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  12  * version 2 for more details (a copy is included in the LICENSE file that
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  24 
  25 #ifndef SHARE_VM_UTILITIES_WORKGROUP_HPP
  26 #define SHARE_VM_UTILITIES_WORKGROUP_HPP
  27 
  28 #include "runtime/thread.inline.hpp"
  29 #include "utilities/taskqueue.hpp"
  30 
  31 // Task class hierarchy:
  32 //   AbstractGangTask
  33 //     AbstractGangTaskWOopQueues
  34 //
  35 // Gang/Group class hierarchy:
  36 //   AbstractWorkGang
  37 //     WorkGang
  38 //       FlexibleWorkGang
  39 //         YieldingFlexibleWorkGang (defined in another file)
  40 //
  41 // Worker class hierarchy:
  42 //   GangWorker (subclass of WorkerThread)
  43 //     YieldingFlexibleGangWorker   (defined in another file)
  44 
  45 // Forward declarations of classes defined here
  46 
  47 class WorkGang;
  48 class GangWorker;
  49 class YieldingFlexibleGangWorker;
  50 class YieldingFlexibleGangTask;
  51 class WorkData;
  52 class AbstractWorkGang;
  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 public:
  58   // The abstract work method.
  59   // The argument tells you which member of the gang you are.
  60   virtual void work(uint worker_id) = 0;
  61 
  62   // This method configures the task for proper termination.
  63   // Some tasks do not have any requirements on termination
  64   // and may inherit this method that does nothing.  Some
  65   // tasks do some coordination on termination and override
  66   // this method to implement that coordination.
  67   virtual void set_for_termination(int active_workers) {};
  68 
  69   // Debugging accessor for the name.
  70   const char* name() const PRODUCT_RETURN_(return NULL;);
  71   int counter() { return _counter; }
  72   void set_counter(int value) { _counter = value; }
  73   int *address_of_counter() { return &_counter; }
  74 
  75   // RTTI
  76   NOT_PRODUCT(virtual bool is_YieldingFlexibleGang_task() const {
  77     return false;
  78   })
  79 
  80 private:
  81   NOT_PRODUCT(const char* _name;)
  82   // ??? Should a task have a priority associated with it?
  83   // ??? Or can the run method adjust priority as needed?
  84   int _counter;
  85 
  86 protected:
  87   // Constructor and desctructor: only construct subclasses.
  88   AbstractGangTask(const char* name)
  89   {
  90     NOT_PRODUCT(_name = name);
  91     _counter = 0;
  92   }
  93   virtual ~AbstractGangTask() { }
  94 
  95 public:
  96 };
  97 
  98 class AbstractGangTaskWOopQueues : public AbstractGangTask {
  99   OopTaskQueueSet*       _queues;
 100   ParallelTaskTerminator _terminator;
 101  public:
 102   AbstractGangTaskWOopQueues(const char* name, OopTaskQueueSet* queues) :
 103     AbstractGangTask(name), _queues(queues), _terminator(0, _queues) {}
 104   ParallelTaskTerminator* terminator() { return &_terminator; }
 105   virtual void set_for_termination(int active_workers) {
 106     terminator()->reset_for_reuse(active_workers);
 107   }
 108   OopTaskQueueSet* queues() { return _queues; }
 109 };
 110 
 111 
 112 // Class AbstractWorkGang:
 113 // An abstract class representing a gang of workers.
 114 // You subclass this to supply an implementation of run_task().
 115 class AbstractWorkGang: public CHeapObj<mtInternal> {
 116   // Here's the public interface to this class.
 117 public:
 118   // Constructor and destructor.
 119   AbstractWorkGang(const char* name, bool are_GC_task_threads,
 120                    bool are_ConcurrentGC_threads);
 121   ~AbstractWorkGang();
 122   // Run a task, returns when the task is done (or terminated).
 123   virtual void run_task(AbstractGangTask* task) = 0;
 124   // Stop and terminate all workers.
