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