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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 SlidingForwarding;
39 class StrongRootsScope;
40 class SubTasksDone;
41 class WorkerThreads;
42
43 // A "GenCollectedHeap" is a CollectedHeap that uses generational
44 // collection. It has two generations, young and old.
45 class GenCollectedHeap : public CollectedHeap {
46 friend class Generation;
47 friend class DefNewGeneration;
48 friend class TenuredGeneration;
49 friend class GenMarkSweep;
50 friend class VM_GenCollectForAllocation;
51 friend class VM_GenCollectFull;
52 friend class VM_GC_HeapInspection;
53 friend class VM_HeapDumper;
54 friend class HeapInspection;
55 friend class GCCauseSetter;
56 friend class VMStructs;
57 public:
58 friend class VM_PopulateDumpSharedSpace;
59
60 enum GenerationType {
61 YoungGen,
62 OldGen
63 };
64
65 protected:
66 Generation* _young_gen;
67 Generation* _old_gen;
68
69 private:
70 GenerationSpec* _young_gen_spec;
71 GenerationSpec* _old_gen_spec;
72
73 // The singleton CardTable Remembered Set.
74 CardTableRS* _rem_set;
75
76 SoftRefGenPolicy _soft_ref_gen_policy;
77
78 // The sizing of the heap is controlled by a sizing policy.
79 AdaptiveSizePolicy* _size_policy;
80
81 GCPolicyCounters* _gc_policy_counters;
82
83 // Indicates that the most recent previous incremental collection failed.
84 // The flag is cleared when an action is taken that might clear the
85 // condition that caused that incremental collection to fail.
86 bool _incremental_collection_failed;
87
88 // In support of ExplicitGCInvokesConcurrent functionality
89 unsigned int _full_collections_completed;
90
91 SlidingForwarding* _forwarding;
92
93 // Collects the given generation.
94 void collect_generation(Generation* gen, bool full, size_t size, bool is_tlab,
95 bool run_verification, bool clear_soft_refs);
96
97 // Reserve aligned space for the heap as needed by the contained generations.
98 ReservedHeapSpace allocate(size_t alignment);
99
100 // Initialize ("weak") refs processing support
101 void ref_processing_init();
102
103 PreGenGCValues get_pre_gc_values() const;
104
105 protected:
106
107 GCMemoryManager* _young_manager;
108 GCMemoryManager* _old_manager;
109
110 // Helper functions for allocation
111 HeapWord* attempt_allocation(size_t size,
112 bool is_tlab,
113 bool first_only);
114
115 // Helper function for two callbacks below.
116 // Considers collection of the first max_level+1 generations.
117 void do_collection(bool full,
118 bool clear_all_soft_refs,
119 size_t size,
120 bool is_tlab,
121 GenerationType max_generation);
122
123 // Callback from VM_GenCollectForAllocation operation.
124 // This function does everything necessary/possible to satisfy an
125 // allocation request that failed in the youngest generation that should
126 // have handled it (including collection, expansion, etc.)
127 HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab);
128
129 // Callback from VM_GenCollectFull operation.
130 // Perform a full collection of the first max_level+1 generations.
131 void do_full_collection(bool clear_all_soft_refs) override;
132 void do_full_collection(bool clear_all_soft_refs, GenerationType max_generation);
133
134 // Does the "cause" of GC indicate that
135 // we absolutely __must__ clear soft refs?
136 bool must_clear_all_soft_refs();
137
138 GenCollectedHeap(Generation::Name young,
139 Generation::Name old,
140 const char* policy_counters_name);
141
142 public:
143
144 // Returns JNI_OK on success
145 jint initialize() override;
146 virtual CardTableRS* create_rem_set(const MemRegion& reserved_region);
147
148 void initialize_size_policy(size_t init_eden_size,
149 size_t init_promo_size,
150 size_t init_survivor_size);
151
152 // Does operations required after initialization has been done.
153 void post_initialize() override;
154
155 Generation* young_gen() const { return _young_gen; }
156 Generation* old_gen() const { return _old_gen; }
157
158 bool is_young_gen(const Generation* gen) const { return gen == _young_gen; }
159 bool is_old_gen(const Generation* gen) const { return gen == _old_gen; }
160
161 MemRegion reserved_region() const { return _reserved; }
162 bool is_in_reserved(const void* addr) const { return _reserved.contains(addr); }
163
164 GenerationSpec* young_gen_spec() const;
165 GenerationSpec* old_gen_spec() const;
166
167 SoftRefPolicy* soft_ref_policy() override { return &_soft_ref_gen_policy; }
168
169 // Adaptive size policy
170 virtual AdaptiveSizePolicy* size_policy() {
171 return _size_policy;
172 }
173
174 // Performance Counter support
175 GCPolicyCounters* counters() { return _gc_policy_counters; }
176
177 size_t capacity() const override;
178 size_t used() const override;
179
180 // Save the "used_region" for both generations.
