1 /*

     2  * Copyright (c) 2010, 2015, Oracle and/or its affiliates. All rights reserved.

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

     4  *

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

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

     7  * published by the Free Software Foundation.

     8  *

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

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

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

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

    13  * accompanied this code).

    14  *

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

    16  * 2 along with this work; if not, write to the Free Software Foundation,

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

    18  *

    19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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

    21  * questions.

    22  *

    23  */

    24 

    25 #ifndef SHARE_VM_GC_CMS_PROMOTIONINFO_HPP

    26 #define SHARE_VM_GC_CMS_PROMOTIONINFO_HPP

    27 

    28 #include "gc/cms/freeChunk.hpp"

    29 #include "memory/allocation.hpp"

    30 

    31 // Forward declarations

    32 class CompactibleFreeListSpace;

    33 

    34 class PromotedObject VALUE_OBJ_CLASS_SPEC {

    35  private:

    36   enum {

    37     promoted_mask  = right_n_bits(2),   // i.e. 0x3

    38     displaced_mark = nth_bit(2),        // i.e. 0x4

    39     next_mask      = ~(right_n_bits(3)) // i.e. ~(0x7)

    40   };

    41 

    42   // Below, we want _narrow_next in the "higher" 32 bit slot,

    43   // whose position will depend on endian-ness of the platform.

    44   // This is so that there is no interference with the

    45   // cms_free_bit occupying bit position 7 (lsb == 0)

    46   // when we are using compressed oops; see FreeChunk::is_free().

    47   // We cannot move the cms_free_bit down because currently

    48   // biased locking code assumes that age bits are contiguous

    49   // with the lock bits. Even if that assumption were relaxed,

    50   // the least position we could move this bit to would be

    51   // to bit position 3, which would require 16 byte alignment.

    52   typedef struct {

    53 #ifdef VM_LITTLE_ENDIAN

    54     LP64_ONLY(narrowOop _pad;)

    55               narrowOop _narrow_next;

    56 #else

    57               narrowOop _narrow_next;

    58     LP64_ONLY(narrowOop _pad;)

    59 #endif

    60   } Data;

    61 

    62   union {

    63     intptr_t _next;

    64     Data     _data;

    65   };

    66  public:

    67   inline PromotedObject* next() const {

    68     assert(!((FreeChunk*)this)->is_free(), "Error");

    69     PromotedObject* res;

    70     if (UseCompressedOops) {

    71       // The next pointer is a compressed oop stored in the top 32 bits

    72       res = (PromotedObject*)oopDesc::decode_heap_oop(_data._narrow_next);

    73     } else {

    74       res = (PromotedObject*)(_next & next_mask);

    75     }

    76     assert(oop(res)->is_oop_or_null(true /* ignore mark word */), err_msg("Expected an oop or NULL at " PTR_FORMAT, p2i(oop(res))));

    77     return res;

    78   }

    79   inline void setNext(PromotedObject* x) {

    80     assert(((intptr_t)x & ~next_mask) == 0, "Conflict in bit usage, "

    81            "or insufficient alignment of objects");

    82     if (UseCompressedOops) {

    83       assert(_data._narrow_next == 0, "Overwrite?");

    84       _data._narrow_next = oopDesc::encode_heap_oop(oop(x));

    85     } else {

    86       _next |= (intptr_t)x;

    87     }

    88     assert(!((FreeChunk*)this)->is_free(), "Error");

    89   }

    90   inline void setPromotedMark() {

    91     _next |= promoted_mask;

    92     assert(!((FreeChunk*)this)->is_free(), "Error");

    93   }

    94   inline bool hasPromotedMark() const {

    95     assert(!((FreeChunk*)this)->is_free(), "Error");

    96     return (_next & promoted_mask) == promoted_mask;

    97   }

    98   inline void setDisplacedMark() {

    99     _next |= displaced_mark;

   100     assert(!((FreeChunk*)this)->is_free(), "Error");

   101   }

   102   inline bool hasDisplacedMark() const {

   103     assert(!((FreeChunk*)this)->is_free(), "Error");

   104     return (_next & displaced_mark) != 0;

   105   }

   106   inline void clear_next()        {

   107     _next = 0;

   108     assert(!((FreeChunk*)this)->is_free(), "Error");

   109   }

   110   debug_only(void *next_addr() { return (void *) &_next; })

   111 };

   112 

   113 class SpoolBlock: public FreeChunk {

   114   friend class PromotionInfo;

   115  protected:

   116   SpoolBlock*  nextSpoolBlock;

   117   size_t       bufferSize;        // number of usable words in this block

   118   markOop*     displacedHdr;      // the displaced headers start here

   119 

   120   // Note about bufferSize: it denotes the number of entries available plus 1;

   121   // legal indices range from 1 through BufferSize - 1.  See the verification

   122   // code verify() that counts the number of displaced headers spooled.

