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 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 ~AbstractWorkGang() {} 126 127 private: 128 // Initialize only instance data. 129 const bool _are_GC_task_threads; 130 const bool _are_ConcurrentGC_threads; 131 132 void set_thread(uint worker_id, AbstractGangWorker* worker) { 133 _workers[worker_id] = worker; 134 } 135 136 public: 137 AbstractWorkGang(const char* name, uint workers, bool are_GC_task_threads, bool are_ConcurrentGC_threads) : 138 _name(name), 139 _total_workers(workers), 140 _active_workers(UseDynamicNumberOfGCThreads ? 1U : workers), 141 _created_workers(0), 142 _are_GC_task_threads(are_GC_task_threads), 143 _are_ConcurrentGC_threads(are_ConcurrentGC_threads) 144 { } 145 146 // Initialize workers in the gang. Return true if initialization succeeded. 147 void initialize_workers(); 148 149 bool are_GC_task_threads() const { return _are_GC_task_threads; } 150 bool are_ConcurrentGC_threads() const { return _are_ConcurrentGC_threads; } 151 152 uint total_workers() const { return _total_workers; } 153 154 uint created_workers() const { 155 return _created_workers; 156 } 157 158 virtual uint active_workers() const { 159 assert(_active_workers <= _total_workers, 160 "_active_workers: %u > _total_workers: %u", _active_workers, _total_workers); 161 assert(UseDynamicNumberOfGCThreads || _active_workers == _total_workers, 162 "Unless dynamic should use total workers"); 163 return _active_workers; 164 } 165 166 uint update_active_workers(uint v) { 167 assert(v <= _total_workers, 168 "Trying to set more workers active than there are"); 169 _active_workers = MIN2(v, _total_workers); 170 add_workers(false /* exit_on_failure */); 171 assert(v != 0, "Trying to set active workers to 0"); 172 log_trace(gc, task)("%s: using %d out of %d workers", name(), _active_workers, _total_workers); 173 return _active_workers; 174 } 175 176 // Add GC workers as needed. 177 void add_workers(bool initializing); 178 179 // Add GC workers as needed to reach the specified number of workers. 180 void add_workers(uint active_workers, bool initializing); 181 182 // Return the Ith worker. 183 AbstractGangWorker* worker(uint i) const; 184 185 // Base name (without worker id #) of threads. 186 const char* group_name() { return name(); } 187 188 void threads_do(ThreadClosure* tc) const; 189 190 // Create a GC worker and install it into the work gang. 191 virtual AbstractGangWorker* install_worker(uint which); 192 193 // Debugging. 194 const char* name() const { return _name; } 195 196 // Printing 197 void print_worker_threads_on(outputStream *st) const; 198 void print_worker_threads() const { 199 print_worker_threads_on(tty); 200 } 201 202 protected: 203 virtual AbstractGangWorker* allocate_worker(uint which) = 0; 204 }; 205 206 // An class representing a gang of workers. 207 class WorkGang: public AbstractWorkGang { 208 // To get access to the GangTaskDispatcher instance. 209 friend class GangWorker; 210 211 GangTaskDispatcher* const _dispatcher; 212 GangTaskDispatcher* dispatcher() const { 213 return _dispatcher; 214 } 215 216 public: 217 WorkGang(const char* name, 218 uint workers, 219 bool are_GC_task_threads, 220 bool are_ConcurrentGC_threads); 221 222 ~WorkGang(); 223 224 // Run a task using the current active number of workers, returns when the task is done. 225 virtual void run_task(AbstractGangTask* task); 226 // Run a task with the given number of workers, returns 227 // when the task is done. The number of workers must be at most the number of 228 // active workers. Additional workers may be created if an insufficient 229 // number currently exists. 230 void run_task(AbstractGangTask* task, uint num_workers); 231 232 protected: 233 virtual AbstractGangWorker* allocate_worker(uint which); 234 }; 235 236 // Several instances of this class run in parallel as workers for a gang. 237 class AbstractGangWorker: public WorkerThread { 238 public: 239 AbstractGangWorker(AbstractWorkGang* gang, uint id); 240 241 // The only real method: run a task for the gang. 242 virtual void run(); 243 // Predicate for Thread 244 virtual bool is_GC_task_thread() const; 245 virtual bool is_ConcurrentGC_thread() const; 246 // Printing 247 void print_on(outputStream* st) const; 248 virtual void print() const { print_on(tty); } 249 250 protected: 251 AbstractWorkGang* _gang; 252 253 virtual void initialize(); 254 virtual void loop() = 0; 255 256 AbstractWorkGang* gang() const { return _gang; } 257 }; 258 259 class GangWorker: public AbstractGangWorker { 260 public: 261 GangWorker(WorkGang* gang, uint id) : AbstractGangWorker(gang, id) {} 262 263 protected: 264 virtual void loop(); 265 266 private: 267 WorkData wait_for_task(); 268 void run_task(WorkData work); 269 void signal_task_done(); 270 271 WorkGang* gang() const { return (WorkGang*)_gang; } 272 }; 273 274 // A class that acts as a synchronisation barrier. Workers enter 275 // the barrier and must wait until all other workers have entered 276 // before any of them may leave. 