1 /*
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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 virtual void do_full_collection(bool clear_all_soft_refs);
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 virtual jint initialize();
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();
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 virtual SoftRefPolicy* soft_ref_policy() { 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;
175 size_t used() const;
176
177 // Save the "used_region" for both generations.
178 void save_used_regions();
179
180 size_t max_capacity() const;
181
182 HeapWord* mem_allocate(size_t size, bool* gc_overhead_limit_was_exceeded);
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 virtual void collect(GCCause::Cause cause);
188
189 // Perform a full collection of generations up to and including max_generation.
190 // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry.
191 void collect(GCCause::Cause cause, GenerationType max_generation);
192
193 // Returns "TRUE" iff "p" points into the committed areas of the heap.
194 // The methods is_in() and is_in_youngest() may be expensive to compute
195 // in general, so, to prevent their inadvertent use in product jvm's, we
196 // restrict their use to assertion checking or verification only.
197 bool is_in(const void* p) const;
198
199 // Returns true if the reference is to an object in the reserved space
200 // for the young generation.
201 // Assumes the young gen address range is less than that of the old gen.
202 bool is_in_young(oop p) const;
203
204 virtual bool requires_barriers(stackChunkOop obj) const;
205
206 #ifdef ASSERT
207 bool is_in_partial_collection(const void* p);
208 #endif
209
210 // Optimized nmethod scanning support routines
211 virtual void register_nmethod(nmethod* nm);
212 virtual void unregister_nmethod(nmethod* nm);
213 virtual void verify_nmethod(nmethod* nm);
214 virtual void flush_nmethod(nmethod* nm);
215
216 void prune_scavengable_nmethods();
217
218 // Iteration functions.
219 void oop_iterate(OopIterateClosure* cl);
220 void object_iterate(ObjectClosure* cl);
221 Space* space_containing(const void* addr) const;
222
223 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
224 // each address in the (reserved) heap is a member of exactly
225 // one block. The defining characteristic of a block is that it is
226 // possible to find its size, and thus to progress forward to the next
227 // block. (Blocks may be of different sizes.) Thus, blocks may
228 // represent Java objects, or they might be free blocks in a
229 // free-list-based heap (or subheap), as long as the two kinds are
230 // distinguishable and the size of each is determinable.
231
232 // Returns the address of the start of the "block" that contains the
233 // address "addr". We say "blocks" instead of "object" since some heaps
234 // may not pack objects densely; a chunk may either be an object or a
235 // non-object.
236 HeapWord* block_start(const void* addr) const;
237
238 // Requires "addr" to be the start of a block, and returns "TRUE" iff
239 // the block is an object. Assumes (and verifies in non-product
240 // builds) that addr is in the allocated part of the heap and is
241 // the start of a chunk.
242 bool block_is_obj(const HeapWord* addr) const;
243
244 // Section on TLAB's.
245 virtual size_t tlab_capacity(Thread* thr) const;
246 virtual size_t tlab_used(Thread* thr) const;
247 virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
248 virtual HeapWord* allocate_new_tlab(size_t min_size,
249 size_t requested_size,
250 size_t* actual_size);
251
252 // The "requestor" generation is performing some garbage collection
253 // action for which it would be useful to have scratch space. The
254 // requestor promises to allocate no more than "max_alloc_words" in any
255 // older generation (via promotion say.) Any blocks of space that can
256 // be provided are returned as a list of ScratchBlocks, sorted by
257 // decreasing size.
258 ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words);
259 // Allow each generation to reset any scratch space that it has
260 // contributed as it needs.
261 void release_scratch();
262
263 // Ensure parsability: override
264 virtual void ensure_parsability(bool retire_tlabs);
265
266 // Total number of full collections completed.
267 unsigned int total_full_collections_completed() {
268 assert(_full_collections_completed <= _total_full_collections,
269 "Can't complete more collections than were started");
270 return _full_collections_completed;
271 }
272
273 // Update above counter, as appropriate, at the end of a stop-world GC cycle
274 unsigned int update_full_collections_completed();
275
276 // Update the gc statistics for each generation.
277 void update_gc_stats(Generation* current_generation, bool full) {
278 _old_gen->update_gc_stats(current_generation, full);
279 }
280
281 bool no_gc_in_progress() { return !is_gc_active(); }
282
283 // Override.
284 void prepare_for_verify();
285
286 // Override.
287 void verify(VerifyOption option);
288
289 // Override.
290 virtual void print_on(outputStream* st) const;
291 virtual void gc_threads_do(ThreadClosure* tc) const;
292 virtual void print_tracing_info() const;
293
294 // Used to print information about locations in the hs_err file.