 125   virtual void stop();
 126   // Return true if more workers should be applied to the task.
 127   virtual bool needs_more_workers() const { return true; }
 128 public:
 129   // Debugging.
 130   const char* name() const;
 131 protected:
 132   // Initialize only instance data.
 133   const bool _are_GC_task_threads;
 134   const bool _are_ConcurrentGC_threads;
 135   // Printing support.
 136   const char* _name;
 137   // The monitor which protects these data,
 138   // and notifies of changes in it.
 139   Monitor*  _monitor;
 140   // The count of the number of workers in the gang.
 141   uint _total_workers;
 142   // Whether the workers should terminate.
 143   bool _terminate;
 144   // The array of worker threads for this gang.
 145   // This is only needed for cleaning up.
 146   GangWorker** _gang_workers;
 147   // The task for this gang.
 148   AbstractGangTask* _task;
 149   // A sequence number for the current task.
 150   int _sequence_number;
 151   // The number of started workers.
 152   uint _started_workers;
 153   // The number of finished workers.
 154   uint _finished_workers;
 155 public:
 156   // Accessors for fields
 157   Monitor* monitor() const {
 158     return _monitor;
 159   }
 160   uint total_workers() const {
 161     return _total_workers;
 162   }
 163   virtual uint active_workers() const {
 164     return _total_workers;
 165   }
 166   bool terminate() const {
 167     return _terminate;
 168   }
 169   GangWorker** gang_workers() const {
 170     return _gang_workers;
 171   }
 172   AbstractGangTask* task() const {
 173     return _task;
 174   }
 175   int sequence_number() const {
 176     return _sequence_number;
 177   }
 178   uint started_workers() const {
 179     return _started_workers;
 180   }
 181   uint finished_workers() const {
 182     return _finished_workers;
 183   }
 184   bool are_GC_task_threads() const {
 185     return _are_GC_task_threads;
 186   }
 187   bool are_ConcurrentGC_threads() const {
 188     return _are_ConcurrentGC_threads;
 189   }
 190   // Predicates.
 191   bool is_idle() const {
 192     return (task() == NULL);
 193   }
 194   // Return the Ith gang worker.
 195   GangWorker* gang_worker(uint i) const;
 196 
 197   void threads_do(ThreadClosure* tc) const;
 198 
 199   // Printing
 200   void print_worker_threads_on(outputStream *st) const;
 201   void print_worker_threads() const {
 202     print_worker_threads_on(tty);
 203   }
 204 
 205 protected:
 206   friend class GangWorker;
 207   friend class YieldingFlexibleGangWorker;
 208   // Note activation and deactivation of workers.
 209   // These methods should only be called with the mutex held.
 210   void internal_worker_poll(WorkData* data) const;
 211   void internal_note_start();
 212   void internal_note_finish();
 213 };
 214 
 215 class WorkData: public StackObj {
 216   // This would be a struct, but I want accessor methods.
 217 private:
 218   bool              _terminate;
 219   AbstractGangTask* _task;
 220   int               _sequence_number;
 221 public:
 222   // Constructor and destructor
 223   WorkData() {
 224     _terminate       = false;
 225     _task            = NULL;
 226     _sequence_number = 0;
 227   }
 228   ~WorkData() {
 229   }
 230   // Accessors and modifiers
 231   bool terminate()                       const { return _terminate;  }
 232   void set_terminate(bool value)               { _terminate = value; }
 233   AbstractGangTask* task()               const { return _task; }
 234   void set_task(AbstractGangTask* value)       { _task = value; }
 235   int sequence_number()                  const { return _sequence_number; }
 236   void set_sequence_number(int value)          { _sequence_number = value; }
 237 
 238   YieldingFlexibleGangTask* yf_task()    const {
 239     return (YieldingFlexibleGangTask*)_task;
 240   }
 241 };
 242 
 243 // Class WorkGang:
 244 class WorkGang: public AbstractWorkGang {
 245 public:
 246   // Constructor
 247   WorkGang(const char* name, uint workers,
 248            bool are_GC_task_threads, bool are_ConcurrentGC_threads);
 249   // Run a task, returns when the task is done (or terminated).
