1 /*
2 * Copyright (c) 1997, 2017, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "classfile/stringTable.hpp"
27 #include "classfile/symbolTable.hpp"
28 #include "classfile/systemDictionary.hpp"
29 #include "code/codeCache.hpp"
30 #include "code/icBuffer.hpp"
31 #include "code/nmethod.hpp"
32 #include "code/pcDesc.hpp"
33 #include "code/scopeDesc.hpp"
34 #include "gc/shared/collectedHeap.hpp"
35 #include "gc/shared/gcLocker.inline.hpp"
36 #include "gc/shared/strongRootsScope.hpp"
37 #include "gc/shared/workgroup.hpp"
38 #include "interpreter/interpreter.hpp"
39 #include "logging/log.hpp"
40 #include "logging/logStream.hpp"
41 #include "memory/resourceArea.hpp"
42 #include "memory/universe.inline.hpp"
43 #include "oops/oop.inline.hpp"
44 #include "oops/symbol.hpp"
45 #include "runtime/atomic.hpp"
46 #include "runtime/compilationPolicy.hpp"
47 #include "runtime/deoptimization.hpp"
48 #include "runtime/frame.inline.hpp"
49 #include "runtime/interfaceSupport.hpp"
50 #include "runtime/mutexLocker.hpp"
51 #include "runtime/orderAccess.inline.hpp"
52 #include "runtime/osThread.hpp"
53 #include "runtime/safepoint.hpp"
54 #include "runtime/signature.hpp"
55 #include "runtime/stubCodeGenerator.hpp"
56 #include "runtime/stubRoutines.hpp"
57 #include "runtime/sweeper.hpp"
58 #include "runtime/synchronizer.hpp"
59 #include "runtime/thread.inline.hpp"
60 #include "runtime/timerTrace.hpp"
61 #include "services/runtimeService.hpp"
62 #include "trace/tracing.hpp"
63 #include "trace/traceMacros.hpp"
64 #include "utilities/events.hpp"
65 #include "utilities/macros.hpp"
66 #if INCLUDE_ALL_GCS
67 #include "gc/shenandoah/shenandoahConcurrentThread.hpp"
68 #include "gc/cms/concurrentMarkSweepThread.hpp"
69 #include "gc/g1/suspendibleThreadSet.hpp"
70 #endif // INCLUDE_ALL_GCS
71 #ifdef COMPILER1
72 #include "c1/c1_globals.hpp"
73 #endif
74
75 // --------------------------------------------------------------------------------------------------
76 // Implementation of Safepoint begin/end
77
78 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
79 volatile int SafepointSynchronize::_waiting_to_block = 0;
80 volatile int SafepointSynchronize::_safepoint_counter = 0;
81 int SafepointSynchronize::_current_jni_active_count = 0;
82 long SafepointSynchronize::_end_of_last_safepoint = 0;
83 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE
84 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only
85 static bool timeout_error_printed = false;
86
87 // Roll all threads forward to a safepoint and suspend them all
88 void SafepointSynchronize::begin() {
89 EventSafepointBegin begin_event;
90 Thread* myThread = Thread::current();
91 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint");
92
93 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
94 _safepoint_begin_time = os::javaTimeNanos();
95 _ts_of_current_safepoint = tty->time_stamp().seconds();
96 }
97
98 #if INCLUDE_ALL_GCS
99 if (UseConcMarkSweepGC) {
100 // In the future we should investigate whether CMS can use the
101 // more-general mechanism below. DLD (01/05).
102 ConcurrentMarkSweepThread::synchronize(false);
103 } else if (UseG1GC || (UseShenandoahGC && ShenandoahSuspendibleWorkers)) {
104 SuspendibleThreadSet::synchronize();
105 }
106 #endif // INCLUDE_ALL_GCS
107
108 // By getting the Threads_lock, we assure that no threads are about to start or
109 // exit. It is released again in SafepointSynchronize::end().
110 Threads_lock->lock();
111
112 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
113
114 int nof_threads = Threads::number_of_threads();
115
116 log_debug(safepoint)("Safepoint synchronization initiated. (%d)", nof_threads);
117
118 RuntimeService::record_safepoint_begin();
119
120 MutexLocker mu(Safepoint_lock);
121
122 // Reset the count of active JNI critical threads
123 _current_jni_active_count = 0;
124
125 // Set number of threads to wait for, before we initiate the callbacks
126 _waiting_to_block = nof_threads;
127 TryingToBlock = 0 ;
128 int still_running = nof_threads;
129
130 // Save the starting time, so that it can be compared to see if this has taken
131 // too long to complete.
132 jlong safepoint_limit_time = 0;
133 timeout_error_printed = false;
134
135 // PrintSafepointStatisticsTimeout can be specified separately. When
136 // specified, PrintSafepointStatistics will be set to true in
137 // deferred_initialize_stat method. The initialization has to be done
138 // early enough to avoid any races. See bug 6880029 for details.
139 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
140 deferred_initialize_stat();
141 }
142
143 // Begin the process of bringing the system to a safepoint.
144 // Java threads can be in several different states and are
145 // stopped by different mechanisms:
146 //
147 // 1. Running interpreted
148 // The interpreter dispatch table is changed to force it to
149 // check for a safepoint condition between bytecodes.
150 // 2. Running in native code
151 // When returning from the native code, a Java thread must check
152 // the safepoint _state to see if we must block. If the
153 // VM thread sees a Java thread in native, it does
154 // not wait for this thread to block. The order of the memory
155 // writes and reads of both the safepoint state and the Java
156 // threads state is critical. In order to guarantee that the
157 // memory writes are serialized with respect to each other,
158 // the VM thread issues a memory barrier instruction
159 // (on MP systems). In order to avoid the overhead of issuing
160 // a memory barrier for each Java thread making native calls, each Java
161 // thread performs a write to a single memory page after changing
162 // the thread state. The VM thread performs a sequence of
163 // mprotect OS calls which forces all previous writes from all
164 // Java threads to be serialized. This is done in the
165 // os::serialize_thread_states() call. This has proven to be
166 // much more efficient than executing a membar instruction
167 // on every call to native code.
168 // 3. Running compiled Code
169 // Compiled code reads a global (Safepoint Polling) page that
170 // is set to fault if we are trying to get to a safepoint.
171 // 4. Blocked
172 // A thread which is blocked will not be allowed to return from the
173 // block condition until the safepoint operation is complete.
174 // 5. In VM or Transitioning between states
175 // If a Java thread is currently running in the VM or transitioning
176 // between states, the safepointing code will wait for the thread to
177 // block itself when it attempts transitions to a new state.
