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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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24
25 #ifndef SHARE_GC_SHARED_WORKGROUP_HPP
26 #define SHARE_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 ThreadClosure;
54 class WorkGang;
55 class GangTaskDispatcher;
56
57 // An abstract task to be worked on by a gang.
58 // You subclass this to supply your own work() method
59 class AbstractGangTask {
60 const char* _name;
61 const uint _gc_id;
62
63 public:
64 explicit AbstractGangTask(const char* name) :
65 _name(name),
66 _gc_id(GCId::current_or_undefined())
67 {}
68
69 // The abstract work method.
70 // The argument tells you which member of the gang you are.
71 virtual void work(uint worker_id) = 0;
72
73 // Debugging accessor for the name.
74 const char* name() const { return _name; }
75 const uint gc_id() const { return _gc_id; }
76 };
77
78 struct WorkData {
79 AbstractGangTask* _task;
80 uint _worker_id;
81 WorkData(AbstractGangTask* task, uint worker_id) : _task(task), _worker_id(worker_id) {}
82 };
83
84 // The work gang is the collection of workers to execute tasks.
85 // The number of workers run for a task is "_active_workers"
86 // while "_total_workers" is the number of available of workers.
87 class AbstractWorkGang : public CHeapObj<mtInternal> {
88 protected:
89 // The array of worker threads for this gang.
90 AbstractGangWorker** _workers;
91 // The count of the number of workers in the gang.
92 uint _total_workers;
93 // The currently active workers in this gang.
94 uint _active_workers;
95 // The count of created workers in the gang.
96 uint _created_workers;
97 // Printing support.
98 const char* _name;
99
100 ~AbstractWorkGang() {}
101
102 private:
103 // Initialize only instance data.
104 const bool _are_GC_task_threads;
105 const bool _are_ConcurrentGC_threads;
106
107 void set_thread(uint worker_id, AbstractGangWorker* worker) {
108 _workers[worker_id] = worker;
109 }
110
111 public:
112 AbstractWorkGang(const char* name, uint workers, bool are_GC_task_threads, bool are_ConcurrentGC_threads) :
113 _workers(NULL),
114 _total_workers(workers),
115 _active_workers(UseDynamicNumberOfGCThreads ? 1U : workers),
116 _created_workers(0),
117 _name(name),
118 _are_GC_task_threads(are_GC_task_threads),
119 _are_ConcurrentGC_threads(are_ConcurrentGC_threads)
120 { }
121
122 // Initialize workers in the gang. Return true if initialization succeeded.
123 void initialize_workers();
124
125 bool are_GC_task_threads() const { return _are_GC_task_threads; }
126 bool are_ConcurrentGC_threads() const { return _are_ConcurrentGC_threads; }
127
128 uint total_workers() const { return _total_workers; }
129
130 uint created_workers() const {
131 return _created_workers;
132 }
133
134 virtual uint active_workers() const {
135 assert(_active_workers <= _total_workers,
136 "_active_workers: %u > _total_workers: %u", _active_workers, _total_workers);
137 return _active_workers;
138 }
139
140 uint update_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 add_workers(false /* exit_on_failure */);
145 assert(v != 0, "Trying to set active workers to 0");
146 log_trace(gc, task)("%s: using %d out of %d workers", name(), _active_workers, _total_workers);
147 return _active_workers;
148 }
149
150 // Add GC workers as needed.
151 void add_workers(bool initializing);
152
153 // Add GC workers as needed to reach the specified number of workers.
154 void add_workers(uint active_workers, bool initializing);
155
156 // Return the Ith worker.
157 AbstractGangWorker* worker(uint i) const;
158
159 // Base name (without worker id #) of threads.
160 const char* group_name() { return name(); }
161
162 void threads_do(ThreadClosure* tc) const;
163
164 // Create a GC worker and install it into the work gang.
165 virtual AbstractGangWorker* install_worker(uint which);
166
167 // Debugging.
168 const char* name() const { return _name; }
169
170 protected:
171 virtual AbstractGangWorker* allocate_worker(uint which) = 0;
172 };
173
174 // An class representing a gang of workers.
