1 /* 2 * Copyright (c) 2002, 2016, 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 // The count of created workers in the gang. 116 uint _created_workers; 117 // Printing support. 118 const char* _name; 119 120 private: 121 // Initialize only instance data. 122 const bool _are_GC_task_threads; 123 const bool _are_ConcurrentGC_threads; 124 125 void set_thread(uint worker_id, AbstractGangWorker* worker) { 126 _workers[worker_id] = worker; 127 } 128 129 public: 130 AbstractWorkGang(const char* name, uint workers, bool are_GC_task_threads, bool are_ConcurrentGC_threads) : 131 _name(name), 132 _total_workers(workers), 133 _active_workers(UseDynamicNumberOfGCThreads ? 1U : workers), 134 _created_workers(0), 135 _are_GC_task_threads(are_GC_task_threads), 136 _are_ConcurrentGC_threads(are_ConcurrentGC_threads) 137 { } 138 139 // Initialize workers in the gang. Return true if initialization succeeded. 140 void initialize_workers(); 141 142 bool are_GC_task_threads() const { return _are_GC_task_threads; } 143 bool are_ConcurrentGC_threads() const { return _are_ConcurrentGC_threads; } 144 145 uint total_workers() const { return _total_workers; } 146 147 uint created_workers() const { 148 return _created_workers; 149 } 150 151 virtual uint active_workers() const { 152 assert(_active_workers <= _total_workers, 153 "_active_workers: %u > _total_workers: %u", _active_workers, _total_workers); 154 assert(UseDynamicNumberOfGCThreads || _active_workers == _total_workers, 155 "Unless dynamic should use total workers"); 156 return _active_workers; 157 } 158 159 uint update_active_workers(uint v) { 160 assert(v <= _total_workers, 161 "Trying to set more workers active than there are"); 162 _active_workers = MIN2(v, _total_workers); 163 add_workers(false /* exit_on_failure */); 164 assert(v != 0, "Trying to set active workers to 0"); 165 log_info(gc, task)("GC Workers: using %d out of %d", _active_workers, _total_workers); 166 return _active_workers; 167 } 168 169 // Add GC workers as needed. 170 void add_workers(bool initializing); 171 172 // Add GC workers as needed to reach the specified number of workers. 173 void add_workers(uint active_workers, bool initializing); 174 175 // Return the Ith worker. 176 AbstractGangWorker* worker(uint i) const; 177 178 void threads_do(ThreadClosure* tc) const; 179 180 // Create a GC worker and install it into the work gang. 181 virtual AbstractGangWorker* install_worker(uint which); 182 183 // Debugging. 184 const char* name() const { return _name; } 185 186 // Printing 187 void print_worker_threads_on(outputStream *st) const; 188 void print_worker_threads() const { 189 print_worker_threads_on(tty); 190 } 191 192 protected: 193 virtual AbstractGangWorker* allocate_worker(uint which) = 0; 194 }; 195 196 // An class representing a gang of workers. 197 class WorkGang: public AbstractWorkGang { 198 // To get access to the GangTaskDispatcher instance. 199 friend class GangWorker; 200 201 // Never deleted. 202 ~WorkGang(); 203 204 GangTaskDispatcher* const _dispatcher; 205 GangTaskDispatcher* dispatcher() const { 206 return _dispatcher; 207 } 208 209 public: 210 WorkGang(const char* name, 211 uint workers, 212 bool are_GC_task_threads, 213 bool are_ConcurrentGC_threads); 214 215 // Run a task using the current active number of workers, returns when the task is done. 216 virtual void run_task(AbstractGangTask* task); 217 // Run a task with the given number of workers, returns 218 // when the task is done. The number of workers must be at most the number of 219 // active workers. Additional workers may be created if an insufficient 220 // number currently exists. 221 void run_task(AbstractGangTask* task, uint num_workers); 222 223 protected: 224 virtual AbstractGangWorker* allocate_worker(uint which); 225 }; 226 227 // Several instances of this class run in parallel as workers for a gang. 228 class AbstractGangWorker: public WorkerThread { 229 public: 230 AbstractGangWorker(AbstractWorkGang* gang, uint id); 231 232 // The only real method: run a task for the gang. 233 virtual void run(); 234 // Predicate for Thread 235 virtual bool is_GC_task_thread() const; 236 virtual bool is_ConcurrentGC_thread() const; 237 // Printing 238 void print_on(outputStream* st) const; 239 virtual void print() const { print_on(tty); } 240 241 protected: 242 AbstractWorkGang* _gang; 243 244 virtual void initialize(); 245 virtual void loop() = 0; 246 247 AbstractWorkGang* gang() const { return _gang; } 248 }; 249 250 class GangWorker: public AbstractGangWorker { 251 public: 252 GangWorker(WorkGang* gang, uint id) : AbstractGangWorker(gang, id) {} 253 254 protected: 255 virtual void loop(); 256 257 private: 258 WorkData wait_for_task(); 259 void run_task(WorkData work); 260 void signal_task_done(); 261 262 WorkGang* gang() const { return (WorkGang*)_gang; } 263 }; 264 265 // A class that acts as a synchronisation barrier. Workers enter 266 // the barrier and must wait until all other workers have entered 267 // before any of them may leave. 