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/classLoaderData.hpp"
27 #include "classfile/stringTable.hpp"
28 #include "classfile/symbolTable.hpp"
29 #include "classfile/systemDictionary.hpp"
30 #include "code/codeCache.hpp"
31 #include "code/icBuffer.hpp"
32 #include "code/nmethod.hpp"
33 #include "code/pcDesc.hpp"
34 #include "code/scopeDesc.hpp"
35 #include "gc/shared/collectedHeap.hpp"
36 #include "gc/shared/gcLocker.inline.hpp"
37 #include "gc/shared/strongRootsScope.hpp"
38 #include "gc/shared/workgroup.hpp"
39 #include "interpreter/interpreter.hpp"
40 #include "logging/log.hpp"
41 #include "logging/logStream.hpp"
42 #include "memory/resourceArea.hpp"
43 #include "memory/universe.inline.hpp"
44 #include "oops/oop.inline.hpp"
45 #include "oops/symbol.hpp"
46 #include "runtime/atomic.hpp"
47 #include "runtime/compilationPolicy.hpp"
48 #include "runtime/deoptimization.hpp"
49 #include "runtime/frame.inline.hpp"
50 #include "runtime/interfaceSupport.hpp"
51 #include "runtime/mutexLocker.hpp"
52 #include "runtime/orderAccess.inline.hpp"
53 #include "runtime/osThread.hpp"
54 #include "runtime/safepoint.hpp"
55 #include "runtime/safepointMechanism.inline.hpp"
56 #include "runtime/signature.hpp"
57 #include "runtime/stubCodeGenerator.hpp"
58 #include "runtime/stubRoutines.hpp"
59 #include "runtime/sweeper.hpp"
60 #include "runtime/synchronizer.hpp"
61 #include "runtime/thread.inline.hpp"
62 #include "runtime/threadSMR.hpp"
63 #include "runtime/timerTrace.hpp"
64 #include "services/runtimeService.hpp"
65 #include "trace/tracing.hpp"
66 #include "trace/traceMacros.hpp"
67 #include "utilities/events.hpp"
68 #include "utilities/macros.hpp"
69 #ifdef COMPILER1
70 #include "c1/c1_globals.hpp"
71 #endif
72
73 // --------------------------------------------------------------------------------------------------
74 // Implementation of Safepoint begin/end
75
76 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
77 volatile int SafepointSynchronize::_waiting_to_block = 0;
78 volatile int SafepointSynchronize::_safepoint_counter = 0;
79 int SafepointSynchronize::_current_jni_active_count = 0;
80 long SafepointSynchronize::_end_of_last_safepoint = 0;
81 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE
82 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only
83 static bool timeout_error_printed = false;
84
85 // Roll all threads forward to a safepoint and suspend them all
86 void SafepointSynchronize::begin() {
87 EventSafepointBegin begin_event;
88 Thread* myThread = Thread::current();
89 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint");
90
91 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
92 _safepoint_begin_time = os::javaTimeNanos();
93 _ts_of_current_safepoint = tty->time_stamp().seconds();
94 }
95
96 Universe::heap()->safepoint_synchronize_begin();
97
98 // By getting the Threads_lock, we assure that no threads are about to start or
99 // exit. It is released again in SafepointSynchronize::end().
100 Threads_lock->lock();
101
102 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
103
104 int nof_threads = Threads::number_of_threads();
105
106 log_debug(safepoint)("Safepoint synchronization initiated. (%d)", nof_threads);
107
108 RuntimeService::record_safepoint_begin();
109
110 MutexLocker mu(Safepoint_lock);
111
112 // Reset the count of active JNI critical threads
113 _current_jni_active_count = 0;
114
115 // Set number of threads to wait for, before we initiate the callbacks
116 _waiting_to_block = nof_threads;
117 TryingToBlock = 0 ;
118 int still_running = nof_threads;
119
120 // Save the starting time, so that it can be compared to see if this has taken
121 // too long to complete.
122 jlong safepoint_limit_time = 0;
123 timeout_error_printed = false;
124
125 // PrintSafepointStatisticsTimeout can be specified separately. When
126 // specified, PrintSafepointStatistics will be set to true in
127 // deferred_initialize_stat method. The initialization has to be done
128 // early enough to avoid any races. See bug 6880029 for details.
129 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
130 deferred_initialize_stat();
131 }
132
133 // Begin the process of bringing the system to a safepoint.
134 // Java threads can be in several different states and are
135 // stopped by different mechanisms:
136 //
137 // 1. Running interpreted
138 // The interpreter dispatch table is changed to force it to
139 // check for a safepoint condition between bytecodes.
140 // 2. Running in native code
141 // When returning from the native code, a Java thread must check
142 // the safepoint _state to see if we must block. If the
143 // VM thread sees a Java thread in native, it does
144 // not wait for this thread to block. The order of the memory
145 // writes and reads of both the safepoint state and the Java
146 // threads state is critical. In order to guarantee that the
147 // memory writes are serialized with respect to each other,
148 // the VM thread issues a memory barrier instruction
149 // (on MP systems). In order to avoid the overhead of issuing
150 // a memory barrier for each Java thread making native calls, each Java
151 // thread performs a write to a single memory page after changing
152 // the thread state. The VM thread performs a sequence of
153 // mprotect OS calls which forces all previous writes from all
154 // Java threads to be serialized. This is done in the
155 // os::serialize_thread_states() call. This has proven to be
156 // much more efficient than executing a membar instruction
157 // on every call to native code.
158 // 3. Running compiled Code
159 // Compiled code reads a global (Safepoint Polling) page that
160 // is set to fault if we are trying to get to a safepoint.
161 // 4. Blocked
162 // A thread which is blocked will not be allowed to return from the
163 // block condition until the safepoint operation is complete.
164 // 5. In VM or Transitioning between states
165 // If a Java thread is currently running in the VM or transitioning
166 // between states, the safepointing code will wait for the thread to
167 // block itself when it attempts transitions to a new state.
168 //
169 {
170 EventSafepointStateSynchronization sync_event;
171 int initial_running = 0;
172
173 _state = _synchronizing;
174
175 if (SafepointMechanism::uses_thread_local_poll()) {
176 // Arming the per thread poll while having _state != _not_synchronized means safepointing
177 log_trace(safepoint)("Setting thread local yield flag for threads");
178 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
179 // Make sure the threads start polling, it is time to yield.
