1 /*
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   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
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  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
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  24 
  25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_PTRQUEUE_HPP
  26 #define SHARE_VM_GC_IMPLEMENTATION_G1_PTRQUEUE_HPP
  27 
  28 #include "memory/allocation.hpp"
  29 #include "utilities/sizes.hpp"
  30 
  31 // There are various techniques that require threads to be able to log
  32 // addresses.  For example, a generational write barrier might log
  33 // the addresses of modified old-generation objects.  This type supports
  34 // this operation.
  35 
  36 // The definition of placement operator new(size_t, void*) in the <new>.
  37 #include <new>
  38 
  39 class PtrQueueSet;
  40 class PtrQueue VALUE_OBJ_CLASS_SPEC {
  41   friend class VMStructs;
  42 
  43 protected:
  44   // The ptr queue set to which this queue belongs.
  45   PtrQueueSet* _qset;
  46 
  47   // Whether updates should be logged.
  48   bool _active;
  49 
  50   // The buffer.
  51   void** _buf;
  52   // The index at which an object was last enqueued.  Starts at "_sz"
  53   // (indicating an empty buffer) and goes towards zero.
  54   size_t _index;
  55 
  56   // The size of the buffer.
  57   size_t _sz;
  58 
  59   // If true, the queue is permanent, and doesn't need to deallocate
  60   // its buffer in the destructor (since that obtains a lock which may not
  61   // be legally locked by then.
  62   bool _perm;
  63 
  64   // If there is a lock associated with this buffer, this is that lock.
  65   Mutex* _lock;
  66 
  67   PtrQueueSet* qset() { return _qset; }
  68 
  69 public:
  70   // Initialize this queue to contain a null buffer, and be part of the
  71   // given PtrQueueSet.
  72   PtrQueue(PtrQueueSet* qset, bool perm = false, bool active = false);
  73   // Release any contained resources.
  74   virtual void flush();
  75   // Calls flush() when destroyed.
  76   ~PtrQueue() { flush(); }
  77 
  78   // Associate a lock with a ptr queue.
  79   void set_lock(Mutex* lock) { _lock = lock; }
  80 
  81   void reset() { if (_buf != NULL) _index = _sz; }
  82 
  83   void enqueue(volatile void* ptr) {
  84     enqueue((void*)(ptr));
  85   }
  86 
  87   // Enqueues the given "obj".
  88   void enqueue(void* ptr) {
  89     if (!_active) return;
  90     else enqueue_known_active(ptr);
  91   }
  92 
  93   // This method is called when we're doing the zero index handling
  94   // and gives a chance to the queues to do any pre-enqueueing
  95   // processing they might want to do on the buffer. It should return
  96   // true if the buffer should be enqueued, or false if enough
  97   // entries were cleared from it so that it can be re-used. It should
  98   // not return false if the buffer is still full (otherwise we can
  99   // get into an infinite loop).
 100   virtual bool should_enqueue_buffer() { return true; }
 101   void handle_zero_index();
 102   void locking_enqueue_completed_buffer(void** buf);
 103 
 104   void enqueue_known_active(void* ptr);
 105 
 106   size_t size() {
 107     assert(_sz >= _index, "Invariant.");
 108     return _buf == NULL ? 0 : _sz - _index;
 109   }
 110 
 111   bool is_empty() {
 112     return _buf == NULL || _sz == _index;
 113   }
 114 
 115   // Set the "active" property of the queue to "b".  An enqueue to an
 116   // inactive thread is a no-op.  Setting a queue to inactive resets its
 117   // log to the empty state.
