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