181 void save_used_regions();
182
183 size_t max_capacity() const override;
184
185 HeapWord* mem_allocate(size_t size, bool* gc_overhead_limit_was_exceeded) override;
186
187 // Perform a full collection of the heap; intended for use in implementing
188 // "System.gc". This implies as full a collection as the CollectedHeap
189 // supports. Caller does not hold the Heap_lock on entry.
190 void collect(GCCause::Cause cause) override;
191
192 // Returns "TRUE" iff "p" points into the committed areas of the heap.
193 // The methods is_in() and is_in_youngest() may be expensive to compute
194 // in general, so, to prevent their inadvertent use in product jvm's, we
195 // restrict their use to assertion checking or verification only.
196 bool is_in(const void* p) const override;
197
198 // Returns true if p points into the reserved space for the young generation.
199 // Assumes the young gen address range is less than that of the old gen.
200 bool is_in_young(const void* p) const;
201
202 bool requires_barriers(stackChunkOop obj) const override;
203
204 #ifdef ASSERT
205 bool is_in_partial_collection(const void* p);
206 #endif
207
208 // Optimized nmethod scanning support routines
209 void register_nmethod(nmethod* nm) override;
210 void unregister_nmethod(nmethod* nm) override;
211 void verify_nmethod(nmethod* nm) override;
212
213 void prune_scavengable_nmethods();
214
215 // Iteration functions.
216 void oop_iterate(OopIterateClosure* cl);
217 void object_iterate(ObjectClosure* cl) override;
218 Space* space_containing(const void* addr) const;
219
220 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
221 // each address in the (reserved) heap is a member of exactly
222 // one block. The defining characteristic of a block is that it is
223 // possible to find its size, and thus to progress forward to the next
224 // block. (Blocks may be of different sizes.) Thus, blocks may
225 // represent Java objects, or they might be free blocks in a
226 // free-list-based heap (or subheap), as long as the two kinds are
227 // distinguishable and the size of each is determinable.
228
229 // Returns the address of the start of the "block" that contains the
230 // address "addr". We say "blocks" instead of "object" since some heaps
231 // may not pack objects densely; a chunk may either be an object or a
232 // non-object.
233 HeapWord* block_start(const void* addr) const;
234
235 // Requires "addr" to be the start of a block, and returns "TRUE" iff
236 // the block is an object. Assumes (and verifies in non-product
237 // builds) that addr is in the allocated part of the heap and is
238 // the start of a chunk.
239 bool block_is_obj(const HeapWord* addr) const;
240
241 // Section on TLAB's.
242 size_t tlab_capacity(Thread* thr) const override;
243 size_t tlab_used(Thread* thr) const override;
244 size_t unsafe_max_tlab_alloc(Thread* thr) const override;
245 HeapWord* allocate_new_tlab(size_t min_size,
246 size_t requested_size,
247 size_t* actual_size) override;
248
249 // The "requestor" generation is performing some garbage collection
250 // action for which it would be useful to have scratch space. The
251 // requestor promises to allocate no more than "max_alloc_words" in any
252 // older generation (via promotion say.) Any blocks of space that can
253 // be provided are returned as a list of ScratchBlocks, sorted by
254 // decreasing size.
255 ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words);
256 // Allow each generation to reset any scratch space that it has
257 // contributed as it needs.
258 void release_scratch();
259
260 // Ensure parsability
261 void ensure_parsability(bool retire_tlabs) override;
262
263 // Total number of full collections completed.
264 unsigned int total_full_collections_completed() {
265 assert(_full_collections_completed <= _total_full_collections,
266 "Can't complete more collections than were started");
267 return _full_collections_completed;
268 }
269
270 // Update above counter, as appropriate, at the end of a stop-world GC cycle
271 unsigned int update_full_collections_completed();
272
273 // Update the gc statistics for each generation.
274 void update_gc_stats(Generation* current_generation, bool full) {
275 _old_gen->update_gc_stats(current_generation, full);
276 }
277
278 bool no_gc_in_progress() { return !is_gc_active(); }
279
280 void prepare_for_verify() override;
281 void verify(VerifyOption option) override;
282
283 void print_on(outputStream* st) const override;
284 void gc_threads_do(ThreadClosure* tc) const override;
285 void print_tracing_info() const override;
286
287 // Used to print information about locations in the hs_err file.
