Mercurial > hg > truffle
annotate src/share/vm/runtime/safepoint.cpp @ 1053:455105fc81d9 jdk7-b77
Added tag jdk7-b76 for changeset 9174bb32e934
author | katleman |
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date | Thu, 12 Nov 2009 15:35:38 -0800 |
parents | 528d98fe1037 |
children | 4b0f2f4918ed |
rev | line source |
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0 | 1 /* |
579 | 2 * Copyright 1997-2009 Sun Microsystems, Inc. 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 * | |
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/_safepoint.cpp.incl" | |
27 | |
28 // -------------------------------------------------------------------------------------------------- | |
29 // Implementation of Safepoint begin/end | |
30 | |
31 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized; | |
32 volatile int SafepointSynchronize::_waiting_to_block = 0; | |
33 jlong SafepointSynchronize::_last_safepoint = 0; | |
34 volatile int SafepointSynchronize::_safepoint_counter = 0; | |
35 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE | |
36 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only | |
37 static bool timeout_error_printed = false; | |
38 | |
39 // Roll all threads forward to a safepoint and suspend them all | |
40 void SafepointSynchronize::begin() { | |
41 | |
42 Thread* myThread = Thread::current(); | |
43 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint"); | |
44 | |
45 _last_safepoint = os::javaTimeNanos(); | |
46 | |
47 #ifndef SERIALGC | |
48 if (UseConcMarkSweepGC) { | |
49 // In the future we should investigate whether CMS can use the | |
50 // more-general mechanism below. DLD (01/05). | |
51 ConcurrentMarkSweepThread::synchronize(false); | |
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52 } else if (UseG1GC) { |
0 | 53 ConcurrentGCThread::safepoint_synchronize(); |
54 } | |
55 #endif // SERIALGC | |
56 | |
57 // By getting the Threads_lock, we assure that no threads are about to start or | |
58 // exit. It is released again in SafepointSynchronize::end(). | |
59 Threads_lock->lock(); | |
60 | |
61 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state"); | |
62 | |
63 int nof_threads = Threads::number_of_threads(); | |
64 | |
65 if (TraceSafepoint) { | |
66 tty->print_cr("Safepoint synchronization initiated. (%d)", nof_threads); | |
67 } | |
68 | |
69 RuntimeService::record_safepoint_begin(); | |
70 | |
71 { | |
72 MutexLocker mu(Safepoint_lock); | |
73 | |
74 // Set number of threads to wait for, before we initiate the callbacks | |
75 _waiting_to_block = nof_threads; | |
76 TryingToBlock = 0 ; | |
77 int still_running = nof_threads; | |
78 | |
79 // Save the starting time, so that it can be compared to see if this has taken | |
80 // too long to complete. | |
81 jlong safepoint_limit_time; | |
82 timeout_error_printed = false; | |
83 | |
1003 | 84 // PrintSafepointStatisticsTimeout can be specified separately. When |
85 // specified, PrintSafepointStatistics will be set to true in | |
86 // deferred_initialize_stat method. The initialization has to be done | |
87 // early enough to avoid any races. See bug 6880029 for details. | |
88 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) { | |
89 deferred_initialize_stat(); | |
90 } | |
91 | |
0 | 92 // Begin the process of bringing the system to a safepoint. |
93 // Java threads can be in several different states and are | |
94 // stopped by different mechanisms: | |
95 // | |
96 // 1. Running interpreted | |
97 // The interpeter dispatch table is changed to force it to | |
98 // check for a safepoint condition between bytecodes. | |
99 // 2. Running in native code | |
100 // When returning from the native code, a Java thread must check | |
101 // the safepoint _state to see if we must block. If the | |
102 // VM thread sees a Java thread in native, it does | |
103 // not wait for this thread to block. The order of the memory | |
104 // writes and reads of both the safepoint state and the Java | |
105 // threads state is critical. In order to guarantee that the | |
106 // memory writes are serialized with respect to each other, | |
107 // the VM thread issues a memory barrier instruction | |
108 // (on MP systems). In order to avoid the overhead of issuing | |
109 // a memory barrier for each Java thread making native calls, each Java | |
110 // thread performs a write to a single memory page after changing | |
111 // the thread state. The VM thread performs a sequence of | |
112 // mprotect OS calls which forces all previous writes from all | |
113 // Java threads to be serialized. This is done in the | |
114 // os::serialize_thread_states() call. This has proven to be | |
115 // much more efficient than executing a membar instruction | |
116 // on every call to native code. | |
117 // 3. Running compiled Code | |
118 // Compiled code reads a global (Safepoint Polling) page that | |
119 // is set to fault if we are trying to get to a safepoint. | |
120 // 4. Blocked | |
121 // A thread which is blocked will not be allowed to return from the | |
122 // block condition until the safepoint operation is complete. | |
123 // 5. In VM or Transitioning between states | |
124 // If a Java thread is currently running in the VM or transitioning | |
125 // between states, the safepointing code will wait for the thread to | |
126 // block itself when it attempts transitions to a new state. | |
127 // | |
128 _state = _synchronizing; | |
129 OrderAccess::fence(); | |
130 | |
131 // Flush all thread states to memory | |
132 if (!UseMembar) { | |
133 os::serialize_thread_states(); | |
134 } | |
135 | |
136 // Make interpreter safepoint aware | |
137 Interpreter::notice_safepoints(); | |
138 | |
139 if (UseCompilerSafepoints && DeferPollingPageLoopCount < 0) { | |
140 // Make polling safepoint aware | |
141 guarantee (PageArmed == 0, "invariant") ; | |
142 PageArmed = 1 ; | |
143 os::make_polling_page_unreadable(); | |
144 } | |
145 | |
146 // Consider using active_processor_count() ... but that call is expensive. | |
147 int ncpus = os::processor_count() ; | |
148 | |
149 #ifdef ASSERT | |
150 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) { | |
151 assert(cur->safepoint_state()->is_running(), "Illegal initial state"); | |
152 } | |
153 #endif // ASSERT | |
154 | |
155 if (SafepointTimeout) | |
156 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS; | |
157 | |
158 // Iterate through all threads until it have been determined how to stop them all at a safepoint | |
