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