288 bool print_location(outputStream* st, void* addr) const override;
289
290 void print_heap_change(const PreGenGCValues& pre_gc_values) const;
291
292 // The functions below are helper functions that a subclass of
293 // "CollectedHeap" can use in the implementation of its virtual
294 // functions.
295
296 class GenClosure : public StackObj {
297 public:
298 virtual void do_generation(Generation* gen) = 0;
299 };
300
301 // Apply "cl.do_generation" to all generations in the heap
302 // If "old_to_young" determines the order.
303 void generation_iterate(GenClosure* cl, bool old_to_young);
304
305 // Return "true" if all generations have reached the
306 // maximal committed limit that they can reach, without a garbage
307 // collection.
308 virtual bool is_maximal_no_gc() const override;
309
310 // This function returns the CardTableRS object that allows us to scan
311 // generations in a fully generational heap.
312 CardTableRS* rem_set() { return _rem_set; }
313
314 // Convenience function to be used in situations where the heap type can be
315 // asserted to be this type.
316 static GenCollectedHeap* heap();
317
318 SlidingForwarding* forwarding() const {
319 return _forwarding;
320 }
321
322 // The ScanningOption determines which of the roots
323 // the closure is applied to:
324 // "SO_None" does none;
325 enum ScanningOption {
326 SO_None = 0x0,
327 SO_AllCodeCache = 0x8,
328 SO_ScavengeCodeCache = 0x10
329 };
330
331 protected:
332 virtual void gc_prologue(bool full);
333 virtual void gc_epilogue(bool full);
334
335 public:
336 // Apply closures on various roots in Young GC or marking/adjust phases of Full GC.
337 void process_roots(ScanningOption so,
338 OopClosure* strong_roots,
339 CLDClosure* strong_cld_closure,
340 CLDClosure* weak_cld_closure,
341 CodeBlobToOopClosure* code_roots);
342
343 // Apply "root_closure" to all the weak roots of the system.
344 // These include JNI weak roots, string table,
345 // and referents of reachable weak refs.
346 void gen_process_weak_roots(OopClosure* root_closure);
347
348 // Set the saved marks of generations, if that makes sense.
349 // In particular, if any generation might iterate over the oops
350 // in other generations, it should call this method.
351 void save_marks();
352
353 // Returns "true" iff no allocations have occurred since the last
354 // call to "save_marks".
355 bool no_allocs_since_save_marks();
356
357 // Returns true if an incremental collection is likely to fail.
358 // We optionally consult the young gen, if asked to do so;
359 // otherwise we base our answer on whether the previous incremental
360 // collection attempt failed with no corrective action as of yet.
361 bool incremental_collection_will_fail(bool consult_young) {
362 // The first disjunct remembers if an incremental collection failed, even
363 // when we thought (second disjunct) that it would not.
364 return incremental_collection_failed() ||
365 (consult_young && !_young_gen->collection_attempt_is_safe());
366 }
367
368 // If a generation bails out of an incremental collection,
369 // it sets this flag.
370 bool incremental_collection_failed() const {
371 return _incremental_collection_failed;
372 }
373 void set_incremental_collection_failed() {
374 _incremental_collection_failed = true;
375 }
376 void clear_incremental_collection_failed() {
377 _incremental_collection_failed = false;
378 }
379
380 private:
381 // Return true if an allocation should be attempted in the older generation
382 // if it fails in the younger generation. Return false, otherwise.
383 bool should_try_older_generation_allocation(size_t word_size) const;
384
385 // Try to allocate space by expanding the heap.
386 HeapWord* expand_heap_and_allocate(size_t size, bool is_tlab);
387
388 HeapWord* mem_allocate_work(size_t size,
389 bool is_tlab,
390 bool* gc_overhead_limit_was_exceeded);
391
392 #if INCLUDE_SERIALGC
393 // For use by mark-sweep. As implemented, mark-sweep-compact is global
394 // in an essential way: compaction is performed across generations, by
395 // iterating over spaces.
396 void prepare_for_compaction();
397 #endif
398
399 // Save the tops of the spaces in all generations
400 void record_gen_tops_before_GC() PRODUCT_RETURN;
401
402 // Return true if we need to perform full collection.
403 bool should_do_full_collection(size_t size, bool full,
404 bool is_tlab, GenerationType max_gen) const;
405 };
406
407 #endif // SHARE_GC_SHARED_GENCOLLECTEDHEAP_HPP