159 unsigned int iterations = 0; | |
160 int steps = 0 ; | |
161 while(still_running > 0) { | |
162 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) { | |
163 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended"); | |
164 ThreadSafepointState *cur_state = cur->safepoint_state(); | |
165 if (cur_state->is_running()) { | |
166 cur_state->examine_state_of_thread(); | |
167 if (!cur_state->is_running()) { | |
168 still_running--; | |
169 // consider adjusting steps downward: | |
170 // steps = 0 | |
171 // steps -= NNN | |
172 // steps >>= 1 | |
173 // steps = MIN(steps, 2000-100) | |
174 // if (iterations != 0) steps -= NNN | |
175 } | |
176 if (TraceSafepoint && Verbose) cur_state->print(); | |
177 } | |
178 } | |
179 | |
1003 | 180 if (PrintSafepointStatistics && iterations == 0) { |
0 | 181 begin_statistics(nof_threads, still_running); |
182 } | |
183 | |
184 if (still_running > 0) { | |
185 // Check for if it takes to long | |
186 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) { | |
187 print_safepoint_timeout(_spinning_timeout); | |
188 } | |
189 | |
190 // Spin to avoid context switching. | |
191 // There's a tension between allowing the mutators to run (and rendezvous) | |
192 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that | |
193 // a mutator might otherwise use profitably to reach a safepoint. Excessive | |
194 // spinning by the VM thread on a saturated system can increase rendezvous latency. | |
195 // Blocking or yielding incur their own penalties in the form of context switching | |
196 // and the resultant loss of $ residency. | |
197 // | |
198 // Further complicating matters is that yield() does not work as naively expected | |
199 // on many platforms -- yield() does not guarantee that any other ready threads | |
200 // will run. As such we revert yield_all() after some number of iterations. | |
201 // Yield_all() is implemented as a short unconditional sleep on some platforms. | |
202 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping | |
203 // can actually increase the time it takes the VM thread to detect that a system-wide | |
204 // stop-the-world safepoint has been reached. In a pathological scenario such as that | |
205 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe. | |
206 // In that case the mutators will be stalled waiting for the safepoint to complete and the | |
207 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread | |
208 // will eventually wake up and detect that all mutators are safe, at which point | |
209 // we'll again make progress. | |
210 // | |
211 // Beware too that that the VMThread typically runs at elevated priority. | |
212 // Its default priority is higher than the default mutator priority. | |
213 // Obviously, this complicates spinning. | |
214 // | |
215 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0). | |
216 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will. | |
217 // | |
218 // See the comments in synchronizer.cpp for additional remarks on spinning. | |
219 // | |
220 // In the future we might: | |
221 // 1. Modify the safepoint scheme to avoid potentally unbounded spinning. | |
222 // This is tricky as the path used by a thread exiting the JVM (say on | |
223 // on JNI call-out) simply stores into its state field. The burden | |
224 // is placed on the VM thread, which must poll (spin). | |
225 // 2. Find something useful to do while spinning. If the safepoint is GC-related | |
226 // we might aggressively scan the stacks of threads that are already safe. | |
227 // 3. Use Solaris schedctl to examine the state of the still-running mutators. | |
228 // If all the mutators are ONPROC there's no reason to sleep or yield. | |
229 // 4. YieldTo() any still-running mutators that are ready but OFFPROC. | |
230 // 5. Check system saturation. If the system is not fully saturated then | |
231 // simply spin and avoid sleep/yield. | |
232 // 6. As still-running mutators rendezvous they could unpark the sleeping | |
233 // VMthread. This works well for still-running mutators that become | |
234 // safe. The VMthread must still poll for mutators that call-out. | |
235 // 7. Drive the policy on time-since-begin instead of iterations. | |
236 // 8. Consider making the spin duration a function of the # of CPUs: | |
237 // Spin = (((ncpus-1) * M) + K) + F(still_running) | |
238 // Alternately, instead of counting iterations of the outer loop | |
239 // we could count the # of threads visited in the inner loop, above. | |
240 // 9. On windows consider using the return value from SwitchThreadTo() | |
241 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions. | |
242 | |
243 if (UseCompilerSafepoints && int(iterations) == DeferPollingPageLoopCount) { | |
244 guarantee (PageArmed == 0, "invariant") ; | |
245 PageArmed = 1 ; | |
246 os::make_polling_page_unreadable(); | |
247 } | |
248 | |
249 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or | |
250 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus) | |
251 ++steps ; | |
252 if (ncpus > 1 && steps < SafepointSpinBeforeYield) { | |
253 SpinPause() ; // MP-Polite spin | |
254 } else | |
255 if (steps < DeferThrSuspendLoopCount) { | |
256 os::NakedYield() ; | |
257 } else { | |
258 os::yield_all(steps) ; | |
259 // Alternately, the VM thread could transiently depress its scheduling priority or | |
260 // transiently increase the priority of the tardy mutator(s). | |
261 } | |
262 | |
263 iterations ++ ; | |
264 } | |
265 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long"); | |
266 } | |
267 assert(still_running == 0, "sanity check"); | |
268 | |
269 if (PrintSafepointStatistics) { | |
270 update_statistics_on_spin_end(); | |
271 } | |
272 | |
273 // wait until all threads are stopped | |
274 while (_waiting_to_block > 0) { | |
275 if (TraceSafepoint) tty->print_cr("Waiting for %d thread(s) to block", _waiting_to_block); | |
276 if (!SafepointTimeout || timeout_error_printed) { | |
277 Safepoint_lock->wait(true); // true, means with no safepoint checks | |
278 } else { | |
279 // Compute remaining time | |
280 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos(); | |
281 | |
282 // If there is no remaining time, then there is an error | |
283 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) { | |
284 print_safepoint_timeout(_blocking_timeout); | |
285 } | |
286 } | |
287 } | |
288 assert(_waiting_to_block == 0, "sanity check"); | |
289 | |
290 #ifndef PRODUCT | |
