Mercurial > hg > truffle
comparison src/share/vm/utilities/yieldingWorkgroup.cpp @ 0:a61af66fc99e jdk7-b24
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author | duke |
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date | Sat, 01 Dec 2007 00:00:00 +0000 |
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children | 37f87013dfd8 |
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1 /* | |
2 * Copyright 2005 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, | |
20 * CA 95054 USA or visit www.sun.com if you need additional information or | |
21 * have any questions. | |
22 * | |
23 */ | |
24 | |
25 # include "incls/_precompiled.incl" | |
26 # include "incls/_yieldingWorkgroup.cpp.incl" | |
27 | |
28 // Forward declaration of classes declared here. | |
29 | |
30 class GangWorker; | |
31 class WorkData; | |
32 | |
33 YieldingFlexibleWorkGang::YieldingFlexibleWorkGang( | |
34 const char* name, int workers, bool are_GC_threads) : | |
35 AbstractWorkGang(name, are_GC_threads) { | |
36 // Save arguments. | |
37 _total_workers = workers; | |
38 assert(_total_workers > 0, "Must have more than 1 worker"); | |
39 | |
40 _yielded_workers = 0; | |
41 | |
42 if (TraceWorkGang) { | |
43 tty->print_cr("Constructing work gang %s with %d threads", name, workers); | |
44 } | |
45 _gang_workers = NEW_C_HEAP_ARRAY(GangWorker*, workers); | |
46 assert(gang_workers() != NULL, "Failed to allocate gang workers"); | |
47 for (int worker = 0; worker < total_workers(); worker += 1) { | |
48 YieldingFlexibleGangWorker* new_worker = | |
49 new YieldingFlexibleGangWorker(this, worker); | |
50 assert(new_worker != NULL, "Failed to allocate YieldingFlexibleGangWorker"); | |
51 _gang_workers[worker] = new_worker; | |
52 if (new_worker == NULL || !os::create_thread(new_worker, os::pgc_thread)) | |
53 vm_exit_out_of_memory(0, "Cannot create worker GC thread. Out of system resources."); | |
54 if (!DisableStartThread) { | |
55 os::start_thread(new_worker); | |
56 } | |
57 } | |
58 } | |
59 | |
60 // Run a task; returns when the task is done, or the workers yield, | |
61 // or the task is aborted, or the work gang is terminated via stop(). | |
62 // A task that has been yielded can be continued via this interface | |
63 // by using the same task repeatedly as the argument to the call. | |
64 // It is expected that the YieldingFlexibleGangTask carries the appropriate | |
65 // continuation information used by workers to continue the task | |
66 // from its last yield point. Thus, a completed task will return | |
67 // immediately with no actual work having been done by the workers. | |
68 ///////////////////// | |
69 // Implementatiuon notes: remove before checking XXX | |
70 /* | |
71 Each gang is working on a task at a certain time. | |
72 Some subset of workers may have yielded and some may | |
73 have finished their quota of work. Until this task has | |
74 been completed, the workers are bound to that task. | |
75 Once the task has been completed, the gang unbounds | |
76 itself from the task. | |
77 | |
78 The yielding work gang thus exports two invokation | |
79 interfaces: run_task() and continue_task(). The | |
80 first is used to initiate a new task and bind it | |
81 to the workers; the second is used to continue an | |
82 already bound task that has yielded. Upon completion | |
83 the binding is released and a new binding may be | |
84 created. | |
85 | |
86 The shape of a yielding work gang is as follows: | |
87 | |
88 Overseer invokes run_task(*task). | |
89 Lock gang monitor | |
90 Check that there is no existing binding for the gang | |
91 If so, abort with an error | |
92 Else, create a new binding of this gang to the given task | |
93 Set number of active workers (as asked) | |
94 Notify workers that work is ready to be done | |
