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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   virtual void do_full_collection(bool clear_all_soft_refs);
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   virtual jint initialize();
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();
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   virtual SoftRefPolicy* soft_ref_policy() { 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;
178   size_t used() const;
179 
180   // Save the "used_region" for both generations.
181   void save_used_regions();
182 
183   size_t max_capacity() const;
184 
185   HeapWord* mem_allocate(size_t size, bool*  gc_overhead_limit_was_exceeded);
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   virtual void collect(GCCause::Cause cause);
191 
192   // Perform a full collection of generations up to and including max_generation.
193   // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry.
194   void collect(GCCause::Cause cause, GenerationType max_generation);
195 
196   // Returns "TRUE" iff "p" points into the committed areas of the heap.
197   // The methods is_in() and is_in_youngest() may be expensive to compute
198   // in general, so, to prevent their inadvertent use in product jvm's, we
199   // restrict their use to assertion checking or verification only.
200   bool is_in(const void* p) const;
201 
202   // Returns true if the reference is to an object in the reserved space
203   // for the young generation.
204   // Assumes the young gen address range is less than that of the old gen.
205   bool is_in_young(oop p) const;
206 
207   virtual bool requires_barriers(stackChunkOop obj) const;
208 
209 #ifdef ASSERT
210   bool is_in_partial_collection(const void* p);
211 #endif
212 
213   // Optimized nmethod scanning support routines
214   virtual void register_nmethod(nmethod* nm);
215   virtual void unregister_nmethod(nmethod* nm);
216   virtual void verify_nmethod(nmethod* nm);
217   virtual void flush_nmethod(nmethod* nm);
218 
219   void prune_scavengable_nmethods();
220 
221   // Iteration functions.
222   void oop_iterate(OopIterateClosure* cl);
223   void object_iterate(ObjectClosure* cl);
224   Space* space_containing(const void* addr) const;
225 
226   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
227   // each address in the (reserved) heap is a member of exactly
228   // one block.  The defining characteristic of a block is that it is
229   // possible to find its size, and thus to progress forward to the next
230   // block.  (Blocks may be of different sizes.)  Thus, blocks may
231   // represent Java objects, or they might be free blocks in a
232   // free-list-based heap (or subheap), as long as the two kinds are
233   // distinguishable and the size of each is determinable.
234 
235   // Returns the address of the start of the "block" that contains the
236   // address "addr".  We say "blocks" instead of "object" since some heaps
237   // may not pack objects densely; a chunk may either be an object or a
238   // non-object.
239   HeapWord* block_start(const void* addr) const;
240 
241   // Requires "addr" to be the start of a block, and returns "TRUE" iff
242   // the block is an object. Assumes (and verifies in non-product
243   // builds) that addr is in the allocated part of the heap and is
244   // the start of a chunk.
245   bool block_is_obj(const HeapWord* addr) const;
246 
247   // Section on TLAB's.
248   virtual size_t tlab_capacity(Thread* thr) const;
249   virtual size_t tlab_used(Thread* thr) const;
250   virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
251   virtual HeapWord* allocate_new_tlab(size_t min_size,
252                                       size_t requested_size,
253                                       size_t* actual_size);
254 
255   // The "requestor" generation is performing some garbage collection
256   // action for which it would be useful to have scratch space.  The
257   // requestor promises to allocate no more than "max_alloc_words" in any
258   // older generation (via promotion say.)   Any blocks of space that can
259   // be provided are returned as a list of ScratchBlocks, sorted by
260   // decreasing size.
261   ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words);
262   // Allow each generation to reset any scratch space that it has
263   // contributed as it needs.
264   void release_scratch();
265 
266   // Ensure parsability: override
267   virtual void ensure_parsability(bool retire_tlabs);
268 
269   // Total number of full collections completed.
270   unsigned int total_full_collections_completed() {
271     assert(_full_collections_completed <= _total_full_collections,
272            "Can't complete more collections than were started");
273     return _full_collections_completed;
274   }
275 
276   // Update above counter, as appropriate, at the end of a stop-world GC cycle
277   unsigned int update_full_collections_completed();
278 
279   // Update the gc statistics for each generation.
280   void update_gc_stats(Generation* current_generation, bool full) {
281     _old_gen->update_gc_stats(current_generation, full);
282   }
283 
284   bool no_gc_in_progress() { return !is_gc_active(); }
285 
286   // Override.
287   void prepare_for_verify();
288 
289   // Override.
290   void verify(VerifyOption option);
291 
292   // Override.
293   virtual void print_on(outputStream* st) const;
294   virtual void gc_threads_do(ThreadClosure* tc) const;
295   virtual void print_tracing_info() const;
296 
297   // Used to print information about locations in the hs_err file.
298   virtual bool print_location(outputStream* st, void* addr) const;
299 
300   void print_heap_change(const PreGenGCValues& pre_gc_values) const;
301 
302   // The functions below are helper functions that a subclass of
303   // "CollectedHeap" can use in the implementation of its virtual
304   // functions.