291 if (SafepointTimeout) { | |
292 jlong current_time = os::javaTimeNanos(); | |
293 if (safepoint_limit_time < current_time) { | |
294 tty->print_cr("# SafepointSynchronize: Finished after " | |
295 INT64_FORMAT_W(6) " ms", | |
296 ((current_time - safepoint_limit_time) / MICROUNITS + | |
297 SafepointTimeoutDelay)); | |
298 } | |
299 } | |
300 #endif | |
301 | |
302 assert((_safepoint_counter & 0x1) == 0, "must be even"); | |
303 assert(Threads_lock->owned_by_self(), "must hold Threads_lock"); | |
304 _safepoint_counter ++; | |
305 | |
306 // Record state | |
307 _state = _synchronized; | |
308 | |
309 OrderAccess::fence(); | |
310 | |
311 if (TraceSafepoint) { | |
312 VM_Operation *op = VMThread::vm_operation(); | |
313 tty->print_cr("Entering safepoint region: %s", (op != NULL) ? op->name() : "no vm operation"); | |
314 } | |
315 | |
316 RuntimeService::record_safepoint_synchronized(); | |
317 if (PrintSafepointStatistics) { | |
318 update_statistics_on_sync_end(os::javaTimeNanos()); | |
319 } | |
320 | |
321 // Call stuff that needs to be run when a safepoint is just about to be completed | |
322 do_cleanup_tasks(); | |
323 } | |
324 } | |
325 | |
326 // Wake up all threads, so they are ready to resume execution after the safepoint | |
327 // operation has been carried out | |
328 void SafepointSynchronize::end() { | |
329 | |
330 assert(Threads_lock->owned_by_self(), "must hold Threads_lock"); | |
331 assert((_safepoint_counter & 0x1) == 1, "must be odd"); | |
332 _safepoint_counter ++; | |
333 // memory fence isn't required here since an odd _safepoint_counter | |
334 // value can do no harm and a fence is issued below anyway. | |
335 | |
336 DEBUG_ONLY(Thread* myThread = Thread::current();) | |
337 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint"); | |
338 | |
339 if (PrintSafepointStatistics) { | |
340 end_statistics(os::javaTimeNanos()); | |
341 } | |
342 | |
343 #ifdef ASSERT | |
344 // A pending_exception cannot be installed during a safepoint. The threads | |
345 // may install an async exception after they come back from a safepoint into | |
346 // pending_exception after they unblock. But that should happen later. | |
347 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) { | |
348 assert (!(cur->has_pending_exception() && | |
349 cur->safepoint_state()->is_at_poll_safepoint()), | |
350 "safepoint installed a pending exception"); | |
351 } | |
352 #endif // ASSERT | |
353 | |
354 if (PageArmed) { | |
355 // Make polling safepoint aware | |
356 os::make_polling_page_readable(); | |
357 PageArmed = 0 ; | |
358 } | |
359 | |
360 // Remove safepoint check from interpreter | |
361 Interpreter::ignore_safepoints(); | |
362 | |
363 { | |
364 MutexLocker mu(Safepoint_lock); | |
365 | |
366 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization"); | |
367 | |
368 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method | |
369 // when they get restarted. | |
370 _state = _not_synchronized; | |
371 OrderAccess::fence(); | |
372 | |
373 if (TraceSafepoint) { | |
374 tty->print_cr("Leaving safepoint region"); | |
375 } | |
376 | |
377 // Start suspended threads | |
378 for(JavaThread *current = Threads::first(); current; current = current->next()) { | |
605 | 379 // A problem occurring on Solaris is when attempting to restart threads |
0 | 380 // the first #cpus - 1 go well, but then the VMThread is preempted when we get |
381 // to the next one (since it has been running the longest). We then have | |
382 // to wait for a cpu to become available before we can continue restarting | |
383 // threads. | |
384 // FIXME: This causes the performance of the VM to degrade when active and with | |
385 // large numbers of threads. Apparently this is due to the synchronous nature | |
386 // of suspending threads. | |
387 // | |
388 // TODO-FIXME: the comments above are vestigial and no longer apply. | |
389 // Furthermore, using solaris' schedctl in this particular context confers no benefit | |
390 if (VMThreadHintNoPreempt) { | |
391 os::hint_no_preempt(); | |
392 } | |
393 ThreadSafepointState* cur_state = current->safepoint_state(); | |
394 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint"); | |
395 cur_state->restart(); | |
396 assert(cur_state->is_running(), "safepoint state has not been reset"); | |
397 } | |
398 | |
399 RuntimeService::record_safepoint_end(); | |
400 | |
401 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads | |
402 // blocked in signal_thread_blocked | |
403 Threads_lock->unlock(); | |
404 | |
405 } | |
406 #ifndef SERIALGC | |
407 // If there are any concurrent GC threads resume them. | |
408 if (UseConcMarkSweepGC) { | |
409 ConcurrentMarkSweepThread::desynchronize(false); | |
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410 } else if (UseG1GC) { |
0 | 411 ConcurrentGCThread::safepoint_desynchronize(); |
412 } | |
413 #endif // SERIALGC | |
414 } | |
415 | |
416 bool SafepointSynchronize::is_cleanup_needed() { | |
417 // Need a safepoint if some inline cache buffers is non-empty | |
418 if (!InlineCacheBuffer::is_empty()) return true; | |
419 return false; | |
420 } | |
421 | |
422 jlong CounterDecay::_last_timestamp = 0; | |
423 | |
424 static void do_method(methodOop m) { | |
425 m->invocation_counter()->decay(); | |
426 } | |
427 | |
428 void CounterDecay::decay() { | |
429 _last_timestamp = os::javaTimeMillis(); | |
430 | |
431 // This operation is going to be performed only at the end of a safepoint | |
432 // and hence GC's will not be going on, all Java mutators are suspended | |
433 // at this point and hence SystemDictionary_lock is also not needed. | |
434 assert(SafepointSynchronize::is_at_safepoint(), "can only be executed at a safepoint"); | |
435 int nclasses = SystemDictionary::number_of_classes(); | |
436 double classes_per_tick = nclasses * (CounterDecayMinIntervalLength * 1e-3 / | |
437 CounterHalfLifeTime); | |
438 for (int i = 0; i < classes_per_tick; i++) { | |
439 klassOop k = SystemDictionary::try_get_next_class(); | |
440 if (k != NULL && k->klass_part()->oop_is_instance()) { | |
441 instanceKlass::cast(k)->methods_do(do_method); | |
442 } | |
443 } | |
444 } | |
445 | |
446 // Various cleaning tasks that should be done periodically at safepoints | |
447 void SafepointSynchronize::do_cleanup_tasks() { | |
448 jlong cleanup_time; | |
449 | |
450 // Update fat-monitor pool, since this is a safepoint. | |
451 if (TraceSafepoint) { | |
452 cleanup_time = os::javaTimeNanos(); | |
453 } | |
454 | |
