1 /* 2 * Copyright (c) 2002, 2018, 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 explicit AbstractGangTask(const char* name) : 63 _name(name), 64 _gc_id(GCId::current_or_undefined()) 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 ~AbstractWorkGang() {} 121 122 private: 123 // Initialize only instance data. 124 const bool _are_GC_task_threads; 125 const bool _are_ConcurrentGC_threads; 126 127 void set_thread(uint worker_id, AbstractGangWorker* worker) { 128 _workers[worker_id] = worker; 129 } 130 131 public: 132 AbstractWorkGang(const char* name, uint workers, bool are_GC_task_threads, bool are_ConcurrentGC_threads) : 133 _name(name), 134 _total_workers(workers), 135 _active_workers(UseDynamicNumberOfGCThreads ? 1U : workers), 136 _created_workers(0), 137 _are_GC_task_threads(are_GC_task_threads), 138 _are_ConcurrentGC_threads(are_ConcurrentGC_threads) 139 { } 140 141 // Initialize workers in the gang. Return true if initialization succeeded. 142 void initialize_workers(); 143 144 bool are_GC_task_threads() const { return _are_GC_task_threads; } 145 bool are_ConcurrentGC_threads() const { return _are_ConcurrentGC_threads; } 146 147 uint total_workers() const { return _total_workers; } 148 149 uint created_workers() const { 150 return _created_workers; 151 } 152 153 virtual uint active_workers() const { 154 assert(_active_workers <= _total_workers, 155 "_active_workers: %u > _total_workers: %u", _active_workers, _total_workers); 156 assert(UseDynamicNumberOfGCThreads || _active_workers == _total_workers, 157 "Unless dynamic should use total workers"); 158 return _active_workers; 159 } 160 161 uint update_active_workers(uint v) { 162 assert(v <= _total_workers, 163 "Trying to set more workers active than there are"); 164 _active_workers = MIN2(v, _total_workers); 165 add_workers(false /* exit_on_failure */); 166 assert(v != 0, "Trying to set active workers to 0"); 167 log_trace(gc, task)("%s: using %d out of %d workers", name(), _active_workers, _total_workers); 168 return _active_workers; 169 } 170 171 // Add GC workers as needed. 172 void add_workers(bool initializing); 173 174 // Add GC workers as needed to reach the specified number of workers. 175 void add_workers(uint active_workers, bool initializing); 176 177 // Return the Ith worker. 178 AbstractGangWorker* worker(uint i) const; 179 180 // Base name (without worker id #) of threads. 181 const char* group_name() { return name(); } 182 183 void threads_do(ThreadClosure* tc) const; 184 185 // Create a GC worker and install it into the work gang. 186 virtual AbstractGangWorker* install_worker(uint which); 187 188 // Debugging. 189 const char* name() const { return _name; } 190 191 // Printing 192 void print_worker_threads_on(outputStream *st) const; 193 void print_worker_threads() const { 194 print_worker_threads_on(tty); 195 } 196 197 protected: 198 virtual AbstractGangWorker* allocate_worker(uint which) = 0; 199 }; 200 201 // An class representing a gang of workers. 202 class WorkGang: public AbstractWorkGang { 203 // To get access to the GangTaskDispatcher instance. 204 friend class GangWorker; 205 206 GangTaskDispatcher* const _dispatcher; 207 GangTaskDispatcher* dispatcher() const { 208 return _dispatcher; 209 } 210 211 public: 212 WorkGang(const char* name, 213 uint workers, 214 bool are_GC_task_threads, 215 bool are_ConcurrentGC_threads); 216 217 ~WorkGang(); 218 219 // Run a task using the current active number of workers, returns when the task is done. 220 virtual void run_task(AbstractGangTask* task); 221 // Run a task with the given number of workers, returns 222 // when the task is done. The number of workers must be at most the number of 223 // active workers. Additional workers may be created if an insufficient 224 // number currently exists. 225 void run_task(AbstractGangTask* task, uint num_workers); 226 227 protected: 228 virtual AbstractGangWorker* allocate_worker(uint which); 229 }; 230 231 // Several instances of this class run in parallel as workers for a gang. 232 class AbstractGangWorker: public WorkerThread { 233 public: 234 AbstractGangWorker(AbstractWorkGang* gang, uint id); 235 236 // The only real method: run a task for the gang. 237 virtual void run(); 238 // Predicate for Thread 239 virtual bool is_GC_task_thread() const; 240 virtual bool is_ConcurrentGC_thread() const; 241 // Printing 242 void print_on(outputStream* st) const; 243 virtual void print() const { print_on(tty); } 244 245 protected: 246 AbstractWorkGang* _gang; 247 248 virtual void initialize(); 249 virtual void loop() = 0; 250 251 AbstractWorkGang* gang() const { return _gang; } 252 }; 253 254 class GangWorker: public AbstractGangWorker { 255 public: 256 GangWorker(WorkGang* gang, uint id) : AbstractGangWorker(gang, id) {} 257 258 protected: 259 virtual void loop(); 260 261 private: 262 WorkData wait_for_task(); 263 void run_task(WorkData work); 264 void signal_task_done(); 265 266 WorkGang* gang() const { return (WorkGang*)_gang; } 267 }; 268 269 // A class that acts as a synchronisation barrier. Workers enter 270 // the barrier and must wait until all other workers have entered 271 // before any of them may leave. 