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 "oops/valueKlass.hpp" 46 #include "runtime/atomic.hpp" 47 #include "runtime/compilationPolicy.hpp" 48 #include "runtime/deoptimization.hpp" 49 #include "runtime/frame.inline.hpp" 50 #include "runtime/interfaceSupport.hpp" 51 #include "runtime/mutexLocker.hpp" 52 #include "runtime/orderAccess.inline.hpp" 53 #include "runtime/osThread.hpp" 54 #include "runtime/safepoint.hpp" 55 #include "runtime/signature.hpp" 56 #include "runtime/stubCodeGenerator.hpp" 57 #include "runtime/stubRoutines.hpp" 58 #include "runtime/sweeper.hpp" 59 #include "runtime/synchronizer.hpp" 60 #include "runtime/thread.inline.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() ; 203 204 #ifdef ASSERT 205 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) { 206 assert(cur->safepoint_state()->is_running(), "Illegal initial state"); 207 // Clear the visited flag to ensure that the critical counts are collected properly. 208 cur->set_visited_for_critical_count(false); 209 } 210 #endif // ASSERT 211 212 if (SafepointTimeout) 213 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS; 214 215 // Iterate through all threads until it have been determined how to stop them all at a safepoint 216 unsigned int iterations = 0; 217 int steps = 0 ; 218 while(still_running > 0) { 219 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) { 220 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended"); 221 ThreadSafepointState *cur_state = cur->safepoint_state(); 222 if (cur_state->is_running()) { 223 cur_state->examine_state_of_thread(); 224 if (!cur_state->is_running()) { 225 still_running--; 226 // consider adjusting steps downward: 227 // steps = 0 228 // steps -= NNN 229 // steps >>= 1 230 // steps = MIN(steps, 2000-100) 231 // if (iterations != 0) steps -= NNN 232 } 233 LogTarget(Trace, safepoint) lt; 234 if (lt.is_enabled()) { 235 ResourceMark rm; 236 LogStream ls(lt); 237 cur_state->print_on(&ls); 238 } 239 } 240 } 241 242 if (iterations == 0) { 243 initial_running = still_running; 244 if (PrintSafepointStatistics) { 245 begin_statistics(nof_threads, still_running); 246 } 247 } 248 249 if (still_running > 0) { 250 // Check for if it takes to long 251 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) { 252 print_safepoint_timeout(_spinning_timeout); 253 } 254 255 // Spin to avoid context switching. 256 // There's a tension between allowing the mutators to run (and rendezvous) 257 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that 258 // a mutator might otherwise use profitably to reach a safepoint. Excessive 259 // spinning by the VM thread on a saturated system can increase rendezvous latency. 260 // Blocking or yielding incur their own penalties in the form of context switching 261 // and the resultant loss of $ residency. 262 // 263 // Further complicating matters is that yield() does not work as naively expected 264 // on many platforms -- yield() does not guarantee that any other ready threads 265 // will run. As such we revert to naked_short_sleep() after some number of iterations. 266 // nakes_short_sleep() is implemented as a short unconditional sleep. 267 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping 268 // can actually increase the time it takes the VM thread to detect that a system-wide 269 // stop-the-world safepoint has been reached. In a pathological scenario such as that 270 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe. 271 // In that case the mutators will be stalled waiting for the safepoint to complete and the 272 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread 273 // will eventually wake up and detect that all mutators are safe, at which point 274 // we'll again make progress. 275 // 276 // Beware too that that the VMThread typically runs at elevated priority. 277 // Its default priority is higher than the default mutator priority. 278 // Obviously, this complicates spinning. 279 // 280 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0). 281 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will. 282 // 283 // See the comments in synchronizer.cpp for additional remarks on spinning. 284 // 285 // In the future we might: 286 // 1. Modify the safepoint scheme to avoid potentially unbounded spinning. 287 // This is tricky as the path used by a thread exiting the JVM (say on 288 // on JNI call-out) simply stores into its state field. The burden 289 // is placed on the VM thread, which must poll (spin). 290 // 2. Find something useful to do while spinning. If the safepoint is GC-related 291 // we might aggressively scan the stacks of threads that are already safe. 292 // 3. Use Solaris schedctl to examine the state of the still-running mutators. 293 // If all the mutators are ONPROC there's no reason to sleep or yield. 294 // 4. YieldTo() any still-running mutators that are ready but OFFPROC. 295 // 5. Check system saturation. If the system is not fully saturated then 296 // simply spin and avoid sleep/yield. 297 // 6. As still-running mutators rendezvous they could unpark the sleeping 298 // VMthread. This works well for still-running mutators that become 299 // safe. The VMthread must still poll for mutators that call-out. 300 // 7. Drive the policy on time-since-begin instead of iterations. 301 // 8. Consider making the spin duration a function of the # of CPUs: 302 // Spin = (((ncpus-1) * M) + K) + F(still_running) 303 // Alternately, instead of counting iterations of the outer loop 304 // we could count the # of threads visited in the inner loop, above. 