455 ObjectSynchronizer::deflate_idle_monitors(); | |
456 InlineCacheBuffer::update_inline_caches(); | |
457 if(UseCounterDecay && CounterDecay::is_decay_needed()) { | |
458 CounterDecay::decay(); | |
459 } | |
460 NMethodSweeper::sweep(); | |
461 | |
462 if (TraceSafepoint) { | |
463 tty->print_cr("do_cleanup_tasks takes "INT64_FORMAT_W(6) "ms", | |
464 (os::javaTimeNanos() - cleanup_time) / MICROUNITS); | |
465 } | |
466 } | |
467 | |
468 | |
469 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) { | |
470 switch(state) { | |
471 case _thread_in_native: | |
472 // native threads are safe if they have no java stack or have walkable stack | |
473 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable(); | |
474 | |
475 // blocked threads should have already have walkable stack | |
476 case _thread_blocked: | |
477 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable"); | |
478 return true; | |
479 | |
480 default: | |
481 return false; | |
482 } | |
483 } | |
484 | |
485 | |
486 // ------------------------------------------------------------------------------------------------------- | |
487 // Implementation of Safepoint callback point | |
488 | |
489 void SafepointSynchronize::block(JavaThread *thread) { | |
490 assert(thread != NULL, "thread must be set"); | |
491 assert(thread->is_Java_thread(), "not a Java thread"); | |
492 | |
493 // Threads shouldn't block if they are in the middle of printing, but... | |
494 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id()); | |
495 | |
496 // Only bail from the block() call if the thread is gone from the | |
497 // thread list; starting to exit should still block. | |
498 if (thread->is_terminated()) { | |
499 // block current thread if we come here from native code when VM is gone | |
500 thread->block_if_vm_exited(); | |
501 | |
502 // otherwise do nothing | |
503 return; | |
504 } | |
505 | |
506 JavaThreadState state = thread->thread_state(); | |
507 thread->frame_anchor()->make_walkable(thread); | |
508 | |
509 // Check that we have a valid thread_state at this point | |
510 switch(state) { | |
511 case _thread_in_vm_trans: | |
512 case _thread_in_Java: // From compiled code | |
513 | |
514 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case, | |
515 // we pretend we are still in the VM. | |
516 thread->set_thread_state(_thread_in_vm); | |
517 | |
518 if (is_synchronizing()) { | |
519 Atomic::inc (&TryingToBlock) ; | |
520 } | |
521 | |
522 // We will always be holding the Safepoint_lock when we are examine the state | |
523 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and | |
524 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code | |
525 Safepoint_lock->lock_without_safepoint_check(); | |
526 if (is_synchronizing()) { | |
527 // Decrement the number of threads to wait for and signal vm thread | |
528 assert(_waiting_to_block > 0, "sanity check"); | |
529 _waiting_to_block--; | |
530 thread->safepoint_state()->set_has_called_back(true); | |
531 | |
532 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread | |
533 if (_waiting_to_block == 0) { | |
534 Safepoint_lock->notify_all(); | |
535 } | |
536 } | |
537 | |
538 // We transition the thread to state _thread_blocked here, but | |
539 // we can't do our usual check for external suspension and then | |
540 // self-suspend after the lock_without_safepoint_check() call | |
541 // below because we are often called during transitions while | |
542 // we hold different locks. That would leave us suspended while | |
543 // holding a resource which results in deadlocks. | |
544 thread->set_thread_state(_thread_blocked); | |
545 Safepoint_lock->unlock(); | |
546 | |
547 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during | |
548 // the entire safepoint, the threads will all line up here during the safepoint. | |
549 Threads_lock->lock_without_safepoint_check(); | |
550 // restore original state. This is important if the thread comes from compiled code, so it | |
551 // will continue to execute with the _thread_in_Java state. | |
552 thread->set_thread_state(state); | |
553 Threads_lock->unlock(); | |
554 break; | |
555 | |
556 case _thread_in_native_trans: | |
557 case _thread_blocked_trans: | |
558 case _thread_new_trans: | |
559 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) { | |
560 thread->print_thread_state(); | |
561 fatal("Deadlock in safepoint code. " | |
562 "Should have called back to the VM before blocking."); | |
563 } | |
564 | |
565 // We transition the thread to state _thread_blocked here, but | |
566 // we can't do our usual check for external suspension and then | |
567 // self-suspend after the lock_without_safepoint_check() call | |
568 // below because we are often called during transitions while | |
569 // we hold different locks. That would leave us suspended while | |
570 // holding a resource which results in deadlocks. | |
571 thread->set_thread_state(_thread_blocked); | |
572 | |
573 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence, | |
574 // the safepoint code might still be waiting for it to block. We need to change the state here, | |
575 // so it can see that it is at a safepoint. | |
576 | |
577 // Block until the safepoint operation is completed. | |
578 Threads_lock->lock_without_safepoint_check(); | |
579 | |
580 // Restore state | |
581 thread->set_thread_state(state); | |
582 | |
583 Threads_lock->unlock(); | |
584 break; | |
585 | |
586 default: | |
587 fatal1("Illegal threadstate encountered: %d", state); | |
588 } | |
589 | |
590 // Check for pending. async. exceptions or suspends - except if the | |
591 // thread was blocked inside the VM. has_special_runtime_exit_condition() | |
592 // is called last since it grabs a lock and we only want to do that when | |
593 // we must. | |
594 // | |
595 // Note: we never deliver an async exception at a polling point as the | |
596 // compiler may not have an exception handler for it. The polling | |
597 // code will notice the async and deoptimize and the exception will | |
598 // be delivered. (Polling at a return point is ok though). Sure is | |
599 // a lot of bother for a deprecated feature... | |
600 // | |
601 // We don't deliver an async exception if the thread state is | |
602 // _thread_in_native_trans so JNI functions won't be called with | |
603 // a surprising pending exception. If the thread state is going back to java, | |
604 // async exception is checked in check_special_condition_for_native_trans(). | |
605 | |
