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 "runtime/thread.inline.hpp"
29
30 // Task class hierarchy:
31 // AbstractGangTask
32 //
33 // Gang/Group class hierarchy:
34 // AbstractWorkGang
35 // WorkGang
36 // YieldingFlexibleWorkGang (defined in another file)
37 //
38 // Worker class hierarchy:
39 // AbstractGangWorker (subclass of WorkerThread)
40 // GangWorker
41 // YieldingFlexibleGangWorker (defined in another file)
42
43 // Forward declarations of classes defined here
44
45 class AbstractGangWorker;
46 class GangWorker;
47 class WorkData;
48
49 // An abstract task to be worked on by a gang.
50 // You subclass this to supply your own work() method
51 class AbstractGangTask VALUE_OBJ_CLASS_SPEC {
52 const char* _name;
53
54 public:
55 AbstractGangTask(const char* name) : _name(name) {}
56
57 // The abstract work method.
58 // The argument tells you which member of the gang you are.
59 virtual void work(uint worker_id) = 0;
60
61 // Debugging accessor for the name.
62 const char* name() const { return _name; }
63 };
64
65
66 // The work gang is the collection of workers to execute tasks.
67 // The number of workers run for a task is "_active_workers"
68 // while "_total_workers" is the number of available of workers.
69 class AbstractWorkGang : public CHeapObj<mtInternal> {
70 protected:
71 // The array of worker threads for this gang.
72 AbstractGangWorker** _workers;
73 // The count of the number of workers in the gang.
74 uint _total_workers;
75 // The currently active workers in this gang.
76 uint _active_workers;
77 // Printing support.
78 const char* _name;
79
80 private:
81 // Initialize only instance data.
82 const bool _are_GC_task_threads;
83 const bool _are_ConcurrentGC_threads;
84
85 public:
86 AbstractWorkGang(const char* name, uint workers, bool are_GC_task_threads, bool are_ConcurrentGC_threads) :
87 _name(name),
88 _total_workers(workers),
89 _active_workers(UseDynamicNumberOfGCThreads ? 1U : workers),
90 _are_GC_task_threads(are_GC_task_threads),
91 _are_ConcurrentGC_threads(are_ConcurrentGC_threads)
92 { }
93
94 virtual AbstractGangWorker* allocate_worker(uint which) = 0;
95
96 // Initialize workers in the gang. Return true if initialization succeeded.
97 bool initialize_workers();
98
99 bool are_GC_task_threads() const { return _are_GC_task_threads; }
100 bool are_ConcurrentGC_threads() const { return _are_ConcurrentGC_threads; }
101
102 uint total_workers() const { return _total_workers; }
103
104 virtual uint active_workers() const {
105 assert(_active_workers <= _total_workers,
106 err_msg("_active_workers: %u > _total_workers: %u", _active_workers, _total_workers));
107 assert(UseDynamicNumberOfGCThreads || _active_workers == _total_workers,
108 "Unless dynamic should use total workers");
109 return _active_workers;
110 }
111 void set_active_workers(uint v) {
112 assert(v <= _total_workers,
113 "Trying to set more workers active than there are");
114 _active_workers = MIN2(v, _total_workers);
115 assert(v != 0, "Trying to set active workers to 0");
116 _active_workers = MAX2(1U, _active_workers);
117 assert(UseDynamicNumberOfGCThreads || _active_workers == _total_workers,
118 "Unless dynamic should use total workers");
119 }
120
121 // Return the Ith worker.
122 AbstractGangWorker* worker(uint i) const;
123
124 void threads_do(ThreadClosure* tc) const;
125
126 // Debugging.
127 const char* name() const { return _name; }
128
129 // Printing
130 void print_worker_threads_on(outputStream *st) const;
131 void print_worker_threads() const {
132 print_worker_threads_on(tty);
133 }
134 };
135
136 // An class representing a gang of workers.
137 class WorkGang: public AbstractWorkGang {
138 private:
139 // Never deleted.
140 ~WorkGang();
141 public:
142 WorkGang(const char* name,
143 uint workers,
144 bool are_GC_task_threads,
145 bool are_ConcurrentGC_threads);
146
147 // Run a task, returns when the task is done.
148 virtual void run_task(AbstractGangTask* task);
149 void run_task(AbstractGangTask* task, uint no_of_parallel_workers);
150
151 // Return true if more workers should be applied to the task.
152 virtual bool needs_more_workers() const {
153 return _started_workers < _active_workers;
154 }
155
156 protected:
157 // The monitor which protects these data,
158 // and notifies of changes in it.
159 Monitor* _monitor;
160 // The task for this gang.
161 AbstractGangTask* _task;
162 // A sequence number for the current task.
163 int _sequence_number;
164 // The number of started workers.
165 uint _started_workers;
166 // The number of finished workers.