178 //
179 {
180 EventSafepointStateSynchronization sync_event;
181 int initial_running = 0;
182
183 _state = _synchronizing;
184 OrderAccess::fence();
185
186 // Flush all thread states to memory
187 if (!UseMembar) {
188 os::serialize_thread_states();
189 }
190
191 // Make interpreter safepoint aware
192 Interpreter::notice_safepoints();
193
194 if (DeferPollingPageLoopCount < 0) {
195 // Make polling safepoint aware
196 guarantee (PageArmed == 0, "invariant") ;
197 PageArmed = 1 ;
198 os::make_polling_page_unreadable();
199 }
200
201 // Consider using active_processor_count() ... but that call is expensive.
202 int ncpus = os::processor_count() ;
203
204 #ifdef ASSERT
205 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
206 assert(cur->safepoint_state()->is_running(), "Illegal initial state");
207 // Clear the visited flag to ensure that the critical counts are collected properly.
208 cur->set_visited_for_critical_count(false);
209 }
210 #endif // ASSERT
211
212 if (SafepointTimeout)
213 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
214
215 // Iterate through all threads until it have been determined how to stop them all at a safepoint
216 unsigned int iterations = 0;
217 int steps = 0 ;
218 while(still_running > 0) {
219 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
220 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
221 ThreadSafepointState *cur_state = cur->safepoint_state();
222 if (cur_state->is_running()) {
223 cur_state->examine_state_of_thread();
224 if (!cur_state->is_running()) {
225 still_running--;
226 // consider adjusting steps downward:
227 // steps = 0
228 // steps -= NNN
229 // steps >>= 1
230 // steps = MIN(steps, 2000-100)
231 // if (iterations != 0) steps -= NNN
232 }
233 LogTarget(Trace, safepoint) lt;
234 if (lt.is_enabled()) {
235 ResourceMark rm;
236 LogStream ls(lt);
237 cur_state->print_on(&ls);
238 }
239 }
240 }
241
242 if (iterations == 0) {
243 initial_running = still_running;
244 if (PrintSafepointStatistics) {
245 begin_statistics(nof_threads, still_running);
246 }
247 }
248
249 if (still_running > 0) {
250 // Check for if it takes to long
251 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
252 print_safepoint_timeout(_spinning_timeout);
253 }
254
255 // Spin to avoid context switching.
256 // There's a tension between allowing the mutators to run (and rendezvous)
257 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that
258 // a mutator might otherwise use profitably to reach a safepoint. Excessive
259 // spinning by the VM thread on a saturated system can increase rendezvous latency.
260 // Blocking or yielding incur their own penalties in the form of context switching
261 // and the resultant loss of $ residency.
262 //
263 // Further complicating matters is that yield() does not work as naively expected
264 // on many platforms -- yield() does not guarantee that any other ready threads
265 // will run. As such we revert to naked_short_sleep() after some number of iterations.
266 // nakes_short_sleep() is implemented as a short unconditional sleep.
267 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
268 // can actually increase the time it takes the VM thread to detect that a system-wide
269 // stop-the-world safepoint has been reached. In a pathological scenario such as that
270 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
271 // In that case the mutators will be stalled waiting for the safepoint to complete and the
272 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread
273 // will eventually wake up and detect that all mutators are safe, at which point
274 // we'll again make progress.
275 //
276 // Beware too that that the VMThread typically runs at elevated priority.
277 // Its default priority is higher than the default mutator priority.
278 // Obviously, this complicates spinning.
279 //
280 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
281 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
282 //
283 // See the comments in synchronizer.cpp for additional remarks on spinning.
284 //
285 // In the future we might:
286 // 1. Modify the safepoint scheme to avoid potentially unbounded spinning.
287 // This is tricky as the path used by a thread exiting the JVM (say on
288 // on JNI call-out) simply stores into its state field. The burden
289 // is placed on the VM thread, which must poll (spin).
290 // 2. Find something useful to do while spinning. If the safepoint is GC-related
291 // we might aggressively scan the stacks of threads that are already safe.
292 // 3. Use Solaris schedctl to examine the state of the still-running mutators.
293 // If all the mutators are ONPROC there's no reason to sleep or yield.
294 // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
295 // 5. Check system saturation. If the system is not fully saturated then
296 // simply spin and avoid sleep/yield.
297 // 6. As still-running mutators rendezvous they could unpark the sleeping
298 // VMthread. This works well for still-running mutators that become
299 // safe. The VMthread must still poll for mutators that call-out.
300 // 7. Drive the policy on time-since-begin instead of iterations.
301 // 8. Consider making the spin duration a function of the # of CPUs:
302 // Spin = (((ncpus-1) * M) + K) + F(still_running)
303 // Alternately, instead of counting iterations of the outer loop
304 // we could count the # of threads visited in the inner loop, above.