606 if (state != _thread_blocked_trans && | |
607 state != _thread_in_vm_trans && | |
608 thread->has_special_runtime_exit_condition()) { | |
609 thread->handle_special_runtime_exit_condition( | |
610 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans)); | |
611 } | |
612 } | |
613 | |
614 // ------------------------------------------------------------------------------------------------------ | |
615 // Exception handlers | |
616 | |
617 #ifndef PRODUCT | |
618 #ifdef _LP64 | |
619 #define PTR_PAD "" | |
620 #else | |
621 #define PTR_PAD " " | |
622 #endif | |
623 | |
624 static void print_ptrs(intptr_t oldptr, intptr_t newptr, bool wasoop) { | |
625 bool is_oop = newptr ? ((oop)newptr)->is_oop() : false; | |
626 tty->print_cr(PTR_FORMAT PTR_PAD " %s %c " PTR_FORMAT PTR_PAD " %s %s", | |
627 oldptr, wasoop?"oop":" ", oldptr == newptr ? ' ' : '!', | |
628 newptr, is_oop?"oop":" ", (wasoop && !is_oop) ? "STALE" : ((wasoop==false&&is_oop==false&&oldptr !=newptr)?"STOMP":" ")); | |
629 } | |
630 | |
631 static void print_longs(jlong oldptr, jlong newptr, bool wasoop) { | |
632 bool is_oop = newptr ? ((oop)(intptr_t)newptr)->is_oop() : false; | |
633 tty->print_cr(PTR64_FORMAT " %s %c " PTR64_FORMAT " %s %s", | |
634 oldptr, wasoop?"oop":" ", oldptr == newptr ? ' ' : '!', | |
635 newptr, is_oop?"oop":" ", (wasoop && !is_oop) ? "STALE" : ((wasoop==false&&is_oop==false&&oldptr !=newptr)?"STOMP":" ")); | |
636 } | |
637 | |
638 #ifdef SPARC | |
639 static void print_me(intptr_t *new_sp, intptr_t *old_sp, bool *was_oops) { | |
640 #ifdef _LP64 | |
641 tty->print_cr("--------+------address-----+------before-----------+-------after----------+"); | |
642 const int incr = 1; // Increment to skip a long, in units of intptr_t | |
643 #else | |
644 tty->print_cr("--------+--address-+------before-----------+-------after----------+"); | |
645 const int incr = 2; // Increment to skip a long, in units of intptr_t | |
646 #endif | |
647 tty->print_cr("---SP---|"); | |
648 for( int i=0; i<16; i++ ) { | |
649 tty->print("blob %c%d |"PTR_FORMAT" ","LO"[i>>3],i&7,new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); } | |
650 tty->print_cr("--------|"); | |
651 for( int i1=0; i1<frame::memory_parameter_word_sp_offset-16; i1++ ) { | |
652 tty->print("argv pad|"PTR_FORMAT" ",new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); } | |
653 tty->print(" pad|"PTR_FORMAT" ",new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); | |
654 tty->print_cr("--------|"); | |
655 tty->print(" G1 |"PTR_FORMAT" ",new_sp); print_longs(*(jlong*)old_sp,*(jlong*)new_sp,was_oops[incr-1]); old_sp += incr; new_sp += incr; was_oops += incr; | |
656 tty->print(" G3 |"PTR_FORMAT" ",new_sp); print_longs(*(jlong*)old_sp,*(jlong*)new_sp,was_oops[incr-1]); old_sp += incr; new_sp += incr; was_oops += incr; | |
657 tty->print(" G4 |"PTR_FORMAT" ",new_sp); print_longs(*(jlong*)old_sp,*(jlong*)new_sp,was_oops[incr-1]); old_sp += incr; new_sp += incr; was_oops += incr; | |
658 tty->print(" G5 |"PTR_FORMAT" ",new_sp); print_longs(*(jlong*)old_sp,*(jlong*)new_sp,was_oops[incr-1]); old_sp += incr; new_sp += incr; was_oops += incr; | |
659 tty->print_cr(" FSR |"PTR_FORMAT" "PTR64_FORMAT" "PTR64_FORMAT,new_sp,*(jlong*)old_sp,*(jlong*)new_sp); | |
660 old_sp += incr; new_sp += incr; was_oops += incr; | |
661 // Skip the floats | |
662 tty->print_cr("--Float-|"PTR_FORMAT,new_sp); | |
663 tty->print_cr("---FP---|"); | |
664 old_sp += incr*32; new_sp += incr*32; was_oops += incr*32; | |
665 for( int i2=0; i2<16; i2++ ) { | |
666 tty->print("call %c%d |"PTR_FORMAT" ","LI"[i2>>3],i2&7,new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); } | |
667 tty->print_cr(""); | |
668 } | |
669 #endif // SPARC | |
670 #endif // PRODUCT | |
671 | |
672 | |
673 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) { | |
674 assert(thread->is_Java_thread(), "polling reference encountered by VM thread"); | |
675 assert(thread->thread_state() == _thread_in_Java, "should come from Java code"); | |
676 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization"); | |
677 | |
678 // Uncomment this to get some serious before/after printing of the | |
679 // Sparc safepoint-blob frame structure. | |
680 /* | |
681 intptr_t* sp = thread->last_Java_sp(); | |
682 intptr_t stack_copy[150]; | |
683 for( int i=0; i<150; i++ ) stack_copy[i] = sp[i]; | |
684 bool was_oops[150]; | |
685 for( int i=0; i<150; i++ ) | |
686 was_oops[i] = stack_copy[i] ? ((oop)stack_copy[i])->is_oop() : false; | |
687 */ | |
688 | |
689 if (ShowSafepointMsgs) { | |
690 tty->print("handle_polling_page_exception: "); | |
691 } | |
692 | |
693 if (PrintSafepointStatistics) { | |
694 inc_page_trap_count(); | |
695 } | |
696 | |
697 ThreadSafepointState* state = thread->safepoint_state(); | |
698 | |
699 state->handle_polling_page_exception(); | |
700 // print_me(sp,stack_copy,was_oops); | |
701 } | |
702 | |
703 | |
704 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) { | |
705 if (!timeout_error_printed) { | |
706 timeout_error_printed = true; | |
707 // Print out the thread infor which didn't reach the safepoint for debugging | |
708 // purposes (useful when there are lots of threads in the debugger). | |
709 tty->print_cr(""); | |
710 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:"); | |
711 if (reason == _spinning_timeout) { | |
712 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint."); | |
713 } else if (reason == _blocking_timeout) { | |
714 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop."); | |
715 } | |
716 | |
717 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:"); | |
718 ThreadSafepointState *cur_state; | |
719 ResourceMark rm; | |
720 for(JavaThread *cur_thread = Threads::first(); cur_thread; | |
721 cur_thread = cur_thread->next()) { | |
722 cur_state = cur_thread->safepoint_state(); | |
723 | |
724 if (cur_thread->thread_state() != _thread_blocked && | |
725 ((reason == _spinning_timeout && cur_state->is_running()) || | |
726 (reason == _blocking_timeout && !cur_state->has_called_back()))) { | |
727 tty->print("# "); | |
728 cur_thread->print(); | |
729 tty->print_cr(""); | |
730 } | |
731 } | |
732 tty->print_cr("# SafepointSynchronize::begin: (End of list)"); | |
733 } | |
734 | |
735 // To debug the long safepoint, specify both DieOnSafepointTimeout & | |
736 // ShowMessageBoxOnError. | |
737 if (DieOnSafepointTimeout) { | |
738 char msg[1024]; | |
739 VM_Operation *op = VMThread::vm_operation(); | |
513