305 
306   class GenClosure : public StackObj {
307    public:
308     virtual void do_generation(Generation* gen) = 0;
309   };
310 
311   // Apply "cl.do_generation" to all generations in the heap
312   // If "old_to_young" determines the order.
313   void generation_iterate(GenClosure* cl, bool old_to_young);
314 
315   // Return "true" if all generations have reached the
316   // maximal committed limit that they can reach, without a garbage
317   // collection.
318   virtual bool is_maximal_no_gc() const;
319 
320   // This function returns the CardTableRS object that allows us to scan
321   // generations in a fully generational heap.
322   CardTableRS* rem_set() { return _rem_set; }
323 
324   // Convenience function to be used in situations where the heap type can be
325   // asserted to be this type.
326   static GenCollectedHeap* heap();
327 
328   SlidingForwarding* forwarding() const {
329     return _forwarding;
330   }
331 
332   // The ScanningOption determines which of the roots
333   // the closure is applied to:
334   // "SO_None" does none;
335   enum ScanningOption {
336     SO_None                =  0x0,
337     SO_AllCodeCache        =  0x8,
338     SO_ScavengeCodeCache   = 0x10
339   };
340 
341  protected:
342   void process_roots(ScanningOption so,
343                      OopClosure* strong_roots,
344                      CLDClosure* strong_cld_closure,
345                      CLDClosure* weak_cld_closure,
346                      CodeBlobToOopClosure* code_roots);
347 
348   virtual void gc_prologue(bool full);
349   virtual void gc_epilogue(bool full);
350 
351  public:
352   void full_process_roots(bool is_adjust_phase,
353                           ScanningOption so,
354                           bool only_strong_roots,
355                           OopClosure* root_closure,
356                           CLDClosure* cld_closure);
357 
358   // Apply "root_closure" to all the weak roots of the system.
359   // These include JNI weak roots, string table,
360   // and referents of reachable weak refs.
361   void gen_process_weak_roots(OopClosure* root_closure);
362 
363   // Set the saved marks of generations, if that makes sense.
364   // In particular, if any generation might iterate over the oops
365   // in other generations, it should call this method.
366   void save_marks();
367 
368   // Returns "true" iff no allocations have occurred since the last
369   // call to "save_marks".
370   bool no_allocs_since_save_marks();
371 
372   // Returns true if an incremental collection is likely to fail.
373   // We optionally consult the young gen, if asked to do so;
374   // otherwise we base our answer on whether the previous incremental
375   // collection attempt failed with no corrective action as of yet.
376   bool incremental_collection_will_fail(bool consult_young) {
377     // The first disjunct remembers if an incremental collection failed, even
378     // when we thought (second disjunct) that it would not.
379     return incremental_collection_failed() ||
380            (consult_young && !_young_gen->collection_attempt_is_safe());
381   }
382 
383   // If a generation bails out of an incremental collection,
384   // it sets this flag.
385   bool incremental_collection_failed() const {
386     return _incremental_collection_failed;
387   }
388   void set_incremental_collection_failed() {
389     _incremental_collection_failed = true;
390   }
391   void clear_incremental_collection_failed() {
392     _incremental_collection_failed = false;
393   }
394 
395   // Promotion of obj into gen failed.  Try to promote obj to higher
396   // gens in ascending order; return the new location of obj if successful.
397   // Otherwise, try expand-and-allocate for obj in both the young and old
398   // generation; return the new location of obj if successful.  Otherwise, return NULL.
399   oop handle_failed_promotion(Generation* old_gen,
400                               oop obj,
401                               size_t obj_size);
402 
403 
404 private:
405   // Return true if an allocation should be attempted in the older generation
406   // if it fails in the younger generation.  Return false, otherwise.
407   bool should_try_older_generation_allocation(size_t word_size) const;
408 
409   // Try to allocate space by expanding the heap.
410   HeapWord* expand_heap_and_allocate(size_t size, bool is_tlab);
411 
412   HeapWord* mem_allocate_work(size_t size,
413                               bool is_tlab,
414                               bool* gc_overhead_limit_was_exceeded);
415 
416 #if INCLUDE_SERIALGC
417   // For use by mark-sweep.  As implemented, mark-sweep-compact is global
418   // in an essential way: compaction is performed across generations, by
419   // iterating over spaces.
420   void prepare_for_compaction();
421 #endif
422 
423   // Save the tops of the spaces in all generations
424   void record_gen_tops_before_GC() PRODUCT_RETURN;
425 
426   // Return true if we need to perform full collection.
427   bool should_do_full_collection(size_t size, bool full,
428                                  bool is_tlab, GenerationType max_gen) const;
429 };
430 
431 #endif // SHARE_GC_SHARED_GENCOLLECTEDHEAP_HPP