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.
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   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   bool is_permanent() const { return _perm; }
  69 
  70   // Process queue entries and release resources, if not permanent.
  71   void flush_impl();
  72 
  73 public:
  74   // Initialize this queue to contain a null buffer, and be part of the
  75   // given PtrQueueSet.
  76   PtrQueue(PtrQueueSet* qset, bool perm = false, bool active = false);
  77 
  78   // Requires queue flushed or permanent.
  79   ~PtrQueue();
  80 
  81   // Associate a lock with a ptr queue.
  82   void set_lock(Mutex* lock) { _lock = lock; }
  83 
  84   void reset() { if (_buf != NULL) _index = _sz; }
  85 
  86   void enqueue(volatile void* ptr) {
  87     enqueue((void*)(ptr));
  88   }
  89 
  90   // Enqueues the given "obj".
  91   void enqueue(void* ptr) {
  92     if (!_active) return;
  93     else enqueue_known_active(ptr);
  94   }
  95 
  96   // This method is called when we're doing the zero index handling
  97   // and gives a chance to the queues to do any pre-enqueueing
  98   // processing they might want to do on the buffer. It should return
  99   // true if the buffer should be enqueued, or false if enough
 100   // entries were cleared from it so that it can be re-used. It should
 101   // not return false if the buffer is still full (otherwise we can
 102   // get into an infinite loop).
 103   virtual bool should_enqueue_buffer() { return true; }
 104   void handle_zero_index();
 105   void locking_enqueue_completed_buffer(void** buf);
 106 
 107   void enqueue_known_active(void* ptr);
 108 
 109   size_t size() {
 110     assert(_sz >= _index, "Invariant.");
 111     return _buf == NULL ? 0 : _sz - _index;
 112   }
 113 
 114   bool is_empty() {
 115     return _buf == NULL || _sz == _index;
 116   }
 117 
 118   // Set the "active" property of the queue to "b".  An enqueue to an
 119   // inactive thread is a no-op.  Setting a queue to inactive resets its
 120   // log to the empty state.
 121   void set_active(bool b) {
 122     _active = b;
 123     if (!b && _buf != NULL) {
 124       _index = _sz;
 125     } else if (b && _buf != NULL) {
 126       assert(_index == _sz, "invariant: queues are empty when activated.");
 127     }
 128   }
 129 
 130   bool is_active() { return _active; }
 131 
 132   static int byte_index_to_index(int ind) {
 133     assert((ind % oopSize) == 0, "Invariant.");
 134     return ind / oopSize;
 135   }
 136 
 137   static int index_to_byte_index(int byte_ind) {
 138     return byte_ind * oopSize;
 139   }
 140 
 141   // To support compiler.
 142   static ByteSize byte_offset_of_index() {
 143     return byte_offset_of(PtrQueue, _index);
 144   }
 145   static ByteSize byte_width_of_index() { return in_ByteSize(sizeof(size_t)); }
 146 
 147   static ByteSize byte_offset_of_buf() {
 148     return byte_offset_of(PtrQueue, _buf);
 149   }
 150   static ByteSize byte_width_of_buf() { return in_ByteSize(sizeof(void*)); }
 151 
 152   static ByteSize byte_offset_of_active() {
 153     return byte_offset_of(PtrQueue, _active);
 154   }
 155   static ByteSize byte_width_of_active() { return in_ByteSize(sizeof(bool)); }
 156 
 157 };
 158 
 159 class BufferNode {
 160   size_t _index;
 161   BufferNode* _next;
 162 public:
 163   BufferNode() : _index(0), _next(NULL) { }
 164   BufferNode* next() const     { return _next;  }
 165   void set_next(BufferNode* n) { _next = n;     }
 166   size_t index() const         { return _index; }
 167   void set_index(size_t i)     { _index = i;    }
 168 
 169   // Align the size of the structure to the size of the pointer
 170   static size_t aligned_size() {
 171     static const size_t alignment = round_to(sizeof(BufferNode), sizeof(void*));
 172     return alignment;
 173   }
 174 
 175   // BufferNode is allocated before the buffer.
 176   // The chunk of memory that holds both of them is a block.
 177 
 178   // Produce a new BufferNode given a buffer.
 179   static BufferNode* new_from_buffer(void** buf) {
 180     return new (make_block_from_buffer(buf)) BufferNode;
 181   }
 182 
 183   // The following are the required conversion routines:
 184   static BufferNode* make_node_from_buffer(void** buf) {
 185     return (BufferNode*)make_block_from_buffer(buf);
 186   }
 187   static void** make_buffer_from_node(BufferNode *node) {
 188     return make_buffer_from_block(node);
 189   }
 190   static void* make_block_from_node(BufferNode *node) {
 191     return (void*)node;
 192   }
 193   static void** make_buffer_from_block(void* p) {
 194     return (void**)((char*)p + aligned_size());
 195   }
 196   static void* make_block_from_buffer(void** p) {
 197     return (void*)((char*)p - aligned_size());
 198   }
 199 };
 200 
 201 // A PtrQueueSet represents resources common to a set of pointer queues.