268 269 class WorkGangBarrierSync : public StackObj { 270 protected: 271 Monitor _monitor; 272 uint _n_workers; 273 uint _n_completed; 274 bool _should_reset; 275 bool _aborted; 276 277 Monitor* monitor() { return &_monitor; } 278 uint n_workers() { return _n_workers; } 279 uint n_completed() { return _n_completed; } 280 bool should_reset() { return _should_reset; } 281 bool aborted() { return _aborted; } 282 283 void zero_completed() { _n_completed = 0; } 284 void inc_completed() { _n_completed++; } 285 void set_aborted() { _aborted = true; } 286 void set_should_reset(bool v) { _should_reset = v; } 287 288 public: 289 WorkGangBarrierSync(); 290 WorkGangBarrierSync(uint n_workers, const char* name); 291 292 // Set the number of workers that will use the barrier. 293 // Must be called before any of the workers start running. 294 void set_n_workers(uint n_workers); 295 296 // Enter the barrier. A worker that enters the barrier will 297 // not be allowed to leave until all other threads have 298 // also entered the barrier or the barrier is aborted. 299 // Returns false if the barrier was aborted. 300 bool enter(); 301 302 // Aborts the barrier and wakes up any threads waiting for 303 // the barrier to complete. The barrier will remain in the 304 // aborted state until the next call to set_n_workers(). 305 void abort(); 306 }; 307 308 // A class to manage claiming of subtasks within a group of tasks. The 309 // subtasks will be identified by integer indices, usually elements of an 310 // enumeration type. 311 312 class SubTasksDone: public CHeapObj<mtInternal> { 313 uint* _tasks; 314 uint _n_tasks; 315 uint _threads_completed; 316 #ifdef ASSERT 317 volatile uint _claimed; 318 #endif 319 320 // Set all tasks to unclaimed. 321 void clear(); 322 323 public: 324 // Initializes "this" to a state in which there are "n" tasks to be 325 // processed, none of the which are originally claimed. The number of 326 // threads doing the tasks is initialized 1. 327 SubTasksDone(uint n); 328 329 // True iff the object is in a valid state. 330 bool valid(); 331 332 // Returns "false" if the task "t" is unclaimed, and ensures that task is 333 // claimed. The task "t" is required to be within the range of "this". 334 bool is_task_claimed(uint t); 335 336 // The calling thread asserts that it has attempted to claim all the 337 // tasks that it will try to claim. Every thread in the parallel task 338 // must execute this. (When the last thread does so, the task array is 339 // cleared.) 340 // 341 // n_threads - Number of threads executing the sub-tasks. 342 void all_tasks_completed(uint n_threads); 343 344 // Destructor. 345 ~SubTasksDone(); 346 }; 347 348 // As above, but for sequential tasks, i.e. instead of claiming 349 // sub-tasks from a set (possibly an enumeration), claim sub-tasks 350 // in sequential order. This is ideal for claiming dynamically 351 // partitioned tasks (like striding in the parallel remembered 352 // set scanning). Note that unlike the above class this is 353 // a stack object - is there any reason for it not to be? 354 355 class SequentialSubTasksDone : public StackObj { 356 protected: 357 uint _n_tasks; // Total number of tasks available. 358 uint _n_claimed; // Number of tasks claimed. 359 // _n_threads is used to determine when a sub task is done. 360 // See comments on SubTasksDone::_n_threads 361 uint _n_threads; // Total number of parallel threads. 362 uint _n_completed; // Number of completed threads. 363 364 void clear(); 365 366 public: 367 SequentialSubTasksDone() { 368 clear(); 369 } 370 ~SequentialSubTasksDone() {} 371 372 // True iff the object is in a valid state. 373 bool valid(); 374 375 // number of tasks 376 uint n_tasks() const { return _n_tasks; } 377 378 // Get/set the number of parallel threads doing the tasks to t. 379 // Should be called before the task starts but it is safe 380 // to call this once a task is running provided that all 381 // threads agree on the number of threads. 382 uint n_threads() { return _n_threads; } 383 void set_n_threads(uint t) { _n_threads = t; } 384 385 // Set the number of tasks to be claimed to t. As above, 386 // should be called before the tasks start but it is safe 387 // to call this once a task is running provided all threads 388 // agree on the number of tasks. 389 void set_n_tasks(uint t) { _n_tasks = t; } 390 391 // Returns false if the next task in the sequence is unclaimed, 392 // and ensures that it is claimed. Will set t to be the index 393 // of the claimed task in the sequence. Will return true if 394 // the task cannot be claimed and there are none left to claim. 395 bool is_task_claimed(uint& t); 396 397 // The calling thread asserts that it has attempted to claim 398 // all the tasks it possibly can in the sequence. Every thread 399 // claiming tasks must promise call this. Returns true if this 400 // is the last thread to complete so that the thread can perform 401 // cleanup if necessary. 402 bool all_tasks_completed(); 403 }; 404 405 #endif // SHARE_VM_GC_SHARED_WORKGROUP_HPP