 118   void set_active(bool b) {
 119     _active = b;
 120     if (!b && _buf != NULL) {
 121       _index = _sz;
 122     } else if (b && _buf != NULL) {
 123       assert(_index == _sz, "invariant: queues are empty when activated.");
 124     }
 125   }
 126 
 127   bool is_active() { return _active; }
 128 
 129   static int byte_index_to_index(int ind) {
 130     assert((ind % oopSize) == 0, "Invariant.");
 131     return ind / oopSize;
 132   }
 133 
 134   static int index_to_byte_index(int byte_ind) {
 135     return byte_ind * oopSize;
 136   }
 137 
 138   // To support compiler.
 139   static ByteSize byte_offset_of_index() {
 140     return byte_offset_of(PtrQueue, _index);
 141   }
 142   static ByteSize byte_width_of_index() { return in_ByteSize(sizeof(size_t)); }
 143 
 144   static ByteSize byte_offset_of_buf() {
 145     return byte_offset_of(PtrQueue, _buf);
 146   }
 147   static ByteSize byte_width_of_buf() { return in_ByteSize(sizeof(void*)); }
 148 
 149   static ByteSize byte_offset_of_active() {
 150     return byte_offset_of(PtrQueue, _active);
 151   }
 152   static ByteSize byte_width_of_active() { return in_ByteSize(sizeof(bool)); }
 153 
 154 };
 155 
 156 class BufferNode {
 157   size_t _index;
 158   BufferNode* _next;
 159 public:
 160   BufferNode() : _index(0), _next(NULL) { }
 161   BufferNode* next() const     { return _next;  }
 162   void set_next(BufferNode* n) { _next = n;     }
 163   size_t index() const         { return _index; }
 164   void set_index(size_t i)     { _index = i;    }
 165 
 166   // Align the size of the structure to the size of the pointer
 167   static size_t aligned_size() {
 168     static const size_t alignment = round_to(sizeof(BufferNode), sizeof(void*));
 169     return alignment;
 170   }
 171 
 172   // BufferNode is allocated before the buffer.
 173   // The chunk of memory that holds both of them is a block.
 174 
 175   // Produce a new BufferNode given a buffer.
 176   static BufferNode* new_from_buffer(void** buf) {
 177     return new (make_block_from_buffer(buf)) BufferNode;
 178   }
 179 
 180   // The following are the required conversion routines:
 181   static BufferNode* make_node_from_buffer(void** buf) {
 182     return (BufferNode*)make_block_from_buffer(buf);
 183   }
 184   static void** make_buffer_from_node(BufferNode *node) {
 185     return make_buffer_from_block(node);
 186   }
 187   static void* make_block_from_node(BufferNode *node) {
 188     return (void*)node;
 189   }
 190   static void** make_buffer_from_block(void* p) {
 191     return (void**)((char*)p + aligned_size());
 192   }
 193   static void* make_block_from_buffer(void** p) {
 194     return (void*)((char*)p - aligned_size());
 195   }
 196 };
 197 
 198 // A PtrQueueSet represents resources common to a set of pointer queues.
 199 // In particular, the individual queues allocate buffers from this shared
 200 // set, and return completed buffers to the set.
 201 // All these variables are are protected by the TLOQ_CBL_mon. XXX ???
 202 class PtrQueueSet VALUE_OBJ_CLASS_SPEC {
 203 protected:
 204   Monitor* _cbl_mon;  // Protects the fields below.
 205   BufferNode* _completed_buffers_head;
 206   BufferNode* _completed_buffers_tail;
 207   int _n_completed_buffers;
 208   int _process_completed_threshold;
 209   volatile bool _process_completed;
 210 
 211   // This (and the interpretation of the first element as a "next"
 212   // pointer) are protected by the TLOQ_FL_lock.
 213   Mutex* _fl_lock;
 214   BufferNode* _buf_free_list;
 215   size_t _buf_free_list_sz;
 216   // Queue set can share a freelist. The _fl_owner variable
 217   // specifies the owner. It is set to "this" by default.
 218   PtrQueueSet* _fl_owner;
 219 
 220   // The size of all buffers in the set.