167 uint _finished_workers;
168
169 public:
170 virtual AbstractGangWorker* allocate_worker(uint which);
171
172 // Accessors for fields
173 Monitor* monitor() const {
174 return _monitor;
175 }
176 AbstractGangTask* task() const {
177 return _task;
178 }
179 int sequence_number() const {
180 return _sequence_number;
181 }
182 uint started_workers() const {
183 return _started_workers;
184 }
185 uint finished_workers() const {
186 return _finished_workers;
187 }
188 // Predicates.
189 bool is_idle() const {
190 return (task() == NULL);
191 }
192 // Return the Ith gang worker.
193 GangWorker* gang_worker(uint i) const;
194
195 protected:
196 friend class GangWorker;
197 // Note activation and deactivation of workers.
198 // These methods should only be called with the mutex held.
199 void internal_worker_poll(WorkData* data) const;
200 void internal_note_start();
201 void internal_note_finish();
202 };
203
204 class WorkData: public StackObj {
205 // This would be a struct, but I want accessor methods.
206 private:
207 AbstractGangTask* _task;
208 int _sequence_number;
209 public:
210 // Constructor and destructor
211 WorkData() {
212 _task = NULL;
213 _sequence_number = 0;
214 }
215 ~WorkData() {
216 }
217 AbstractGangTask* task() const { return _task; }
218 void set_task(AbstractGangTask* value) { _task = value; }
219 int sequence_number() const { return _sequence_number; }
220 void set_sequence_number(int value) { _sequence_number = value; }
221 };
222
223 // Several instances of this class run in parallel as workers for a gang.
224 class AbstractGangWorker: public WorkerThread {
225 public:
226 // Constructors and destructor.
227 AbstractGangWorker(AbstractWorkGang* gang, uint id);
228
229 // The only real method: run a task for the gang.
230 virtual void run();
231 // Predicate for Thread
232 virtual bool is_GC_task_thread() const;
233 virtual bool is_ConcurrentGC_thread() const;
234 // Printing
235 void print_on(outputStream* st) const;
236 virtual void print() const { print_on(tty); }
237
238 protected:
239 AbstractWorkGang* _gang;
240
241 virtual void initialize();
242 virtual void loop() = 0;
243
244 AbstractWorkGang* gang() const { return _gang; }
245 };
246
247 class GangWorker: public AbstractGangWorker {
248 public:
249 GangWorker(WorkGang* gang, uint id) : AbstractGangWorker(gang, id) {}
250
251 protected:
252 virtual void loop();
253
254 private:
255 WorkGang* gang() const { return (WorkGang*)_gang; }
256 };
257
258 // Dynamic number of worker threads
259 //
260 // This type of work gang is used to run different numbers of
261 // worker threads at different times. The
262 // number of workers run for a task is "_active_workers"
263 // instead of "_total_workers" in a WorkGang. The method
264 // "needs_more_workers()" returns true until "_active_workers"
265 // have been started and returns false afterwards. The
266 // implementation of "needs_more_workers()" in WorkGang always
267 // returns true so that all workers are started. The method
268 // "loop()" in GangWorker was modified to ask "needs_more_workers()"
269 // in its loop to decide if it should start working on a task.
270 // A worker in "loop()" waits for notification on the WorkGang
271 // monitor and execution of each worker as it checks for work
272 // is serialized via the same monitor. The "needs_more_workers()"
273 // call is serialized and additionally the calculation for the
274 // "part" (effectively the worker id for executing the task) is
275 // serialized to give each worker a unique "part". Workers that
276 // are not needed for this tasks (i.e., "_active_workers" have
277 // been started before it, continue to wait for work.
278
279 // A class that acts as a synchronisation barrier. Workers enter
280 // the barrier and must wait until all other workers have entered
281 // before any of them may leave.
282
283 class WorkGangBarrierSync : public StackObj {
284 protected:
285 Monitor _monitor;
286 uint _n_workers;
287 uint _n_completed;
288 bool _should_reset;
289 bool _aborted;
290
291 Monitor* monitor() { return &_monitor; }
292 uint n_workers() { return _n_workers; }
293 uint n_completed() { return _n_completed; }
294 bool should_reset() { return _should_reset; }
295 bool aborted() { return _aborted; }
296
297 void zero_completed() { _n_completed = 0; }
298 void inc_completed() { _n_completed++; }
299 void set_aborted() { _aborted = true; }
300 void set_should_reset(bool v) { _should_reset = v; }
301
302 public:
303 WorkGangBarrierSync();
304 WorkGangBarrierSync(uint n_workers, const char* name);
305
306 // Set the number of workers that will use the barrier.
307 // Must be called before any of the workers start running.
308 void set_n_workers(uint n_workers);
309
310 // Enter the barrier. A worker that enters the barrier will
311 // not be allowed to leave until all other threads have
312 // also entered the barrier or the barrier is aborted.
313 // Returns false if the barrier was aborted.
