1 /*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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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_trace(gc, task)("%s: using %d out of %d workers", name(), _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 // Base name (without worker id #) of threads.
179 const char* group_name() { return name(); }
180
181 void threads_do(ThreadClosure* tc) const;
182
183 // Create a GC worker and install it into the work gang.
184 virtual AbstractGangWorker* install_worker(uint which);
185
186 // Debugging.
187 const char* name() const { return _name; }
188
189 // Printing
190 void print_worker_threads_on(outputStream *st) const;
191 void print_worker_threads() const {
192 print_worker_threads_on(tty);
193 }
194
195 protected:
196 virtual AbstractGangWorker* allocate_worker(uint which) = 0;
197 };
198
199 // An class representing a gang of workers.
200 class WorkGang: public AbstractWorkGang {
201 // To get access to the GangTaskDispatcher instance.
202 friend class GangWorker;
203
204 // Never deleted.
205 ~WorkGang();
206
207 GangTaskDispatcher* const _dispatcher;
208 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 // Run a task using the current active number of workers, returns when the task is done.
219 virtual void run_task(AbstractGangTask* task);
220 // Run a task with the given number of workers, returns
221 // when the task is done. The number of workers must be at most the number of
222 // active workers. Additional workers may be created if an insufficient
223 // number currently exists.
224 void run_task(AbstractGangTask* task, uint num_workers);
225
226 protected:
227 virtual AbstractGangWorker* allocate_worker(uint which);
228 };
229
230 // Several instances of this class run in parallel as workers for a gang.
231 class AbstractGangWorker: public WorkerThread {
232 public:
233 AbstractGangWorker(AbstractWorkGang* gang, uint id);
234
235 // The only real method: run a task for the gang.
236 virtual void run();
237 // Predicate for Thread
238 virtual bool is_GC_task_thread() const;
239 virtual bool is_ConcurrentGC_thread() const;
240 // Printing
241 void print_on(outputStream* st) const;
242 virtual void print() const { print_on(tty); }
243
244 protected:
245 AbstractWorkGang* _gang;
246
247 virtual void initialize();
248 virtual void loop() = 0;
249
250 AbstractWorkGang* gang() const { return _gang; }
251 };
252
253 class GangWorker: public AbstractGangWorker {
254 public:
255 GangWorker(WorkGang* gang, uint id) : AbstractGangWorker(gang, id) {}
256
257 protected:
258 virtual void loop();
259
260 private:
261 WorkData wait_for_task();
262 void run_task(WorkData work);
263 void signal_task_done();
264
265 WorkGang* gang() const { return (WorkGang*)_gang; }
266 };
267
268 // A class that acts as a synchronisation barrier. Workers enter
269 // the barrier and must wait until all other workers have entered
270 // before any of them may leave.
271
272 class WorkGangBarrierSync : public StackObj {
273 protected:
274 Monitor _monitor;
275 uint _n_workers;
276 uint _n_completed;
277 bool _should_reset;
278 bool _aborted;
279
280 Monitor* monitor() { return &_monitor; }
281 uint n_workers() { return _n_workers; }
282 uint n_completed() { return _n_completed; }
283 bool should_reset() { return _should_reset; }
284 bool aborted() { return _aborted; }
285
286 void zero_completed() { _n_completed = 0; }
287 void inc_completed() { _n_completed++; }
288 void set_aborted() { _aborted = true; }
289 void set_should_reset(bool v) { _should_reset = v; }
290
291 public:
292 WorkGangBarrierSync();
293 WorkGangBarrierSync(uint n_workers, const char* name);
294
295 // Set the number of workers that will use the barrier.
296 // Must be called before any of the workers start running.
297 void set_n_workers(uint n_workers);
298
299 // Enter the barrier. A worker that enters the barrier will
300 // not be allowed to leave until all other threads have
301 // also entered the barrier or the barrier is aborted.
