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 bool 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 void set_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 assert(UseDynamicNumberOfGCThreads || _active_workers == _total_workers,
166 "Unless dynamic should use total workers");
167 log_info(gc, task)("GC Workers: using %d out of %d", _active_workers, _total_workers);
168 }
169
170 // Add GC workers as needed.
171 bool add_workers(bool initializing);
172
173 // Return the Ith worker.
174 AbstractGangWorker* worker(uint i) const;
175
176 void threads_do(ThreadClosure* tc) const;
177
178 // Create a GC worker and install it into the work gang.
179 virtual AbstractGangWorker* install_worker(uint which);
180
181 // Debugging.
182 const char* name() const { return _name; }
183
184 // Printing
185 void print_worker_threads_on(outputStream *st) const;
186 void print_worker_threads() const {
187 print_worker_threads_on(tty);
188 }
189
190 protected:
191 virtual AbstractGangWorker* allocate_worker(uint which) = 0;
192 };
193
194 // An class representing a gang of workers.
195 class WorkGang: public AbstractWorkGang {
196 // To get access to the GangTaskDispatcher instance.
197 friend class GangWorker;
198
199 // Never deleted.
200 ~WorkGang();
201
202 GangTaskDispatcher* const _dispatcher;
203 GangTaskDispatcher* dispatcher() const {
204 return _dispatcher;
205 }
206
207 public:
208 WorkGang(const char* name,
209 uint workers,
210 bool are_GC_task_threads,
211 bool are_ConcurrentGC_threads);
212
213 // Run a task, returns when the task is done.
214 virtual void run_task(AbstractGangTask* task);
215
216 protected:
217 virtual AbstractGangWorker* allocate_worker(uint which);
218 };
219
220 // Several instances of this class run in parallel as workers for a gang.
221 class AbstractGangWorker: public WorkerThread {
222 public:
223 AbstractGangWorker(AbstractWorkGang* gang, uint id);
224
225 // The only real method: run a task for the gang.
226 virtual void run();
227 // Predicate for Thread
228 virtual bool is_GC_task_thread() const;
229 virtual bool is_ConcurrentGC_thread() const;
230 // Printing
231 void print_on(outputStream* st) const;
232 virtual void print() const { print_on(tty); }
233
234 protected:
235 AbstractWorkGang* _gang;
236
237 virtual void initialize();
238 virtual void loop() = 0;
239
240 AbstractWorkGang* gang() const { return _gang; }
241 };
242
243 class GangWorker: public AbstractGangWorker {
244 public:
245 GangWorker(WorkGang* gang, uint id) : AbstractGangWorker(gang, id) {}
246
247 protected:
248 virtual void loop();
249
250 private:
251 WorkData wait_for_task();
252 void run_task(WorkData work);
253 void signal_task_done();
254
255 WorkGang* gang() const { return (WorkGang*)_gang; }
256 };
257
258 // A class that acts as a synchronisation barrier. Workers enter
259 // the barrier and must wait until all other workers have entered
260 // before any of them may leave.
261
262 class WorkGangBarrierSync : public StackObj {
263 protected:
264 Monitor _monitor;
265 uint _n_workers;
266 uint _n_completed;
267 bool _should_reset;
268 bool _aborted;
269
270 Monitor* monitor() { return &_monitor; }
271 uint n_workers() { return _n_workers; }
272 uint n_completed() { return _n_completed; }
273 bool should_reset() { return _should_reset; }
274 bool aborted() { return _aborted; }
275
276 void zero_completed() { _n_completed = 0; }
277 void inc_completed() { _n_completed++; }
278 void set_aborted() { _aborted = true; }
279 void set_should_reset(bool v) { _should_reset = v; }
280
281 public:
282 WorkGangBarrierSync();
283 WorkGangBarrierSync(uint n_workers, const char* name);
284
285 // Set the number of workers that will use the barrier.
286 // Must be called before any of the workers start running.
