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 "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 WorkGang;
54
55 // An abstract task to be worked on by a gang.
56 // You subclass this to supply your own work() method
57 class AbstractGangTask {
58 const char* _name;
59 const uint _gc_id;
60
61 public:
62 explicit AbstractGangTask(const char* name) :
63 _name(name),
64 _gc_id(GCId::current_or_undefined())
65 {}
66
67 // The abstract work method.
68 // The argument tells you which member of the gang you are.
69 virtual void work(uint worker_id) = 0;
70
71 // Debugging accessor for the name.
72 const char* name() const { return _name; }
73 const uint gc_id() const { return _gc_id; }
74 };
75
76 struct WorkData {
77 AbstractGangTask* _task;
78 uint _worker_id;
79 WorkData(AbstractGangTask* task, uint worker_id) : _task(task), _worker_id(worker_id) {}
80 };
81
82 // Interface to handle the synchronization between the coordinator thread and the worker threads,
83 // when a task is dispatched out to the worker threads.
84 class GangTaskDispatcher : public CHeapObj<mtGC> {
85 public:
86 virtual ~GangTaskDispatcher() {}
87
88 // Coordinator API.
89
90 // Distributes the task out to num_workers workers.
91 // Returns when the task has been completed by all workers.
92 virtual void coordinator_execute_on_workers(AbstractGangTask* task, uint num_workers) = 0;
93
94 // Worker API.
95
96 // Waits for a task to become available to the worker.
97 // Returns when the worker has been assigned a task.
98 virtual WorkData worker_wait_for_task() = 0;
99
100 // Signal to the coordinator that the worker is done with the assigned task.
101 virtual void worker_done_with_task() = 0;
102 };
103
104 // The work gang is the collection of workers to execute tasks.
105 // The number of workers run for a task is "_active_workers"
106 // while "_total_workers" is the number of available of workers.
107 class AbstractWorkGang : public CHeapObj<mtInternal> {
108 protected:
109 // The array of worker threads for this gang.
110 AbstractGangWorker** _workers;
111 // The count of the number of workers in the gang.
112 uint _total_workers;
113 // The currently active workers in this gang.
114 uint _active_workers;
115 // The count of created workers in the gang.
116 uint _created_workers;
117 // Printing support.
118 const char* _name;
119
120 ~AbstractWorkGang() {}
121
122 private:
123 // Initialize only instance data.
124 const bool _are_GC_task_threads;
125 const bool _are_ConcurrentGC_threads;
126
127 void set_thread(uint worker_id, AbstractGangWorker* worker) {
128 _workers[worker_id] = worker;
129 }
130
131 public:
132 AbstractWorkGang(const char* name, uint workers, bool are_GC_task_threads, bool are_ConcurrentGC_threads) :
133 _name(name),
134 _total_workers(workers),
135 _active_workers(UseDynamicNumberOfGCThreads ? 1U : workers),
136 _created_workers(0),
137 _are_GC_task_threads(are_GC_task_threads),
138 _are_ConcurrentGC_threads(are_ConcurrentGC_threads)
139 { }
140
141 // Initialize workers in the gang. Return true if initialization succeeded.
142 void initialize_workers();
143
144 bool are_GC_task_threads() const { return _are_GC_task_threads; }
145 bool are_ConcurrentGC_threads() const { return _are_ConcurrentGC_threads; }
146
147 uint total_workers() const { return _total_workers; }
148
149 uint created_workers() const {
150 return _created_workers;
151 }
152
153 virtual uint active_workers() const {
154 assert(_active_workers <= _total_workers,
155 "_active_workers: %u > _total_workers: %u", _active_workers, _total_workers);
156 assert(UseDynamicNumberOfGCThreads || _active_workers == _total_workers,
157 "Unless dynamic should use total workers");
158 return _active_workers;
159 }
160
161 uint update_active_workers(uint v) {
162 assert(v <= _total_workers,
163 "Trying to set more workers active than there are");
164 _active_workers = MIN2(v, _total_workers);
165 add_workers(false /* exit_on_failure */);
166 assert(v != 0, "Trying to set active workers to 0");
167 log_trace(gc, task)("%s: using %d out of %d workers", name(), _active_workers, _total_workers);
168 return _active_workers;
169 }
170
171 // Add GC workers as needed.
