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 /*

  * Copyright 2000-2009 Sun Microsystems, Inc.  All Rights Reserved.

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

  * 2 along with this work; if not, write to the Free Software Foundation,

  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

  *

  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

  * CA 95054 USA or visit www.sun.com if you need additional information or

  * have any questions.

  *

  */

 class SubTasksDone;

 // A "GenCollectedHeap" is a SharedHeap that uses generational

 // collection.  It is represented with a sequence of Generation's.

 class GenCollectedHeap : public SharedHeap {

   friend class GenCollectorPolicy;

   friend class Generation;

   friend class DefNewGeneration;

   friend class TenuredGeneration;

   friend class ConcurrentMarkSweepGeneration;

   friend class CMSCollector;

   friend class GenMarkSweep;

   friend class VM_GenCollectForAllocation;

   friend class VM_GenCollectForPermanentAllocation;

   friend class VM_GenCollectFull;

   friend class VM_GenCollectFullConcurrent;

   friend class VM_GC_HeapInspection;

   friend class VM_HeapDumper;

   friend class HeapInspection;

   friend class GCCauseSetter;

   friend class VMStructs;

 public:

   enum SomeConstants {

     max_gens = 10

   };

   friend class VM_PopulateDumpSharedSpace;

  protected:

   // Fields:

   static GenCollectedHeap* _gch;

  private:

   int _n_gens;

   Generation* _gens[max_gens];

   GenerationSpec** _gen_specs;

   // The generational collector policy.

   GenCollectorPolicy* _gen_policy;

   // If a generation would bail out of an incremental collection,

   // it sets this flag.  If the flag is set, satisfy_failed_allocation

   // will attempt allocating in all generations before doing a full GC.

   bool _incremental_collection_will_fail;

   bool _last_incremental_collection_failed;

   // In support of ExplicitGCInvokesConcurrent functionality

   unsigned int _full_collections_completed;

   // Data structure for claiming the (potentially) parallel tasks in

   // (gen-specific) strong roots processing.

   SubTasksDone* _gen_process_strong_tasks;

   // In block contents verification, the number of header words to skip

   NOT_PRODUCT(static size_t _skip_header_HeapWords;)

   // GC is not allowed during the dump of the shared classes.  Keep track

   // of this in order to provide an reasonable error message when terminating.

   bool _preloading_shared_classes;

 protected:

   // Directs each generation up to and including "collectedGen" to recompute

   // its desired size.

   void compute_new_generation_sizes(int collectedGen);

   // Helper functions for allocation

   HeapWord* attempt_allocation(size_t size,

                                bool   is_tlab,

                                bool   first_only);

   // Helper function for two callbacks below.

   // Considers collection of the first max_level+1 generations.

   void do_collection(bool   full,

                      bool   clear_all_soft_refs,

                      size_t size,

                      bool   is_tlab,

                      int    max_level);

   // Callback from VM_GenCollectForAllocation operation.

   // This function does everything necessary/possible to satisfy an

   // allocation request that failed in the youngest generation that should

   // have handled it (including collection, expansion, etc.)

   HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab);

   // Callback from VM_GenCollectFull operation.

   // Perform a full collection of the first max_level+1 generations.

   void do_full_collection(bool clear_all_soft_refs, int max_level);

   // Does the "cause" of GC indicate that

   // we absolutely __must__ clear soft refs?

   bool must_clear_all_soft_refs();

 public:

   GenCollectedHeap(GenCollectorPolicy *policy);

   GCStats* gc_stats(int level) const;

   // Returns JNI_OK on success

   virtual jint initialize();

   char* allocate(size_t alignment, PermanentGenerationSpec* perm_gen_spec,

                  size_t* _total_reserved, int* _n_covered_regions,

                  ReservedSpace* heap_rs);

   // Does operations required after initialization has been done.

   void post_initialize();

   // Initialize ("weak") refs processing support

   virtual void ref_processing_init();

   virtual CollectedHeap::Name kind() const {

     return CollectedHeap::GenCollectedHeap;

   }

   // The generational collector policy.