180 SafepointMechanism::arm_local_poll(cur); // release store, global state -> local state
181 }
182 }
183 OrderAccess::fence(); // storestore|storeload, global state -> local state
184
185 // Flush all thread states to memory
186 if (!UseMembar) {
187 os::serialize_thread_states();
188 }
189
190 if (SafepointMechanism::uses_global_page_poll()) {
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
202 // Consider using active_processor_count() ... but that call is expensive.
203 int ncpus = os::processor_count() ;
204
205 #ifdef ASSERT
206 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
207 assert(cur->safepoint_state()->is_running(), "Illegal initial state");
208 // Clear the visited flag to ensure that the critical counts are collected properly.
209 cur->set_visited_for_critical_count(false);
210 }
211 #endif // ASSERT
212
213 if (SafepointTimeout)
214 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
215
216 // Iterate through all threads until it have been determined how to stop them all at a safepoint
217 unsigned int iterations = 0;
218 int steps = 0 ;
219 while(still_running > 0) {
220 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
221 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
222 ThreadSafepointState *cur_state = cur->safepoint_state();
223 if (cur_state->is_running()) {
224 cur_state->examine_state_of_thread();
225 if (!cur_state->is_running()) {
226 still_running--;
227 // consider adjusting steps downward:
228 // steps = 0
229 // steps -= NNN
230 // steps >>= 1
231 // steps = MIN(steps, 2000-100)
232 // if (iterations != 0) steps -= NNN
233 }
234 LogTarget(Trace, safepoint) lt;
235 if (lt.is_enabled()) {
236 ResourceMark rm;
237 LogStream ls(lt);
238 cur_state->print_on(&ls);
239 }
240 }
241 }
242
243 if (iterations == 0) {
244 initial_running = still_running;
245 if (PrintSafepointStatistics) {
246 begin_statistics(nof_threads, still_running);
247 }
248 }
249
250 if (still_running > 0) {
251 // Check for if it takes to long
252 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
253 print_safepoint_timeout(_spinning_timeout);
254 }
255
256 // Spin to avoid context switching.
257 // There's a tension between allowing the mutators to run (and rendezvous)
258 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that
259 // a mutator might otherwise use profitably to reach a safepoint. Excessive
260 // spinning by the VM thread on a saturated system can increase rendezvous latency.
261 // Blocking or yielding incur their own penalties in the form of context switching
262 // and the resultant loss of $ residency.
263 //
264 // Further complicating matters is that yield() does not work as naively expected
265 // on many platforms -- yield() does not guarantee that any other ready threads
266 // will run. As such we revert to naked_short_sleep() after some number of iterations.
267 // nakes_short_sleep() is implemented as a short unconditional sleep.
268 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
269 // can actually increase the time it takes the VM thread to detect that a system-wide
270 // stop-the-world safepoint has been reached. In a pathological scenario such as that
271 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
272 // In that case the mutators will be stalled waiting for the safepoint to complete and the
273 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread
274 // will eventually wake up and detect that all mutators are safe, at which point
275 // we'll again make progress.
276 //
277 // Beware too that that the VMThread typically runs at elevated priority.
278 // Its default priority is higher than the default mutator priority.
279 // Obviously, this complicates spinning.
280 //
281 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
282 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
283 //
284 // See the comments in synchronizer.cpp for additional remarks on spinning.
285 //
286 // In the future we might:
287 // 1. Modify the safepoint scheme to avoid potentially unbounded spinning.
288 // This is tricky as the path used by a thread exiting the JVM (say on
289 // on JNI call-out) simply stores into its state field. The burden
290 // is placed on the VM thread, which must poll (spin).
291 // 2. Find something useful to do while spinning. If the safepoint is GC-related
292 // we might aggressively scan the stacks of threads that are already safe.
293 // 3. Use Solaris schedctl to examine the state of the still-running mutators.
294 // If all the mutators are ONPROC there's no reason to sleep or yield.
295 // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
296 // 5. Check system saturation. If the system is not fully saturated then
297 // simply spin and avoid sleep/yield.
298 // 6. As still-running mutators rendezvous they could unpark the sleeping
299 // VMthread. This works well for still-running mutators that become
300 // safe. The VMthread must still poll for mutators that call-out.
301 // 7. Drive the policy on time-since-begin instead of iterations.
302 // 8. Consider making the spin duration a function of the # of CPUs:
303 // Spin = (((ncpus-1) * M) + K) + F(still_running)
304 // Alternately, instead of counting iterations of the outer loop
305 // we could count the # of threads visited in the inner loop, above.
306 // 9. On windows consider using the return value from SwitchThreadTo()
307 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
308
309 if (SafepointMechanism::uses_global_page_poll() && int(iterations) == DeferPollingPageLoopCount) {
310 guarantee (PageArmed == 0, "invariant") ;
311 PageArmed = 1 ;
312 os::make_polling_page_unreadable();
313 }
314
315 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
316 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
317 ++steps ;
318 if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
319 SpinPause() ; // MP-Polite spin
320 } else
321 if (steps < DeferThrSuspendLoopCount) {
322 os::naked_yield() ;
323 } else {
324 os::naked_short_sleep(1);
325 }
326
327 iterations ++ ;
328 }
329 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
330 }
331 assert(still_running == 0, "sanity check");
332
333 if (PrintSafepointStatistics) {
334 update_statistics_on_spin_end();
335 }
336
337 if (sync_event.should_commit()) {
338 // Group this event together with the ones committed after the counter is increased
339 sync_event.set_safepointId(safepoint_counter() + 1);
340 sync_event.set_initialThreadCount(initial_running);
341 sync_event.set_runningThreadCount(_waiting_to_block);
342 sync_event.set_iterations(iterations);
343 sync_event.commit();
344 }
345 } // EventSafepointStateSynchronization destroyed here.
