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   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   * published by the Free Software Foundation.
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   * 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
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  #ifndef SHARE_GC_SHARED_GENCOLLECTEDHEAP_HPP
  #define SHARE_GC_SHARED_GENCOLLECTEDHEAP_HPP
  
  #include "gc/shared/collectedHeap.hpp"
  #include "gc/shared/generation.hpp"
  #include "gc/shared/oopStorageParState.hpp"
  #include "gc/shared/preGCValues.hpp"
  #include "gc/shared/softRefGenPolicy.hpp"
  
  class AdaptiveSizePolicy;
  class CardTableRS;
  class GCPolicyCounters;
  class GenerationSpec;
  class StrongRootsScope;
  class SubTasksDone;
  class WorkGang;
  
  // A "GenCollectedHeap" is a CollectedHeap that uses generational
  // collection.  It has two generations, young and old.
  class GenCollectedHeap : public CollectedHeap {
    friend class Generation;
    friend class DefNewGeneration;
    friend class TenuredGeneration;
    friend class GenMarkSweep;
    friend class VM_GenCollectForAllocation;
    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:
    friend class VM_PopulateDumpSharedSpace;
  
    enum GenerationType {
      YoungGen,
      OldGen
    };
  
  protected:
    Generation* _young_gen;
    Generation* _old_gen;
  
  private:
    GenerationSpec* _young_gen_spec;
    GenerationSpec* _old_gen_spec;
  
    // The singleton CardTable Remembered Set.
    CardTableRS* _rem_set;
  
    SoftRefGenPolicy _soft_ref_gen_policy;
  
    // The sizing of the heap is controlled by a sizing policy.
    AdaptiveSizePolicy* _size_policy;
  
    GCPolicyCounters* _gc_policy_counters;
  
    // Indicates that the most recent previous incremental collection failed.
    // The flag is cleared when an action is taken that might clear the
    // condition that caused that incremental collection to fail.
    bool _incremental_collection_failed;
  
    // In support of ExplicitGCInvokesConcurrent functionality
    unsigned int _full_collections_completed;
  
    // Collects the given generation.
    void collect_generation(Generation* gen, bool full, size_t size, bool is_tlab,
                            bool run_verification, bool clear_soft_refs);
  
    // Reserve aligned space for the heap as needed by the contained generations.
    ReservedHeapSpace allocate(size_t alignment);
  
    // Initialize ("weak") refs processing support
    void ref_processing_init();
  
    PreGenGCValues get_pre_gc_values() const;
  
  protected:
  
    GCMemoryManager* _young_manager;
    GCMemoryManager* _old_manager;
  
    // 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,
                       GenerationType max_generation);
  
    // 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.
    virtual void do_full_collection(bool clear_all_soft_refs);
    void do_full_collection(bool clear_all_soft_refs, GenerationType max_generation);
  
    // Does the "cause" of GC indicate that
    // we absolutely __must__ clear soft refs?
    bool must_clear_all_soft_refs();
  
    GenCollectedHeap(Generation::Name young,
                     Generation::Name old,
                     const char* policy_counters_name);
  
  public:
  
    // Returns JNI_OK on success
    virtual jint initialize();
    virtual CardTableRS* create_rem_set(const MemRegion& reserved_region);
  
    void initialize_size_policy(size_t init_eden_size,
                                size_t init_promo_size,
                                size_t init_survivor_size);
  
    // Does operations required after initialization has been done.
    void post_initialize();
  
    Generation* young_gen() const { return _young_gen; }
    Generation* old_gen()   const { return _old_gen; }
  
    bool is_young_gen(const Generation* gen) const { return gen == _young_gen; }
    bool is_old_gen(const Generation* gen) const { return gen == _old_gen; }
  
    MemRegion reserved_region() const { return _reserved; }
    bool is_in_reserved(const void* addr) const { return _reserved.contains(addr); }
  
    GenerationSpec* young_gen_spec() const;
    GenerationSpec* old_gen_spec() const;
  
    virtual SoftRefPolicy* soft_ref_policy() { return &_soft_ref_gen_policy; }
  
    // Adaptive size policy
    virtual AdaptiveSizePolicy* size_policy() {
      return _size_policy;
    }
  
    // Performance Counter support
    GCPolicyCounters* counters()     { return _gc_policy_counters; }
  
    size_t capacity() const;
    size_t used() const;
  
    // Save the "used_region" for both generations.
    void save_used_regions();
  
    size_t max_capacity() const;
  
    HeapWord* mem_allocate(size_t size, 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* volatile* top_addr() const;
    HeapWord** end_addr() const;
  
    // 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.
    virtual void collect(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 generations up to and including max_generation.
    // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry.
    void collect(GCCause::Cause cause, GenerationType max_generation);
  
    // Returns "TRUE" iff "p" points into the committed areas of the heap.
    // The methods is_in() 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;
  
    // Returns true if the reference is to an object in the reserved space
    // for the young generation.
    // Assumes the the young gen address range is less than that of the old gen.
    bool is_in_young(oop p);
  
  #ifdef ASSERT
    bool is_in_partial_collection(const void* p);
  #endif
  
    // Optimized nmethod scanning support routines
    virtual void register_nmethod(nmethod* nm);
    virtual void unregister_nmethod(nmethod* nm);
    virtual void verify_nmethod(nmethod* nm);
    virtual void flush_nmethod(nmethod* nm);
  
    void prune_scavengable_nmethods();
  
