1 /* 2 * Copyright (c) 1997, 2017, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #include "precompiled.hpp" 26 #include "classfile/stringTable.hpp" 27 #include "classfile/symbolTable.hpp" 28 #include "classfile/systemDictionary.hpp" 29 #include "code/codeCache.hpp" 30 #include "code/icBuffer.hpp" 31 #include "code/nmethod.hpp" 32 #include "code/pcDesc.hpp" 33 #include "code/scopeDesc.hpp" 34 #include "gc/shared/collectedHeap.hpp" 35 #include "gc/shared/gcLocker.inline.hpp" 36 #include "gc/shared/strongRootsScope.hpp" 37 #include "gc/shared/workgroup.hpp" 38 #include "interpreter/interpreter.hpp" 39 #include "logging/log.hpp" 40 #include "logging/logStream.hpp" 41 #include "memory/resourceArea.hpp" 42 #include "memory/universe.inline.hpp" 43 #include "oops/oop.inline.hpp" 44 #include "oops/symbol.hpp" 45 #include "runtime/atomic.hpp" 46 #include "runtime/compilationPolicy.hpp" 47 #include "runtime/deoptimization.hpp" 48 #include "runtime/frame.inline.hpp" 49 #include "runtime/interfaceSupport.hpp" 50 #include "runtime/mutexLocker.hpp" 51 #include "runtime/orderAccess.inline.hpp" 52 #include "runtime/osThread.hpp" 53 #include "runtime/safepoint.hpp" 54 #include "runtime/signature.hpp" 55 #include "runtime/stubCodeGenerator.hpp" 56 #include "runtime/stubRoutines.hpp" 57 #include "runtime/sweeper.hpp" 58 #include "runtime/synchronizer.hpp" 59 #include "runtime/thread.inline.hpp" 60 #include "runtime/threadSMR.hpp" 61 #include "runtime/timerTrace.hpp" 62 #include "services/runtimeService.hpp" 63 #include "trace/tracing.hpp" 64 #include "trace/traceMacros.hpp" 65 #include "utilities/events.hpp" 66 #include "utilities/macros.hpp" 67 #if INCLUDE_ALL_GCS 68 #include "gc/cms/concurrentMarkSweepThread.hpp" 69 #include "gc/g1/suspendibleThreadSet.hpp" 70 #endif // INCLUDE_ALL_GCS 71 #ifdef COMPILER1 72 #include "c1/c1_globals.hpp" 73 #endif 74 75 // -------------------------------------------------------------------------------------------------- 76 // Implementation of Safepoint begin/end 77 78 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized; 79 volatile int SafepointSynchronize::_waiting_to_block = 0; 80 volatile int SafepointSynchronize::_safepoint_counter = 0; 81 int SafepointSynchronize::_current_jni_active_count = 0; 82 long SafepointSynchronize::_end_of_last_safepoint = 0; 83 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE 84 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only 85 static bool timeout_error_printed = false; 86 87 // Roll all threads forward to a safepoint and suspend them all 88 void SafepointSynchronize::begin() { 89 EventSafepointBegin begin_event; 90 Thread* myThread = Thread::current(); 91 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint"); 92 93 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) { 94 _safepoint_begin_time = os::javaTimeNanos(); 95 _ts_of_current_safepoint = tty->time_stamp().seconds(); 96 } 97 98 #if INCLUDE_ALL_GCS 99 if (UseConcMarkSweepGC) { 100 // In the future we should investigate whether CMS can use the 101 // more-general mechanism below. DLD (01/05). 102 ConcurrentMarkSweepThread::synchronize(false); 103 } else if (UseG1GC) { 104 SuspendibleThreadSet::synchronize(); 105 } 106 #endif // INCLUDE_ALL_GCS 107 108 // By getting the Threads_lock, we assure that no threads are about to start or 109 // exit. It is released again in SafepointSynchronize::end(). 110 Threads_lock->lock(); 111 112 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state"); 113 114 int nof_threads = Threads::number_of_threads(); 115 116 log_debug(safepoint)("Safepoint synchronization initiated. (%d)", nof_threads); 117 118 RuntimeService::record_safepoint_begin(); 119 120 MutexLocker mu(Safepoint_lock); 121 122 // Reset the count of active JNI critical threads 123 _current_jni_active_count = 0; 124 125 // Set number of threads to wait for, before we initiate the callbacks 126 _waiting_to_block = nof_threads; 127 TryingToBlock = 0 ; 128 int still_running = nof_threads; 129 130 // Save the starting time, so that it can be compared to see if this has taken 131 // too long to complete. 132 jlong safepoint_limit_time = 0; 133 timeout_error_printed = false; 134 135 // PrintSafepointStatisticsTimeout can be specified separately. When 136 // specified, PrintSafepointStatistics will be set to true in 137 // deferred_initialize_stat method. The initialization has to be done 138 // early enough to avoid any races. See bug 6880029 for details. 139 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) { 140 deferred_initialize_stat(); 141 } 142 143 // Begin the process of bringing the system to a safepoint. 144 // Java threads can be in several different states and are 145 // stopped by different mechanisms: 146 // 147 // 1. Running interpreted 148 // The interpreter dispatch table is changed to force it to 149 // check for a safepoint condition between bytecodes. 150 // 2. Running in native code 151 // When returning from the native code, a Java thread must check 152 // the safepoint _state to see if we must block. If the 153 // VM thread sees a Java thread in native, it does 154 // not wait for this thread to block. The order of the memory 155 // writes and reads of both the safepoint state and the Java 156 // threads state is critical. In order to guarantee that the 157 // memory writes are serialized with respect to each other, 158 // the VM thread issues a memory barrier instruction 159 // (on MP systems). In order to avoid the overhead of issuing 160 // a memory barrier for each Java thread making native calls, each Java 161 // thread performs a write to a single memory page after changing 162 // the thread state. The VM thread performs a sequence of 163 // mprotect OS calls which forces all previous writes from all 164 // Java threads to be serialized. This is done in the 165 // os::serialize_thread_states() call. This has proven to be 166 // much more efficient than executing a membar instruction 167 // on every call to native code. 168 // 3. Running compiled Code 169 // Compiled code reads a global (Safepoint Polling) page that 170 // is set to fault if we are trying to get to a safepoint. 171 // 4. Blocked 172 // A thread which is blocked will not be allowed to return from the 173 // block condition until the safepoint operation is complete. 174 // 5. In VM or Transitioning between states 175 // If a Java thread is currently running in the VM or transitioning 176 // between states, the safepointing code will wait for the thread to 177 // block itself when it attempts transitions to a new state. 