1 /*
   2  * Copyright (c) 2002, 2015, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  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).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  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   // The abstract work method.
  68   // The argument tells you which member of the gang you are.
  69   virtual void work(uint worker_id) = 0;
  70 
  71   // Debugging accessor for the name.
  72   const char* name() const { return _name; }
  73   const uint gc_id() const { return _gc_id; }
  74 };
  75 
  76 struct WorkData {
  77   AbstractGangTask* _task;
  78   uint              _worker_id;
  79   WorkData(AbstractGangTask* task, uint worker_id) : _task(task), _worker_id(worker_id) {}
  80 };
  81 
  82 // Interface to handle the synchronization between the coordinator thread and the worker threads,
  83 // when a task is dispatched out to the worker threads.
  84 class GangTaskDispatcher : public CHeapObj<mtGC> {
  85  public:
  86   virtual ~GangTaskDispatcher() {}
  87 
  88   // Coordinator API.
  89 
  90   // Distributes the task out to num_workers workers.
  91   // Returns when the task has been completed by all workers.
  92   virtual void coordinator_execute_on_workers(AbstractGangTask* task, uint num_workers) = 0;
  93 
  94   // Worker API.
  95 
  96   // Waits for a task to become available to the worker.
  97   // Returns when the worker has been assigned a task.
  98   virtual WorkData worker_wait_for_task() = 0;
  99 
 100   // Signal to the coordinator that the worker is done with the assigned task.
 101   virtual void     worker_done_with_task() = 0;
 102 };
 103 
 104 // The work gang is the collection of workers to execute tasks.
 105 // The number of workers run for a task is "_active_workers"
 106 // while "_total_workers" is the number of available of workers.
 107 class AbstractWorkGang : public CHeapObj<mtInternal> {
 108  protected:
 109   // The array of worker threads for this gang.
 110   AbstractGangWorker** _workers;
 111   // The count of the number of workers in the gang.
 112   uint _total_workers;
 113   // The currently active workers in this gang.
 114   uint _active_workers;
 115   // Printing support.
 116   const char* _name;
 117 
 118  private:
 119   // Initialize only instance data.
 120   const bool _are_GC_task_threads;
 121   const bool _are_ConcurrentGC_threads;
 122 
 123  public:
 124   AbstractWorkGang(const char* name, uint workers, bool are_GC_task_threads, bool are_ConcurrentGC_threads) :
 125       _name(name),
 126       _total_workers(workers),
 127       _active_workers(UseDynamicNumberOfGCThreads ? 1U : workers),
 128       _are_GC_task_threads(are_GC_task_threads),
 129       _are_ConcurrentGC_threads(are_ConcurrentGC_threads)
 130   { }
 131 
 132   // Initialize workers in the gang.  Return true if initialization succeeded.
 133   bool initialize_workers();
 134 
 135   bool are_GC_task_threads()      const { return _are_GC_task_threads; }
 136   bool are_ConcurrentGC_threads() const { return _are_ConcurrentGC_threads; }
 137 
 138   uint total_workers() const { return _total_workers; }
 139 
 140   virtual uint active_workers() const {
 141     assert(_active_workers <= _total_workers,
 142            "_active_workers: %u > _total_workers: %u", _active_workers, _total_workers);
 143     assert(UseDynamicNumberOfGCThreads || _active_workers == _total_workers,
 144            "Unless dynamic should use total workers");
 145     return _active_workers;
 146   }
 147   void set_active_workers(uint v) {
 148     assert(v <= _total_workers,
 149            "Trying to set more workers active than there are");
 150     _active_workers = MIN2(v, _total_workers);
 151     assert(v != 0, "Trying to set active workers to 0");
 152     _active_workers = MAX2(1U, _active_workers);
 153     assert(UseDynamicNumberOfGCThreads || _active_workers == _total_workers,
 154            "Unless dynamic should use total workers");
 155     log_info(gc, task)("GC Workers: %d", _active_workers);
 156   }
 157 
 158   // Return the Ith worker.
 159   AbstractGangWorker* worker(uint i) const;
 160 
 161   void threads_do(ThreadClosure* tc) const;
 162 
 163   // Debugging.