   123   size_t computeBufferSize() {

   124     return (size() * sizeof(HeapWord) - sizeof(*this)) / sizeof(markOop);

   125   }

   126 

   127  public:

   128   void init() {

   129     bufferSize = computeBufferSize();

   130     displacedHdr = (markOop*)&displacedHdr;

   131     nextSpoolBlock = NULL;

   132   }

   133 

   134   void print_on(outputStream* st) const;

   135   void print() const { print_on(gclog_or_tty); }

   136 };

   137 

   138 class PromotionInfo VALUE_OBJ_CLASS_SPEC {

   139   bool            _tracking;      // set if tracking

   140   CompactibleFreeListSpace* _space; // the space to which this belongs

   141   PromotedObject* _promoHead;     // head of list of promoted objects

   142   PromotedObject* _promoTail;     // tail of list of promoted objects

   143   SpoolBlock*     _spoolHead;     // first spooling block

   144   SpoolBlock*     _spoolTail;     // last  non-full spooling block or null

   145   SpoolBlock*     _splice_point;  // when _spoolTail is null, holds list tail

   146   SpoolBlock*     _spareSpool;    // free spool buffer

   147   size_t          _firstIndex;    // first active index in

   148                                   // first spooling block (_spoolHead)

   149   size_t          _nextIndex;     // last active index + 1 in last

   150                                   // spooling block (_spoolTail)

   151  private:

   152   // ensure that spooling space exists; return true if there is spooling space

   153   bool ensure_spooling_space_work();

   154 

   155  public:

   156   PromotionInfo() :

   157     _tracking(0), _space(NULL),

   158     _promoHead(NULL), _promoTail(NULL),

   159     _spoolHead(NULL), _spoolTail(NULL),

   160     _spareSpool(NULL), _firstIndex(1),

   161     _nextIndex(1) {}

   162 

   163   bool noPromotions() const {

   164     assert(_promoHead != NULL || _promoTail == NULL, "list inconsistency");

   165     return _promoHead == NULL;

   166   }

   167   void startTrackingPromotions();

   168   void stopTrackingPromotions(uint worker_id = 0);

   169   bool tracking() const          { return _tracking;  }

   170   void track(PromotedObject* trackOop);      // keep track of a promoted oop

   171   // The following variant must be used when trackOop is not fully

   172   // initialized and has a NULL klass:

   173   void track(PromotedObject* trackOop, Klass* klassOfOop); // keep track of a promoted oop

   174   void setSpace(CompactibleFreeListSpace* sp) { _space = sp; }

   175   CompactibleFreeListSpace* space() const     { return _space; }

   176   markOop nextDisplacedHeader(); // get next header & forward spool pointer

   177   void    saveDisplacedHeader(markOop hdr);

   178                                  // save header and forward spool

   179 

   180   inline size_t refillSize() const;

   181 

   182   SpoolBlock* getSpoolBlock();   // return a free spooling block

   183   inline bool has_spooling_space() {

   184     return _spoolTail != NULL && _spoolTail->bufferSize > _nextIndex;

   185   }

   186   // ensure that spooling space exists

   187   bool ensure_spooling_space() {

   188     return has_spooling_space() || ensure_spooling_space_work();

   189   }

   190   #define PROMOTED_OOPS_ITERATE_DECL(OopClosureType, nv_suffix)  \

   191     void promoted_oops_iterate##nv_suffix(OopClosureType* cl);

   192   ALL_SINCE_SAVE_MARKS_CLOSURES(PROMOTED_OOPS_ITERATE_DECL)

   193   #undef PROMOTED_OOPS_ITERATE_DECL

   194   void promoted_oops_iterate(OopsInGenClosure* cl) {

   195     promoted_oops_iterate_v(cl);

   196   }

   197   void verify()  const;

   198   void reset() {

   199     _promoHead = NULL;

   200     _promoTail = NULL;

   201     _spoolHead = NULL;

   202     _spoolTail = NULL;

   203     _spareSpool = NULL;

   204     _firstIndex = 0;

   205     _nextIndex = 0;

   206 

   207   }

   208 

   209   void print_on(outputStream* st) const;

   210   void print_statistics(uint worker_id) const;

   211 };

   212 

   213 

   214 #endif // SHARE_VM_GC_CMS_PROMOTIONINFO_HPP