287 void set_n_workers(uint n_workers);
288
289 // Enter the barrier. A worker that enters the barrier will
290 // not be allowed to leave until all other threads have
291 // also entered the barrier or the barrier is aborted.
292 // Returns false if the barrier was aborted.
293 bool enter();
294
295 // Aborts the barrier and wakes up any threads waiting for
296 // the barrier to complete. The barrier will remain in the
297 // aborted state until the next call to set_n_workers().
298 void abort();
299 };
300
301 // A class to manage claiming of subtasks within a group of tasks. The
302 // subtasks will be identified by integer indices, usually elements of an
303 // enumeration type.
304
305 class SubTasksDone: public CHeapObj<mtInternal> {
306 uint* _tasks;
307 uint _n_tasks;
308 uint _threads_completed;
309 #ifdef ASSERT
310 volatile uint _claimed;
311 #endif
312
313 // Set all tasks to unclaimed.
314 void clear();
315
316 public:
317 // Initializes "this" to a state in which there are "n" tasks to be
318 // processed, none of the which are originally claimed. The number of
319 // threads doing the tasks is initialized 1.
320 SubTasksDone(uint n);
321
322 // True iff the object is in a valid state.
323 bool valid();
324
325 // Returns "false" if the task "t" is unclaimed, and ensures that task is
326 // claimed. The task "t" is required to be within the range of "this".
327 bool is_task_claimed(uint t);
328
329 // The calling thread asserts that it has attempted to claim all the
330 // tasks that it will try to claim. Every thread in the parallel task
331 // must execute this. (When the last thread does so, the task array is
332 // cleared.)
333 //
334 // n_threads - Number of threads executing the sub-tasks.
335 void all_tasks_completed(uint n_threads);
336
337 // Destructor.
338 ~SubTasksDone();
339 };
340
341 // As above, but for sequential tasks, i.e. instead of claiming
342 // sub-tasks from a set (possibly an enumeration), claim sub-tasks
343 // in sequential order. This is ideal for claiming dynamically
344 // partitioned tasks (like striding in the parallel remembered
345 // set scanning). Note that unlike the above class this is
346 // a stack object - is there any reason for it not to be?
347
348 class SequentialSubTasksDone : public StackObj {
349 protected:
350 uint _n_tasks; // Total number of tasks available.
351 uint _n_claimed; // Number of tasks claimed.
352 // _n_threads is used to determine when a sub task is done.
353 // See comments on SubTasksDone::_n_threads
354 uint _n_threads; // Total number of parallel threads.
355 uint _n_completed; // Number of completed threads.
356
357 void clear();
358
359 public:
360 SequentialSubTasksDone() {
361 clear();
362 }
363 ~SequentialSubTasksDone() {}
364
365 // True iff the object is in a valid state.
366 bool valid();
367
368 // number of tasks
369 uint n_tasks() const { return _n_tasks; }
370
371 // Get/set the number of parallel threads doing the tasks to t.
372 // Should be called before the task starts but it is safe
373 // to call this once a task is running provided that all
374 // threads agree on the number of threads.
375 uint n_threads() { return _n_threads; }
376 void set_n_threads(uint t) { _n_threads = t; }
377
378 // Set the number of tasks to be claimed to t. As above,
379 // should be called before the tasks start but it is safe
380 // to call this once a task is running provided all threads
381 // agree on the number of tasks.
382 void set_n_tasks(uint t) { _n_tasks = t; }
383
384 // Returns false if the next task in the sequence is unclaimed,
385 // and ensures that it is claimed. Will set t to be the index
386 // of the claimed task in the sequence. Will return true if
387 // the task cannot be claimed and there are none left to claim.
388 bool is_task_claimed(uint& t);
389
390 // The calling thread asserts that it has attempted to claim
391 // all the tasks it possibly can in the sequence. Every thread
392 // claiming tasks must promise call this. Returns true if this
393 // is the last thread to complete so that the thread can perform
394 // cleanup if necessary.
395 bool all_tasks_completed();
396 };
397
398 #endif // SHARE_VM_GC_SHARED_WORKGROUP_HPP