1 /*
2 * Copyright (c) 2002, 2010, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
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23 */
24
25 // Forward declarations of classes defined here
26
27 class WorkGang;
28 class GangWorker;
29 class YieldingFlexibleGangWorker;
30 class YieldingFlexibleGangTask;
31 class WorkData;
32 class AbstractWorkGang;
33
34 // An abstract task to be worked on by a gang.
35 // You subclass this to supply your own work() method
36 class AbstractGangTask VALUE_OBJ_CLASS_SPEC {
37 public:
38 // The abstract work method.
39 // The argument tells you which member of the gang you are.
40 virtual void work(int i) = 0;
41
42 // This method configures the task for proper termination.
43 // Some tasks do not have any requirements on termination
44 // and may inherit this method that does nothing. Some
45 // tasks do some coordination on termination and override
46 // this method to implement that coordination.
47 virtual void set_for_termination(int active_workers) {};
48
49 // Debugging accessor for the name.
50 const char* name() const PRODUCT_RETURN_(return NULL;);
51 int counter() { return _counter; }
52 void set_counter(int value) { _counter = value; }
53 int *address_of_counter() { return &_counter; }
54
55 // RTTI
56 NOT_PRODUCT(virtual bool is_YieldingFlexibleGang_task() const {
57 return false;
58 })
59
60 private:
61 NOT_PRODUCT(const char* _name;)
62 // ??? Should a task have a priority associated with it?
63 // ??? Or can the run method adjust priority as needed?
64 int _counter;
65
66 protected:
67 // Constructor and desctructor: only construct subclasses.
68 AbstractGangTask(const char* name) {
69 NOT_PRODUCT(_name = name);
70 _counter = 0;
71 }
72 virtual ~AbstractGangTask() { }
73 };
74
75 class AbstractGangTaskWOopQueues : public AbstractGangTask {
76 OopTaskQueueSet* _queues;
77 ParallelTaskTerminator _terminator;
78 public:
79 AbstractGangTaskWOopQueues(const char* name, OopTaskQueueSet* queues) :
80 AbstractGangTask(name), _queues(queues), _terminator(0, _queues) {}
81 ParallelTaskTerminator* terminator() { return &_terminator; }
82 virtual void set_for_termination(int active_workers) {
83 terminator()->reset_for_reuse(active_workers);
84 }
85 OopTaskQueueSet* queues() { return _queues; }
86 };
87
88 // Class AbstractWorkGang:
89 // An abstract class representing a gang of workers.
90 // You subclass this to supply an implementation of run_task().
91 class AbstractWorkGang: public CHeapObj {
92 // Here's the public interface to this class.
93 public:
94 // Constructor and destructor.
95 AbstractWorkGang(const char* name, bool are_GC_task_threads,
96 bool are_ConcurrentGC_threads);
97 ~AbstractWorkGang();
98 // Run a task, returns when the task is done (or terminated).
99 virtual void run_task(AbstractGangTask* task) = 0;
100 // Stop and terminate all workers.
101 virtual void stop();
102 public:
103 // Debugging.
104 const char* name() const;
105 protected:
106 // Initialize only instance data.
107 const bool _are_GC_task_threads;
108 const bool _are_ConcurrentGC_threads;
109 // Printing support.
110 const char* _name;
111 // The monitor which protects these data,
112 // and notifies of changes in it.
113 Monitor* _monitor;
114 // The count of the number of workers in the gang.
115 int _total_workers;
116 // Whether the workers should terminate.
117 bool _terminate;
118 // The array of worker threads for this gang.
119 // This is only needed for cleaning up.
120 GangWorker** _gang_workers;
121 // The task for this gang.
122 AbstractGangTask* _task;
123 // A sequence number for the current task.
124 int _sequence_number;
125 // The number of started workers.
126 int _started_workers;
127 // The number of finished workers.
128 int _finished_workers;
129 public:
130 // Accessors for fields
131 Monitor* monitor() const {
132 return _monitor;
133 }
134 int total_workers() const {
135 return _total_workers;
136 }
137 virtual int active_workers() const {
138 return _total_workers;
139 }
140 bool terminate() const {
141 return _terminate;
142 }
143 GangWorker** gang_workers() const {
144 return _gang_workers;
145 }
146 AbstractGangTask* task() const {
147 return _task;
148 }
149 int sequence_number() const {
150 return _sequence_number;
151 }
152 int started_workers() const {
153 return _started_workers;
154 }
155 int finished_workers() const {
156 return _finished_workers;
157 }
158 bool are_GC_task_threads() const {
159 return _are_GC_task_threads;
160 }
161 bool are_ConcurrentGC_threads() const {
162 return _are_ConcurrentGC_threads;
163 }
164 // Predicates.
165 bool is_idle() const {
166 return (task() == NULL);
167 }
168 // Return the Ith gang worker.
