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annotate src/share/vm/utilities/yieldingWorkgroup.cpp @ 14702:d4dd5204c0aa
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author | ehelin |
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date | Fri, 14 Mar 2014 13:27:18 +0100 |
parents | de6a9e811145 |
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0 | 1 /* |
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2 * Copyright (c) 2005, 2013, Oracle and/or its affiliates. All rights reserved. |
0 | 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 * | |
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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20 * or visit www.oracle.com if you need additional information or have any |
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21 * questions. |
0 | 22 * |
23 */ | |
24 | |
1972 | 25 #include "precompiled.hpp" |
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26 #include "utilities/macros.hpp" |
1972 | 27 #include "utilities/yieldingWorkgroup.hpp" |
0 | 28 |
29 // Forward declaration of classes declared here. | |
30 | |
31 class GangWorker; | |
32 class WorkData; | |
33 | |
34 YieldingFlexibleWorkGang::YieldingFlexibleWorkGang( | |
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35 const char* name, uint workers, bool are_GC_task_threads) : |
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36 FlexibleWorkGang(name, workers, are_GC_task_threads, false), |
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37 _yielded_workers(0) {} |
0 | 38 |
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39 GangWorker* YieldingFlexibleWorkGang::allocate_worker(uint which) { |
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40 YieldingFlexibleGangWorker* new_member = |
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41 new YieldingFlexibleGangWorker(this, which); |
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42 return (YieldingFlexibleGangWorker*) new_member; |
0 | 43 } |
44 | |
45 // Run a task; returns when the task is done, or the workers yield, | |
46 // or the task is aborted, or the work gang is terminated via stop(). | |
47 // A task that has been yielded can be continued via this interface | |
48 // by using the same task repeatedly as the argument to the call. | |
49 // It is expected that the YieldingFlexibleGangTask carries the appropriate | |
50 // continuation information used by workers to continue the task | |
51 // from its last yield point. Thus, a completed task will return | |
52 // immediately with no actual work having been done by the workers. | |
53 ///////////////////// | |
54 // Implementatiuon notes: remove before checking XXX | |
55 /* | |
56 Each gang is working on a task at a certain time. | |
57 Some subset of workers may have yielded and some may | |
58 have finished their quota of work. Until this task has | |
59 been completed, the workers are bound to that task. | |
60 Once the task has been completed, the gang unbounds | |
61 itself from the task. | |
62 | |
63 The yielding work gang thus exports two invokation | |
64 interfaces: run_task() and continue_task(). The | |
65 first is used to initiate a new task and bind it | |
66 to the workers; the second is used to continue an | |
67 already bound task that has yielded. Upon completion | |
68 the binding is released and a new binding may be | |
69 created. | |
70 | |
71 The shape of a yielding work gang is as follows: | |
72 | |
73 Overseer invokes run_task(*task). | |
74 Lock gang monitor | |
75 Check that there is no existing binding for the gang | |
76 If so, abort with an error | |
77 Else, create a new binding of this gang to the given task | |
78 Set number of active workers (as asked) | |
79 Notify workers that work is ready to be done | |
80 [the requisite # workers would then start up | |
81 and do the task] | |
82 Wait on the monitor until either | |