95 [the requisite # workers would then start up | |
96 and do the task] | |
97 Wait on the monitor until either | |
98 all work is completed or the task has yielded | |
99 -- this is normally done through | |
100 yielded + completed == active | |
101 [completed workers are rest to idle state by overseer?] | |
102 return appropriate status to caller | |
103 | |
104 Overseer invokes continue_task(*task), | |
105 Lock gang monitor | |
106 Check that task is the same as current binding | |
107 If not, abort with an error | |
108 Else, set the number of active workers as requested? | |
109 Notify workers that they can continue from yield points | |
110 New workers can also start up as required | |
111 while satisfying the constraint that | |
112 active + yielded does not exceed required number | |
113 Wait (as above). | |
114 | |
115 NOTE: In the above, for simplicity in a first iteration | |
116 our gangs will be of fixed population and will not | |
117 therefore be flexible work gangs, just yielding work | |
118 gangs. Once this works well, we will in a second | |
119 iteration.refinement introduce flexibility into | |
120 the work gang. | |
121 | |
122 NOTE: we can always create a new gang per each iteration | |
123 in order to get the flexibility, but we will for now | |
124 desist that simplified route. | |
125 | |
126 */ | |
127 ///////////////////// | |
128 void YieldingFlexibleWorkGang::start_task(YieldingFlexibleGangTask* new_task) { | |
129 MutexLockerEx ml(monitor(), Mutex::_no_safepoint_check_flag); | |
130 assert(task() == NULL, "Gang currently tied to a task"); | |
131 assert(new_task != NULL, "Null task"); | |
132 // Bind task to gang | |
133 _task = new_task; | |
134 new_task->set_gang(this); // Establish 2-way binding to support yielding | |
135 _sequence_number++; | |
136 | |
137 int requested_size = new_task->requested_size(); | |
138 assert(requested_size >= 0, "Should be non-negative"); | |
139 if (requested_size != 0) { | |
140 _active_workers = MIN2(requested_size, total_workers()); | |
141 } else { | |
142 _active_workers = total_workers(); | |
143 } | |
144 new_task->set_actual_size(_active_workers); | |
145 | |
146 assert(_started_workers == 0, "Tabula rasa non"); | |
147 assert(_finished_workers == 0, "Tabula rasa non"); | |
148 assert(_yielded_workers == 0, "Tabula rasa non"); | |
149 yielding_task()->set_status(ACTIVE); | |
150 | |
151 // Wake up all the workers, the first few will get to work, | |
152 // and the rest will go back to sleep | |
153 monitor()->notify_all(); | |
154 wait_for_gang(); | |
155 } | |
156 | |
157 void YieldingFlexibleWorkGang::wait_for_gang() { | |
158 | |
159 assert(monitor()->owned_by_self(), "Data race"); | |
160 // Wait for task to complete or yield | |
161 for (Status status = yielding_task()->status(); | |
162 status != COMPLETED && status != YIELDED && status != ABORTED; | |
163 status = yielding_task()->status()) { | |
164 assert(started_workers() <= active_workers(), "invariant"); | |
165 assert(finished_workers() <= active_workers(), "invariant"); | |
166 assert(yielded_workers() <= active_workers(), "invariant"); | |
167 monitor()->wait(Mutex::_no_safepoint_check_flag); | |
168 } | |
169 switch (yielding_task()->status()) { | |
170 case COMPLETED: | |
171 case ABORTED: { | |
172 assert(finished_workers() == active_workers(), "Inconsistent status"); | |
173 assert(yielded_workers() == 0, "Invariant"); | |
174 reset(); // for next task; gang<->task binding released | |
175 break; | |
176 } | |
177 case YIELDED: { | |
178 assert(yielded_workers() > 0, "Invariant"); | |
179 assert(yielded_workers() + finished_workers() == active_workers(), | |
180 "Inconsistent counts"); | |
181 break; | |
182 } | |
183 case ACTIVE: | |
184 case INACTIVE: | |
185 case COMPLETING: | |
