safepoint.cpp revision 1472:c18cbe5936b8
1/* 2 * Copyright (c) 1997, 2009, 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 "incls/_precompiled.incl" 26# include "incls/_safepoint.cpp.incl" 27 28// -------------------------------------------------------------------------------------------------- 29// Implementation of Safepoint begin/end 30 31SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized; 32volatile int SafepointSynchronize::_waiting_to_block = 0; 33volatile int SafepointSynchronize::_safepoint_counter = 0; 34long SafepointSynchronize::_end_of_last_safepoint = 0; 35static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE 36static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only 37static bool timeout_error_printed = false; 38 39// Roll all threads forward to a safepoint and suspend them all 40void SafepointSynchronize::begin() { 41 42 Thread* myThread = Thread::current(); 43 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint"); 44 45 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) { 46 _safepoint_begin_time = os::javaTimeNanos(); 47 _ts_of_current_safepoint = tty->time_stamp().seconds(); 48 } 49 50#ifndef SERIALGC 51 if (UseConcMarkSweepGC) { 52 // In the future we should investigate whether CMS can use the 53 // more-general mechanism below. DLD (01/05). 54 ConcurrentMarkSweepThread::synchronize(false); 55 } else if (UseG1GC) { 56 ConcurrentGCThread::safepoint_synchronize(); 57 } 58#endif // SERIALGC 59 60 // By getting the Threads_lock, we assure that no threads are about to start or 61 // exit. It is released again in SafepointSynchronize::end(). 62 Threads_lock->lock(); 63 64 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state"); 65 66 int nof_threads = Threads::number_of_threads(); 67 68 if (TraceSafepoint) { 69 tty->print_cr("Safepoint synchronization initiated. (%d)", nof_threads); 70 } 71 72 RuntimeService::record_safepoint_begin(); 73 74 { 75 MutexLocker mu(Safepoint_lock); 76 77 // Set number of threads to wait for, before we initiate the callbacks 78 _waiting_to_block = nof_threads; 79 TryingToBlock = 0 ; 80 int still_running = nof_threads; 81 82 // Save the starting time, so that it can be compared to see if this has taken 83 // too long to complete. 84 jlong safepoint_limit_time; 85 timeout_error_printed = false; 86 87 // PrintSafepointStatisticsTimeout can be specified separately. When 88 // specified, PrintSafepointStatistics will be set to true in 89 // deferred_initialize_stat method. The initialization has to be done 90 // early enough to avoid any races. See bug 6880029 for details. 91 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) { 92 deferred_initialize_stat(); 93 } 94 95 // Begin the process of bringing the system to a safepoint. 96 // Java threads can be in several different states and are 97 // stopped by different mechanisms: 98 // 99 // 1. Running interpreted 100 // The interpeter dispatch table is changed to force it to 101 // check for a safepoint condition between bytecodes. 102 // 2. Running in native code 103 // When returning from the native code, a Java thread must check 104 // the safepoint _state to see if we must block. If the 105 // VM thread sees a Java thread in native, it does 106 // not wait for this thread to block. The order of the memory 107 // writes and reads of both the safepoint state and the Java 108 // threads state is critical. In order to guarantee that the 109 // memory writes are serialized with respect to each other, 110 // the VM thread issues a memory barrier instruction 111 // (on MP systems). In order to avoid the overhead of issuing 112 // a memory barrier for each Java thread making native calls, each Java 113 // thread performs a write to a single memory page after changing 114 // the thread state. The VM thread performs a sequence of 115 // mprotect OS calls which forces all previous writes from all 116 // Java threads to be serialized. This is done in the 117 // os::serialize_thread_states() call. This has proven to be 118 // much more efficient than executing a membar instruction 119 // on every call to native code. 120 // 3. Running compiled Code 121 // Compiled code reads a global (Safepoint Polling) page that 122 // is set to fault if we are trying to get to a safepoint. 123 // 4. Blocked 124 // A thread which is blocked will not be allowed to return from the 125 // block condition until the safepoint operation is complete. 126 // 5. In VM or Transitioning between states 127 // If a Java thread is currently running in the VM or transitioning 128 // between states, the safepointing code will wait for the thread to 129 // block itself when it attempts transitions to a new state. 130 // 131 _state = _synchronizing; 132 OrderAccess::fence(); 133 134 // Flush all thread states to memory 135 if (!UseMembar) { 136 os::serialize_thread_states(); 137 } 138 139 // Make interpreter safepoint aware 140 Interpreter::notice_safepoints(); 141 142 if (UseCompilerSafepoints && DeferPollingPageLoopCount < 0) { 143 // Make polling safepoint aware 144 guarantee (PageArmed == 0, "invariant") ; 145 PageArmed = 1 ; 146 os::make_polling_page_unreadable(); 147 } 148 149 // Consider using active_processor_count() ... but that call is expensive. 