178 // 179 { 180 EventSafepointStateSynchronization sync_event; 181 int initial_running = 0; 182 183 _state = _synchronizing; 184 OrderAccess::fence(); 185 186 // Flush all thread states to memory 187 if (!UseMembar) { 188 os::serialize_thread_states(); 189 } 190 191 // Make interpreter safepoint aware 192 Interpreter::notice_safepoints(); 193 194 if (DeferPollingPageLoopCount < 0) { 195 // Make polling safepoint aware 196 guarantee (PageArmed == 0, "invariant") ; 197 PageArmed = 1 ; 198 os::make_polling_page_unreadable(); 199 } 200 201 // Consider using active_processor_count() ... but that call is expensive. 202 int ncpus = os::processor_count() ; 203 unsigned int iterations = 0; 204 205 { 206 ThreadsListHandle tlh; 207 JavaThreadIterator jti(tlh.list()); 208 #ifdef ASSERT 209 for (JavaThread *cur = jti.first(); cur != NULL; cur = jti.next()) { 210 assert(cur->safepoint_state()->is_running(), "Illegal initial state"); 211 // Clear the visited flag to ensure that the critical counts are collected properly. 212 cur->set_visited_for_critical_count(false); 213 } 214 #endif // ASSERT 215 216 if (SafepointTimeout) 217 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS; 218 219 // Iterate through all threads until it have been determined how to stop them all at a safepoint 220 int steps = 0 ; 221 while(still_running > 0) { 222 for (JavaThread *cur = jti.first(); cur != NULL; cur = jti.next()) { 223 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended"); 224 ThreadSafepointState *cur_state = cur->safepoint_state(); 225 if (cur_state->is_running()) { 226 cur_state->examine_state_of_thread(); 227 if (!cur_state->is_running()) { 228 still_running--; 229 // consider adjusting steps downward: 230 // steps = 0 231 // steps -= NNN 232 // steps >>= 1 233 // steps = MIN(steps, 2000-100) 234 // if (iterations != 0) steps -= NNN 235 } 236 LogTarget(Trace, safepoint) lt; 237 if (lt.is_enabled()) { 238 ResourceMark rm; 239 LogStream ls(lt); 240 cur_state->print_on(&ls); 241 } 242 } 243 } 244 245 if (iterations == 0) { 246 initial_running = still_running; 247 if (PrintSafepointStatistics) { 248 begin_statistics(nof_threads, still_running); 249 } 250 } 251 252 if (still_running > 0) { 253 // Check for if it takes to long 254 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) { 255 print_safepoint_timeout(_spinning_timeout); 256 } 257 258 // Spin to avoid context switching. 259 // There's a tension between allowing the mutators to run (and rendezvous) 260 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that 261 // a mutator might otherwise use profitably to reach a safepoint. Excessive 262 // spinning by the VM thread on a saturated system can increase rendezvous latency. 263 // Blocking or yielding incur their own penalties in the form of context switching 264 // and the resultant loss of $ residency. 265 // 266 // Further complicating matters is that yield() does not work as naively expected 267 // on many platforms -- yield() does not guarantee that any other ready threads 268 // will run. As such we revert to naked_short_sleep() after some number of iterations. 269 // nakes_short_sleep() is implemented as a short unconditional sleep. 270 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping 271 // can actually increase the time it takes the VM thread to detect that a system-wide 272 // stop-the-world safepoint has been reached. In a pathological scenario such as that 273 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe. 274 // In that case the mutators will be stalled waiting for the safepoint to complete and the 275 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread 276 // will eventually wake up and detect that all mutators are safe, at which point 277 // we'll again make progress. 278 // 279 // Beware too that that the VMThread typically runs at elevated priority. 280 // Its default priority is higher than the default mutator priority. 281 // Obviously, this complicates spinning. 282 // 283 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0). 284 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will. 285 // 286 // See the comments in synchronizer.cpp for additional remarks on spinning. 287 // 288 // In the future we might: 289 // 1. Modify the safepoint scheme to avoid potentially unbounded spinning. 290 // This is tricky as the path used by a thread exiting the JVM (say on 291 // on JNI call-out) simply stores into its state field. The burden 292 // is placed on the VM thread, which must poll (spin). 293 // 2. Find something useful to do while spinning. If the safepoint is GC-related 294 // we might aggressively scan the stacks of threads that are already safe. 295 // 3. Use Solaris schedctl to examine the state of the still-running mutators. 296 // If all the mutators are ONPROC there's no reason to sleep or yield. 297 // 4. YieldTo() any still-running mutators that are ready but OFFPROC. 298 // 5. Check system saturation. If the system is not fully saturated then 299 // simply spin and avoid sleep/yield. 300 // 6. As still-running mutators rendezvous they could unpark the sleeping 301 // VMthread. This works well for still-running mutators that become 302 // safe. The VMthread must still poll for mutators that call-out. 303 // 7. Drive the policy on time-since-begin instead of iterations. 304 // 8. Consider making the spin duration a function of the # of CPUs: 305 // Spin = (((ncpus-1) * M) + K) + F(still_running) 306 // Alternately, instead of counting iterations of the outer loop 307 // we could count the # of threads visited in the inner loop, above. 308 // 9. On windows consider using the return value from SwitchThreadTo() 309 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions. 310 311 if (int(iterations) == DeferPollingPageLoopCount) { 312 guarantee (PageArmed == 0, "invariant") ; 313 PageArmed = 1 ; 314 os::make_polling_page_unreadable(); 315 } 316 317 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or 318 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus) 319 ++steps ; 320 if (ncpus > 1 && steps < SafepointSpinBeforeYield) { 321 SpinPause() ; // MP-Polite spin 322 } else 323 if (steps < DeferThrSuspendLoopCount) { 324 os::naked_yield() ; 325 } else { 326 os::naked_short_sleep(1); 327 } 328 329 iterations ++ ; 330 } 331 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long"); 332 } 333 } // ThreadsListHandle destroyed here. 334 assert(still_running == 0, "sanity check"); 335 336 if (PrintSafepointStatistics) { 337 update_statistics_on_spin_end(); 338 } 339 340 if (sync_event.should_commit()) { 341 sync_event.set_safepointId(safepoint_counter()); 342 sync_event.set_initialThreadCount(initial_running); 343 sync_event.set_runningThreadCount(_waiting_to_block); 344 sync_event.set_iterations(iterations); 345 sync_event.commit(); 346 } 347 } // EventSafepointStateSynchronization destroyed here. 348 349 // wait until all