305 // 9. On windows consider using the return value from SwitchThreadTo()
306 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
307
308 if (int(iterations) == DeferPollingPageLoopCount) {
309 guarantee (PageArmed == 0, "invariant") ;
310 PageArmed = 1 ;
311 os::make_polling_page_unreadable();
312 }
313
314 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
315 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
316 ++steps ;
317 if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
318 SpinPause() ; // MP-Polite spin
319 } else
320 if (steps < DeferThrSuspendLoopCount) {
321 os::naked_yield() ;
322 } else {
323 os::naked_short_sleep(1);
324 }
325
326 iterations ++ ;
327 }
328 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
329 }
330 assert(still_running == 0, "sanity check");
331
332 if (PrintSafepointStatistics) {
333 update_statistics_on_spin_end();
334 }
335
336 if (sync_event.should_commit()) {
337 sync_event.set_safepointId(safepoint_counter());
338 sync_event.set_initialThreadCount(initial_running);
339 sync_event.set_runningThreadCount(_waiting_to_block);
340 sync_event.set_iterations(iterations);
341 sync_event.commit();
342 }
343 } //EventSafepointStateSync
344
345 // wait until all threads are stopped
346 {
347 EventSafepointWaitBlocked wait_blocked_event;
348 int initial_waiting_to_block = _waiting_to_block;
349
350 while (_waiting_to_block > 0) {
351 log_debug(safepoint)("Waiting for %d thread(s) to block", _waiting_to_block);
352 if (!SafepointTimeout || timeout_error_printed) {
353 Safepoint_lock->wait(true); // true, means with no safepoint checks
354 } else {
355 // Compute remaining time
356 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
357
358 // If there is no remaining time, then there is an error
359 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
360 print_safepoint_timeout(_blocking_timeout);
361 }
362 }
363 }
364 assert(_waiting_to_block == 0, "sanity check");
365
366 #ifndef PRODUCT
367 if (SafepointTimeout) {
368 jlong current_time = os::javaTimeNanos();
369 if (safepoint_limit_time < current_time) {
370 tty->print_cr("# SafepointSynchronize: Finished after "
371 INT64_FORMAT_W(6) " ms",
372 (int64_t)((current_time - safepoint_limit_time) / MICROUNITS +
373 (jlong)SafepointTimeoutDelay));
374 }
375 }
376 #endif
377
378 assert((_safepoint_counter & 0x1) == 0, "must be even");
379 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
380 _safepoint_counter ++;
381
382 // Record state
383 _state = _synchronized;
384
385 OrderAccess::fence();
386
387 if (wait_blocked_event.should_commit()) {
388 wait_blocked_event.set_safepointId(safepoint_counter());
389 wait_blocked_event.set_runningThreadCount(initial_waiting_to_block);
390 wait_blocked_event.commit();
391 }
392 } // EventSafepointWaitBlocked
393
394 #ifdef ASSERT
395 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
396 // make sure all the threads were visited
397 assert(cur->was_visited_for_critical_count(), "missed a thread");
398 }
399 #endif // ASSERT
400
401 // Update the count of active JNI critical regions
402 GCLocker::set_jni_lock_count(_current_jni_active_count);
403
404 if (log_is_enabled(Debug, safepoint)) {
405 log_debug(safepoint)("Entering safepoint region: %s", VMThread::vm_safepoint_description());
406 }
407
408 RuntimeService::record_safepoint_synchronized();
409 if (PrintSafepointStatistics) {
410 update_statistics_on_sync_end(os::javaTimeNanos());
411 }
412
413 // Call stuff that needs to be run when a safepoint is just about to be completed
414 {
415 EventSafepointCleanup cleanup_event;
416 do_cleanup_tasks();
417 if (cleanup_event.should_commit()) {
418 cleanup_event.set_safepointId(safepoint_counter());
419 cleanup_event.commit();
420 }
421 }
422
423 if (PrintSafepointStatistics) {
424 // Record how much time spend on the above cleanup tasks
425 update_statistics_on_cleanup_end(os::javaTimeNanos());
426 }
427 if (begin_event.should_commit()) {
428 begin_event.set_safepointId(safepoint_counter());
429 begin_event.set_totalThreadCount(nof_threads);
430 begin_event.set_jniCriticalThreadCount(_current_jni_active_count);
431 begin_event.commit();
432 }
433 }
434
435 // Wake up all threads, so they are ready to resume execution after the safepoint
436 // operation has been carried out
437 void SafepointSynchronize::end() {
438 EventSafepointEnd event;
439 int safepoint_id = safepoint_counter(); // Keep the odd counter as "id"
440
441 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
442 assert((_safepoint_counter & 0x1) == 1, "must be odd");
443 _safepoint_counter ++;
444 // memory fence isn't required here since an odd _safepoint_counter
445 // value can do no harm and a fence is issued below anyway.
446
447 DEBUG_ONLY(Thread* myThread = Thread::current();)
448 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
449
450 if (PrintSafepointStatistics) {
451 end_statistics(os::javaTimeNanos());
452 }
453
454 #ifdef ASSERT
455 // A pending_exception cannot be installed during a safepoint. The threads
456 // may install an async exception after they come back from a safepoint into
457 // pending_exception after they unblock. But that should happen later.
458 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
459 assert (!(cur->has_pending_exception() &&
460 cur->safepoint_state()->is_at_poll_safepoint()),
461 "safepoint installed a pending exception");
462 }
463 #endif // ASSERT
464
465 if (PageArmed) {
466 // Make polling safepoint aware
467 os::make_polling_page_readable();
468 PageArmed = 0 ;
469 }
470
471 // Remove safepoint check from interpreter
472 Interpreter::ignore_safepoints();
473
474 {
475 MutexLocker mu(Safepoint_lock);
476
477 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
478
479 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
480 // when they get restarted.
481 _state = _not_synchronized;
482 OrderAccess::fence();
483
484 log_debug(safepoint)("Leaving safepoint region");
485
486 // Start suspended threads
487 for(JavaThread *current = Threads::first(); current; current = current->next()) {
488 // A problem occurring on Solaris is when attempting to restart threads
489 // the first #cpus - 1 go well, but then the VMThread is preempted when we get
490 // to the next one (since it has been running the longest). We then have
491 // to wait for a cpu to become available before we can continue restarting
492 // threads.
493 // FIXME: This causes the performance of the VM to degrade when active and with
494 // large numbers of threads. Apparently this is due to the synchronous nature
495 // of suspending threads.
496 //
497 // TODO-FIXME: the comments above are vestigial and no longer apply.
498 // Furthermore, using solaris' schedctl in this particular context confers no benefit
499 if (VMThreadHintNoPreempt) {
500 os::hint_no_preempt();
501 }
502 ThreadSafepointState* cur_state = current->safepoint_state();
503 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
504 cur_state->restart();
505 assert(cur_state->is_running(), "safepoint state has not been reset");
506 }
507
508 RuntimeService::record_safepoint_end();
509
510 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads
511 // blocked in signal_thread_blocked
512 Threads_lock->unlock();
513
514 }
515 #if INCLUDE_ALL_GCS
516 // If there are any concurrent GC threads resume them.
517 if (UseConcMarkSweepGC) {
518 ConcurrentMarkSweepThread::desynchronize(false);
519 } else if (UseG1GC || (UseShenandoahGC && ShenandoahSuspendibleWorkers)) {
520 SuspendibleThreadSet::desynchronize();
521 }
522 #endif // INCLUDE_ALL_GCS
523 // record this time so VMThread can keep track how much time has elapsed
524 // since last safepoint.
525 _end_of_last_safepoint = os::javaTimeMillis();
526
527 if (event.should_commit()) {
528 event.set_safepointId(safepoint_id);
529 event.commit();
530 }
531 }
532
533 bool SafepointSynchronize::is_cleanup_needed() {
534 // Need a safepoint if there are many monitors to deflate.
