1 /* 2 * Copyright (c) 2002, 2020, 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 ThreadClosure; 54 class WorkGang; 55 56 // An abstract task to be worked on by a gang. 57 // You subclass this to supply your own work() method 58 class AbstractGangTask { 59 const char* _name; 60 const uint _gc_id; 61 62 public: AbstractGangTask(const char * name)63 explicit AbstractGangTask(const char* name) : 64 _name(name), 65 _gc_id(GCId::current_or_undefined()) 66 {} 67 68 // The abstract work method. 69 // The argument tells you which member of the gang you are. 70 virtual void work(uint worker_id) = 0; 71 72 // Debugging accessor for the name. name() const73 const char* name() const { return _name; } gc_id() const74 const uint gc_id() const { return _gc_id; } 75 }; 76 77 struct WorkData { 78 AbstractGangTask* _task; 79 uint _worker_id; WorkDataWorkData80 WorkData(AbstractGangTask* task, uint worker_id) : _task(task), _worker_id(worker_id) {} 81 }; 82 83 // Interface to handle the synchronization between the coordinator thread and the worker threads, 84 // when a task is dispatched out to the worker threads. 85 class GangTaskDispatcher : public CHeapObj<mtGC> { 86 public: ~GangTaskDispatcher()87 virtual ~GangTaskDispatcher() {} 88 89 // Coordinator API. 90 91 // Distributes the task out to num_workers workers. 92 // Returns when the task has been completed by all workers. 93 virtual void coordinator_execute_on_workers(AbstractGangTask* task, uint num_workers) = 0; 94 95 // Worker API. 96 97 // Waits for a task to become available to the worker. 98 // Returns when the worker has been assigned a task. 99 virtual WorkData worker_wait_for_task() = 0; 100 101 // Signal to the coordinator that the worker is done with the assigned task. 102 virtual void worker_done_with_task() = 0; 103 }; 104 105 // The work gang is the collection of workers to execute tasks. 106 // The number of workers run for a task is "_active_workers" 107 // while "_total_workers" is the number of available of workers. 108 class AbstractWorkGang : public CHeapObj<mtInternal> { 109 protected: 110 // The array of worker threads for this gang. 111 AbstractGangWorker** _workers; 112 // The count of the number of workers in the gang. 113 uint _total_workers; 114 // The currently active workers in this gang. 115 uint _active_workers; 116 // The count of created workers in the gang. 117 uint _created_workers; 118 // Printing support. 119 const char* _name; 120 ~AbstractWorkGang()121 ~AbstractWorkGang() {} 122 123 private: 124 // Initialize only instance data. 125 const bool _are_GC_task_threads; 126 const bool _are_ConcurrentGC_threads; 127 set_thread(uint worker_id,AbstractGangWorker * worker)128 void set_thread(uint worker_id, AbstractGangWorker* worker) { 129 _workers[worker_id] = worker; 130 } 131 132 public: AbstractWorkGang(const char * name,uint workers,bool are_GC_task_threads,bool are_ConcurrentGC_threads)133 AbstractWorkGang(const char* name, uint workers, bool are_GC_task_threads, bool are_ConcurrentGC_threads) : 134 _name(name), 135 _total_workers(workers), 136 _active_workers(UseDynamicNumberOfGCThreads ? 1U : workers), 137 _created_workers(0), 138 _are_GC_task_threads(are_GC_task_threads), 139 _are_ConcurrentGC_threads(are_ConcurrentGC_threads) 140 { } 141 142 // Initialize workers in the gang. Return true if initialization succeeded. 143 void initialize_workers(); 144 are_GC_task_threads() const145 bool are_GC_task_threads() const { return _are_GC_task_threads; } are_ConcurrentGC_threads() const146 bool are_ConcurrentGC_threads() const { return _are_ConcurrentGC_threads; } 147 total_workers() const148 uint total_workers() const { return _total_workers; } 149 created_workers() const150 uint created_workers() const { 151 return _created_workers; 152 } 153 active_workers() const154 virtual uint active_workers() const { 155 assert(_active_workers <= _total_workers, 156 "_active_workers: %u > _total_workers: %u", _active_workers, _total_workers); 157 assert(UseDynamicNumberOfGCThreads || _active_workers == _total_workers, 158 "Unless dynamic should use total workers"); 159 return _active_workers; 160 } 161 update_active_workers(uint v)162 uint update_active_workers(uint v) { 163 assert(v <= _total_workers, 164 "Trying to set more workers active than there are"); 165 _active_workers = MIN2(v, _total_workers); 166 add_workers(false /* exit_on_failure */); 167 assert(v != 0, "Trying to set active workers to 0"); 168 log_trace(gc, task)("%s: using %d out of %d workers", name(), _active_workers, _total_workers); 169 return _active_workers; 170 } 171 172 // Add GC workers as needed. 