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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 WorkGang;
 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);
213 
214 #ifdef ASSERT
215   bool is_in_partial_collection(const void* p);
216 #endif
217 
218   // Optimized nmethod scanning support routines
219   virtual void register_nmethod(nmethod* nm);
220   virtual void unregister_nmethod(nmethod* nm);
221   virtual void verify_nmethod(nmethod* nm);
222   virtual void flush_nmethod(nmethod* nm);
223 
224   void prune_scavengable_nmethods();
225 
226   // Iteration functions.
227   void oop_iterate(OopIterateClosure* cl);
228   void object_iterate(ObjectClosure* cl);
229   Space* space_containing(const void* addr) const;
230 
231   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
232   // each address in the (reserved) heap is a member of exactly
233   // one block.  The defining characteristic of a block is that it is
234   // possible to find its size, and thus to progress forward to the next
235   // block.  (Blocks may be of different sizes.)  Thus, blocks may
236   // represent Java objects, or they might be free blocks in a
237   // free-list-based heap (or subheap), as long as the two kinds are
238   // distinguishable and the size of each is determinable.
239 
240   // Returns the address of the start of the "block" that contains the
241   // address "addr".  We say "blocks" instead of "object" since some heaps
242   // may not pack objects densely; a chunk may either be an object or a
243   // non-object.
244   HeapWord* block_start(const void* addr) const;
245 
246   // Requires "addr" to be the start of a block, and returns "TRUE" iff
247   // the block is an object. Assumes (and verifies in non-product
248   // builds) that addr is in the allocated part of the heap and is
249   // the start of a chunk.
250   bool block_is_obj(const HeapWord* addr) const;
251 
252   // Section on TLAB's.
253   virtual size_t tlab_capacity(Thread* thr) const;
254   virtual size_t tlab_used(Thread* thr) const;
255   virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
256   virtual HeapWord* allocate_new_tlab(size_t min_size,
257                                       size_t requested_size,
258                                       size_t* actual_size);
259 
260   // The "requestor" generation is performing some garbage collection
261   // action for which it would be useful to have scratch space.  The
262   // requestor promises to allocate no more than "max_alloc_words" in any
263   // older generation (via promotion say.)   Any blocks of space that can
264   // be provided are returned as a list of ScratchBlocks, sorted by
265   // decreasing size.
266   ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words);
267   // Allow each generation to reset any scratch space that it has
268   // contributed as it needs.
269   void release_scratch();
270 
271   // Ensure parsability: override
272   virtual void ensure_parsability(bool retire_tlabs);
273 
274   // Total number of full collections completed.
275   unsigned int total_full_collections_completed() {
276     assert(_full_collections_completed <= _total_full_collections,
277            "Can't complete more collections than were started");
278     return _full_collections_completed;
279   }
280 
281   // Update above counter, as appropriate, at the end of a stop-world GC cycle
282   unsigned int update_full_collections_completed();
283 
284   // Update the gc statistics for each generation.
285   void update_gc_stats(Generation* current_generation, bool full) {
286     _old_gen->update_gc_stats(current_generation, full);
287   }
288 
289   bool no_gc_in_progress() { return !is_gc_active(); }
290 
291   // Override.
292   void prepare_for_verify();
293 
294   // Override.
295   void verify(VerifyOption option);
296 
297   // Override.
298   virtual void print_on(outputStream* st) const;
299   virtual void gc_threads_do(ThreadClosure* tc) const;
300   virtual void print_tracing_info() const;
301 
302   // Used to print information about locations in the hs_err file.
303   virtual bool print_location(outputStream* st, void* addr) const;
304 
305   void print_heap_change(const PreGenGCValues& pre_gc_values) const;
306 
307   // The functions below are helper functions that a subclass of
308   // "CollectedHeap" can use in the implementation of its virtual
309   // functions.
310 
311   class GenClosure : public StackObj {
312    public:
313     virtual void do_generation(Generation* gen) = 0;
314   };
315 
316   // Apply "cl.do_generation" to all generations in the heap
317   // If "old_to_young" determines the order.
318   void generation_iterate(GenClosure* cl, bool old_to_young);
319 
320   // Return "true" if all generations have reached the
321   // maximal committed limit that they can reach, without a garbage
322   // collection.
323   virtual bool is_maximal_no_gc() const;
324 
325   // This function returns the CardTableRS object that allows us to scan
326   // generations in a fully generational heap.
