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
--- EOF ---