346
347 // wait until all threads are stopped
348 {
349 EventSafepointWaitBlocked wait_blocked_event;
350 int initial_waiting_to_block = _waiting_to_block;
351
352 while (_waiting_to_block > 0) {
353 log_debug(safepoint)("Waiting for %d thread(s) to block", _waiting_to_block);
354 if (!SafepointTimeout || timeout_error_printed) {
355 Safepoint_lock->wait(true); // true, means with no safepoint checks
356 } else {
357 // Compute remaining time
358 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
359
360 // If there is no remaining time, then there is an error
361 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
362 print_safepoint_timeout(_blocking_timeout);
363 }
364 }
365 }
366 assert(_waiting_to_block == 0, "sanity check");
367
368 #ifndef PRODUCT
369 if (SafepointTimeout) {
370 jlong current_time = os::javaTimeNanos();
371 if (safepoint_limit_time < current_time) {
372 tty->print_cr("# SafepointSynchronize: Finished after "
373 INT64_FORMAT_W(6) " ms",
374 (int64_t)((current_time - safepoint_limit_time) / MICROUNITS +
375 (jlong)SafepointTimeoutDelay));
376 }
377 }
378 #endif
379
380 assert((_safepoint_counter & 0x1) == 0, "must be even");
381 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
382 _safepoint_counter ++;
383
384 // Record state
385 _state = _synchronized;
386
387 OrderAccess::fence();
388
389 if (wait_blocked_event.should_commit()) {
390 wait_blocked_event.set_safepointId(safepoint_counter());
391 wait_blocked_event.set_runningThreadCount(initial_waiting_to_block);
392 wait_blocked_event.commit();
393 }
394 } // EventSafepointWaitBlocked
395
396 #ifdef ASSERT
397 // Make sure all the threads were visited.
398 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur = jtiwh.next(); ) {
399 assert(cur->was_visited_for_critical_count(), "missed a thread");
400 }
401 #endif // ASSERT
402
403 // Update the count of active JNI critical regions
404 GCLocker::set_jni_lock_count(_current_jni_active_count);
405
406 if (log_is_enabled(Debug, safepoint)) {
407 log_debug(safepoint)("Entering safepoint region: %s", VMThread::vm_safepoint_description());
408 }
409
410 RuntimeService::record_safepoint_synchronized();
411 if (PrintSafepointStatistics) {
412 update_statistics_on_sync_end(os::javaTimeNanos());
413 }
414
415 // Call stuff that needs to be run when a safepoint is just about to be completed
416 {
417 EventSafepointCleanup cleanup_event;
418 do_cleanup_tasks();
419 if (cleanup_event.should_commit()) {
420 cleanup_event.set_safepointId(safepoint_counter());
421 cleanup_event.commit();
422 }
423 }
424
425 if (PrintSafepointStatistics) {
426 // Record how much time spend on the above cleanup tasks
427 update_statistics_on_cleanup_end(os::javaTimeNanos());
428 }
429 if (begin_event.should_commit()) {
430 begin_event.set_safepointId(safepoint_counter());
431 begin_event.set_totalThreadCount(nof_threads);
432 begin_event.set_jniCriticalThreadCount(_current_jni_active_count);
433 begin_event.commit();
434 }
435 }
436
437 // Wake up all threads, so they are ready to resume execution after the safepoint
438 // operation has been carried out
439 void SafepointSynchronize::end() {
440 EventSafepointEnd event;
441 int safepoint_id = safepoint_counter(); // Keep the odd counter as "id"
442
443 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
444 assert((_safepoint_counter & 0x1) == 1, "must be odd");
445 _safepoint_counter ++;
446 // memory fence isn't required here since an odd _safepoint_counter
447 // value can do no harm and a fence is issued below anyway.
448
449 DEBUG_ONLY(Thread* myThread = Thread::current();)
450 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
451
452 if (PrintSafepointStatistics) {
453 end_statistics(os::javaTimeNanos());
454 }
455
456 #ifdef ASSERT
457 // A pending_exception cannot be installed during a safepoint. The threads
458 // may install an async exception after they come back from a safepoint into
459 // pending_exception after they unblock. But that should happen later.
460 for (JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
461 assert (!(cur->has_pending_exception() &&
462 cur->safepoint_state()->is_at_poll_safepoint()),
463 "safepoint installed a pending exception");
464 }
465 #endif // ASSERT
466
467 if (PageArmed) {
468 assert(SafepointMechanism::uses_global_page_poll(), "sanity");
469 // Make polling safepoint aware
470 os::make_polling_page_readable();
471 PageArmed = 0 ;
472 }
473
474 if (SafepointMechanism::uses_global_page_poll()) {
475 // Remove safepoint check from interpreter
476 Interpreter::ignore_safepoints();
477 }
478
479 {
480 MutexLocker mu(Safepoint_lock);
481
482 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
483
484 if (SafepointMechanism::uses_thread_local_poll()) {
485 _state = _not_synchronized;
486 OrderAccess::storestore(); // global state -> local state
487 for (JavaThread *current = Threads::first(); current; current = current->next()) {
488 ThreadSafepointState* cur_state = current->safepoint_state();
489 cur_state->restart(); // TSS _running
490 SafepointMechanism::disarm_local_poll(current); // release store, local state -> polling page
491 }
492 log_debug(safepoint)("Leaving safepoint region");
493 } else {
494 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
495 // when they get restarted.
496 _state = _not_synchronized;
497 OrderAccess::fence();
498
499 log_debug(safepoint)("Leaving safepoint region");
500
501 // Start suspended threads
502 for (JavaThread *current = Threads::first(); current; current = current->next()) {
503 // A problem occurring on Solaris is when attempting to restart threads
504 // the first #cpus - 1 go well, but then the VMThread is preempted when we get
505 // to the next one (since it has been running the longest). We then have
506 // to wait for a cpu to become available before we can continue restarting
507 // threads.
508 // FIXME: This causes the performance of the VM to degrade when active and with
509 // large numbers of threads. Apparently this is due to the synchronous nature
510 // of suspending threads.
511 //
512 // TODO-FIXME: the comments above are vestigial and no longer apply.
513 // Furthermore, using solaris' schedctl in this particular context confers no benefit
514 if (VMThreadHintNoPreempt) {
515 os::hint_no_preempt();
516 }
517 ThreadSafepointState* cur_state = current->safepoint_state();
518 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
519 cur_state->restart();
520 assert(cur_state->is_running(), "safepoint state has not been reset");
521 }
522 }
523
524 RuntimeService::record_safepoint_end();
525
526 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads
527 // blocked in signal_thread_blocked
528 Threads_lock->unlock();
529
530 }
531 Universe::heap()->safepoint_synchronize_end();
532 // record this time so VMThread can keep track how much time has elapsed
533 // since last safepoint.
534 _end_of_last_safepoint = os::javaTimeMillis();
535
536 if (event.should_commit()) {
537 event.set_safepointId(safepoint_id);
538 event.commit();
539 }
540 }
541
542 bool SafepointSynchronize::is_cleanup_needed() {
543 // Need a safepoint if there are many monitors to deflate.
