1 /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   6  * under the terms of the GNU General Public License version 2 only, as
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  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).
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  24 
  25 #ifndef SHARE_VM_GC_G1_PTRQUEUE_HPP
  26 #define SHARE_VM_GC_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 class BufferNode;
  37 class PtrQueueSet;
  38 class PtrQueue VALUE_OBJ_CLASS_SPEC {
  39   friend class VMStructs;
  40 
  41   // Noncopyable - not defined.
  42   PtrQueue(const PtrQueue&);
  43   PtrQueue& operator=(const PtrQueue&);
  44 
  45   // The ptr queue set to which this queue belongs.
  46   PtrQueueSet* const _qset;
  47 
  48   // Whether updates should be logged.
  49   bool _active;
  50 
  51   // If true, the queue is permanent, and doesn't need to deallocate
  52   // its buffer in the destructor (since that obtains a lock which may not
  53   // be legally locked by then.
  54   const bool _permanent;
  55 
  56   // The (byte) index at which an object was last enqueued.  Starts at
  57   // capacity_in_bytes (indicating an empty buffer) and goes towards zero.
  58   // Value is always pointer-size aligned.
  59   size_t _index;
  60 
  61   // Size of the current buffer, in bytes.
  62   // Value is always pointer-size aligned.
  63   size_t _capacity_in_bytes;
  64 
  65   static const size_t _element_size = sizeof(void*);
  66 
  67   // Get the capacity, in bytes.  The capacity must have been set.
  68   size_t capacity_in_bytes() const {
  69     assert(_capacity_in_bytes > 0, "capacity not set");
  70     return _capacity_in_bytes;
  71   }
  72 
  73   void set_capacity(size_t entries) {
  74     size_t byte_capacity = index_to_byte_index(entries);
  75     assert(_capacity_in_bytes == 0 || _capacity_in_bytes == byte_capacity,
  76            "changing capacity " SIZE_FORMAT " -> " SIZE_FORMAT,
  77            _capacity_in_bytes, byte_capacity);
  78     _capacity_in_bytes = byte_capacity;
  79   }
  80 
  81   static size_t byte_index_to_index(size_t ind) {
  82     assert(is_size_aligned(ind, _element_size), "precondition");
  83     return ind / _element_size;
  84   }
  85 
  86   static size_t index_to_byte_index(size_t ind) {
  87     return ind * _element_size;
  88   }
  89 
  90 protected:
  91   // The buffer.
  92   void** _buf;
  93 
  94   size_t index() const {
  95     return byte_index_to_index(_index);
  96   }
  97 
  98   void set_index(size_t new_index) {
  99     size_t byte_index = index_to_byte_index(new_index);
 100     assert(byte_index <= capacity_in_bytes(), "precondition");
 101     _index = byte_index;
 102   }
 103 
 104   size_t capacity() const {
 105     return byte_index_to_index(capacity_in_bytes());
 106   }
 107 
 108   // If there is a lock associated with this buffer, this is that lock.
 109   Mutex* _lock;
 110 
 111   PtrQueueSet* qset() { return _qset; }
 112   bool is_permanent() const { return _permanent; }
 113 
 114   // Process queue entries and release resources.
 115   void flush_impl();
 116 
 117   // Initialize this queue to contain a null buffer, and be part of the
 118   // given PtrQueueSet.
 119   PtrQueue(PtrQueueSet* qset, bool permanent = false, bool active = false);
 120 
 121   // Requires queue flushed or permanent.
 122   ~PtrQueue();
 123 
 124 public:
 125 
 126   // Associate a lock with a ptr queue.
 127   void set_lock(Mutex* lock) { _lock = lock; }
 128 
 129   // Forcibly set empty.
 130   void reset() {
 131     if (_buf != NULL) {
 132       _index = capacity_in_bytes();
 133     }
 134   }
 135 
 136   void enqueue(volatile void* ptr) {
 137     enqueue((void*)(ptr));
 138   }
 139 
 140   // Enqueues the given "obj".
 141   void enqueue(void* ptr) {
 142     if (!_active) return;
 143     else enqueue_known_active(ptr);
 144   }
 145 
 146   // This method is called when we're doing the zero index handling
 147   // and gives a chance to the queues to do any pre-enqueueing
 148   // processing they might want to do on the buffer. It should return
 149   // true if the buffer should be enqueued, or false if enough
 150   // entries were cleared from it so that it can be re-used. It should
 151   // not return false if the buffer is still full (otherwise we can
 152   // get into an infinite loop).
