1 /*
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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_SHARED_WORKGROUP_HPP
  26 #define SHARE_VM_GC_SHARED_WORKGROUP_HPP
  27 
  28 #include "memory/allocation.hpp"
  29 #include "runtime/globals.hpp"
  30 #include "runtime/thread.hpp"
  31 #include "gc/shared/gcId.hpp"
  32 #include "utilities/debug.hpp"
  33 #include "utilities/globalDefinitions.hpp"
  34 
  35 // Task class hierarchy:
  36 //   AbstractGangTask
  37 //
  38 // Gang/Group class hierarchy:
  39 //   AbstractWorkGang
  40 //     WorkGang
  41 //     YieldingFlexibleWorkGang (defined in another file)
  42 //
  43 // Worker class hierarchy:
  44 //   AbstractGangWorker (subclass of WorkerThread)
  45 //     GangWorker
  46 //     YieldingFlexibleGangWorker   (defined in another file)
  47 
  48 // Forward declarations of classes defined here
  49 
  50 class AbstractGangWorker;
  51 class Semaphore;
  52 class WorkGang;
  53 
  54 // An abstract task to be worked on by a gang.
  55 // You subclass this to supply your own work() method
  56 class AbstractGangTask VALUE_OBJ_CLASS_SPEC {
  57   const char* _name;
  58   const uint _gc_id;
  59 
  60  public:
  61   AbstractGangTask(const char* name) :
  62     _name(name),
  63     _gc_id(GCId::current_raw())
  64  {}
  65 
  66   // The abstract work method.
  67   // The argument tells you which member of the gang you are.
  68   virtual void work(uint worker_id) = 0;
  69 
  70   // Debugging accessor for the name.
  71   const char* name() const { return _name; }
  72   const uint gc_id() const { return _gc_id; }
  73 };
  74 
  75 struct WorkData {
  76   AbstractGangTask* _task;
  77   uint              _worker_id;
  78   WorkData(AbstractGangTask* task, uint worker_id) : _task(task), _worker_id(worker_id) {}
  79 };
  80 
  81 // Interface to handle the synchronization between the coordinator thread and the worker threads,
  82 // when a task is dispatched out to the worker threads.
  83 class GangTaskDispatcher : public CHeapObj<mtGC> {
  84  public:
  85   virtual ~GangTaskDispatcher() {}
  86 
  87   // Coordinator API.
  88 
  89   // Distributes the task out to num_workers workers.
  90   // Returns when the task has been completed by all workers.
  91   virtual void coordinator_execute_on_workers(AbstractGangTask* task, uint num_workers) = 0;
  92 
  93   // Worker API.
  94 
  95   // Waits for a task to become available to the worker.
  96   // Returns when the worker has been assigned a task.
  97   virtual WorkData worker_wait_for_task() = 0;
  98 
  99   // Signal to the coordinator that the worker is done with the assigned task.
 100   virtual void     worker_done_with_task() = 0;
 101 };
 102 
 103 // The work gang is the collection of workers to execute tasks.
 104 // The number of workers run for a task is "_active_workers"
 105 // while "_total_workers" is the number of available of workers.
 106 class AbstractWorkGang : public CHeapObj<mtInternal> {
 107  protected:
 108   // The array of worker threads for this gang.
 109   AbstractGangWorker** _workers;
 110   // The count of the number of workers in the gang.
 111   uint _total_workers;
 112   // The currently active workers in this gang.
 113   uint _active_workers;
 114   // Printing support.
 115   const char* _name;
 116 
 117  private:
 118   // Initialize only instance data.
 119   const bool _are_GC_task_threads;
 120   const bool _are_ConcurrentGC_threads;
 121 
 122  public:
 123   AbstractWorkGang(const char* name, uint workers, bool are_GC_task_threads, bool are_ConcurrentGC_threads) :
 124       _name(name),
 125       _total_workers(workers),
 126       _active_workers(UseDynamicNumberOfGCThreads ? 1U : workers),
 127       _are_GC_task_threads(are_GC_task_threads),
 128       _are_ConcurrentGC_threads(are_ConcurrentGC_threads)
 129   { }
 130 
 131   // Initialize workers in the gang.  Return true if initialization succeeded.
 132   bool initialize_workers();
 133 
 134   bool are_GC_task_threads()      const { return _are_GC_task_threads; }
 135   bool are_ConcurrentGC_threads() const { return _are_ConcurrentGC_threads; }
 136 
 137   uint total_workers() const { return _total_workers; }
 138 
 139   virtual uint active_workers() const {
 140     assert(_active_workers <= _total_workers,
 141            "_active_workers: %u > _total_workers: %u", _active_workers, _total_workers);
 142     assert(UseDynamicNumberOfGCThreads || _active_workers == _total_workers,
 143            "Unless dynamic should use total workers");
 144     return _active_workers;
 145   }
 146   void set_active_workers(uint v) {
 147     assert(v <= _total_workers,
 148            "Trying to set more workers active than there are");
 149     _active_workers = MIN2(v, _total_workers);
 150     assert(v != 0, "Trying to set active workers to 0");
 151     _active_workers = MAX2(1U, _active_workers);
 152     assert(UseDynamicNumberOfGCThreads || _active_workers == _total_workers,
 153            "Unless dynamic should use total workers");
 154   }
 155 
 156   // Return the Ith worker.