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740 sprintf(msg, "Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.", |
0 | 741 SafepointTimeoutDelay, |
742 op != NULL ? op->name() : "no vm operation"); | |
743 fatal(msg); | |
744 } | |
745 } | |
746 | |
747 | |
748 // ------------------------------------------------------------------------------------------------------- | |
749 // Implementation of ThreadSafepointState | |
750 | |
751 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) { | |
752 _thread = thread; | |
753 _type = _running; | |
754 _has_called_back = false; | |
755 _at_poll_safepoint = false; | |
756 } | |
757 | |
758 void ThreadSafepointState::create(JavaThread *thread) { | |
759 ThreadSafepointState *state = new ThreadSafepointState(thread); | |
760 thread->set_safepoint_state(state); | |
761 } | |
762 | |
763 void ThreadSafepointState::destroy(JavaThread *thread) { | |
764 if (thread->safepoint_state()) { | |
765 delete(thread->safepoint_state()); | |
766 thread->set_safepoint_state(NULL); | |
767 } | |
768 } | |
769 | |
770 void ThreadSafepointState::examine_state_of_thread() { | |
771 assert(is_running(), "better be running or just have hit safepoint poll"); | |
772 | |
773 JavaThreadState state = _thread->thread_state(); | |
774 | |
775 // Check for a thread that is suspended. Note that thread resume tries | |
776 // to grab the Threads_lock which we own here, so a thread cannot be | |
777 // resumed during safepoint synchronization. | |
778 | |
979 | 779 // We check to see if this thread is suspended without locking to |
780 // avoid deadlocking with a third thread that is waiting for this | |
781 // thread to be suspended. The third thread can notice the safepoint | |
782 // that we're trying to start at the beginning of its SR_lock->wait() | |
783 // call. If that happens, then the third thread will block on the | |
784 // safepoint while still holding the underlying SR_lock. We won't be | |
785 // able to get the SR_lock and we'll deadlock. | |
786 // | |
787 // We don't need to grab the SR_lock here for two reasons: | |
788 // 1) The suspend flags are both volatile and are set with an | |
789 // Atomic::cmpxchg() call so we should see the suspended | |
790 // state right away. | |
791 // 2) We're being called from the safepoint polling loop; if | |
792 // we don't see the suspended state on this iteration, then | |
793 // we'll come around again. | |
794 // | |
795 bool is_suspended = _thread->is_ext_suspended(); | |
0 | 796 if (is_suspended) { |
797 roll_forward(_at_safepoint); | |
798 return; | |
799 } | |
800 | |
801 // Some JavaThread states have an initial safepoint state of | |
802 // running, but are actually at a safepoint. We will happily | |
803 // agree and update the safepoint state here. | |
804 if (SafepointSynchronize::safepoint_safe(_thread, state)) { | |
805 roll_forward(_at_safepoint); | |
806 return; | |
807 } | |
808 | |
809 if (state == _thread_in_vm) { | |
810 roll_forward(_call_back); | |
811 return; | |
812 } | |
813 | |
814 // All other thread states will continue to run until they | |
815 // transition and self-block in state _blocked | |
816 // Safepoint polling in compiled code causes the Java threads to do the same. | |
817 // Note: new threads may require a malloc so they must be allowed to finish | |
818 | |
819 assert(is_running(), "examine_state_of_thread on non-running thread"); | |
820 return; | |
821 } | |
822 | |
823 // Returns true is thread could not be rolled forward at present position. | |
824 void ThreadSafepointState::roll_forward(suspend_type type) { | |
825 _type = type; | |
826 | |
827 switch(_type) { | |
828 case _at_safepoint: | |
829 SafepointSynchronize::signal_thread_at_safepoint(); | |
830 break; | |
831 | |
832 case _call_back: | |
833 set_has_called_back(false); | |
834 break; | |
835 | |
836 case _running: | |
837 default: | |
838 ShouldNotReachHere(); | |
839 } | |
840 } | |
841 | |
842 void ThreadSafepointState::restart() { | |
843 switch(type()) { | |
844 case _at_safepoint: | |
845 case _call_back: | |
846 break; | |
847 | |
848 case _running: | |
849 default: | |
850 tty->print_cr("restart thread "INTPTR_FORMAT" with state %d", | |
851 _thread, _type); | |
852 _thread->print(); | |
853 ShouldNotReachHere(); | |
854 } | |
855 _type = _running; | |
856 set_has_called_back(false); | |
857 } | |
858 | |
859 | |
860 void ThreadSafepointState::print_on(outputStream *st) const { | |
861 const char *s; | |
862 | |
863 switch(_type) { | |
864 case _running : s = "_running"; break; | |
865 case _at_safepoint : s = "_at_safepoint"; break; | |
866 case _call_back : s = "_call_back"; break; | |
867 default: | |
868 ShouldNotReachHere(); | |
869 } | |
870 | |
871 st->print_cr("Thread: " INTPTR_FORMAT | |
872 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d", | |
873 _thread, _thread->osthread()->thread_id(), s, _has_called_back, | |
874 _at_poll_safepoint); | |
875 | |
876 _thread->print_thread_state_on(st); | |
877 } | |
878 | |
879 | |
880 // --------------------------------------------------------------------------------------------------------------------- | |
881 | |
882 // Block the thread at the safepoint poll or poll return. | |
883 void ThreadSafepointState::handle_polling_page_exception() { | |
884 | |
885 // Check state. block() will set thread state to thread_in_vm which will | |
886 // cause the safepoint state _type to become _call_back. | |
887 assert(type() == ThreadSafepointState::_running, | |
888 "polling page exception on thread not running state"); | |
889 | |
890 // Step 1: Find the nmethod from the return address | |
891 if (ShowSafepointMsgs && Verbose) { | |
892 tty->print_cr("Polling page exception at " INTPTR_FORMAT, thread()->saved_exception_pc()); | |
893 } | |
894 address real_return_addr = thread()->saved_exception_pc(); | |
895 | |
896 CodeBlob *cb = CodeCache::find_blob(real_return_addr); | |
897 assert(cb != NULL && cb->is_nmethod(), "return address should be in nmethod"); | |
898 nmethod* nm = (nmethod*)cb; | |
899 | |
900 // Find frame of caller | |
901 frame stub_fr = thread()->last_frame(); | |
902 CodeBlob* stub_cb = stub_fr.cb(); | |
903 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub"); | |
904 RegisterMap map(thread(), true); | |
905 frame caller_fr = stub_fr.sender(&map); | |
906 | |
907 // Should only be poll_return or poll | |
908 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" ); | |
909 | |