544 if (ObjectSynchronizer::is_cleanup_needed()) return true;
545 // Need a safepoint if some inline cache buffers is non-empty
546 if (!InlineCacheBuffer::is_empty()) return true;
547 return false;
548 }
549
550 static void event_safepoint_cleanup_task_commit(EventSafepointCleanupTask& event, const char* name) {
551 if (event.should_commit()) {
552 event.set_safepointId(SafepointSynchronize::safepoint_counter());
553 event.set_name(name);
554 event.commit();
555 }
556 }
557
558 class ParallelSPCleanupThreadClosure : public ThreadClosure {
559 private:
560 CodeBlobClosure* _nmethod_cl;
561 DeflateMonitorCounters* _counters;
562
563 public:
564 ParallelSPCleanupThreadClosure(DeflateMonitorCounters* counters) :
565 _counters(counters),
566 _nmethod_cl(NMethodSweeper::prepare_mark_active_nmethods()) {}
567
568 void do_thread(Thread* thread) {
569 ObjectSynchronizer::deflate_thread_local_monitors(thread, _counters);
570 if (_nmethod_cl != NULL && thread->is_Java_thread() &&
571 ! thread->is_Code_cache_sweeper_thread()) {
572 JavaThread* jt = (JavaThread*) thread;
573 jt->nmethods_do(_nmethod_cl);
574 }
575 }
576 };
577
578 class ParallelSPCleanupTask : public AbstractGangTask {
579 private:
580 SubTasksDone _subtasks;
581 ParallelSPCleanupThreadClosure _cleanup_threads_cl;
582 uint _num_workers;
583 DeflateMonitorCounters* _counters;
584 public:
585 ParallelSPCleanupTask(uint num_workers, DeflateMonitorCounters* counters) :
586 AbstractGangTask("Parallel Safepoint Cleanup"),
587 _cleanup_threads_cl(ParallelSPCleanupThreadClosure(counters)),
588 _num_workers(num_workers),
589 _subtasks(SubTasksDone(SafepointSynchronize::SAFEPOINT_CLEANUP_NUM_TASKS)),
590 _counters(counters) {}
591
592 void work(uint worker_id) {
593 // All threads deflate monitors and mark nmethods (if necessary).
594 Threads::possibly_parallel_threads_do(true, &_cleanup_threads_cl);
595
596 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_DEFLATE_MONITORS)) {
597 const char* name = "deflating idle monitors";
598 EventSafepointCleanupTask event;
599 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
600 ObjectSynchronizer::deflate_idle_monitors(_counters);
601 event_safepoint_cleanup_task_commit(event, name);
602 }
603
604 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_UPDATE_INLINE_CACHES)) {
605 const char* name = "updating inline caches";
606 EventSafepointCleanupTask event;
607 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
608 InlineCacheBuffer::update_inline_caches();
609 event_safepoint_cleanup_task_commit(event, name);
610 }
611
612 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_COMPILATION_POLICY)) {
613 const char* name = "compilation policy safepoint handler";
614 EventSafepointCleanupTask event;
615 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
616 CompilationPolicy::policy()->do_safepoint_work();
617 event_safepoint_cleanup_task_commit(event, name);
618 }
619
620 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_SYMBOL_TABLE_REHASH)) {
621 if (SymbolTable::needs_rehashing()) {
622 const char* name = "rehashing symbol table";
623 EventSafepointCleanupTask event;
624 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
625 SymbolTable::rehash_table();
626 event_safepoint_cleanup_task_commit(event, name);
627 }
628 }
629
630 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_STRING_TABLE_REHASH)) {
631 if (StringTable::needs_rehashing()) {
632 const char* name = "rehashing string table";
633 EventSafepointCleanupTask event;
634 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
635 StringTable::rehash_table();
636 event_safepoint_cleanup_task_commit(event, name);
637 }
638 }
639
640 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_CLD_PURGE)) {
641 // CMS delays purging the CLDG until the beginning of the next safepoint and to
642 // make sure concurrent sweep is done
643 const char* name = "purging class loader data graph";
644 EventSafepointCleanupTask event;
645 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
646 ClassLoaderDataGraph::purge_if_needed();
647 event_safepoint_cleanup_task_commit(event, name);
648 }
649
650 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_SYSTEM_DICTIONARY_RESIZE)) {
651 const char* name = "resizing system dictionaries";
652 EventSafepointCleanupTask event;
653 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
654 ClassLoaderDataGraph::resize_if_needed();
655 event_safepoint_cleanup_task_commit(event, name);
656 }
657 _subtasks.all_tasks_completed(_num_workers);
658 }
659 };
660
661 // Various cleaning tasks that should be done periodically at safepoints.
662 void SafepointSynchronize::do_cleanup_tasks() {
663
664 TraceTime timer("safepoint cleanup tasks", TRACETIME_LOG(Info, safepoint, cleanup));
665
666 // Prepare for monitor deflation.
667 DeflateMonitorCounters deflate_counters;
668 ObjectSynchronizer::prepare_deflate_idle_monitors(&deflate_counters);
669
670 CollectedHeap* heap = Universe::heap();
671 assert(heap != NULL, "heap not initialized yet?");
672 WorkGang* cleanup_workers = heap->get_safepoint_workers();
673 if (cleanup_workers != NULL) {
674 // Parallel cleanup using GC provided thread pool.
675 uint num_cleanup_workers = cleanup_workers->active_workers();
676 ParallelSPCleanupTask cleanup(num_cleanup_workers, &deflate_counters);
677 StrongRootsScope srs(num_cleanup_workers);
678 cleanup_workers->run_task(&cleanup);
679 } else {
680 // Serial cleanup using VMThread.
681 ParallelSPCleanupTask cleanup(1, &deflate_counters);
682 StrongRootsScope srs(1);
683 cleanup.work(0);
684 }
685
686 // Finish monitor deflation.
687 ObjectSynchronizer::finish_deflate_idle_monitors(&deflate_counters);
688 }
689
690
691 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
692 switch(state) {
693 case _thread_in_native:
694 // native threads are safe if they have no java stack or have walkable stack
695 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
696
697 // blocked threads should have already have walkable stack
698 case _thread_blocked:
699 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
700 return true;
701
702 default:
703 return false;
704 }
705 }
706
707
708 // See if the thread is running inside a lazy critical native and
709 // update the thread critical count if so. Also set a suspend flag to
710 // cause the native wrapper to return into the JVM to do the unlock
711 // once the native finishes.
712 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
713 if (state == _thread_in_native &&
714 thread->has_last_Java_frame() &&
715 thread->frame_anchor()->walkable()) {
716 // This thread might be in a critical native nmethod so look at
717 // the top of the stack and increment the critical count if it
718 // is.
