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 
 187   // Run a task, returns when the task is done.
 188   virtual void run_task(AbstractGangTask* task);
 189 
 190 protected:
 191   virtual AbstractGangWorker* allocate_worker(uint which);
 192 
 193 private:
 194   void print_worker_started_task(AbstractGangTask* task, uint worker_id);
 195   void print_worker_finished_task(AbstractGangTask* task, uint worker_id);
 196 };
 197 
 198 // Several instances of this class run in parallel as workers for a gang.
 199 class AbstractGangWorker: public WorkerThread {
 200 public:
 201   AbstractGangWorker(AbstractWorkGang* gang, uint id);
 202 
 203   // The only real method: run a task for the gang.
 204   virtual void run();
 205   // Predicate for Thread
 206   virtual bool is_GC_task_thread() const;
 207   virtual bool is_ConcurrentGC_thread() const;
 208   // Printing
 209   void print_on(outputStream* st) const;
 210   virtual void print() const { print_on(tty); }
 211 
 212 protected:
 213   AbstractWorkGang* _gang;
 214 
 215   virtual void initialize();
 216   virtual void loop() = 0;
 217 
 218   AbstractWorkGang* gang() const { return _gang; }
 219 };
 220 
 221 class GangWorker: public AbstractGangWorker {
 222 public:
 223   GangWorker(WorkGang* gang, uint id) : AbstractGangWorker(gang, id) {}
 224 
 225 protected:
 226   virtual void loop();
 227 
 228 private:
 229   WorkData wait_for_task();
 230   void run_task(WorkData work);
 231   void signal_task_done();
 232 
 233   void print_task_started(WorkData data);
 234   void print_task_done(WorkData data);
 235 
 236   WorkGang* gang() const { return (WorkGang*)_gang; }
 237 };
 238 
 239 // A class that acts as a synchronisation barrier. Workers enter
 240 // the barrier and must wait until all other workers have entered
 241 // before any of them may leave.
 242 
 243 class WorkGangBarrierSync : public StackObj {
 244 protected:
 245   Monitor _monitor;
 246   uint    _n_workers;
 247   uint    _n_completed;
 248   bool    _should_reset;
 249   bool    _aborted;
 250 
 251   Monitor* monitor()        { return &_monitor; }
 252   uint     n_workers()      { return _n_workers; }
 253   uint     n_completed()    { return _n_completed; }
 254   bool     should_reset()   { return _should_reset; }
 255   bool     aborted()        { return _aborted; }
 256 
 257   void     zero_completed() { _n_completed = 0; }
 258   void     inc_completed()  { _n_completed++; }
 259   void     set_aborted()    { _aborted = true; }
 260   void     set_should_reset(bool v) { _should_reset = v; }
 261 
 262 public:
 263   WorkGangBarrierSync();
 264   WorkGangBarrierSync(uint n_workers, const char* name);
 265 
 266   // Set the number of workers that will use the barrier.
 267   // Must be called before any of the workers start running.
 268   void set_n_workers(uint n_workers);
 269 
 270   // Enter the barrier. A worker that enters the barrier will
 271   // not be allowed to leave until all other threads have
 272   // also entered the barrier or the barrier is aborted.
 273   // Returns false if the barrier was aborted.
 274   bool enter();
 275 
 276   // Aborts the barrier and wakes up any threads waiting for
 277   // the barrier to complete. The barrier will remain in the
 278   // aborted state until the next call to set_n_workers().
 279   void abort();
 280 };
 281 
 282 // A class to manage claiming of subtasks within a group of tasks.  The
 283 // subtasks will be identified by integer indices, usually elements of an
 284 // enumeration type.
 285 
 286 class SubTasksDone: public CHeapObj<mtInternal> {
 287   uint* _tasks;
 288   uint _n_tasks;
 289   uint _threads_completed;
 290 #ifdef ASSERT
 291   volatile uint _claimed;
 292 #endif
 293 
 294   // Set all tasks to unclaimed.
 295   void clear();
 296 
 297 public:
 298   // Initializes "this" to a state in which there are "n" tasks to be
 299   // processed, none of the which are originally claimed.  The number of
 300   // threads doing the tasks is initialized 1.
 301   SubTasksDone(uint n);
 302 
 303   // True iff the object is in a valid state.