535 if (ObjectSynchronizer::is_cleanup_needed()) return true;
536 // Need a safepoint if some inline cache buffers is non-empty
537 if (!InlineCacheBuffer::is_empty()) return true;
538 return false;
539 }
540
541 static void event_safepoint_cleanup_task_commit(EventSafepointCleanupTask& event, const char* name) {
542 if (event.should_commit()) {
543 event.set_safepointId(SafepointSynchronize::safepoint_counter());
544 event.set_name(name);
545 event.commit();
546 }
547 }
548
549 class ParallelSPCleanupThreadClosure : public ThreadClosure {
550 private:
551 bool _do_deflate_idle_monitors;
552 CodeBlobClosure* _nmethod_cl;
553 DeflateMonitorCounters* _counters;
554
555 public:
556 ParallelSPCleanupThreadClosure(DeflateMonitorCounters* counters) :
557 _counters(counters) {
558 VM_Operation* op = VMThread::vm_operation();
559 _do_deflate_idle_monitors = op == NULL || ! op->deflates_idle_monitors();
560 if (op == NULL || ! op->marks_nmethods()) {
561 _nmethod_cl = NMethodSweeper::prepare_mark_active_nmethods();
562 } else {
563 _nmethod_cl = NULL;
564 }
565 }
566
567 void do_thread(Thread* thread) {
568 if (_do_deflate_idle_monitors) {
569 ObjectSynchronizer::deflate_thread_local_monitors(thread, _counters, NULL);
570 }
571 if (_nmethod_cl != NULL && thread->is_Java_thread() &&
572 ! thread->is_Code_cache_sweeper_thread()) {
573 JavaThread* jt = (JavaThread*) thread;
574 jt->nmethods_do(_nmethod_cl);
575 }
576 }
577 };
578
579 class ParallelSPCleanupTask : public AbstractGangTask {
580 private:
581 SubTasksDone _subtasks;
582 ParallelSPCleanupThreadClosure _cleanup_threads_cl;
583 uint _num_workers;
584 DeflateMonitorCounters* _counters;
585 public:
586 ParallelSPCleanupTask(uint num_workers, DeflateMonitorCounters* counters) :
587 AbstractGangTask("Parallel Safepoint Cleanup"),
588 _cleanup_threads_cl(ParallelSPCleanupThreadClosure(counters)),
589 _num_workers(num_workers),
590 _subtasks(SubTasksDone(SafepointSynchronize::SAFEPOINT_CLEANUP_NUM_TASKS)),
591 _counters(counters) {}
592
593 void work(uint worker_id) {
594 // All threads deflate monitors and mark nmethods (if necessary).
595 Threads::parallel_java_threads_do(&_cleanup_threads_cl);
596
597 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_DEFLATE_MONITORS)) {
598 const char* name = "deflating idle monitors";
599 EventSafepointCleanupTask event;
600 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
601 ObjectSynchronizer::deflate_idle_monitors(_counters);
602 event_safepoint_cleanup_task_commit(event, name);
603 }
604
605 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_UPDATE_INLINE_CACHES)) {
606 const char* name = "updating inline caches";
607 EventSafepointCleanupTask event;
608 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
609 InlineCacheBuffer::update_inline_caches();
610 event_safepoint_cleanup_task_commit(event, name);
611 }
612
613 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_COMPILATION_POLICY)) {
614 const char* name = "compilation policy safepoint handler";
615 EventSafepointCleanupTask event;
616 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
617 CompilationPolicy::policy()->do_safepoint_work();
618 event_safepoint_cleanup_task_commit(event, name);
619 }
620
621 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_SYMBOL_TABLE_REHASH)) {
622 if (SymbolTable::needs_rehashing()) {
623 const char* name = "rehashing symbol table";
624 EventSafepointCleanupTask event;
625 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
626 SymbolTable::rehash_table();
627 event_safepoint_cleanup_task_commit(event, name);
628 }
629 }
630
631 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_STRING_TABLE_REHASH)) {
632 if (StringTable::needs_rehashing()) {
633 const char* name = "rehashing string table";
634 EventSafepointCleanupTask event;
635 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
636 StringTable::rehash_table();
637 event_safepoint_cleanup_task_commit(event, name);
638 }
639 }
640
641 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_CLD_PURGE)) {
642 // CMS delays purging the CLDG until the beginning of the next safepoint and to
643 // make sure concurrent sweep is done
644 const char* name = "purging class loader data graph";
645 EventSafepointCleanupTask event;
646 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
647 ClassLoaderDataGraph::purge_if_needed();
648 event_safepoint_cleanup_task_commit(event, name);
649 }
650 _subtasks.all_tasks_completed(_num_workers);
651 }
652 };
653
654 // Various cleaning tasks that should be done periodically at safepoints.
655 void SafepointSynchronize::do_cleanup_tasks() {
656
657 TraceTime timer("safepoint cleanup tasks", TRACETIME_LOG(Info, safepoint, cleanup));
658
659 // Prepare for monitor deflation.
660 DeflateMonitorCounters deflate_counters;
661 ObjectSynchronizer::prepare_deflate_idle_monitors(&deflate_counters);
662
663 CollectedHeap* heap = Universe::heap();
664 assert(heap != NULL, "heap not initialized yet?");
665 WorkGang* cleanup_workers = heap->get_safepoint_workers();
666 if (cleanup_workers != NULL) {
667 // Parallel cleanup using GC provided thread pool.
668 uint num_cleanup_workers = cleanup_workers->active_workers();
669 ParallelSPCleanupTask cleanup(num_cleanup_workers, &deflate_counters);
670 StrongRootsScope srs(num_cleanup_workers);
671 cleanup_workers->run_task(&cleanup);
672 } else {
673 // Serial cleanup using VMThread.
674 ParallelSPCleanupTask cleanup(1, &deflate_counters);
675 StrongRootsScope srs(1);
676 cleanup.work(0);
677 }
678
679 // Finish monitor deflation.
680 ObjectSynchronizer::finish_deflate_idle_monitors(&deflate_counters);
681 }
682
683
684 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
685 switch(state) {
686 case _thread_in_native:
687 // native threads are safe if they have no java stack or have walkable stack
688 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
689
690 // blocked threads should have already have walkable stack
691 case _thread_blocked:
692 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
693 return true;
694
695 default:
696 return false;
697 }
698 }
699
700
701 // See if the thread is running inside a lazy critical native and
702 // update the thread critical count if so. Also set a suspend flag to
703 // cause the native wrapper to return into the JVM to do the unlock
704 // once the native finishes.
705 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
706 if (state == _thread_in_native &&
707 thread->has_last_Java_frame() &&
708 thread->frame_anchor()->walkable()) {
709 // This thread might be in a critical native nmethod so look at
710 // the top of the stack and increment the critical count if it
711 // is.