150 int ncpus = os::processor_count() ; 151 152#ifdef ASSERT 153 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) { 154 assert(cur->safepoint_state()->is_running(), "Illegal initial state"); 155 } 156#endif // ASSERT 157 158 if (SafepointTimeout) 159 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS; 160 161 // Iterate through all threads until it have been determined how to stop them all at a safepoint 162 unsigned int iterations = 0; 163 int steps = 0 ; 164 while(still_running > 0) { 165 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) { 166 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended"); 167 ThreadSafepointState *cur_state = cur->safepoint_state(); 168 if (cur_state->is_running()) { 169 cur_state->examine_state_of_thread(); 170 if (!cur_state->is_running()) { 171 still_running--; 172 // consider adjusting steps downward: 173 // steps = 0 174 // steps -= NNN 175 // steps >>= 1 176 // steps = MIN(steps, 2000-100) 177 // if (iterations != 0) steps -= NNN 178 } 179 if (TraceSafepoint && Verbose) cur_state->print(); 180 } 181 } 182 183 if (PrintSafepointStatistics && iterations == 0) { 184 begin_statistics(nof_threads, still_running); 185 } 186 187 if (still_running > 0) { 188 // Check for if it takes to long 189 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) { 190 print_safepoint_timeout(_spinning_timeout); 191 } 192 193 // Spin to avoid context switching. 194 // There's a tension between allowing the mutators to run (and rendezvous) 195 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that 196 // a mutator might otherwise use profitably to reach a safepoint. Excessive 197 // spinning by the VM thread on a saturated system can increase rendezvous latency. 198 // Blocking or yielding incur their own penalties in the form of context switching 199 // and the resultant loss of $ residency. 200 // 201 // Further complicating matters is that yield() does not work as naively expected 202 // on many platforms -- yield() does not guarantee that any other ready threads 203 // will run. As such we revert yield_all() after some number of iterations. 204 // Yield_all() is implemented as a short unconditional sleep on some platforms. 205 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping 206 // can actually increase the time it takes the VM thread to detect that a system-wide 207 // stop-the-world safepoint has been reached. In a pathological scenario such as that 208 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe. 209 // In that case the mutators will be stalled waiting for the safepoint to complete and the 210 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread 211 // will eventually wake up and detect that all mutators are safe, at which point 212 // we'll again make progress. 213 // 214 // Beware too that that the VMThread typically runs at elevated priority. 215 // Its default priority is higher than the default mutator priority. 216 // Obviously, this complicates spinning. 217 // 218 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0). 219 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will. 220 // 221 // See the comments in synchronizer.cpp for additional remarks on spinning. 222 // 223 // In the future we might: 224 // 1. Modify the safepoint scheme to avoid potentally unbounded spinning. 225 // This is tricky as the path used by a thread exiting the JVM (say on 226 // on JNI call-out) simply stores into its state field. The burden 227 // is placed on the VM thread, which must poll (spin). 228 // 2. Find something useful to do while spinning. If the safepoint is GC-related 229 // we might aggressively scan the stacks of threads that are already safe. 230 // 3. Use Solaris schedctl to examine the state of the still-running mutators. 231 // If all the mutators are ONPROC there's no reason to sleep or yield. 232 // 4. YieldTo() any still-running mutators that are ready but OFFPROC. 233 // 5. Check system saturation. If the system is not fully saturated then 234 // simply spin and avoid sleep/yield. 235 // 6. As still-running mutators rendezvous they could unpark the sleeping 236 // VMthread. This works well for still-running mutators that become 237 // safe. The VMthread must still poll for mutators that call-out. 238 // 7. Drive the policy on time-since-begin instead of iterations. 239 // 8. Consider making the spin duration a function of the # of CPUs: 240 // Spin = (((ncpus-1) * M) + K) + F(still_running) 241 // Alternately, instead of counting iterations of the outer loop 242 // we could count the # of threads visited in the inner loop, above. 243 // 9. On windows consider using the return value from SwitchThreadTo() 244 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions. 245 246 if (UseCompilerSafepoints && int(iterations) == DeferPollingPageLoopCount) { 247 guarantee (PageArmed == 0, "invariant") ; 248 PageArmed = 1 ; 249 os::make_polling_page_unreadable(); 250 } 251 252 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or 253 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus) 254 ++steps ; 255 if (ncpus > 1 && steps < SafepointSpinBeforeYield) { 256 SpinPause() ; // MP-Polite spin 257 } else 258 if (steps < DeferThrSuspendLoopCount) { 259 os::NakedYield() ; 260 } else { 261 os::yield_all(steps) ; 262 // Alternately, the VM thread could transiently depress its scheduling priority or 263 // transiently increase the priority of the tardy mutator(s). 264 } 265 266 iterations ++ ; 267 } 268 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long"); 269 } 270 assert(still_running == 0, "sanity check"); 271 272 if (PrintSafepointStatistics) { 273 update_statistics_on_spin_end(); 274 } 275 276 // wait until all threads are stopped 277 while (_waiting_to_block > 0) { 278 if (TraceSafepoint) tty->print_cr("Waiting for %d thread(s) to block", _waiting_to_block); 279 if (!SafepointTimeout || timeout_error_printed) { 280 Safepoint_lock->wait(true); // true, means with no safepoint checks 281 } else { 282 // Compute remaining time 283 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos(); 284 285 // If there is no remaining time, then there is an error 286 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) { 287 print_safepoint_timeout(_blocking_timeout); 288 } 289 } 290 } 291 assert(_waiting_to_block == 0, "sanity check"); 292 293#ifndef PRODUCT 294 if (SafepointTimeout) { 295 jlong current_time = os::javaTimeNanos(); 296 if (safepoint_limit_time < current_time) { 297 tty->print_cr("# SafepointSynchronize: Finished after " 298 INT64_FORMAT_W(6) " ms", 299 ((current_time - safepoint_limit_time) / MICROUNITS + 300 SafepointTimeoutDelay)); 301 } 302 } 303#endif 304 305 assert((_safepoint_counter & 0x1) == 0, "must be even"); 306 assert(Threads_lock->owned_by_self(), "must hold Threads_lock"); 307 _safepoint_counter ++; 308 309 // Record state 310 _state = _synchronized; 311 312 OrderAccess::fence(); 313 314 if (TraceSafepoint) { 315 VM_Operation *op = VMThread::vm_operation(); 316 tty->print_cr("Entering safepoint region: %s", (op != NULL) ? op->name() : "no vm operation"); 317 } 318 319 RuntimeService::record_safepoint_synchronized(); 320 if (PrintSafepointStatistics) { 321 update_statistics_on_sync_end(os::javaTimeNanos()); 322 } 323 324 // Call stuff that needs to be run when a safepoint is just about to be completed 325 do_cleanup_tasks(); 326 327 if (PrintSafepointStatistics) { 328 // Record how much time spend on the above cleanup tasks 329 update_statistics_on_cleanup_end(os::javaTimeNanos()); 330 } 331 } 332} 333 334// Wake up all threads, so they are ready to resume execution after the safepoint 335// operation has been carried out 336void SafepointSynchronize::end() { 337 338 assert(Threads_lock->owned_by_self(), "must hold Threads_lock"); 339 assert((_safepoint_counter & 0x1) == 1, "must be odd"); 340 _safepoint_counter ++; 341 // memory fence isn't required here since an odd _safepoint_counter 342 // value can do no harm and a fence is issued below anyway. 343 344 DEBUG_ONLY(Thread* myThread = Thread::current();) 345 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint"); 346 347 if (PrintSafepointStatistics) { 348 end_statistics(os::javaTimeNanos()); 349 } 350 351#ifdef ASSERT 352 // A pending_exception cannot be installed during a safepoint. The threads 353 // may install an async exception after they come back from a safepoint into 354 // pending_exception after they unblock. But that should happen later. 355 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) { 356 assert (!(cur->has_pending_exception() && 357 cur->safepoint_state()->is_at_poll_safepoint()), 358 "safepoint installed a pending exception"); 359 } 360#endif // ASSERT 361 362 if (PageArmed) { 363 // Make polling safepoint aware 364 os::make_polling_page_readable(); 365 PageArmed = 0 ; 366 } 367 368 // Remove safepoint check from interpreter 369 Interpreter::ignore_safepoints(); 370 371 { 372 MutexLocker mu(Safepoint_lock); 373 374 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization"); 375 376 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method 377 // when they get restarted. 378 _state = _not_synchronized; 379 OrderAccess::fence(); 380 381 if (TraceSafepoint) { 382 tty->print_cr("Leaving safepoint region"); 383 } 384 385 // Start suspended threads 386 for(JavaThread *current = Threads::first(); current; current = current->next()) { 387 // A problem occurring on Solaris is when attempting to restart threads 388 // the first #cpus - 1 go well, but then the VMThread is preempted when we get 389 // to the next one (since it has been running the longest). We then have 390 // to wait for a cpu to become available before we can continue restarting 391 // threads. 392 // FIXME: This causes the performance of the VM to degrade when active and with 393 // large numbers of threads. Apparently this is due to the synchronous nature 394 // of suspending threads. 395 // 396 // TODO-FIXME: the comments above are vestigial and no longer apply. 397 // Furthermore, using solaris' schedctl in this particular context confers no benefit 398 if (VMThreadHintNoPreempt) { 399 os::hint_no_preempt(); 400 } 401 ThreadSafepointState* cur_state = current->safepoint_state(); 402 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint"); 403 cur_state->restart(); 404 assert(cur_state->is_running(), "safepoint state has not been reset"); 405 } 406 407 RuntimeService::record_safepoint_end(); 408 409 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads 410 // blocked in signal_thread_blocked 411 Threads_lock->unlock(); 412 413 } 414#ifndef SERIALGC 415 // If there are any concurrent GC threads resume them. 416 if (UseConcMarkSweepGC) { 417 ConcurrentMarkSweepThread::desynchronize(false); 418 } else if (UseG1GC) { 419 ConcurrentGCThread::safepoint_desynchronize(); 420 } 421#endif // SERIALGC 422 // record this time so VMThread can keep track how much time has elasped 423 // since last safepoint. 424 _end_of_last_safepoint = os::javaTimeMillis(); 425} 426 427bool SafepointSynchronize::is_cleanup_needed() { 428 // Need a safepoint if some inline cache buffers is non-empty 429 if (!InlineCacheBuffer::is_empty()) return true; 430 return false; 431} 432 433jlong CounterDecay::_last_timestamp = 0; 434 435static void do_method(methodOop m) { 436 m->invocation_counter()->decay(); 437} 438 439void CounterDecay::decay() { 440 _last_timestamp = os::javaTimeMillis(); 441 442 // This operation is going to be performed only at the end of a safepoint 443 // and hence GC's will not be going on, all Java mutators are suspended 444 // at this point and hence SystemDictionary_lock is also not needed. 