186 case YIELDING: | |
187 case ABORTING: | |
188 default: | |
189 ShouldNotReachHere(); | |
190 } | |
191 } | |
192 | |
193 void YieldingFlexibleWorkGang::continue_task( | |
194 YieldingFlexibleGangTask* gang_task) { | |
195 | |
196 MutexLockerEx ml(monitor(), Mutex::_no_safepoint_check_flag); | |
197 assert(task() != NULL && task() == gang_task, "Incorrect usage"); | |
198 // assert(_active_workers == total_workers(), "For now"); | |
199 assert(_started_workers == _active_workers, "Precondition"); | |
200 assert(_yielded_workers > 0 && yielding_task()->status() == YIELDED, | |
201 "Else why are we calling continue_task()"); | |
202 // Restart the yielded gang workers | |
203 yielding_task()->set_status(ACTIVE); | |
204 monitor()->notify_all(); | |
205 wait_for_gang(); | |
206 } | |
207 | |
208 void YieldingFlexibleWorkGang::reset() { | |
209 _started_workers = 0; | |
210 _finished_workers = 0; | |
211 _active_workers = 0; | |
212 yielding_task()->set_gang(NULL); | |
213 _task = NULL; // unbind gang from task | |
214 } | |
215 | |
216 void YieldingFlexibleWorkGang::yield() { | |
217 assert(task() != NULL, "Inconsistency; should have task binding"); | |
218 MutexLockerEx ml(monitor(), Mutex::_no_safepoint_check_flag); | |
219 assert(yielded_workers() < active_workers(), "Consistency check"); | |
220 if (yielding_task()->status() == ABORTING) { | |
221 // Do not yield; we need to abort as soon as possible | |
222 // XXX NOTE: This can cause a performance pathology in the | |
223 // current implementation in Mustang, as of today, and | |
224 // pre-Mustang in that as soon as an overflow occurs, | |
225 // yields will not be honoured. The right way to proceed | |
226 // of course is to fix bug # TBF, so that abort's cause | |
227 // us to return at each potential yield point. | |
228 return; | |
229 } | |
230 if (++_yielded_workers + finished_workers() == active_workers()) { | |
231 yielding_task()->set_status(YIELDED); | |
232 monitor()->notify_all(); | |
233 } else { | |
234 yielding_task()->set_status(YIELDING); | |
235 } | |
236 | |
237 while (true) { | |
238 switch (yielding_task()->status()) { | |
239 case YIELDING: | |
240 case YIELDED: { | |
241 monitor()->wait(Mutex::_no_safepoint_check_flag); | |
242 break; // from switch | |
243 } | |
244 case ACTIVE: | |
245 case ABORTING: | |
246 case COMPLETING: { | |
247 assert(_yielded_workers > 0, "Else why am i here?"); | |
248 _yielded_workers--; | |
249 return; | |
250 } | |
251 case INACTIVE: | |
252 case ABORTED: | |
253 case COMPLETED: | |
254 default: { | |
255 ShouldNotReachHere(); | |
256 } | |
257 } | |
258 } | |
259 // Only return is from inside switch statement above | |
260 ShouldNotReachHere(); | |
261 } | |
262 | |
263 void YieldingFlexibleWorkGang::abort() { | |
264 assert(task() != NULL, "Inconsistency; should have task binding"); | |
265 MutexLockerEx ml(monitor(), Mutex::_no_safepoint_check_flag); | |
266 assert(yielded_workers() < active_workers(), "Consistency check"); | |
267 #ifndef PRODUCT | |
268 switch (yielding_task()->status()) { | |
269 // allowed states | |
270 case ACTIVE: | |
271 case ABORTING: | |
272 case COMPLETING: | |
273 case YIELDING: | |
274 break; | |
275 // not allowed states | |
276 case INACTIVE: | |
277 case ABORTED: | |
278 case COMPLETED: | |
279 case YIELDED: | |
280 default: | |
281 ShouldNotReachHere(); | |
282 } | |
283 #endif // !PRODUCT | |
284 Status prev_status = yielding_task()->status(); | |
285 yielding_task()->set_status(ABORTING); | |
286 if (prev_status == YIELDING) { | |
287 assert(yielded_workers() > 0, "Inconsistency"); | |
288 // At least one thread has yielded, wake it up | |
289 // so it can go back to waiting stations ASAP. | |
290 monitor()->notify_all(); | |
291 } | |
292 } | |
293 | |
294 /////////////////////////////// | |
