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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_GenCollectFullConcurrent;
 53   friend class VM_GC_HeapInspection;
 54   friend class VM_HeapDumper;
 55   friend class HeapInspection;
 56   friend class GCCauseSetter;
 57   friend class VMStructs;
 58 public:
 59   friend class VM_PopulateDumpSharedSpace;
 60 
 61   enum GenerationType {
 62     YoungGen,
 63     OldGen
 64   };
 65 
 66 protected:
 67   Generation* _young_gen;
 68   Generation* _old_gen;
 69 
 70 private:
 71   GenerationSpec* _young_gen_spec;
 72   GenerationSpec* _old_gen_spec;
 73 
 74   // The singleton CardTable Remembered Set.
 75   CardTableRS* _rem_set;
 76 
 77   SoftRefGenPolicy _soft_ref_gen_policy;
 78 
 79   // The sizing of the heap is controlled by a sizing policy.
 80   AdaptiveSizePolicy* _size_policy;
 81 
 82   GCPolicyCounters* _gc_policy_counters;
 83 
 84   // Indicates that the most recent previous incremental collection failed.
 85   // The flag is cleared when an action is taken that might clear the
 86   // condition that caused that incremental collection to fail.
 87   bool _incremental_collection_failed;
 88 
 89   // In support of ExplicitGCInvokesConcurrent functionality
 90   unsigned int _full_collections_completed;
 91 
 92   SlidingForwarding* _forwarding;
 93 
 94   // Collects the given generation.
 95   void collect_generation(Generation* gen, bool full, size_t size, bool is_tlab,
 96                           bool run_verification, bool clear_soft_refs);
 97 
 98   // Reserve aligned space for the heap as needed by the contained generations.
 99   ReservedHeapSpace allocate(size_t alignment);
100 
101   // Initialize ("weak") refs processing support
102   void ref_processing_init();
103 
104   PreGenGCValues get_pre_gc_values() const;
105 
106 protected:
107 
108   GCMemoryManager* _young_manager;
109   GCMemoryManager* _old_manager;
110 
111   // Helper functions for allocation
112   HeapWord* attempt_allocation(size_t size,
113                                bool   is_tlab,
114                                bool   first_only);
115 
116   // Helper function for two callbacks below.
117   // Considers collection of the first max_level+1 generations.
118   void do_collection(bool           full,
119                      bool           clear_all_soft_refs,
120                      size_t         size,
121                      bool           is_tlab,
122                      GenerationType max_generation);
123 
124   // Callback from VM_GenCollectForAllocation operation.
125   // This function does everything necessary/possible to satisfy an
126   // allocation request that failed in the youngest generation that should
127   // have handled it (including collection, expansion, etc.)
128   HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab);
129 
130   // Callback from VM_GenCollectFull operation.
131   // Perform a full collection of the first max_level+1 generations.
132   virtual void do_full_collection(bool clear_all_soft_refs);
133   void do_full_collection(bool clear_all_soft_refs, GenerationType max_generation);
134 
135   // Does the "cause" of GC indicate that
136   // we absolutely __must__ clear soft refs?
137   bool must_clear_all_soft_refs();
138 
139   GenCollectedHeap(Generation::Name young,
140                    Generation::Name old,
141                    const char* policy_counters_name);
142 
143 public:
144 
145   // Returns JNI_OK on success
146   virtual jint initialize();
147   virtual CardTableRS* create_rem_set(const MemRegion& reserved_region);
148 
149   void initialize_size_policy(size_t init_eden_size,
150                               size_t init_promo_size,
151                               size_t init_survivor_size);
152 
153   // Does operations required after initialization has been done.
154   void post_initialize();
155 
156   Generation* young_gen() const { return _young_gen; }
157   Generation* old_gen()   const { return _old_gen; }
158 
159   bool is_young_gen(const Generation* gen) const { return gen == _young_gen; }
160   bool is_old_gen(const Generation* gen) const { return gen == _old_gen; }
161 
162   MemRegion reserved_region() const { return _reserved; }
163   bool is_in_reserved(const void* addr) const { return _reserved.contains(addr); }
164 
165   GenerationSpec* young_gen_spec() const;
166   GenerationSpec* old_gen_spec() const;
167 
168   virtual SoftRefPolicy* soft_ref_policy() { return &_soft_ref_gen_policy; }
169 
170   // Adaptive size policy
171   virtual AdaptiveSizePolicy* size_policy() {
172     return _size_policy;
173   }
174 
175   // Performance Counter support
176   GCPolicyCounters* counters()     { return _gc_policy_counters; }
177 
178   size_t capacity() const;
179   size_t used() const;
180 
181   // Save the "used_region" for both generations.
182   void save_used_regions();
183 
184   size_t max_capacity() const;
185 
186   HeapWord* mem_allocate(size_t size, bool*  gc_overhead_limit_was_exceeded);
187 
188   // We may support a shared contiguous allocation area, if the youngest
189   // generation does.