712 frame wrapper_frame = thread->last_frame();
713 CodeBlob* stub_cb = wrapper_frame.cb();
714 if (stub_cb != NULL &&
715 stub_cb->is_nmethod() &&
716 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
717 // A thread could potentially be in a critical native across
718 // more than one safepoint, so only update the critical state on
719 // the first one. When it returns it will perform the unlock.
720 if (!thread->do_critical_native_unlock()) {
721 #ifdef ASSERT
722 if (!thread->in_critical()) {
723 GCLocker::increment_debug_jni_lock_count();
724 }
725 #endif
726 thread->enter_critical();
727 // Make sure the native wrapper calls back on return to
728 // perform the needed critical unlock.
729 thread->set_critical_native_unlock();
730 }
731 }
732 }
733 }
734
735
736
737 // -------------------------------------------------------------------------------------------------------
738 // Implementation of Safepoint callback point
739
740 void SafepointSynchronize::block(JavaThread *thread) {
741 assert(thread != NULL, "thread must be set");
742 assert(thread->is_Java_thread(), "not a Java thread");
743
744 // Threads shouldn't block if they are in the middle of printing, but...
745 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
746
747 // Only bail from the block() call if the thread is gone from the
748 // thread list; starting to exit should still block.
749 if (thread->is_terminated()) {
750 // block current thread if we come here from native code when VM is gone
751 thread->block_if_vm_exited();
752
753 // otherwise do nothing
754 return;
755 }
756
757 JavaThreadState state = thread->thread_state();
758 thread->frame_anchor()->make_walkable(thread);
759
760 // Check that we have a valid thread_state at this point
761 switch(state) {
762 case _thread_in_vm_trans:
763 case _thread_in_Java: // From compiled code
764
765 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
766 // we pretend we are still in the VM.
767 thread->set_thread_state(_thread_in_vm);
768
769 if (is_synchronizing()) {
770 Atomic::inc (&TryingToBlock) ;
771 }
772
773 // We will always be holding the Safepoint_lock when we are examine the state
774 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
775 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
776 Safepoint_lock->lock_without_safepoint_check();
777 if (is_synchronizing()) {
778 // Decrement the number of threads to wait for and signal vm thread
779 assert(_waiting_to_block > 0, "sanity check");
780 _waiting_to_block--;
781 thread->safepoint_state()->set_has_called_back(true);
782
783 DEBUG_ONLY(thread->set_visited_for_critical_count(true));
784 if (thread->in_critical()) {
785 // Notice that this thread is in a critical section
786 increment_jni_active_count();
787 }
788
789 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
790 if (_waiting_to_block == 0) {
791 Safepoint_lock->notify_all();
792 }
793 }
794
795 // We transition the thread to state _thread_blocked here, but
796 // we can't do our usual check for external suspension and then
797 // self-suspend after the lock_without_safepoint_check() call
798 // below because we are often called during transitions while
799 // we hold different locks. That would leave us suspended while
800 // holding a resource which results in deadlocks.
801 thread->set_thread_state(_thread_blocked);
802 Safepoint_lock->unlock();
803
804 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
805 // the entire safepoint, the threads will all line up here during the safepoint.
806 Threads_lock->lock_without_safepoint_check();
807 // restore original state. This is important if the thread comes from compiled code, so it
808 // will continue to execute with the _thread_in_Java state.
809 thread->set_thread_state(state);
810 Threads_lock->unlock();
811 break;
812
813 case _thread_in_native_trans:
814 case _thread_blocked_trans:
815 case _thread_new_trans:
816 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
817 thread->print_thread_state();
818 fatal("Deadlock in safepoint code. "
819 "Should have called back to the VM before blocking.");
820 }
821
822 // We transition the thread to state _thread_blocked here, but
823 // we can't do our usual check for external suspension and then
824 // self-suspend after the lock_without_safepoint_check() call
825 // below because we are often called during transitions while
826 // we hold different locks. That would leave us suspended while
827 // holding a resource which results in deadlocks.
828 thread->set_thread_state(_thread_blocked);
829
830 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
831 // the safepoint code might still be waiting for it to block. We need to change the state here,
832 // so it can see that it is at a safepoint.
833
834 // Block until the safepoint operation is completed.
835 Threads_lock->lock_without_safepoint_check();
836
837 // Restore state
838 thread->set_thread_state(state);
839
840 Threads_lock->unlock();
841 break;
842
843 default:
844 fatal("Illegal threadstate encountered: %d", state);
845 }
846
847 // Check for pending. async. exceptions or suspends - except if the
848 // thread was blocked inside the VM. has_special_runtime_exit_condition()
849 // is called last since it grabs a lock and we only want to do that when
850 // we must.
851 //
852 // Note: we never deliver an async exception at a polling point as the
853 // compiler may not have an exception handler for it. The polling
854 // code will notice the async and deoptimize and the exception will
855 // be delivered. (Polling at a return point is ok though). Sure is
856 // a lot of bother for a deprecated feature...
857 //
858 // We don't deliver an async exception if the thread state is
859 // _thread_in_native_trans so JNI functions won't be called with
860 // a surprising pending exception. If the thread state is going back to java,
861 // async exception is checked in check_special_condition_for_native_trans().
862
863 if (state != _thread_blocked_trans &&
864 state != _thread_in_vm_trans &&
865 thread->has_special_runtime_exit_condition()) {
866 thread->handle_special_runtime_exit_condition(
867 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
868 }
869 }
870
871 // ------------------------------------------------------------------------------------------------------
872 // Exception handlers
873
874
875 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
876 assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
877 assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
878 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
879
880 if (ShowSafepointMsgs) {
881 tty->print("handle_polling_page_exception: ");
882 }
883
884 if (PrintSafepointStatistics) {
885 inc_page_trap_count();
886 }
887
888 ThreadSafepointState* state = thread->safepoint_state();
889
890 state->handle_polling_page_exception();
891 }
892
893
894 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
895 if (!timeout_error_printed) {
896 timeout_error_printed = true;
897 // Print out the thread info which didn't reach the safepoint for debugging
898 // purposes (useful when there are lots of threads in the debugger).