305 // 9. On windows consider using the return value from SwitchThreadTo() 306 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions. 307 308 if (int(iterations) == DeferPollingPageLoopCount) { 309 guarantee (PageArmed == 0, "invariant") ; 310 PageArmed = 1 ; 311 os::make_polling_page_unreadable(); 312 } 313 314 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or 315 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus) 316 ++steps ; 317 if (ncpus > 1 && steps < SafepointSpinBeforeYield) { 318 SpinPause() ; // MP-Polite spin 319 } else 320 if (steps < DeferThrSuspendLoopCount) { 321 os::naked_yield() ; 322 } else { 323 os::naked_short_sleep(1); 324 } 325 326 iterations ++ ; 327 } 328 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long"); 329 } 330 assert(still_running == 0, "sanity check"); 331 332 if (PrintSafepointStatistics) { 333 update_statistics_on_spin_end(); 334 } 335 336 if (sync_event.should_commit()) { 337 sync_event.set_safepointId(safepoint_counter()); 338 sync_event.set_initialThreadCount(initial_running); 339 sync_event.set_runningThreadCount(_waiting_to_block); 340 sync_event.set_iterations(iterations); 341 sync_event.commit(); 342 } 343 } //EventSafepointStateSync 344 345 // wait until all threads are stopped 346 { 347 EventSafepointWaitBlocked wait_blocked_event; 348 int initial_waiting_to_block = _waiting_to_block; 349 350 while (_waiting_to_block > 0) { 351 log_debug(safepoint)("Waiting for %d thread(s) to block", _waiting_to_block); 352 if (!SafepointTimeout || timeout_error_printed) { 353 Safepoint_lock->wait(true); // true, means with no safepoint checks 354 } else { 355 // Compute remaining time 356 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos(); 357 358 // If there is no remaining time, then there is an error 359 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) { 360 print_safepoint_timeout(_blocking_timeout); 361 } 362 } 363 } 364 assert(_waiting_to_block == 0, "sanity check"); 365 366 #ifndef PRODUCT 367 if (SafepointTimeout) { 368 jlong current_time = os::javaTimeNanos(); 369 if (safepoint_limit_time < current_time) { 370 tty->print_cr("# SafepointSynchronize: Finished after " 371 INT64_FORMAT_W(6) " ms", 372 (int64_t)((current_time - safepoint_limit_time) / MICROUNITS + 373 (jlong)SafepointTimeoutDelay)); 374 } 375 } 376 #endif 377 378 assert((_safepoint_counter & 0x1) == 0, "must be even"); 379 assert(Threads_lock->owned_by_self(), "must hold Threads_lock"); 380 _safepoint_counter ++; 381 382 // Record state 383 _state = _synchronized; 384 385 OrderAccess::fence(); 386 387 if (wait_blocked_event.should_commit()) { 388 wait_blocked_event.set_safepointId(safepoint_counter()); 389 wait_blocked_event.set_runningThreadCount(initial_waiting_to_block); 390 wait_blocked_event.commit(); 391 } 392 } // EventSafepointWaitBlocked 393 394 #ifdef ASSERT 395 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) { 396 // make sure all the threads were visited 397 assert(cur->was_visited_for_critical_count(), "missed a thread"); 398 } 399 #endif // ASSERT 400 401 // Update the count of active JNI critical regions 402 GCLocker::set_jni_lock_count(_current_jni_active_count); 403 404 if (log_is_enabled(Debug, safepoint)) { 405 log_debug(safepoint)("Entering safepoint region: %s", VMThread::vm_safepoint_description()); 406 } 407 408 RuntimeService::record_safepoint_synchronized(); 409 if (PrintSafepointStatistics) { 410 update_statistics_on_sync_end(os::javaTimeNanos()); 411 } 412 413 // Call stuff that needs to be run when a safepoint is just about to be completed 414 { 415 EventSafepointCleanup cleanup_event; 416 do_cleanup_tasks(); 417 if (cleanup_event.should_commit()) { 418 cleanup_event.set_safepointId(safepoint_counter()); 419 cleanup_event.commit(); 420 } 421 } 422 423 if (PrintSafepointStatistics) { 424 // Record how much time spend on the above cleanup tasks 425 update_statistics_on_cleanup_end(os::javaTimeNanos()); 426 } 427 if (begin_event.should_commit()) { 428 begin_event.set_safepointId(safepoint_counter()); 429 begin_event.set_totalThreadCount(nof_threads); 430 begin_event.set_jniCriticalThreadCount(_current_jni_active_count); 431 begin_event.commit(); 432 } 433 } 434 435 // Wake up all threads, so they are ready to resume execution after the safepoint 436 // operation has been carried out 437 void SafepointSynchronize::end() { 438 EventSafepointEnd event; 439 int safepoint_id = safepoint_counter(); // Keep the odd counter as "id" 440 441 assert(Threads_lock->owned_by_self(), "must hold Threads_lock"); 442 assert((_safepoint_counter & 0x1) == 1, "must be odd"); 443 _safepoint_counter ++; 444 // memory fence isn't required here since an odd _safepoint_counter 445 // value can do no harm and a fence is issued below anyway. 446 447 DEBUG_ONLY(Thread* myThread = Thread::current();) 448 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint"); 449 450 if (PrintSafepointStatistics) { 451 end_statistics(os::javaTimeNanos()); 452 } 453 454 #ifdef ASSERT 455 // A pending_exception cannot be installed during a safepoint. The threads 456 // may install an async exception after they come back from a safepoint into 457 // pending_exception after they unblock. But that should happen later. 458 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) { 459 assert (!(cur->has_pending_exception() && 460 cur->safepoint_state()->is_at_poll_safepoint()), 461 "safepoint installed a pending exception"); 462 } 463 #endif // ASSERT 464 465 if (PageArmed) { 466 // Make polling safepoint aware 467 os::make_polling_page_readable(); 468 PageArmed = 0 ; 469 } 470 471 // Remove safepoint check from interpreter 472 Interpreter::ignore_safepoints(); 473 474 { 475 MutexLocker mu(Safepoint_lock); 476 477 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization"); 478 479 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method 480 // when they get restarted. 481 _state = _not_synchronized; 482 OrderAccess::fence(); 483 484 log_debug(safepoint)("Leaving safepoint region"); 485 486 // Start suspended threads 487 for(JavaThread *current = Threads::first(); current; current = current->next()) { 488 // A problem occurring on Solaris is when attempting to restart threads 489 // the first #cpus - 1 go well, but then the VMThread is preempted when we get 490 // to the next one (since it has been running the longest). We then have 491 // to wait for a cpu to become available before we can continue restarting 492 // threads. 