threads are stopped 350 { 351 EventSafepointWaitBlocked wait_blocked_event; 352 int initial_waiting_to_block = _waiting_to_block; 353 354 while (_waiting_to_block > 0) { 355 log_debug(safepoint)("Waiting for %d thread(s) to block", _waiting_to_block); 356 if (!SafepointTimeout || timeout_error_printed) { 357 Safepoint_lock->wait(true); // true, means with no safepoint checks 358 } else { 359 // Compute remaining time 360 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos(); 361 362 // If there is no remaining time, then there is an error 363 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) { 364 print_safepoint_timeout(_blocking_timeout); 365 } 366 } 367 } 368 assert(_waiting_to_block == 0, "sanity check"); 369 370 #ifndef PRODUCT 371 if (SafepointTimeout) { 372 jlong current_time = os::javaTimeNanos(); 373 if (safepoint_limit_time < current_time) { 374 tty->print_cr("# SafepointSynchronize: Finished after " 375 INT64_FORMAT_W(6) " ms", 376 (int64_t)((current_time - safepoint_limit_time) / MICROUNITS + 377 (jlong)SafepointTimeoutDelay)); 378 } 379 } 380 #endif 381 382 assert((_safepoint_counter & 0x1) == 0, "must be even"); 383 assert(Threads_lock->owned_by_self(), "must hold Threads_lock"); 384 _safepoint_counter ++; 385 386 // Record state 387 _state = _synchronized; 388 389 OrderAccess::fence(); 390 391 if (wait_blocked_event.should_commit()) { 392 wait_blocked_event.set_safepointId(safepoint_counter()); 393 wait_blocked_event.set_runningThreadCount(initial_waiting_to_block); 394 wait_blocked_event.commit(); 395 } 396 } // EventSafepointWaitBlocked 397 398 #ifdef ASSERT 399 { 400 // Make sure all the threads were visited. 401 ThreadsListHandle tlh; 402 JavaThreadIterator jti(tlh.list()); 403 for (JavaThread *cur = jti.first(); cur != NULL; cur = jti.next()) { 404 assert(cur->was_visited_for_critical_count(), "missed a thread"); 405 } 406 } 407 #endif // ASSERT 408 409 // Update the count of active JNI critical regions 410 GCLocker::set_jni_lock_count(_current_jni_active_count); 411 412 if (log_is_enabled(Debug, safepoint)) { 413 log_debug(safepoint)("Entering safepoint region: %s", VMThread::vm_safepoint_description()); 414 } 415 416 RuntimeService::record_safepoint_synchronized(); 417 if (PrintSafepointStatistics) { 418 update_statistics_on_sync_end(os::javaTimeNanos()); 419 } 420 421 // Call stuff that needs to be run when a safepoint is just about to be completed 422 { 423 EventSafepointCleanup cleanup_event; 424 do_cleanup_tasks(); 425 if (cleanup_event.should_commit()) { 426 cleanup_event.set_safepointId(safepoint_counter()); 427 cleanup_event.commit(); 428 } 429 } 430 431 if (PrintSafepointStatistics) { 432 // Record how much time spend on the above cleanup tasks 433 update_statistics_on_cleanup_end(os::javaTimeNanos()); 434 } 435 if (begin_event.should_commit()) { 436 begin_event.set_safepointId(safepoint_counter()); 437 begin_event.set_totalThreadCount(nof_threads); 438 begin_event.set_jniCriticalThreadCount(_current_jni_active_count); 439 begin_event.commit(); 440 } 441 } 442 443 // Wake up all threads, so they are ready to resume execution after the safepoint 444 // operation has been carried out 445 void SafepointSynchronize::end() { 446 EventSafepointEnd event; 447 int safepoint_id = safepoint_counter(); // Keep the odd counter as "id" 448 449 assert(Threads_lock->owned_by_self(), "must hold Threads_lock"); 450 assert((_safepoint_counter & 0x1) == 1, "must be odd"); 451 _safepoint_counter ++; 452 // memory fence isn't required here since an odd _safepoint_counter 453 // value can do no harm and a fence is issued below anyway. 454 455 DEBUG_ONLY(Thread* myThread = Thread::current();) 456 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint"); 457 458 if (PrintSafepointStatistics) { 459 end_statistics(os::javaTimeNanos()); 460 } 461 462 { 463 ThreadsListHandle tlh; 464 JavaThreadIterator jti(tlh.list()); 465 #ifdef ASSERT 466 // A pending_exception cannot be installed during a safepoint. The threads 467 // may install an async exception after they come back from a safepoint into 468 // pending_exception after they unblock. But that should happen later. 469 for (JavaThread *cur = jti.first(); cur != NULL; cur = jti.next()) { 470 assert (!(cur->has_pending_exception() && 471 cur->safepoint_state()->is_at_poll_safepoint()), 472 "safepoint installed a pending exception"); 473 } 474 #endif // ASSERT 475 476 if (PageArmed) { 477 // Make polling safepoint aware 478 os::make_polling_page_readable(); 479 PageArmed = 0 ; 480 } 481 482 // Remove safepoint check from interpreter 483 Interpreter::ignore_safepoints(); 484 485 { 486 MutexLocker mu(Safepoint_lock); 487 488 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization"); 489 490 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method 491 // when they get restarted. 492 _state = _not_synchronized; 493 OrderAccess::fence(); 494 495 log_debug(safepoint)("Leaving safepoint region"); 496 497 // Start suspended threads 498 for (JavaThread *current = jti.first(); current != NULL; current = jti.next()) { 499 // A problem occurring on Solaris is when attempting to restart threads 500 // the first #cpus - 1 go well, but then the VMThread is preempted when we get 501 // to the next one (since it has been running the longest). We then have 502 // to wait for a cpu to become available before we can continue restarting 503 // threads. 504 // FIXME: This causes the performance of the VM to degrade when active and with 505 // large numbers of threads. Apparently this is due to the synchronous nature 506 // of suspending threads. 507 // 508 // TODO-FIXME: the comments above are vestigial and no longer apply. 509 // Furthermore, using solaris' schedctl in this particular context confers no benefit 510 if (VMThreadHintNoPreempt) { 511 os::hint_no_preempt(); 512 } 513 ThreadSafepointState* cur_state = current->safepoint_state(); 514 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint"); 515 cur_state->restart(); 516 assert(cur_state->is_running(), "safepoint state has not been reset"); 517 } 518 519 RuntimeService::record_safepoint_end(); 520 521 // Release threads lock, so threads can be created/destroyed again. 522 // It will also release all threads blocked in signal_thread_blocked. 523 Threads_lock->unlock(); 524 } 525 } // ThreadsListHandle destroyed here. 526 527 #if INCLUDE_ALL_GCS 528 // If there are any concurrent GC threads resume them. 529 if (UseConcMarkSweepGC) { 530 ConcurrentMarkSweepThread::desynchronize(false); 531 } else if (UseG1GC) { 532 SuspendibleThreadSet::desynchronize(); 533 } 534 #endif // INCLUDE_ALL_GCS 535 // record this time so VMThread can keep track how much time has elapsed 536 // since last safepoint. 