173 void add_workers(bool initializing); 174 175 // Add GC workers as needed to reach the specified number of workers. 176 void add_workers(uint active_workers, bool initializing); 177 178 // Return the Ith worker. 179 AbstractGangWorker* worker(uint i) const; 180 181 // Base name (without worker id #) of threads. group_name()182 const char* group_name() { return name(); } 183 184 void threads_do(ThreadClosure* tc) const; 185 186 // Create a GC worker and install it into the work gang. 187 virtual AbstractGangWorker* install_worker(uint which); 188 189 // Debugging. name() const190 const char* name() const { return _name; } 191 192 // Printing 193 void print_worker_threads_on(outputStream *st) const; print_worker_threads() const194 void print_worker_threads() const { 195 print_worker_threads_on(tty); 196 } 197 198 protected: 199 virtual AbstractGangWorker* allocate_worker(uint which) = 0; 200 }; 201 202 // An class representing a gang of workers. 203 class WorkGang: public AbstractWorkGang { 204 // To get access to the GangTaskDispatcher instance. 205 friend class GangWorker; 206 207 GangTaskDispatcher* const _dispatcher; dispatcher() const208 GangTaskDispatcher* dispatcher() const { 209 return _dispatcher; 210 } 211 212 public: 213 WorkGang(const char* name, 214 uint workers, 215 bool are_GC_task_threads, 216 bool are_ConcurrentGC_threads); 217 218 ~WorkGang(); 219 220 // Run a task using the current active number of workers, returns when the task is done. 221 virtual void run_task(AbstractGangTask* task); 222 // Run a task with the given number of workers, returns 223 // when the task is done. The number of workers must be at most the number of 224 // active workers. Additional workers may be created if an insufficient 225 // number currently exists. 226 void run_task(AbstractGangTask* task, uint num_workers); 227 228 protected: 229 virtual AbstractGangWorker* allocate_worker(uint which); 230 }; 231 232 // Several instances of this class run in parallel as workers for a gang. 233 class AbstractGangWorker: public WorkerThread { 234 public: 235 AbstractGangWorker(AbstractWorkGang* gang, uint id); 236 237 // The only real method: run a task for the gang. 238 virtual void run(); 239 // Predicate for Thread 240 virtual bool is_GC_task_thread() const; 241 virtual bool is_ConcurrentGC_thread() const; 242 // Printing 243 void print_on(outputStream* st) const; print() const244 virtual void print() const { print_on(tty); } 245 246 protected: 247 AbstractWorkGang* _gang; 248 249 virtual void initialize(); 250 virtual void loop() = 0; 251 gang() const252 AbstractWorkGang* gang() const { return _gang; } 253 }; 254 255 class GangWorker: public AbstractGangWorker { 256 public: GangWorker(WorkGang * gang,uint id)257 GangWorker(WorkGang* gang, uint id) : AbstractGangWorker(gang, id) {} 258 259 protected: 260 virtual void loop(); 261 262 private: 263 WorkData wait_for_task(); 264 void run_task(WorkData work); 265 void signal_task_done(); 266 gang() const267 WorkGang* gang() const { return (WorkGang*)_gang; } 268 }; 269 270 // A class that acts as a synchronisation barrier. Workers enter 271 // the barrier and must wait until all other workers have entered 272 // before any of them may leave. 273 274 class WorkGangBarrierSync : public StackObj { 275 protected: 276 Monitor _monitor; 277 uint _n_workers; 278 uint _n_completed; 279 bool _should_reset; 280 bool _aborted; 281 monitor()282 Monitor* monitor() { return &_monitor; } n_workers()283 uint n_workers() { return _n_workers; } n_completed()284 uint n_completed() { return _n_completed; } should_reset()285 bool should_reset() { return _should_reset; } aborted()286 bool aborted() { return _aborted; } 287 zero_completed()288 void zero_completed() { _n_completed = 0; } inc_completed()289 void inc_completed() { _n_completed++; } set_aborted()290 void set_aborted() { _aborted = true; } set_should_reset(bool v)291 void set_should_reset(bool v) { _should_reset = v; } 292 293 public: 294 WorkGangBarrierSync(); 295 WorkGangBarrierSync(uint n_workers, const char* name); 296 297 // Set the number of workers that will use the barrier. 298 // Must be called before any of the workers start running. 