83 all work is completed or the task has yielded | |
84 -- this is normally done through | |
85 yielded + completed == active | |
86 [completed workers are rest to idle state by overseer?] | |
87 return appropriate status to caller | |
88 | |
89 Overseer invokes continue_task(*task), | |
90 Lock gang monitor | |
91 Check that task is the same as current binding | |
92 If not, abort with an error | |
93 Else, set the number of active workers as requested? | |
94 Notify workers that they can continue from yield points | |
95 New workers can also start up as required | |
96 while satisfying the constraint that | |
97 active + yielded does not exceed required number | |
98 Wait (as above). | |
99 | |
100 NOTE: In the above, for simplicity in a first iteration | |
101 our gangs will be of fixed population and will not | |
102 therefore be flexible work gangs, just yielding work | |
103 gangs. Once this works well, we will in a second | |
104 iteration.refinement introduce flexibility into | |
105 the work gang. | |
106 | |
107 NOTE: we can always create a new gang per each iteration | |
108 in order to get the flexibility, but we will for now | |
109 desist that simplified route. | |
110 | |
111 */ | |
112 ///////////////////// | |
113 void YieldingFlexibleWorkGang::start_task(YieldingFlexibleGangTask* new_task) { | |
114 MutexLockerEx ml(monitor(), Mutex::_no_safepoint_check_flag); | |
115 assert(task() == NULL, "Gang currently tied to a task"); | |
116 assert(new_task != NULL, "Null task"); | |
117 // Bind task to gang | |
118 _task = new_task; | |
119 new_task->set_gang(this); // Establish 2-way binding to support yielding | |
120 _sequence_number++; | |
121 | |
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122 uint requested_size = new_task->requested_size(); |
0 | 123 assert(requested_size >= 0, "Should be non-negative"); |
124 if (requested_size != 0) { | |
125 _active_workers = MIN2(requested_size, total_workers()); | |
126 } else { | |
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127 _active_workers = active_workers(); |
0 | 128 } |
129 new_task->set_actual_size(_active_workers); | |
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130 new_task->set_for_termination(_active_workers); |
0 | 131 |
132 assert(_started_workers == 0, "Tabula rasa non"); | |
133 assert(_finished_workers == 0, "Tabula rasa non"); | |
134 assert(_yielded_workers == 0, "Tabula rasa non"); | |
135 yielding_task()->set_status(ACTIVE); | |
136 | |
137 // Wake up all the workers, the first few will get to work, | |
138 // and the rest will go back to sleep | |
139 monitor()->notify_all(); | |
140 wait_for_gang(); | |
141 } | |
142 | |
143 void YieldingFlexibleWorkGang::wait_for_gang() { | |
144 | |
145 assert(monitor()->owned_by_self(), "Data race"); | |
146 // Wait for task to complete or yield | |
147 for (Status status = yielding_task()->status(); | |
148 status != COMPLETED && status != YIELDED && status != ABORTED; | |
149 status = yielding_task()->status()) { | |
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150 assert(started_workers() <= active_workers(), "invariant"); |
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151 assert(finished_workers() <= active_workers(), "invariant"); |
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152 assert(yielded_workers() <= active_workers(), "invariant"); |
0 | 153 monitor()->wait(Mutex::_no_safepoint_check_flag); |
154 } | |
155 switch (yielding_task()->status()) { | |
156 case COMPLETED: | |
157 case ABORTED: { | |
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158 assert(finished_workers() == active_workers(), "Inconsistent status"); |
0 | 159 assert(yielded_workers() == 0, "Invariant"); |
160 reset(); // for next task; gang<->task binding released | |
161 break; | |
162 } | |
163 case YIELDED: { | |
164 assert(yielded_workers() > 0, "Invariant"); | |
