Mercurial > hg > truffle
annotate src/share/vm/utilities/yieldingWorkgroup.cpp @ 3202:9352a9c26095
revert outer framesate scheduling change
author | Gilles Duboscq <gilles.duboscq@oracle.com> |
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date | Fri, 08 Jul 2011 18:00:39 +0200 |
parents | f95d63e2154a |
children | fe189d4a44e9 |
rev | line source |
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0 | 1 /* |
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2 * Copyright (c) 2005, 2010 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" |
26 #ifndef SERIALGC | |
27 #include "utilities/yieldingWorkgroup.hpp" | |
28 #endif | |
0 | 29 |
30 // Forward declaration of classes declared here. | |
31 | |
32 class GangWorker; | |
33 class WorkData; | |
34 | |
35 YieldingFlexibleWorkGang::YieldingFlexibleWorkGang( | |
342 | 36 const char* name, int workers, bool are_GC_task_threads) : |
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37 FlexibleWorkGang(name, workers, are_GC_task_threads, false), |
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38 _yielded_workers(0) {} |
0 | 39 |
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40 GangWorker* YieldingFlexibleWorkGang::allocate_worker(int which) { |
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41 YieldingFlexibleGangWorker* new_member = |
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42 new YieldingFlexibleGangWorker(this, which); |
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43 return (YieldingFlexibleGangWorker*) new_member; |
0 | 44 } |
45 | |
46 // Run a task; returns when the task is done, or the workers yield, | |
47 // or the task is aborted, or the work gang is terminated via stop(). | |
48 // A task that has been yielded can be continued via this interface | |
49 // by using the same task repeatedly as the argument to the call. | |
50 // It is expected that the YieldingFlexibleGangTask carries the appropriate | |
51 // continuation information used by workers to continue the task | |
52 // from its last yield point. Thus, a completed task will return | |
53 // immediately with no actual work having been done by the workers. | |
54 ///////////////////// | |
55 // Implementatiuon notes: remove before checking XXX | |
56 /* | |
57 Each gang is working on a task at a certain time. | |
58 Some subset of workers may have yielded and some may | |
59 have finished their quota of work. Until this task has | |
60 been completed, the workers are bound to that task. | |
61 Once the task has been completed, the gang unbounds | |
62 itself from the task. | |
63 | |
64 The yielding work gang thus exports two invokation | |
65 interfaces: run_task() and continue_task(). The | |
66 first is used to initiate a new task and bind it | |
67 to the workers; the second is used to continue an | |
68 already bound task that has yielded. Upon completion | |
69 the binding is released and a new binding may be | |
70 created. | |
71 | |
72 The shape of a yielding work gang is as follows: | |
73 | |
74 Overseer invokes run_task(*task). | |
75 Lock gang monitor | |
76 Check that there is no existing binding for the gang | |
77 If so, abort with an error | |
78 Else, create a new binding of this gang to the given task | |
79 Set number of active workers (as asked) | |
80 Notify workers that work is ready to be done | |
81 [the requisite # workers would then start up | |
82 and do the task] | |
83 Wait on the monitor until either | |
84 all work is completed or the task has yielded | |
85 -- this is normally done through | |
86 yielded + completed == active | |
87 [completed workers are rest to idle state by overseer?] | |
88 return appropriate status to caller | |
89 | |
90 Overseer invokes continue_task(*task), | |
91 Lock gang monitor | |