172 void add_workers(bool initializing);
173
174 // Add GC workers as needed to reach the specified number of workers.
175 void add_workers(uint active_workers, bool initializing);
176
177 // Return the Ith worker.
178 AbstractGangWorker* worker(uint i) const;
179
180 // Base name (without worker id #) of threads.
181 const char* group_name() { return name(); }
182
183 void threads_do(ThreadClosure* tc) const;
184
185 // Create a GC worker and install it into the work gang.
186 virtual AbstractGangWorker* install_worker(uint which);
187
188 // Debugging.
189 const char* name() const { return _name; }
190
191 // Printing
192 void print_worker_threads_on(outputStream *st) const;
193 void print_worker_threads() const {
194 print_worker_threads_on(tty);
195 }
196
197 protected:
198 virtual AbstractGangWorker* allocate_worker(uint which) = 0;
199 };
200
201 // An class representing a gang of workers.
202 class WorkGang: public AbstractWorkGang {
203 // To get access to the GangTaskDispatcher instance.
204 friend class GangWorker;
205
206 GangTaskDispatcher* const _dispatcher;
207 GangTaskDispatcher* dispatcher() const {
208 return _dispatcher;
209 }
210
211 public:
212 WorkGang(const char* name,
213 uint workers,
214 bool are_GC_task_threads,
215 bool are_ConcurrentGC_threads);
216
217 ~WorkGang();
218
219 // Run a task using the current active number of workers, returns when the task is done.
220 virtual void run_task(AbstractGangTask* task);
221 // Run a task with the given number of workers, returns
222 // when the task is done. The number of workers must be at most the number of
223 // active workers. Additional workers may be created if an insufficient
224 // number currently exists.
225 void run_task(AbstractGangTask* task, uint num_workers);
226
227 protected:
228 virtual AbstractGangWorker* allocate_worker(uint which);
229 };
230
231 // Several instances of this class run in parallel as workers for a gang.
232 class AbstractGangWorker: public WorkerThread {
233 public:
234 AbstractGangWorker(AbstractWorkGang* gang, uint id);
235
236 // The only real method: run a task for the gang.
237 virtual void run();
238 // Predicate for Thread
239 virtual bool is_GC_task_thread() const;
240 virtual bool is_ConcurrentGC_thread() const;
241 // Printing
242 void print_on(outputStream* st) const;
243 virtual void print() const { print_on(tty); }
244
245 protected:
246 AbstractWorkGang* _gang;
247
248 virtual void initialize();
249 virtual void loop() = 0;
250
251 AbstractWorkGang* gang() const { return _gang; }
252 };
253
254 class GangWorker: public AbstractGangWorker {
255 public:
256 GangWorker(WorkGang* gang, uint id) : AbstractGangWorker(gang, id) {}
257
258 protected:
259 virtual void loop();
260
261 private:
262 WorkData wait_for_task();
263 void run_task(WorkData work);
264 void signal_task_done();
265
266 WorkGang* gang() const { return (WorkGang*)_gang; }
267 };
268
269 // A class that acts as a synchronisation barrier. Workers enter
270 // the barrier and must wait until all other workers have entered
271 // before any of them may leave.
272
273 class WorkGangBarrierSync : public StackObj {
274 protected:
275 Monitor _monitor;
276 uint _n_workers;
277 uint _n_completed;
278 bool _should_reset;
279 bool _aborted;
280
281 Monitor* monitor() { return &_monitor; }
282 uint n_workers() { return _n_workers; }
283 uint n_completed() { return _n_completed; }
284 bool should_reset() { return _should_reset; }
285 bool aborted() { return _aborted; }
286
287 void zero_completed() { _n_completed = 0; }
288 void inc_completed() { _n_completed++; }
289 void set_aborted() { _aborted = true; }
290 void set_should_reset(bool v) { _should_reset = v; }
291
292 public:
293 WorkGangBarrierSync();
294 WorkGangBarrierSync(uint n_workers, const char* name);
295
296 // Set the number of workers that will use the barrier.
