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 "gc/shared/taskqueue.hpp"
29 #include "runtime/thread.inline.hpp"
30
31 // Task class hierarchy:
32 // AbstractGangTask
33 // AbstractGangTaskWOopQueues
34 //
35 // Gang/Group class hierarchy:
36 // AbstractWorkGang
37 // WorkGang
38 // FlexibleWorkGang
39 // YieldingFlexibleWorkGang (defined in another file)
40 //
41 // Worker class hierarchy:
42 // GangWorker (subclass of WorkerThread)
43 // YieldingFlexibleGangWorker (defined in another file)
44
45 // Forward declarations of classes defined here
46
47 class WorkGang;
48 class GangWorker;
49 class YieldingFlexibleGangWorker;
50 class YieldingFlexibleGangTask;
51 class WorkData;
52 class AbstractWorkGang;
53
54 // An abstract task to be worked on by a gang.
55 // You subclass this to supply your own work() method
56 class AbstractGangTask VALUE_OBJ_CLASS_SPEC {
57 public:
58 // The abstract work method.
59 // The argument tells you which member of the gang you are.
60 virtual void work(uint worker_id) = 0;
61
62 // Debugging accessor for the name.
63 const char* name() const PRODUCT_RETURN_(return NULL;);
64 int counter() { return _counter; }
65 void set_counter(int value) { _counter = value; }
66 int *address_of_counter() { return &_counter; }
67
68 // RTTI
69 NOT_PRODUCT(virtual bool is_YieldingFlexibleGang_task() const {
70 return false;
71 })
72
73 private:
74 NOT_PRODUCT(const char* _name;)
75 // ??? Should a task have a priority associated with it?
76 // ??? Or can the run method adjust priority as needed?
77 int _counter;
78
79 protected:
80 // Constructor and desctructor: only construct subclasses.
81 AbstractGangTask(const char* name)
82 {
83 NOT_PRODUCT(_name = name);
84 _counter = 0;
85 }
86 ~AbstractGangTask() { }
87
88 public:
89 };
90
91 class AbstractGangTaskWOopQueues : public AbstractGangTask {
92 OopTaskQueueSet* _queues;
93 ParallelTaskTerminator _terminator;
94 public:
95 AbstractGangTaskWOopQueues(const char* name, OopTaskQueueSet* queues, uint n_threads) :
96 AbstractGangTask(name), _queues(queues), _terminator(n_threads, _queues) {}
97 ParallelTaskTerminator* terminator() { return &_terminator; }
98 OopTaskQueueSet* queues() { return _queues; }
99 };
100
101
102 // Class AbstractWorkGang:
103 // An abstract class representing a gang of workers.
104 // You subclass this to supply an implementation of run_task().
105 class AbstractWorkGang: public CHeapObj<mtInternal> {
106 protected:
107 // Work gangs are never deleted, so no need to cleanup.
108 ~AbstractWorkGang() { ShouldNotReachHere(); }
109 public:
110 // Constructor.
111 AbstractWorkGang(const char* name, bool are_GC_task_threads,
112 bool are_ConcurrentGC_threads);
113 // Run a task, returns when the task is done (or terminated).
114 virtual void run_task(AbstractGangTask* task) = 0;
115 // Return true if more workers should be applied to the task.
116 virtual bool needs_more_workers() const { return true; }
117 public:
118 // Debugging.
119 const char* name() const;
120 protected:
121 // Initialize only instance data.
122 const bool _are_GC_task_threads;
123 const bool _are_ConcurrentGC_threads;
124 // Printing support.
125 const char* _name;
126 // The monitor which protects these data,
127 // and notifies of changes in it.
128 Monitor* _monitor;
129 // The count of the number of workers in the gang.
130 uint _total_workers;
131 // The array of worker threads for this gang.
132 // This is only needed for cleaning up.
133 GangWorker** _gang_workers;
134 // The task for this gang.
135 AbstractGangTask* _task;
136 // A sequence number for the current task.
137 int _sequence_number;
138 // The number of started workers.
139 uint _started_workers;
140 // The number of finished workers.