445 assert(SafepointSynchronize::is_at_safepoint(), "can only be executed at a safepoint"); 446 int nclasses = SystemDictionary::number_of_classes(); 447 double classes_per_tick = nclasses * (CounterDecayMinIntervalLength * 1e-3 / 448 CounterHalfLifeTime); 449 for (int i = 0; i < classes_per_tick; i++) { 450 klassOop k = SystemDictionary::try_get_next_class(); 451 if (k != NULL && k->klass_part()->oop_is_instance()) { 452 instanceKlass::cast(k)->methods_do(do_method); 453 } 454 } 455} 456 457// Various cleaning tasks that should be done periodically at safepoints 458void SafepointSynchronize::do_cleanup_tasks() { 459 { 460 TraceTime t1("deflating idle monitors", TraceSafepointCleanupTime); 461 ObjectSynchronizer::deflate_idle_monitors(); 462 } 463 464 { 465 TraceTime t2("updating inline caches", TraceSafepointCleanupTime); 466 InlineCacheBuffer::update_inline_caches(); 467 } 468 469 if(UseCounterDecay && CounterDecay::is_decay_needed()) { 470 TraceTime t3("decaying counter", TraceSafepointCleanupTime); 471 CounterDecay::decay(); 472 } 473 474 TraceTime t4("sweeping nmethods", TraceSafepointCleanupTime); 475 NMethodSweeper::scan_stacks(); 476} 477 478 479bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) { 480 switch(state) { 481 case _thread_in_native: 482 // native threads are safe if they have no java stack or have walkable stack 483 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable(); 484 485 // blocked threads should have already have walkable stack 486 case _thread_blocked: 487 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable"); 488 return true; 489 490 default: 491 return false; 492 } 493} 494 495 496// ------------------------------------------------------------------------------------------------------- 497// Implementation of Safepoint callback point 498 499void SafepointSynchronize::block(JavaThread *thread) { 500 assert(thread != NULL, "thread must be set"); 501 assert(thread->is_Java_thread(), "not a Java thread"); 502 503 // Threads shouldn't block if they are in the middle of printing, but... 504 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id()); 505 506 // Only bail from the block() call if the thread is gone from the 507 // thread list; starting to exit should still block. 508 if (thread->is_terminated()) { 509 // block current thread if we come here from native code when VM is gone 510 thread->block_if_vm_exited(); 511 512 // otherwise do nothing 513 return; 514 } 515 516 JavaThreadState state = thread->thread_state(); 517 thread->frame_anchor()->make_walkable(thread); 518 519 // Check that we have a valid thread_state at this point 520 switch(state) { 521 case _thread_in_vm_trans: 522 case _thread_in_Java: // From compiled code 523 524 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case, 525 // we pretend we are still in the VM. 526 thread->set_thread_state(_thread_in_vm); 527 528 if (is_synchronizing()) { 529 Atomic::inc (&TryingToBlock) ; 530 } 531 532 // We will always be holding the Safepoint_lock when we are examine the state 533 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and 534 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code 535 Safepoint_lock->lock_without_safepoint_check(); 536 if (is_synchronizing()) { 537 // Decrement the number of threads to wait for and signal vm thread 538 assert(_waiting_to_block > 0, "sanity check"); 539 _waiting_to_block--; 540 thread->safepoint_state()->set_has_called_back(true); 541 542 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread 543 if (_waiting_to_block == 0) { 544 Safepoint_lock->notify_all(); 545 } 546 } 547 548 // We transition the thread to state _thread_blocked here, but 549 // we can't do our usual check for external suspension and then 550 // self-suspend after the lock_without_safepoint_check() call 551 // below because we are often called during transitions while 552 // we hold different locks. That would leave us suspended while 553 // holding a resource which results in deadlocks. 554 thread->set_thread_state(_thread_blocked); 555 Safepoint_lock->unlock(); 556 557 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during 558 // the entire safepoint, the threads will all line up here during the safepoint. 559 Threads_lock->lock_without_safepoint_check(); 560 // restore original state. This is important if the thread comes from compiled code, so it 561 // will continue to execute with the _thread_in_Java state. 562 thread->set_thread_state(state); 563 Threads_lock->unlock(); 564 break; 565 566 case _thread_in_native_trans: 567 case _thread_blocked_trans: 568 case _thread_new_trans: 569 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) { 570 thread->print_thread_state(); 571 fatal("Deadlock in safepoint code. " 572 "Should have called back to the VM before blocking."); 573 } 574 575 // We transition the thread to state _thread_blocked here, but 576 // we can't do our usual check for external suspension and then 577 // self-suspend after the lock_without_safepoint_check() call 578 // below because we are often called during transitions while 579 // we hold different locks. That would leave us suspended while 580 // holding a resource which results in deadlocks. 581 thread->set_thread_state(_thread_blocked); 582 583 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence, 584 // the safepoint code might still be waiting for it to block. We need to change the state here, 585 // so it can see that it is at a safepoint. 586 587 // Block until the safepoint operation is completed. 588 Threads_lock->lock_without_safepoint_check(); 589 590 // Restore state 591 thread->set_thread_state(state); 592 593 Threads_lock->unlock(); 594 break; 595 596 default: 597 fatal(err_msg("Illegal threadstate encountered: %d", state)); 598 } 599 600 // Check for pending. async. exceptions or suspends - except if the 601 // thread was blocked inside the VM. has_special_runtime_exit_condition() 602 // is called last since it grabs a lock and we only want to do that when 603 // we must. 604 // 605 // Note: we never deliver an async exception at a polling point as the 606 // compiler may not have an exception handler for it. The polling 607 // code will notice the async and deoptimize and the exception will 608 // be delivered. (Polling at a return point is ok though). Sure is 609 // a lot of bother for a deprecated feature... 610 // 611 // We don't deliver an async exception if the thread state is 612 // _thread_in_native_trans so JNI functions won't be called with 613 // a surprising pending exception. If the thread state is going back to java, 614 // async exception is checked in check_special_condition_for_native_trans(). 