493 // FIXME: This causes the performance of the VM to degrade when active and with 494 // large numbers of threads. Apparently this is due to the synchronous nature 495 // of suspending threads. 496 // 497 // TODO-FIXME: the comments above are vestigial and no longer apply. 498 // Furthermore, using solaris' schedctl in this particular context confers no benefit 499 if (VMThreadHintNoPreempt) { 500 os::hint_no_preempt(); 501 } 502 ThreadSafepointState* cur_state = current->safepoint_state(); 503 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint"); 504 cur_state->restart(); 505 assert(cur_state->is_running(), "safepoint state has not been reset"); 506 } 507 508 RuntimeService::record_safepoint_end(); 509 510 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads 511 // blocked in signal_thread_blocked 512 Threads_lock->unlock(); 513 514 } 515 #if INCLUDE_ALL_GCS 516 // If there are any concurrent GC threads resume them. 517 if (UseConcMarkSweepGC) { 518 ConcurrentMarkSweepThread::desynchronize(false); 519 } else if (UseG1GC) { 520 SuspendibleThreadSet::desynchronize(); 521 } 522 #endif // INCLUDE_ALL_GCS 523 // record this time so VMThread can keep track how much time has elapsed 524 // since last safepoint. 525 _end_of_last_safepoint = os::javaTimeMillis(); 526 527 if (event.should_commit()) { 528 event.set_safepointId(safepoint_id); 529 event.commit(); 530 } 531 } 532 533 bool SafepointSynchronize::is_cleanup_needed() { 534 // Need a safepoint if there are many monitors to deflate. 535 if (ObjectSynchronizer::is_cleanup_needed()) return true; 536 // Need a safepoint if some inline cache buffers is non-empty 537 if (!InlineCacheBuffer::is_empty()) return true; 538 return false; 539 } 540 541 static void event_safepoint_cleanup_task_commit(EventSafepointCleanupTask& event, const char* name) { 542 if (event.should_commit()) { 543 event.set_safepointId(SafepointSynchronize::safepoint_counter()); 544 event.set_name(name); 545 event.commit(); 546 } 547 } 548 549 class ParallelSPCleanupThreadClosure : public ThreadClosure { 550 private: 551 CodeBlobClosure* _nmethod_cl; 552 DeflateMonitorCounters* _counters; 553 554 public: 555 ParallelSPCleanupThreadClosure(DeflateMonitorCounters* counters) : 556 _counters(counters), 557 _nmethod_cl(NMethodSweeper::prepare_mark_active_nmethods()) {} 558 559 void do_thread(Thread* thread) { 560 ObjectSynchronizer::deflate_thread_local_monitors(thread, _counters); 561 if (_nmethod_cl != NULL && thread->is_Java_thread() && 562 ! thread->is_Code_cache_sweeper_thread()) { 563 JavaThread* jt = (JavaThread*) thread; 564 jt->nmethods_do(_nmethod_cl); 565 } 566 } 567 }; 568 569 class ParallelSPCleanupTask : public AbstractGangTask { 570 private: 571 SubTasksDone _subtasks; 572 ParallelSPCleanupThreadClosure _cleanup_threads_cl; 573 uint _num_workers; 574 DeflateMonitorCounters* _counters; 575 public: 576 ParallelSPCleanupTask(uint num_workers, DeflateMonitorCounters* counters) : 577 AbstractGangTask("Parallel Safepoint Cleanup"), 578 _cleanup_threads_cl(ParallelSPCleanupThreadClosure(counters)), 579 _num_workers(num_workers), 580 _subtasks(SubTasksDone(SafepointSynchronize::SAFEPOINT_CLEANUP_NUM_TASKS)), 581 _counters(counters) {} 582 583 void work(uint worker_id) { 584 // All threads deflate monitors and mark nmethods (if necessary). 585 Threads::parallel_java_threads_do(&_cleanup_threads_cl); 586 587 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_DEFLATE_MONITORS)) { 588 const char* name = "deflating idle monitors"; 589 EventSafepointCleanupTask event; 590 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup)); 591 ObjectSynchronizer::deflate_idle_monitors(_counters); 592 event_safepoint_cleanup_task_commit(event, name); 593 } 594 595 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_UPDATE_INLINE_CACHES)) { 596 const char* name = "updating inline caches"; 597 EventSafepointCleanupTask event; 598 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup)); 599 InlineCacheBuffer::update_inline_caches(); 600 event_safepoint_cleanup_task_commit(event, name); 601 } 602 603 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_COMPILATION_POLICY)) { 604 const char* name = "compilation policy safepoint handler"; 605 EventSafepointCleanupTask event; 606 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup)); 607 CompilationPolicy::policy()->do_safepoint_work(); 608 event_safepoint_cleanup_task_commit(event, name); 609 } 610 611 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_SYMBOL_TABLE_REHASH)) { 612 if (SymbolTable::needs_rehashing()) { 613 const char* name = "rehashing symbol table"; 614 EventSafepointCleanupTask event; 615 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup)); 616 SymbolTable::rehash_table(); 617 event_safepoint_cleanup_task_commit(event, name); 618 } 619 } 620 621 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_STRING_TABLE_REHASH)) { 622 if (StringTable::needs_rehashing()) { 623 const char* name = "rehashing string table"; 624 EventSafepointCleanupTask event; 625 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup)); 626 StringTable::rehash_table(); 627 event_safepoint_cleanup_task_commit(event, name); 628 } 629 } 630 631 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_CLD_PURGE)) { 632 // CMS delays purging the CLDG until the beginning of the next safepoint and to 633 // make sure concurrent sweep is done 634 const char* name = "purging class loader data graph"; 635 EventSafepointCleanupTask event; 636 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup)); 637 ClassLoaderDataGraph::purge_if_needed(); 638 event_safepoint_cleanup_task_commit(event, name); 639 } 640 _subtasks.all_tasks_completed(_num_workers); 641 } 642 }; 643 644 // Various cleaning tasks that should be done periodically at safepoints. 