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165 assert(yielded_workers() + finished_workers() == active_workers(), |
0 | 166 "Inconsistent counts"); |
167 break; | |
168 } | |
169 case ACTIVE: | |
170 case INACTIVE: | |
171 case COMPLETING: | |
172 case YIELDING: | |
173 case ABORTING: | |
174 default: | |
175 ShouldNotReachHere(); | |
176 } | |
177 } | |
178 | |
179 void YieldingFlexibleWorkGang::continue_task( | |
180 YieldingFlexibleGangTask* gang_task) { | |
181 | |
182 MutexLockerEx ml(monitor(), Mutex::_no_safepoint_check_flag); | |
183 assert(task() != NULL && task() == gang_task, "Incorrect usage"); | |
184 assert(_started_workers == _active_workers, "Precondition"); | |
185 assert(_yielded_workers > 0 && yielding_task()->status() == YIELDED, | |
186 "Else why are we calling continue_task()"); | |
187 // Restart the yielded gang workers | |
188 yielding_task()->set_status(ACTIVE); | |
189 monitor()->notify_all(); | |
190 wait_for_gang(); | |
191 } | |
192 | |
193 void YieldingFlexibleWorkGang::reset() { | |
194 _started_workers = 0; | |
195 _finished_workers = 0; | |
196 yielding_task()->set_gang(NULL); | |
197 _task = NULL; // unbind gang from task | |
198 } | |
199 | |
200 void YieldingFlexibleWorkGang::yield() { | |
201 assert(task() != NULL, "Inconsistency; should have task binding"); | |
202 MutexLockerEx ml(monitor(), Mutex::_no_safepoint_check_flag); | |
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203 assert(yielded_workers() < active_workers(), "Consistency check"); |
0 | 204 if (yielding_task()->status() == ABORTING) { |
205 // Do not yield; we need to abort as soon as possible | |
206 // XXX NOTE: This can cause a performance pathology in the | |
207 // current implementation in Mustang, as of today, and | |
208 // pre-Mustang in that as soon as an overflow occurs, | |
209 // yields will not be honoured. The right way to proceed | |
210 // of course is to fix bug # TBF, so that abort's cause | |
211 // us to return at each potential yield point. | |
212 return; | |
213 } | |
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214 if (++_yielded_workers + finished_workers() == active_workers()) { |
0 | 215 yielding_task()->set_status(YIELDED); |
216 monitor()->notify_all(); | |
217 } else { | |
218 yielding_task()->set_status(YIELDING); | |
219 } | |
220 | |
221 while (true) { | |
222 switch (yielding_task()->status()) { | |
223 case YIELDING: | |
224 case YIELDED: { | |
225 monitor()->wait(Mutex::_no_safepoint_check_flag); | |
226 break; // from switch | |
227 } | |
228 case ACTIVE: | |
229 case ABORTING: | |
230 case COMPLETING: { | |
231 assert(_yielded_workers > 0, "Else why am i here?"); | |
232 _yielded_workers--; | |
233 return; | |
234 } | |
235 case INACTIVE: | |
236 case ABORTED: | |
237 case COMPLETED: | |
238 default: { | |
239 ShouldNotReachHere(); | |
240 } | |
241 } | |
242 } | |
243 // Only return is from inside switch statement above | |
244 ShouldNotReachHere(); | |
245 } | |
246 | |
247 void YieldingFlexibleWorkGang::abort() { | |
248 assert(task() != NULL, "Inconsistency; should have task binding"); | |
249 MutexLockerEx ml(monitor(), Mutex::_no_safepoint_check_flag); | |
250 assert(yielded_workers() < active_workers(), "Consistency check"); | |
251 #ifndef PRODUCT | |
252 switch (yielding_task()->status()) { | |
253 // allowed states | |
254 case ACTIVE: | |
255 case ABORTING: | |
256 case COMPLETING: | |
257 case YIELDING: | |
258 break; | |
259 // not allowed states | |
260 case INACTIVE: | |
261 case ABORTED: | |
262 case COMPLETED: | |
263 case YIELDED: | |
264 default: | |
265 ShouldNotReachHere(); | |
266 } | |
267 #endif // !PRODUCT | |
268 Status prev_status = yielding_task()->status(); | |
269 yielding_task()->set_status(ABORTING); | |
270 if (prev_status == YIELDING) { | |
271 assert(yielded_workers() > 0, "Inconsistency"); | |
272 // At least one thread has yielded, wake it up | |
273 // so it can go back to waiting stations ASAP. | |