277 278 class WorkGangBarrierSync : public StackObj { 279 protected: 280 Monitor _monitor; 281 uint _n_workers; 282 uint _n_completed; 283 bool _should_reset; 284 bool _aborted; 285 286 Monitor* monitor() { return &_monitor; } 287 uint n_workers() { return _n_workers; } 288 uint n_completed() { return _n_completed; } 289 bool should_reset() { return _should_reset; } 290 bool aborted() { return _aborted; } 291 292 void zero_completed() { _n_completed = 0; } 293 void inc_completed() { _n_completed++; } 294 void set_aborted() { _aborted = true; } 295 void set_should_reset(bool v) { _should_reset = v; } 296 297 public: 298 WorkGangBarrierSync(); 299 WorkGangBarrierSync(uint n_workers, const char* name); 300 301 // Set the number of workers that will use the barrier. 302 // Must be called before any of the workers start running. 303 void set_n_workers(uint n_workers); 304 305 // Enter the barrier. A worker that enters the barrier will 306 // not be allowed to leave until all other threads have 307 // also entered the barrier or the barrier is aborted. 308 // Returns false if the barrier was aborted. 309 bool enter(); 310 311 // Aborts the barrier and wakes up any threads waiting for 312 // the barrier to complete. The barrier will remain in the 313 // aborted state until the next call to set_n_workers(). 314 void abort(); 315 }; 316 317 // A class to manage claiming of subtasks within a group of tasks. The 318 // subtasks will be identified by integer indices, usually elements of an 319 // enumeration type. 320 321 class SubTasksDone: public CHeapObj<mtInternal> { 322 volatile uint* _tasks; 323 uint _n_tasks; 324 volatile uint _threads_completed; 325 #ifdef ASSERT 326 volatile uint _claimed; 327 #endif 328 329 // Set all tasks to unclaimed. 330 void clear(); 331 332 public: 333 // Initializes "this" to a state in which there are "n" tasks to be 334 // processed, none of the which are originally claimed. The number of 335 // threads doing the tasks is initialized 1. 336 SubTasksDone(uint n); 337 338 // True iff the object is in a valid state. 339 bool valid(); 340 341 // Returns "false" if the task "t" is unclaimed, and ensures that task is 342 // claimed. The task "t" is required to be within the range of "this". 343 bool is_task_claimed(uint t); 344 345 // The calling thread asserts that it has attempted to claim all the 346 // tasks that it will try to claim. Every thread in the parallel task 347 // must execute this. (When the last thread does so, the task array is 348 // cleared.) 349 // 350 // n_threads - Number of threads executing the sub-tasks. 351 void all_tasks_completed(uint n_threads); 352 353 // Destructor. 354 ~SubTasksDone(); 355 }; 356 357 // As above, but for sequential tasks, i.e. instead of claiming 358 // sub-tasks from a set (possibly an enumeration), claim sub-tasks 359 // in sequential order. This is ideal for claiming dynamically 360 // partitioned tasks (like striding in the parallel remembered 361 // set scanning). Note that unlike the above class this is 362 // a stack object - is there any reason for it not to be? 363 364 class SequentialSubTasksDone : public StackObj { 365 protected: 366 uint _n_tasks; // Total number of tasks available. 367 volatile uint _n_claimed; // Number of tasks claimed. 368 // _n_threads is used to determine when a sub task is done. 369 // See comments on SubTasksDone::_n_threads 370 uint _n_threads; // Total number of parallel threads. 371 volatile uint _n_completed; // Number of completed threads. 372 373 void clear(); 374 375 public: 376 SequentialSubTasksDone() { 377 clear(); 378 } 379 ~SequentialSubTasksDone() {} 380 381 // True iff the object is in a valid state. 382 bool valid(); 383 384 // number of tasks 385 uint n_tasks() const { return _n_tasks; } 386 387 // Get/set the number of parallel threads doing the tasks to t. 388 // Should be called before the task starts but it is safe 389 // to call this once a task is running provided that all 390 // threads agree on the number of threads. 391 uint n_threads() { return _n_threads; } 392 void set_n_threads(uint t) { _n_threads = t; } 393 394 // Set the number of tasks to be claimed to t. As above, 395 // should be called before the tasks start but it is safe 396 // to call this once a task is running provided all threads 397 // agree on the number of tasks. 398 void set_n_tasks(uint t) { _n_tasks = t; } 399 400 // Returns false if the next task in the sequence is unclaimed, 401 // and ensures that it is claimed. Will set t to be the index 402 // of the claimed task in the sequence. Will return true if 403 // the task cannot be claimed and there are none left to claim. 404 bool is_task_claimed(uint& t); 405 406 // The calling thread asserts that it has attempted to claim 407 // all the tasks it possibly can in the sequence. Every thread 408 // claiming tasks must promise call this. Returns true if this 409 // is the last thread to complete so that the thread can perform 410 // cleanup if necessary. 411 bool all_tasks_completed(); 412 }; 413 414 #endif // SHARE_VM_GC_SHARED_WORKGROUP_HPP