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 // 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: using %d out of %d", _active_workers, _total_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 WorkGang* gang() const { return (WorkGang*)_gang; } 238 }; 239 240 // A class that acts as a synchronisation barrier. Workers enter 241 // the barrier and must wait until all other workers have entered 242 // before any of them may leave. 243 244 class WorkGangBarrierSync : public StackObj { 245 protected: 246 Monitor _monitor; 247 uint _n_workers; 248 uint _n_completed; 249 bool _should_reset; 250 bool _aborted; 251 252 Monitor* monitor() { return &_monitor; } 253 uint n_workers() { return _n_workers; } 254 uint n_completed() { return _n_completed; } 255 bool should_reset() { return _should_reset; } 256 bool aborted() { return _aborted; } 257 258 void zero_completed() { _n_completed = 0; } 259 void inc_completed() { _n_completed++; } 260 void set_aborted() { _aborted = true; } 261 void set_should_reset(bool v) { _should_reset = v; } 262 263 public: 264 WorkGangBarrierSync(); 265 WorkGangBarrierSync(uint n_workers, const char* name); 266 267 // Set the number of workers that will use the barrier. 268 // Must be called before any of the workers start running. 269 void set_n_workers(uint n_workers); 270 271 // Enter the barrier. A worker that enters the barrier will 272 // not be allowed to leave until all other threads have 273 // also entered the barrier or the barrier is aborted. 274 // Returns false if the barrier was aborted. 275 bool enter(); 276 277 // Aborts the barrier and wakes up any threads waiting for 278 // the barrier to complete. The barrier will remain in the 279 // aborted state until the next call to set_n_workers(). 280 void abort(); 281 }; 282 283 // A class to manage claiming of subtasks within a group of tasks. The 284 // subtasks will be identified by integer indices, usually elements of an 285 // enumeration type. 286 287 class SubTasksDone: public CHeapObj<mtInternal> { 288 uint* _tasks; 289 uint _n_tasks; 290 uint _threads_completed; 291 #ifdef ASSERT 292 volatile uint _claimed; 293 #endif 294 295 // Set all tasks to unclaimed. 296 void clear(); 297 298 public: 299 // Initializes "this" to a state in which there are "n" tasks to be 300 // processed, none of the which are originally claimed. The number of 301 // threads doing the tasks is initialized 1. 302 SubTasksDone(uint n); 303 304 // True iff the object is in a valid state. 305 bool valid(); 306 307 // Returns "false" if the task "t" is unclaimed, and ensures that task is 308 // claimed. The task "t" is required to be within the range of "this". 309 bool is_task_claimed(uint t); 310 311 // The calling thread asserts that it has attempted to claim all the 312 // tasks that it will try to claim. Every thread in the parallel task 313 // must execute this. (When the last thread does so, the task array is 314 // cleared.) 315 // 316 // n_threads - Number of threads executing the sub-tasks. 317 void all_tasks_completed(uint n_threads); 318 319 // Destructor. 320 ~SubTasksDone(); 321 }; 322 323 // As above, but for sequential tasks, i.e. instead of claiming 324 // sub-tasks from a set (possibly an enumeration), claim sub-tasks 325 // in sequential order. This is ideal for claiming dynamically 326 // partitioned tasks (like striding in the parallel remembered 327 // set scanning). Note that unlike the above class this is 328 // a stack object - is there any reason for it not to be? 329 330 class SequentialSubTasksDone : public StackObj { 331 protected: 332 uint _n_tasks; // Total number of tasks available. 333 uint _n_claimed; // Number of tasks claimed. 334 // _n_threads is used to determine when a sub task is done. 335 // See comments on SubTasksDone::_n_threads 336 uint _n_threads; // Total number of parallel threads. 337 uint _n_completed; // Number of completed threads. 338 339 void clear(); 340 341 public: 342 SequentialSubTasksDone() { 343 clear(); 344 } 345 ~SequentialSubTasksDone() {} 346 347 // True iff the object is in a valid state. 348 bool valid(); 349 350 // number of tasks 351 uint n_tasks() const { return _n_tasks; } 352 353 // Get/set the number of parallel threads doing the tasks to t. 354 // Should be called before the task starts but it is safe 355 // to call this once a task is running provided that all 356 // threads agree on the number of threads. 357 uint n_threads() { return _n_threads; } 358 void set_n_threads(uint t) { _n_threads = t; } 359 360 // Set the number of tasks to be claimed to t. As above, 361 // should be called before the tasks start but it is safe 362 // to call this once a task is running provided all threads 363 // agree on the number of tasks. 364 void set_n_tasks(uint t) { _n_tasks = t; } 365 366 // Returns false if the next task in the sequence is unclaimed, 367 // and ensures that it is claimed. Will set t to be the index 368 // of the claimed task in the sequence. Will return true if 369 // the task cannot be claimed and there are none left to claim. 370 bool is_task_claimed(uint& t); 371 372 // The calling thread asserts that it has attempted to claim 373 // all the tasks it possibly can in the sequence. Every thread 374 // claiming tasks must promise call this. Returns true if this 375 // is the last thread to complete so that the thread can perform 376 // cleanup if necessary. 377 bool all_tasks_completed(); 378 }; 379 380 #endif // SHARE_VM_GC_SHARED_WORKGROUP_HPP