92 Check that task is the same as current binding | |
93 If not, abort with an error | |
94 Else, set the number of active workers as requested? | |
95 Notify workers that they can continue from yield points | |
96 New workers can also start up as required | |
97 while satisfying the constraint that | |
98 active + yielded does not exceed required number | |
99 Wait (as above). | |
100 | |
101 NOTE: In the above, for simplicity in a first iteration | |
102 our gangs will be of fixed population and will not | |
103 therefore be flexible work gangs, just yielding work | |
104 gangs. Once this works well, we will in a second | |
105 iteration.refinement introduce flexibility into | |
106 the work gang. | |
107 | |
108 NOTE: we can always create a new gang per each iteration | |
109 in order to get the flexibility, but we will for now | |
110 desist that simplified route. | |
111 | |
112 */ | |
113 ///////////////////// | |
114 void YieldingFlexibleWorkGang::start_task(YieldingFlexibleGangTask* new_task) { | |
115 MutexLockerEx ml(monitor(), Mutex::_no_safepoint_check_flag); | |
116 assert(task() == NULL, "Gang currently tied to a task"); | |
117 assert(new_task != NULL, "Null task"); | |
118 // Bind task to gang | |
119 _task = new_task; | |
120 new_task->set_gang(this); // Establish 2-way binding to support yielding | |
121 _sequence_number++; | |
122 | |
123 int requested_size = new_task->requested_size(); | |
124 assert(requested_size >= 0, "Should be non-negative"); | |
125 if (requested_size != 0) { | |
126 _active_workers = MIN2(requested_size, total_workers()); | |
127 } else { | |
128 _active_workers = total_workers(); | |
129 } | |
130 new_task->set_actual_size(_active_workers); | |
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131 new_task->set_for_termination(_active_workers); |
0 | 132 |
133 assert(_started_workers == 0, "Tabula rasa non"); | |
134 assert(_finished_workers == 0, "Tabula rasa non"); | |
135 assert(_yielded_workers == 0, "Tabula rasa non"); | |
136 yielding_task()->set_status(ACTIVE); | |
137 | |
138 // Wake up all the workers, the first few will get to work, | |
139 // and the rest will go back to sleep | |
140 monitor()->notify_all(); | |
141 wait_for_gang(); | |
142 } | |
143 | |
144 void YieldingFlexibleWorkGang::wait_for_gang() { | |
145 | |
146 assert(monitor()->owned_by_self(), "Data race"); | |
147 // Wait for task to complete or yield | |
148 for (Status status = yielding_task()->status(); | |
149 status != COMPLETED && status != YIELDED && status != ABORTED; | |
150 status = yielding_task()->status()) { | |
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151 assert(started_workers() <= total_workers(), "invariant"); |
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152 assert(finished_workers() <= total_workers(), "invariant"); |
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153 assert(yielded_workers() <= total_workers(), "invariant"); |
0 | 154 monitor()->wait(Mutex::_no_safepoint_check_flag); |
155 } | |
156 switch (yielding_task()->status()) { | |
157 case COMPLETED: | |
158 case ABORTED: { | |
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159 assert(finished_workers() == total_workers(), "Inconsistent status"); |
0 | 160 assert(yielded_workers() == 0, "Invariant"); |
161 reset(); // for next task; gang<->task binding released | |
162 break; | |
163 } | |
164 case YIELDED: { | |
165 assert(yielded_workers() > 0, "Invariant"); | |
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166 assert(yielded_workers() + finished_workers() == total_workers(), |
0 | 167 "Inconsistent counts"); |
168 break; | |
169 } | |
170 case ACTIVE: | |
171 case INACTIVE: | |
172 case COMPLETING: | |
173 case YIELDING: | |
174 case ABORTING: | |
175 default: | |
176 ShouldNotReachHere(); | |
