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  24 
  25 #ifndef SHARE_GC_SHARED_WORKGROUP_HPP
  26 #define SHARE_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 "logging/log.hpp"
  33 #include "utilities/debug.hpp"
  34 #include "utilities/globalDefinitions.hpp"
  35 
  36 // Task class hierarchy:
  37 //   AbstractGangTask
  38 //
  39 // Gang/Group class hierarchy:
  40 //   AbstractWorkGang
  41 //     WorkGang
  42 //     YieldingFlexibleWorkGang (defined in another file)
  43 //
  44 // Worker class hierarchy:
  45 //   AbstractGangWorker (subclass of WorkerThread)
  46 //     GangWorker
  47 //     YieldingFlexibleGangWorker   (defined in another file)
  48 
  49 // Forward declarations of classes defined here
  50 
  51 class AbstractGangWorker;
  52 class Semaphore;
  53 class ThreadClosure;
  54 class WorkGang;
  55 class GangTaskDispatcher;
  56 
  57 // An abstract task to be worked on by a gang.
  58 // You subclass this to supply your own work() method
  59 class AbstractGangTask {
  60   const char* _name;
  61   const uint _gc_id;
  62 
  63  public:
  64   explicit AbstractGangTask(const char* name) :
  65     _name(name),
  66     _gc_id(GCId::current_or_undefined())
  67   {}
  68 
  69   // The abstract work method.
  70   // The argument tells you which member of the gang you are.
  71   virtual void work(uint worker_id) = 0;
  72 
  73   // Debugging accessor for the name.
  74   const char* name() const { return _name; }
  75   const uint gc_id() const { return _gc_id; }
  76 };
  77 
  78 struct WorkData {
  79   AbstractGangTask* _task;
  80   uint              _worker_id;
  81   WorkData(AbstractGangTask* task, uint worker_id) : _task(task), _worker_id(worker_id) {}
  82 };
  83 
  84 // The work gang is the collection of workers to execute tasks.
  85 // The number of workers run for a task is "_active_workers"
  86 // while "_total_workers" is the number of available of workers.
  87 class AbstractWorkGang : public CHeapObj<mtInternal> {
  88  protected:
  89   // The array of worker threads for this gang.
  90   AbstractGangWorker** _workers;
  91   // The count of the number of workers in the gang.
  92   uint _total_workers;
  93   // The currently active workers in this gang.
  94   uint _active_workers;
  95   // The count of created workers in the gang.
  96   uint _created_workers;
  97   // Printing support.
  98   const char* _name;
  99 
 100   ~AbstractWorkGang() {}
 101 
 102  private:
 103   // Initialize only instance data.
 104   const bool _are_GC_task_threads;
 105   const bool _are_ConcurrentGC_threads;
 106 
 107   void set_thread(uint worker_id, AbstractGangWorker* worker) {
 108     _workers[worker_id] = worker;
 109   }
 110 
 111  public:
 112   AbstractWorkGang(const char* name, uint workers, bool are_GC_task_threads, bool are_ConcurrentGC_threads) :
 113       _workers(NULL),
 114       _total_workers(workers),
 115       _active_workers(UseDynamicNumberOfGCThreads ? 1U : workers),
 116       _created_workers(0),
 117       _name(name),
 118       _are_GC_task_threads(are_GC_task_threads),
 119       _are_ConcurrentGC_threads(are_ConcurrentGC_threads)
 120   { }
 121 
 122   // Initialize workers in the gang.  Return true if initialization succeeded.
 123   void initialize_workers();
 124 
 125   bool are_GC_task_threads()      const { return _are_GC_task_threads; }
 126   bool are_ConcurrentGC_threads() const { return _are_ConcurrentGC_threads; }
 127 
 128   uint total_workers() const { return _total_workers; }
 129 
 130   uint created_workers() const {
 131     return _created_workers;
 132   }
 133 
 134   virtual uint active_workers() const {
 135     assert(_active_workers <= _total_workers,
 136            "_active_workers: %u > _total_workers: %u", _active_workers, _total_workers);
 137     return _active_workers;
 138   }
 139 
 140   uint update_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     add_workers(false /* exit_on_failure */);
 145     assert(v != 0, "Trying to set active workers to 0");
 146     log_trace(gc, task)("%s: using %d out of %d workers", name(), _active_workers, _total_workers);
 147     return _active_workers;
 148   }
 149 
 150   // Add GC workers as needed.
 151   void add_workers(bool initializing);
 152 
 153   // Add GC workers as needed to reach the specified number of workers.
 154   void add_workers(uint active_workers, bool initializing);
 155 
 156   // Return the Ith worker.