   GenCollectorPolicy* gen_policy() const { return _gen_policy; }

   // Adaptive size policy

   virtual AdaptiveSizePolicy* size_policy() {

     return gen_policy()->size_policy();

   }

   size_t capacity() const;

   size_t used() const;

   // Save the "used_region" for generations level and lower,

   // and, if perm is true, for perm gen.

   void save_used_regions(int level, bool perm);

   size_t max_capacity() const;

   HeapWord* mem_allocate(size_t size,

                          bool   is_large_noref,

                          bool   is_tlab,

                          bool*  gc_overhead_limit_was_exceeded);

   // We may support a shared contiguous allocation area, if the youngest

   // generation does.

   bool supports_inline_contig_alloc() const;

   HeapWord** top_addr() const;

   HeapWord** end_addr() const;

   // Return an estimate of the maximum allocation that could be performed

   // without triggering any collection activity.  In a generational

   // collector, for example, this is probably the largest allocation that

   // could be supported in the youngest generation.  It is "unsafe" because

   // no locks are taken; the result should be treated as an approximation,

   // not a guarantee.

   size_t unsafe_max_alloc();

   // Does this heap support heap inspection? (+PrintClassHistogram)

   virtual bool supports_heap_inspection() const { return true; }

   // Perform a full collection of the heap; intended for use in implementing

   // "System.gc". This implies as full a collection as the CollectedHeap

   // supports. Caller does not hold the Heap_lock on entry.

   void collect(GCCause::Cause cause);

   // This interface assumes that it's being called by the

   // vm thread. It collects the heap assuming that the

   // heap lock is already held and that we are executing in

   // the context of the vm thread.

   void collect_as_vm_thread(GCCause::Cause cause);

   // The same as above but assume that the caller holds the Heap_lock.

   void collect_locked(GCCause::Cause cause);

   // Perform a full collection of the first max_level+1 generations.

   // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry.

   void collect(GCCause::Cause cause, int max_level);

   // Returns "TRUE" iff "p" points into the allocated area of the heap.

   // The methods is_in(), is_in_closed_subset() and is_in_youngest() may

   // be expensive to compute in general, so, to prevent

   // their inadvertent use in product jvm's, we restrict their use to

   // assertion checking or verification only.

   bool is_in(const void* p) const;

   // override

   bool is_in_closed_subset(const void* p) const {

     if (UseConcMarkSweepGC) {

       return is_in_reserved(p);

     } else {

       return is_in(p);

     }

   }

   // Returns "TRUE" iff "p" points into the youngest generation.

   bool is_in_youngest(void* p);

   // Iteration functions.

   void oop_iterate(OopClosure* cl);

   void oop_iterate(MemRegion mr, OopClosure* cl);

   void object_iterate(ObjectClosure* cl);

   void safe_object_iterate(ObjectClosure* cl);

   void object_iterate_since_last_GC(ObjectClosure* cl);

   Space* space_containing(const void* addr) const;

   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,

   // each address in the (reserved) heap is a member of exactly

   // one block.  The defining characteristic of a block is that it is

   // possible to find its size, and thus to progress forward to the next

   // block.  (Blocks may be of different sizes.)  Thus, blocks may

   // represent Java objects, or they might be free blocks in a

   // free-list-based heap (or subheap), as long as the two kinds are

   // distinguishable and the size of each is determinable.

   // Returns the address of the start of the "block" that contains the

   // address "addr".  We say "blocks" instead of "object" since some heaps

   // may not pack objects densely; a chunk may either be an object or a

   // non-object.

   virtual HeapWord* block_start(const void* addr) const;

   // Requires "addr" to be the start of a chunk, and returns its size.

   // "addr + size" is required to be the start of a new chunk, or the end

   // of the active area of the heap. Assumes (and verifies in non-product

   // builds) that addr is in the allocated part of the heap and is

   // the start of a chunk.

   virtual size_t block_size(const HeapWord* addr) const;

   // Requires "addr" to be the start of a block, and returns "TRUE" iff

   // the block is an object. Assumes (and verifies in non-product

   // builds) that addr is in the allocated part of the heap and is

   // the start of a chunk.

   virtual bool block_is_obj(const HeapWord* addr) const;

   // Section on TLAB's.

   virtual bool supports_tlab_allocation() const;

   virtual size_t tlab_capacity(Thread* thr) const;

   virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;

   virtual HeapWord* allocate_new_tlab(size_t size);

   // Can a compiler initialize a new object without store barriers?

   // This permission only extends from the creation of a new object

   // via a TLAB up to the first subsequent safepoint.

   virtual bool can_elide_tlab_store_barriers() const {

     return true;

   }

   virtual bool card_mark_must_follow_store() const {

     return UseConcMarkSweepGC;

   }

   // We don't need barriers for stores to objects in the

   // young gen and, a fortiori, for initializing stores to

   // objects therein. This applies to {DefNew,ParNew}+{Tenured,CMS}

   // only and may need to be re-examined in case other

   // kinds of collectors are implemented in the future.

   virtual bool can_elide_initializing_store_barrier(oop new_obj) {

     // We wanted to assert that:-

     // assert(UseParNewGC || UseSerialGC || UseConcMarkSweepGC,

     //       "Check can_elide_initializing_store_barrier() for this collector");

