1 /*
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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_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 "utilities/debug.hpp"
  32 #include "utilities/globalDefinitions.hpp"
  33 
  34 // Task class hierarchy:
  35 //   AbstractGangTask
  36 //
  37 // Gang/Group class hierarchy:
  38 //   AbstractWorkGang
  39 //     WorkGang
  40 //     YieldingFlexibleWorkGang (defined in another file)
  41 //
  42 // Worker class hierarchy:
  43 //   AbstractGangWorker (subclass of WorkerThread)
  44 //     GangWorker
  45 //     YieldingFlexibleGangWorker   (defined in another file)
  46 
  47 // Forward declarations of classes defined here
  48 
  49 class AbstractGangWorker;
  50 class Semaphore;
  51 class WorkGang;
  52 
  53 // An abstract task to be worked on by a gang.
  54 // You subclass this to supply your own work() method
  55 class AbstractGangTask VALUE_OBJ_CLASS_SPEC {
  56   const char* _name;
  57 
  58  public:
  59   AbstractGangTask(const char* name) : _name(name) {}
  60 
  61   // The abstract work method.
  62   // The argument tells you which member of the gang you are.
  63   virtual void work(uint worker_id) = 0;
  64 
  65   // Debugging accessor for the name.
  66   const char* name() const { return _name; }
  67 };
  68 
  69 struct WorkData {
  70   AbstractGangTask* _task;
  71   uint              _worker_id;
  72   WorkData(AbstractGangTask* task, uint worker_id) : _task(task), _worker_id(worker_id) {}
  73 };
  74 
  75 // Interface to handle the synchronization between the coordinator thread and the worker threads,
  76 // when a task is dispatched out to the worker threads.
  77 class GangTaskDispatcher : public CHeapObj<mtGC> {
  78  public:
  79   virtual ~GangTaskDispatcher() {}
  80 
  81   // Coordinator API.
  82 
  83   // Distributes the task out to num_workers workers.
  84   // Returns when the task has been completed by all workers.
  85   virtual void coordinator_execute_on_workers(AbstractGangTask* task, uint num_workers) = 0;
  86 
  87   // Worker API.
  88 
  89   // Waits for a task to become available to the worker.
  90   // Returns when the worker has been assigned a task.
  91   virtual WorkData worker_wait_for_task() = 0;
  92 
  93   // Signal to the coordinator that the worker is done with the assigned task.
  94   virtual void     worker_done_with_task() = 0;
  95 };
  96 
  97 // The work gang is the collection of workers to execute tasks.
  98 // The number of workers run for a task is "_active_workers"
  99 // while "_total_workers" is the number of available of workers.
 100 class AbstractWorkGang : public CHeapObj<mtInternal> {
 101  protected:
 102   // The array of worker threads for this gang.
 103   AbstractGangWorker** _workers;
 104   // The count of the number of workers in the gang.
 105   uint _total_workers;
 106   // The currently active workers in this gang.
 107   uint _active_workers;
 108   // Printing support.
 109   const char* _name;
 110 
 111  private:
 112   // Initialize only instance data.
 113   const bool _are_GC_task_threads;
 114   const bool _are_ConcurrentGC_threads;
 115 
 116  public:
 117   AbstractWorkGang(const char* name, uint workers, bool are_GC_task_threads, bool are_ConcurrentGC_threads) :
 118       _name(name),
 119       _total_workers(workers),
 120       _active_workers(UseDynamicNumberOfGCThreads ? 1U : workers),
 121       _are_GC_task_threads(are_GC_task_threads),
 122       _are_ConcurrentGC_threads(are_ConcurrentGC_threads)
 123   { }
 124 
 125   // Initialize workers in the gang.  Return true if initialization succeeded.
 126   bool initialize_workers();
 127 
 128   bool are_GC_task_threads()      const { return _are_GC_task_threads; }
 129   bool are_ConcurrentGC_threads() const { return _are_ConcurrentGC_threads; }
 130 
 131   uint total_workers() const { return _total_workers; }
 132 
 133   virtual uint active_workers() const {
 134     assert(_active_workers <= _total_workers,
 135            err_msg("_active_workers: %u > _total_workers: %u", _active_workers, _total_workers));
 136     assert(UseDynamicNumberOfGCThreads || _active_workers == _total_workers,
 137            "Unless dynamic should use total workers");
 138     return _active_workers;
 139   }
 140   void set_active_workers(uint v) {
 141     assert(v <= _total_workers,
 142            "Trying to set more workers active than there are");
 143     _active_workers = MIN2(v, _total_workers);
 144     assert(v != 0, "Trying to set active workers to 0");
 145     _active_workers = MAX2(1U, _active_workers);
 146     assert(UseDynamicNumberOfGCThreads || _active_workers == _total_workers,
 147            "Unless dynamic should use total workers");
 148   }
 149 
 150   // Return the Ith worker.