141 uint _finished_workers;
142 public:
143 // Accessors for fields
144 Monitor* monitor() const {
145 return _monitor;
146 }
147 uint total_workers() const {
148 return _total_workers;
149 }
150 virtual uint active_workers() const {
151 return _total_workers;
152 }
153 GangWorker** gang_workers() const {
154 return _gang_workers;
155 }
156 AbstractGangTask* task() const {
157 return _task;
158 }
159 int sequence_number() const {
160 return _sequence_number;
161 }
162 uint started_workers() const {
163 return _started_workers;
164 }
165 uint finished_workers() const {
166 return _finished_workers;
167 }
168 bool are_GC_task_threads() const {
169 return _are_GC_task_threads;
170 }
171 bool are_ConcurrentGC_threads() const {
172 return _are_ConcurrentGC_threads;
173 }
174 // Predicates.
175 bool is_idle() const {
176 return (task() == NULL);
177 }
178 // Return the Ith gang worker.
179 GangWorker* gang_worker(uint i) const;
180
181 void threads_do(ThreadClosure* tc) const;
182
183 // Printing
184 void print_worker_threads_on(outputStream *st) const;
185 void print_worker_threads() const {
186 print_worker_threads_on(tty);
187 }
188
189 protected:
190 friend class GangWorker;
191 friend class YieldingFlexibleGangWorker;
192 // Note activation and deactivation of workers.
193 // These methods should only be called with the mutex held.
194 void internal_worker_poll(WorkData* data) const;
195 void internal_note_start();
196 void internal_note_finish();
197 };
198
199 class WorkData: public StackObj {
200 // This would be a struct, but I want accessor methods.
201 private:
202 AbstractGangTask* _task;
203 int _sequence_number;
204 public:
205 // Constructor and destructor
206 WorkData() {
207 _task = NULL;
208 _sequence_number = 0;
209 }
210 ~WorkData() {
211 }
212 AbstractGangTask* task() const { return _task; }
213 void set_task(AbstractGangTask* value) { _task = value; }
214 int sequence_number() const { return _sequence_number; }
215 void set_sequence_number(int value) { _sequence_number = value; }
216
217 YieldingFlexibleGangTask* yf_task() const {
218 return (YieldingFlexibleGangTask*)_task;
219 }
220 };
221
222 // Class WorkGang:
223 class WorkGang: public AbstractWorkGang {
224 public:
225 // Constructor
226 WorkGang(const char* name, uint workers,
227 bool are_GC_task_threads, bool are_ConcurrentGC_threads);
228 // Run a task, returns when the task is done (or terminated).
229 virtual void run_task(AbstractGangTask* task);
230 void run_task(AbstractGangTask* task, uint no_of_parallel_workers);
231 // Allocate a worker and return a pointer to it.
232 virtual GangWorker* allocate_worker(uint which);
233 // Initialize workers in the gang. Return true if initialization
234 // succeeded. The type of the worker can be overridden in a derived
235 // class with the appropriate implementation of allocate_worker().
236 bool initialize_workers();
237 };
238
239 // Class GangWorker:
240 // Several instances of this class run in parallel as workers for a gang.
241 class GangWorker: public WorkerThread {
242 public:
243 // Constructors and destructor.
244 GangWorker(AbstractWorkGang* gang, uint id);
245
246 // The only real method: run a task for the gang.
247 virtual void run();
248 // Predicate for Thread
249 virtual bool is_GC_task_thread() const;
250 virtual bool is_ConcurrentGC_thread() const;
251 // Printing
252 void print_on(outputStream* st) const;
253 virtual void print() const { print_on(tty); }
254 protected:
255 AbstractWorkGang* _gang;
256
257 virtual void initialize();
258 virtual void loop();
259
260 public:
261 AbstractWorkGang* gang() const { return _gang; }
262 };
263
264 // Dynamic number of worker threads
265 //
266 // This type of work gang is used to run different numbers of
267 // worker threads at different times. The
268 // number of workers run for a task is "_active_workers"
269 // instead of "_total_workers" in a WorkGang. The method
270 // "needs_more_workers()" returns true until "_active_workers"
271 // have been started and returns false afterwards. The
272 // implementation of "needs_more_workers()" in WorkGang always
273 // returns true so that all workers are started. The method
274 // "loop()" in GangWorker was modified to ask "needs_more_workers()"
275 // in its loop to decide if it should start working on a task.