 304   bool valid();
 305 
 306   // Returns "false" if the task "t" is unclaimed, and ensures that task is
 307   // claimed.  The task "t" is required to be within the range of "this".
 308   bool is_task_claimed(uint t);
 309 
 310   // The calling thread asserts that it has attempted to claim all the
 311   // tasks that it will try to claim.  Every thread in the parallel task
 312   // must execute this.  (When the last thread does so, the task array is
 313   // cleared.)
 314   //
 315   // n_threads - Number of threads executing the sub-tasks.
 316   void all_tasks_completed(uint n_threads);
 317 
 318   // Destructor.
 319   ~SubTasksDone();
 320 };
 321 
 322 // As above, but for sequential tasks, i.e. instead of claiming
 323 // sub-tasks from a set (possibly an enumeration), claim sub-tasks
 324 // in sequential order. This is ideal for claiming dynamically
 325 // partitioned tasks (like striding in the parallel remembered
 326 // set scanning). Note that unlike the above class this is
 327 // a stack object - is there any reason for it not to be?
 328 
 329 class SequentialSubTasksDone : public StackObj {
 330 protected:
 331   uint _n_tasks;     // Total number of tasks available.
 332   uint _n_claimed;   // Number of tasks claimed.
 333   // _n_threads is used to determine when a sub task is done.
 334   // See comments on SubTasksDone::_n_threads
 335   uint _n_threads;   // Total number of parallel threads.
 336   uint _n_completed; // Number of completed threads.
 337 
 338   void clear();
 339 
 340 public:
 341   SequentialSubTasksDone() {
 342     clear();
 343   }
 344   ~SequentialSubTasksDone() {}
 345 
 346   // True iff the object is in a valid state.
 347   bool valid();
 348 
 349   // number of tasks
 350   uint n_tasks() const { return _n_tasks; }
 351 
 352   // Get/set the number of parallel threads doing the tasks to t.
 353   // Should be called before the task starts but it is safe
 354   // to call this once a task is running provided that all
 355   // threads agree on the number of threads.
 356   uint n_threads() { return _n_threads; }
 357   void set_n_threads(uint t) { _n_threads = t; }
 358 
 359   // Set the number of tasks to be claimed to t. As above,
 360   // should be called before the tasks start but it is safe
 361   // to call this once a task is running provided all threads
 362   // agree on the number of tasks.
 363   void set_n_tasks(uint t) { _n_tasks = t; }
 364 
 365   // Returns false if the next task in the sequence is unclaimed,
 366   // and ensures that it is claimed. Will set t to be the index
 367   // of the claimed task in the sequence. Will return true if
 368   // the task cannot be claimed and there are none left to claim.
 369   bool is_task_claimed(uint& t);
 370 
 371   // The calling thread asserts that it has attempted to claim
 372   // all the tasks it possibly can in the sequence. Every thread
 373   // claiming tasks must promise call this. Returns true if this
 374   // is the last thread to complete so that the thread can perform
 375   // cleanup if necessary.
 376   bool all_tasks_completed();
 377 };
 378 
 379 // Represents a set of free small integer ids.
 380 class FreeIdSet : public CHeapObj<mtInternal> {
 381   enum {
 382     end_of_list = -1,
 383     claimed = -2
 384   };
 385 
 386   int _sz;
 387   Monitor* _mon;
 388 
 389   int* _ids;
 390   int _hd;
 391   int _waiters;
 392   int _claimed;
 393 
 394   static bool _safepoint;
 395   typedef FreeIdSet* FreeIdSetPtr;
 396   static const int NSets = 10;
 397   static FreeIdSetPtr _sets[NSets];
 398   static bool _stat_init;
 399   int _index;
 400 
 401 public:
 402   FreeIdSet(int sz, Monitor* mon);
 403   ~FreeIdSet();
 404 
 405   static void set_safepoint(bool b);
 406 
 407   // Attempt to claim the given id permanently.  Returns "true" iff
 408   // successful.
 409   bool claim_perm_id(int i);
 410 
 411   // Returns an unclaimed parallel id (waiting for one to be released if
 412   // necessary).  Returns "-1" if a GC wakes up a wait for an id.
 413   int claim_par_id();
 414 
 415   void release_par_id(int id);
 416 };
 417 
 418 #endif // SHARE_VM_GC_SHARED_WORKGROUP_HPP