302 // Returns false if the barrier was aborted.
303 bool enter();
304
305 // Aborts the barrier and wakes up any threads waiting for
306 // the barrier to complete. The barrier will remain in the
307 // aborted state until the next call to set_n_workers().
308 void abort();
309 };
310
311 // A class to manage claiming of subtasks within a group of tasks. The
312 // subtasks will be identified by integer indices, usually elements of an
313 // enumeration type.
314
315 class SubTasksDone: public CHeapObj<mtInternal> {
316 uint* _tasks;
317 uint _n_tasks;
318 uint _threads_completed;
319 #ifdef ASSERT
320 volatile uint _claimed;
321 #endif
322
323 // Set all tasks to unclaimed.
324 void clear();
325
326 public:
327 // Initializes "this" to a state in which there are "n" tasks to be
328 // processed, none of the which are originally claimed. The number of
329 // threads doing the tasks is initialized 1.
330 SubTasksDone(uint n);
331
332 // True iff the object is in a valid state.
333 bool valid();
334
335 // Returns "false" if the task "t" is unclaimed, and ensures that task is
336 // claimed. The task "t" is required to be within the range of "this".
337 bool is_task_claimed(uint t);
338
339 // The calling thread asserts that it has attempted to claim all the
340 // tasks that it will try to claim. Every thread in the parallel task
341 // must execute this. (When the last thread does so, the task array is
342 // cleared.)
343 //
344 // n_threads - Number of threads executing the sub-tasks.
345 void all_tasks_completed(uint n_threads);
346
347 // Destructor.
348 ~SubTasksDone();
349 };
350
351 // As above, but for sequential tasks, i.e. instead of claiming
352 // sub-tasks from a set (possibly an enumeration), claim sub-tasks
353 // in sequential order. This is ideal for claiming dynamically
354 // partitioned tasks (like striding in the parallel remembered
355 // set scanning). Note that unlike the above class this is
356 // a stack object - is there any reason for it not to be?
357
358 class SequentialSubTasksDone : public StackObj {
359 protected:
360 uint _n_tasks; // Total number of tasks available.
361 uint _n_claimed; // Number of tasks claimed.
362 // _n_threads is used to determine when a sub task is done.
363 // See comments on SubTasksDone::_n_threads
364 uint _n_threads; // Total number of parallel threads.
365 uint _n_completed; // Number of completed threads.
366
367 void clear();
368
369 public:
370 SequentialSubTasksDone() {
371 clear();
372 }
373 ~SequentialSubTasksDone() {}
374
375 // True iff the object is in a valid state.
376 bool valid();
377
378 // number of tasks
379 uint n_tasks() const { return _n_tasks; }
380
381 // Get/set the number of parallel threads doing the tasks to t.
382 // Should be called before the task starts but it is safe
383 // to call this once a task is running provided that all
384 // threads agree on the number of threads.
385 uint n_threads() { return _n_threads; }
386 void set_n_threads(uint t) { _n_threads = t; }
387
388 // Set the number of tasks to be claimed to t. As above,
389 // should be called before the tasks start but it is safe
390 // to call this once a task is running provided all threads
391 // agree on the number of tasks.
392 void set_n_tasks(uint t) { _n_tasks = t; }
393
394 // Returns false if the next task in the sequence is unclaimed,
395 // and ensures that it is claimed. Will set t to be the index
396 // of the claimed task in the sequence. Will return true if
397 // the task cannot be claimed and there are none left to claim.
398 bool is_task_claimed(uint& t);
399
400 // The calling thread asserts that it has attempted to claim
401 // all the tasks it possibly can in the sequence. Every thread
402 // claiming tasks must promise call this. Returns true if this
403 // is the last thread to complete so that the thread can perform
404 // cleanup if necessary.
405 bool all_tasks_completed();
406 };
407
408 #endif // SHARE_VM_GC_SHARED_WORKGROUP_HPP