274 monitor()->notify_all(); | |
275 } | |
276 } | |
277 | |
278 /////////////////////////////// | |
279 // YieldingFlexibleGangTask | |
280 /////////////////////////////// | |
281 void YieldingFlexibleGangTask::yield() { | |
282 assert(gang() != NULL, "No gang to signal"); | |
283 gang()->yield(); | |
284 } | |
285 | |
286 void YieldingFlexibleGangTask::abort() { | |
287 assert(gang() != NULL, "No gang to signal"); | |
288 gang()->abort(); | |
289 } | |
290 | |
291 /////////////////////////////// | |
292 // YieldingFlexibleGangWorker | |
293 /////////////////////////////// | |
294 void YieldingFlexibleGangWorker::loop() { | |
295 int previous_sequence_number = 0; | |
296 Monitor* gang_monitor = gang()->monitor(); | |
297 MutexLockerEx ml(gang_monitor, Mutex::_no_safepoint_check_flag); | |
298 WorkData data; | |
299 int id; | |
300 while (true) { | |
301 // Check if there is work to do or if we have been asked | |
302 // to terminate | |
303 gang()->internal_worker_poll(&data); | |
304 if (data.terminate()) { | |
305 // We have been asked to terminate. | |
306 assert(gang()->task() == NULL, "No task binding"); | |
307 // set_status(TERMINATED); | |
308 return; | |
309 } else if (data.task() != NULL && | |
310 data.sequence_number() != previous_sequence_number) { | |
311 // There is work to be done. | |
312 // First check if we need to become active or if there | |
313 // are already the requisite number of workers | |
314 if (gang()->started_workers() == yf_gang()->active_workers()) { | |
315 // There are already enough workers, we do not need to | |
316 // to run; fall through and wait on monitor. | |
317 } else { | |
318 // We need to pitch in and do the work. | |
319 assert(gang()->started_workers() < yf_gang()->active_workers(), | |
320 "Unexpected state"); | |
321 id = gang()->started_workers(); | |
322 gang()->internal_note_start(); | |
323 // Now, release the gang mutex and do the work. | |
324 { | |
325 MutexUnlockerEx mul(gang_monitor, Mutex::_no_safepoint_check_flag); | |
326 data.task()->work(id); // This might include yielding | |
327 } | |
328 // Reacquire monitor and note completion of this worker | |
329 gang()->internal_note_finish(); | |
330 // Update status of task based on whether all workers have | |
331 // finished or some have yielded | |
332 assert(data.task() == gang()->task(), "Confused task binding"); | |
333 if (gang()->finished_workers() == yf_gang()->active_workers()) { | |
334 switch (data.yf_task()->status()) { | |
335 case ABORTING: { | |
336 data.yf_task()->set_status(ABORTED); | |
337 break; | |
338 } | |
339 case ACTIVE: | |
340 case COMPLETING: { | |
341 data.yf_task()->set_status(COMPLETED); | |
342 break; | |
343 } | |
344 default: | |
345 ShouldNotReachHere(); | |
346 } | |
347 gang_monitor->notify_all(); // Notify overseer | |
348 } else { // at least one worker is still working or yielded | |
349 assert(gang()->finished_workers() < yf_gang()->active_workers(), | |
350 "Counts inconsistent"); | |
351 switch (data.yf_task()->status()) { | |
352 case ACTIVE: { | |
353 // first, but not only thread to complete | |
354 data.yf_task()->set_status(COMPLETING); | |
355 break; | |
356 } | |
357 case YIELDING: { | |
358 if (gang()->finished_workers() + yf_gang()->yielded_workers() | |
359 == yf_gang()->active_workers()) { | |
360 data.yf_task()->set_status(YIELDED); | |
361 gang_monitor->notify_all(); // notify overseer | |
362 } | |
363 break; | |
364 } | |
365 case ABORTING: | |
366 case COMPLETING: { | |
367 break; // nothing to do | |
368 } | |
369 default: // everything else: INACTIVE, YIELDED, ABORTED, COMPLETED | |
370 ShouldNotReachHere(); | |
371 } | |
372 } | |
373 } | |
374 } | |
375 // Remember the sequence number | |
376 previous_sequence_number = data.sequence_number(); | |
377 // Wait for more work | |
378 gang_monitor->wait(Mutex::_no_safepoint_check_flag); | |
379 } | |
380 } |