899 tty->cr();
900 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
901 if (reason == _spinning_timeout) {
902 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
903 } else if (reason == _blocking_timeout) {
904 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
905 }
906
907 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
908 ThreadSafepointState *cur_state;
909 ResourceMark rm;
910 for(JavaThread *cur_thread = Threads::first(); cur_thread;
911 cur_thread = cur_thread->next()) {
912 cur_state = cur_thread->safepoint_state();
913
914 if (cur_thread->thread_state() != _thread_blocked &&
915 ((reason == _spinning_timeout && cur_state->is_running()) ||
916 (reason == _blocking_timeout && !cur_state->has_called_back()))) {
917 tty->print("# ");
918 cur_thread->print();
919 tty->cr();
920 }
921 }
922 tty->print_cr("# SafepointSynchronize::begin: (End of list)");
923 }
924
925 // To debug the long safepoint, specify both DieOnSafepointTimeout &
926 // ShowMessageBoxOnError.
927 if (DieOnSafepointTimeout) {
928 fatal("Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
929 SafepointTimeoutDelay, VMThread::vm_safepoint_description());
930 }
931 }
932
933
934 // -------------------------------------------------------------------------------------------------------
935 // Implementation of ThreadSafepointState
936
937 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
938 _thread = thread;
939 _type = _running;
940 _has_called_back = false;
941 _at_poll_safepoint = false;
942 }
943
944 void ThreadSafepointState::create(JavaThread *thread) {
945 ThreadSafepointState *state = new ThreadSafepointState(thread);
946 thread->set_safepoint_state(state);
947 }
948
949 void ThreadSafepointState::destroy(JavaThread *thread) {
950 if (thread->safepoint_state()) {
951 delete(thread->safepoint_state());
952 thread->set_safepoint_state(NULL);
953 }
954 }
955
956 void ThreadSafepointState::examine_state_of_thread() {
957 assert(is_running(), "better be running or just have hit safepoint poll");
958
959 JavaThreadState state = _thread->thread_state();
960
961 // Save the state at the start of safepoint processing.
962 _orig_thread_state = state;
963
964 // Check for a thread that is suspended. Note that thread resume tries
965 // to grab the Threads_lock which we own here, so a thread cannot be
966 // resumed during safepoint synchronization.
967
968 // We check to see if this thread is suspended without locking to
969 // avoid deadlocking with a third thread that is waiting for this
970 // thread to be suspended. The third thread can notice the safepoint
971 // that we're trying to start at the beginning of its SR_lock->wait()
972 // call. If that happens, then the third thread will block on the
973 // safepoint while still holding the underlying SR_lock. We won't be
974 // able to get the SR_lock and we'll deadlock.
975 //
976 // We don't need to grab the SR_lock here for two reasons:
977 // 1) The suspend flags are both volatile and are set with an
978 // Atomic::cmpxchg() call so we should see the suspended
979 // state right away.
980 // 2) We're being called from the safepoint polling loop; if
981 // we don't see the suspended state on this iteration, then
982 // we'll come around again.
983 //
984 bool is_suspended = _thread->is_ext_suspended();
985 if (is_suspended) {
986 roll_forward(_at_safepoint);
987 return;
988 }
989
990 // Some JavaThread states have an initial safepoint state of
991 // running, but are actually at a safepoint. We will happily
992 // agree and update the safepoint state here.
993 if (SafepointSynchronize::safepoint_safe(_thread, state)) {
994 SafepointSynchronize::check_for_lazy_critical_native(_thread, state);
995 roll_forward(_at_safepoint);
996 return;
997 }
998
999 if (state == _thread_in_vm) {
1000 roll_forward(_call_back);
1001 return;
1002 }
1003
1004 // All other thread states will continue to run until they
1005 // transition and self-block in state _blocked
1006 // Safepoint polling in compiled code causes the Java threads to do the same.
1007 // Note: new threads may require a malloc so they must be allowed to finish
1008
1009 assert(is_running(), "examine_state_of_thread on non-running thread");
1010 return;
1011 }
1012
1013 // Returns true is thread could not be rolled forward at present position.
1014 void ThreadSafepointState::roll_forward(suspend_type type) {
1015 _type = type;
1016
1017 switch(_type) {
1018 case _at_safepoint:
1019 SafepointSynchronize::signal_thread_at_safepoint();
1020 DEBUG_ONLY(_thread->set_visited_for_critical_count(true));
1021 if (_thread->in_critical()) {
1022 // Notice that this thread is in a critical section
1023 SafepointSynchronize::increment_jni_active_count();
1024 }
1025 break;
1026
1027 case _call_back:
1028 set_has_called_back(false);
1029 break;
1030
1031 case _running:
1032 default:
1033 ShouldNotReachHere();
1034 }
1035 }
1036
1037 void ThreadSafepointState::restart() {
1038 switch(type()) {
1039 case _at_safepoint:
1040 case _call_back:
1041 break;
1042
1043 case _running:
1044 default:
1045 tty->print_cr("restart thread " INTPTR_FORMAT " with state %d",
1046 p2i(_thread), _type);
1047 _thread->print();
1048 ShouldNotReachHere();
1049 }
1050 _type = _running;
1051 set_has_called_back(false);
1052 }
1053
1054
1055 void ThreadSafepointState::print_on(outputStream *st) const {
1056 const char *s = NULL;
1057
1058 switch(_type) {
1059 case _running : s = "_running"; break;
1060 case _at_safepoint : s = "_at_safepoint"; break;
1061 case _call_back : s = "_call_back"; break;
1062 default:
1063 ShouldNotReachHere();
1064 }
1065
1066 st->print_cr("Thread: " INTPTR_FORMAT
1067 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
1068 p2i(_thread), _thread->osthread()->thread_id(), s, _has_called_back,
1069 _at_poll_safepoint);
1070
1071 _thread->print_thread_state_on(st);
1072 }
1073
1074 // ---------------------------------------------------------------------------------------------------------------------
1075
1076 // Block the thread at the safepoint poll or poll return.
1077 void ThreadSafepointState::handle_polling_page_exception() {
1078
1079 // Check state. block() will set thread state to thread_in_vm which will
1080 // cause the safepoint state _type to become _call_back.
1081 assert(type() == ThreadSafepointState::_running,
1082 "polling page exception on thread not running state");
1083
1084 // Step 1: Find the nmethod from the return address
1085 if (ShowSafepointMsgs && Verbose) {
1086 tty->print_cr("Polling page exception at " INTPTR_FORMAT, p2i(thread()->saved_exception_pc()));
1087 }
1088 address real_return_addr = thread()->saved_exception_pc();
1089
1090 CodeBlob *cb = CodeCache::find_blob(real_return_addr);
1091 assert(cb != NULL && cb->is_compiled(), "return address should be in nmethod");
1092 CompiledMethod* nm = (CompiledMethod*)cb;
1093
1094 // Find frame of caller
1095 frame stub_fr = thread()->last_frame();
1096 CodeBlob* stub_cb = stub_fr.cb();
1097 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
1098 RegisterMap map(thread(), true);
1099 frame caller_fr = stub_fr.sender(&map);
1100
1101 // Should only be poll_return or poll
1102 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
1103
1104 // This is a poll immediately before a return. The exception handling code
1105 // has already had the effect of causing the return to occur, so the execution
1106 // will continue immediately after the call. In addition, the oopmap at the
1107 // return point does not mark the return value as an oop (if it is), so
1108 // it needs a handle here to be updated.