910 // This is a poll immediately before a return. The exception handling code | |
911 // has already had the effect of causing the return to occur, so the execution | |
912 // will continue immediately after the call. In addition, the oopmap at the | |
913 // return point does not mark the return value as an oop (if it is), so | |
914 // it needs a handle here to be updated. | |
915 if( nm->is_at_poll_return(real_return_addr) ) { | |
916 // See if return type is an oop. | |
917 bool return_oop = nm->method()->is_returning_oop(); | |
918 Handle return_value; | |
919 if (return_oop) { | |
920 // The oop result has been saved on the stack together with all | |
921 // the other registers. In order to preserve it over GCs we need | |
922 // to keep it in a handle. | |
923 oop result = caller_fr.saved_oop_result(&map); | |
924 assert(result == NULL || result->is_oop(), "must be oop"); | |
925 return_value = Handle(thread(), result); | |
926 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer"); | |
927 } | |
928 | |
929 // Block the thread | |
930 SafepointSynchronize::block(thread()); | |
931 | |
932 // restore oop result, if any | |
933 if (return_oop) { | |
934 caller_fr.set_saved_oop_result(&map, return_value()); | |
935 } | |
936 } | |
937 | |
938 // This is a safepoint poll. Verify the return address and block. | |
939 else { | |
940 set_at_poll_safepoint(true); | |
941 | |
942 // verify the blob built the "return address" correctly | |
943 assert(real_return_addr == caller_fr.pc(), "must match"); | |
944 | |
945 // Block the thread | |
946 SafepointSynchronize::block(thread()); | |
947 set_at_poll_safepoint(false); | |
948 | |
949 // If we have a pending async exception deoptimize the frame | |
950 // as otherwise we may never deliver it. | |
951 if (thread()->has_async_condition()) { | |
952 ThreadInVMfromJavaNoAsyncException __tiv(thread()); | |
953 VM_DeoptimizeFrame deopt(thread(), caller_fr.id()); | |
954 VMThread::execute(&deopt); | |
955 } | |
956 | |
957 // If an exception has been installed we must check for a pending deoptimization | |
958 // Deoptimize frame if exception has been thrown. | |
959 | |
960 if (thread()->has_pending_exception() ) { | |
961 RegisterMap map(thread(), true); | |
962 frame caller_fr = stub_fr.sender(&map); | |
963 if (caller_fr.is_deoptimized_frame()) { | |
964 // The exception patch will destroy registers that are still | |
965 // live and will be needed during deoptimization. Defer the | |
966 // Async exception should have defered the exception until the | |
967 // next safepoint which will be detected when we get into | |
968 // the interpreter so if we have an exception now things | |
969 // are messed up. | |
970 | |
971 fatal("Exception installed and deoptimization is pending"); | |
972 } | |
973 } | |
974 } | |
975 } | |
976 | |
977 | |
978 // | |
979 // Statistics & Instrumentations | |
980 // | |
981 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL; | |
982 int SafepointSynchronize::_cur_stat_index = 0; | |
983 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating]; | |
984 julong SafepointSynchronize::_coalesced_vmop_count = 0; | |
985 jlong SafepointSynchronize::_max_sync_time = 0; | |
986 | |
987 // last_safepoint_start_time records the start time of last safepoint. | |
988 static jlong last_safepoint_start_time = 0; | |
989 static jlong sync_end_time = 0; | |
990 static bool need_to_track_page_armed_status = false; | |
991 static bool init_done = false; | |
992 | |
993 void SafepointSynchronize::deferred_initialize_stat() { | |
994 if (init_done) return; | |
995 | |
996 if (PrintSafepointStatisticsCount <= 0) { | |
997 fatal("Wrong PrintSafepointStatisticsCount"); | |
998 } | |
999 | |
1000 // If PrintSafepointStatisticsTimeout is specified, the statistics data will | |
1001 // be printed right away, in which case, _safepoint_stats will regress to | |
1002 // a single element array. Otherwise, it is a circular ring buffer with default | |
1003 // size of PrintSafepointStatisticsCount. | |
1004 int stats_array_size; | |
1005 if (PrintSafepointStatisticsTimeout > 0) { | |
1006 stats_array_size = 1; | |
1007 PrintSafepointStatistics = true; | |
1008 } else { | |
1009 stats_array_size = PrintSafepointStatisticsCount; | |
1010 } | |
1011 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size | |
1012 * sizeof(SafepointStats)); | |
1013 guarantee(_safepoint_stats != NULL, | |
1014 "not enough memory for safepoint instrumentation data"); | |
1015 | |
1016 if (UseCompilerSafepoints && DeferPollingPageLoopCount >= 0) { | |
1017 need_to_track_page_armed_status = true; | |
1018 } | |
1019 | |
1020 tty->print(" vmop_name " | |
1021 "[threads: total initially_running wait_to_block] "); | |
1022 tty->print("[time: spin block sync] " | |
1023 "[vmop_time time_elapsed] "); | |
1024 | |
1025 // no page armed status printed out if it is always armed. | |
1026 if (need_to_track_page_armed_status) { | |
1027 tty->print("page_armed "); | |
1028 } | |
1029 | |
1030 tty->print_cr("page_trap_count"); | |
1031 | |
1032 init_done = true; | |
1033 } | |
1034 | |
1035 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) { | |
1003 | 1036 assert(init_done, "safepoint statistics array hasn't been initialized"); |
0 | 1037 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; |
1038 | |
1039 VM_Operation *op = VMThread::vm_operation(); | |
1040 spstat->_vmop_type = (op != NULL ? op->type() : -1); | |
1041 if (op != NULL) { | |
1042 _safepoint_reasons[spstat->_vmop_type]++; | |
1043 } | |
1044 | |
1045 spstat->_nof_total_threads = nof_threads; | |
1046 spstat->_nof_initial_running_threads = nof_running; | |
1047 spstat->_nof_threads_hit_page_trap = 0; | |
1048 | |
1049 // Records the start time of spinning. The real time spent on spinning | |
1050 // will be adjusted when spin is done. Same trick is applied for time | |
1051 // spent on waiting for threads to block. | |
1052 if (nof_running != 0) { | |
1053 spstat->_time_to_spin = os::javaTimeNanos(); | |
1054 } else { | |
1055 spstat->_time_to_spin = 0; | |
1056 } | |
1057 | |
1058 if (last_safepoint_start_time == 0) { | |
1059 spstat->_time_elapsed_since_last_safepoint = 0; | |
1060 } else { | |
1061 spstat->_time_elapsed_since_last_safepoint = _last_safepoint - | |
1062 last_safepoint_start_time; | |
1063 } | |
1064 last_safepoint_start_time = _last_safepoint; | |
1065 } | |
1066 | |
1067 void SafepointSynchronize::update_statistics_on_spin_end() { | |
1068 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; | |