 157   AbstractGangWorker* worker(uint i) const;
 158 
 159   // Base name (without worker id #) of threads.
 160   const char* group_name() { return name(); }
 161 
 162   void threads_do(ThreadClosure* tc) const;
 163 
 164   // Create a GC worker and install it into the work gang.
 165   virtual AbstractGangWorker* install_worker(uint which);
 166 
 167   // Debugging.
 168   const char* name() const { return _name; }
 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   GangTaskDispatcher* const _dispatcher;
 180   GangTaskDispatcher* dispatcher() const {
 181     return _dispatcher;
 182   }
 183 
 184 public:
 185   WorkGang(const char* name,
 186            uint workers,
 187            bool are_GC_task_threads,
 188            bool are_ConcurrentGC_threads);
 189 
 190   ~WorkGang();
 191 
 192   // Run a task using the current active number of workers, returns when the task is done.
 193   virtual void run_task(AbstractGangTask* task);
 194   // Run a task with the given number of workers, returns
 195   // when the task is done. The number of workers must be at most the number of
 196   // active workers.  Additional workers may be created if an insufficient
 197   // number currently exists. If the add_foreground_work flag is true, the current thread
 198   // is used to run the task too.
 199   void run_task(AbstractGangTask* task, uint num_workers, bool add_foreground_work = false);
 200 
 201 protected:
 202   virtual AbstractGangWorker* allocate_worker(uint which);
 203 };
 204 
 205 // Temporarily try to set the number of active workers.
 206 // It's not guaranteed that it succeeds, and users need to
 207 // query the number of active workers.
 208 class WithUpdatedActiveWorkers : public StackObj {
 209 private:
 210   AbstractWorkGang* const _gang;
 211   const uint              _old_active_workers;
 212 
 213 public:
 214   WithUpdatedActiveWorkers(AbstractWorkGang* gang, uint requested_num_workers) :
 215       _gang(gang),
 216       _old_active_workers(gang->active_workers()) {
 217     uint capped_num_workers = MIN2(requested_num_workers, gang->total_workers());
 218     gang->update_active_workers(capped_num_workers);
 219   }
 220 
 221   ~WithUpdatedActiveWorkers() {
 222     _gang->update_active_workers(_old_active_workers);
 223   }
 224 };
 225 
 226 // Several instances of this class run in parallel as workers for a gang.
 227 class AbstractGangWorker: public WorkerThread {
 228 public:
 229   AbstractGangWorker(AbstractWorkGang* gang, uint id);
 230 
 231   // The only real method: run a task for the gang.
 232   virtual void run();
 233   // Predicate for Thread
 234   virtual bool is_GC_task_thread() const;
 235   virtual bool is_ConcurrentGC_thread() const;
 236   // Printing
 237   void print_on(outputStream* st) const;
 238   virtual void print() const;
 239 
 240 protected:
 241   AbstractWorkGang* _gang;
 242 
 243   virtual void initialize();
 244   virtual void loop() = 0;
 245 
 246   AbstractWorkGang* gang() const { return _gang; }
 247 };
 248 
 249 class GangWorker: public AbstractGangWorker {
 250 public:
 251   GangWorker(WorkGang* gang, uint id) : AbstractGangWorker(gang, id) {}
 252 
 253 protected:
 254   virtual void loop();
 255 
 256 private:
 257   WorkData wait_for_task();
 258   void run_task(WorkData work);
 259   void signal_task_done();
 260 
 261   WorkGang* gang() const { return (WorkGang*)_gang; }
 262 };
 263 
 264 // A class that acts as a synchronisation barrier. Workers enter
 265 // the barrier and must wait until all other workers have entered
 266 // before any of them may leave.
 267 
 268 class WorkGangBarrierSync : public StackObj {
 269 protected:
 270   Monitor _monitor;
 271   uint    _n_workers;
 272   uint    _n_completed;
 273   bool    _should_reset;
 274   bool    _aborted;
 275 
 276   Monitor* monitor()        { return &_monitor; }
 277   uint     n_workers()      { return _n_workers; }
 278   uint     n_completed()    { return _n_completed; }
 279   bool     should_reset()   { return _should_reset; }
 280   bool     aborted()        { return _aborted; }
 281 
 282   void     zero_completed() { _n_completed = 0; }
 283   void     inc_completed()  { _n_completed++; }
 284   void     set_aborted()    { _aborted = true; }
 285   void     set_should_reset(bool v) { _should_reset = v; }
 286 
 287 public:
 288   WorkGangBarrierSync();
 289   WorkGangBarrierSync(uint n_workers, const char* name);
 290 
 291   // Set the number of workers that will use the barrier.