     // but unfortunately the flag UseSerialGC need not necessarily always

     // be set when DefNew+Tenured are being used.

     return is_in_youngest((void*)new_obj);

   }

   // Can a compiler elide a store barrier when it writes

   // a permanent oop into the heap?  Applies when the compiler

   // is storing x to the heap, where x->is_perm() is true.

   virtual bool can_elide_permanent_oop_store_barriers() const {

     // CMS needs to see all, even intra-generational, ref updates.

     return !UseConcMarkSweepGC;

   }

   // The "requestor" generation is performing some garbage collection

   // action for which it would be useful to have scratch space.  The

   // requestor promises to allocate no more than "max_alloc_words" in any

   // older generation (via promotion say.)   Any blocks of space that can

   // be provided are returned as a list of ScratchBlocks, sorted by

   // decreasing size.

   ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words);

   // Allow each generation to reset any scratch space that it has

   // contributed as it needs.

   void release_scratch();

   size_t large_typearray_limit();

   // Ensure parsability: override

   virtual void ensure_parsability(bool retire_tlabs);

   // Time in ms since the longest time a collector ran in

   // in any generation.

   virtual jlong millis_since_last_gc();

   // Total number of full collections completed.

   unsigned int total_full_collections_completed() {

     assert(_full_collections_completed <= _total_full_collections,

            "Can't complete more collections than were started");

     return _full_collections_completed;

   }

   // Update above counter, as appropriate, at the end of a stop-world GC cycle

   unsigned int update_full_collections_completed();

   // Update above counter, as appropriate, at the end of a concurrent GC cycle

   unsigned int update_full_collections_completed(unsigned int count);

   // Update "time of last gc" for all constituent generations

   // to "now".

   void update_time_of_last_gc(jlong now) {

     for (int i = 0; i < _n_gens; i++) {

       _gens[i]->update_time_of_last_gc(now);

     }

     perm_gen()->update_time_of_last_gc(now);

   }

   // Update the gc statistics for each generation.

   // "level" is the level of the lastest collection

   void update_gc_stats(int current_level, bool full) {

     for (int i = 0; i < _n_gens; i++) {

       _gens[i]->update_gc_stats(current_level, full);

     }

     perm_gen()->update_gc_stats(current_level, full);

   }

   // Override.

   bool no_gc_in_progress() { return !is_gc_active(); }

   // Override.

   void prepare_for_verify();

   // Override.

   void verify(bool allow_dirty, bool silent, bool /* option */);

   // Override.

   void print() const;

   void print_on(outputStream* st) const;

   virtual void print_gc_threads_on(outputStream* st) const;

   virtual void gc_threads_do(ThreadClosure* tc) const;

   virtual void print_tracing_info() const;

   // PrintGC, PrintGCDetails support

   void print_heap_change(size_t prev_used) const;

   void print_perm_heap_change(size_t perm_prev_used) const;

   // The functions below are helper functions that a subclass of

   // "CollectedHeap" can use in the implementation of its virtual

   // functions.

   class GenClosure : public StackObj {

    public:

     virtual void do_generation(Generation* gen) = 0;

   };

   // Apply "cl.do_generation" to all generations in the heap (not including

   // the permanent generation).  If "old_to_young" determines the order.

   void generation_iterate(GenClosure* cl, bool old_to_young);

   void space_iterate(SpaceClosure* cl);

   // Return "true" if all generations (but perm) have reached the

   // maximal committed limit that they can reach, without a garbage

   // collection.

   virtual bool is_maximal_no_gc() const;

   // Return the generation before "gen", or else NULL.

   Generation* prev_gen(Generation* gen) const {

     int l = gen->level();

     if (l == 0) return NULL;

     else return _gens[l-1];

   }

   // Return the generation after "gen", or else NULL.

   Generation* next_gen(Generation* gen) const {

     int l = gen->level() + 1;

     if (l == _n_gens) return NULL;

     else return _gens[l];

   }

   Generation* get_gen(int i) const {

     if (i >= 0 && i < _n_gens)

       return _gens[i];

     else

       return NULL;

   }

   int n_gens() const {

     assert(_n_gens == gen_policy()->number_of_generations(), "Sanity");

     return _n_gens;

   }

   // Convenience function to be used in situations where the heap type can be

   // asserted to be this type.

   static GenCollectedHeap* heap();

   void set_par_threads(int t);

   // Invoke the "do_oop" method of one of the closures "not_older_gens"

   // or "older_gens" on root locations for the generation at

   // "level".  (The "older_gens" closure is used for scanning references

   // from older generations; "not_older_gens" is used everywhere else.)