 221   size_t _sz;
 222 
 223   bool _all_active;
 224 
 225   // If true, notify_all on _cbl_mon when the threshold is reached.
 226   bool _notify_when_complete;
 227 
 228   // Maximum number of elements allowed on completed queue: after that,
 229   // enqueuer does the work itself.  Zero indicates no maximum.
 230   int _max_completed_queue;
 231   int _completed_queue_padding;
 232 
 233   int completed_buffers_list_length();
 234   void assert_completed_buffer_list_len_correct_locked();
 235   void assert_completed_buffer_list_len_correct();
 236 
 237 protected:
 238   // A mutator thread does the the work of processing a buffer.
 239   // Returns "true" iff the work is complete (and the buffer may be
 240   // deallocated).
 241   virtual bool mut_process_buffer(void** buf) {
 242     ShouldNotReachHere();
 243     return false;
 244   }
 245 
 246 public:
 247   // Create an empty ptr queue set.
 248   PtrQueueSet(bool notify_when_complete = false);
 249 
 250   // Because of init-order concerns, we can't pass these as constructor
 251   // arguments.
 252   void initialize(Monitor* cbl_mon, Mutex* fl_lock,
 253                   int process_completed_threshold,
 254                   int max_completed_queue,
 255                   PtrQueueSet *fl_owner = NULL) {
 256     _max_completed_queue = max_completed_queue;
 257     _process_completed_threshold = process_completed_threshold;
 258     _completed_queue_padding = 0;
 259     assert(cbl_mon != NULL && fl_lock != NULL, "Init order issue?");
 260     _cbl_mon = cbl_mon;
 261     _fl_lock = fl_lock;
 262     _fl_owner = (fl_owner != NULL) ? fl_owner : this;
 263   }
 264 
 265   // Return an empty oop array of size _sz (required to be non-zero).
 266   void** allocate_buffer();
 267 
 268   // Return an empty buffer to the free list.  The "buf" argument is
 269   // required to be a pointer to the head of an array of length "_sz".
 270   void deallocate_buffer(void** buf);
 271 
 272   // Declares that "buf" is a complete buffer.
 273   void enqueue_complete_buffer(void** buf, size_t index = 0);
 274 
 275   // To be invoked by the mutator.
 276   bool process_or_enqueue_complete_buffer(void** buf);
 277 
 278   bool completed_buffers_exist_dirty() {
 279     return _n_completed_buffers > 0;
 280   }
 281 
 282   bool process_completed_buffers() { return _process_completed; }
 283   void set_process_completed(bool x) { _process_completed = x; }
 284 
 285   bool is_active() { return _all_active; }
 286 
 287   // Set the buffer size.  Should be called before any "enqueue" operation
 288   // can be called.  And should only be called once.
 289   void set_buffer_size(size_t sz);
 290 
 291   // Get the buffer size.
 292   size_t buffer_size() { return _sz; }
 293 
 294   // Get/Set the number of completed buffers that triggers log processing.
 295   void set_process_completed_threshold(int sz) { _process_completed_threshold = sz; }
 296   int process_completed_threshold() const { return _process_completed_threshold; }
 297 
 298   // Must only be called at a safe point.  Indicates that the buffer free
 299   // list size may be reduced, if that is deemed desirable.
 300   void reduce_free_list();
 301 
 302   int completed_buffers_num() { return _n_completed_buffers; }
 303 
 304   void merge_bufferlists(PtrQueueSet* src);
 305 
 306   void set_max_completed_queue(int m) { _max_completed_queue = m; }
 307   int max_completed_queue() { return _max_completed_queue; }
 308 
 309   void set_completed_queue_padding(int padding) { _completed_queue_padding = padding; }
 310   int completed_queue_padding() { return _completed_queue_padding; }
 311 
 312   // Notify the consumer if the number of buffers crossed the threshold
 313   void notify_if_necessary();
 314 };
 315 
 316 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_PTRQUEUE_HPP