272 273 class WorkGangBarrierSync : public StackObj { 274 protected: 275 Monitor _monitor; 276 uint _n_workers; 277 uint _n_completed; 278 bool _should_reset; 279 bool _aborted; 280 281 Monitor* monitor() { return &_monitor; } 282 uint n_workers() { return _n_workers; } 283 uint n_completed() { return _n_completed; } 284 bool should_reset() { return _should_reset; } 285 bool aborted() { return _aborted; } 286 287 void zero_completed() { _n_completed = 0; } 288 void inc_completed() { _n_completed++; } 289 void set_aborted() { _aborted = true; } 290 void set_should_reset(bool v) { _should_reset = v; } 291 292 public: 293 WorkGangBarrierSync(); 294 WorkGangBarrierSync(uint n_workers, const char* name); 295 296 // Set the number of workers that will use the barrier. 297 // Must be called before any of the workers start running. 298 void set_n_workers(uint n_workers); 299 300 // Enter the barrier. A worker that enters the barrier will 301 // not be allowed to leave until all other threads have 302 // also entered the barrier or the barrier is aborted. 303 // Returns false if the barrier was aborted. 304 bool enter(); 305 306 // Aborts the barrier and wakes up any threads waiting for 307 // the barrier to complete. The barrier will remain in the 308 // aborted state until the next call to set_n_workers(). 309 void abort(); 310 }; 311 312 // A class to manage claiming of subtasks within a group of tasks. The 313 // subtasks will be identified by integer indices, usually elements of an 314 // enumeration type. 315 316 class SubTasksDone: public CHeapObj<mtInternal> { 317 volatile uint* _tasks; 318 uint _n_tasks; 319 volatile uint _threads_completed; 320 #ifdef ASSERT 321 volatile uint _claimed; 322 #endif 323 324 // Set all tasks to unclaimed. 325 void clear(); 326 327 public: 328 // Initializes "this" to a state in which there are "n" tasks to be 329 // processed, none of the which are originally claimed. The number of 330 // threads doing the tasks is initialized 1. 331 SubTasksDone(uint n); 332 333 // True iff the object is in a valid state. 334 bool valid(); 335 336 // Returns "false" if the task "t" is unclaimed, and ensures that task is 337 // claimed. The task "t" is required to be within the range of "this". 338 bool is_task_claimed(uint t); 339 340 // The calling thread asserts that it has attempted to claim all the 341 // tasks that it will try to claim. Every thread in the parallel task 342 // must execute this. (When the last thread does so, the task array is 343 // cleared.) 344 // 345 // n_threads - Number of threads executing the sub-tasks. 346 void all_tasks_completed(uint n_threads); 347 348 // Destructor. 349 ~SubTasksDone(); 350 }; 351 352 // As above, but for sequential tasks, i.e. instead of claiming 353 // sub-tasks from a set (possibly an enumeration), claim sub-tasks 354 // in sequential order. This is ideal for claiming dynamically 355 // partitioned tasks (like striding in the parallel remembered 356 // set scanning). Note that unlike the above class this is 357 // a stack object - is there any reason for it not to be? 358 359 class SequentialSubTasksDone : public StackObj { 360 protected: 361 uint _n_tasks; // Total number of tasks available. 362 volatile uint _n_claimed; // Number of tasks claimed. 363 // _n_threads is used to determine when a sub task is done. 364 // See comments on SubTasksDone::_n_threads 365 uint _n_threads; // Total number of parallel threads. 366 volatile uint _n_completed; // Number of completed threads. 367 368 void clear(); 369 370 public: 371 SequentialSubTasksDone() { 372 clear(); 373 } 374 ~SequentialSubTasksDone() {} 375 376 // True iff the object is in a valid state. 377 bool valid(); 378 379 // number of tasks 380 uint n_tasks() const { return _n_tasks; } 381 382 // Get/set the number of parallel threads doing the tasks to t. 383 // Should be called before the task starts but it is safe 384 // to call this once a task is running provided that all 385 // threads agree on the number of threads. 386 uint n_threads() { return _n_threads; } 387 void set_n_threads(uint t) { _n_threads = t; } 388 389 // Set the number of tasks to be claimed to t. As above, 390 // should be called before the tasks start but it is safe 391 // to call this once a task is running provided all threads 392 // agree on the number of tasks. 393 void set_n_tasks(uint t) { _n_tasks = t; } 394 395 // Returns false if the next task in the sequence is unclaimed, 396 // and ensures that it is claimed. Will set t to be the index 397 // of the claimed task in the sequence. Will return true if 398 // the task cannot be claimed and there are none left to claim. 399 bool is_task_claimed(uint& t); 400 401 // The calling thread asserts that it has attempted to claim 402 // all the tasks it possibly can in the sequence. Every thread 403 // claiming tasks must promise call this. Returns true if this 404 // is the last thread to complete so that the thread can perform 405 // cleanup if necessary. 406 bool all_tasks_completed(); 407 }; 408 409 #endif // SHARE_VM_GC_SHARED_WORKGROUP_HPP