Mercurial > jdk8-mips64-public > hotspot / file revision

 /*

  * 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);

   // Together, these keep <object with a preserved mark, mark value> pairs.

   // They should always contain the same number of elements.

   Stack<oop>     _objs_with_preserved_marks;

   Stack<markOop> _preserved_marks_of_objs;

   // 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;

   }

   Stack<oop> _promo_failure_scan_stack;

   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();

   // Returns true if the collection is likely to be safely

   // completed. Even if this method returns true, a collection

   // may not be guaranteed to succeed, and the system should be

   // able to safely unwind and recover from that failure, albeit

   // at some additional cost. Override superclass's implementation.

   virtual bool collection_attempt_is_safe();

   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);

   bool promo_failure_scan_is_complete() const {

     return _promo_failure_scan_stack.is_empty();

   }

  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();

 };