314 bool enter();
315
316 // Aborts the barrier and wakes up any threads waiting for
317 // the barrier to complete. The barrier will remain in the
318 // aborted state until the next call to set_n_workers().
319 void abort();
320 };
321
322 // A class to manage claiming of subtasks within a group of tasks. The
323 // subtasks will be identified by integer indices, usually elements of an
324 // enumeration type.
325
326 class SubTasksDone: public CHeapObj<mtInternal> {
327 uint* _tasks;
328 uint _n_tasks;
329 uint _threads_completed;
330 #ifdef ASSERT
331 volatile uint _claimed;
332 #endif
333
334 // Set all tasks to unclaimed.
335 void clear();
336
337 public:
338 // Initializes "this" to a state in which there are "n" tasks to be
339 // processed, none of the which are originally claimed. The number of
340 // threads doing the tasks is initialized 1.
341 SubTasksDone(uint n);
342
343 // True iff the object is in a valid state.
344 bool valid();
345
346 // Returns "false" if the task "t" is unclaimed, and ensures that task is
347 // claimed. The task "t" is required to be within the range of "this".
348 bool is_task_claimed(uint t);
349
350 // The calling thread asserts that it has attempted to claim all the
351 // tasks that it will try to claim. Every thread in the parallel task
352 // must execute this. (When the last thread does so, the task array is
353 // cleared.)
354 //
355 // n_threads - Number of threads executing the sub-tasks.
356 void all_tasks_completed(uint n_threads);
357
358 // Destructor.
359 ~SubTasksDone();
360 };
361
362 // As above, but for sequential tasks, i.e. instead of claiming
363 // sub-tasks from a set (possibly an enumeration), claim sub-tasks
364 // in sequential order. This is ideal for claiming dynamically
365 // partitioned tasks (like striding in the parallel remembered
366 // set scanning). Note that unlike the above class this is
367 // a stack object - is there any reason for it not to be?
368
369 class SequentialSubTasksDone : public StackObj {
370 protected:
371 uint _n_tasks; // Total number of tasks available.
372 uint _n_claimed; // Number of tasks claimed.
373 // _n_threads is used to determine when a sub task is done.
374 // See comments on SubTasksDone::_n_threads
375 uint _n_threads; // Total number of parallel threads.
376 uint _n_completed; // Number of completed threads.
377
378 void clear();
379
380 public:
381 SequentialSubTasksDone() {
382 clear();
383 }
384 ~SequentialSubTasksDone() {}
385
386 // True iff the object is in a valid state.
387 bool valid();
388
389 // number of tasks
390 uint n_tasks() const { return _n_tasks; }
391
392 // Get/set the number of parallel threads doing the tasks to t.
393 // Should be called before the task starts but it is safe
394 // to call this once a task is running provided that all
395 // threads agree on the number of threads.
396 uint n_threads() { return _n_threads; }
397 void set_n_threads(uint t) { _n_threads = t; }
398
399 // Set the number of tasks to be claimed to t. As above,
400 // should be called before the tasks start but it is safe
401 // to call this once a task is running provided all threads
402 // agree on the number of tasks.
403 void set_n_tasks(uint t) { _n_tasks = t; }
404
405 // Returns false if the next task in the sequence is unclaimed,
406 // and ensures that it is claimed. Will set t to be the index
407 // of the claimed task in the sequence. Will return true if
408 // the task cannot be claimed and there are none left to claim.
409 bool is_task_claimed(uint& t);
410
411 // The calling thread asserts that it has attempted to claim
412 // all the tasks it possibly can in the sequence. Every thread
413 // claiming tasks must promise call this. Returns true if this
414 // is the last thread to complete so that the thread can perform
415 // cleanup if necessary.
416 bool all_tasks_completed();
417 };
418
419 // Represents a set of free small integer ids.
420 class FreeIdSet : public CHeapObj<mtInternal> {
421 enum {
422 end_of_list = -1,
423 claimed = -2
424 };
425
426 int _sz;
427 Monitor* _mon;
428
429 int* _ids;
430 int _hd;
431 int _waiters;
432 int _claimed;
433
434 static bool _safepoint;
435 typedef FreeIdSet* FreeIdSetPtr;
436 static const int NSets = 10;
437 static FreeIdSetPtr _sets[NSets];
438 static bool _stat_init;
439 int _index;
440
441 public:
442 FreeIdSet(int sz, Monitor* mon);
443 ~FreeIdSet();
444
445 static void set_safepoint(bool b);
446
447 // Attempt to claim the given id permanently. Returns "true" iff
448 // successful.
449 bool claim_perm_id(int i);
450
451 // Returns an unclaimed parallel id (waiting for one to be released if
452 // necessary). Returns "-1" if a GC wakes up a wait for an id.
453 int claim_par_id();
454
455 void release_par_id(int id);
456 };
457
458 #endif // SHARE_VM_GC_SHARED_WORKGROUP_HPP