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
187 // Run a task, returns when the task is done.
188 virtual void run_task(AbstractGangTask* task);
189
190 protected:
191 virtual AbstractGangWorker* allocate_worker(uint which);
192 };
193
194 // Several instances of this class run in parallel as workers for a gang.
195 class AbstractGangWorker: public WorkerThread {
196 public:
197 AbstractGangWorker(AbstractWorkGang* gang, uint id);
198
199 // The only real method: run a task for the gang.
200 virtual void run();
201 // Predicate for Thread
202 virtual bool is_GC_task_thread() const;
203 virtual bool is_ConcurrentGC_thread() const;
204 // Printing
205 void print_on(outputStream* st) const;
206 virtual void print() const { print_on(tty); }
207
208 protected:
209 AbstractWorkGang* _gang;
210
211 virtual void initialize();
212 virtual void loop() = 0;
213
214 AbstractWorkGang* gang() const { return _gang; }
215 };
216
217 class GangWorker: public AbstractGangWorker {
218 public:
219 GangWorker(WorkGang* gang, uint id) : AbstractGangWorker(gang, id) {}
220
221 protected:
222 virtual void loop();
223
224 private:
225 WorkData wait_for_task();
226 void run_task(WorkData work);
227 void signal_task_done();
228
229 void print_task_started(WorkData data);
230 void print_task_done(WorkData data);
231
232 WorkGang* gang() const { return (WorkGang*)_gang; }
233 };
234
235 // A class that acts as a synchronisation barrier. Workers enter
236 // the barrier and must wait until all other workers have entered
237 // before any of them may leave.
238
239 class WorkGangBarrierSync : public StackObj {
240 protected:
241 Monitor _monitor;
242 uint _n_workers;
243 uint _n_completed;
244 bool _should_reset;
245 bool _aborted;
246
247 Monitor* monitor() { return &_monitor; }
248 uint n_workers() { return _n_workers; }
249 uint n_completed() { return _n_completed; }
250 bool should_reset() { return _should_reset; }
251 bool aborted() { return _aborted; }
252
253 void zero_completed() { _n_completed = 0; }
254 void inc_completed() { _n_completed++; }
255 void set_aborted() { _aborted = true; }
256 void set_should_reset(bool v) { _should_reset = v; }
257
258 public:
259 WorkGangBarrierSync();
260 WorkGangBarrierSync(uint n_workers, const char* name);
261
262 // Set the number of workers that will use the barrier.
263 // Must be called before any of the workers start running.
264 void set_n_workers(uint n_workers);
265
266 // Enter the barrier. A worker that enters the barrier will
267 // not be allowed to leave until all other threads have
268 // also entered the barrier or the barrier is aborted.
269 // Returns false if the barrier was aborted.
270 bool enter();
271
272 // Aborts the barrier and wakes up any threads waiting for
273 // the barrier to complete. The barrier will remain in the
274 // aborted state until the next call to set_n_workers().
275 void abort();
276 };
277
278 // A class to manage claiming of subtasks within a group of tasks. The
279 // subtasks will be identified by integer indices, usually elements of an
280 // enumeration type.
281
282 class SubTasksDone: public CHeapObj<mtInternal> {
283 uint* _tasks;
284 uint _n_tasks;
285 uint _threads_completed;
286 #ifdef ASSERT
287 volatile uint _claimed;
288 #endif
289
290 // Set all tasks to unclaimed.
291 void clear();
292
293 public:
294 // Initializes "this" to a state in which there are "n" tasks to be
295 // processed, none of the which are originally claimed. The number of
296 // threads doing the tasks is initialized 1.
297 SubTasksDone(uint n);
298
299 // True iff the object is in a valid state.
300 bool valid();
301
302 // Returns "false" if the task "t" is unclaimed, and ensures that task is
303 // claimed. The task "t" is required to be within the range of "this".
304 bool is_task_claimed(uint t);
305
306 // The calling thread asserts that it has attempted to claim all the
307 // tasks that it will try to claim. Every thread in the parallel task
308 // must execute this. (When the last thread does so, the task array is
309 // cleared.)
310 //
311 // n_threads - Number of threads executing the sub-tasks.
312 void all_tasks_completed(uint n_threads);
313
314 // Destructor.
315 ~SubTasksDone();
316 };
317
318 // As above, but for sequential tasks, i.e. instead of claiming
319 // sub-tasks from a set (possibly an enumeration), claim sub-tasks
320 // in sequential order. This is ideal for claiming dynamically
321 // partitioned tasks (like striding in the parallel remembered
322 // set scanning). Note that unlike the above class this is
323 // a stack object - is there any reason for it not to be?
324
325 class SequentialSubTasksDone : public StackObj {
326 protected:
327 uint _n_tasks; // Total number of tasks available.
328 uint _n_claimed; // Number of tasks claimed.
329 // _n_threads is used to determine when a sub task is done.
330 // See comments on SubTasksDone::_n_threads
331 uint _n_threads; // Total number of parallel threads.
332 uint _n_completed; // Number of completed threads.
333
334 void clear();
335
336 public:
337 SequentialSubTasksDone() {
338 clear();
339 }
340 ~SequentialSubTasksDone() {}
341
342 // True iff the object is in a valid state.
343 bool valid();
344
345 // number of tasks
346 uint n_tasks() const { return _n_tasks; }
347
348 // Get/set the number of parallel threads doing the tasks to t.
349 // Should be called before the task starts but it is safe
350 // to call this once a task is running provided that all
351 // threads agree on the number of threads.
352 uint n_threads() { return _n_threads; }
353 void set_n_threads(uint t) { _n_threads = t; }
354
355 // Set the number of tasks to be claimed to t. As above,
356 // should be called before the tasks start but it is safe
357 // to call this once a task is running provided all threads
358 // agree on the number of tasks.
359 void set_n_tasks(uint t) { _n_tasks = t; }
360
361 // Returns false if the next task in the sequence is unclaimed,
362 // and ensures that it is claimed. Will set t to be the index
363 // of the claimed task in the sequence. Will return true if
364 // the task cannot be claimed and there are none left to claim.
365 bool is_task_claimed(uint& t);
366
367 // The calling thread asserts that it has attempted to claim
368 // all the tasks it possibly can in the sequence. Every thread
369 // claiming tasks must promise call this. Returns true if this
370 // is the last thread to complete so that the thread can perform
371 // cleanup if necessary.
372 bool all_tasks_completed();
373 };
374
375 // Represents a set of free small integer ids.
376 class FreeIdSet : public CHeapObj<mtInternal> {
377 enum {
378 end_of_list = -1,
379 claimed = -2
380 };
381
382 int _sz;
383 Monitor* _mon;
384
385 int* _ids;
386 int _hd;
387 int _waiters;
388 int _claimed;
389
390 static bool _safepoint;
391 typedef FreeIdSet* FreeIdSetPtr;
392 static const int NSets = 10;
393 static FreeIdSetPtr _sets[NSets];
394 static bool _stat_init;
395 int _index;
396
397 public:
398 FreeIdSet(int sz, Monitor* mon);
399 ~FreeIdSet();
400
401 static void set_safepoint(bool b);
402
403 // Attempt to claim the given id permanently. Returns "true" iff
404 // successful.
405 bool claim_perm_id(int i);
406
407 // Returns an unclaimed parallel id (waiting for one to be released if
408 // necessary). Returns "-1" if a GC wakes up a wait for an id.
409 int claim_par_id();
410
411 void release_par_id(int id);
412 };
413
414 #endif // SHARE_VM_GC_SHARED_WORKGROUP_HPP