177 } | |
178 } | |
179 | |
180 void YieldingFlexibleWorkGang::continue_task( | |
181 YieldingFlexibleGangTask* gang_task) { | |
182 | |
183 MutexLockerEx ml(monitor(), Mutex::_no_safepoint_check_flag); | |
184 assert(task() != NULL && task() == gang_task, "Incorrect usage"); | |
185 // assert(_active_workers == total_workers(), "For now"); | |
186 assert(_started_workers == _active_workers, "Precondition"); | |
187 assert(_yielded_workers > 0 && yielding_task()->status() == YIELDED, | |
188 "Else why are we calling continue_task()"); | |
189 // Restart the yielded gang workers | |
190 yielding_task()->set_status(ACTIVE); | |
191 monitor()->notify_all(); | |
192 wait_for_gang(); | |
193 } | |
194 | |
195 void YieldingFlexibleWorkGang::reset() { | |
196 _started_workers = 0; | |
197 _finished_workers = 0; | |
198 yielding_task()->set_gang(NULL); | |
199 _task = NULL; // unbind gang from task | |
200 } | |
201 | |
202 void YieldingFlexibleWorkGang::yield() { | |
203 assert(task() != NULL, "Inconsistency; should have task binding"); | |
204 MutexLockerEx ml(monitor(), Mutex::_no_safepoint_check_flag); | |
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205 assert(yielded_workers() < total_workers(), "Consistency check"); |
0 | 206 if (yielding_task()->status() == ABORTING) { |
207 // Do not yield; we need to abort as soon as possible | |
208 // XXX NOTE: This can cause a performance pathology in the | |
209 // current implementation in Mustang, as of today, and | |
210 // pre-Mustang in that as soon as an overflow occurs, | |
211 // yields will not be honoured. The right way to proceed | |
212 // of course is to fix bug # TBF, so that abort's cause | |
213 // us to return at each potential yield point. | |
214 return; | |
215 } | |
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216 if (++_yielded_workers + finished_workers() == total_workers()) { |
0 | 217 yielding_task()->set_status(YIELDED); |
218 monitor()->notify_all(); | |
219 } else { | |
220 yielding_task()->set_status(YIELDING); | |
221 } | |
222 | |
223 while (true) { | |
224 switch (yielding_task()->status()) { | |
225 case YIELDING: | |
226 case YIELDED: { | |
227 monitor()->wait(Mutex::_no_safepoint_check_flag); | |
228 break; // from switch | |
229 } | |
230 case ACTIVE: | |
231 case ABORTING: | |
232 case COMPLETING: { | |
233 assert(_yielded_workers > 0, "Else why am i here?"); | |
234 _yielded_workers--; | |
235 return; | |
236 } | |
237 case INACTIVE: | |
238 case ABORTED: | |
239 case COMPLETED: | |
240 default: { | |
241 ShouldNotReachHere(); | |
242 } | |
243 } | |
244 } | |
245 // Only return is from inside switch statement above | |
246 ShouldNotReachHere(); | |
247 } | |
248 | |
249 void YieldingFlexibleWorkGang::abort() { | |
250 assert(task() != NULL, "Inconsistency; should have task binding"); | |
251 MutexLockerEx ml(monitor(), Mutex::_no_safepoint_check_flag); | |
252 assert(yielded_workers() < active_workers(), "Consistency check"); | |
253 #ifndef PRODUCT | |
254 switch (yielding_task()->status()) { | |
255 // allowed states | |
256 case ACTIVE: | |
257 case ABORTING: | |
258 case COMPLETING: | |
259 case YIELDING: | |
260 break; | |
261 // not allowed states | |
262 case INACTIVE: | |
263 case ABORTED: | |
264 case COMPLETED: | |
265 case YIELDED: | |
266 default: | |
267 ShouldNotReachHere(); | |
268 } | |
269 #endif // !PRODUCT | |
270 Status prev_status = yielding_task()->status(); | |
271 yielding_task()->set_status(ABORTING); | |
272 if (prev_status == YIELDING) { | |
273 assert(yielded_workers() > 0, "Inconsistency"); | |
274 // At least one thread has yielded, wake it up | |
275 // so it can go back to waiting stations ASAP. | |
276 monitor()->notify_all(); | |
277 } | |
278 } | |
279 | |
280 /////////////////////////////// | |