645 void SafepointSynchronize::do_cleanup_tasks() { 646 647 TraceTime timer("safepoint cleanup tasks", TRACETIME_LOG(Info, safepoint, cleanup)); 648 649 // Prepare for monitor deflation. 650 DeflateMonitorCounters deflate_counters; 651 ObjectSynchronizer::prepare_deflate_idle_monitors(&deflate_counters); 652 653 CollectedHeap* heap = Universe::heap(); 654 assert(heap != NULL, "heap not initialized yet?"); 655 WorkGang* cleanup_workers = heap->get_safepoint_workers(); 656 if (cleanup_workers != NULL) { 657 // Parallel cleanup using GC provided thread pool. 658 uint num_cleanup_workers = cleanup_workers->active_workers(); 659 ParallelSPCleanupTask cleanup(num_cleanup_workers, &deflate_counters); 660 StrongRootsScope srs(num_cleanup_workers); 661 cleanup_workers->run_task(&cleanup); 662 } else { 663 // Serial cleanup using VMThread. 664 ParallelSPCleanupTask cleanup(1, &deflate_counters); 665 StrongRootsScope srs(1); 666 cleanup.work(0); 667 } 668 669 // Finish monitor deflation. 670 ObjectSynchronizer::finish_deflate_idle_monitors(&deflate_counters); 671 } 672 673 674 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) { 675 switch(state) { 676 case _thread_in_native: 677 // native threads are safe if they have no java stack or have walkable stack 678 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable(); 679 680 // blocked threads should have already have walkable stack 681 case _thread_blocked: 682 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable"); 683 return true; 684 685 default: 686 return false; 687 } 688 } 689 690 691 // See if the thread is running inside a lazy critical native and 692 // update the thread critical count if so. Also set a suspend flag to 693 // cause the native wrapper to return into the JVM to do the unlock 694 // once the native finishes. 695 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) { 696 if (state == _thread_in_native && 697 thread->has_last_Java_frame() && 698 thread->frame_anchor()->walkable()) { 699 // This thread might be in a critical native nmethod so look at 700 // the top of the stack and increment the critical count if it 701 // is. 702 frame wrapper_frame = thread->last_frame(); 703 CodeBlob* stub_cb = wrapper_frame.cb(); 704 if (stub_cb != NULL && 705 stub_cb->is_nmethod() && 706 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) { 707 // A thread could potentially be in a critical native across 708 // more than one safepoint, so only update the critical state on 709 // the first one. When it returns it will perform the unlock. 710 if (!thread->do_critical_native_unlock()) { 711 #ifdef ASSERT 712 if (!thread->in_critical()) { 713 GCLocker::increment_debug_jni_lock_count(); 714 } 715 #endif 716 thread->enter_critical(); 717 // Make sure the native wrapper calls back on return to 718 // perform the needed critical unlock. 719 thread->set_critical_native_unlock(); 720 } 721 } 722 } 723 } 724 725 726 727 // ------------------------------------------------------------------------------------------------------- 728 // Implementation of Safepoint callback point 729 730 void SafepointSynchronize::block(JavaThread *thread) { 731 assert(thread != NULL, "thread must be set"); 732 assert(thread->is_Java_thread(), "not a Java thread"); 733 734 // Threads shouldn't block if they are in the middle of printing, but... 735 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id()); 736 737 // Only bail from the block() call if the thread is gone from the 738 // thread list; starting to exit should still block. 739 if (thread->is_terminated()) { 740 // block current thread if we come here from native code when VM is gone 741 thread->block_if_vm_exited(); 742 743 // otherwise do nothing 744 return; 745 } 746 747 JavaThreadState state = thread->thread_state(); 748 thread->frame_anchor()->make_walkable(thread); 749 750 // Check that we have a valid thread_state at this point 751 switch(state) { 752 case _thread_in_vm_trans: 753 case _thread_in_Java: // From compiled code 754 755 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case, 756 // we pretend we are still in the VM. 757 thread->set_thread_state(_thread_in_vm); 758 759 if (is_synchronizing()) { 760 Atomic::inc (&TryingToBlock) ; 761 } 762 763 // We will always be holding the Safepoint_lock when we are examine the state 764 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and 765 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code 766 Safepoint_lock->lock_without_safepoint_check(); 767 if (is_synchronizing()) { 768 // Decrement the number of threads to wait for and signal vm thread 769 assert(_waiting_to_block > 0, "sanity check"); 770 _waiting_to_block--; 771 thread->safepoint_state()->set_has_called_back(true); 772 773 DEBUG_ONLY(thread->set_visited_for_critical_count(true)); 774 if (thread->in_critical()) { 775 // Notice that this thread is in a critical section 776 increment_jni_active_count(); 777 } 778 779 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread 780 if (_waiting_to_block == 0) { 781 Safepoint_lock->notify_all(); 782 } 783 } 784 785 // We transition the thread to state _thread_blocked here, but 786 // we can't do our usual check for external suspension and then 787 // self-suspend after the lock_without_safepoint_check() call 788 // below because we are often called during transitions while 789 // we hold different locks. That would leave us suspended while 790 // holding a resource which results in deadlocks. 791 thread->set_thread_state(_thread_blocked); 792 Safepoint_lock->unlock(); 793 794 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during 795 // the entire safepoint, the threads will all line up here during the safepoint. 796 Threads_lock->lock_without_safepoint_check(); 797 // restore original state. This is important if the thread comes from compiled code, so it 798 // will continue to execute with the _thread_in_Java state. 