1109 if( nm->is_at_poll_return(real_return_addr) ) {
1110 // See if return type is an oop.
1111 bool return_oop = nm->method()->is_returning_oop();
1112 Handle return_value;
1113 if (return_oop) {
1114 // The oop result has been saved on the stack together with all
1115 // the other registers. In order to preserve it over GCs we need
1116 // to keep it in a handle.
1117 oop result = caller_fr.saved_oop_result(&map);
1118 assert(result == NULL || result->is_oop(), "must be oop");
1119 return_value = Handle(thread(), result);
1120 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
1121 }
1122
1123 // Block the thread
1124 SafepointSynchronize::block(thread());
1125
1126 // restore oop result, if any
1127 if (return_oop) {
1128 caller_fr.set_saved_oop_result(&map, return_value());
1129 }
1130 }
1131
1132 // This is a safepoint poll. Verify the return address and block.
1133 else {
1134 set_at_poll_safepoint(true);
1135
1136 // verify the blob built the "return address" correctly
1137 assert(real_return_addr == caller_fr.pc(), "must match");
1138
1139 // Block the thread
1140 SafepointSynchronize::block(thread());
1141 set_at_poll_safepoint(false);
1142
1143 // If we have a pending async exception deoptimize the frame
1144 // as otherwise we may never deliver it.
1145 if (thread()->has_async_condition()) {
1146 ThreadInVMfromJavaNoAsyncException __tiv(thread());
1147 Deoptimization::deoptimize_frame(thread(), caller_fr.id());
1148 }
1149
1150 // If an exception has been installed we must check for a pending deoptimization
1151 // Deoptimize frame if exception has been thrown.
1152
1153 if (thread()->has_pending_exception() ) {
1154 RegisterMap map(thread(), true);
1155 frame caller_fr = stub_fr.sender(&map);
1156 if (caller_fr.is_deoptimized_frame()) {
1157 // The exception patch will destroy registers that are still
1158 // live and will be needed during deoptimization. Defer the
1159 // Async exception should have deferred the exception until the
1160 // next safepoint which will be detected when we get into
1161 // the interpreter so if we have an exception now things
1162 // are messed up.
1163
1164 fatal("Exception installed and deoptimization is pending");
1165 }
1166 }
1167 }
1168 }
1169
1170
1171 //
1172 // Statistics & Instrumentations
1173 //
1174 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL;
1175 jlong SafepointSynchronize::_safepoint_begin_time = 0;
1176 int SafepointSynchronize::_cur_stat_index = 0;
1177 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
1178 julong SafepointSynchronize::_coalesced_vmop_count = 0;
1179 jlong SafepointSynchronize::_max_sync_time = 0;
1180 jlong SafepointSynchronize::_max_vmop_time = 0;
1181 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f;
1182
1183 static jlong cleanup_end_time = 0;
1184 static bool need_to_track_page_armed_status = false;
1185 static bool init_done = false;
1186
1187 // Helper method to print the header.
1188 static void print_header() {
1189 // The number of spaces is significant here, and should match the format
1190 // specifiers in print_statistics().
1191
1192 tty->print(" vmop "
1193 "[ threads: total initially_running wait_to_block ]"
1194 "[ time: spin block sync cleanup vmop ] ");
1195
1196 // no page armed status printed out if it is always armed.
1197 if (need_to_track_page_armed_status) {
1198 tty->print("page_armed ");
1199 }
1200
1201 tty->print_cr("page_trap_count");
1202 }
1203
1204 void SafepointSynchronize::deferred_initialize_stat() {
1205 if (init_done) return;
1206
1207 // If PrintSafepointStatisticsTimeout is specified, the statistics data will
1208 // be printed right away, in which case, _safepoint_stats will regress to
1209 // a single element array. Otherwise, it is a circular ring buffer with default
1210 // size of PrintSafepointStatisticsCount.
1211 int stats_array_size;
1212 if (PrintSafepointStatisticsTimeout > 0) {
1213 stats_array_size = 1;
1214 PrintSafepointStatistics = true;
1215 } else {
1216 stats_array_size = PrintSafepointStatisticsCount;
1217 }
1218 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
1219 * sizeof(SafepointStats), mtInternal);
1220 guarantee(_safepoint_stats != NULL,
1221 "not enough memory for safepoint instrumentation data");
1222
1223 if (DeferPollingPageLoopCount >= 0) {
1224 need_to_track_page_armed_status = true;
1225 }
1226 init_done = true;
1227 }
1228
1229 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
1230 assert(init_done, "safepoint statistics array hasn't been initialized");
1231 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1232
1233 spstat->_time_stamp = _ts_of_current_safepoint;
1234
1235 VM_Operation *op = VMThread::vm_operation();
1236 spstat->_vmop_type = (op != NULL ? op->type() : -1);
1237 if (op != NULL) {
1238 _safepoint_reasons[spstat->_vmop_type]++;
1239 }
1240
1241 spstat->_nof_total_threads = nof_threads;
1242 spstat->_nof_initial_running_threads = nof_running;
1243 spstat->_nof_threads_hit_page_trap = 0;
1244
1245 // Records the start time of spinning. The real time spent on spinning
1246 // will be adjusted when spin is done. Same trick is applied for time
1247 // spent on waiting for threads to block.
1248 if (nof_running != 0) {
1249 spstat->_time_to_spin = os::javaTimeNanos();
1250 } else {
1251 spstat->_time_to_spin = 0;
1252 }
1253 }
1254
1255 void SafepointSynchronize::update_statistics_on_spin_end() {
1256 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1257
1258 jlong cur_time = os::javaTimeNanos();
1259
1260 spstat->_nof_threads_wait_to_block = _waiting_to_block;
1261 if (spstat->_nof_initial_running_threads != 0) {
1262 spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
1263 }
1264
1265 if (need_to_track_page_armed_status) {
1266 spstat->_page_armed = (PageArmed == 1);
1267 }
1268
1269 // Records the start time of waiting for to block. Updated when block is done.
