/*

 * Copyright (c) 2001, 2008, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 *

 */

class EdenSpace;

class ContiguousSpace;

class ScanClosure;

// DefNewGeneration is a young generation containing eden, from- and

// to-space.

class DefNewGeneration: public Generation {

  friend class VMStructs;

protected:

  Generation* _next_gen;

  int         _tenuring_threshold;   // Tenuring threshold for next collection.

  ageTable    _age_table;

  // Size of object to pretenure in words; command line provides bytes

  size_t        _pretenure_size_threshold_words;

  ageTable*   age_table() { return &_age_table; }

  // Initialize state to optimistically assume no promotion failure will

  // happen.

  void   init_assuming_no_promotion_failure();

  // True iff a promotion has failed in the current collection.

  bool   _promotion_failed;

  bool   promotion_failed() { return _promotion_failed; }

  // Handling promotion failure.  A young generation collection

  // can fail if a live object cannot be copied out of its

  // location in eden or from-space during the collection.  If

  // a collection fails, the young generation is left in a

  // consistent state such that it can be collected by a

  // full collection.

  //   Before the collection

  //     Objects are in eden or from-space

  //     All roots into the young generation point into eden or from-space.

  //

  //   After a failed collection

  //     Objects may be in eden, from-space, or to-space

  //     An object A in eden or from-space may have a copy B

  //       in to-space.  If B exists, all roots that once pointed

  //       to A must now point to B.

  //     All objects in the young generation are unmarked.

  //     Eden, from-space, and to-space will all be collected by

  //       the full collection.

  void handle_promotion_failure(oop);

  // In the absence of promotion failure, we wouldn't look at "from-space"

  // objects after a young-gen collection.  When promotion fails, however,

  // the subsequent full collection will look at from-space objects:

  // therefore we must remove their forwarding pointers.

  void remove_forwarding_pointers();

  // Preserve the mark of "obj", if necessary, in preparation for its mark

  // word being overwritten with a self-forwarding-pointer.

  void   preserve_mark_if_necessary(oop obj, markOop m);

  // Returns true if the collection can be safely attempted.

  // If this method returns false, a collection is not

  // guaranteed to fail but the system may not be able

  // to recover from the failure.

  bool collection_attempt_is_safe();

  // Promotion failure handling

  OopClosure *_promo_failure_scan_stack_closure;

  void set_promo_failure_scan_stack_closure(OopClosure *scan_stack_closure) {

    _promo_failure_scan_stack_closure = scan_stack_closure;

  }

  void drain_promo_failure_scan_stack(void);

  bool _promo_failure_drain_in_progress;

  // Performance Counters

  GenerationCounters*  _gen_counters;

  CSpaceCounters*      _eden_counters;

  CSpaceCounters*      _from_counters;

  CSpaceCounters*      _to_counters;

  // sizing information

  size_t               _max_eden_size;

  size_t               _max_survivor_size;

  // Allocation support

  bool _should_allocate_from_space;

  bool should_allocate_from_space() const {

    return _should_allocate_from_space;

  }

  void clear_should_allocate_from_space() {

    _should_allocate_from_space = false;

  }

  void set_should_allocate_from_space() {

    _should_allocate_from_space = true;

  }

 protected:

  // Spaces

  EdenSpace*       _eden_space;

  ContiguousSpace* _from_space;

  ContiguousSpace* _to_space;

  enum SomeProtectedConstants {

    // Generations are GenGrain-aligned and have size that are multiples of

    // GenGrain.

    MinFreeScratchWords = 100

  };

  // Return the size of a survivor space if this generation were of size

  // gen_size.

  size_t compute_survivor_size(size_t gen_size, size_t alignment) const {

    size_t n = gen_size / (SurvivorRatio + 2);

    return n > alignment ? align_size_down(n, alignment) : alignment;

  }

 public:  // was "protected" but caused compile error on win32

  class IsAliveClosure: public BoolObjectClosure {

    Generation* _g;

  public:

    IsAliveClosure(Generation* g);

    void do_object(oop p);

    bool do_object_b(oop p);

  };

  class KeepAliveClosure: public OopClosure {

  protected:

    ScanWeakRefClosure* _cl;

    CardTableRS* _rs;

    template <class T> void do_oop_work(T* p);

  public:

    KeepAliveClosure(ScanWeakRefClosure* cl);

    virtual void do_oop(oop* p);

    virtual void do_oop(narrowOop* p);

  };

  class FastKeepAliveClosure: public KeepAliveClosure {

  protected:

    HeapWord* _boundary;

    template <class T> void do_oop_work(T* p);

  public:

    FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl);

    virtual void do_oop(oop* p);

    virtual void do_oop(narrowOop* p);

  };

  class EvacuateFollowersClosure: public VoidClosure {

    GenCollectedHeap* _gch;

    int _level;

    ScanClosure* _scan_cur_or_nonheap;

    ScanClosure* _scan_older;

  public:

    EvacuateFollowersClosure(GenCollectedHeap* gch, int level,

                             ScanClosure* cur, ScanClosure* older);

    void do_void();

  };

  class FastEvacuateFollowersClosure: public VoidClosure {

    GenCollectedHeap* _gch;

    int _level;