175 class WorkGang: public AbstractWorkGang {
176 // To get access to the GangTaskDispatcher instance.
177 friend class GangWorker;
178
179 GangTaskDispatcher* const _dispatcher;
180 GangTaskDispatcher* dispatcher() const {
181 return _dispatcher;
182 }
183
184 public:
185 WorkGang(const char* name,
186 uint workers,
187 bool are_GC_task_threads,
188 bool are_ConcurrentGC_threads);
189
190 ~WorkGang();
191
192 // Run a task using the current active number of workers, returns when the task is done.
193 virtual void run_task(AbstractGangTask* task);
194 // Run a task with the given number of workers, returns
195 // when the task is done. The number of workers must be at most the number of
196 // active workers. Additional workers may be created if an insufficient
197 // number currently exists. If the add_foreground_work flag is true, the current thread
198 // is used to run the task too.
199 void run_task(AbstractGangTask* task, uint num_workers, bool add_foreground_work = false);
200
201 protected:
202 virtual AbstractGangWorker* allocate_worker(uint which);
203 };
204
205 // Temporarily try to set the number of active workers.
206 // It's not guaranteed that it succeeds, and users need to
207 // query the number of active workers.
208 class WithUpdatedActiveWorkers : public StackObj {
209 private:
210 AbstractWorkGang* const _gang;
211 const uint _old_active_workers;
212
213 public:
214 WithUpdatedActiveWorkers(AbstractWorkGang* gang, uint requested_num_workers) :
215 _gang(gang),
216 _old_active_workers(gang->active_workers()) {
217 uint capped_num_workers = MIN2(requested_num_workers, gang->total_workers());
218 gang->update_active_workers(capped_num_workers);
219 }
220
221 ~WithUpdatedActiveWorkers() {
222 _gang->update_active_workers(_old_active_workers);
223 }
224 };
225
226 // Several instances of this class run in parallel as workers for a gang.
227 class AbstractGangWorker: public WorkerThread {
228 public:
229 AbstractGangWorker(AbstractWorkGang* gang, uint id);
230
231 // The only real method: run a task for the gang.
232 virtual void run();
233 // Predicate for Thread
234 virtual bool is_GC_task_thread() const;
235 virtual bool is_ConcurrentGC_thread() const;
236 // Printing
237 void print_on(outputStream* st) const;
238 virtual void print() const;
239
240 protected:
241 AbstractWorkGang* _gang;
242
243 virtual void initialize();
244 virtual void loop() = 0;
245
246 AbstractWorkGang* gang() const { return _gang; }
247 };
248
249 class GangWorker: public AbstractGangWorker {
250 public:
251 GangWorker(WorkGang* gang, uint id) : AbstractGangWorker(gang, id) {}
252
253 protected:
254 virtual void loop();
255
256 private:
257 WorkData wait_for_task();
258 void run_task(WorkData work);
259 void signal_task_done();
260
261 WorkGang* gang() const { return (WorkGang*)_gang; }
262 };
263
264 // A class that acts as a synchronisation barrier. Workers enter
265 // the barrier and must wait until all other workers have entered
266 // before any of them may leave.
267
268 class WorkGangBarrierSync : public StackObj {
269 protected:
270 Monitor _monitor;
271 uint _n_workers;
272 uint _n_completed;
273 bool _should_reset;
274 bool _aborted;
275
276 Monitor* monitor() { return &_monitor; }
277 uint n_workers() { return _n_workers; }
278 uint n_completed() { return _n_completed; }
279 bool should_reset() { return _should_reset; }
280 bool aborted() { return _aborted; }
281
282 void zero_completed() { _n_completed = 0; }
283 void inc_completed() { _n_completed++; }
284 void set_aborted() { _aborted = true; }
285 void set_should_reset(bool v) { _should_reset = v; }
286
287 public:
288 WorkGangBarrierSync();
289 WorkGangBarrierSync(uint n_workers, const char* name);
290
291 // Set the number of workers that will use the barrier.
292 // Must be called before any of the workers start running.