719 frame wrapper_frame = thread->last_frame();
720 CodeBlob* stub_cb = wrapper_frame.cb();
721 if (stub_cb != NULL &&
722 stub_cb->is_nmethod() &&
723 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
724 // A thread could potentially be in a critical native across
725 // more than one safepoint, so only update the critical state on
726 // the first one. When it returns it will perform the unlock.
727 if (!thread->do_critical_native_unlock()) {
728 #ifdef ASSERT
729 if (!thread->in_critical()) {
730 GCLocker::increment_debug_jni_lock_count();
731 }
732 #endif
733 thread->enter_critical();
734 // Make sure the native wrapper calls back on return to
735 // perform the needed critical unlock.
736 thread->set_critical_native_unlock();
737 }
738 }
739 }
740 }
741
742
743
744 // -------------------------------------------------------------------------------------------------------
745 // Implementation of Safepoint callback point
746
747 void SafepointSynchronize::block(JavaThread *thread) {
748 assert(thread != NULL, "thread must be set");
749 assert(thread->is_Java_thread(), "not a Java thread");
750
751 // Threads shouldn't block if they are in the middle of printing, but...
752 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
753
754 // Only bail from the block() call if the thread is gone from the
755 // thread list; starting to exit should still block.
756 if (thread->is_terminated()) {
757 // block current thread if we come here from native code when VM is gone
758 thread->block_if_vm_exited();
759
760 // otherwise do nothing
761 return;
762 }
763
764 JavaThreadState state = thread->thread_state();
765 thread->frame_anchor()->make_walkable(thread);
766
767 // Check that we have a valid thread_state at this point
768 switch(state) {
769 case _thread_in_vm_trans:
770 case _thread_in_Java: // From compiled code
771
772 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
773 // we pretend we are still in the VM.
774 thread->set_thread_state(_thread_in_vm);
775
776 if (is_synchronizing()) {
777 Atomic::inc (&TryingToBlock) ;
778 }
779
780 // We will always be holding the Safepoint_lock when we are examine the state
781 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
782 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
783 Safepoint_lock->lock_without_safepoint_check();
784 if (is_synchronizing()) {
785 // Decrement the number of threads to wait for and signal vm thread
786 assert(_waiting_to_block > 0, "sanity check");
787 _waiting_to_block--;
788 thread->safepoint_state()->set_has_called_back(true);
789
790 DEBUG_ONLY(thread->set_visited_for_critical_count(true));
791 if (thread->in_critical()) {
792 // Notice that this thread is in a critical section
793 increment_jni_active_count();
794 }
795
796 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
797 if (_waiting_to_block == 0) {
798 Safepoint_lock->notify_all();
799 }
800 }
801
802 // We transition the thread to state _thread_blocked here, but
803 // we can't do our usual check for external suspension and then
804 // self-suspend after the lock_without_safepoint_check() call
805 // below because we are often called during transitions while
806 // we hold different locks. That would leave us suspended while
807 // holding a resource which results in deadlocks.
808 thread->set_thread_state(_thread_blocked);
809 Safepoint_lock->unlock();
810
811 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
812 // the entire safepoint, the threads will all line up here during the safepoint.
813 Threads_lock->lock_without_safepoint_check();
814 // restore original state. This is important if the thread comes from compiled code, so it
815 // will continue to execute with the _thread_in_Java state.
816 thread->set_thread_state(state);
817 Threads_lock->unlock();
818 break;
819
820 case _thread_in_native_trans:
821 case _thread_blocked_trans:
822 case _thread_new_trans:
823 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
824 thread->print_thread_state();
825 fatal("Deadlock in safepoint code. "
826 "Should have called back to the VM before blocking.");
827 }
828
829 // We transition the thread to state _thread_blocked here, but
830 // we can't do our usual check for external suspension and then
831 // self-suspend after the lock_without_safepoint_check() call
832 // below because we are often called during transitions while
833 // we hold different locks. That would leave us suspended while
834 // holding a resource which results in deadlocks.
835 thread->set_thread_state(_thread_blocked);
836
837 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
838 // the safepoint code might still be waiting for it to block. We need to change the state here,
839 // so it can see that it is at a safepoint.
840
841 // Block until the safepoint operation is completed.
842 Threads_lock->lock_without_safepoint_check();
843
844 // Restore state
845 thread->set_thread_state(state);
846
847 Threads_lock->unlock();
848 break;
849
850 default:
851 fatal("Illegal threadstate encountered: %d", state);
852 }
853
854 // Check for pending. async. exceptions or suspends - except if the
855 // thread was blocked inside the VM. has_special_runtime_exit_condition()
856 // is called last since it grabs a lock and we only want to do that when
857 // we must.
858 //
859 // Note: we never deliver an async exception at a polling point as the
860 // compiler may not have an exception handler for it. The polling
861 // code will notice the async and deoptimize and the exception will
862 // be delivered. (Polling at a return point is ok though). Sure is
863 // a lot of bother for a deprecated feature...
864 //
865 // We don't deliver an async exception if the thread state is
866 // _thread_in_native_trans so JNI functions won't be called with
867 // a surprising pending exception. If the thread state is going back to java,
868 // async exception is checked in check_special_condition_for_native_trans().
869
870 if (state != _thread_blocked_trans &&
871 state != _thread_in_vm_trans &&
872 thread->has_special_runtime_exit_condition()) {
873 thread->handle_special_runtime_exit_condition(
874 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
875 }
876 }
877
878 // ------------------------------------------------------------------------------------------------------
879 // Exception handlers
880
881
882 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
883 assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
884 assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
885 if (!ThreadLocalHandshakes) {
886 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
887 }
888
889 if (ShowSafepointMsgs) {
890 tty->print("handle_polling_page_exception: ");
891 }
892
893 if (PrintSafepointStatistics) {
894 inc_page_trap_count();
895 }
896
897 ThreadSafepointState* state = thread->safepoint_state();
898
899 state->handle_polling_page_exception();
900 }
901
902
903 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
904 if (!timeout_error_printed) {
905 timeout_error_printed = true;
906 // Print out the thread info which didn't reach the safepoint for debugging
907 // purposes (useful when there are lots of threads in the debugger).