    DefNewGeneration* _gen;

    FastScanClosure* _scan_cur_or_nonheap;

    FastScanClosure* _scan_older;

  public:

    FastEvacuateFollowersClosure(GenCollectedHeap* gch, int level,

                                 DefNewGeneration* gen,

                                 FastScanClosure* cur,

                                 FastScanClosure* older);

    void do_void();

  };

 public:

  DefNewGeneration(ReservedSpace rs, size_t initial_byte_size, int level,

                   const char* policy="Copy");

  virtual Generation::Name kind() { return Generation::DefNew; }

  // Accessing spaces

  EdenSpace*       eden() const           { return _eden_space; }

  ContiguousSpace* from() const           { return _from_space;  }

  ContiguousSpace* to()   const           { return _to_space;    }

  virtual CompactibleSpace* first_compaction_space() const;

  // Space enquiries

  size_t capacity() const;

  size_t used() const;

  size_t free() const;

  size_t max_capacity() const;

  size_t capacity_before_gc() const;

  size_t unsafe_max_alloc_nogc() const;

  size_t contiguous_available() const;

  size_t max_eden_size() const              { return _max_eden_size; }

  size_t max_survivor_size() const          { return _max_survivor_size; }

  bool supports_inline_contig_alloc() const { return true; }

  HeapWord** top_addr() const;

  HeapWord** end_addr() const;

  // Thread-local allocation buffers

  bool supports_tlab_allocation() const { return true; }

  size_t tlab_capacity() const;

  size_t unsafe_max_tlab_alloc() const;

  // Grow the generation by the specified number of bytes.

  // The size of bytes is assumed to be properly aligned.

  // Return true if the expansion was successful.

  bool expand(size_t bytes);

  // DefNewGeneration cannot currently expand except at

  // a GC.

  virtual bool is_maximal_no_gc() const { return true; }

  // Iteration

  void object_iterate(ObjectClosure* blk);

  void object_iterate_since_last_GC(ObjectClosure* cl);

  void younger_refs_iterate(OopsInGenClosure* cl);

  void space_iterate(SpaceClosure* blk, bool usedOnly = false);

  // Allocation support

  virtual bool should_allocate(size_t word_size, bool is_tlab) {

    assert(UseTLAB || !is_tlab, "Should not allocate tlab");

    size_t overflow_limit    = (size_t)1 << (BitsPerSize_t - LogHeapWordSize);

    const bool non_zero      = word_size > 0;

    const bool overflows     = word_size >= overflow_limit;

    const bool check_too_big = _pretenure_size_threshold_words > 0;

    const bool not_too_big   = word_size < _pretenure_size_threshold_words;

    const bool size_ok       = is_tlab || !check_too_big || not_too_big;

    bool result = !overflows &&

                  non_zero   &&

                  size_ok;

    return result;

  }

  HeapWord* allocate(size_t word_size, bool is_tlab);

  HeapWord* allocate_from_space(size_t word_size);

  HeapWord* par_allocate(size_t word_size, bool is_tlab);

  // Prologue & Epilogue

  virtual void gc_prologue(bool full);

  virtual void gc_epilogue(bool full);

  // Save the tops for eden, from, and to

  virtual void record_spaces_top();

  // Doesn't require additional work during GC prologue and epilogue

  virtual bool performs_in_place_marking() const { return false; }

  // Accessing marks

  void save_marks();

  void reset_saved_marks();

  bool no_allocs_since_save_marks();

  // Need to declare the full complement of closures, whether we'll

  // override them or not, or get message from the compiler:

  //   oop_since_save_marks_iterate_nv hides virtual function...

#define DefNew_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \

  void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl);

  ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DECL)

#undef DefNew_SINCE_SAVE_MARKS_DECL

  // For non-youngest collection, the DefNewGeneration can contribute

  // "to-space".

  virtual void contribute_scratch(ScratchBlock*& list, Generation* requestor,

                          size_t max_alloc_words);

  // Reset for contribution of "to-space".

  virtual void reset_scratch();

  // GC support

  virtual void compute_new_size();

  virtual void collect(bool   full,

                       bool   clear_all_soft_refs,

                       size_t size,

                       bool   is_tlab);

  HeapWord* expand_and_allocate(size_t size,

                                bool is_tlab,

                                bool parallel = false);

  oop copy_to_survivor_space(oop old);

  int tenuring_threshold() { return _tenuring_threshold; }

  // Performance Counter support

  void update_counters();

  // Printing

  virtual const char* name() const;

  virtual const char* short_name() const { return "DefNew"; }

  bool must_be_youngest() const { return true; }

  bool must_be_oldest() const { return false; }

  // PrintHeapAtGC support.

  void print_on(outputStream* st) const;

  void verify(bool allow_dirty);

 protected:

  // If clear_space is true, clear the survivor spaces.  Eden is

  // cleared if the minimum size of eden is 0.  If mangle_space

  // is true, also mangle the space in debug mode.

  void compute_space_boundaries(uintx minimum_eden_size,

                                bool clear_space,

                                bool mangle_space);

  // Scavenge support

  void swap_spaces();

};