169 GangWorker* gang_worker(int i) const;
170
171 void threads_do(ThreadClosure* tc) const;
172
173 // Printing
174 void print_worker_threads_on(outputStream *st) const;
175 void print_worker_threads() const {
176 print_worker_threads_on(tty);
177 }
178
179 protected:
180 friend class GangWorker;
181 friend class YieldingFlexibleGangWorker;
182 // Note activation and deactivation of workers.
183 // These methods should only be called with the mutex held.
184 void internal_worker_poll(WorkData* data) const;
185 void internal_note_start();
186 void internal_note_finish();
187 };
188
189 class WorkData: public StackObj {
190 // This would be a struct, but I want accessor methods.
191 private:
192 bool _terminate;
193 AbstractGangTask* _task;
194 int _sequence_number;
195 public:
196 // Constructor and destructor
197 WorkData() {
198 _terminate = false;
199 _task = NULL;
200 _sequence_number = 0;
201 }
202 ~WorkData() {
203 }
204 // Accessors and modifiers
205 bool terminate() const { return _terminate; }
206 void set_terminate(bool value) { _terminate = value; }
207 AbstractGangTask* task() const { return _task; }
208 void set_task(AbstractGangTask* value) { _task = value; }
209 int sequence_number() const { return _sequence_number; }
210 void set_sequence_number(int value) { _sequence_number = value; }
211
212 YieldingFlexibleGangTask* yf_task() const {
213 return (YieldingFlexibleGangTask*)_task;
214 }
215 };
216
217 // Class WorkGang:
218 class WorkGang: public AbstractWorkGang {
219 public:
220 // Constructor
221 WorkGang(const char* name, int workers,
222 bool are_GC_task_threads, bool are_ConcurrentGC_threads);
223 // Run a task, returns when the task is done (or terminated).
224 virtual void run_task(AbstractGangTask* task);
225 void run_task(AbstractGangTask* task, uint no_of_parallel_workers);
226 // Allocate a worker and return a pointer to it.
227 virtual GangWorker* allocate_worker(int which);
228 // Initialize workers in the gang. Return true if initialization
229 // succeeded. The type of the worker can be overridden in a derived
230 // class with the appropriate implementation of allocate_worker().
231 bool initialize_workers();
232 };
233
234 // Class GangWorker:
235 // Several instances of this class run in parallel as workers for a gang.
236 class GangWorker: public WorkerThread {
237 public:
238 // Constructors and destructor.
239 GangWorker(AbstractWorkGang* gang, uint id);
240
241 // The only real method: run a task for the gang.
242 virtual void run();
243 // Predicate for Thread
244 virtual bool is_GC_task_thread() const;
245 virtual bool is_ConcurrentGC_thread() const;
246 // Printing
247 void print_on(outputStream* st) const;
248 virtual void print() const { print_on(tty); }
249 protected:
250 AbstractWorkGang* _gang;
251
252 virtual void initialize();
253 virtual void loop();
254
255 public:
256 AbstractWorkGang* gang() const { return _gang; }
257 };
258
259 class FlexibleWorkGang: public WorkGang {
260 protected:
261 int _active_workers;
262 public:
263 // Constructor and destructor.
264 FlexibleWorkGang(const char* name, int workers,
265 bool are_GC_task_threads,
266 bool are_ConcurrentGC_threads) :
267 WorkGang(name, workers, are_GC_task_threads, are_ConcurrentGC_threads) {
268 _active_workers = ParallelGCThreads;
269 };
270 // Accessors for fields
271 virtual int active_workers() const { return _active_workers; }
272 void set_active_workers(int v) { _active_workers = v; }
273 };
274
275 // Work gangs in garbage collectors: 2009-06-10
276 //
277 // SharedHeap - work gang for stop-the-world parallel collection.
278 // Used by
279 // ParNewGeneration
280 // CMSParRemarkTask
281 // CMSRefProcTaskExecutor
282 // G1CollectedHeap
283 // G1ParFinalCountTask
284 // ConcurrentMark
285 // CMSCollector
286
287 // A class that acts as a synchronisation barrier. Workers enter
288 // the barrier and must wait until all other workers have entered
289 // before any of them may leave.
290
291 class WorkGangBarrierSync : public StackObj {
292 protected:
293 Monitor _monitor;
294 int _n_workers;
295 int _n_completed;
296 bool _should_reset;
297
298 Monitor* monitor() { return &_monitor; }
299 int n_workers() { return _n_workers; }
300 int n_completed() { return _n_completed; }
301 bool should_reset() { return _should_reset; }
302
303 void zero_completed() { _n_completed = 0; }
304 void inc_completed() { _n_completed++; }
305
306 void set_should_reset(bool v) { _should_reset = v; }
307
308 public:
309 WorkGangBarrierSync();
310 WorkGangBarrierSync(int n_workers, const char* name);
311
312 // Set the number of workers that will use the barrier.
313 // Must be called before any of the workers start running.