190   bool supports_inline_contig_alloc() const;
191   HeapWord* volatile* top_addr() const;
192   HeapWord** end_addr() const;
193 
194   // Perform a full collection of the heap; intended for use in implementing
195   // "System.gc". This implies as full a collection as the CollectedHeap
196   // supports. Caller does not hold the Heap_lock on entry.
197   virtual void collect(GCCause::Cause cause);
198 
199   // The same as above but assume that the caller holds the Heap_lock.
200   void collect_locked(GCCause::Cause cause);
201 
202   // Perform a full collection of generations up to and including max_generation.
203   // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry.
204   void collect(GCCause::Cause cause, GenerationType max_generation);
205 
206   // Returns "TRUE" iff "p" points into the committed areas of the heap.
207   // The methods is_in() and is_in_youngest() may be expensive to compute
208   // in general, so, to prevent their inadvertent use in product jvm's, we
209   // restrict their use to assertion checking or verification only.
210   bool is_in(const void* p) const;
211 
212   // Returns true if the reference is to an object in the reserved space
213   // for the young generation.
214   // Assumes the the young gen address range is less than that of the old gen.
215   bool is_in_young(oop p);
216 
217 #ifdef ASSERT
218   bool is_in_partial_collection(const void* p);
219 #endif
220 
221   // Optimized nmethod scanning support routines
222   virtual void register_nmethod(nmethod* nm);
223   virtual void unregister_nmethod(nmethod* nm);
224   virtual void verify_nmethod(nmethod* nm);
225   virtual void flush_nmethod(nmethod* nm);
226 
227   void prune_scavengable_nmethods();
228 
229   // Iteration functions.
230   void oop_iterate(OopIterateClosure* cl);
231   void object_iterate(ObjectClosure* cl);
232   Space* space_containing(const void* addr) const;
233 
234   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
235   // each address in the (reserved) heap is a member of exactly
236   // one block.  The defining characteristic of a block is that it is
237   // possible to find its size, and thus to progress forward to the next
238   // block.  (Blocks may be of different sizes.)  Thus, blocks may
239   // represent Java objects, or they might be free blocks in a
240   // free-list-based heap (or subheap), as long as the two kinds are
241   // distinguishable and the size of each is determinable.
242 
243   // Returns the address of the start of the "block" that contains the
244   // address "addr".  We say "blocks" instead of "object" since some heaps
245   // may not pack objects densely; a chunk may either be an object or a
246   // non-object.
247   HeapWord* block_start(const void* addr) const;
248 
249   // Requires "addr" to be the start of a block, and returns "TRUE" iff
250   // the block is an object. Assumes (and verifies in non-product
251   // builds) that addr is in the allocated part of the heap and is
252   // the start of a chunk.
253   bool block_is_obj(const HeapWord* addr) const;
254 
255   // Section on TLAB's.
256   virtual size_t tlab_capacity(Thread* thr) const;
257   virtual size_t tlab_used(Thread* thr) const;
258   virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
259   virtual HeapWord* allocate_new_tlab(size_t min_size,
260                                       size_t requested_size,
261                                       size_t* actual_size);
262 
263   // The "requestor" generation is performing some garbage collection
264   // action for which it would be useful to have scratch space.  The
265   // requestor promises to allocate no more than "max_alloc_words" in any
266   // older generation (via promotion say.)   Any blocks of space that can
267   // be provided are returned as a list of ScratchBlocks, sorted by
268   // decreasing size.
269   ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words);
270   // Allow each generation to reset any scratch space that it has
271   // contributed as it needs.
272   void release_scratch();
273 
274   // Ensure parsability: override
275   virtual void ensure_parsability(bool retire_tlabs);
276 
277   // Total number of full collections completed.
278   unsigned int total_full_collections_completed() {
279     assert(_full_collections_completed <= _total_full_collections,
280            "Can't complete more collections than were started");
281     return _full_collections_completed;
282   }
283 
284   // Update above counter, as appropriate, at the end of a stop-world GC cycle
285   unsigned int update_full_collections_completed();
286 
287   // Update the gc statistics for each generation.
288   void update_gc_stats(Generation* current_generation, bool full) {
289     _old_gen->update_gc_stats(current_generation, full);
290   }
291 
292   bool no_gc_in_progress() { return !is_gc_active(); }
293 
294   // Override.
295   void prepare_for_verify();
296 
297   // Override.
298   void verify(VerifyOption option);
299 
300   // Override.
301   virtual void print_on(outputStream* st) const;
302   virtual void gc_threads_do(ThreadClosure* tc) const;
303   virtual void print_tracing_info() const;
304 
305   // Used to print information about locations in the hs_err file.
306   virtual bool print_location(outputStream* st, void* addr) const;
307 
308   void print_heap_change(const PreGenGCValues& pre_gc_values) const;
309 
310   // The functions below are helper functions that a subclass of
311   // "CollectedHeap" can use in the implementation of its virtual
312   // functions.
