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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_GenCollectFullConcurrent;
 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   // Collects the given generation.
 92   void collect_generation(Generation* gen, bool full, size_t size, bool is_tlab,
 93                           bool run_verification, bool clear_soft_refs);
 94 
 95   // Reserve aligned space for the heap as needed by the contained generations.
 96   ReservedHeapSpace allocate(size_t alignment);
 97 
 98   // Initialize ("weak") refs processing support
 99   void ref_processing_init();
100 
101   PreGenGCValues get_pre_gc_values() const;
102 
103 protected:
104 
105   GCMemoryManager* _young_manager;
106   GCMemoryManager* _old_manager;
107 
108   // Helper functions for allocation
109   HeapWord* attempt_allocation(size_t size,
110                                bool   is_tlab,
111                                bool   first_only);
112 
113   // Helper function for two callbacks below.
114   // Considers collection of the first max_level+1 generations.
115   void do_collection(bool           full,
116                      bool           clear_all_soft_refs,
117                      size_t         size,
118                      bool           is_tlab,
119                      GenerationType max_generation);
120 
121   // Callback from VM_GenCollectForAllocation operation.
122   // This function does everything necessary/possible to satisfy an
123   // allocation request that failed in the youngest generation that should
124   // have handled it (including collection, expansion, etc.)
125   HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab);
126 
127   // Callback from VM_GenCollectFull operation.
128   // Perform a full collection of the first max_level+1 generations.
129   virtual void do_full_collection(bool clear_all_soft_refs);
130   void do_full_collection(bool clear_all_soft_refs, GenerationType max_generation);
131 
132   // Does the "cause" of GC indicate that
133   // we absolutely __must__ clear soft refs?
134   bool must_clear_all_soft_refs();
135 
136   GenCollectedHeap(Generation::Name young,
137                    Generation::Name old,
138                    const char* policy_counters_name);
139 
140 public:
141 
142   // Returns JNI_OK on success
143   virtual jint initialize();
144   virtual CardTableRS* create_rem_set(const MemRegion& reserved_region);
145 
146   void initialize_size_policy(size_t init_eden_size,
147                               size_t init_promo_size,
148                               size_t init_survivor_size);
149 
150   // Does operations required after initialization has been done.
151   void post_initialize();
152 
153   Generation* young_gen() const { return _young_gen; }
154   Generation* old_gen()   const { return _old_gen; }
155 
156   bool is_young_gen(const Generation* gen) const { return gen == _young_gen; }
157   bool is_old_gen(const Generation* gen) const { return gen == _old_gen; }
158 
159   MemRegion reserved_region() const { return _reserved; }
160   bool is_in_reserved(const void* addr) const { return _reserved.contains(addr); }
161 
162   GenerationSpec* young_gen_spec() const;
163   GenerationSpec* old_gen_spec() const;
164 
165   virtual SoftRefPolicy* soft_ref_policy() { return &_soft_ref_gen_policy; }
166 
167   // Adaptive size policy
168   virtual AdaptiveSizePolicy* size_policy() {
169     return _size_policy;
170   }
171 
172   // Performance Counter support
173   GCPolicyCounters* counters()     { return _gc_policy_counters; }
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() and is_in_youngest() may be expensive to compute
205   // in general, so, to prevent their inadvertent use in product jvm's, we
206   // restrict their use to assertion checking or verification only.
207   bool is_in(const void* p) const;
208 
209   // Returns true if the reference is to an object in the reserved space
210   // for the young generation.
211   // Assumes the the young gen address range is less than that of the old gen.
212   bool is_in_young(oop p) const;
213 
214   virtual bool requires_barriers(oop obj) const { return !is_in_young(obj); }
215 
216 #ifdef ASSERT
217   bool is_in_partial_collection(const void* p);
218 #endif
219 
220   // Optimized nmethod scanning support routines
221   virtual void register_nmethod(nmethod* nm);
222   virtual void unregister_nmethod(nmethod* nm);
223   virtual void verify_nmethod(nmethod* nm);
224   virtual void flush_nmethod(nmethod* nm);
225 
226   void prune_scavengable_nmethods();
227 
228   // Iteration functions.