799 thread->set_thread_state(state); 800 Threads_lock->unlock(); 801 break; 802 803 case _thread_in_native_trans: 804 case _thread_blocked_trans: 805 case _thread_new_trans: 806 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) { 807 thread->print_thread_state(); 808 fatal("Deadlock in safepoint code. " 809 "Should have called back to the VM before blocking."); 810 } 811 812 // We transition the thread to state _thread_blocked here, but 813 // we can't do our usual check for external suspension and then 814 // self-suspend after the lock_without_safepoint_check() call 815 // below because we are often called during transitions while 816 // we hold different locks. That would leave us suspended while 817 // holding a resource which results in deadlocks. 818 thread->set_thread_state(_thread_blocked); 819 820 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence, 821 // the safepoint code might still be waiting for it to block. We need to change the state here, 822 // so it can see that it is at a safepoint. 823 824 // Block until the safepoint operation is completed. 825 Threads_lock->lock_without_safepoint_check(); 826 827 // Restore state 828 thread->set_thread_state(state); 829 830 Threads_lock->unlock(); 831 break; 832 833 default: 834 fatal("Illegal threadstate encountered: %d", state); 835 } 836 837 // Check for pending. async. exceptions or suspends - except if the 838 // thread was blocked inside the VM. has_special_runtime_exit_condition() 839 // is called last since it grabs a lock and we only want to do that when 840 // we must. 841 // 842 // Note: we never deliver an async exception at a polling point as the 843 // compiler may not have an exception handler for it. The polling 844 // code will notice the async and deoptimize and the exception will 845 // be delivered. (Polling at a return point is ok though). Sure is 846 // a lot of bother for a deprecated feature... 847 // 848 // We don't deliver an async exception if the thread state is 849 // _thread_in_native_trans so JNI functions won't be called with 850 // a surprising pending exception. If the thread state is going back to java, 851 // async exception is checked in check_special_condition_for_native_trans(). 852 853 if (state != _thread_blocked_trans && 854 state != _thread_in_vm_trans && 855 thread->has_special_runtime_exit_condition()) { 856 thread->handle_special_runtime_exit_condition( 857 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans)); 858 } 859 } 860 861 // ------------------------------------------------------------------------------------------------------ 862 // Exception handlers 863 864 865 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) { 866 assert(thread->is_Java_thread(), "polling reference encountered by VM thread"); 867 assert(thread->thread_state() == _thread_in_Java, "should come from Java code"); 868 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization"); 869 870 if (ShowSafepointMsgs) { 871 tty->print("handle_polling_page_exception: "); 872 } 873 874 if (PrintSafepointStatistics) { 875 inc_page_trap_count(); 876 } 877 878 ThreadSafepointState* state = thread->safepoint_state(); 879 880 state->handle_polling_page_exception(); 881 } 882 883 884 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) { 885 if (!timeout_error_printed) { 886 timeout_error_printed = true; 887 // Print out the thread info which didn't reach the safepoint for debugging 888 // purposes (useful when there are lots of threads in the debugger). 889 tty->cr(); 890 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:"); 891 if (reason == _spinning_timeout) { 892 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint."); 893 } else if (reason == _blocking_timeout) { 894 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop."); 895 } 896 897 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:"); 898 ThreadSafepointState *cur_state; 899 ResourceMark rm; 900 for(JavaThread *cur_thread = Threads::first(); cur_thread; 901 cur_thread = cur_thread->next()) { 902 cur_state = cur_thread->safepoint_state(); 903 904 if (cur_thread->thread_state() != _thread_blocked && 905 ((reason == _spinning_timeout && cur_state->is_running()) || 906 (reason == _blocking_timeout && !cur_state->has_called_back()))) { 907 tty->print("# "); 908 cur_thread->print(); 909 tty->cr(); 910 } 911 } 912 tty->print_cr("# SafepointSynchronize::begin: (End of list)"); 913 } 914 915 // To debug the long safepoint, specify both DieOnSafepointTimeout & 916 // ShowMessageBoxOnError. 917 if (DieOnSafepointTimeout) { 918 fatal("Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.", 919 SafepointTimeoutDelay, VMThread::vm_safepoint_description()); 920 } 921 } 922 923 924 // ------------------------------------------------------------------------------------------------------- 925 // Implementation of ThreadSafepointState 926 927 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) { 928 _thread = thread; 929 _type = _running; 930 _has_called_back = false; 931 _at_poll_safepoint = false; 932 } 933 934 void ThreadSafepointState::create(JavaThread *thread) { 935 ThreadSafepointState *state = new ThreadSafepointState(thread); 936 thread->set_safepoint_state(state); 937 } 938 939 void ThreadSafepointState::destroy(JavaThread *thread) { 940 if (thread->safepoint_state()) { 941 delete(thread->safepoint_state()); 942 thread->set_safepoint_state(NULL); 943 } 944 } 945 946 void ThreadSafepointState::examine_state_of_thread() { 947 assert(is_running(), "better be running or just have hit safepoint poll"); 948 949 JavaThreadState state = _thread->thread_state(); 950 951 // Save the state at the start of safepoint processing. 952 _orig_thread_state = state; 953 954 // Check for a thread that is suspended. Note that thread resume tries 955 // to grab the Threads_lock which we own here, so a thread cannot be 956 // resumed during safepoint synchronization. 