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