 250   virtual void run_task(AbstractGangTask* task);
 251   void run_task(AbstractGangTask* task, uint no_of_parallel_workers);
 252   // Allocate a worker and return a pointer to it.
 253   virtual GangWorker* allocate_worker(uint which);
 254   // Initialize workers in the gang.  Return true if initialization
 255   // succeeded. The type of the worker can be overridden in a derived
 256   // class with the appropriate implementation of allocate_worker().
 257   bool initialize_workers();
 258 };
 259 
 260 // Class GangWorker:
 261 //   Several instances of this class run in parallel as workers for a gang.
 262 class GangWorker: public WorkerThread {
 263 public:
 264   // Constructors and destructor.
 265   GangWorker(AbstractWorkGang* gang, uint id);
 266 
 267   // The only real method: run a task for the gang.
 268   virtual void run();
 269   // Predicate for Thread
 270   virtual bool is_GC_task_thread() const;
 271   virtual bool is_ConcurrentGC_thread() const;
 272   // Printing
 273   void print_on(outputStream* st) const;
 274   virtual void print() const { print_on(tty); }
 275 protected:
 276   AbstractWorkGang* _gang;
 277 
 278   virtual void initialize();
 279   virtual void loop();
 280 
 281 public:
 282   AbstractWorkGang* gang() const { return _gang; }
 283 };
 284 
 285 // Dynamic number of worker threads
 286 //
 287 // This type of work gang is used to run different numbers of
 288 // worker threads at different times.  The
 289 // number of workers run for a task is "_active_workers"
 290 // instead of "_total_workers" in a WorkGang.  The method
 291 // "needs_more_workers()" returns true until "_active_workers"
 292 // have been started and returns false afterwards.  The
 293 // implementation of "needs_more_workers()" in WorkGang always
 294 // returns true so that all workers are started.  The method
 295 // "loop()" in GangWorker was modified to ask "needs_more_workers()"
 296 // in its loop to decide if it should start working on a task.
 297 // A worker in "loop()" waits for notification on the WorkGang
 298 // monitor and execution of each worker as it checks for work
 299 // is serialized via the same monitor.  The "needs_more_workers()"
 300 // call is serialized and additionally the calculation for the
 301 // "part" (effectively the worker id for executing the task) is
 302 // serialized to give each worker a unique "part".  Workers that
 303 // are not needed for this tasks (i.e., "_active_workers" have
 304 // been started before it, continue to wait for work.
 305 
 306 class FlexibleWorkGang: public WorkGang {
 307   // The currently active workers in this gang.
 308   // This is a number that is dynamically adjusted
 309   // and checked in the run_task() method at each invocation.
 310   // As described above _active_workers determines the number
 311   // of threads started on a task.  It must also be used to
 312   // determine completion.
 313 
 314  protected:
 315   uint _active_workers;
 316  public:
 317   // Constructor and destructor.
 318   // Initialize active_workers to a minimum value.  Setting it to
 319   // the parameter "workers" will initialize it to a maximum
 320   // value which is not desirable.