537 _end_of_last_safepoint = os::javaTimeMillis(); 538 539 if (event.should_commit()) { 540 event.set_safepointId(safepoint_id); 541 event.commit(); 542 } 543 } 544 545 bool SafepointSynchronize::is_cleanup_needed() { 546 // Need a safepoint if there are many monitors to deflate. 547 if (ObjectSynchronizer::is_cleanup_needed()) return true; 548 // Need a safepoint if some inline cache buffers is non-empty 549 if (!InlineCacheBuffer::is_empty()) return true; 550 return false; 551 } 552 553 static void event_safepoint_cleanup_task_commit(EventSafepointCleanupTask& event, const char* name) { 554 if (event.should_commit()) { 555 event.set_safepointId(SafepointSynchronize::safepoint_counter()); 556 event.set_name(name); 557 event.commit(); 558 } 559 } 560 561 class ParallelSPCleanupThreadClosure : public ThreadClosure { 562 private: 563 CodeBlobClosure* _nmethod_cl; 564 DeflateMonitorCounters* _counters; 565 566 public: 567 ParallelSPCleanupThreadClosure(DeflateMonitorCounters* counters) : 568 _counters(counters), 569 _nmethod_cl(NMethodSweeper::prepare_mark_active_nmethods()) {} 570 571 void do_thread(Thread* thread) { 572 ObjectSynchronizer::deflate_thread_local_monitors(thread, _counters); 573 if (_nmethod_cl != NULL && thread->is_Java_thread() && 574 ! thread->is_Code_cache_sweeper_thread()) { 575 JavaThread* jt = (JavaThread*) thread; 576 jt->nmethods_do(_nmethod_cl); 577 } 578 } 579 }; 580 581 class ParallelSPCleanupTask : public AbstractGangTask { 582 private: 583 SubTasksDone _subtasks; 584 ParallelSPCleanupThreadClosure _cleanup_threads_cl; 585 uint _num_workers; 586 DeflateMonitorCounters* _counters; 587 public: 588 ParallelSPCleanupTask(uint num_workers, DeflateMonitorCounters* counters) : 589 AbstractGangTask("Parallel Safepoint Cleanup"), 590 _cleanup_threads_cl(ParallelSPCleanupThreadClosure(counters)), 591 _num_workers(num_workers), 592 _subtasks(SubTasksDone(SafepointSynchronize::SAFEPOINT_CLEANUP_NUM_TASKS)), 593 _counters(counters) {} 594 595 void work(uint worker_id) { 596 // All threads deflate monitors and mark nmethods (if necessary). 597 Threads::parallel_java_threads_do(&_cleanup_threads_cl); 598 599 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_DEFLATE_MONITORS)) { 600 const char* name = "deflating idle monitors"; 601 EventSafepointCleanupTask event; 602 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup)); 603 ObjectSynchronizer::deflate_idle_monitors(_counters); 604 event_safepoint_cleanup_task_commit(event, name); 605 } 606 607 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_UPDATE_INLINE_CACHES)) { 608 const char* name = "updating inline caches"; 609 EventSafepointCleanupTask event; 610 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup)); 611 InlineCacheBuffer::update_inline_caches(); 612 event_safepoint_cleanup_task_commit(event, name); 613 } 614 615 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_COMPILATION_POLICY)) { 616 const char* name = "compilation policy safepoint handler"; 617 EventSafepointCleanupTask event; 618 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup)); 619 CompilationPolicy::policy()->do_safepoint_work(); 620 event_safepoint_cleanup_task_commit(event, name); 621 } 622 623 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_SYMBOL_TABLE_REHASH)) { 624 if (SymbolTable::needs_rehashing()) { 625 const char* name = "rehashing symbol table"; 626 EventSafepointCleanupTask event; 627 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup)); 628 SymbolTable::rehash_table(); 629 event_safepoint_cleanup_task_commit(event, name); 630 } 631 } 632 633 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_STRING_TABLE_REHASH)) { 634 if (StringTable::needs_rehashing()) { 635 const char* name = "rehashing string table"; 636 EventSafepointCleanupTask event; 637 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup)); 638 StringTable::rehash_table(); 639 event_safepoint_cleanup_task_commit(event, name); 640 } 641 } 642 643 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_CLD_PURGE)) { 644 // CMS delays purging the CLDG until the beginning of the next safepoint and to 645 // make sure concurrent sweep is done 646 const char* name = "purging class loader data graph"; 647 EventSafepointCleanupTask event; 648 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup)); 649 ClassLoaderDataGraph::purge_if_needed(); 650 event_safepoint_cleanup_task_commit(event, name); 651 } 652 _subtasks.all_tasks_completed(_num_workers); 653 } 654 }; 655 656 // Various cleaning tasks that should be done periodically at safepoints. 657 void SafepointSynchronize::do_cleanup_tasks() { 658 659 TraceTime timer("safepoint cleanup tasks", TRACETIME_LOG(Info, safepoint, cleanup)); 660 661 // Prepare for monitor deflation. 662 DeflateMonitorCounters deflate_counters; 663 ObjectSynchronizer::prepare_deflate_idle_monitors(&deflate_counters); 664 665 CollectedHeap* heap = Universe::heap(); 666 assert(heap != NULL, "heap not initialized yet?"); 667 WorkGang* cleanup_workers = heap->get_safepoint_workers(); 668 if (cleanup_workers != NULL) { 669 // Parallel cleanup using GC provided thread pool. 670 uint num_cleanup_workers = cleanup_workers->active_workers(); 671 ParallelSPCleanupTask cleanup(num_cleanup_workers, &deflate_counters); 672 StrongRootsScope srs(num_cleanup_workers); 673 cleanup_workers->run_task(&cleanup); 674 } else { 675 // Serial cleanup using VMThread. 676 ParallelSPCleanupTask cleanup(1, &deflate_counters); 677 StrongRootsScope srs(1); 678 cleanup.work(0); 679 } 680 681 // Finish monitor deflation. 682 ObjectSynchronizer::finish_deflate_idle_monitors(&deflate_counters); 683 } 684 685 686 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) { 687 switch(state) { 688 case _thread_in_native: 689 // native threads are safe if they have no java stack or have walkable stack 690 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable(); 691 692 // blocked threads should have already have walkable stack 693 case _thread_blocked: 694 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable"); 695 return true; 696 697 default: 698 return false; 699 } 700 } 701 702 703 // See if the thread is running inside a lazy critical native and 704 // update the thread critical count if so. Also set a suspend flag to 705 // cause the native wrapper to return into the JVM to do the unlock 706 // once the native finishes. 707 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) { 708 if (state == _thread_in_native && 709 thread->has_last_Java_frame() && 710 thread->frame_anchor()->walkable()) { 711 // This thread might be in a critical native nmethod so look at 712 // the top of the stack and increment the critical count if it 713 // is. 714 frame wrapper_frame = thread->last_frame(); 715 CodeBlob* stub_cb = wrapper_frame.cb(); 716 if (stub_cb != NULL && 717 stub_cb->is_nmethod() && 718 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) { 719 // A thread could potentially be in a critical native across 720 // more than one safepoint, so only update the critical state on 721 // the first one. When it returns it will perform the unlock. 