 292   // Must be called before any of the workers start running.
 293   void set_n_workers(uint n_workers);
 294 
 295   // Enter the barrier. A worker that enters the barrier will
 296   // not be allowed to leave until all other threads have
 297   // also entered the barrier or the barrier is aborted.
 298   // Returns false if the barrier was aborted.
 299   bool enter();
 300 
 301   // Aborts the barrier and wakes up any threads waiting for
 302   // the barrier to complete. The barrier will remain in the
 303   // aborted state until the next call to set_n_workers().
 304   void abort();
 305 };
 306 
 307 // A class to manage claiming of subtasks within a group of tasks.  The
 308 // subtasks will be identified by integer indices, usually elements of an
 309 // enumeration type.
 310 
 311 class SubTasksDone: public CHeapObj<mtInternal> {
 312   volatile uint* _tasks;
 313   uint _n_tasks;
 314   volatile uint _threads_completed;
 315 #ifdef ASSERT
 316   volatile uint _claimed;
 317 #endif
 318 
 319   // Set all tasks to unclaimed.
 320   void clear();
 321 
 322   NONCOPYABLE(SubTasksDone);
 323 
 324 public:
 325   // Initializes "this" to a state in which there are "n" tasks to be
 326   // processed, none of the which are originally claimed.  The number of
 327   // threads doing the tasks is initialized 1.
 328   SubTasksDone(uint n);
 329 
 330   // True iff the object is in a valid state.
 331   bool valid();
 332 
 333   // Attempt to claim the task "t", returning true if successful,
 334   // false if it has already been claimed.  The task "t" is required
 335   // to be within the range of "this".
 336   bool try_claim_task(uint t);
 337 
 338   // The calling thread asserts that it has attempted to claim all the
 339   // tasks that it will try to claim.  Every thread in the parallel task
 340   // must execute this.  (When the last thread does so, the task array is
 341   // cleared.)
 342   //
 343   // n_threads - Number of threads executing the sub-tasks.
 344   void all_tasks_completed(uint n_threads);
 345 
 346   // Destructor.
 347   ~SubTasksDone();
 348 };
 349 
 350 // As above, but for sequential tasks, i.e. instead of claiming
 351 // sub-tasks from a set (possibly an enumeration), claim sub-tasks
 352 // in sequential order. This is ideal for claiming dynamically
 353 // partitioned tasks (like striding in the parallel remembered
 354 // set scanning). Note that unlike the above class this is
 355 // a stack object - is there any reason for it not to be?
 356 
 357 class SequentialSubTasksDone : public StackObj {
 358 protected:
 359   uint _n_tasks;     // Total number of tasks available.
 360   volatile uint _n_claimed;   // Number of tasks claimed.
 361   // _n_threads is used to determine when a sub task is done.
 362   // See comments on SubTasksDone::_n_threads
 363   uint _n_threads;   // Total number of parallel threads.
 364   volatile uint _n_completed; // Number of completed threads.
 365 
 366   void clear();
 367 
 368 public:
 369   SequentialSubTasksDone() {
 370     clear();
 371   }
 372   ~SequentialSubTasksDone() {}
 373 
 374   // True iff the object is in a valid state.
 375   bool valid();
 376 
 377   // number of tasks
 378   uint n_tasks() const { return _n_tasks; }
 379 
 380   // Get/set the number of parallel threads doing the tasks to t.
 381   // Should be called before the task starts but it is safe
 382   // to call this once a task is running provided that all
 383   // threads agree on the number of threads.
 384   uint n_threads() { return _n_threads; }
 385   void set_n_threads(uint t) { _n_threads = t; }
 386 
 387   // Set the number of tasks to be claimed to t. As above,
 388   // should be called before the tasks start but it is safe
 389   // to call this once a task is running provided all threads
 390   // agree on the number of tasks.
 391   void set_n_tasks(uint t) { _n_tasks = t; }
 392 
 393   // Attempt to claim the next unclaimed task in the sequence,
 394   // returning true if successful, with t set to the index of the
 395   // claimed task.  Returns false if there are no more unclaimed tasks
 396   // in the sequence.
 397   bool try_claim_task(uint& t);
 398 
 399   // The calling thread asserts that it has attempted to claim
 400   // all the tasks it possibly can in the sequence. Every thread
 401   // claiming tasks must promise call this. Returns true if this
 402   // is the last thread to complete so that the thread can perform
 403   // cleanup if necessary.
 404   bool all_tasks_completed();
 405 };
 406 
 407 #endif // SHARE_GC_SHARED_WORKGROUP_HPP
--- EOF ---