 153   virtual bool should_enqueue_buffer() { return true; }
 154   void handle_zero_index();
 155   void locking_enqueue_completed_buffer(BufferNode* node);
 156 
 157   void enqueue_known_active(void* ptr);
 158 
 159   // Return the size of the in-use region.
 160   size_t size() const {
 161     size_t result = 0;
 162     if (_buf != NULL) {
 163       assert(_index <= capacity_in_bytes(), "Invariant");
 164       result = byte_index_to_index(capacity_in_bytes() - _index);
 165     }
 166     return result;
 167   }
 168 
 169   bool is_empty() const {
 170     return _buf == NULL || capacity_in_bytes() == _index;
 171   }
 172 
 173   // Set the "active" property of the queue to "b".  An enqueue to an
 174   // inactive thread is a no-op.  Setting a queue to inactive resets its
 175   // log to the empty state.
 176   void set_active(bool b) {
 177     _active = b;
 178     if (!b && _buf != NULL) {
 179       reset();
 180     } else if (b && _buf != NULL) {
 181       assert(index() == capacity(),
 182              "invariant: queues are empty when activated.");
 183     }
 184   }
 185 
 186   bool is_active() const { return _active; }
 187 
 188   // To support compiler.
 189 
 190 protected:
 191   template<typename Derived>
 192   static ByteSize byte_offset_of_index() {
 193     return byte_offset_of(Derived, _index);
 194   }
 195 
 196   static ByteSize byte_width_of_index() { return in_ByteSize(sizeof(size_t)); }
 197 
 198   template<typename Derived>
 199   static ByteSize byte_offset_of_buf() {
 200     return byte_offset_of(Derived, _buf);
 201   }
 202 
 203   static ByteSize byte_width_of_buf() { return in_ByteSize(_element_size); }
 204 
 205   template<typename Derived>
 206   static ByteSize byte_offset_of_active() {
 207     return byte_offset_of(Derived, _active);
 208   }
 209 
 210   static ByteSize byte_width_of_active() { return in_ByteSize(sizeof(bool)); }
 211 
 212 };
 213 
 214 class BufferNode {
 215   size_t _index;
 216   BufferNode* _next;
 217   void* _buffer[1];             // Pseudo flexible array member.
 218 
 219   BufferNode() : _index(0), _next(NULL) { }
 220   ~BufferNode() { }
 221 
 222   static size_t buffer_offset() {
 223     return offset_of(BufferNode, _buffer);
 224   }
 225 
 226 public:
 227   BufferNode* next() const     { return _next;  }
 228   void set_next(BufferNode* n) { _next = n;     }
 229   size_t index() const         { return _index; }
 230   void set_index(size_t i)     { _index = i; }
 231 
 232   // Allocate a new BufferNode with the "buffer" having size elements.
 233   static BufferNode* allocate(size_t size);
 234 
 235   // Free a BufferNode.
 236   static void deallocate(BufferNode* node);
 237 
 238   // Return the BufferNode containing the buffer, after setting its index.
 239   static BufferNode* make_node_from_buffer(void** buffer, size_t index) {
 240     BufferNode* node =
 241       reinterpret_cast<BufferNode*>(
 242         reinterpret_cast<char*>(buffer) - buffer_offset());
 243     node->set_index(index);
 244     return node;
 245   }
 246 
 247   // Return the buffer for node.
 248   static void** make_buffer_from_node(BufferNode *node) {
 249     // &_buffer[0] might lead to index out of bounds warnings.
 250     return reinterpret_cast<void**>(
 251       reinterpret_cast<char*>(node) + buffer_offset());
 252   }
 253 };
 254 
 255 // A PtrQueueSet represents resources common to a set of pointer queues.
 256 // In particular, the individual queues allocate buffers from this shared
 257 // set, and return completed buffers to the set.
 258 // All these variables are are protected by the TLOQ_CBL_mon. XXX ???
 259 class PtrQueueSet VALUE_OBJ_CLASS_SPEC {
 260 private:
 261   // The size of all buffers in the set.