722 if (!thread->do_critical_native_unlock()) { 723 #ifdef ASSERT 724 if (!thread->in_critical()) { 725 GCLocker::increment_debug_jni_lock_count(); 726 } 727 #endif 728 thread->enter_critical(); 729 // Make sure the native wrapper calls back on return to 730 // perform the needed critical unlock. 731 thread->set_critical_native_unlock(); 732 } 733 } 734 } 735 } 736 737 738 739 // ------------------------------------------------------------------------------------------------------- 740 // Implementation of Safepoint callback point 741 742 void SafepointSynchronize::block(JavaThread *thread) { 743 assert(thread != NULL, "thread must be set"); 744 assert(thread->is_Java_thread(), "not a Java thread"); 745 746 // Threads shouldn't block if they are in the middle of printing, but... 747 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id()); 748 749 // Only bail from the block() call if the thread is gone from the 750 // thread list; starting to exit should still block. 751 if (thread->is_terminated()) { 752 // block current thread if we come here from native code when VM is gone 753 thread->block_if_vm_exited(); 754 755 // otherwise do nothing 756 return; 757 } 758 759 JavaThreadState state = thread->thread_state(); 760 thread->frame_anchor()->make_walkable(thread); 761 762 // Check that we have a valid thread_state at this point 763 switch(state) { 764 case _thread_in_vm_trans: 765 case _thread_in_Java: // From compiled code 766 767 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case, 768 // we pretend we are still in the VM. 769 thread->set_thread_state(_thread_in_vm); 770 771 if (is_synchronizing()) { 772 Atomic::inc (&TryingToBlock) ; 773 } 774 775 // We will always be holding the Safepoint_lock when we are examine the state 776 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and 777 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code 778 Safepoint_lock->lock_without_safepoint_check(); 779 if (is_synchronizing()) { 780 // Decrement the number of threads to wait for and signal vm thread 781 assert(_waiting_to_block > 0, "sanity check"); 782 _waiting_to_block--; 783 thread->safepoint_state()->set_has_called_back(true); 784 785 DEBUG_ONLY(thread->set_visited_for_critical_count(true)); 786 if (thread->in_critical()) { 787 // Notice that this thread is in a critical section 788 increment_jni_active_count(); 789 } 790 791 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread 792 if (_waiting_to_block == 0) { 793 Safepoint_lock->notify_all(); 794 } 795 } 796 797 // We transition the thread to state _thread_blocked here, but 798 // we can't do our usual check for external suspension and then 799 // self-suspend after the lock_without_safepoint_check() call 800 // below because we are often called during transitions while 801 // we hold different locks. That would leave us suspended while 802 // holding a resource which results in deadlocks. 803 thread->set_thread_state(_thread_blocked); 804 Safepoint_lock->unlock(); 805 806 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during 807 // the entire safepoint, the threads will all line up here during the safepoint. 808 Threads_lock->lock_without_safepoint_check(); 809 // restore original state. This is important if the thread comes from compiled code, so it 810 // will continue to execute with the _thread_in_Java state. 811 thread->set_thread_state(state); 812 Threads_lock->unlock(); 813 break; 814 815 case _thread_in_native_trans: 816 case _thread_blocked_trans: 817 case _thread_new_trans: 818 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) { 819 thread->print_thread_state(); 820 fatal("Deadlock in safepoint code. " 821 "Should have called back to the VM before blocking."); 822 } 823 824 // We transition the thread to state _thread_blocked here, but 825 // we can't do our usual check for external suspension and then 826 // self-suspend after the lock_without_safepoint_check() call 827 // below because we are often called during transitions while 828 // we hold different locks. That would leave us suspended while 829 // holding a resource which results in deadlocks. 830 thread->set_thread_state(_thread_blocked); 831 832 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence, 833 // the safepoint code might still be waiting for it to block. We need to change the state here, 834 // so it can see that it is at a safepoint. 835 836 // Block until the safepoint operation is completed. 837 Threads_lock->lock_without_safepoint_check(); 838 839 // Restore state 840 thread->set_thread_state(state); 841 842 Threads_lock->unlock(); 843 break; 844 845 default: 846 fatal("Illegal threadstate encountered: %d", state); 847 } 848 849 // Check for pending. async. exceptions or suspends - except if the 850 // thread was blocked inside the VM. has_special_runtime_exit_condition() 851 // is called last since it grabs a lock and we only want to do that when 852 // we must. 853 // 854 // Note: we never deliver an async exception at a polling point as the 855 // compiler may not have an exception handler for it. The polling 856 // code will notice the async and deoptimize and the exception will 857 // be delivered. (Polling at a return point is ok though). Sure is 858 // a lot of bother for a deprecated feature... 859 // 860 // We don't deliver an async exception if the thread state is 861 // _thread_in_native_trans so JNI functions won't be called with 862 // a surprising pending exception. If the thread state is going back to java, 863 // async exception is checked in check_special_condition_for_native_trans(). 864 865 if (state != _thread_blocked_trans && 866 state != _thread_in_vm_trans && 867 thread->has_special_runtime_exit_condition()) { 868 thread->handle_special_runtime_exit_condition( 869 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans)); 870 } 871 } 872 873 // ------------------------------------------------------------------------------------------------------ 874 // Exception handlers 875 876 877 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) { 878 assert(thread->is_Java_thread(), "polling reference encountered by VM thread"); 879 assert(thread->thread_state() == _thread_in_Java, "should come from Java code"); 880 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization"); 881 882 if (ShowSafepointMsgs) { 883 tty->print("handle_polling_page_exception: "); 884 } 885 886 if (PrintSafepointStatistics) { 887 inc_page_trap_count(); 888 } 889 890 ThreadSafepointState* state = thread->safepoint_state(); 891 892 state->handle_polling_page_exception(); 893 } 894 895 896 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) { 897 if (!timeout_error_printed) { 898 timeout_error_printed = true; 899 // Print out the thread info which didn't reach the safepoint for debugging 900 // purposes (useful when there are lots of threads in the debugger). 