908 tty->cr();
909 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
910 if (reason == _spinning_timeout) {
911 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
912 } else if (reason == _blocking_timeout) {
913 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
914 }
915
916 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
917 ThreadSafepointState *cur_state;
918 ResourceMark rm;
919 for (JavaThread *cur_thread = Threads::first(); cur_thread;
920 cur_thread = cur_thread->next()) {
921 cur_state = cur_thread->safepoint_state();
922
923 if (cur_thread->thread_state() != _thread_blocked &&
924 ((reason == _spinning_timeout && cur_state->is_running()) ||
925 (reason == _blocking_timeout && !cur_state->has_called_back()))) {
926 tty->print("# ");
927 cur_thread->print();
928 tty->cr();
929 }
930 }
931 tty->print_cr("# SafepointSynchronize::begin: (End of list)");
932 }
933
934 // To debug the long safepoint, specify both DieOnSafepointTimeout &
935 // ShowMessageBoxOnError.
936 if (DieOnSafepointTimeout) {
937 fatal("Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
938 SafepointTimeoutDelay, VMThread::vm_safepoint_description());
939 }
940 }
941
942
943 // -------------------------------------------------------------------------------------------------------
944 // Implementation of ThreadSafepointState
945
946 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
947 _thread = thread;
948 _type = _running;
949 _has_called_back = false;
950 _at_poll_safepoint = false;
951 }
952
953 void ThreadSafepointState::create(JavaThread *thread) {
954 ThreadSafepointState *state = new ThreadSafepointState(thread);
955 thread->set_safepoint_state(state);
956 }
957
958 void ThreadSafepointState::destroy(JavaThread *thread) {
959 if (thread->safepoint_state()) {
960 delete(thread->safepoint_state());
961 thread->set_safepoint_state(NULL);
962 }
963 }
964
965 void ThreadSafepointState::examine_state_of_thread() {
966 assert(is_running(), "better be running or just have hit safepoint poll");
967
968 JavaThreadState state = _thread->thread_state();
969
970 // Save the state at the start of safepoint processing.
971 _orig_thread_state = state;
972
973 // Check for a thread that is suspended. Note that thread resume tries
974 // to grab the Threads_lock which we own here, so a thread cannot be
975 // resumed during safepoint synchronization.
976
977 // We check to see if this thread is suspended without locking to
978 // avoid deadlocking with a third thread that is waiting for this
979 // thread to be suspended. The third thread can notice the safepoint
980 // that we're trying to start at the beginning of its SR_lock->wait()
981 // call. If that happens, then the third thread will block on the
982 // safepoint while still holding the underlying SR_lock. We won't be
983 // able to get the SR_lock and we'll deadlock.
984 //
985 // We don't need to grab the SR_lock here for two reasons:
986 // 1) The suspend flags are both volatile and are set with an
987 // Atomic::cmpxchg() call so we should see the suspended
988 // state right away.
989 // 2) We're being called from the safepoint polling loop; if
990 // we don't see the suspended state on this iteration, then
991 // we'll come around again.
992 //
993 bool is_suspended = _thread->is_ext_suspended();
994 if (is_suspended) {
995 roll_forward(_at_safepoint);
996 return;
997 }
998
999 // Some JavaThread states have an initial safepoint state of
1000 // running, but are actually at a safepoint. We will happily
1001 // agree and update the safepoint state here.
1002 if (SafepointSynchronize::safepoint_safe(_thread, state)) {
1003 SafepointSynchronize::check_for_lazy_critical_native(_thread, state);
1004 roll_forward(_at_safepoint);
1005 return;
1006 }
1007
1008 if (state == _thread_in_vm) {
1009 roll_forward(_call_back);
1010 return;
1011 }
1012
1013 // All other thread states will continue to run until they
1014 // transition and self-block in state _blocked
1015 // Safepoint polling in compiled code causes the Java threads to do the same.
1016 // Note: new threads may require a malloc so they must be allowed to finish
1017
1018 assert(is_running(), "examine_state_of_thread on non-running thread");
1019 return;
1020 }
1021
1022 // Returns true is thread could not be rolled forward at present position.
1023 void ThreadSafepointState::roll_forward(suspend_type type) {
1024 _type = type;
1025
1026 switch(_type) {
1027 case _at_safepoint:
1028 SafepointSynchronize::signal_thread_at_safepoint();
1029 DEBUG_ONLY(_thread->set_visited_for_critical_count(true));
1030 if (_thread->in_critical()) {
1031 // Notice that this thread is in a critical section
1032 SafepointSynchronize::increment_jni_active_count();
1033 }
1034 break;
1035
1036 case _call_back:
1037 set_has_called_back(false);
1038 break;
1039
1040 case _running:
1041 default:
1042 ShouldNotReachHere();
1043 }
1044 }
1045
1046 void ThreadSafepointState::restart() {
1047 switch(type()) {
1048 case _at_safepoint:
1049 case _call_back:
1050 break;
1051
1052 case _running:
1053 default:
1054 tty->print_cr("restart thread " INTPTR_FORMAT " with state %d",
1055 p2i(_thread), _type);
1056 _thread->print();
1057 ShouldNotReachHere();
1058 }
1059 _type = _running;
1060 set_has_called_back(false);
1061 }
1062
1063
1064 void ThreadSafepointState::print_on(outputStream *st) const {
1065 const char *s = NULL;
1066
1067 switch(_type) {
1068 case _running : s = "_running"; break;
1069 case _at_safepoint : s = "_at_safepoint"; break;
1070 case _call_back : s = "_call_back"; break;
1071 default:
1072 ShouldNotReachHere();
1073 }
1074
1075 st->print_cr("Thread: " INTPTR_FORMAT
1076 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
1077 p2i(_thread), _thread->osthread()->thread_id(), s, _has_called_back,
1078 _at_poll_safepoint);
1079
1080 _thread->print_thread_state_on(st);
1081 }
1082
1083 // ---------------------------------------------------------------------------------------------------------------------
1084
1085 // Block the thread at poll or poll return for safepoint/handshake.
1086 void ThreadSafepointState::handle_polling_page_exception() {
1087
1088 // Check state. block() will set thread state to thread_in_vm which will
1089 // cause the safepoint state _type to become _call_back.
1090 suspend_type t = type();
1091 assert(!SafepointMechanism::uses_global_page_poll() || t == ThreadSafepointState::_running,
1092 "polling page exception on thread not running state: %u", uint(t));
1093
1094 // Step 1: Find the nmethod from the return address
1095 if (ShowSafepointMsgs && Verbose) {
1096 tty->print_cr("Polling page exception at " INTPTR_FORMAT, p2i(thread()->saved_exception_pc()));
1097 }
1098 address real_return_addr = thread()->saved_exception_pc();
1099
1100 CodeBlob *cb = CodeCache::find_blob(real_return_addr);
1101 assert(cb != NULL && cb->is_compiled(), "return address should be in nmethod");
1102 CompiledMethod* nm = (CompiledMethod*)cb;
1103
1104 // Find frame of caller
1105 frame stub_fr = thread()->last_frame();
1106 CodeBlob* stub_cb = stub_fr.cb();
1107 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
1108 RegisterMap map(thread(), true);
1109 frame caller_fr = stub_fr.sender(&map);
1110
1111 // Should only be poll_return or poll
1112 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
1113
1114 // This is a poll immediately before a return. The exception handling code
1115 // has already had the effect of causing the return to occur, so the execution
1116 // will continue immediately after the call. In addition, the oopmap at the
1117 // return point does not mark the return value as an oop (if it is), so
1118 // it needs a handle here to be updated.