 151   AbstractGangWorker* worker(uint i) const;
 152 
 153   void threads_do(ThreadClosure* tc) const;
 154 
 155   // Debugging.
 156   const char* name() const { return _name; }
 157 
 158   // Printing
 159   void print_worker_threads_on(outputStream *st) const;
 160   void print_worker_threads() const {
 161     print_worker_threads_on(tty);
 162   }
 163 
 164  protected:
 165   virtual AbstractGangWorker* allocate_worker(uint which) = 0;
 166 };
 167 
 168 // An class representing a gang of workers.
 169 class WorkGang: public AbstractWorkGang {
 170   // To get access to the GangTaskDispatcher instance.
 171   friend class GangWorker;
 172 
 173   // Never deleted.
 174   ~WorkGang();
 175 
 176   GangTaskDispatcher* const _dispatcher;
 177   GangTaskDispatcher* dispatcher()const {
 178     return _dispatcher;
 179   }
 180 
 181 public:
 182   WorkGang(const char* name,
 183            uint workers,
 184            bool are_GC_task_threads,
 185            bool are_ConcurrentGC_threads,
 186            GangTaskDispatcher* dispatcher = NULL);
 187 
 188   // Run a task, returns when the task is done.
 189   virtual void run_task(AbstractGangTask* task);
 190 
 191 protected:
 192   virtual AbstractGangWorker* allocate_worker(uint which);
 193 
 194 private:
 195   void print_worker_started_task(AbstractGangTask* task, uint worker_id);
 196   void print_worker_finished_task(AbstractGangTask* task, uint worker_id);
 197 };
 198 
 199 // Several instances of this class run in parallel as workers for a gang.
 200 class AbstractGangWorker: public WorkerThread {
 201 public:
 202   AbstractGangWorker(AbstractWorkGang* gang, uint id);
 203 
 204   // The only real method: run a task for the gang.
 205   virtual void run();
 206   // Predicate for Thread
 207   virtual bool is_GC_task_thread() const;
 208   virtual bool is_ConcurrentGC_thread() const;
 209   // Printing
 210   void print_on(outputStream* st) const;
 211   virtual void print() const { print_on(tty); }
 212 
 213 protected:
 214   AbstractWorkGang* _gang;
 215 
 216   virtual void initialize();
 217   virtual void loop() = 0;
 218 
 219   AbstractWorkGang* gang() const { return _gang; }
 220 };
 221 
 222 class GangWorker: public AbstractGangWorker {
 223 public:
 224   GangWorker(WorkGang* gang, uint id) : AbstractGangWorker(gang, id) {}
 225 
 226 protected:
 227   virtual void loop();
 228 
 229 private:
 230   WorkData wait_for_task();
 231   void run_task(WorkData work);
 232   void signal_task_done();
 233 
 234   void print_task_started(WorkData data);
 235   void print_task_done(WorkData data);
 236 
 237   WorkGang* gang() const { return (WorkGang*)_gang; }
 238 };
 239 
 240 // A class that acts as a synchronisation barrier. Workers enter
 241 // the barrier and must wait until all other workers have entered
 242 // before any of them may leave.
 243 
 244 class WorkGangBarrierSync : public StackObj {
 245 protected:
 246   Monitor _monitor;
 247   uint    _n_workers;
 248   uint    _n_completed;
 249   bool    _should_reset;
 250   bool    _aborted;
 251 
 252   Monitor* monitor()        { return &_monitor; }
 253   uint     n_workers()      { return _n_workers; }
 254   uint     n_completed()    { return _n_completed; }
 255   bool     should_reset()   { return _should_reset; }
 256   bool     aborted()        { return _aborted; }
 257 
 258   void     zero_completed() { _n_completed = 0; }
 259   void     inc_completed()  { _n_completed++; }
 260   void     set_aborted()    { _aborted = true; }
 261   void     set_should_reset(bool v) { _should_reset = v; }
 262 
 263 public:
 264   WorkGangBarrierSync();
 265   WorkGangBarrierSync(uint n_workers, const char* name);
 266 
 267   // Set the number of workers that will use the barrier.
 268   // Must be called before any of the workers start running.
 269   void set_n_workers(uint n_workers);
 270 
 271   // Enter the barrier. A worker that enters the barrier will
 272   // not be allowed to leave until all other threads have
 273   // also entered the barrier or the barrier is aborted.
 274   // Returns false if the barrier was aborted.
 275   bool enter();
 276 
 277   // Aborts the barrier and wakes up any threads waiting for
 278   // the barrier to complete. The barrier will remain in the
 279   // aborted state until the next call to set_n_workers().
 280   void abort();
 281 };
 282 
 283 // A class to manage claiming of subtasks within a group of tasks.  The
 284 // subtasks will be identified by integer indices, usually elements of an
 285 // enumeration type.