957 958 // We check to see if this thread is suspended without locking to 959 // avoid deadlocking with a third thread that is waiting for this 960 // thread to be suspended. The third thread can notice the safepoint 961 // that we're trying to start at the beginning of its SR_lock->wait() 962 // call. If that happens, then the third thread will block on the 963 // safepoint while still holding the underlying SR_lock. We won't be 964 // able to get the SR_lock and we'll deadlock. 965 // 966 // We don't need to grab the SR_lock here for two reasons: 967 // 1) The suspend flags are both volatile and are set with an 968 // Atomic::cmpxchg() call so we should see the suspended 969 // state right away. 970 // 2) We're being called from the safepoint polling loop; if 971 // we don't see the suspended state on this iteration, then 972 // we'll come around again. 973 // 974 bool is_suspended = _thread->is_ext_suspended(); 975 if (is_suspended) { 976 roll_forward(_at_safepoint); 977 return; 978 } 979 980 // Some JavaThread states have an initial safepoint state of 981 // running, but are actually at a safepoint. We will happily 982 // agree and update the safepoint state here. 983 if (SafepointSynchronize::safepoint_safe(_thread, state)) { 984 SafepointSynchronize::check_for_lazy_critical_native(_thread, state); 985 roll_forward(_at_safepoint); 986 return; 987 } 988 989 if (state == _thread_in_vm) { 990 roll_forward(_call_back); 991 return; 992 } 993 994 // All other thread states will continue to run until they 995 // transition and self-block in state _blocked 996 // Safepoint polling in compiled code causes the Java threads to do the same. 997 // Note: new threads may require a malloc so they must be allowed to finish 998 999 assert(is_running(), "examine_state_of_thread on non-running thread"); 1000 return; 1001 } 1002 1003 // Returns true is thread could not be rolled forward at present position. 1004 void ThreadSafepointState::roll_forward(suspend_type type) { 1005 _type = type; 1006 1007 switch(_type) { 1008 case _at_safepoint: 1009 SafepointSynchronize::signal_thread_at_safepoint(); 1010 DEBUG_ONLY(_thread->set_visited_for_critical_count(true)); 1011 if (_thread->in_critical()) { 1012 // Notice that this thread is in a critical section 1013 SafepointSynchronize::increment_jni_active_count(); 1014 } 1015 break; 1016 1017 case _call_back: 1018 set_has_called_back(false); 1019 break; 1020 1021 case _running: 1022 default: 1023 ShouldNotReachHere(); 1024 } 1025 } 1026 1027 void ThreadSafepointState::restart() { 1028 switch(type()) { 1029 case _at_safepoint: 1030 case _call_back: 1031 break; 1032 1033 case _running: 1034 default: 1035 tty->print_cr("restart thread " INTPTR_FORMAT " with state %d", 1036 p2i(_thread), _type); 1037 _thread->print(); 1038 ShouldNotReachHere(); 1039 } 1040 _type = _running; 1041 set_has_called_back(false); 1042 } 1043 1044 1045 void ThreadSafepointState::print_on(outputStream *st) const { 1046 const char *s = NULL; 1047 1048 switch(_type) { 1049 case _running : s = "_running"; break; 1050 case _at_safepoint : s = "_at_safepoint"; break; 1051 case _call_back : s = "_call_back"; break; 1052 default: 1053 ShouldNotReachHere(); 1054 } 1055 1056 st->print_cr("Thread: " INTPTR_FORMAT 1057 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d", 1058 p2i(_thread), _thread->osthread()->thread_id(), s, _has_called_back, 1059 _at_poll_safepoint); 1060 1061 _thread->print_thread_state_on(st); 1062 } 1063 1064 // --------------------------------------------------------------------------------------------------------------------- 1065 1066 // Block the thread at the safepoint poll or poll return. 1067 void ThreadSafepointState::handle_polling_page_exception() { 1068 1069 // Check state. block() will set thread state to thread_in_vm which will 1070 // cause the safepoint state _type to become _call_back. 1071 assert(type() == ThreadSafepointState::_running, 1072 "polling page exception on thread not running state"); 1073 1074 // Step 1: Find the nmethod from the return address 1075 if (ShowSafepointMsgs && Verbose) { 1076 tty->print_cr("Polling page exception at " INTPTR_FORMAT, p2i(thread()->saved_exception_pc())); 1077 } 1078 address real_return_addr = thread()->saved_exception_pc(); 1079 1080 CodeBlob *cb = CodeCache::find_blob(real_return_addr); 1081 assert(cb != NULL && cb->is_compiled(), "return address should be in nmethod"); 1082 CompiledMethod* nm = (CompiledMethod*)cb; 1083 1084 // Find frame of caller 1085 frame stub_fr = thread()->last_frame(); 1086 CodeBlob* stub_cb = stub_fr.cb(); 1087 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub"); 1088 RegisterMap map(thread(), true); 1089 frame caller_fr = stub_fr.sender(&map); 1090 1091 // Should only be poll_return or poll 1092 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" ); 1093 1094 // This is a poll immediately before a return. The exception handling code 1095 // has already had the effect of causing the return to occur, so the execution 1096 // will continue immediately after the call. In addition, the oopmap at the 1097 // return point does not mark the return value as an oop (if it is), so 1098 // it needs a handle here to be updated. 1099 if( nm->is_at_poll_return(real_return_addr) ) { 1100 ResourceMark rm; 1101 // See if return type is an oop. 1102 Method* method = nm->method(); 1103 bool return_oop = method->is_returning_oop(); 1104 1105 GrowableArray<Handle> return_values; 1106 ValueKlass* vk = NULL; 1107 if (method->is_returning_vt() && ValueTypeReturnedAsFields) { 1108 // Check if value type is returned as fields 1109 vk = ValueKlass::returned_value_klass(map); 1110 if (vk != NULL) { 1111 // We're at a safepoint at the return of a method that returns 1112 // multiple values. We must make sure we preserve the oop values 1113 // across the safepoint. 1114 assert(vk == method->returned_value_type(thread()), "bad value klass"); 1115 vk->save_oop_fields(map, return_values); 1116 return_oop = false; 1117 } 1118 } 1119 1120 if (return_oop) { 1121 // The oop result has been saved on the stack together with all 1122 // the other registers. In order to preserve it over GCs we need 1123 // to keep it in a handle. 