1119 if( nm->is_at_poll_return(real_return_addr) ) {
1120 // See if return type is an oop.
1121 bool return_oop = nm->method()->is_returning_oop();
1122 Handle return_value;
1123 if (return_oop) {
1124 // The oop result has been saved on the stack together with all
1125 // the other registers. In order to preserve it over GCs we need
1126 // to keep it in a handle.
1127 oop result = caller_fr.saved_oop_result(&map);
1128 assert(oopDesc::is_oop_or_null(result), "must be oop");
1129 return_value = Handle(thread(), result);
1130 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
1131 }
1132
1133 // Block the thread
1134 SafepointMechanism::block_if_requested(thread());
1135
1136 // restore oop result, if any
1137 if (return_oop) {
1138 caller_fr.set_saved_oop_result(&map, return_value());
1139 }
1140 }
1141
1142 // This is a safepoint poll. Verify the return address and block.
1143 else {
1144 set_at_poll_safepoint(true);
1145
1146 // verify the blob built the "return address" correctly
1147 assert(real_return_addr == caller_fr.pc(), "must match");
1148
1149 // Block the thread
1150 SafepointMechanism::block_if_requested(thread());
1151 set_at_poll_safepoint(false);
1152
1153 // If we have a pending async exception deoptimize the frame
1154 // as otherwise we may never deliver it.
1155 if (thread()->has_async_condition()) {
1156 ThreadInVMfromJavaNoAsyncException __tiv(thread());
1157 Deoptimization::deoptimize_frame(thread(), caller_fr.id());
1158 }
1159
1160 // If an exception has been installed we must check for a pending deoptimization
1161 // Deoptimize frame if exception has been thrown.
1162
1163 if (thread()->has_pending_exception() ) {
1164 RegisterMap map(thread(), true);
1165 frame caller_fr = stub_fr.sender(&map);
1166 if (caller_fr.is_deoptimized_frame()) {
1167 // The exception patch will destroy registers that are still
1168 // live and will be needed during deoptimization. Defer the
1169 // Async exception should have deferred the exception until the
1170 // next safepoint which will be detected when we get into
1171 // the interpreter so if we have an exception now things
1172 // are messed up.
1173
1174 fatal("Exception installed and deoptimization is pending");
1175 }
1176 }
1177 }
1178 }
1179
1180
1181 //
1182 // Statistics & Instrumentations
1183 //
1184 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL;
1185 jlong SafepointSynchronize::_safepoint_begin_time = 0;
1186 int SafepointSynchronize::_cur_stat_index = 0;
1187 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
1188 julong SafepointSynchronize::_coalesced_vmop_count = 0;
1189 jlong SafepointSynchronize::_max_sync_time = 0;
1190 jlong SafepointSynchronize::_max_vmop_time = 0;
1191 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f;
1192
1193 static jlong cleanup_end_time = 0;
1194 static bool need_to_track_page_armed_status = false;
1195 static bool init_done = false;
1196
1197 // Helper method to print the header.
1198 static void print_header() {
1199 // The number of spaces is significant here, and should match the format
1200 // specifiers in print_statistics().
1201
1202 tty->print(" vmop "
1203 "[ threads: total initially_running wait_to_block ]"
1204 "[ time: spin block sync cleanup vmop ] ");
1205
1206 // no page armed status printed out if it is always armed.
1207 if (need_to_track_page_armed_status) {
1208 tty->print("page_armed ");
1209 }
1210
1211 tty->print_cr("page_trap_count");
1212 }
1213
1214 void SafepointSynchronize::deferred_initialize_stat() {
1215 if (init_done) return;
1216
1217 // If PrintSafepointStatisticsTimeout is specified, the statistics data will
1218 // be printed right away, in which case, _safepoint_stats will regress to
1219 // a single element array. Otherwise, it is a circular ring buffer with default
1220 // size of PrintSafepointStatisticsCount.
1221 int stats_array_size;
1222 if (PrintSafepointStatisticsTimeout > 0) {
1223 stats_array_size = 1;
1224 PrintSafepointStatistics = true;
1225 } else {
1226 stats_array_size = PrintSafepointStatisticsCount;
1227 }
1228 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
1229 * sizeof(SafepointStats), mtInternal);
1230 guarantee(_safepoint_stats != NULL,
1231 "not enough memory for safepoint instrumentation data");
1232
1233 if (DeferPollingPageLoopCount >= 0) {
1234 need_to_track_page_armed_status = true;
1235 }
1236 init_done = true;
1237 }
1238
1239 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
1240 assert(init_done, "safepoint statistics array hasn't been initialized");
1241 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1242
1243 spstat->_time_stamp = _ts_of_current_safepoint;
1244
1245 VM_Operation *op = VMThread::vm_operation();
1246 spstat->_vmop_type = (op != NULL ? op->type() : -1);
1247 if (op != NULL) {
1248 _safepoint_reasons[spstat->_vmop_type]++;
1249 }
1250
1251 spstat->_nof_total_threads = nof_threads;
1252 spstat->_nof_initial_running_threads = nof_running;
1253 spstat->_nof_threads_hit_page_trap = 0;
1254
1255 // Records the start time of spinning. The real time spent on spinning
1256 // will be adjusted when spin is done. Same trick is applied for time
1257 // spent on waiting for threads to block.
1258 if (nof_running != 0) {
1259 spstat->_time_to_spin = os::javaTimeNanos();
1260 } else {
1261 spstat->_time_to_spin = 0;
1262 }
1263 }
1264
1265 void SafepointSynchronize::update_statistics_on_spin_end() {
1266 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1267
1268 jlong cur_time = os::javaTimeNanos();
1269
1270 spstat->_nof_threads_wait_to_block = _waiting_to_block;
1271 if (spstat->_nof_initial_running_threads != 0) {
1272 spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
1273 }
1274
1275 if (need_to_track_page_armed_status) {
1276 spstat->_page_armed = (PageArmed == 1);
1277 }
1278
1279 // Records the start time of waiting for to block. Updated when block is done.