229   void oop_iterate(OopIterateClosure* cl);
230   void object_iterate(ObjectClosure* cl);
231   Space* space_containing(const void* addr) const;
232 
233   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
234   // each address in the (reserved) heap is a member of exactly
235   // one block.  The defining characteristic of a block is that it is
236   // possible to find its size, and thus to progress forward to the next
237   // block.  (Blocks may be of different sizes.)  Thus, blocks may
238   // represent Java objects, or they might be free blocks in a
239   // free-list-based heap (or subheap), as long as the two kinds are
240   // distinguishable and the size of each is determinable.
241 
242   // Returns the address of the start of the "block" that contains the
243   // address "addr".  We say "blocks" instead of "object" since some heaps
244   // may not pack objects densely; a chunk may either be an object or a
245   // non-object.
246   HeapWord* block_start(const void* addr) const;
247 
248   // Requires "addr" to be the start of a block, and returns "TRUE" iff
249   // the block is an object. Assumes (and verifies in non-product
250   // builds) that addr is in the allocated part of the heap and is
251   // the start of a chunk.
252   bool block_is_obj(const HeapWord* addr) const;
253 
254   // Section on TLAB's.
255   virtual size_t tlab_capacity(Thread* thr) const;
256   virtual size_t tlab_used(Thread* thr) const;
257   virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
258   virtual HeapWord* allocate_new_tlab(size_t min_size,
259                                       size_t requested_size,
260                                       size_t* actual_size);
261 
262   // The "requestor" generation is performing some garbage collection
263   // action for which it would be useful to have scratch space.  The
264   // requestor promises to allocate no more than "max_alloc_words" in any
265   // older generation (via promotion say.)   Any blocks of space that can
266   // be provided are returned as a list of ScratchBlocks, sorted by
267   // decreasing size.
268   ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words);
269   // Allow each generation to reset any scratch space that it has
270   // contributed as it needs.
271   void release_scratch();
272 
273   // Ensure parsability: override
274   virtual void ensure_parsability(bool retire_tlabs);
275 
276   // Total number of full collections completed.
277   unsigned int total_full_collections_completed() {
278     assert(_full_collections_completed <= _total_full_collections,
279            "Can't complete more collections than were started");
280     return _full_collections_completed;
281   }
282 
283   // Update above counter, as appropriate, at the end of a stop-world GC cycle
284   unsigned int update_full_collections_completed();
285 
286   // Update the gc statistics for each generation.
287   void update_gc_stats(Generation* current_generation, bool full) {
288     _old_gen->update_gc_stats(current_generation, full);
289   }
290 
291   bool no_gc_in_progress() { return !is_gc_active(); }
292 
293   // Override.
294   void prepare_for_verify();
295 
296   // Override.
297   void verify(VerifyOption option);
298 
299   // Override.
300   virtual void print_on(outputStream* st) const;
301   virtual void gc_threads_do(ThreadClosure* tc) const;
302   virtual void print_tracing_info() const;
303 
304   // Used to print information about locations in the hs_err file.
305   virtual bool print_location(outputStream* st, void* addr) const;
306 
307   void print_heap_change(const PreGenGCValues& pre_gc_values) const;
308 
309   // The functions below are helper functions that a subclass of
310   // "CollectedHeap" can use in the implementation of its virtual
311   // functions.
312 
313   class GenClosure : public StackObj {
314    public:
315     virtual void do_generation(Generation* gen) = 0;
316   };
317 
318   // Apply "cl.do_generation" to all generations in the heap
319   // If "old_to_young" determines the order.
320   void generation_iterate(GenClosure* cl, bool old_to_young);
321 
322   // Return "true" if all generations have reached the
323   // maximal committed limit that they can reach, without a garbage
324   // collection.
325   virtual bool is_maximal_no_gc() const;
326 
327   // This function returns the CardTableRS object that allows us to scan
328   // generations in a fully generational heap.
329   CardTableRS* rem_set() { return _rem_set; }
330 
331   // Convenience function to be used in situations where the heap type can be
332   // asserted to be this type.