615 616 if (state != _thread_blocked_trans && 617 state != _thread_in_vm_trans && 618 thread->has_special_runtime_exit_condition()) { 619 thread->handle_special_runtime_exit_condition( 620 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans)); 621 } 622} 623 624// ------------------------------------------------------------------------------------------------------ 625// Exception handlers 626 627#ifndef PRODUCT 628#ifdef _LP64 629#define PTR_PAD "" 630#else 631#define PTR_PAD " " 632#endif 633 634static void print_ptrs(intptr_t oldptr, intptr_t newptr, bool wasoop) { 635 bool is_oop = newptr ? ((oop)newptr)->is_oop() : false; 636 tty->print_cr(PTR_FORMAT PTR_PAD " %s %c " PTR_FORMAT PTR_PAD " %s %s", 637 oldptr, wasoop?"oop":" ", oldptr == newptr ? ' ' : '!', 638 newptr, is_oop?"oop":" ", (wasoop && !is_oop) ? "STALE" : ((wasoop==false&&is_oop==false&&oldptr !=newptr)?"STOMP":" ")); 639} 640 641static void print_longs(jlong oldptr, jlong newptr, bool wasoop) { 642 bool is_oop = newptr ? ((oop)(intptr_t)newptr)->is_oop() : false; 643 tty->print_cr(PTR64_FORMAT " %s %c " PTR64_FORMAT " %s %s", 644 oldptr, wasoop?"oop":" ", oldptr == newptr ? ' ' : '!', 645 newptr, is_oop?"oop":" ", (wasoop && !is_oop) ? "STALE" : ((wasoop==false&&is_oop==false&&oldptr !=newptr)?"STOMP":" ")); 646} 647 648#ifdef SPARC 649static void print_me(intptr_t *new_sp, intptr_t *old_sp, bool *was_oops) { 650#ifdef _LP64 651 tty->print_cr("--------+------address-----+------before-----------+-------after----------+"); 652 const int incr = 1; // Increment to skip a long, in units of intptr_t 653#else 654 tty->print_cr("--------+--address-+------before-----------+-------after----------+"); 655 const int incr = 2; // Increment to skip a long, in units of intptr_t 656#endif 657 tty->print_cr("---SP---|"); 658 for( int i=0; i<16; i++ ) { 659 tty->print("blob %c%d |"PTR_FORMAT" ","LO"[i>>3],i&7,new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); } 660 tty->print_cr("--------|"); 661 for( int i1=0; i1<frame::memory_parameter_word_sp_offset-16; i1++ ) { 662 tty->print("argv pad|"PTR_FORMAT" ",new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); } 663 tty->print(" pad|"PTR_FORMAT" ",new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); 664 tty->print_cr("--------|"); 665 tty->print(" G1 |"PTR_FORMAT" ",new_sp); print_longs(*(jlong*)old_sp,*(jlong*)new_sp,was_oops[incr-1]); old_sp += incr; new_sp += incr; was_oops += incr; 666 tty->print(" G3 |"PTR_FORMAT" ",new_sp); print_longs(*(jlong*)old_sp,*(jlong*)new_sp,was_oops[incr-1]); old_sp += incr; new_sp += incr; was_oops += incr; 667 tty->print(" G4 |"PTR_FORMAT" ",new_sp); print_longs(*(jlong*)old_sp,*(jlong*)new_sp,was_oops[incr-1]); old_sp += incr; new_sp += incr; was_oops += incr; 668 tty->print(" G5 |"PTR_FORMAT" ",new_sp); print_longs(*(jlong*)old_sp,*(jlong*)new_sp,was_oops[incr-1]); old_sp += incr; new_sp += incr; was_oops += incr; 669 tty->print_cr(" FSR |"PTR_FORMAT" "PTR64_FORMAT" "PTR64_FORMAT,new_sp,*(jlong*)old_sp,*(jlong*)new_sp); 670 old_sp += incr; new_sp += incr; was_oops += incr; 671 // Skip the floats 672 tty->print_cr("--Float-|"PTR_FORMAT,new_sp); 673 tty->print_cr("---FP---|"); 674 old_sp += incr*32; new_sp += incr*32; was_oops += incr*32; 675 for( int i2=0; i2<16; i2++ ) { 676 tty->print("call %c%d |"PTR_FORMAT" ","LI"[i2>>3],i2&7,new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); } 677 tty->print_cr(""); 678} 679#endif // SPARC 680#endif // PRODUCT 681 682 683void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) { 684 assert(thread->is_Java_thread(), "polling reference encountered by VM thread"); 685 assert(thread->thread_state() == _thread_in_Java, "should come from Java code"); 686 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization"); 687 688 // Uncomment this to get some serious before/after printing of the 689 // Sparc safepoint-blob frame structure. 690 /* 691 intptr_t* sp = thread->last_Java_sp(); 692 intptr_t stack_copy[150]; 693 for( int i=0; i<150; i++ ) stack_copy[i] = sp[i]; 694 bool was_oops[150]; 695 for( int i=0; i<150; i++ ) 696 was_oops[i] = stack_copy[i] ? ((oop)stack_copy[i])->is_oop() : false; 697 */ 698 699 if (ShowSafepointMsgs) { 700 tty->print("handle_polling_page_exception: "); 701 } 702 703 if (PrintSafepointStatistics) { 704 inc_page_trap_count(); 705 } 706 707 ThreadSafepointState* state = thread->safepoint_state(); 708 709 state->handle_polling_page_exception(); 710 // print_me(sp,stack_copy,was_oops); 711} 712 713 714void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) { 715 if (!timeout_error_printed) { 716 timeout_error_printed = true; 717 // Print out the thread infor which didn't reach the safepoint for debugging 718 // purposes (useful when there are lots of threads in the debugger). 719 tty->print_cr(""); 720 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:"); 721 if (reason == _spinning_timeout) { 722 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint."); 723 } else if (reason == _blocking_timeout) { 724 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop."); 725 } 726 727 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:"); 728 ThreadSafepointState *cur_state; 729 ResourceMark rm; 730 for(JavaThread *cur_thread = Threads::first(); cur_thread; 731 cur_thread = cur_thread->next()) { 732 cur_state = cur_thread->safepoint_state(); 733 734 if (cur_thread->thread_state() != _thread_blocked && 735 ((reason == _spinning_timeout && cur_state->is_running()) || 736 (reason == _blocking_timeout && !cur_state->has_called_back()))) { 737 tty->print("# "); 738 cur_thread->print(); 739 tty->print_cr(""); 740 } 741 } 742 tty->print_cr("# SafepointSynchronize::begin: (End of list)"); 743 } 744 745 // To debug the long safepoint, specify both DieOnSafepointTimeout & 746 // ShowMessageBoxOnError. 