1124 oop result = caller_fr.saved_oop_result(&map); 1125 assert(oopDesc::is_oop_or_null(result), "must be oop"); 1126 return_values.push(Handle(thread(), result)); 1127 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer"); 1128 } 1129 1130 // Block the thread 1131 SafepointSynchronize::block(thread()); 1132 1133 // restore oop result, if any 1134 if (return_oop) { 1135 assert(return_values.length() == 1, "only one return value"); 1136 caller_fr.set_saved_oop_result(&map, return_values.pop()()); 1137 } else if (vk != NULL) { 1138 vk->restore_oop_results(map, return_values); 1139 } 1140 } 1141 1142 // This is a safepoint poll. Verify the return address and block. 1143 else { 1144 set_at_poll_safepoint(true); 1145 1146 // verify the blob built the "return address" correctly 1147 assert(real_return_addr == caller_fr.pc(), "must match"); 1148 1149 // Block the thread 1150 SafepointSynchronize::block(thread()); 1151 set_at_poll_safepoint(false); 1152 1153 // If we have a pending async exception deoptimize the frame 1154 // as otherwise we may never deliver it. 1155 if (thread()->has_async_condition()) { 1156 ThreadInVMfromJavaNoAsyncException __tiv(thread()); 1157 Deoptimization::deoptimize_frame(thread(), caller_fr.id()); 1158 } 1159 1160 // If an exception has been installed we must check for a pending deoptimization 1161 // Deoptimize frame if exception has been thrown. 1162 1163 if (thread()->has_pending_exception() ) { 1164 RegisterMap map(thread(), true); 1165 frame caller_fr = stub_fr.sender(&map); 1166 if (caller_fr.is_deoptimized_frame()) { 1167 // The exception patch will destroy registers that are still 1168 // live and will be needed during deoptimization. Defer the 1169 // Async exception should have deferred the exception until the 1170 // next safepoint which will be detected when we get into 1171 // the interpreter so if we have an exception now things 1172 // are messed up. 1173 1174 fatal("Exception installed and deoptimization is pending"); 1175 } 1176 } 1177 } 1178 } 1179 1180 1181 // 1182 // Statistics & Instrumentations 1183 // 1184 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL; 1185 jlong SafepointSynchronize::_safepoint_begin_time = 0; 1186 int SafepointSynchronize::_cur_stat_index = 0; 1187 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating]; 1188 julong SafepointSynchronize::_coalesced_vmop_count = 0; 1189 jlong SafepointSynchronize::_max_sync_time = 0; 1190 jlong SafepointSynchronize::_max_vmop_time = 0; 1191 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f; 1192 1193 static jlong cleanup_end_time = 0; 1194 static bool need_to_track_page_armed_status = false; 1195 static bool init_done = false; 1196 1197 // Helper method to print the header. 1198 static void print_header() { 1199 // The number of spaces is significant here, and should match the format 1200 // specifiers in print_statistics(). 1201 1202 tty->print(" vmop " 1203 "[ threads: total initially_running wait_to_block ]" 1204 "[ time: spin block sync cleanup vmop ] "); 1205 1206 // no page armed status printed out if it is always armed. 1207 if (need_to_track_page_armed_status) { 1208 tty->print("page_armed "); 1209 } 1210 1211 tty->print_cr("page_trap_count"); 1212 } 1213 1214 void SafepointSynchronize::deferred_initialize_stat() { 1215 if (init_done) return; 1216 1217 // If PrintSafepointStatisticsTimeout is specified, the statistics data will 1218 // be printed right away, in which case, _safepoint_stats will regress to 1219 // a single element array. Otherwise, it is a circular ring buffer with default 1220 // size of PrintSafepointStatisticsCount. 1221 int stats_array_size; 1222 if (PrintSafepointStatisticsTimeout > 0) { 1223 stats_array_size = 1; 1224 PrintSafepointStatistics = true; 1225 } else { 1226 stats_array_size = PrintSafepointStatisticsCount; 1227 } 1228 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size 1229 * sizeof(SafepointStats), mtInternal); 1230 guarantee(_safepoint_stats != NULL, 1231 "not enough memory for safepoint instrumentation data"); 1232 1233 if (DeferPollingPageLoopCount >= 0) { 1234 need_to_track_page_armed_status = true; 1235 } 1236 init_done = true; 1237 } 1238 1239 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) { 1240 assert(init_done, "safepoint statistics array hasn't been initialized"); 1241 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1242 1243 spstat->_time_stamp = _ts_of_current_safepoint; 1244 1245 VM_Operation *op = VMThread::vm_operation(); 1246 spstat->_vmop_type = (op != NULL ? op->type() : -1); 1247 if (op != NULL) { 1248 _safepoint_reasons[spstat->_vmop_type]++; 1249 } 1250 1251 spstat->_nof_total_threads = nof_threads; 1252 spstat->_nof_initial_running_threads = nof_running; 1253 spstat->_nof_threads_hit_page_trap = 0; 1254 1255 // Records the start time of spinning. The real time spent on spinning 1256 // will be adjusted when spin is done. Same trick is applied for time 1257 // spent on waiting for threads to block. 1258 if (nof_running != 0) { 1259 spstat->_time_to_spin = os::javaTimeNanos(); 1260 } else { 1261 spstat->_time_to_spin = 0; 1262 } 1263 } 1264 1265 void SafepointSynchronize::update_statistics_on_spin_end() { 1266 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1267 1268 jlong cur_time = os::javaTimeNanos(); 1269 1270 spstat->_nof_threads_wait_to_block = _waiting_to_block; 1271 if (spstat->_nof_initial_running_threads != 0) { 1272 spstat->_time_to_spin = cur_time - spstat->_time_to_spin; 1273 } 1274 1275 if (need_to_track_page_armed_status) { 1276 spstat->_page_armed = (PageArmed == 1); 1277 } 1278 1279 // Records the start time of waiting for to block. Updated when block is done. 1280 if (_waiting_to_block != 0) { 1281 spstat->_time_to_wait_to_block = cur_time; 1282 } else { 1283 spstat->_time_to_wait_to_block = 0; 1284 } 1285 } 1286 1287 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) { 1288 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1289 1290 if (spstat->_nof_threads_wait_to_block != 0) { 1291 spstat->_time_to_wait_to_block = end_time - 1292 spstat->_time_to_wait_to_block; 1293 } 1294 1295 // Records the end time of sync which will be used to calculate the total 1296 // vm operation time. Again, the real time spending in syncing will be deducted 1297 // from the start of the sync time later when end_statistics is called. 