1069 | |
1070 jlong cur_time = os::javaTimeNanos(); | |
1071 | |
1072 spstat->_nof_threads_wait_to_block = _waiting_to_block; | |
1073 if (spstat->_nof_initial_running_threads != 0) { | |
1074 spstat->_time_to_spin = cur_time - spstat->_time_to_spin; | |
1075 } | |
1076 | |
1077 if (need_to_track_page_armed_status) { | |
1078 spstat->_page_armed = (PageArmed == 1); | |
1079 } | |
1080 | |
1081 // Records the start time of waiting for to block. Updated when block is done. | |
1082 if (_waiting_to_block != 0) { | |
1083 spstat->_time_to_wait_to_block = cur_time; | |
1084 } else { | |
1085 spstat->_time_to_wait_to_block = 0; | |
1086 } | |
1087 } | |
1088 | |
1089 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) { | |
1090 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; | |
1091 | |
1092 if (spstat->_nof_threads_wait_to_block != 0) { | |
1093 spstat->_time_to_wait_to_block = end_time - | |
1094 spstat->_time_to_wait_to_block; | |
1095 } | |
1096 | |
1097 // Records the end time of sync which will be used to calculate the total | |
1098 // vm operation time. Again, the real time spending in syncing will be deducted | |
1099 // from the start of the sync time later when end_statistics is called. | |
1100 spstat->_time_to_sync = end_time - _last_safepoint; | |
1101 if (spstat->_time_to_sync > _max_sync_time) { | |
1102 _max_sync_time = spstat->_time_to_sync; | |
1103 } | |
1104 sync_end_time = end_time; | |
1105 } | |
1106 | |
1107 void SafepointSynchronize::end_statistics(jlong vmop_end_time) { | |
1108 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; | |
1109 | |
1110 // Update the vm operation time. | |
1111 spstat->_time_to_exec_vmop = vmop_end_time - sync_end_time; | |
1112 // Only the sync time longer than the specified | |
1113 // PrintSafepointStatisticsTimeout will be printed out right away. | |
1114 // By default, it is -1 meaning all samples will be put into the list. | |
1115 if ( PrintSafepointStatisticsTimeout > 0) { | |
1116 if (spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) { | |
1117 print_statistics(); | |
1118 } | |
1119 } else { | |
1120 // The safepoint statistics will be printed out when the _safepoin_stats | |
1121 // array fills up. | |
1122 if (_cur_stat_index != PrintSafepointStatisticsCount - 1) { | |
1123 _cur_stat_index ++; | |
1124 } else { | |
1125 print_statistics(); | |
1126 _cur_stat_index = 0; | |
1127 tty->print_cr(""); | |
1128 } | |
1129 } | |
1130 } | |
1131 | |
1132 void SafepointSynchronize::print_statistics() { | |
1133 int index; | |
1134 SafepointStats* sstats = _safepoint_stats; | |
1135 | |
1136 for (index = 0; index <= _cur_stat_index; index++) { | |
1137 sstats = &_safepoint_stats[index]; | |
1138 tty->print("%-28s [" | |
1139 INT32_FORMAT_W(8)INT32_FORMAT_W(11)INT32_FORMAT_W(15) | |
1140 "] ", | |
1141 sstats->_vmop_type == -1 ? "no vm operation" : | |
1142 VM_Operation::name(sstats->_vmop_type), | |
1143 sstats->_nof_total_threads, | |
1144 sstats->_nof_initial_running_threads, | |
1145 sstats->_nof_threads_wait_to_block); | |
1146 // "/ MICROUNITS " is to convert the unit from nanos to millis. | |
1147 tty->print(" [" | |
1148 INT64_FORMAT_W(6)INT64_FORMAT_W(6)INT64_FORMAT_W(6) | |
1149 "] " | |
1150 "["INT64_FORMAT_W(6)INT64_FORMAT_W(9) "] ", | |
1151 sstats->_time_to_spin / MICROUNITS, | |
1152 sstats->_time_to_wait_to_block / MICROUNITS, | |
1153 sstats->_time_to_sync / MICROUNITS, | |
1154 sstats->_time_to_exec_vmop / MICROUNITS, | |
1155 sstats->_time_elapsed_since_last_safepoint / MICROUNITS); | |
1156 | |
1157 if (need_to_track_page_armed_status) { | |
1158 tty->print(INT32_FORMAT" ", sstats->_page_armed); | |
1159 } | |
1160 tty->print_cr(INT32_FORMAT" ", sstats->_nof_threads_hit_page_trap); | |
1161 } | |
1162 } | |
1163 | |
1164 // This method will be called when VM exits. It will first call | |
1165 // print_statistics to print out the rest of the sampling. Then | |
1166 // it tries to summarize the sampling. | |
1167 void SafepointSynchronize::print_stat_on_exit() { | |
1168 if (_safepoint_stats == NULL) return; | |
1169 | |
1170 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; | |
1171 | |
1172 // During VM exit, end_statistics may not get called and in that | |
1173 // case, if the sync time is less than PrintSafepointStatisticsTimeout, | |
1174 // don't print it out. | |
1175 // Approximate the vm op time. | |
1176 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop = | |
1177 os::javaTimeNanos() - sync_end_time; | |
1178 | |
1179 if ( PrintSafepointStatisticsTimeout < 0 || | |
1180 spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) { | |
1181 print_statistics(); | |
1182 } | |
1183 tty->print_cr(""); | |
1184 | |
1185 // Print out polling page sampling status. | |
1186 if (!need_to_track_page_armed_status) { | |
1187 if (UseCompilerSafepoints) { | |
1188 tty->print_cr("Polling page always armed"); | |
1189 } | |
1190 } else { | |
1191 tty->print_cr("Defer polling page loop count = %d\n", | |
1192 DeferPollingPageLoopCount); | |
1193 } | |
1194 | |
1195 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) { | |
1196 if (_safepoint_reasons[index] != 0) { | |
1197 tty->print_cr("%-26s"UINT64_FORMAT_W(10), VM_Operation::name(index), | |
1198 _safepoint_reasons[index]); | |
1199 } | |
1200 } | |
1201 | |
1202 tty->print_cr(UINT64_FORMAT_W(5)" VM operations coalesced during safepoint", | |
1203 _coalesced_vmop_count); | |
1204 tty->print_cr("Maximum sync time "INT64_FORMAT_W(5)" ms", | |
1205 _max_sync_time / MICROUNITS); | |
1206 } | |
1207 | |
1208 // ------------------------------------------------------------------------------------------------ | |
1209 // Non-product code | |
1210 | |
1211 #ifndef PRODUCT | |
1212 | |
1213 void SafepointSynchronize::print_state() { | |
1214 if (_state == _not_synchronized) { | |
1215 tty->print_cr("not synchronized"); | |
1216 } else if (_state == _synchronizing || _state == _synchronized) { | |
1217 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" : | |
1218 "synchronized"); | |
1219 | |
1220 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) { | |
1221 cur->safepoint_state()->print(); | |
1222 } | |
1223 } | |
1224 } | |
1225 | |
1226 void SafepointSynchronize::safepoint_msg(const char* format, ...) { | |
1227 if (ShowSafepointMsgs) { | |
1228 va_list ap; | |
1229 va_start(ap, format); | |
1230 tty->vprint_cr(format, ap); | |
1231 va_end(ap); | |
1232 } | |
1233 } | |
1234 | |
1235 #endif // !PRODUCT |