 157   AbstractGangWorker* worker(uint i) const;
 158 
 159   void threads_do(ThreadClosure* tc) const;
 160 
 161   // Debugging.
 162   const char* name() const { return _name; }
 163 
 164   // Printing
 165   void print_worker_threads_on(outputStream *st) const;
 166   void print_worker_threads() const {
 167     print_worker_threads_on(tty);
 168   }
 169 
 170  protected:
 171   virtual AbstractGangWorker* allocate_worker(uint which) = 0;
 172 };
 173 
 174 // An class representing a gang of workers.
 175 class WorkGang: public AbstractWorkGang {
 176   // To get access to the GangTaskDispatcher instance.
 177   friend class GangWorker;
 178 
 179   // Never deleted.
 180   ~WorkGang();
 181 
 182   GangTaskDispatcher* const _dispatcher;
 183   GangTaskDispatcher* dispatcher() const {
 184     return _dispatcher;
 185   }
 186 
 187 public:
 188   WorkGang(const char* name,
 189            uint workers,
 190            bool are_GC_task_threads,
 191            bool are_ConcurrentGC_threads);
 192 
 193   // Run a task, returns when the task is done.
 194   virtual void run_task(AbstractGangTask* task);
 195 
 196 protected:
 197   virtual AbstractGangWorker* allocate_worker(uint which);
 198 };
 199 
 200 // Several instances of this class run in parallel as workers for a gang.
 201 class AbstractGangWorker: public WorkerThread {
 202 public:
 203   AbstractGangWorker(AbstractWorkGang* gang, uint id);
 204 
 205   // The only real method: run a task for the gang.
 206   virtual void run();
 207   // Predicate for Thread
 208   virtual bool is_GC_task_thread() const;
 209   virtual bool is_ConcurrentGC_thread() const;
 210   // Printing
 211   void print_on(outputStream* st) const;
 212   virtual void print() const { print_on(tty); }
 213 
 214 protected:
 215   AbstractWorkGang* _gang;
 216 
 217   virtual void initialize();
 218   virtual void loop() = 0;
 219 
 220   AbstractWorkGang* gang() const { return _gang; }
 221 };
 222 
 223 class GangWorker: public AbstractGangWorker {
 224 public:
 225   GangWorker(WorkGang* gang, uint id) : AbstractGangWorker(gang, id) {}
 226 
 227 protected:
 228   virtual void loop();
 229 
 230 private:
 231   WorkData wait_for_task();
 232   void run_task(WorkData work);
 233   void signal_task_done();
 234 
 235   void print_task_started(WorkData data);
 236   void print_task_done(WorkData data);
 237 
 238   WorkGang* gang() const { return (WorkGang*)_gang; }
 239 };
 240 
 241 // A class that acts as a synchronisation barrier. Workers enter
 242 // the barrier and must wait until all other workers have entered
 243 // before any of them may leave.
 244 
 245 class WorkGangBarrierSync : public StackObj {
 246 protected:
 247   Monitor _monitor;
 248   uint    _n_workers;
 249   uint    _n_completed;
 250   bool    _should_reset;
 251   bool    _aborted;
 252 
 253   Monitor* monitor()        { return &_monitor; }
 254   uint     n_workers()      { return _n_workers; }
 255   uint     n_completed()    { return _n_completed; }
 256   bool     should_reset()   { return _should_reset; }
 257   bool     aborted()        { return _aborted; }
 258 
 259   void     zero_completed() { _n_completed = 0; }
 260   void     inc_completed()  { _n_completed++; }
 261   void     set_aborted()    { _aborted = true; }
 262   void     set_should_reset(bool v) { _should_reset = v; }
 263 
 264 public:
 265   WorkGangBarrierSync();
 266   WorkGangBarrierSync(uint n_workers, const char* name);
 267 
 268   // Set the number of workers that will use the barrier.
 269   // Must be called before any of the workers start running.
 270   void set_n_workers(uint n_workers);
 271 
 272   // Enter the barrier. A worker that enters the barrier will
 273   // not be allowed to leave until all other threads have
 274   // also entered the barrier or the barrier is aborted.
 275   // Returns false if the barrier was aborted.
 276   bool enter();
 277 
 278   // Aborts the barrier and wakes up any threads waiting for
 279   // the barrier to complete. The barrier will remain in the
 280   // aborted state until the next call to set_n_workers().