295 // YieldingFlexibleGangTask | |
296 /////////////////////////////// | |
297 void YieldingFlexibleGangTask::yield() { | |
298 assert(gang() != NULL, "No gang to signal"); | |
299 gang()->yield(); | |
300 } | |
301 | |
302 void YieldingFlexibleGangTask::abort() { | |
303 assert(gang() != NULL, "No gang to signal"); | |
304 gang()->abort(); | |
305 } | |
306 | |
307 /////////////////////////////// | |
308 // YieldingFlexibleGangWorker | |
309 /////////////////////////////// | |
310 void YieldingFlexibleGangWorker::loop() { | |
311 int previous_sequence_number = 0; | |
312 Monitor* gang_monitor = gang()->monitor(); | |
313 MutexLockerEx ml(gang_monitor, Mutex::_no_safepoint_check_flag); | |
314 WorkData data; | |
315 int id; | |
316 while (true) { | |
317 // Check if there is work to do or if we have been asked | |
318 // to terminate | |
319 gang()->internal_worker_poll(&data); | |
320 if (data.terminate()) { | |
321 // We have been asked to terminate. | |
322 assert(gang()->task() == NULL, "No task binding"); | |
323 // set_status(TERMINATED); | |
324 return; | |
325 } else if (data.task() != NULL && | |
326 data.sequence_number() != previous_sequence_number) { | |
327 // There is work to be done. | |
328 // First check if we need to become active or if there | |
329 // are already the requisite number of workers | |
330 if (gang()->started_workers() == yf_gang()->active_workers()) { | |
331 // There are already enough workers, we do not need to | |
332 // to run; fall through and wait on monitor. | |
333 } else { | |
334 // We need to pitch in and do the work. | |
335 assert(gang()->started_workers() < yf_gang()->active_workers(), | |
336 "Unexpected state"); | |
337 id = gang()->started_workers(); | |
338 gang()->internal_note_start(); | |
339 // Now, release the gang mutex and do the work. | |
340 { | |
341 MutexUnlockerEx mul(gang_monitor, Mutex::_no_safepoint_check_flag); | |
342 data.task()->work(id); // This might include yielding | |
343 } | |
344 // Reacquire monitor and note completion of this worker | |
345 gang()->internal_note_finish(); | |
346 // Update status of task based on whether all workers have | |
347 // finished or some have yielded | |
348 assert(data.task() == gang()->task(), "Confused task binding"); | |
349 if (gang()->finished_workers() == yf_gang()->active_workers()) { | |
350 switch (data.yf_task()->status()) { | |
351 case ABORTING: { | |
352 data.yf_task()->set_status(ABORTED); | |
353 break; | |
354 } | |
355 case ACTIVE: | |
356 case COMPLETING: { | |
357 data.yf_task()->set_status(COMPLETED); | |
358 break; | |
359 } | |
360 default: | |
361 ShouldNotReachHere(); | |
362 } | |
363 gang_monitor->notify_all(); // Notify overseer | |
364 } else { // at least one worker is still working or yielded | |
365 assert(gang()->finished_workers() < yf_gang()->active_workers(), | |
366 "Counts inconsistent"); | |
367 switch (data.yf_task()->status()) { | |
368 case ACTIVE: { | |
369 // first, but not only thread to complete | |
370 data.yf_task()->set_status(COMPLETING); | |
371 break; | |
372 } | |
373 case YIELDING: { | |
374 if (gang()->finished_workers() + yf_gang()->yielded_workers() | |
375 == yf_gang()->active_workers()) { | |
376 data.yf_task()->set_status(YIELDED); | |
377 gang_monitor->notify_all(); // notify overseer | |
378 } | |
379 break; | |
380 } | |
381 case ABORTING: | |
382 case COMPLETING: { | |
383 break; // nothing to do | |
384 } | |
385 default: // everything else: INACTIVE, YIELDED, ABORTED, COMPLETED | |
386 ShouldNotReachHere(); | |
387 } | |
388 } | |
389 } | |
390 } | |
391 // Remember the sequence number | |
392 previous_sequence_number = data.sequence_number(); | |
393 // Wait for more work | |
394 gang_monitor->wait(Mutex::_no_safepoint_check_flag); | |
395 } | |
396 } |