901 tty->cr(); 902 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:"); 903 if (reason == _spinning_timeout) { 904 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint."); 905 } else if (reason == _blocking_timeout) { 906 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop."); 907 } 908 909 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:"); 910 ThreadSafepointState *cur_state; 911 ResourceMark rm; 912 { 913 ThreadsListHandle tlh; 914 JavaThreadIterator jti(tlh.list()); 915 for (JavaThread *cur_thread = jti.first(); cur_thread != NULL; cur_thread = jti.next()) { 916 cur_state = cur_thread->safepoint_state(); 917 918 if (cur_thread->thread_state() != _thread_blocked && 919 ((reason == _spinning_timeout && cur_state->is_running()) || 920 (reason == _blocking_timeout && !cur_state->has_called_back()))) { 921 tty->print("# "); 922 cur_thread->print(); 923 tty->cr(); 924 } 925 } 926 } 927 tty->print_cr("# SafepointSynchronize::begin: (End of list)"); 928 } 929 930 // To debug the long safepoint, specify both DieOnSafepointTimeout & 931 // ShowMessageBoxOnError. 932 if (DieOnSafepointTimeout) { 933 fatal("Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.", 934 SafepointTimeoutDelay, VMThread::vm_safepoint_description()); 935 } 936 } 937 938 939 // ------------------------------------------------------------------------------------------------------- 940 // Implementation of ThreadSafepointState 941 942 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) { 943 _thread = thread; 944 _type = _running; 945 _has_called_back = false; 946 _at_poll_safepoint = false; 947 } 948 949 void ThreadSafepointState::create(JavaThread *thread) { 950 ThreadSafepointState *state = new ThreadSafepointState(thread); 951 thread->set_safepoint_state(state); 952 } 953 954 void ThreadSafepointState::destroy(JavaThread *thread) { 955 if (thread->safepoint_state()) { 956 delete(thread->safepoint_state()); 957 thread->set_safepoint_state(NULL); 958 } 959 } 960 961 void ThreadSafepointState::examine_state_of_thread() { 962 assert(is_running(), "better be running or just have hit safepoint poll"); 963 964 JavaThreadState state = _thread->thread_state(); 965 966 // Save the state at the start of safepoint processing. 967 _orig_thread_state = state; 968 969 // Check for a thread that is suspended. Note that thread resume tries 970 // to grab the Threads_lock which we own here, so a thread cannot be 971 // resumed during safepoint synchronization. 972 973 // We check to see if this thread is suspended without locking to 974 // avoid deadlocking with a third thread that is waiting for this 975 // thread to be suspended. The third thread can notice the safepoint 976 // that we're trying to start at the beginning of its SR_lock->wait() 977 // call. If that happens, then the third thread will block on the 978 // safepoint while still holding the underlying SR_lock. We won't be 979 // able to get the SR_lock and we'll deadlock. 980 // 981 // We don't need to grab the SR_lock here for two reasons: 982 // 1) The suspend flags are both volatile and are set with an 983 // Atomic::cmpxchg() call so we should see the suspended 984 // state right away. 985 // 2) We're being called from the safepoint polling loop; if 986 // we don't see the suspended state on this iteration, then 987 // we'll come around again. 988 // 989 bool is_suspended = _thread->is_ext_suspended(); 990 if (is_suspended) { 991 roll_forward(_at_safepoint); 992 return; 993 } 994 995 // Some JavaThread states have an initial safepoint state of 996 // running, but are actually at a safepoint. We will happily 997 // agree and update the safepoint state here. 998 if (SafepointSynchronize::safepoint_safe(_thread, state)) { 999 SafepointSynchronize::check_for_lazy_critical_native(_thread, state); 1000 roll_forward(_at_safepoint); 1001 return; 1002 } 1003 1004 if (state == _thread_in_vm) { 1005 roll_forward(_call_back); 1006 return; 1007 } 1008 1009 // All other thread states will continue to run until they 1010 // transition and self-block in state _blocked 1011 // Safepoint polling in compiled code causes the Java threads to do the same. 1012 // Note: new threads may require a malloc so they must be allowed to finish 1013 1014 assert(is_running(), "examine_state_of_thread on non-running thread"); 1015 return; 1016 } 1017 1018 // Returns true is thread could not be rolled forward at present position. 1019 void ThreadSafepointState::roll_forward(suspend_type type) { 1020 _type = type; 1021 1022 switch(_type) { 1023 case _at_safepoint: 1024 SafepointSynchronize::signal_thread_at_safepoint(); 1025 DEBUG_ONLY(_thread->set_visited_for_critical_count(true)); 1026 if (_thread->in_critical()) { 1027 // Notice that this thread is in a critical section 1028 SafepointSynchronize::increment_jni_active_count(); 1029 } 1030 break; 1031 1032 case _call_back: 1033 set_has_called_back(false); 1034 break; 1035 1036 case _running: 1037 default: 1038 ShouldNotReachHere(); 1039 } 1040 } 1041 1042 void ThreadSafepointState::restart() { 1043 switch(type()) { 1044 case _at_safepoint: 1045 case _call_back: 1046 break; 1047 1048 case _running: 1049 default: 1050 tty->print_cr("restart thread " INTPTR_FORMAT " with state %d", 1051 p2i(_thread), _type); 1052 _thread->print(); 1053 ShouldNotReachHere(); 1054 } 1055 _type = _running; 1056 set_has_called_back(false); 1057 } 1058 1059 1060 void ThreadSafepointState::print_on(outputStream *st) const { 1061 const char *s = NULL; 1062 1063 switch(_type) { 1064 case _running : s = "_running"; break; 1065 case _at_safepoint : s = "_at_safepoint"; break; 1066 case _call_back : s = "_call_back"; break; 1067 default: 1068 ShouldNotReachHere(); 1069 } 1070 1071 st->print_cr("Thread: " INTPTR_FORMAT 1072 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d", 1073 p2i(_thread), _thread->osthread()->thread_id(), s, _has_called_back, 1074 _at_poll_safepoint); 1075 1076 _thread->print_thread_state_on(st); 1077 } 1078 1079 // --------------------------------------------------------------------------------------------------------------------- 1080 1081 // Block the thread at the safepoint poll or poll return. 