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 "utilities/debug.hpp"
32 #include "utilities/globalDefinitions.hpp"
33
34 // Task class hierarchy:
35 // AbstractGangTask
36 //
37 // Gang/Group class hierarchy:
38 // AbstractWorkGang
39 // WorkGang
40 // YieldingFlexibleWorkGang (defined in another file)
41 //
42 // Worker class hierarchy:
43 // AbstractGangWorker (subclass of WorkerThread)
44 // GangWorker
45 // YieldingFlexibleGangWorker (defined in another file)
46
47 // Forward declarations of classes defined here
48
49 class AbstractGangWorker;
50 class Semaphore;
51 class WorkGang;
52
53 // An abstract task to be worked on by a gang.
54 // You subclass this to supply your own work() method
55 class AbstractGangTask VALUE_OBJ_CLASS_SPEC {
56 const char* _name;
57
58 public:
59 AbstractGangTask(const char* name) : _name(name) {}
60
61 // The abstract work method.
62 // The argument tells you which member of the gang you are.
63 virtual void work(uint worker_id) = 0;
64
65 // Debugging accessor for the name.
66 const char* name() const { return _name; }
67 };
68
69 struct WorkData {
70 AbstractGangTask* _task;
71 uint _worker_id;
72 WorkData(AbstractGangTask* task, uint worker_id) : _task(task), _worker_id(worker_id) {}
73 };
74
75 // Interface to handle the synchronization between the coordinator thread and the worker threads,
76 // when a task is dispatched out to the worker threads.
77 class GangTaskDispatcher : public CHeapObj<mtGC> {
78 public:
79 virtual ~GangTaskDispatcher() {}
80
81 // Coordinator API.
82
83 // Distributes the task out to num_workers workers.
84 // Returns when the task has been completed by all workers.
85 virtual void coordinator_execute_on_workers(AbstractGangTask* task, uint num_workers) = 0;
86
87 // Worker API.
88
89 // Waits for a task to become available to the worker.
90 // Returns when the worker has been assigned a task.
91 virtual WorkData worker_wait_for_task() = 0;
92
93 // Signal to the coordinator that the worker is done with the assigned task.
94 virtual void worker_done_with_task() = 0;
95 };
96
97 // The work gang is the collection of workers to execute tasks.
98 // The number of workers run for a task is "_active_workers"
99 // while "_total_workers" is the number of available of workers.
100 class AbstractWorkGang : public CHeapObj<mtInternal> {
101 protected:
102 // The array of worker threads for this gang.
103 AbstractGangWorker** _workers;
104 // The count of the number of workers in the gang.
105 uint _total_workers;
106 // The currently active workers in this gang.
107 uint _active_workers;
108 // Printing support.
109 const char* _name;
110
111 private:
112 // Initialize only instance data.
113 const bool _are_GC_task_threads;
114 const bool _are_ConcurrentGC_threads;
115
116 public:
117 AbstractWorkGang(const char* name, uint workers, bool are_GC_task_threads, bool are_ConcurrentGC_threads) :
118 _name(name),
119 _total_workers(workers),
120 _active_workers(UseDynamicNumberOfGCThreads ? 1U : workers),
121 _are_GC_task_threads(are_GC_task_threads),
122 _are_ConcurrentGC_threads(are_ConcurrentGC_threads)
123 { }
124
125 // Initialize workers in the gang. Return true if initialization succeeded.
126 bool initialize_workers();
127
128 bool are_GC_task_threads() const { return _are_GC_task_threads; }
129 bool are_ConcurrentGC_threads() const { return _are_ConcurrentGC_threads; }
130
131 uint total_workers() const { return _total_workers; }
132
133 virtual uint active_workers() const {
134 assert(_active_workers <= _total_workers,
135 err_msg("_active_workers: %u > _total_workers: %u", _active_workers, _total_workers));
136 assert(UseDynamicNumberOfGCThreads || _active_workers == _total_workers,
137 "Unless dynamic should use total workers");
138 return _active_workers;
139 }
140 void set_active_workers(uint v) {
141 assert(v <= _total_workers,
142 "Trying to set more workers active than there are");
143 _active_workers = MIN2(v, _total_workers);
144 assert(v != 0, "Trying to set active workers to 0");
145 _active_workers = MAX2(1U, _active_workers);
146 assert(UseDynamicNumberOfGCThreads || _active_workers == _total_workers,
147 "Unless dynamic should use total workers");
148 }
149
150 // Return the Ith worker.