747 if (DieOnSafepointTimeout) { 748 char msg[1024]; 749 VM_Operation *op = VMThread::vm_operation(); 750 sprintf(msg, "Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.", 751 SafepointTimeoutDelay, 752 op != NULL ? op->name() : "no vm operation"); 753 fatal(msg); 754 } 755} 756 757 758// ------------------------------------------------------------------------------------------------------- 759// Implementation of ThreadSafepointState 760 761ThreadSafepointState::ThreadSafepointState(JavaThread *thread) { 762 _thread = thread; 763 _type = _running; 764 _has_called_back = false; 765 _at_poll_safepoint = false; 766} 767 768void ThreadSafepointState::create(JavaThread *thread) { 769 ThreadSafepointState *state = new ThreadSafepointState(thread); 770 thread->set_safepoint_state(state); 771} 772 773void ThreadSafepointState::destroy(JavaThread *thread) { 774 if (thread->safepoint_state()) { 775 delete(thread->safepoint_state()); 776 thread->set_safepoint_state(NULL); 777 } 778} 779 780void ThreadSafepointState::examine_state_of_thread() { 781 assert(is_running(), "better be running or just have hit safepoint poll"); 782 783 JavaThreadState state = _thread->thread_state(); 784 785 // Check for a thread that is suspended. Note that thread resume tries 786 // to grab the Threads_lock which we own here, so a thread cannot be 787 // resumed during safepoint synchronization. 788 789 // We check to see if this thread is suspended without locking to 790 // avoid deadlocking with a third thread that is waiting for this 791 // thread to be suspended. The third thread can notice the safepoint 792 // that we're trying to start at the beginning of its SR_lock->wait() 793 // call. If that happens, then the third thread will block on the 794 // safepoint while still holding the underlying SR_lock. We won't be 795 // able to get the SR_lock and we'll deadlock. 796 // 797 // We don't need to grab the SR_lock here for two reasons: 798 // 1) The suspend flags are both volatile and are set with an 799 // Atomic::cmpxchg() call so we should see the suspended 800 // state right away. 801 // 2) We're being called from the safepoint polling loop; if 802 // we don't see the suspended state on this iteration, then 803 // we'll come around again. 804 // 805 bool is_suspended = _thread->is_ext_suspended(); 806 if (is_suspended) { 807 roll_forward(_at_safepoint); 808 return; 809 } 810 811 // Some JavaThread states have an initial safepoint state of 812 // running, but are actually at a safepoint. We will happily 813 // agree and update the safepoint state here. 814 if (SafepointSynchronize::safepoint_safe(_thread, state)) { 815 roll_forward(_at_safepoint); 816 return; 817 } 818 819 if (state == _thread_in_vm) { 820 roll_forward(_call_back); 821 return; 822 } 823 824 // All other thread states will continue to run until they 825 // transition and self-block in state _blocked 826 // Safepoint polling in compiled code causes the Java threads to do the same. 827 // Note: new threads may require a malloc so they must be allowed to finish 828 829 assert(is_running(), "examine_state_of_thread on non-running thread"); 830 return; 831} 832 833// Returns true is thread could not be rolled forward at present position. 834void ThreadSafepointState::roll_forward(suspend_type type) { 835 _type = type; 836 837 switch(_type) { 838 case _at_safepoint: 839 SafepointSynchronize::signal_thread_at_safepoint(); 840 break; 841 842 case _call_back: 843 set_has_called_back(false); 844 break; 845 846 case _running: 847 default: 848 ShouldNotReachHere(); 849 } 850} 851 852void ThreadSafepointState::restart() { 853 switch(type()) { 854 case _at_safepoint: 855 case _call_back: 856 break; 857 858 case _running: 859 default: 860 tty->print_cr("restart thread "INTPTR_FORMAT" with state %d", 861 _thread, _type); 862 _thread->print(); 863 ShouldNotReachHere(); 864 } 865 _type = _running; 866 set_has_called_back(false); 867} 868 869 870void ThreadSafepointState::print_on(outputStream *st) const { 871 const char *s; 872 873 switch(_type) { 874 case _running : s = "_running"; break; 875 case _at_safepoint : s = "_at_safepoint"; break; 876 case _call_back : s = "_call_back"; break; 877 default: 878 ShouldNotReachHere(); 879 } 880 881 st->print_cr("Thread: " INTPTR_FORMAT 882 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d", 883 _thread, _thread->osthread()->thread_id(), s, _has_called_back, 884 _at_poll_safepoint); 885 886 _thread->print_thread_state_on(st); 887} 888 889 890// --------------------------------------------------------------------------------------------------------------------- 891 892// Block the thread at the safepoint poll or poll return. 893void ThreadSafepointState::handle_polling_page_exception() { 894 895 // Check state. block() will set thread state to thread_in_vm which will 896 // cause the safepoint state _type to become _call_back. 897 assert(type() == ThreadSafepointState::_running, 898 "polling page exception on thread not running state"); 899 900 // Step 1: Find the nmethod from the return address 901 if (ShowSafepointMsgs && Verbose) { 902 tty->print_cr("Polling page exception at " INTPTR_FORMAT, thread()->saved_exception_pc()); 903 } 904 address real_return_addr = thread()->saved_exception_pc(); 905 906 CodeBlob *cb = CodeCache::find_blob(real_return_addr); 907 assert(cb != NULL && cb->is_nmethod(), "return address should be in nmethod"); 908 nmethod* nm = (nmethod*)cb; 909 910 // Find frame of caller 911 frame stub_fr = thread()->last_frame(); 912 CodeBlob* stub_cb = stub_fr.cb(); 913 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub"); 914 RegisterMap map(thread(), true); 915 frame caller_fr = stub_fr.sender(&map); 916 917 // Should only be poll_return or poll 918 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" ); 919 920 // This is a poll immediately before a return. The exception handling code 921 // has already had the effect of causing the return to occur, so the execution 922 // will continue immediately after the call. In addition, the oopmap at the 923 // return point does not mark the return value as an oop (if it is), so 924 // it needs a handle here to be updated. 