1280 if (_waiting_to_block != 0) {
1281 spstat->_time_to_wait_to_block = cur_time;
1282 } else {
1283 spstat->_time_to_wait_to_block = 0;
1284 }
1285 }
1286
1287 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
1288 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1289
1290 if (spstat->_nof_threads_wait_to_block != 0) {
1291 spstat->_time_to_wait_to_block = end_time -
1292 spstat->_time_to_wait_to_block;
1293 }
1294
1295 // Records the end time of sync which will be used to calculate the total
1296 // vm operation time. Again, the real time spending in syncing will be deducted
1297 // from the start of the sync time later when end_statistics is called.
1298 spstat->_time_to_sync = end_time - _safepoint_begin_time;
1299 if (spstat->_time_to_sync > _max_sync_time) {
1300 _max_sync_time = spstat->_time_to_sync;
1301 }
1302
1303 spstat->_time_to_do_cleanups = end_time;
1304 }
1305
1306 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
1307 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1308
1309 // Record how long spent in cleanup tasks.
1310 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
1311
1312 cleanup_end_time = end_time;
1313 }
1314
1315 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
1316 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1317
1318 // Update the vm operation time.
1319 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time;
1320 if (spstat->_time_to_exec_vmop > _max_vmop_time) {
1321 _max_vmop_time = spstat->_time_to_exec_vmop;
1322 }
1323 // Only the sync time longer than the specified
1324 // PrintSafepointStatisticsTimeout will be printed out right away.
1325 // By default, it is -1 meaning all samples will be put into the list.
1326 if ( PrintSafepointStatisticsTimeout > 0) {
1327 if (spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
1328 print_statistics();
1329 }
1330 } else {
1331 // The safepoint statistics will be printed out when the _safepoin_stats
1332 // array fills up.
1333 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) {
1334 print_statistics();
1335 _cur_stat_index = 0;
1336 } else {
1337 _cur_stat_index++;
1338 }
1339 }
1340 }
1341
1342 void SafepointSynchronize::print_statistics() {
1343 for (int index = 0; index <= _cur_stat_index; index++) {
1344 if (index % 30 == 0) {
1345 print_header();
1346 }
1347 SafepointStats* sstats = &_safepoint_stats[index];
1348 tty->print("%8.3f: ", sstats->_time_stamp);
1349 tty->print("%-30s [ "
1350 INT32_FORMAT_W(8) " " INT32_FORMAT_W(17) " " INT32_FORMAT_W(13) " "
1351 "]",
1352 (sstats->_vmop_type == -1 ? "no vm operation" : VM_Operation::name(sstats->_vmop_type)),
1353 sstats->_nof_total_threads,
1354 sstats->_nof_initial_running_threads,
1355 sstats->_nof_threads_wait_to_block);
1356 // "/ MICROUNITS " is to convert the unit from nanos to millis.
1357 tty->print("[ "
1358 INT64_FORMAT_W(7) " " INT64_FORMAT_W(7) " "
1359 INT64_FORMAT_W(7) " " INT64_FORMAT_W(7) " "
1360 INT64_FORMAT_W(7) " ] ",
1361 (int64_t)(sstats->_time_to_spin / MICROUNITS),
1362 (int64_t)(sstats->_time_to_wait_to_block / MICROUNITS),
1363 (int64_t)(sstats->_time_to_sync / MICROUNITS),
1364 (int64_t)(sstats->_time_to_do_cleanups / MICROUNITS),
1365 (int64_t)(sstats->_time_to_exec_vmop / MICROUNITS));
1366
1367 if (need_to_track_page_armed_status) {
1368 tty->print(INT32_FORMAT_W(10) " ", sstats->_page_armed);
1369 }
1370 tty->print_cr(INT32_FORMAT_W(15) " ", sstats->_nof_threads_hit_page_trap);
1371 }
1372 }
1373
1374 // This method will be called when VM exits. It will first call
1375 // print_statistics to print out the rest of the sampling. Then
1376 // it tries to summarize the sampling.
1377 void SafepointSynchronize::print_stat_on_exit() {
1378 if (_safepoint_stats == NULL) return;
1379
1380 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1381
1382 // During VM exit, end_statistics may not get called and in that
1383 // case, if the sync time is less than PrintSafepointStatisticsTimeout,
1384 // don't print it out.
1385 // Approximate the vm op time.
1386 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
1387 os::javaTimeNanos() - cleanup_end_time;
1388
1389 if ( PrintSafepointStatisticsTimeout < 0 ||
1390 spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
1391 print_statistics();
1392 }
1393 tty->cr();
1394
1395 // Print out polling page sampling status.
1396 if (!need_to_track_page_armed_status) {
1397 tty->print_cr("Polling page always armed");
1398 } else {
1399 tty->print_cr("Defer polling page loop count = " INTX_FORMAT "\n",
1400 DeferPollingPageLoopCount);
1401 }
1402
1403 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1404 if (_safepoint_reasons[index] != 0) {
1405 tty->print_cr("%-26s" UINT64_FORMAT_W(10), VM_Operation::name(index),
1406 _safepoint_reasons[index]);
1407 }
1408 }
1409
1410 tty->print_cr(UINT64_FORMAT_W(5) " VM operations coalesced during safepoint",
1411 _coalesced_vmop_count);
1412 tty->print_cr("Maximum sync time " INT64_FORMAT_W(5) " ms",
1413 (int64_t)(_max_sync_time / MICROUNITS));
1414 tty->print_cr("Maximum vm operation time (except for Exit VM operation) "
1415 INT64_FORMAT_W(5) " ms",
1416 (int64_t)(_max_vmop_time / MICROUNITS));
1417 }
1418
1419 // ------------------------------------------------------------------------------------------------
1420 // Non-product code
1421
1422 #ifndef PRODUCT
1423
1424 void SafepointSynchronize::print_state() {
1425 if (_state == _not_synchronized) {
1426 tty->print_cr("not synchronized");
1427 } else if (_state == _synchronizing || _state == _synchronized) {
1428 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
1429 "synchronized");
1430
1431 for (JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
1432 cur->safepoint_state()->print();
1433 }
1434 }
1435 }
1436
1437 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
1438 if (ShowSafepointMsgs) {
1439 va_list ap;
1440 va_start(ap, format);
1441 tty->vprint_cr(format, ap);
1442 va_end(ap);
1443 }
1444 }
1445
1446 #endif // !PRODUCT