276 // A worker in "loop()" waits for notification on the WorkGang
277 // monitor and execution of each worker as it checks for work
278 // is serialized via the same monitor. The "needs_more_workers()"
279 // call is serialized and additionally the calculation for the
280 // "part" (effectively the worker id for executing the task) is
281 // serialized to give each worker a unique "part". Workers that
282 // are not needed for this tasks (i.e., "_active_workers" have
283 // been started before it, continue to wait for work.
284
285 class FlexibleWorkGang: public WorkGang {
286 // The currently active workers in this gang.
287 // This is a number that is dynamically adjusted
288 // and checked in the run_task() method at each invocation.
289 // As described above _active_workers determines the number
290 // of threads started on a task. It must also be used to
291 // determine completion.
292
293 protected:
294 uint _active_workers;
295 public:
296 // Constructor and destructor.
297 FlexibleWorkGang(const char* name, uint workers,
298 bool are_GC_task_threads,
299 bool are_ConcurrentGC_threads) :
300 WorkGang(name, workers, are_GC_task_threads, are_ConcurrentGC_threads),
301 _active_workers(UseDynamicNumberOfGCThreads ? 1U : workers) {}
302
303 // Accessors for fields.
304 virtual uint active_workers() const {
305 assert(_active_workers <= _total_workers,
306 err_msg("_active_workers: %u > _total_workers: %u", _active_workers, _total_workers));
307 assert(UseDynamicNumberOfGCThreads || _active_workers == _total_workers,
308 "Unless dynamic should use total workers");
309 return _active_workers;
310 }
311 void set_active_workers(uint v) {
312 assert(v <= _total_workers,
313 "Trying to set more workers active than there are");
314 _active_workers = MIN2(v, _total_workers);
315 assert(v != 0, "Trying to set active workers to 0");
316 _active_workers = MAX2(1U, _active_workers);
317 assert(UseDynamicNumberOfGCThreads || _active_workers == _total_workers,
318 "Unless dynamic should use total workers");
319 }
320 virtual void run_task(AbstractGangTask* task);
321 virtual bool needs_more_workers() const {
322 return _started_workers < _active_workers;
323 }
324 };
325
326 // A class that acts as a synchronisation barrier. Workers enter
327 // the barrier and must wait until all other workers have entered
328 // before any of them may leave.
329
330 class WorkGangBarrierSync : public StackObj {
331 protected:
332 Monitor _monitor;
333 uint _n_workers;
334 uint _n_completed;
335 bool _should_reset;
336 bool _aborted;
337
338 Monitor* monitor() { return &_monitor; }
339 uint n_workers() { return _n_workers; }
340 uint n_completed() { return _n_completed; }
341 bool should_reset() { return _should_reset; }
342 bool aborted() { return _aborted; }
343
344 void zero_completed() { _n_completed = 0; }
345 void inc_completed() { _n_completed++; }
346 void set_aborted() { _aborted = true; }
347 void set_should_reset(bool v) { _should_reset = v; }
348
349 public:
350 WorkGangBarrierSync();
351 WorkGangBarrierSync(uint n_workers, const char* name);
352
353 // Set the number of workers that will use the barrier.
354 // Must be called before any of the workers start running.
355 void set_n_workers(uint n_workers);
356
357 // Enter the barrier. A worker that enters the barrier will
358 // not be allowed to leave until all other threads have
359 // also entered the barrier or the barrier is aborted.
360 // Returns false if the barrier was aborted.
361 bool enter();
362
363 // Aborts the barrier and wakes up any threads waiting for
364 // the barrier to complete. The barrier will remain in the
365 // aborted state until the next call to set_n_workers().
366 void abort();
367 };
368
369 // A class to manage claiming of subtasks within a group of tasks. The
370 // subtasks will be identified by integer indices, usually elements of an
371 // enumeration type.
372
373 class SubTasksDone: public CHeapObj<mtInternal> {
374 uint* _tasks;
375 uint _n_tasks;
376 uint _threads_completed;
377 #ifdef ASSERT
378 volatile uint _claimed;
379 #endif
380
381 // Set all tasks to unclaimed.