 164   const char* name() const { return _name; }
 165 
 166   // Printing
 167   void print_worker_threads_on(outputStream *st) const;
 168   void print_worker_threads() const {
 169     print_worker_threads_on(tty);
 170   }
 171 
 172  protected:
 173   virtual AbstractGangWorker* allocate_worker(uint which) = 0;
 174 };
 175 
 176 // An class representing a gang of workers.
 177 class WorkGang: public AbstractWorkGang {
 178   // To get access to the GangTaskDispatcher instance.
 179   friend class GangWorker;
 180 
 181   // Never deleted.
 182   ~WorkGang();
 183 
 184   GangTaskDispatcher* const _dispatcher;
 185   GangTaskDispatcher* dispatcher() const {
 186     return _dispatcher;
 187   }
 188 
 189 public:
 190   WorkGang(const char* name,
 191            uint workers,
 192            bool are_GC_task_threads,
 193            bool are_ConcurrentGC_threads);
 194 
 195   // Run a task, returns when the task is done.
 196   virtual void run_task(AbstractGangTask* task);
 197 
 198 protected:
 199   virtual AbstractGangWorker* allocate_worker(uint which);
 200 };
 201 
 202 // Several instances of this class run in parallel as workers for a gang.
 203 class AbstractGangWorker: public WorkerThread {
 204 public:
 205   AbstractGangWorker(AbstractWorkGang* gang, uint id);
 206 
 207   // The only real method: run a task for the gang.
 208   virtual void run();
 209   // Predicate for Thread
 210   virtual bool is_GC_task_thread() const;
 211   virtual bool is_ConcurrentGC_thread() const;
 212   // Printing
 213   void print_on(outputStream* st) const;
 214   virtual void print() const { print_on(tty); }
 215 
 216 protected:
 217   AbstractWorkGang* _gang;
 218 
 219   virtual void initialize();
 220   virtual void loop() = 0;
 221 
 222   AbstractWorkGang* gang() const { return _gang; }
 223 };
 224 
 225 class GangWorker: public AbstractGangWorker {
 226 public:
 227   GangWorker(WorkGang* gang, uint id) : AbstractGangWorker(gang, id) {}
 228 
 229 protected:
 230   virtual void loop();
 231 
 232 private:
 233   WorkData wait_for_task();
 234   void run_task(WorkData work);
 235   void signal_task_done();
 236 
 237   void print_task_started(WorkData data);
 238   void print_task_done(WorkData data);
 239 
 240   WorkGang* gang() const { return (WorkGang*)_gang; }
 241 };
 242 
 243 // A class that acts as a synchronisation barrier. Workers enter
 244 // the barrier and must wait until all other workers have entered
 245 // before any of them may leave.
 246 
 247 class WorkGangBarrierSync : public StackObj {
 248 protected:
 249   Monitor _monitor;
 250   uint    _n_workers;
 251   uint    _n_completed;
 252   bool    _should_reset;
 253   bool    _aborted;
 254 
 255   Monitor* monitor()        { return &_monitor; }
 256   uint     n_workers()      { return _n_workers; }
 257   uint     n_completed()    { return _n_completed; }
 258   bool     should_reset()   { return _should_reset; }
 259   bool     aborted()        { return _aborted; }
 260 
 261   void     zero_completed() { _n_completed = 0; }
 262   void     inc_completed()  { _n_completed++; }
 263   void     set_aborted()    { _aborted = true; }
 264   void     set_should_reset(bool v) { _should_reset = v; }
 265 
 266 public:
 267   WorkGangBarrierSync();
 268   WorkGangBarrierSync(uint n_workers, const char* name);
 269 
 270   // Set the number of workers that will use the barrier.
 271   // Must be called before any of the workers start running.
 272   void set_n_workers(uint n_workers);
 273 
 274   // Enter the barrier. A worker that enters the barrier will
 275   // not be allowed to leave until all other threads have
 276   // also entered the barrier or the barrier is aborted.
 277   // Returns false if the barrier was aborted.