314 void set_n_workers(int n_workers);
315
316 // Enter the barrier. A worker that enters the barrier will
317 // not be allowed to leave until all other threads have
318 // also entered the barrier.
319 void enter();
320 };
321
322 // A class to manage claiming of subtasks within a group of tasks. The
323 // subtasks will be identified by integer indices, usually elements of an
324 // enumeration type.
325
326 class SubTasksDone: public CHeapObj {
327 jint* _tasks;
328 int _n_tasks;
329 int _n_threads;
330 jint _threads_completed;
331 #ifdef ASSERT
332 volatile jint _claimed;
333 #endif
334
335 // Set all tasks to unclaimed.
336 void clear();
337
338 public:
339 // Initializes "this" to a state in which there are "n" tasks to be
340 // processed, none of the which are originally claimed. The number of
341 // threads doing the tasks is initialized 1.
342 SubTasksDone(int n);
343
344 // True iff the object is in a valid state.
345 bool valid();
346
347 // Get/set the number of parallel threads doing the tasks to "t". Can only
348 // be called before tasks start or after they are complete.
349 int n_threads() { return _n_threads; }
350 void set_n_threads(int t);
351
352 // Returns "false" if the task "t" is unclaimed, and ensures that task is
353 // claimed. The task "t" is required to be within the range of "this".
354 bool is_task_claimed(int t);
355
356 // The calling thread asserts that it has attempted to claim all the
357 // tasks that it will try to claim. Every thread in the parallel task
358 // must execute this. (When the last thread does so, the task array is
359 // cleared.)
360 void all_tasks_completed();
361
362 // Destructor.
363 ~SubTasksDone();
364 };
365
366 // As above, but for sequential tasks, i.e. instead of claiming
367 // sub-tasks from a set (possibly an enumeration), claim sub-tasks
368 // in sequential order. This is ideal for claiming dynamically
369 // partitioned tasks (like striding in the parallel remembered
370 // set scanning). Note that unlike the above class this is
371 // a stack object - is there any reason for it not to be?
372
373 class SequentialSubTasksDone : public StackObj {
374 protected:
375 jint _n_tasks; // Total number of tasks available.
376 jint _n_claimed; // Number of tasks claimed.
377 // _n_threads is used to determine when a sub task is done.
378 // See comments on SubTasksDone::_n_threads
379 jint _n_threads; // Total number of parallel threads.
380 jint _n_completed; // Number of completed threads.
381
382 void clear();
383
384 public:
385 SequentialSubTasksDone() {
386 clear();
387 }
388 ~SequentialSubTasksDone() {}
389
390 // True iff the object is in a valid state.
391 bool valid();
392
393 // number of tasks
394 jint n_tasks() const { return _n_tasks; }
395
396 // Get/set the number of parallel threads doing the tasks to t.
397 // Should be called before the task starts but it is safe
398 // to call this once a task is running provided that all
399 // threads agree on the number of threads.
400 int n_threads() { return _n_threads; }
401 void set_n_threads(int t) { _n_threads = t; }
402
403 // Set the number of tasks to be claimed to t. As above,
404 // should be called before the tasks start but it is safe
405 // to call this once a task is running provided all threads
406 // agree on the number of tasks.
407 void set_n_tasks(int t) { _n_tasks = t; }
408
409 // Returns false if the next task in the sequence is unclaimed,
410 // and ensures that it is claimed. Will set t to be the index
411 // of the claimed task in the sequence. Will return true if
412 // the task cannot be claimed and there are none left to claim.
413 bool is_task_claimed(int& t);
414
415 // The calling thread asserts that it has attempted to claim
416 // all the tasks it possibly can in the sequence. Every thread
417 // claiming tasks must promise call this. Returns true if this
418 // is the last thread to complete so that the thread can perform
419 // cleanup if necessary.
420 bool all_tasks_completed();
421 };
422
423 // Represents a set of free small integer ids.
424 class FreeIdSet {
425 enum {
426 end_of_list = -1,
427 claimed = -2
428 };
429
430 int _sz;
431 Monitor* _mon;
432
433 int* _ids;
434 int _hd;
435 int _waiters;
436 int _claimed;
437
438 static bool _safepoint;
439 typedef FreeIdSet* FreeIdSetPtr;
440 static const int NSets = 10;
441 static FreeIdSetPtr _sets[NSets];
442 static bool _stat_init;
443 int _index;
444
445 public:
446 FreeIdSet(int sz, Monitor* mon);
447 ~FreeIdSet();
448
449 static void set_safepoint(bool b);
450
451 // Attempt to claim the given id permanently. Returns "true" iff
452 // successful.
453 bool claim_perm_id(int i);
454
455 // Returns an unclaimed parallel id (waiting for one to be released if
456 // necessary). Returns "-1" if a GC wakes up a wait for an id.
457 int claim_par_id();
458
459 void release_par_id(int id);
460 };