 321   FlexibleWorkGang(const char* name, uint workers,
 322                    bool are_GC_task_threads,
 323                    bool  are_ConcurrentGC_threads) :
 324     WorkGang(name, workers, are_GC_task_threads, are_ConcurrentGC_threads),
 325     _active_workers(UseDynamicNumberOfGCThreads ? 1U : ParallelGCThreads) {}
 326   // Accessors for fields
 327   virtual uint active_workers() const { return _active_workers; }
 328   void set_active_workers(uint v) {
 329     assert(v <= _total_workers,
 330            "Trying to set more workers active than there are");
 331     _active_workers = MIN2(v, _total_workers);
 332     assert(v != 0, "Trying to set active workers to 0");
 333     _active_workers = MAX2(1U, _active_workers);
 334     assert(UseDynamicNumberOfGCThreads || _active_workers == _total_workers,
 335            "Unless dynamic should use total workers");
 336   }
 337   virtual void run_task(AbstractGangTask* task);
 338   virtual bool needs_more_workers() const {
 339     return _started_workers < _active_workers;
 340   }
 341 };
 342 
 343 // Work gangs in garbage collectors: 2009-06-10
 344 //
 345 // SharedHeap - work gang for stop-the-world parallel collection.
 346 //   Used by
 347 //     ParNewGeneration
 348 //     CMSParRemarkTask
 349 //     CMSRefProcTaskExecutor
 350 //     G1CollectedHeap
 351 //     G1ParFinalCountTask
 352 // ConcurrentMark
 353 // CMSCollector
 354 
 355 // A class that acts as a synchronisation barrier. Workers enter
 356 // the barrier and must wait until all other workers have entered
 357 // before any of them may leave.
 358 
 359 class WorkGangBarrierSync : public StackObj {
 360 protected:
 361   Monitor _monitor;
 362   uint     _n_workers;
 363   uint     _n_completed;
 364   bool    _should_reset;
 365 
 366   Monitor* monitor()        { return &_monitor; }
 367   uint     n_workers()      { return _n_workers; }
 368   uint     n_completed()    { return _n_completed; }
 369   bool     should_reset()   { return _should_reset; }
 370 
 371   void     zero_completed() { _n_completed = 0; }
 372   void     inc_completed()  { _n_completed++; }
 373 
 374   void     set_should_reset(bool v) { _should_reset = v; }
 375 
 376 public:
 377   WorkGangBarrierSync();
 378   WorkGangBarrierSync(uint n_workers, const char* name);
 379 
 380   // Set the number of workers that will use the barrier.
 381   // Must be called before any of the workers start running.
 382   void set_n_workers(uint n_workers);
 383 
 384   // Enter the barrier. A worker that enters the barrier will
 385   // not be allowed to leave until all other threads have
 386   // also entered the barrier.
 387   void enter();
 388 };
 389 
 390 // A class to manage claiming of subtasks within a group of tasks.  The
 391 // subtasks will be identified by integer indices, usually elements of an
 392 // enumeration type.
 393 
 394 class SubTasksDone: public CHeapObj<mtInternal> {
 395   uint* _tasks;
 396   uint _n_tasks;
 397   // _n_threads is used to determine when a sub task is done.
 398   // It does not control how many threads will execute the subtask
 399   // but must be initialized to the number that do execute the task
 400   // in order to correctly decide when the subtask is done (all the
 401   // threads working on the task have finished).
 402   uint _n_threads;
 403   uint _threads_completed;
 404 #ifdef ASSERT
 405   volatile uint _claimed;
 406 #endif
 407 
 408   // Set all tasks to unclaimed.
 409   void clear();
 410 
 411 public:
 412   // Initializes "this" to a state in which there are "n" tasks to be
 413   // processed, none of the which are originally claimed.  The number of
 414   // threads doing the tasks is initialized 1.
 415   SubTasksDone(uint n);
 416 
 417   // True iff the object is in a valid state.
 418   bool valid();
 419 
 420   // Get/set the number of parallel threads doing the tasks to "t".  Can only
 421   // be called before tasks start or after they are complete.
 422   uint n_threads() { return _n_threads; }
 423   void set_n_threads(uint t);
 424 
 425   // Returns "false" if the task "t" is unclaimed, and ensures that task is
 426   // claimed.  The task "t" is required to be within the range of "this".
 427   bool is_task_claimed(uint t);
 428 
 429   // The calling thread asserts that it has attempted to claim all the
 430   // tasks that it will try to claim.  Every thread in the parallel task
 431   // must execute this.  (When the last thread does so, the task array is
 432   // cleared.)