1082 void ThreadSafepointState::handle_polling_page_exception() { 1083 1084 // Check state. block() will set thread state to thread_in_vm which will 1085 // cause the safepoint state _type to become _call_back. 1086 assert(type() == ThreadSafepointState::_running, 1087 "polling page exception on thread not running state"); 1088 1089 // Step 1: Find the nmethod from the return address 1090 if (ShowSafepointMsgs && Verbose) { 1091 tty->print_cr("Polling page exception at " INTPTR_FORMAT, p2i(thread()->saved_exception_pc())); 1092 } 1093 address real_return_addr = thread()->saved_exception_pc(); 1094 1095 CodeBlob *cb = CodeCache::find_blob(real_return_addr); 1096 assert(cb != NULL && cb->is_compiled(), "return address should be in nmethod"); 1097 CompiledMethod* nm = (CompiledMethod*)cb; 1098 1099 // Find frame of caller 1100 frame stub_fr = thread()->last_frame(); 1101 CodeBlob* stub_cb = stub_fr.cb(); 1102 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub"); 1103 RegisterMap map(thread(), true); 1104 frame caller_fr = stub_fr.sender(&map); 1105 1106 // Should only be poll_return or poll 1107 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" ); 1108 1109 // This is a poll immediately before a return. The exception handling code 1110 // has already had the effect of causing the return to occur, so the execution 1111 // will continue immediately after the call. In addition, the oopmap at the 1112 // return point does not mark the return value as an oop (if it is), so 1113 // it needs a handle here to be updated. 1114 if( nm->is_at_poll_return(real_return_addr) ) { 1115 // See if return type is an oop. 1116 bool return_oop = nm->method()->is_returning_oop(); 1117 Handle return_value; 1118 if (return_oop) { 1119 // The oop result has been saved on the stack together with all 1120 // the other registers. In order to preserve it over GCs we need 1121 // to keep it in a handle. 1122 oop result = caller_fr.saved_oop_result(&map); 1123 assert(oopDesc::is_oop_or_null(result), "must be oop"); 1124 return_value = Handle(thread(), result); 1125 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer"); 1126 } 1127 1128 // Block the thread 1129 SafepointSynchronize::block(thread()); 1130 1131 // restore oop result, if any 1132 if (return_oop) { 1133 caller_fr.set_saved_oop_result(&map, return_value()); 1134 } 1135 } 1136 1137 // This is a safepoint poll. Verify the return address and block. 1138 else { 1139 set_at_poll_safepoint(true); 1140 1141 // verify the blob built the "return address" correctly 1142 assert(real_return_addr == caller_fr.pc(), "must match"); 1143 1144 // Block the thread 1145 SafepointSynchronize::block(thread()); 1146 set_at_poll_safepoint(false); 1147 1148 // If we have a pending async exception deoptimize the frame 1149 // as otherwise we may never deliver it. 1150 if (thread()->has_async_condition()) { 1151 ThreadInVMfromJavaNoAsyncException __tiv(thread()); 1152 Deoptimization::deoptimize_frame(thread(), caller_fr.id()); 1153 } 1154 1155 // If an exception has been installed we must check for a pending deoptimization 1156 // Deoptimize frame if exception has been thrown. 1157 1158 if (thread()->has_pending_exception() ) { 1159 RegisterMap map(thread(), true); 1160 frame caller_fr = stub_fr.sender(&map); 1161 if (caller_fr.is_deoptimized_frame()) { 1162 // The exception patch will destroy registers that are still 1163 // live and will be needed during deoptimization. Defer the 1164 // Async exception should have deferred the exception until the 1165 // next safepoint which will be detected when we get into 1166 // the interpreter so if we have an exception now things 1167 // are messed up. 1168 1169 fatal("Exception installed and deoptimization is pending"); 1170 } 1171 } 1172 } 1173 } 1174 1175 1176 // 1177 // Statistics & Instrumentations 1178 // 1179 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL; 1180 jlong SafepointSynchronize::_safepoint_begin_time = 0; 1181 int SafepointSynchronize::_cur_stat_index = 0; 1182 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating]; 1183 julong SafepointSynchronize::_coalesced_vmop_count = 0; 1184 jlong SafepointSynchronize::_max_sync_time = 0; 1185 jlong SafepointSynchronize::_max_vmop_time = 0; 1186 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f; 1187 1188 static jlong cleanup_end_time = 0; 1189 static bool need_to_track_page_armed_status = false; 1190 static bool init_done = false; 1191 1192 // Helper method to print the header. 1193 static void print_header() { 1194 // The number of spaces is significant here, and should match the format 1195 // specifiers in print_statistics(). 1196 1197 tty->print(" vmop " 1198 "[ threads: total initially_running wait_to_block ]" 1199 "[ time: spin block sync cleanup vmop ] "); 1200 1201 // no page armed status printed out if it is always armed. 1202 if (need_to_track_page_armed_status) { 1203 tty->print("page_armed "); 1204 } 1205 1206 tty->print_cr("page_trap_count"); 1207 } 1208 1209 void SafepointSynchronize::deferred_initialize_stat() { 1210 if (init_done) return; 1211 1212 // If PrintSafepointStatisticsTimeout is specified, the statistics data will 1213 // be printed right away, in which case, _safepoint_stats will regress to 1214 // a single element array. Otherwise, it is a circular ring buffer with default 1215 // size of PrintSafepointStatisticsCount. 1216 int stats_array_size; 1217 if (PrintSafepointStatisticsTimeout > 0) { 1218 stats_array_size = 1; 1219 PrintSafepointStatistics = true; 1220 } else { 1221 stats_array_size = PrintSafepointStatisticsCount; 1222 } 1223 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size 1224 * sizeof(SafepointStats), mtInternal); 1225 guarantee(_safepoint_stats != NULL, 1226 "not enough memory for safepoint instrumentation data"); 1227 1228 if (DeferPollingPageLoopCount >= 0) { 1229 need_to_track_page_armed_status = true; 1230 } 1231 init_done = true; 1232 } 1233 1234 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) { 1235 assert(init_done, "safepoint statistics array hasn't been initialized"); 1236 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1237 1238 spstat->_time_stamp = _ts_of_current_safepoint; 1239 1240 VM_Operation *op = VMThread::vm_operation(); 1241 spstat->_vmop_type = (op != NULL ? op->type() : -1); 1242 if (op != NULL) { 1243 _safepoint_reasons[spstat->_vmop_type]++; 1244 } 1245 1246 spstat->_nof_total_threads = nof_threads; 1247 spstat->_nof_initial_running_threads = nof_running; 1248 spstat->_nof_threads_hit_page_trap = 0; 1249 1250 // Records the start time of spinning. The real time spent on spinning 1251 // will be adjusted when spin is done. Same trick is applied for time 1252 // spent on waiting for threads to block. 