382 void clear();
383
384 public:
385 // Initializes "this" to a state in which there are "n" tasks to be
386 // processed, none of the which are originally claimed. The number of
387 // threads doing the tasks is initialized 1.
388 SubTasksDone(uint n);
389
390 // True iff the object is in a valid state.
391 bool valid();
392
393 // Returns "false" if the task "t" is unclaimed, and ensures that task is
394 // claimed. The task "t" is required to be within the range of "this".
395 bool is_task_claimed(uint t);
396
397 // The calling thread asserts that it has attempted to claim all the
398 // tasks that it will try to claim. Every thread in the parallel task
399 // must execute this. (When the last thread does so, the task array is
400 // cleared.)
401 //
402 // n_threads - Number of threads executing the sub-tasks.
403 void all_tasks_completed(uint n_threads);
404
405 // Destructor.
406 ~SubTasksDone();
407 };
408
409 // As above, but for sequential tasks, i.e. instead of claiming
410 // sub-tasks from a set (possibly an enumeration), claim sub-tasks
411 // in sequential order. This is ideal for claiming dynamically
412 // partitioned tasks (like striding in the parallel remembered
413 // set scanning). Note that unlike the above class this is
414 // a stack object - is there any reason for it not to be?
415
416 class SequentialSubTasksDone : public StackObj {
417 protected:
418 uint _n_tasks; // Total number of tasks available.
419 uint _n_claimed; // Number of tasks claimed.
420 // _n_threads is used to determine when a sub task is done.
421 // See comments on SubTasksDone::_n_threads
422 uint _n_threads; // Total number of parallel threads.
423 uint _n_completed; // Number of completed threads.
424
425 void clear();
426
427 public:
428 SequentialSubTasksDone() {
429 clear();
430 }
431 ~SequentialSubTasksDone() {}
432
433 // True iff the object is in a valid state.
434 bool valid();
435
436 // number of tasks
437 uint n_tasks() const { return _n_tasks; }
438
439 // Get/set the number of parallel threads doing the tasks to t.
440 // Should be called before the task starts but it is safe
441 // to call this once a task is running provided that all
442 // threads agree on the number of threads.
443 uint n_threads() { return _n_threads; }
444 void set_n_threads(uint t) { _n_threads = t; }
445
446 // Set the number of tasks to be claimed to t. As above,
447 // should be called before the tasks start but it is safe
448 // to call this once a task is running provided all threads
449 // agree on the number of tasks.
450 void set_n_tasks(uint t) { _n_tasks = t; }
451
452 // Returns false if the next task in the sequence is unclaimed,
453 // and ensures that it is claimed. Will set t to be the index
454 // of the claimed task in the sequence. Will return true if
455 // the task cannot be claimed and there are none left to claim.
456 bool is_task_claimed(uint& t);
457
458 // The calling thread asserts that it has attempted to claim
459 // all the tasks it possibly can in the sequence. Every thread
460 // claiming tasks must promise call this. Returns true if this
461 // is the last thread to complete so that the thread can perform
462 // cleanup if necessary.
463 bool all_tasks_completed();
464 };
465
466 // Represents a set of free small integer ids.
467 class FreeIdSet : public CHeapObj<mtInternal> {
468 enum {
469 end_of_list = -1,
470 claimed = -2
471 };
472
473 int _sz;
474 Monitor* _mon;
475
476 int* _ids;
477 int _hd;
478 int _waiters;
479 int _claimed;
480
481 static bool _safepoint;
482 typedef FreeIdSet* FreeIdSetPtr;
483 static const int NSets = 10;
484 static FreeIdSetPtr _sets[NSets];
485 static bool _stat_init;
486 int _index;
487
488 public:
489 FreeIdSet(int sz, Monitor* mon);
490 ~FreeIdSet();
491
492 static void set_safepoint(bool b);
493
494 // Attempt to claim the given id permanently. Returns "true" iff
495 // successful.
496 bool claim_perm_id(int i);
497
498 // Returns an unclaimed parallel id (waiting for one to be released if
499 // necessary). Returns "-1" if a GC wakes up a wait for an id.
500 int claim_par_id();
501
502 void release_par_id(int id);
503 };
504
505 #endif // SHARE_VM_GC_SHARED_WORKGROUP_HPP