 278   bool enter();
 279 
 280   // Aborts the barrier and wakes up any threads waiting for
 281   // the barrier to complete. The barrier will remain in the
 282   // aborted state until the next call to set_n_workers().
 283   void abort();
 284 };
 285 
 286 // A class to manage claiming of subtasks within a group of tasks.  The
 287 // subtasks will be identified by integer indices, usually elements of an
 288 // enumeration type.
 289 
 290 class SubTasksDone: public CHeapObj<mtInternal> {
 291   uint* _tasks;
 292   uint _n_tasks;
 293   uint _threads_completed;
 294 #ifdef ASSERT
 295   volatile uint _claimed;
 296 #endif
 297 
 298   // Set all tasks to unclaimed.
 299   void clear();
 300 
 301 public:
 302   // Initializes "this" to a state in which there are "n" tasks to be
 303   // processed, none of the which are originally claimed.  The number of
 304   // threads doing the tasks is initialized 1.
 305   SubTasksDone(uint n);
 306 
 307   // True iff the object is in a valid state.
 308   bool valid();
 309 
 310   // Returns "false" if the task "t" is unclaimed, and ensures that task is
 311   // claimed.  The task "t" is required to be within the range of "this".
 312   bool is_task_claimed(uint t);
 313 
 314   // The calling thread asserts that it has attempted to claim all the
 315   // tasks that it will try to claim.  Every thread in the parallel task
 316   // must execute this.  (When the last thread does so, the task array is
 317   // cleared.)
 318   //
 319   // n_threads - Number of threads executing the sub-tasks.
 320   void all_tasks_completed(uint n_threads);
 321 
 322   // Destructor.
 323   ~SubTasksDone();
 324 };
 325 
 326 // As above, but for sequential tasks, i.e. instead of claiming
 327 // sub-tasks from a set (possibly an enumeration), claim sub-tasks
 328 // in sequential order. This is ideal for claiming dynamically
 329 // partitioned tasks (like striding in the parallel remembered
 330 // set scanning). Note that unlike the above class this is
 331 // a stack object - is there any reason for it not to be?
 332 
 333 class SequentialSubTasksDone : public StackObj {
 334 protected:
 335   uint _n_tasks;     // Total number of tasks available.
 336   uint _n_claimed;   // Number of tasks claimed.
 337   // _n_threads is used to determine when a sub task is done.
 338   // See comments on SubTasksDone::_n_threads
 339   uint _n_threads;   // Total number of parallel threads.
 340   uint _n_completed; // Number of completed threads.
 341 
 342   void clear();
 343 
 344 public:
 345   SequentialSubTasksDone() {
 346     clear();
 347   }
 348   ~SequentialSubTasksDone() {}
 349 
 350   // True iff the object is in a valid state.
 351   bool valid();
 352 
 353   // number of tasks
 354   uint n_tasks() const { return _n_tasks; }
 355 
 356   // Get/set the number of parallel threads doing the tasks to t.
 357   // Should be called before the task starts but it is safe
 358   // to call this once a task is running provided that all
 359   // threads agree on the number of threads.
 360   uint n_threads() { return _n_threads; }
 361   void set_n_threads(uint t) { _n_threads = t; }
 362 
 363   // Set the number of tasks to be claimed to t. As above,
 364   // should be called before the tasks start but it is safe
 365   // to call this once a task is running provided all threads
 366   // agree on the number of tasks.
 367   void set_n_tasks(uint t) { _n_tasks = t; }
 368 
 369   // Returns false if the next task in the sequence is unclaimed,
 370   // and ensures that it is claimed. Will set t to be the index
 371   // of the claimed task in the sequence. Will return true if
 372   // the task cannot be claimed and there are none left to claim.
 373   bool is_task_claimed(uint& t);
 374 
 375   // The calling thread asserts that it has attempted to claim
 376   // all the tasks it possibly can in the sequence. Every thread
 377   // claiming tasks must promise call this. Returns true if this
 378   // is the last thread to complete so that the thread can perform
 379   // cleanup if necessary.
 380   bool all_tasks_completed();
 381 };
 382 
 383 #endif // SHARE_VM_GC_SHARED_WORKGROUP_HPP