333   static GenCollectedHeap* heap();
334 
335   // The ScanningOption determines which of the roots
336   // the closure is applied to:
337   // "SO_None" does none;
338   enum ScanningOption {
339     SO_None                =  0x0,
340     SO_AllCodeCache        =  0x8,
341     SO_ScavengeCodeCache   = 0x10
342   };
343 
344  protected:
345   void process_roots(ScanningOption so,
346                      OopClosure* strong_roots,
347                      CLDClosure* strong_cld_closure,
348                      CLDClosure* weak_cld_closure,
349                      CodeBlobToOopClosure* code_roots);
350 
351   virtual void gc_prologue(bool full);
352   virtual void gc_epilogue(bool full);
353 
354  public:
355   void full_process_roots(bool is_adjust_phase,
356                           ScanningOption so,
357                           bool only_strong_roots,
358                           OopClosure* root_closure,
359                           CLDClosure* cld_closure);
360 
361   // Apply "root_closure" to all the weak roots of the system.
362   // These include JNI weak roots, string table,
363   // and referents of reachable weak refs.
364   void gen_process_weak_roots(OopClosure* root_closure);
365 
366   // Set the saved marks of generations, if that makes sense.
367   // In particular, if any generation might iterate over the oops
368   // in other generations, it should call this method.
369   void save_marks();
370 
371   // Returns "true" iff no allocations have occurred since the last
372   // call to "save_marks".
373   bool no_allocs_since_save_marks();
374 
375   // Returns true if an incremental collection is likely to fail.
376   // We optionally consult the young gen, if asked to do so;
377   // otherwise we base our answer on whether the previous incremental
378   // collection attempt failed with no corrective action as of yet.
379   bool incremental_collection_will_fail(bool consult_young) {
380     // The first disjunct remembers if an incremental collection failed, even
381     // when we thought (second disjunct) that it would not.
382     return incremental_collection_failed() ||
383            (consult_young && !_young_gen->collection_attempt_is_safe());
384   }
385 
386   // If a generation bails out of an incremental collection,
387   // it sets this flag.
388   bool incremental_collection_failed() const {
389     return _incremental_collection_failed;
390   }
391   void set_incremental_collection_failed() {
392     _incremental_collection_failed = true;
393   }
394   void clear_incremental_collection_failed() {
395     _incremental_collection_failed = false;
396   }
397 
398   // Promotion of obj into gen failed.  Try to promote obj to higher
399   // gens in ascending order; return the new location of obj if successful.
400   // Otherwise, try expand-and-allocate for obj in both the young and old
401   // generation; return the new location of obj if successful.  Otherwise, return NULL.
402   oop handle_failed_promotion(Generation* old_gen,
403                               oop obj,
404                               size_t obj_size);
405 
406 
407 private:
408   // Return true if an allocation should be attempted in the older generation
409   // if it fails in the younger generation.  Return false, otherwise.
410   bool should_try_older_generation_allocation(size_t word_size) const;
411 
412   // Try to allocate space by expanding the heap.
413   HeapWord* expand_heap_and_allocate(size_t size, bool is_tlab);
414 
415   HeapWord* mem_allocate_work(size_t size,
416                               bool is_tlab,
417                               bool* gc_overhead_limit_was_exceeded);
418 
419 #if INCLUDE_SERIALGC
420   // For use by mark-sweep.  As implemented, mark-sweep-compact is global
421   // in an essential way: compaction is performed across generations, by
422   // iterating over spaces.
423   void prepare_for_compaction();
424 #endif
425 
426   // Perform a full collection of the generations up to and including max_generation.
427   // This is the low level interface used by the public versions of
428   // collect() and collect_locked(). Caller holds the Heap_lock on entry.
429   void collect_locked(GCCause::Cause cause, GenerationType max_generation);
430 
431   // Save the tops of the spaces in all generations
432   void record_gen_tops_before_GC() PRODUCT_RETURN;
433 
434   // Return true if we need to perform full collection.
435   bool should_do_full_collection(size_t size, bool full,
436                                  bool is_tlab, GenerationType max_gen) const;
437 };
438 
439 #endif // SHARE_GC_SHARED_GENCOLLECTEDHEAP_HPP