    // Iteration functions.
    void oop_iterate(OopIterateClosure* cl);
    void object_iterate(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.
    HeapWord* block_start(const void* 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.
    bool block_is_obj(const HeapWord* addr) const;
  
    // Section on TLAB's.
    virtual size_t tlab_capacity(Thread* thr) const;
    virtual size_t tlab_used(Thread* thr) const;
    virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
    virtual HeapWord* allocate_new_tlab(size_t min_size,
                                        size_t requested_size,
                                        size_t* actual_size);
  
    // 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();
  
    // Ensure parsability: override
    virtual void ensure_parsability(bool retire_tlabs);
  
    // 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 the gc statistics for each generation.
    void update_gc_stats(Generation* current_generation, bool full) {
      _old_gen->update_gc_stats(current_generation, full);
    }
  
    bool no_gc_in_progress() { return !is_gc_active(); }
  
    // Override.
    void prepare_for_verify();
  
    // Override.
    void verify(VerifyOption option);
  
    // Override.
    virtual void print_on(outputStream* st) const;
    virtual void gc_threads_do(ThreadClosure* tc) const;
    virtual void print_tracing_info() const;
  
    // Used to print information about locations in the hs_err file.
    virtual bool print_location(outputStream* st, void* addr) const;
  
    void print_heap_change(const PreGenGCValues& pre_gc_values) 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
    // If "old_to_young" determines the order.
    void generation_iterate(GenClosure* cl, bool old_to_young);
  
    // Return "true" if all generations have reached the
    // maximal committed limit that they can reach, without a garbage
    // collection.
    virtual bool is_maximal_no_gc() const;
  
    // This function returns the CardTableRS object that allows us to scan
    // generations in a fully generational heap.
    CardTableRS* rem_set() { return _rem_set; }
  
    // Convenience function to be used in situations where the heap type can be
    // asserted to be this type.
    static GenCollectedHeap* heap();
  
    // The ScanningOption determines which of the roots
    // the closure is applied to:
    // "SO_None" does none;
    enum ScanningOption {
      SO_None                =  0x0,
      SO_AllCodeCache        =  0x8,
      SO_ScavengeCodeCache   = 0x10
    };
  
   protected:
    void process_roots(ScanningOption so,
                       OopClosure* strong_roots,
                       CLDClosure* strong_cld_closure,
                       CLDClosure* weak_cld_closure,
                       CodeBlobToOopClosure* code_roots);
  
    virtual void gc_prologue(bool full);
    virtual void gc_epilogue(bool full);
  
   public:
    void full_process_roots(bool is_adjust_phase,
                            ScanningOption so,
                            bool only_strong_roots,
                            OopClosure* root_closure,
                            CLDClosure* cld_closure);
  
    // Apply "root_closure" to all the weak roots of the system.
    // These include JNI weak roots, string table,
    // and referents of reachable weak refs.
    void gen_process_weak_roots(OopClosure* 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();
  
    // Returns "true" iff no allocations have occurred since the last
    // call to "save_marks".
    bool no_allocs_since_save_marks();
  
    // Returns true if an incremental collection is likely to fail.
    // We optionally consult the young gen, if asked to do so;
    // otherwise we base our answer on whether the previous incremental
    // collection attempt failed with no corrective action as of yet.
    bool incremental_collection_will_fail(bool consult_young) {
      // The first disjunct remembers if an incremental collection failed, even
      // when we thought (second disjunct) that it would not.
      return incremental_collection_failed() ||
             (consult_young && !_young_gen->collection_attempt_is_safe());
    }
  
    // If a generation bails out of an incremental collection,
    // it sets this flag.
    bool incremental_collection_failed() const {
      return _incremental_collection_failed;
    }
    void set_incremental_collection_failed() {
      _incremental_collection_failed = true;
    }
    void clear_incremental_collection_failed() {
      _incremental_collection_failed = false;
    }
  
    // Promotion of obj into gen failed.  Try to promote obj to higher
    // gens in ascending order; return the new location of obj if successful.
    // Otherwise, try expand-and-allocate for obj in both the young and old
    // generation; return the new location of obj if successful.  Otherwise, return NULL.
    oop handle_failed_promotion(Generation* old_gen,
                                oop obj,
                                size_t obj_size);
  
  
  private:
    // Return true if an allocation should be attempted in the older generation
    // if it fails in the younger generation.  Return false, otherwise.
    bool should_try_older_generation_allocation(size_t word_size) const;
  
    // Try to allocate space by expanding the heap.
    HeapWord* expand_heap_and_allocate(size_t size, bool is_tlab);
  
    HeapWord* mem_allocate_work(size_t size,
                                bool is_tlab,
                                bool* gc_overhead_limit_was_exceeded);
  
  #if INCLUDE_SERIALGC
    // 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();
  #endif
  
    // Perform a full collection of the generations up to and including max_generation.
    // 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, GenerationType max_generation);
  
    // Save the tops of the spaces in all generations
    void record_gen_tops_before_GC() PRODUCT_RETURN;
  
    // Return true if we need to perform full collection.
    bool should_do_full_collection(size_t size, bool full,
                                   bool is_tlab, GenerationType max_gen) const;
  };
  
  #endif // SHARE_GC_SHARED_GENCOLLECTEDHEAP_HPP
  