 281   void abort();
 282 };
 283 
 284 // A class to manage claiming of subtasks within a group of tasks.  The
 285 // subtasks will be identified by integer indices, usually elements of an
 286 // enumeration type.
 287 
 288 class SubTasksDone: public CHeapObj<mtInternal> {
 289   uint* _tasks;
 290   uint _n_tasks;
 291   uint _threads_completed;
 292 #ifdef ASSERT
 293   volatile uint _claimed;
 294 #endif
 295 
 296   // Set all tasks to unclaimed.
 297   void clear();
 298 
 299 public:
 300   // Initializes "this" to a state in which there are "n" tasks to be
 301   // processed, none of the which are originally claimed.  The number of
 302   // threads doing the tasks is initialized 1.
 303   SubTasksDone(uint n);
 304 
 305   // True iff the object is in a valid state.
 306   bool valid();
 307 
 308   // Returns "false" if the task "t" is unclaimed, and ensures that task is
 309   // claimed.  The task "t" is required to be within the range of "this".
 310   bool is_task_claimed(uint t);
 311 
 312   // The calling thread asserts that it has attempted to claim all the
 313   // tasks that it will try to claim.  Every thread in the parallel task
 314   // must execute this.  (When the last thread does so, the task array is
 315   // cleared.)
 316   //
 317   // n_threads - Number of threads executing the sub-tasks.
 318   void all_tasks_completed(uint n_threads);
 319 
 320   // Destructor.
 321   ~SubTasksDone();
 322 };
 323 
 324 // As above, but for sequential tasks, i.e. instead of claiming
 325 // sub-tasks from a set (possibly an enumeration), claim sub-tasks
 326 // in sequential order. This is ideal for claiming dynamically
 327 // partitioned tasks (like striding in the parallel remembered
 328 // set scanning). Note that unlike the above class this is
 329 // a stack object - is there any reason for it not to be?
 330 
 331 class SequentialSubTasksDone : public StackObj {
 332 protected:
 333   uint _n_tasks;     // Total number of tasks available.
 334   uint _n_claimed;   // Number of tasks claimed.
 335   // _n_threads is used to determine when a sub task is done.
 336   // See comments on SubTasksDone::_n_threads
 337   uint _n_threads;   // Total number of parallel threads.
 338   uint _n_completed; // Number of completed threads.
 339 
 340   void clear();
 341 
 342 public:
 343   SequentialSubTasksDone() {
 344     clear();
 345   }
 346   ~SequentialSubTasksDone() {}
 347 
 348   // True iff the object is in a valid state.
 349   bool valid();
 350 
 351   // number of tasks
 352   uint n_tasks() const { return _n_tasks; }
 353 
 354   // Get/set the number of parallel threads doing the tasks to t.
 355   // Should be called before the task starts but it is safe
 356   // to call this once a task is running provided that all
 357   // threads agree on the number of threads.
 358   uint n_threads() { return _n_threads; }
 359   void set_n_threads(uint t) { _n_threads = t; }
 360 
 361   // Set the number of tasks to be claimed to t. As above,
 362   // should be called before the tasks start but it is safe
 363   // to call this once a task is running provided all threads
 364   // agree on the number of tasks.
 365   void set_n_tasks(uint t) { _n_tasks = t; }
 366 
 367   // Returns false if the next task in the sequence is unclaimed,
 368   // and ensures that it is claimed. Will set t to be the index
 369   // of the claimed task in the sequence. Will return true if
 370   // the task cannot be claimed and there are none left to claim.
 371   bool is_task_claimed(uint& t);
 372 
 373   // The calling thread asserts that it has attempted to claim
 374   // all the tasks it possibly can in the sequence. Every thread
 375   // claiming tasks must promise call this. Returns true if this
 376   // is the last thread to complete so that the thread can perform
 377   // cleanup if necessary.
 378   bool all_tasks_completed();
 379 };
 380 
 381 // Represents a set of free small integer ids.
 382 class FreeIdSet : public CHeapObj<mtGC> {
 383   enum {
 384     end_of_list = UINT_MAX,
 385     claimed = UINT_MAX - 1
 386   };
 387 
 388   uint _size;
 389   Monitor* _mon;
 390 
 391   uint* _ids;
 392   uint _hd;
 393   uint _waiters;
 394   uint _claimed;
 395 
 396 public:
 397   FreeIdSet(uint size, Monitor* mon);
 398   ~FreeIdSet();
 399 
 400   // Returns an unclaimed parallel id (waiting for one to be released if
 401   // necessary).  Returns "UINT_MAX" if a GC wakes up a wait for an id.
 402   uint claim_par_id();
 403 
 404   void release_par_id(uint id);
 405 };
 406 
 407 #endif // SHARE_VM_GC_SHARED_WORKGROUP_HPP