925 if( nm->is_at_poll_return(real_return_addr) ) { 926 // See if return type is an oop. 927 bool return_oop = nm->method()->is_returning_oop(); 928 Handle return_value; 929 if (return_oop) { 930 // The oop result has been saved on the stack together with all 931 // the other registers. In order to preserve it over GCs we need 932 // to keep it in a handle. 933 oop result = caller_fr.saved_oop_result(&map); 934 assert(result == NULL || result->is_oop(), "must be oop"); 935 return_value = Handle(thread(), result); 936 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer"); 937 } 938 939 // Block the thread 940 SafepointSynchronize::block(thread()); 941 942 // restore oop result, if any 943 if (return_oop) { 944 caller_fr.set_saved_oop_result(&map, return_value()); 945 } 946 } 947 948 // This is a safepoint poll. Verify the return address and block. 949 else { 950 set_at_poll_safepoint(true); 951 952 // verify the blob built the "return address" correctly 953 assert(real_return_addr == caller_fr.pc(), "must match"); 954 955 // Block the thread 956 SafepointSynchronize::block(thread()); 957 set_at_poll_safepoint(false); 958 959 // If we have a pending async exception deoptimize the frame 960 // as otherwise we may never deliver it. 961 if (thread()->has_async_condition()) { 962 ThreadInVMfromJavaNoAsyncException __tiv(thread()); 963 VM_DeoptimizeFrame deopt(thread(), caller_fr.id()); 964 VMThread::execute(&deopt); 965 } 966 967 // If an exception has been installed we must check for a pending deoptimization 968 // Deoptimize frame if exception has been thrown. 969 970 if (thread()->has_pending_exception() ) { 971 RegisterMap map(thread(), true); 972 frame caller_fr = stub_fr.sender(&map); 973 if (caller_fr.is_deoptimized_frame()) { 974 // The exception patch will destroy registers that are still 975 // live and will be needed during deoptimization. Defer the 976 // Async exception should have defered the exception until the 977 // next safepoint which will be detected when we get into 978 // the interpreter so if we have an exception now things 979 // are messed up. 980 981 fatal("Exception installed and deoptimization is pending"); 982 } 983 } 984 } 985} 986 987 988// 989// Statistics & Instrumentations 990// 991SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL; 992jlong SafepointSynchronize::_safepoint_begin_time = 0; 993int SafepointSynchronize::_cur_stat_index = 0; 994julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating]; 995julong SafepointSynchronize::_coalesced_vmop_count = 0; 996jlong SafepointSynchronize::_max_sync_time = 0; 997jlong SafepointSynchronize::_max_vmop_time = 0; 998float SafepointSynchronize::_ts_of_current_safepoint = 0.0f; 999 1000static jlong cleanup_end_time = 0; 1001static bool need_to_track_page_armed_status = false; 1002static bool init_done = false; 1003 1004// Helper method to print the header. 1005static void print_header() { 1006 tty->print(" vmop " 1007 "[threads: total initially_running wait_to_block] "); 1008 tty->print("[time: spin block sync cleanup vmop] "); 1009 1010 // no page armed status printed out if it is always armed. 1011 if (need_to_track_page_armed_status) { 1012 tty->print("page_armed "); 1013 } 1014 1015 tty->print_cr("page_trap_count"); 1016} 1017 1018void SafepointSynchronize::deferred_initialize_stat() { 1019 if (init_done) return; 1020 1021 if (PrintSafepointStatisticsCount <= 0) { 1022 fatal("Wrong PrintSafepointStatisticsCount"); 1023 } 1024 1025 // If PrintSafepointStatisticsTimeout is specified, the statistics data will 1026 // be printed right away, in which case, _safepoint_stats will regress to 1027 // a single element array. Otherwise, it is a circular ring buffer with default 1028 // size of PrintSafepointStatisticsCount. 1029 int stats_array_size; 1030 if (PrintSafepointStatisticsTimeout > 0) { 1031 stats_array_size = 1; 1032 PrintSafepointStatistics = true; 1033 } else { 1034 stats_array_size = PrintSafepointStatisticsCount; 1035 } 1036 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size 1037 * sizeof(SafepointStats)); 1038 guarantee(_safepoint_stats != NULL, 1039 "not enough memory for safepoint instrumentation data"); 1040 1041 if (UseCompilerSafepoints && DeferPollingPageLoopCount >= 0) { 1042 need_to_track_page_armed_status = true; 1043 } 1044 init_done = true; 1045} 1046 1047void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) { 1048 assert(init_done, "safepoint statistics array hasn't been initialized"); 1049 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1050 1051 spstat->_time_stamp = _ts_of_current_safepoint; 1052 1053 VM_Operation *op = VMThread::vm_operation(); 1054 spstat->_vmop_type = (op != NULL ? op->type() : -1); 1055 if (op != NULL) { 1056 _safepoint_reasons[spstat->_vmop_type]++; 1057 } 1058 1059 spstat->_nof_total_threads = nof_threads; 1060 spstat->_nof_initial_running_threads = nof_running; 1061 spstat->_nof_threads_hit_page_trap = 0; 1062 1063 // Records the start time of spinning. The real time spent on spinning 1064 // will be adjusted when spin is done. Same trick is applied for time 1065 // spent on waiting for threads to block. 1066 if (nof_running != 0) { 1067 spstat->_time_to_spin = os::javaTimeNanos(); 1068 } else { 1069 spstat->_time_to_spin = 0; 1070 } 1071} 1072 1073void SafepointSynchronize::update_statistics_on_spin_end() { 1074 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1075 1076 jlong cur_time = os::javaTimeNanos(); 1077 1078 spstat->_nof_threads_wait_to_block = _waiting_to_block; 1079 if (spstat->_nof_initial_running_threads != 0) { 1080 spstat->_time_to_spin = cur_time - spstat->_time_to_spin; 1081 } 1082 1083 if (need_to_track_page_armed_status) { 1084 spstat->_page_armed = (PageArmed == 1); 1085 } 1086 1087 // Records the start time of waiting for to block. Updated when block is done. 1088 if (_waiting_to_block != 0) { 1089 spstat->_time_to_wait_to_block = cur_time; 1090 } else { 1091 spstat->_time_to_wait_to_block = 0; 1092 } 1093} 1094 1095void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) { 1096 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1097 1098 if (spstat->_nof_threads_wait_to_block != 0) { 1099 spstat->_time_to_wait_to_block = end_time - 1100 spstat->_time_to_wait_to_block; 1101 } 1102 1103 // Records the end time of sync which will be used to calculate the total 1104 // vm operation time. Again, the real time spending in syncing will be deducted 1105 // from the start of the sync time later when end_statistics is called. 