 202 // In particular, the individual queues allocate buffers from this shared
 203 // set, and return completed buffers to the set.
 204 // All these variables are are protected by the TLOQ_CBL_mon. XXX ???
 205 class PtrQueueSet VALUE_OBJ_CLASS_SPEC {
 206 protected:
 207   Monitor* _cbl_mon;  // Protects the fields below.
 208   BufferNode* _completed_buffers_head;
 209   BufferNode* _completed_buffers_tail;
 210   int _n_completed_buffers;
 211   int _process_completed_threshold;
 212   volatile bool _process_completed;
 213 
 214   // This (and the interpretation of the first element as a "next"
 215   // pointer) are protected by the TLOQ_FL_lock.
 216   Mutex* _fl_lock;
 217   BufferNode* _buf_free_list;
 218   size_t _buf_free_list_sz;
 219   // Queue set can share a freelist. The _fl_owner variable
 220   // specifies the owner. It is set to "this" by default.
 221   PtrQueueSet* _fl_owner;
 222 
 223   // The size of all buffers in the set.
 224   size_t _sz;
 225 
 226   bool _all_active;
 227 
 228   // If true, notify_all on _cbl_mon when the threshold is reached.
 229   bool _notify_when_complete;
 230 
 231   // Maximum number of elements allowed on completed queue: after that,
 232   // enqueuer does the work itself.  Zero indicates no maximum.
 233   int _max_completed_queue;
 234   int _completed_queue_padding;
 235 
 236   int completed_buffers_list_length();
 237   void assert_completed_buffer_list_len_correct_locked();
 238   void assert_completed_buffer_list_len_correct();
 239 
 240 protected:
 241   // A mutator thread does the the work of processing a buffer.
 242   // Returns "true" iff the work is complete (and the buffer may be
 243   // deallocated).
 244   virtual bool mut_process_buffer(void** buf) {
 245     ShouldNotReachHere();
 246   }
 247 
 248 public:
 249   // Create an empty ptr queue set.
 250   PtrQueueSet(bool notify_when_complete = false);
 251 
 252   // Because of init-order concerns, we can't pass these as constructor
 253   // arguments.
 254   void initialize(Monitor* cbl_mon, Mutex* fl_lock,
 255                   int process_completed_threshold,
 256                   int max_completed_queue,
 257                   PtrQueueSet *fl_owner = NULL) {
 258     _max_completed_queue = max_completed_queue;
 259     _process_completed_threshold = process_completed_threshold;
 260     _completed_queue_padding = 0;
 261     assert(cbl_mon != NULL && fl_lock != NULL, "Init order issue?");
 262     _cbl_mon = cbl_mon;
 263     _fl_lock = fl_lock;
 264     _fl_owner = (fl_owner != NULL) ? fl_owner : this;
 265   }
 266 
 267   // Return an empty oop array of size _sz (required to be non-zero).
 268   void** allocate_buffer();
 269 
 270   // Return an empty buffer to the free list.  The "buf" argument is
 271   // required to be a pointer to the head of an array of length "_sz".
 272   void deallocate_buffer(void** buf);
 273 
 274   // Declares that "buf" is a complete buffer.
 275   void enqueue_complete_buffer(void** buf, size_t index = 0);
 276 
 277   // To be invoked by the mutator.
 278   bool process_or_enqueue_complete_buffer(void** buf);
 279 
 280   bool completed_buffers_exist_dirty() {
 281     return _n_completed_buffers > 0;
 282   }
 283 
 284   bool process_completed_buffers() { return _process_completed; }
 285   void set_process_completed(bool x) { _process_completed = x; }
 286 
 287   bool is_active() { return _all_active; }
 288 
 289   // Set the buffer size.  Should be called before any "enqueue" operation
 290   // can be called.  And should only be called once.
 291   void set_buffer_size(size_t sz);
 292 
 293   // Get the buffer size.
 294   size_t buffer_size() { return _sz; }
 295 
 296   // Get/Set the number of completed buffers that triggers log processing.
 297   void set_process_completed_threshold(int sz) { _process_completed_threshold = sz; }
 298   int process_completed_threshold() const { return _process_completed_threshold; }
 299 
 300   // Must only be called at a safe point.  Indicates that the buffer free
 301   // list size may be reduced, if that is deemed desirable.
 302   void reduce_free_list();
 303 
 304   int completed_buffers_num() { return _n_completed_buffers; }
 305 
 306   void merge_bufferlists(PtrQueueSet* src);
 307 
 308   void set_max_completed_queue(int m) { _max_completed_queue = m; }
 309   int max_completed_queue() { return _max_completed_queue; }
 310 
 311   void set_completed_queue_padding(int padding) { _completed_queue_padding = padding; }
 312   int completed_queue_padding() { return _completed_queue_padding; }
 313 
 314   // Notify the consumer if the number of buffers crossed the threshold
 315   void notify_if_necessary();
 316 };
 317 
 318 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_PTRQUEUE_HPP