151 AbstractGangWorker* worker(uint i) const;
152
153 void threads_do(ThreadClosure* tc) const;
154
155 // Debugging.
156 const char* name() const { return _name; }
157
158 // Printing
159 void print_worker_threads_on(outputStream *st) const;
160 void print_worker_threads() const {
161 print_worker_threads_on(tty);
162 }
163
164 protected:
165 virtual AbstractGangWorker* allocate_worker(uint which) = 0;
166 };
167
168 // An class representing a gang of workers.
169 class WorkGang: public AbstractWorkGang {
170 // To get access to the GangTaskDispatcher instance.
171 friend class GangWorker;
172
173 // Never deleted.
174 ~WorkGang();
175
176 GangTaskDispatcher* const _dispatcher;
177 GangTaskDispatcher* dispatcher()const {
178 return _dispatcher;
179 }
180
181 public:
182 WorkGang(const char* name,
183 uint workers,
184 bool are_GC_task_threads,
185 bool are_ConcurrentGC_threads,
186 GangTaskDispatcher* dispatcher = NULL);
187
188 // Run a task, returns when the task is done.
189 virtual void run_task(AbstractGangTask* task);
190
191 protected:
192 virtual AbstractGangWorker* allocate_worker(uint which);
193
194 private:
195 void print_worker_started_task(AbstractGangTask* task, uint worker_id);
196 void print_worker_finished_task(AbstractGangTask* task, uint worker_id);
197 };
198
199 // Several instances of this class run in parallel as workers for a gang.
200 class AbstractGangWorker: public WorkerThread {
201 public:
202 AbstractGangWorker(AbstractWorkGang* gang, uint id);
203
204 // The only real method: run a task for the gang.
205 virtual void run();
206 // Predicate for Thread
207 virtual bool is_GC_task_thread() const;
208 virtual bool is_ConcurrentGC_thread() const;
209 // Printing
210 void print_on(outputStream* st) const;
211 virtual void print() const { print_on(tty); }
212
213 protected:
214 AbstractWorkGang* _gang;
215
216 virtual void initialize();
217 virtual void loop() = 0;
218
219 AbstractWorkGang* gang() const { return _gang; }
220 };
221
222 class GangWorker: public AbstractGangWorker {
223 public:
224 GangWorker(WorkGang* gang, uint id) : AbstractGangWorker(gang, id) {}
225
226 protected:
227 virtual void loop();
228
229 private:
230 WorkData wait_for_task();
231 void run_task(WorkData work);
232 void signal_task_done();
233
234 void print_task_started(WorkData data);
235 void print_task_done(WorkData data);
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 // Represents a set of free small integer ids.
381 class FreeIdSet : public CHeapObj<mtInternal> {
382 enum {
383 end_of_list = -1,
384 claimed = -2
385 };
386
387 int _sz;
388 Monitor* _mon;
389
390 int* _ids;
391 int _hd;
392 int _waiters;
393 int _claimed;
394
395 static bool _safepoint;
396 typedef FreeIdSet* FreeIdSetPtr;
397 static const int NSets = 10;
398 static FreeIdSetPtr _sets[NSets];
399 static bool _stat_init;
400 int _index;
401
402 public:
403 FreeIdSet(int sz, Monitor* mon);
404 ~FreeIdSet();
405
406 static void set_safepoint(bool b);
407
408 // Attempt to claim the given id permanently. Returns "true" iff
409 // successful.
410 bool claim_perm_id(int i);
411
412 // Returns an unclaimed parallel id (waiting for one to be released if
413 // necessary). Returns "-1" if a GC wakes up a wait for an id.
414 int claim_par_id();
415
416 void release_par_id(int id);
417 };
418
419 #endif // SHARE_VM_GC_SHARED_WORKGROUP_HPP