1253 if (nof_running != 0) { 1254 spstat->_time_to_spin = os::javaTimeNanos(); 1255 } else { 1256 spstat->_time_to_spin = 0; 1257 } 1258 } 1259 1260 void SafepointSynchronize::update_statistics_on_spin_end() { 1261 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1262 1263 jlong cur_time = os::javaTimeNanos(); 1264 1265 spstat->_nof_threads_wait_to_block = _waiting_to_block; 1266 if (spstat->_nof_initial_running_threads != 0) { 1267 spstat->_time_to_spin = cur_time - spstat->_time_to_spin; 1268 } 1269 1270 if (need_to_track_page_armed_status) { 1271 spstat->_page_armed = (PageArmed == 1); 1272 } 1273 1274 // Records the start time of waiting for to block. Updated when block is done. 1275 if (_waiting_to_block != 0) { 1276 spstat->_time_to_wait_to_block = cur_time; 1277 } else { 1278 spstat->_time_to_wait_to_block = 0; 1279 } 1280 } 1281 1282 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) { 1283 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1284 1285 if (spstat->_nof_threads_wait_to_block != 0) { 1286 spstat->_time_to_wait_to_block = end_time - 1287 spstat->_time_to_wait_to_block; 1288 } 1289 1290 // Records the end time of sync which will be used to calculate the total 1291 // vm operation time. Again, the real time spending in syncing will be deducted 1292 // from the start of the sync time later when end_statistics is called. 1293 spstat->_time_to_sync = end_time - _safepoint_begin_time; 1294 if (spstat->_time_to_sync > _max_sync_time) { 1295 _max_sync_time = spstat->_time_to_sync; 1296 } 1297 1298 spstat->_time_to_do_cleanups = end_time; 1299 } 1300 1301 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) { 1302 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1303 1304 // Record how long spent in cleanup tasks. 1305 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups; 1306 1307 cleanup_end_time = end_time; 1308 } 1309 1310 void SafepointSynchronize::end_statistics(jlong vmop_end_time) { 1311 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1312 1313 // Update the vm operation time. 1314 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time; 1315 if (spstat->_time_to_exec_vmop > _max_vmop_time) { 1316 _max_vmop_time = spstat->_time_to_exec_vmop; 1317 } 1318 // Only the sync time longer than the specified 1319 // PrintSafepointStatisticsTimeout will be printed out right away. 1320 // By default, it is -1 meaning all samples will be put into the list. 1321 if ( PrintSafepointStatisticsTimeout > 0) { 1322 if (spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) { 1323 print_statistics(); 1324 } 1325 } else { 1326 // The safepoint statistics will be printed out when the _safepoin_stats 1327 // array fills up. 1328 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) { 1329 print_statistics(); 1330 _cur_stat_index = 0; 1331 } else { 1332 _cur_stat_index++; 1333 } 1334 } 1335 } 1336 1337 void SafepointSynchronize::print_statistics() { 1338 for (int index = 0; index <= _cur_stat_index; index++) { 1339 if (index % 30 == 0) { 1340 print_header(); 1341 } 1342 SafepointStats* sstats = &_safepoint_stats[index]; 1343 tty->print("%8.3f: ", sstats->_time_stamp); 1344 tty->print("%-30s [ " 1345 INT32_FORMAT_W(8) " " INT32_FORMAT_W(17) " " INT32_FORMAT_W(13) " " 1346 "]", 1347 (sstats->_vmop_type == -1 ? "no vm operation" : VM_Operation::name(sstats->_vmop_type)), 1348 sstats->_nof_total_threads, 1349 sstats->_nof_initial_running_threads, 1350 sstats->_nof_threads_wait_to_block); 1351 // "/ MICROUNITS " is to convert the unit from nanos to millis. 1352 tty->print("[ " 1353 INT64_FORMAT_W(7) " " INT64_FORMAT_W(7) " " 1354 INT64_FORMAT_W(7) " " INT64_FORMAT_W(7) " " 1355 INT64_FORMAT_W(7) " ] ", 1356 (int64_t)(sstats->_time_to_spin / MICROUNITS), 1357 (int64_t)(sstats->_time_to_wait_to_block / MICROUNITS), 1358 (int64_t)(sstats->_time_to_sync / MICROUNITS), 1359 (int64_t)(sstats->_time_to_do_cleanups / MICROUNITS), 1360 (int64_t)(sstats->_time_to_exec_vmop / MICROUNITS)); 1361 1362 if (need_to_track_page_armed_status) { 1363 tty->print(INT32_FORMAT_W(10) " ", sstats->_page_armed); 1364 } 1365 tty->print_cr(INT32_FORMAT_W(15) " ", sstats->_nof_threads_hit_page_trap); 1366 } 1367 } 1368 1369 // This method will be called when VM exits. It will first call 1370 // print_statistics to print out the rest of the sampling. Then 1371 // it tries to summarize the sampling. 1372 void SafepointSynchronize::print_stat_on_exit() { 1373 if (_safepoint_stats == NULL) return; 1374 1375 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1376 1377 // During VM exit, end_statistics may not get called and in that 1378 // case, if the sync time is less than PrintSafepointStatisticsTimeout, 1379 // don't print it out. 1380 // Approximate the vm op time. 1381 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop = 1382 os::javaTimeNanos() - cleanup_end_time; 1383 1384 if ( PrintSafepointStatisticsTimeout < 0 || 1385 spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) { 1386 print_statistics(); 1387 } 1388 tty->cr(); 1389 1390 // Print out polling page sampling status. 1391 if (!need_to_track_page_armed_status) { 1392 tty->print_cr("Polling page always armed"); 1393 } else { 1394 tty->print_cr("Defer polling page loop count = " INTX_FORMAT "\n", 1395 DeferPollingPageLoopCount); 1396 } 1397 1398 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) { 1399 if (_safepoint_reasons[index] != 0) { 1400 tty->print_cr("%-26s" UINT64_FORMAT_W(10), VM_Operation::name(index), 1401 _safepoint_reasons[index]); 1402 } 1403 } 1404 1405 tty->print_cr(UINT64_FORMAT_W(5) " VM operations coalesced during safepoint", 1406 _coalesced_vmop_count); 1407 tty->print_cr("Maximum sync time " INT64_FORMAT_W(5) " ms", 1408 (int64_t)(_max_sync_time / MICROUNITS)); 1409 tty->print_cr("Maximum vm operation time (except for Exit VM operation) " 1410 INT64_FORMAT_W(5) " ms", 1411 (int64_t)(_max_vmop_time / MICROUNITS)); 1412 } 1413 1414 // ------------------------------------------------------------------------------------------------ 1415 // Non-product code 1416 1417 #ifndef PRODUCT 1418 1419 void SafepointSynchronize::print_state() { 1420 if (_state == _not_synchronized) { 1421 tty->print_cr("not synchronized"); 1422 } else if (_state == _synchronizing || _state == _synchronized) { 1423 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" : 1424 "synchronized"); 1425 1426 ThreadsListHandle tlh; 1427 JavaThreadIterator jti(tlh.list()); 1428 for (JavaThread *cur = jti.first(); cur != NULL; cur = jti.next()) { 1429 cur->safepoint_state()->print(); 1430 } 1431 } 1432 } 1433 1434 void SafepointSynchronize::safepoint_msg(const char* format, ...) { 1435 if (ShowSafepointMsgs) { 1436 va_list ap; 1437 va_start(ap, format); 1438 tty->vprint_cr(format, ap); 1439 va_end(ap); 1440 } 1441 } 1442 1443 #endif // !PRODUCT