327   CardTableRS* rem_set() { return _rem_set; }
328 
329   // Convenience function to be used in situations where the heap type can be
330   // asserted to be this type.
331   static GenCollectedHeap* heap();
332 
333   // The ScanningOption determines which of the roots
334   // the closure is applied to:
335   // "SO_None" does none;
336   enum ScanningOption {
337     SO_None                =  0x0,
338     SO_AllCodeCache        =  0x8,
339     SO_ScavengeCodeCache   = 0x10
340   };
341 
342  protected:
343   void process_roots(ScanningOption so,
344                      OopClosure* strong_roots,
345                      CLDClosure* strong_cld_closure,
346                      CLDClosure* weak_cld_closure,
347                      CodeBlobToOopClosure* code_roots);
348 
349   virtual void gc_prologue(bool full);
350   virtual void gc_epilogue(bool full);
351 
352  public:
353   void full_process_roots(bool is_adjust_phase,
354                           ScanningOption so,
355                           bool only_strong_roots,
356                           OopClosure* root_closure,
357                           CLDClosure* cld_closure);
358 
359   // Apply "root_closure" to all the weak roots of the system.
360   // These include JNI weak roots, string table,
361   // and referents of reachable weak refs.
362   void gen_process_weak_roots(OopClosure* root_closure);
363 
364   // Set the saved marks of generations, if that makes sense.
365   // In particular, if any generation might iterate over the oops
366   // in other generations, it should call this method.
367   void save_marks();
368 
369   // Returns "true" iff no allocations have occurred since the last
370   // call to "save_marks".
371   bool no_allocs_since_save_marks();
372 
373   // Returns true if an incremental collection is likely to fail.
374   // We optionally consult the young gen, if asked to do so;
375   // otherwise we base our answer on whether the previous incremental
376   // collection attempt failed with no corrective action as of yet.
377   bool incremental_collection_will_fail(bool consult_young) {
378     // The first disjunct remembers if an incremental collection failed, even
379     // when we thought (second disjunct) that it would not.
380     return incremental_collection_failed() ||
381            (consult_young && !_young_gen->collection_attempt_is_safe());
382   }
383 
384   // If a generation bails out of an incremental collection,
385   // it sets this flag.
386   bool incremental_collection_failed() const {
387     return _incremental_collection_failed;
388   }
389   void set_incremental_collection_failed() {
390     _incremental_collection_failed = true;
391   }
392   void clear_incremental_collection_failed() {
393     _incremental_collection_failed = false;
394   }
395 
396   // Promotion of obj into gen failed.  Try to promote obj to higher
397   // gens in ascending order; return the new location of obj if successful.
398   // Otherwise, try expand-and-allocate for obj in both the young and old
399   // generation; return the new location of obj if successful.  Otherwise, return NULL.
400   oop handle_failed_promotion(Generation* old_gen,
401                               oop obj,
402                               size_t obj_size);
403 
404 
405 private:
406   // Return true if an allocation should be attempted in the older generation
407   // if it fails in the younger generation.  Return false, otherwise.
408   bool should_try_older_generation_allocation(size_t word_size) const;
409 
410   // Try to allocate space by expanding the heap.
411   HeapWord* expand_heap_and_allocate(size_t size, bool is_tlab);
412 
413   HeapWord* mem_allocate_work(size_t size,
414                               bool is_tlab,
415                               bool* gc_overhead_limit_was_exceeded);
416 
417 #if INCLUDE_SERIALGC
418   // For use by mark-sweep.  As implemented, mark-sweep-compact is global
419   // in an essential way: compaction is performed across generations, by
420   // iterating over spaces.
421   void prepare_for_compaction();
422 #endif
423 
424   // Perform a full collection of the generations up to and including max_generation.
425   // This is the low level interface used by the public versions of
426   // collect() and collect_locked(). Caller holds the Heap_lock on entry.
427   void collect_locked(GCCause::Cause cause, GenerationType max_generation);
428 
429   // Save the tops of the spaces in all generations
430   void record_gen_tops_before_GC() PRODUCT_RETURN;
431 
432   // Return true if we need to perform full collection.
433   bool should_do_full_collection(size_t size, bool full,
434                                  bool is_tlab, GenerationType max_gen) const;
435 };
436 
437 #endif // SHARE_GC_SHARED_GENCOLLECTEDHEAP_HPP