297 // Must be called before any of the workers start running.
298 void set_n_workers(uint n_workers);
299
300 // Enter the barrier. A worker that enters the barrier will
301 // not be allowed to leave until all other threads have
302 // also entered the barrier or the barrier is aborted.
303 // Returns false if the barrier was aborted.
304 bool enter();
305
306 // Aborts the barrier and wakes up any threads waiting for
307 // the barrier to complete. The barrier will remain in the
308 // aborted state until the next call to set_n_workers().
309 void abort();
310 };
311
312 // A class to manage claiming of subtasks within a group of tasks. The
313 // subtasks will be identified by integer indices, usually elements of an
314 // enumeration type.
315
316 class SubTasksDone: public CHeapObj<mtInternal> {
317 volatile uint* _tasks;
318 uint _n_tasks;
319 volatile uint _threads_completed;
320 #ifdef ASSERT
321 volatile uint _claimed;
322 #endif
323
324 // Set all tasks to unclaimed.
325 void clear();
326
327 public:
328 // Initializes "this" to a state in which there are "n" tasks to be
329 // processed, none of the which are originally claimed. The number of
330 // threads doing the tasks is initialized 1.
331 SubTasksDone(uint n);
332
333 // True iff the object is in a valid state.
334 bool valid();
335
336 // Returns "false" if the task "t" is unclaimed, and ensures that task is
337 // claimed. The task "t" is required to be within the range of "this".
338 bool is_task_claimed(uint t);
339
340 // The calling thread asserts that it has attempted to claim all the
341 // tasks that it will try to claim. Every thread in the parallel task
342 // must execute this. (When the last thread does so, the task array is
343 // cleared.)
344 //
345 // n_threads - Number of threads executing the sub-tasks.
346 void all_tasks_completed(uint n_threads);
347
348 // Destructor.
349 ~SubTasksDone();
350 };
351
352 // As above, but for sequential tasks, i.e. instead of claiming
353 // sub-tasks from a set (possibly an enumeration), claim sub-tasks
354 // in sequential order. This is ideal for claiming dynamically
355 // partitioned tasks (like striding in the parallel remembered
356 // set scanning). Note that unlike the above class this is
357 // a stack object - is there any reason for it not to be?
358
359 class SequentialSubTasksDone : public StackObj {
360 protected:
361 uint _n_tasks; // Total number of tasks available.
362 volatile uint _n_claimed; // Number of tasks claimed.
363 // _n_threads is used to determine when a sub task is done.
364 // See comments on SubTasksDone::_n_threads
365 uint _n_threads; // Total number of parallel threads.
366 volatile uint _n_completed; // Number of completed threads.
367
368 void clear();
369
370 public:
371 SequentialSubTasksDone() {
372 clear();
373 }
374 ~SequentialSubTasksDone() {}
375
376 // True iff the object is in a valid state.
377 bool valid();
378
379 // number of tasks
380 uint n_tasks() const { return _n_tasks; }
381
382 // Get/set the number of parallel threads doing the tasks to t.
383 // Should be called before the task starts but it is safe
384 // to call this once a task is running provided that all
385 // threads agree on the number of threads.
386 uint n_threads() { return _n_threads; }
387 void set_n_threads(uint t) { _n_threads = t; }
388
389 // Set the number of tasks to be claimed to t. As above,
390 // should be called before the tasks start but it is safe
391 // to call this once a task is running provided all threads
392 // agree on the number of tasks.
393 void set_n_tasks(uint t) { _n_tasks = t; }
394
395 // Returns false if the next task in the sequence is unclaimed,
396 // and ensures that it is claimed. Will set t to be the index
397 // of the claimed task in the sequence. Will return true if
398 // the task cannot be claimed and there are none left to claim.
399 bool is_task_claimed(uint& t);
400
401 // The calling thread asserts that it has attempted to claim
402 // all the tasks it possibly can in the sequence. Every thread
403 // claiming tasks must promise call this. Returns true if this
404 // is the last thread to complete so that the thread can perform
405 // cleanup if necessary.
406 bool all_tasks_completed();
407 };
408
409 #endif // SHARE_VM_GC_SHARED_WORKGROUP_HPP