1106 spstat->_time_to_sync = end_time - _safepoint_begin_time; 1107 if (spstat->_time_to_sync > _max_sync_time) { 1108 _max_sync_time = spstat->_time_to_sync; 1109 } 1110 1111 spstat->_time_to_do_cleanups = end_time; 1112} 1113 1114void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) { 1115 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1116 1117 // Record how long spent in cleanup tasks. 1118 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups; 1119 1120 cleanup_end_time = end_time; 1121} 1122 1123void SafepointSynchronize::end_statistics(jlong vmop_end_time) { 1124 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1125 1126 // Update the vm operation time. 1127 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time; 1128 if (spstat->_time_to_exec_vmop > _max_vmop_time) { 1129 _max_vmop_time = spstat->_time_to_exec_vmop; 1130 } 1131 // Only the sync time longer than the specified 1132 // PrintSafepointStatisticsTimeout will be printed out right away. 1133 // By default, it is -1 meaning all samples will be put into the list. 1134 if ( PrintSafepointStatisticsTimeout > 0) { 1135 if (spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) { 1136 print_statistics(); 1137 } 1138 } else { 1139 // The safepoint statistics will be printed out when the _safepoin_stats 1140 // array fills up. 1141 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) { 1142 print_statistics(); 1143 _cur_stat_index = 0; 1144 } else { 1145 _cur_stat_index++; 1146 } 1147 } 1148} 1149 1150void SafepointSynchronize::print_statistics() { 1151 SafepointStats* sstats = _safepoint_stats; 1152 1153 for (int index = 0; index <= _cur_stat_index; index++) { 1154 if (index % 30 == 0) { 1155 print_header(); 1156 } 1157 sstats = &_safepoint_stats[index]; 1158 tty->print("%.3f: ", sstats->_time_stamp); 1159 tty->print("%-26s [" 1160 INT32_FORMAT_W(8)INT32_FORMAT_W(11)INT32_FORMAT_W(15) 1161 " ] ", 1162 sstats->_vmop_type == -1 ? "no vm operation" : 1163 VM_Operation::name(sstats->_vmop_type), 1164 sstats->_nof_total_threads, 1165 sstats->_nof_initial_running_threads, 1166 sstats->_nof_threads_wait_to_block); 1167 // "/ MICROUNITS " is to convert the unit from nanos to millis. 1168 tty->print(" [" 1169 INT64_FORMAT_W(6)INT64_FORMAT_W(6) 1170 INT64_FORMAT_W(6)INT64_FORMAT_W(6) 1171 INT64_FORMAT_W(6)" ] ", 1172 sstats->_time_to_spin / MICROUNITS, 1173 sstats->_time_to_wait_to_block / MICROUNITS, 1174 sstats->_time_to_sync / MICROUNITS, 1175 sstats->_time_to_do_cleanups / MICROUNITS, 1176 sstats->_time_to_exec_vmop / MICROUNITS); 1177 1178 if (need_to_track_page_armed_status) { 1179 tty->print(INT32_FORMAT" ", sstats->_page_armed); 1180 } 1181 tty->print_cr(INT32_FORMAT" ", sstats->_nof_threads_hit_page_trap); 1182 } 1183} 1184 1185// This method will be called when VM exits. It will first call 1186// print_statistics to print out the rest of the sampling. Then 1187// it tries to summarize the sampling. 1188void SafepointSynchronize::print_stat_on_exit() { 1189 if (_safepoint_stats == NULL) return; 1190 1191 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1192 1193 // During VM exit, end_statistics may not get called and in that 1194 // case, if the sync time is less than PrintSafepointStatisticsTimeout, 1195 // don't print it out. 1196 // Approximate the vm op time. 1197 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop = 1198 os::javaTimeNanos() - cleanup_end_time; 1199 1200 if ( PrintSafepointStatisticsTimeout < 0 || 1201 spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) { 1202 print_statistics(); 1203 } 1204 tty->print_cr(""); 1205 1206 // Print out polling page sampling status. 1207 if (!need_to_track_page_armed_status) { 1208 if (UseCompilerSafepoints) { 1209 tty->print_cr("Polling page always armed"); 1210 } 1211 } else { 1212 tty->print_cr("Defer polling page loop count = %d\n", 1213 DeferPollingPageLoopCount); 1214 } 1215 1216 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) { 1217 if (_safepoint_reasons[index] != 0) { 1218 tty->print_cr("%-26s"UINT64_FORMAT_W(10), VM_Operation::name(index), 1219 _safepoint_reasons[index]); 1220 } 1221 } 1222 1223 tty->print_cr(UINT64_FORMAT_W(5)" VM operations coalesced during safepoint", 1224 _coalesced_vmop_count); 1225 tty->print_cr("Maximum sync time "INT64_FORMAT_W(5)" ms", 1226 _max_sync_time / MICROUNITS); 1227 tty->print_cr("Maximum vm operation time (except for Exit VM operation) " 1228 INT64_FORMAT_W(5)" ms", 1229 _max_vmop_time / MICROUNITS); 1230} 1231 1232// ------------------------------------------------------------------------------------------------ 1233// Non-product code 1234 1235#ifndef PRODUCT 1236 1237void SafepointSynchronize::print_state() { 1238 if (_state == _not_synchronized) { 1239 tty->print_cr("not synchronized"); 1240 } else if (_state == _synchronizing || _state == _synchronized) { 1241 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" : 1242 "synchronized"); 1243 1244 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) { 1245 cur->safepoint_state()->print(); 1246 } 1247 } 1248} 1249 1250void SafepointSynchronize::safepoint_msg(const char* format, ...) { 1251 if (ShowSafepointMsgs) { 1252 va_list ap; 1253 va_start(ap, format); 1254 tty->vprint_cr(format, ap); 1255 va_end(ap); 1256 } 1257} 1258 1259#endif // !PRODUCT 1260