "object" since some heaps
228 // may not pack objects densely; a chunk may either be an object or a
229 // non-object.
230 HeapWord* block_start(const void* addr) const;
231
232 // Requires "addr" to be the start of a block, and returns "TRUE" iff
233 // the block is an object. Assumes (and verifies in non-product
234 // builds) that addr is in the allocated part of the heap and is
235 // the start of a chunk.
236 bool block_is_obj(const HeapWord* addr) const;
237
238 // Section on TLAB's.
239 size_t tlab_capacity(Thread* thr) const override;
240 size_t tlab_used(Thread* thr) const override;
241 size_t unsafe_max_tlab_alloc(Thread* thr) const override;
242 HeapWord* allocate_new_tlab(size_t min_size,
243 size_t requested_size,
244 size_t* actual_size) override;
245
246 // The "requestor" generation is performing some garbage collection
247 // action for which it would be useful to have scratch space. The
248 // requestor promises to allocate no more than "max_alloc_words" in any
249 // older generation (via promotion say.) Any blocks of space that can
250 // be provided are returned as a list of ScratchBlocks, sorted by
251 // decreasing size.
252 ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words);
253 // Allow each generation to reset any scratch space that it has
254 // contributed as it needs.
255 void release_scratch();
256
257 // Ensure parsability
258 void ensure_parsability(bool retire_tlabs) override;
259
260 // Total number of full collections completed.
261 unsigned int total_full_collections_completed() {
262 assert(_full_collections_completed <= _total_full_collections,
263 "Can't complete more collections than were started");
264 return _full_collections_completed;
265 }
266
267 // Update above counter, as appropriate, at the end of a stop-world GC cycle
268 unsigned int update_full_collections_completed();
269
270 // Update the gc statistics for each generation.
271 void update_gc_stats(Generation* current_generation, bool full) {
272 _old_gen->update_gc_stats(current_generation, full);
273 }
274
275 bool no_gc_in_progress() { return !is_gc_active(); }
276
277 void prepare_for_verify() override;
278 void verify(VerifyOption option) override;
279
280 void print_on(outputStream* st) const override;
281 void gc_threads_do(ThreadClosure* tc) const override;
282 void print_tracing_info() const override;
283
284 // Used to print information about locations in the hs_err file.
285 bool print_location(outputStream* st, void* addr) const override;
286
287 void print_heap_change(const PreGenGCValues& pre_gc_values) const;
288
289 // The functions below are helper functions that a subclass of
290 // "CollectedHeap" can use in the implementation of its virtual
291 // functions.
292
293 class GenClosure : public StackObj {
294 public:
295 virtual void do_generation(Generation* gen) = 0;
296 };
297
298 // Apply "cl.do_generation" to all generations in the heap
299 // If "old_to_young" determines the order.
300 void generation_iterate(GenClosure* cl, bool old_to_young);
301
302 // Return "true" if all generations have reached the
303 // maximal committed limit that they can reach, without a garbage
304 // collection.
305 virtual bool is_maximal_no_gc() const override;
306
307 // This function returns the CardTableRS object that allows us to scan
308 // generations in a fully generational heap.
309 CardTableRS* rem_set() { return _rem_set; }
310
311 // Convenience function to be used in situations where the heap type can be
312 // asserted to be this type.
313 static GenCollectedHeap* heap();
314
315 // The ScanningOption determines which of the roots
316 // the closure is applied to:
317 // "SO_None" does none;
318 enum ScanningOption {
319 SO_None = 0x0,
320 SO_AllCodeCache = 0x8,
321 SO_ScavengeCodeCache = 0x10
322 };
323
324 protected:
325 virtual void gc_prologue(bool full);
326 virtual void gc_epilogue(bool full);
327
328 public:
329 // Apply closures on various roots in Young GC or marking/adjust phases of Full GC.
330 void process_roots(ScanningOption so,
331 OopClosure* strong_roots,
332 CLDClosure* strong_cld_closure,
333 CLDClosure* weak_cld_closure,
334 CodeBlobToOopClosure* code_roots);
335
336 // Apply "root_closure" to all the weak roots of the system.
337 // These include JNI weak roots, string table,
338 // and referents of reachable weak refs.
339 void gen_process_weak_roots(OopClosure* root_closure);
340
341 // Set the saved marks of generations, if that makes sense.
342 // In particular, if any generation might iterate over the oops
343 // in other generations, it should call this method.
344 void save_marks();
345
346 // Returns "true" iff no allocations have occurred since the last
347 // call to "save_marks".
348 bool no_allocs_since_save_marks();
349
350 // Returns true if an incremental collection is likely to fail.
351 // We optionally consult the young gen, if asked to do so;
352 // otherwise we base our answer on whether the previous incremental
353 // collection attempt failed with no corrective action as of yet.
354 bool incremental_collection_will_fail(bool consult_young) {
355 // The first disjunct remembers if an incremental collection failed, even
356 // when we thought (second disjunct) that it would not.
357 return incremental_collection_failed() ||
358 (consult_young && !_young_gen->collection_attempt_is_safe());
359 }
360
361 // If a generation bails out of an incremental collection,
362 // it sets this flag.
363 bool incremental_collection_failed() const {
364 return _incremental_collection_failed;
365 }
366 void set_incremental_collection_failed() {
367 _incremental_collection_failed = true;
368 }
369 void clear_incremental_collection_failed() {
370 _incremental_collection_failed = false;
371 }
372
373 private:
374 // Return true if an allocation should be attempted in the older generation
375 // if it fails in the younger generation. Return false, otherwise.
376 bool should_try_older_generation_allocation(size_t word_size) const;
377
378 // Try to allocate space by expanding the heap.
379 HeapWord* expand_heap_and_allocate(size_t size, bool is_tlab);
380
381 HeapWord* mem_allocate_work(size_t size,
382 bool is_tlab,
383 bool* gc_overhead_limit_was_exceeded);
384
385 #if INCLUDE_SERIALGC
386 // For use by mark-sweep. As implemented, mark-sweep-compact is global
387 // in an essential way: compaction is performed across generations, by
388 // iterating over spaces.
389 void prepare_for_compaction();
390 #endif
391
392 // Save the tops of the spaces in all generations
393 void record_gen_tops_before_GC() PRODUCT_RETURN;
394
395 // Return true if we need to perform full collection.
396 bool should_do_full_collection(size_t size, bool full,
397 bool is_tlab, GenerationType max_gen) const;
398 };
399
400 #endif // SHARE_GC_SHARED_GENCOLLECTEDHEAP_HPP