 262   size_t _buffer_size;
 263 
 264 protected:
 265   Monitor* _cbl_mon;  // Protects the fields below.
 266   BufferNode* _completed_buffers_head;
 267   BufferNode* _completed_buffers_tail;
 268   size_t _n_completed_buffers;
 269   int _process_completed_threshold;
 270   volatile bool _process_completed;
 271 
 272   // This (and the interpretation of the first element as a "next"
 273   // pointer) are protected by the TLOQ_FL_lock.
 274   Mutex* _fl_lock;
 275   BufferNode* _buf_free_list;
 276   size_t _buf_free_list_sz;
 277   // Queue set can share a freelist. The _fl_owner variable
 278   // specifies the owner. It is set to "this" by default.
 279   PtrQueueSet* _fl_owner;
 280 
 281   bool _all_active;
 282 
 283   // If true, notify_all on _cbl_mon when the threshold is reached.
 284   bool _notify_when_complete;
 285 
 286   // Maximum number of elements allowed on completed queue: after that,
 287   // enqueuer does the work itself.  Zero indicates no maximum.
 288   int _max_completed_queue;
 289   size_t _completed_queue_padding;
 290 
 291   size_t completed_buffers_list_length();
 292   void assert_completed_buffer_list_len_correct_locked();
 293   void assert_completed_buffer_list_len_correct();
 294 
 295 protected:
 296   // A mutator thread does the the work of processing a buffer.
 297   // Returns "true" iff the work is complete (and the buffer may be
 298   // deallocated).
 299   virtual bool mut_process_buffer(BufferNode* node) {
 300     ShouldNotReachHere();
 301     return false;
 302   }
 303 
 304   // Create an empty ptr queue set.
 305   PtrQueueSet(bool notify_when_complete = false);
 306   ~PtrQueueSet();
 307 
 308   // Because of init-order concerns, we can't pass these as constructor
 309   // arguments.
 310   void initialize(Monitor* cbl_mon,
 311                   Mutex* fl_lock,
 312                   int process_completed_threshold,
 313                   int max_completed_queue,
 314                   PtrQueueSet *fl_owner = NULL);
 315 
 316 public:
 317 
 318   // Return the buffer for a BufferNode of size buffer_size().
 319   void** allocate_buffer();
 320 
 321   // Return an empty buffer to the free list.  The node is required
 322   // to have been allocated with a size of buffer_size().
 323   void deallocate_buffer(BufferNode* node);
 324 
 325   // Declares that "buf" is a complete buffer.
 326   void enqueue_complete_buffer(BufferNode* node);
 327 
 328   // To be invoked by the mutator.
 329   bool process_or_enqueue_complete_buffer(BufferNode* node);
 330 
 331   bool completed_buffers_exist_dirty() {
 332     return _n_completed_buffers > 0;
 333   }
 334 
 335   bool process_completed_buffers() { return _process_completed; }
 336   void set_process_completed(bool x) { _process_completed = x; }
 337 
 338   bool is_active() { return _all_active; }
 339 
 340   // Set the buffer size.  Should be called before any "enqueue" operation
 341   // can be called.  And should only be called once.
 342   void set_buffer_size(size_t sz);
 343 
 344   // Get the buffer size.  Must have been set.
 345   size_t buffer_size() const {
 346     assert(_buffer_size > 0, "buffer size not set");
 347     return _buffer_size;
 348   }
 349 
 350   // Get/Set the number of completed buffers that triggers log processing.
 351   void set_process_completed_threshold(int sz) { _process_completed_threshold = sz; }
 352   int process_completed_threshold() const { return _process_completed_threshold; }
 353 
 354   // Must only be called at a safe point.  Indicates that the buffer free
 355   // list size may be reduced, if that is deemed desirable.
 356   void reduce_free_list();
 357 
 358   size_t completed_buffers_num() { return _n_completed_buffers; }
 359 
 360   void merge_bufferlists(PtrQueueSet* src);
 361 
 362   void set_max_completed_queue(int m) { _max_completed_queue = m; }
 363   int max_completed_queue() { return _max_completed_queue; }
 364 
 365   void set_completed_queue_padding(size_t padding) { _completed_queue_padding = padding; }
 366   size_t completed_queue_padding() { return _completed_queue_padding; }
 367 
 368   // Notify the consumer if the number of buffers crossed the threshold
 369   void notify_if_necessary();
 370 };
 371 
 372 #endif // SHARE_VM_GC_G1_PTRQUEUE_HPP
--- EOF ---