299 void set_n_workers(uint n_workers); 300 301 // Enter the barrier. A worker that enters the barrier will 302 // not be allowed to leave until all other threads have 303 // also entered the barrier or the barrier is aborted. 304 // Returns false if the barrier was aborted. 305 bool enter(); 306 307 // Aborts the barrier and wakes up any threads waiting for 308 // the barrier to complete. The barrier will remain in the 309 // aborted state until the next call to set_n_workers(). 310 void abort(); 311 }; 312 313 // A class to manage claiming of subtasks within a group of tasks. The 314 // subtasks will be identified by integer indices, usually elements of an 315 // enumeration type. 316 317 class SubTasksDone: public CHeapObj<mtInternal> { 318 volatile uint* _tasks; 319 uint _n_tasks; 320 volatile uint _threads_completed; 321 #ifdef ASSERT 322 volatile uint _claimed; 323 #endif 324 325 // Set all tasks to unclaimed. 326 void clear(); 327 328 NONCOPYABLE(SubTasksDone); 329 330 public: 331 // Initializes "this" to a state in which there are "n" tasks to be 332 // processed, none of the which are originally claimed. The number of 333 // threads doing the tasks is initialized 1. 334 SubTasksDone(uint n); 335 336 // True iff the object is in a valid state. 337 bool valid(); 338 339 // Returns "false" if the task "t" is unclaimed, and ensures that task is 340 // claimed. The task "t" is required to be within the range of "this". 341 bool is_task_claimed(uint t); 342 343 // The calling thread asserts that it has attempted to claim all the 344 // tasks that it will try to claim. Every thread in the parallel task 345 // must execute this. (When the last thread does so, the task array is 346 // cleared.) 347 // 348 // n_threads - Number of threads executing the sub-tasks. 349 void all_tasks_completed(uint n_threads); 350 351 // Destructor. 352 ~SubTasksDone(); 353 }; 354 355 // As above, but for sequential tasks, i.e. instead of claiming 356 // sub-tasks from a set (possibly an enumeration), claim sub-tasks 357 // in sequential order. This is ideal for claiming dynamically 358 // partitioned tasks (like striding in the parallel remembered 359 // set scanning). Note that unlike the above class this is 360 // a stack object - is there any reason for it not to be? 361 362 class SequentialSubTasksDone : public StackObj { 363 protected: 364 uint _n_tasks; // Total number of tasks available. 365 volatile uint _n_claimed; // Number of tasks claimed. 366 // _n_threads is used to determine when a sub task is done. 367 // See comments on SubTasksDone::_n_threads 368 uint _n_threads; // Total number of parallel threads. 369 volatile uint _n_completed; // Number of completed threads. 370 371 void clear(); 372 373 public: SequentialSubTasksDone()374 SequentialSubTasksDone() { 375 clear(); 376 } ~SequentialSubTasksDone()377 ~SequentialSubTasksDone() {} 378 379 // True iff the object is in a valid state. 380 bool valid(); 381 382 // number of tasks n_tasks() const383 uint n_tasks() const { return _n_tasks; } 384 385 // Get/set the number of parallel threads doing the tasks to t. 386 // Should be called before the task starts but it is safe 387 // to call this once a task is running provided that all 388 // threads agree on the number of threads. n_threads()389 uint n_threads() { return _n_threads; } set_n_threads(uint t)390 void set_n_threads(uint t) { _n_threads = t; } 391 392 // Set the number of tasks to be claimed to t. As above, 393 // should be called before the tasks start but it is safe 394 // to call this once a task is running provided all threads 395 // agree on the number of tasks. set_n_tasks(uint t)396 void set_n_tasks(uint t) { _n_tasks = t; } 397 398 // Returns false if the next task in the sequence is unclaimed, 399 // and ensures that it is claimed. Will set t to be the index 400 // of the claimed task in the sequence. Will return true if 401 // the task cannot be claimed and there are none left to claim. 402 bool is_task_claimed(uint& t); 403 404 // The calling thread asserts that it has attempted to claim 405 // all the tasks it possibly can in the sequence. Every thread 406 // claiming tasks must promise call this. Returns true if this 407 // is the last thread to complete so that the thread can perform 408 // cleanup if necessary. 409 bool all_tasks_completed(); 410 }; 411 412 #endif // SHARE_VM_GC_SHARED_WORKGROUP_HPP 413