   // If "younger_gens_as_roots" is false, younger generations are

   // not scanned as roots; in this case, the caller must be arranging to

   // scan the younger generations itself.  (For example, a generation might

   // explicitly mark reachable objects in younger generations, to avoid

   // excess storage retention.)  If "collecting_perm_gen" is false, then

   // roots that may only contain references to permGen objects are not

   // scanned. The "so" argument determines which of the roots

   // the closure is applied to:

   // "SO_None" does none;

   // "SO_AllClasses" applies the closure to all entries in the SystemDictionary;

   // "SO_SystemClasses" to all the "system" classes and loaders;

   // "SO_Symbols_and_Strings" applies the closure to all entries in

   // SymbolsTable and StringTable.

   void gen_process_strong_roots(int level,

                                 bool younger_gens_as_roots,

                                 // The remaining arguments are in an order

                                 // consistent with SharedHeap::process_strong_roots:

                                 bool activate_scope,

                                 bool collecting_perm_gen,

                                 SharedHeap::ScanningOption so,

                                 OopsInGenClosure* not_older_gens,

                                 bool do_code_roots,

                                 OopsInGenClosure* older_gens);

   // Apply "blk" to all the weak roots of the system.  These include

   // JNI weak roots, the code cache, system dictionary, symbol table,

   // string table, and referents of reachable weak refs.

   void gen_process_weak_roots(OopClosure* root_closure,

                               CodeBlobClosure* code_roots,

                               OopClosure* non_root_closure);

   // Set the saved marks of generations, if that makes sense.

   // In particular, if any generation might iterate over the oops

   // in other generations, it should call this method.

   void save_marks();

   // Apply "cur->do_oop" or "older->do_oop" to all the oops in objects

   // allocated since the last call to save_marks in generations at or above

   // "level" (including the permanent generation.)  The "cur" closure is

   // applied to references in the generation at "level", and the "older"

   // closure to older (and permanent) generations.

 #define GCH_SINCE_SAVE_MARKS_ITERATE_DECL(OopClosureType, nv_suffix)    \

   void oop_since_save_marks_iterate(int level,                          \

                                     OopClosureType* cur,                \

                                     OopClosureType* older);

   ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DECL)

 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DECL

   // Returns "true" iff no allocations have occurred in any generation at

   // "level" or above (including the permanent generation) since the last

   // call to "save_marks".

   bool no_allocs_since_save_marks(int level);

   // If a generation bails out of an incremental collection,

   // it sets this flag.

   bool incremental_collection_will_fail() {

     return _incremental_collection_will_fail;

   }

   void set_incremental_collection_will_fail() {

     _incremental_collection_will_fail = true;

   }

   void clear_incremental_collection_will_fail() {

     _incremental_collection_will_fail = false;

   }

   bool last_incremental_collection_failed() const {

     return _last_incremental_collection_failed;

   }

   void set_last_incremental_collection_failed() {

     _last_incremental_collection_failed = true;

   }

   void clear_last_incremental_collection_failed() {

     _last_incremental_collection_failed = false;

   }

   // Promotion of obj into gen failed.  Try to promote obj to higher non-perm

   // gens in ascending order; return the new location of obj if successful.

   // Otherwise, try expand-and-allocate for obj in each generation starting at

   // gen; return the new location of obj if successful.  Otherwise, return NULL.

   oop handle_failed_promotion(Generation* gen,

                               oop obj,

                               size_t obj_size);

 private:

   // Accessor for memory state verification support

   NOT_PRODUCT(

     static size_t skip_header_HeapWords() { return _skip_header_HeapWords; }

   )

   // Override

   void check_for_non_bad_heap_word_value(HeapWord* addr,

     size_t size) PRODUCT_RETURN;

   // For use by mark-sweep.  As implemented, mark-sweep-compact is global

   // in an essential way: compaction is performed across generations, by

   // iterating over spaces.

   void prepare_for_compaction();

   // Perform a full collection of the first max_level+1 generations.

   // This is the low level interface used by the public versions of

   // collect() and collect_locked(). Caller holds the Heap_lock on entry.

   void collect_locked(GCCause::Cause cause, int max_level);

   // Returns success or failure.

   bool create_cms_collector();

   // In support of ExplicitGCInvokesConcurrent functionality

   bool should_do_concurrent_full_gc(GCCause::Cause cause);

   void collect_mostly_concurrent(GCCause::Cause cause);

   // Save the tops of the spaces in all generations

   void record_gen_tops_before_GC() PRODUCT_RETURN;

 protected:

   virtual void gc_prologue(bool full);

   virtual void gc_epilogue(bool full);

 public:

   virtual void preload_and_dump(TRAPS) KERNEL_RETURN;

 };