295 virtual bool print_location(outputStream* st, void* addr) const;
296
297 void print_heap_change(const PreGenGCValues& pre_gc_values) const;
298
299 // The functions below are helper functions that a subclass of
300 // "CollectedHeap" can use in the implementation of its virtual
301 // functions.
302
303 class GenClosure : public StackObj {
304 public:
305 virtual void do_generation(Generation* gen) = 0;
306 };
307
308 // Apply "cl.do_generation" to all generations in the heap
309 // If "old_to_young" determines the order.
310 void generation_iterate(GenClosure* cl, bool old_to_young);
311
312 // Return "true" if all generations have reached the
313 // maximal committed limit that they can reach, without a garbage
314 // collection.
315 virtual bool is_maximal_no_gc() const;
316
317 // This function returns the CardTableRS object that allows us to scan
318 // generations in a fully generational heap.
319 CardTableRS* rem_set() { return _rem_set; }
320
321 // Convenience function to be used in situations where the heap type can be
322 // asserted to be this type.
323 static GenCollectedHeap* heap();
324
325 // The ScanningOption determines which of the roots
326 // the closure is applied to:
327 // "SO_None" does none;
328 enum ScanningOption {
329 SO_None = 0x0,
330 SO_AllCodeCache = 0x8,
331 SO_ScavengeCodeCache = 0x10
332 };
333
334 protected:
335 void process_roots(ScanningOption so,
336 OopClosure* strong_roots,
337 CLDClosure* strong_cld_closure,
338 CLDClosure* weak_cld_closure,
339 CodeBlobToOopClosure* code_roots);
340
341 virtual void gc_prologue(bool full);
342 virtual void gc_epilogue(bool full);
343
344 public:
345 void full_process_roots(bool is_adjust_phase,
346 ScanningOption so,
347 bool only_strong_roots,
348 OopClosure* root_closure,
349 CLDClosure* cld_closure);
350
351 // Apply "root_closure" to all the weak roots of the system.
352 // These include JNI weak roots, string table,
353 // and referents of reachable weak refs.
354 void gen_process_weak_roots(OopClosure* root_closure);
355
356 // Set the saved marks of generations, if that makes sense.
357 // In particular, if any generation might iterate over the oops
358 // in other generations, it should call this method.
359 void save_marks();
360
361 // Returns "true" iff no allocations have occurred since the last
362 // call to "save_marks".
363 bool no_allocs_since_save_marks();
364
365 // Returns true if an incremental collection is likely to fail.
366 // We optionally consult the young gen, if asked to do so;
367 // otherwise we base our answer on whether the previous incremental
368 // collection attempt failed with no corrective action as of yet.
369 bool incremental_collection_will_fail(bool consult_young) {
370 // The first disjunct remembers if an incremental collection failed, even
371 // when we thought (second disjunct) that it would not.
372 return incremental_collection_failed() ||
373 (consult_young && !_young_gen->collection_attempt_is_safe());
374 }
375
376 // If a generation bails out of an incremental collection,
377 // it sets this flag.
378 bool incremental_collection_failed() const {
379 return _incremental_collection_failed;
380 }
381 void set_incremental_collection_failed() {
382 _incremental_collection_failed = true;
383 }
384 void clear_incremental_collection_failed() {
385 _incremental_collection_failed = false;
386 }
387
388 // Promotion of obj into gen failed. Try to promote obj to higher
389 // gens in ascending order; return the new location of obj if successful.
390 // Otherwise, try expand-and-allocate for obj in both the young and old
391 // generation; return the new location of obj if successful. Otherwise, return NULL.
392 oop handle_failed_promotion(Generation* old_gen,
393 oop obj,
394 size_t obj_size);
395
396
397 private:
398 // Return true if an allocation should be attempted in the older generation
399 // if it fails in the younger generation. Return false, otherwise.
400 bool should_try_older_generation_allocation(size_t word_size) const;
401
402 // Try to allocate space by expanding the heap.
403 HeapWord* expand_heap_and_allocate(size_t size, bool is_tlab);
404
405 HeapWord* mem_allocate_work(size_t size,
406 bool is_tlab,
407 bool* gc_overhead_limit_was_exceeded);
408
409 #if INCLUDE_SERIALGC
410 // For use by mark-sweep. As implemented, mark-sweep-compact is global
411 // in an essential way: compaction is performed across generations, by
412 // iterating over spaces.
413 void prepare_for_compaction();
414 #endif
415
416 // Save the tops of the spaces in all generations
417 void record_gen_tops_before_GC() PRODUCT_RETURN;
418
419 // Return true if we need to perform full collection.
420 bool should_do_full_collection(size_t size, bool full,
421 bool is_tlab, GenerationType max_gen) const;
422 };
423
424 #endif // SHARE_GC_SHARED_GENCOLLECTEDHEAP_HPP