 286 
 287 class SubTasksDone: public CHeapObj<mtInternal> {
 288   uint* _tasks;
 289   uint _n_tasks;
 290   uint _threads_completed;
 291 #ifdef ASSERT
 292   volatile uint _claimed;
 293 #endif
 294 
 295   // Set all tasks to unclaimed.
 296   void clear();
 297 
 298 public:
 299   // Initializes "this" to a state in which there are "n" tasks to be
 300   // processed, none of the which are originally claimed.  The number of
 301   // threads doing the tasks is initialized 1.
 302   SubTasksDone(uint n);
 303 
 304   // True iff the object is in a valid state.
 305   bool valid();
 306 
 307   // Returns "false" if the task "t" is unclaimed, and ensures that task is
 308   // claimed.  The task "t" is required to be within the range of "this".
 309   bool is_task_claimed(uint t);
 310 
 311   // The calling thread asserts that it has attempted to claim all the
 312   // tasks that it will try to claim.  Every thread in the parallel task
 313   // must execute this.  (When the last thread does so, the task array is
 314   // cleared.)
 315   //
 316   // n_threads - Number of threads executing the sub-tasks.
 317   void all_tasks_completed(uint n_threads);
 318 
 319   // Destructor.
 320   ~SubTasksDone();
 321 };
 322 
 323 // As above, but for sequential tasks, i.e. instead of claiming
 324 // sub-tasks from a set (possibly an enumeration), claim sub-tasks
 325 // in sequential order. This is ideal for claiming dynamically
 326 // partitioned tasks (like striding in the parallel remembered
 327 // set scanning). Note that unlike the above class this is
 328 // a stack object - is there any reason for it not to be?
 329 
 330 class SequentialSubTasksDone : public StackObj {
 331 protected:
 332   uint _n_tasks;     // Total number of tasks available.
 333   uint _n_claimed;   // Number of tasks claimed.
 334   // _n_threads is used to determine when a sub task is done.
 335   // See comments on SubTasksDone::_n_threads
 336   uint _n_threads;   // Total number of parallel threads.
 337   uint _n_completed; // Number of completed threads.
 338 
 339   void clear();
 340 
 341 public:
 342   SequentialSubTasksDone() {
 343     clear();
 344   }
 345   ~SequentialSubTasksDone() {}
 346 
 347   // True iff the object is in a valid state.
 348   bool valid();
 349 
 350   // number of tasks
 351   uint n_tasks() const { return _n_tasks; }
 352 
 353   // Get/set the number of parallel threads doing the tasks to t.
 354   // Should be called before the task starts but it is safe
 355   // to call this once a task is running provided that all
 356   // threads agree on the number of threads.
 357   uint n_threads() { return _n_threads; }
 358   void set_n_threads(uint t) { _n_threads = t; }
 359 
 360   // Set the number of tasks to be claimed to t. As above,
 361   // should be called before the tasks start but it is safe
 362   // to call this once a task is running provided all threads
 363   // agree on the number of tasks.
 364   void set_n_tasks(uint t) { _n_tasks = t; }
 365 
 366   // Returns false if the next task in the sequence is unclaimed,
 367   // and ensures that it is claimed. Will set t to be the index
 368   // of the claimed task in the sequence. Will return true if
 369   // the task cannot be claimed and there are none left to claim.
 370   bool is_task_claimed(uint& t);
 371 
 372   // The calling thread asserts that it has attempted to claim
 373   // all the tasks it possibly can in the sequence. Every thread
 374   // claiming tasks must promise call this. Returns true if this
 375   // is the last thread to complete so that the thread can perform
 376   // cleanup if necessary.
 377   bool all_tasks_completed();
 378 };
 379 
 380 // Represents a set of free small integer ids.
 381 class FreeIdSet : public CHeapObj<mtInternal> {
 382   enum {
 383     end_of_list = -1,
 384     claimed = -2
 385   };
 386 
 387   int _sz;
 388   Monitor* _mon;
 389 
 390   int* _ids;
 391   int _hd;
 392   int _waiters;
 393   int _claimed;
 394 
 395   static bool _safepoint;
 396   typedef FreeIdSet* FreeIdSetPtr;
 397   static const int NSets = 10;
 398   static FreeIdSetPtr _sets[NSets];
 399   static bool _stat_init;
 400   int _index;
 401 
 402 public:
 403   FreeIdSet(int sz, Monitor* mon);
 404   ~FreeIdSet();
 405 
 406   static void set_safepoint(bool b);
 407 
 408   // Attempt to claim the given id permanently.  Returns "true" iff
 409   // successful.
 410   bool claim_perm_id(int i);
 411 
 412   // Returns an unclaimed parallel id (waiting for one to be released if
 413   // necessary).  Returns "-1" if a GC wakes up a wait for an id.
 414   int claim_par_id();
 415 
 416   void release_par_id(int id);
 417 };
 418 
 419 #endif // SHARE_VM_GC_SHARED_WORKGROUP_HPP