293 void set_n_workers(uint n_workers);
294
295 // Enter the barrier. A worker that enters the barrier will
296 // not be allowed to leave until all other threads have
297 // also entered the barrier or the barrier is aborted.
298 // Returns false if the barrier was aborted.
299 bool enter();
300
301 // Aborts the barrier and wakes up any threads waiting for
302 // the barrier to complete. The barrier will remain in the
303 // aborted state until the next call to set_n_workers().
304 void abort();
305 };
306
307 // A class to manage claiming of subtasks within a group of tasks. The
308 // subtasks will be identified by integer indices, usually elements of an
309 // enumeration type.
310
311 class SubTasksDone: public CHeapObj<mtInternal> {
312 volatile uint* _tasks;
313 uint _n_tasks;
314 volatile uint _threads_completed;
315 #ifdef ASSERT
316 volatile uint _claimed;
317 #endif
318
319 // Set all tasks to unclaimed.
320 void clear();
321
322 NONCOPYABLE(SubTasksDone);
323
324 public:
325 // Initializes "this" to a state in which there are "n" tasks to be
326 // processed, none of the which are originally claimed. The number of
327 // threads doing the tasks is initialized 1.
328 SubTasksDone(uint n);
329
330 // True iff the object is in a valid state.
331 bool valid();
332
333 // Attempt to claim the task "t", returning true if successful,
334 // false if it has already been claimed. The task "t" is required
335 // to be within the range of "this".
336 bool try_claim_task(uint t);
337
338 // The calling thread asserts that it has attempted to claim all the
339 // tasks that it will try to claim. Every thread in the parallel task
340 // must execute this. (When the last thread does so, the task array is
341 // cleared.)
342 //
343 // n_threads - Number of threads executing the sub-tasks.
344 void all_tasks_completed(uint n_threads);
345
346 // Destructor.
347 ~SubTasksDone();
348 };
349
350 // As above, but for sequential tasks, i.e. instead of claiming
351 // sub-tasks from a set (possibly an enumeration), claim sub-tasks
352 // in sequential order. This is ideal for claiming dynamically
353 // partitioned tasks (like striding in the parallel remembered
354 // set scanning). Note that unlike the above class this is
355 // a stack object - is there any reason for it not to be?
356
357 class SequentialSubTasksDone : public StackObj {
358 protected:
359 uint _n_tasks; // Total number of tasks available.
360 volatile uint _n_claimed; // Number of tasks claimed.
361 // _n_threads is used to determine when a sub task is done.
362 // See comments on SubTasksDone::_n_threads
363 uint _n_threads; // Total number of parallel threads.
364 volatile uint _n_completed; // Number of completed threads.
365
366 void clear();
367
368 public:
369 SequentialSubTasksDone() {
370 clear();
371 }
372 ~SequentialSubTasksDone() {}
373
374 // True iff the object is in a valid state.
375 bool valid();
376
377 // number of tasks
378 uint n_tasks() const { return _n_tasks; }
379
380 // Get/set the number of parallel threads doing the tasks to t.
381 // Should be called before the task starts but it is safe
382 // to call this once a task is running provided that all
383 // threads agree on the number of threads.
384 uint n_threads() { return _n_threads; }
385 void set_n_threads(uint t) { _n_threads = t; }
386
387 // Set the number of tasks to be claimed to t. As above,
388 // should be called before the tasks start but it is safe
389 // to call this once a task is running provided all threads
390 // agree on the number of tasks.
391 void set_n_tasks(uint t) { _n_tasks = t; }
392
393 // Attempt to claim the next unclaimed task in the sequence,
394 // returning true if successful, with t set to the index of the
395 // claimed task. Returns false if there are no more unclaimed tasks
396 // in the sequence.
397 bool try_claim_task(uint& t);
398
399 // The calling thread asserts that it has attempted to claim
400 // all the tasks it possibly can in the sequence. Every thread
401 // claiming tasks must promise call this. Returns true if this
402 // is the last thread to complete so that the thread can perform
403 // cleanup if necessary.
404 bool all_tasks_completed();
405 };
406
407 #endif // SHARE_GC_SHARED_WORKGROUP_HPP