313 
314   class GenClosure : public StackObj {
315    public:
316     virtual void do_generation(Generation* gen) = 0;
317   };
318 
319   // Apply "cl.do_generation" to all generations in the heap
320   // If "old_to_young" determines the order.
321   void generation_iterate(GenClosure* cl, bool old_to_young);
322 
323   // Return "true" if all generations have reached the
324   // maximal committed limit that they can reach, without a garbage
325   // collection.
326   virtual bool is_maximal_no_gc() const;
327 
328   // This function returns the CardTableRS object that allows us to scan
329   // generations in a fully generational heap.
330   CardTableRS* rem_set() { return _rem_set; }
331 
332   // Convenience function to be used in situations where the heap type can be
333   // asserted to be this type.
334   static GenCollectedHeap* heap();
335 
336   SlidingForwarding* forwarding() const {
337     return _forwarding;
338   }
339 
340   // The ScanningOption determines which of the roots
341   // the closure is applied to:
342   // "SO_None" does none;
343   enum ScanningOption {
344     SO_None                =  0x0,
345     SO_AllCodeCache        =  0x8,
346     SO_ScavengeCodeCache   = 0x10
347   };
348 
349  protected:
350   void process_roots(ScanningOption so,
351                      OopClosure* strong_roots,
352                      CLDClosure* strong_cld_closure,
353                      CLDClosure* weak_cld_closure,
354                      CodeBlobToOopClosure* code_roots);
355 
356   virtual void gc_prologue(bool full);
357   virtual void gc_epilogue(bool full);
358 
359  public:
360   void full_process_roots(bool is_adjust_phase,
361                           ScanningOption so,
362                           bool only_strong_roots,
363                           OopClosure* root_closure,
364                           CLDClosure* cld_closure);
365 
366   // Apply "root_closure" to all the weak roots of the system.
367   // These include JNI weak roots, string table,
368   // and referents of reachable weak refs.
369   void gen_process_weak_roots(OopClosure* root_closure);
370 
371   // Set the saved marks of generations, if that makes sense.
372   // In particular, if any generation might iterate over the oops
373   // in other generations, it should call this method.
374   void save_marks();
375 
376   // Returns "true" iff no allocations have occurred since the last
377   // call to "save_marks".
378   bool no_allocs_since_save_marks();
379 
380   // Returns true if an incremental collection is likely to fail.
381   // We optionally consult the young gen, if asked to do so;
382   // otherwise we base our answer on whether the previous incremental
383   // collection attempt failed with no corrective action as of yet.
384   bool incremental_collection_will_fail(bool consult_young) {
385     // The first disjunct remembers if an incremental collection failed, even
386     // when we thought (second disjunct) that it would not.
387     return incremental_collection_failed() ||
388            (consult_young && !_young_gen->collection_attempt_is_safe());
389   }
390 
391   // If a generation bails out of an incremental collection,
392   // it sets this flag.
393   bool incremental_collection_failed() const {
394     return _incremental_collection_failed;
395   }
396   void set_incremental_collection_failed() {
397     _incremental_collection_failed = true;
398   }
399   void clear_incremental_collection_failed() {
400     _incremental_collection_failed = false;
401   }
402 
403   // Promotion of obj into gen failed.  Try to promote obj to higher
404   // gens in ascending order; return the new location of obj if successful.
405   // Otherwise, try expand-and-allocate for obj in both the young and old
406   // generation; return the new location of obj if successful.  Otherwise, return NULL.
407   oop handle_failed_promotion(Generation* old_gen,
408                               oop obj,
409                               size_t obj_size);
410 
411 
412 private:
413   // Return true if an allocation should be attempted in the older generation
414   // if it fails in the younger generation.  Return false, otherwise.
415   bool should_try_older_generation_allocation(size_t word_size) const;
416 
417   // Try to allocate space by expanding the heap.
418   HeapWord* expand_heap_and_allocate(size_t size, bool is_tlab);
419 
420   HeapWord* mem_allocate_work(size_t size,
421                               bool is_tlab,
422                               bool* gc_overhead_limit_was_exceeded);
423 
424 #if INCLUDE_SERIALGC
425   // For use by mark-sweep.  As implemented, mark-sweep-compact is global
426   // in an essential way: compaction is performed across generations, by
427   // iterating over spaces.
428   void prepare_for_compaction();
429 #endif
430 
431   // Perform a full collection of the generations up to and including max_generation.
432   // This is the low level interface used by the public versions of
433   // collect() and collect_locked(). Caller holds the Heap_lock on entry.
434   void collect_locked(GCCause::Cause cause, GenerationType max_generation);
435 
436   // Save the tops of the spaces in all generations
437   void record_gen_tops_before_GC() PRODUCT_RETURN;
438 
439   // Return true if we need to perform full collection.
440   bool should_do_full_collection(size_t size, bool full,
441                                  bool is_tlab, GenerationType max_gen) const;
442 };
443 
444 #endif // SHARE_GC_SHARED_GENCOLLECTEDHEAP_HPP