 433   void all_tasks_completed();
 434 
 435   // Destructor.
 436   ~SubTasksDone();
 437 };
 438 
 439 // As above, but for sequential tasks, i.e. instead of claiming
 440 // sub-tasks from a set (possibly an enumeration), claim sub-tasks
 441 // in sequential order. This is ideal for claiming dynamically
 442 // partitioned tasks (like striding in the parallel remembered
 443 // set scanning). Note that unlike the above class this is
 444 // a stack object - is there any reason for it not to be?
 445 
 446 class SequentialSubTasksDone : public StackObj {
 447 protected:
 448   uint _n_tasks;     // Total number of tasks available.
 449   uint _n_claimed;   // Number of tasks claimed.
 450   // _n_threads is used to determine when a sub task is done.
 451   // See comments on SubTasksDone::_n_threads
 452   uint _n_threads;   // Total number of parallel threads.
 453   uint _n_completed; // Number of completed threads.
 454 
 455   void clear();
 456 
 457 public:
 458   SequentialSubTasksDone() {
 459     clear();
 460   }
 461   ~SequentialSubTasksDone() {}
 462 
 463   // True iff the object is in a valid state.
 464   bool valid();
 465 
 466   // number of tasks
 467   uint n_tasks() const { return _n_tasks; }
 468 
 469   // Get/set the number of parallel threads doing the tasks to t.
 470   // Should be called before the task starts but it is safe
 471   // to call this once a task is running provided that all
 472   // threads agree on the number of threads.
 473   uint n_threads() { return _n_threads; }
 474   void set_n_threads(uint t) { _n_threads = t; }
 475 
 476   // Set the number of tasks to be claimed to t. As above,
 477   // should be called before the tasks start but it is safe
 478   // to call this once a task is running provided all threads
 479   // agree on the number of tasks.
 480   void set_n_tasks(uint t) { _n_tasks = t; }
 481 
 482   // Returns false if the next task in the sequence is unclaimed,
 483   // and ensures that it is claimed. Will set t to be the index
 484   // of the claimed task in the sequence. Will return true if
 485   // the task cannot be claimed and there are none left to claim.
 486   bool is_task_claimed(uint& t);
 487 
 488   // The calling thread asserts that it has attempted to claim
 489   // all the tasks it possibly can in the sequence. Every thread
 490   // claiming tasks must promise call this. Returns true if this
 491   // is the last thread to complete so that the thread can perform
 492   // cleanup if necessary.
 493   bool all_tasks_completed();
 494 };
 495 
 496 // Represents a set of free small integer ids.
 497 class FreeIdSet {
 498   enum {
 499     end_of_list = -1,
 500     claimed = -2
 501   };
 502 
 503   int _sz;
 504   Monitor* _mon;
 505 
 506   int* _ids;
 507   int _hd;
 508   int _waiters;
 509   int _claimed;
 510 
 511   static bool _safepoint;
 512   typedef FreeIdSet* FreeIdSetPtr;
 513   static const int NSets = 10;
 514   static FreeIdSetPtr _sets[NSets];
 515   static bool _stat_init;
 516   int _index;
 517 
 518 public:
 519   FreeIdSet(int sz, Monitor* mon);
 520   ~FreeIdSet();
 521 
 522   static void set_safepoint(bool b);
 523 
 524   // Attempt to claim the given id permanently.  Returns "true" iff
 525   // successful.
 526   bool claim_perm_id(int i);
 527 
 528   // Returns an unclaimed parallel id (waiting for one to be released if
 529   // necessary).  Returns "-1" if a GC wakes up a wait for an id.
 530   int claim_par_id();
 531 
 532   void release_par_id(int id);
 533 };
 534 
 535 #endif // SHARE_VM_UTILITIES_WORKGROUP_HPP