1298 spstat->_time_to_sync = end_time - _safepoint_begin_time; 1299 if (spstat->_time_to_sync > _max_sync_time) { 1300 _max_sync_time = spstat->_time_to_sync; 1301 } 1302 1303 spstat->_time_to_do_cleanups = end_time; 1304 } 1305 1306 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) { 1307 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1308 1309 // Record how long spent in cleanup tasks. 1310 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups; 1311 1312 cleanup_end_time = end_time; 1313 } 1314 1315 void SafepointSynchronize::end_statistics(jlong vmop_end_time) { 1316 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1317 1318 // Update the vm operation time. 1319 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time; 1320 if (spstat->_time_to_exec_vmop > _max_vmop_time) { 1321 _max_vmop_time = spstat->_time_to_exec_vmop; 1322 } 1323 // Only the sync time longer than the specified 1324 // PrintSafepointStatisticsTimeout will be printed out right away. 1325 // By default, it is -1 meaning all samples will be put into the list. 1326 if ( PrintSafepointStatisticsTimeout > 0) { 1327 if (spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) { 1328 print_statistics(); 1329 } 1330 } else { 1331 // The safepoint statistics will be printed out when the _safepoin_stats 1332 // array fills up. 1333 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) { 1334 print_statistics(); 1335 _cur_stat_index = 0; 1336 } else { 1337 _cur_stat_index++; 1338 } 1339 } 1340 } 1341 1342 void SafepointSynchronize::print_statistics() { 1343 for (int index = 0; index <= _cur_stat_index; index++) { 1344 if (index % 30 == 0) { 1345 print_header(); 1346 } 1347 SafepointStats* sstats = &_safepoint_stats[index]; 1348 tty->print("%8.3f: ", sstats->_time_stamp); 1349 tty->print("%-30s [ " 1350 INT32_FORMAT_W(8) " " INT32_FORMAT_W(17) " " INT32_FORMAT_W(13) " " 1351 "]", 1352 (sstats->_vmop_type == -1 ? "no vm operation" : VM_Operation::name(sstats->_vmop_type)), 1353 sstats->_nof_total_threads, 1354 sstats->_nof_initial_running_threads, 1355 sstats->_nof_threads_wait_to_block); 1356 // "/ MICROUNITS " is to convert the unit from nanos to millis. 1357 tty->print("[ " 1358 INT64_FORMAT_W(7) " " INT64_FORMAT_W(7) " " 1359 INT64_FORMAT_W(7) " " INT64_FORMAT_W(7) " " 1360 INT64_FORMAT_W(7) " ] ", 1361 (int64_t)(sstats->_time_to_spin / MICROUNITS), 1362 (int64_t)(sstats->_time_to_wait_to_block / MICROUNITS), 1363 (int64_t)(sstats->_time_to_sync / MICROUNITS), 1364 (int64_t)(sstats->_time_to_do_cleanups / MICROUNITS), 1365 (int64_t)(sstats->_time_to_exec_vmop / MICROUNITS)); 1366 1367 if (need_to_track_page_armed_status) { 1368 tty->print(INT32_FORMAT_W(10) " ", sstats->_page_armed); 1369 } 1370 tty->print_cr(INT32_FORMAT_W(15) " ", sstats->_nof_threads_hit_page_trap); 1371 } 1372 } 1373 1374 // This method will be called when VM exits. It will first call 1375 // print_statistics to print out the rest of the sampling. Then 1376 // it tries to summarize the sampling. 1377 void SafepointSynchronize::print_stat_on_exit() { 1378 if (_safepoint_stats == NULL) return; 1379 1380 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1381 1382 // During VM exit, end_statistics may not get called and in that 1383 // case, if the sync time is less than PrintSafepointStatisticsTimeout, 1384 // don't print it out. 1385 // Approximate the vm op time. 1386 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop = 1387 os::javaTimeNanos() - cleanup_end_time; 1388 1389 if ( PrintSafepointStatisticsTimeout < 0 || 1390 spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) { 1391 print_statistics(); 1392 } 1393 tty->cr(); 1394 1395 // Print out polling page sampling status. 1396 if (!need_to_track_page_armed_status) { 1397 tty->print_cr("Polling page always armed"); 1398 } else { 1399 tty->print_cr("Defer polling page loop count = " INTX_FORMAT "\n", 1400 DeferPollingPageLoopCount); 1401 } 1402 1403 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) { 1404 if (_safepoint_reasons[index] != 0) { 1405 tty->print_cr("%-26s" UINT64_FORMAT_W(10), VM_Operation::name(index), 1406 _safepoint_reasons[index]); 1407 } 1408 } 1409 1410 tty->print_cr(UINT64_FORMAT_W(5) " VM operations coalesced during safepoint", 1411 _coalesced_vmop_count); 1412 tty->print_cr("Maximum sync time " INT64_FORMAT_W(5) " ms", 1413 (int64_t)(_max_sync_time / MICROUNITS)); 1414 tty->print_cr("Maximum vm operation time (except for Exit VM operation) " 1415 INT64_FORMAT_W(5) " ms", 1416 (int64_t)(_max_vmop_time / MICROUNITS)); 1417 } 1418 1419 // ------------------------------------------------------------------------------------------------ 1420 // Non-product code 1421 1422 #ifndef PRODUCT 1423 1424 void SafepointSynchronize::print_state() { 1425 if (_state == _not_synchronized) { 1426 tty->print_cr("not synchronized"); 1427 } else if (_state == _synchronizing || _state == _synchronized) { 1428 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" : 1429 "synchronized"); 1430 1431 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) { 1432 cur->safepoint_state()->print(); 1433 } 1434 } 1435 } 1436 1437 void SafepointSynchronize::safepoint_msg(const char* format, ...) { 1438 if (ShowSafepointMsgs) { 1439 va_list ap; 1440 va_start(ap, format); 1441 tty->vprint_cr(format, ap); 1442 va_end(ap); 1443 } 1444 } 1445 1446 #endif // !PRODUCT