1270 if (_waiting_to_block != 0) {
1271 spstat->_time_to_wait_to_block = cur_time;
1272 } else {
1273 spstat->_time_to_wait_to_block = 0;
1274 }
1275 }
1276
1277 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
1278 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1279
1280 if (spstat->_nof_threads_wait_to_block != 0) {
1281 spstat->_time_to_wait_to_block = end_time -
1282 spstat->_time_to_wait_to_block;
1283 }
1284
1285 // Records the end time of sync which will be used to calculate the total
1286 // vm operation time. Again, the real time spending in syncing will be deducted
1287 // from the start of the sync time later when end_statistics is called.
1288 spstat->_time_to_sync = end_time - _safepoint_begin_time;
1289 if (spstat->_time_to_sync > _max_sync_time) {
1290 _max_sync_time = spstat->_time_to_sync;
1291 }
1292
1293 spstat->_time_to_do_cleanups = end_time;
1294 }
1295
1296 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
1297 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1298
1299 // Record how long spent in cleanup tasks.
1300 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
1301
1302 cleanup_end_time = end_time;
1303 }
1304
1305 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
1306 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1307
1308 // Update the vm operation time.
1309 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time;
1310 if (spstat->_time_to_exec_vmop > _max_vmop_time) {
1311 _max_vmop_time = spstat->_time_to_exec_vmop;
1312 }
1313 // Only the sync time longer than the specified
1314 // PrintSafepointStatisticsTimeout will be printed out right away.
1315 // By default, it is -1 meaning all samples will be put into the list.
1316 if ( PrintSafepointStatisticsTimeout > 0) {
1317 if (spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
1318 print_statistics();
1319 }
1320 } else {
1321 // The safepoint statistics will be printed out when the _safepoin_stats
1322 // array fills up.
1323 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) {
1324 print_statistics();
1325 _cur_stat_index = 0;
1326 } else {
1327 _cur_stat_index++;
1328 }
1329 }
1330 }
1331
1332 void SafepointSynchronize::print_statistics() {
1333 for (int index = 0; index <= _cur_stat_index; index++) {
1334 if (index % 30 == 0) {
1335 print_header();
1336 }
1337 SafepointStats* sstats = &_safepoint_stats[index];
1338 tty->print("%8.3f: ", sstats->_time_stamp);
1339 tty->print("%-30s [ "
1340 INT32_FORMAT_W(8) " " INT32_FORMAT_W(17) " " INT32_FORMAT_W(13) " "
1341 "]",
1342 (sstats->_vmop_type == -1 ? "no vm operation" : VM_Operation::name(sstats->_vmop_type)),
1343 sstats->_nof_total_threads,
1344 sstats->_nof_initial_running_threads,
1345 sstats->_nof_threads_wait_to_block);
1346 // "/ MICROUNITS " is to convert the unit from nanos to millis.
1347 tty->print("[ "
1348 INT64_FORMAT_W(7) " " INT64_FORMAT_W(7) " "
1349 INT64_FORMAT_W(7) " " INT64_FORMAT_W(7) " "
1350 INT64_FORMAT_W(7) " ] ",
1351 (int64_t)(sstats->_time_to_spin / MICROUNITS),
1352 (int64_t)(sstats->_time_to_wait_to_block / MICROUNITS),
1353 (int64_t)(sstats->_time_to_sync / MICROUNITS),
1354 (int64_t)(sstats->_time_to_do_cleanups / MICROUNITS),
1355 (int64_t)(sstats->_time_to_exec_vmop / MICROUNITS));
1356
1357 if (need_to_track_page_armed_status) {
1358 tty->print(INT32_FORMAT_W(10) " ", sstats->_page_armed);
1359 }
1360 tty->print_cr(INT32_FORMAT_W(15) " ", sstats->_nof_threads_hit_page_trap);
1361 }
1362 }
1363
1364 // This method will be called when VM exits. It will first call
1365 // print_statistics to print out the rest of the sampling. Then
1366 // it tries to summarize the sampling.
1367 void SafepointSynchronize::print_stat_on_exit() {
1368 if (_safepoint_stats == NULL) return;
1369
1370 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1371
1372 // During VM exit, end_statistics may not get called and in that
1373 // case, if the sync time is less than PrintSafepointStatisticsTimeout,
1374 // don't print it out.
1375 // Approximate the vm op time.
1376 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
1377 os::javaTimeNanos() - cleanup_end_time;
1378
1379 if ( PrintSafepointStatisticsTimeout < 0 ||
1380 spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
1381 print_statistics();
1382 }
1383 tty->cr();
1384
1385 // Print out polling page sampling status.
1386 if (!need_to_track_page_armed_status) {
1387 tty->print_cr("Polling page always armed");
1388 } else {
1389 tty->print_cr("Defer polling page loop count = " INTX_FORMAT "\n",
1390 DeferPollingPageLoopCount);
1391 }
1392
1393 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1394 if (_safepoint_reasons[index] != 0) {
1395 tty->print_cr("%-26s" UINT64_FORMAT_W(10), VM_Operation::name(index),
1396 _safepoint_reasons[index]);
1397 }
1398 }
1399
1400 tty->print_cr(UINT64_FORMAT_W(5) " VM operations coalesced during safepoint",
1401 _coalesced_vmop_count);
1402 tty->print_cr("Maximum sync time " INT64_FORMAT_W(5) " ms",
1403 (int64_t)(_max_sync_time / MICROUNITS));
1404 tty->print_cr("Maximum vm operation time (except for Exit VM operation) "
1405 INT64_FORMAT_W(5) " ms",
1406 (int64_t)(_max_vmop_time / MICROUNITS));
1407 }
1408
1409 // ------------------------------------------------------------------------------------------------
1410 // Non-product code
1411
1412 #ifndef PRODUCT
1413
1414 void SafepointSynchronize::print_state() {
1415 if (_state == _not_synchronized) {
1416 tty->print_cr("not synchronized");
1417 } else if (_state == _synchronizing || _state == _synchronized) {
1418 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
1419 "synchronized");
1420
1421 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
1422 cur->safepoint_state()->print();
1423 }
1424 }
1425 }
1426
1427 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
1428 if (ShowSafepointMsgs) {
1429 va_list ap;
1430 va_start(ap, format);
1431 tty->vprint_cr(format, ap);
1432 va_end(ap);
1433 }
1434 }
1435
1436 #endif // !PRODUCT