281 // YieldingFlexibleGangTask | |
282 /////////////////////////////// | |
283 void YieldingFlexibleGangTask::yield() { | |
284 assert(gang() != NULL, "No gang to signal"); | |
285 gang()->yield(); | |
286 } | |
287 | |
288 void YieldingFlexibleGangTask::abort() { | |
289 assert(gang() != NULL, "No gang to signal"); | |
290 gang()->abort(); | |
291 } | |
292 | |
293 /////////////////////////////// | |
294 // YieldingFlexibleGangWorker | |
295 /////////////////////////////// | |
296 void YieldingFlexibleGangWorker::loop() { | |
297 int previous_sequence_number = 0; | |
298 Monitor* gang_monitor = gang()->monitor(); | |
299 MutexLockerEx ml(gang_monitor, Mutex::_no_safepoint_check_flag); | |
300 WorkData data; | |
301 int id; | |
302 while (true) { | |
303 // Check if there is work to do or if we have been asked | |
304 // to terminate | |
305 gang()->internal_worker_poll(&data); | |
306 if (data.terminate()) { | |
307 // We have been asked to terminate. | |
308 assert(gang()->task() == NULL, "No task binding"); | |
309 // set_status(TERMINATED); | |
310 return; | |
311 } else if (data.task() != NULL && | |
312 data.sequence_number() != previous_sequence_number) { | |
313 // There is work to be done. | |
314 // First check if we need to become active or if there | |
315 // are already the requisite number of workers | |
316 if (gang()->started_workers() == yf_gang()->active_workers()) { | |
317 // There are already enough workers, we do not need to | |
318 // to run; fall through and wait on monitor. | |
319 } else { | |
320 // We need to pitch in and do the work. | |
321 assert(gang()->started_workers() < yf_gang()->active_workers(), | |
322 "Unexpected state"); | |
323 id = gang()->started_workers(); | |
324 gang()->internal_note_start(); | |
325 // Now, release the gang mutex and do the work. | |
326 { | |
327 MutexUnlockerEx mul(gang_monitor, Mutex::_no_safepoint_check_flag); | |
328 data.task()->work(id); // This might include yielding | |
329 } | |
330 // Reacquire monitor and note completion of this worker | |
331 gang()->internal_note_finish(); | |
332 // Update status of task based on whether all workers have | |
333 // finished or some have yielded | |
334 assert(data.task() == gang()->task(), "Confused task binding"); | |
335 if (gang()->finished_workers() == yf_gang()->active_workers()) { | |
336 switch (data.yf_task()->status()) { | |
337 case ABORTING: { | |
338 data.yf_task()->set_status(ABORTED); | |
339 break; | |
340 } | |
341 case ACTIVE: | |
342 case COMPLETING: { | |
343 data.yf_task()->set_status(COMPLETED); | |
344 break; | |
345 } | |
346 default: | |
347 ShouldNotReachHere(); | |
348 } | |
349 gang_monitor->notify_all(); // Notify overseer | |
350 } else { // at least one worker is still working or yielded | |
351 assert(gang()->finished_workers() < yf_gang()->active_workers(), | |
352 "Counts inconsistent"); | |
353 switch (data.yf_task()->status()) { | |
354 case ACTIVE: { | |
355 // first, but not only thread to complete | |
356 data.yf_task()->set_status(COMPLETING); | |
357 break; | |
358 } | |
359 case YIELDING: { | |
360 if (gang()->finished_workers() + yf_gang()->yielded_workers() | |
361 == yf_gang()->active_workers()) { | |
362 data.yf_task()->set_status(YIELDED); | |
363 gang_monitor->notify_all(); // notify overseer | |
364 } | |
365 break; | |
366 } | |
367 case ABORTING: | |
368 case COMPLETING: { | |
369 break; // nothing to do | |
370 } | |
371 default: // everything else: INACTIVE, YIELDED, ABORTED, COMPLETED | |
372 ShouldNotReachHere(); | |
373 } | |
374 } | |
375 } | |
376 } | |
377 // Remember the sequence number | |
378 previous_sequence_number = data.sequence_number(); | |
379 // Wait for more work | |
380 gang_monitor->wait(Mutex::_no_safepoint_check_flag); | |
381 } | |
382 } |