1 /* 2 * Copyright (c) 1997, 2016, 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 "interpreter/interpreter.hpp" 37 #include "logging/log.hpp" 38 #include "memory/resourceArea.hpp" 39 #include "memory/universe.inline.hpp" 40 #include "oops/oop.inline.hpp" 41 #include "oops/symbol.hpp" 42 #include "runtime/atomic.hpp" 43 #include "runtime/compilationPolicy.hpp" 44 #include "runtime/deoptimization.hpp" 45 #include "runtime/frame.inline.hpp" 46 #include "runtime/interfaceSupport.hpp" 47 #include "runtime/mutexLocker.hpp" 48 #include "runtime/orderAccess.inline.hpp" 49 #include "runtime/osThread.hpp" 50 #include "runtime/safepoint.hpp" 51 #include "runtime/signature.hpp" 52 #include "runtime/stubCodeGenerator.hpp" 53 #include "runtime/stubRoutines.hpp" 54 #include "runtime/sweeper.hpp" 55 #include "runtime/synchronizer.hpp" 56 #include "runtime/thread.inline.hpp" 57 #include "runtime/timerTrace.hpp" 58 #include "services/runtimeService.hpp" 59 #include "trace/tracing.hpp" 60 #include "trace/traceMacros.hpp" 61 #include "utilities/events.hpp" 62 #include "utilities/macros.hpp" 63 #if INCLUDE_ALL_GCS 64 #include "gc/cms/concurrentMarkSweepThread.hpp" 65 #include "gc/g1/suspendibleThreadSet.hpp" 66 #endif // INCLUDE_ALL_GCS 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 #if INCLUDE_ALL_GCS 95 if (UseConcMarkSweepGC) { 96 // In the future we should investigate whether CMS can use the 97 // more-general mechanism below. DLD (01/05). 98 ConcurrentMarkSweepThread::synchronize(false); 99 } else if (UseG1GC) { 100 SuspendibleThreadSet::synchronize(); 101 } 102 #endif // INCLUDE_ALL_GCS 103 104 // By getting the Threads_lock, we assure that no threads are about to start or 105 // exit. It is released again in SafepointSynchronize::end(). 106 Threads_lock->lock(); 107 108 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state"); 109 110 int nof_threads = Threads::number_of_threads(); 111 112 log_debug(safepoint)("Safepoint synchronization initiated. (%d)", nof_threads); 113 114 RuntimeService::record_safepoint_begin(); 115 116 MutexLocker mu(Safepoint_lock); 117 118 // Reset the count of active JNI critical threads 119 _current_jni_active_count = 0; 120 121 // Set number of threads to wait for, before we initiate the callbacks 122 _waiting_to_block = nof_threads; 123 TryingToBlock = 0 ; 124 int still_running = nof_threads; 125 126 // Save the starting time, so that it can be compared to see if this has taken 127 // too long to complete. 128 jlong safepoint_limit_time = 0; 129 timeout_error_printed = false; 130 131 // PrintSafepointStatisticsTimeout can be specified separately. When 132 // specified, PrintSafepointStatistics will be set to true in 133 // deferred_initialize_stat method. The initialization has to be done 134 // early enough to avoid any races. See bug 6880029 for details. 135 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) { 136 deferred_initialize_stat(); 137 } 138 139 // Begin the process of bringing the system to a safepoint. 140 // Java threads can be in several different states and are 141 // stopped by different mechanisms: 142 // 143 // 1. Running interpreted 144 // The interpreter dispatch table is changed to force it to 145 // check for a safepoint condition between bytecodes. 146 // 2. Running in native code 147 // When returning from the native code, a Java thread must check 148 // the safepoint _state to see if we must block. If the 149 // VM thread sees a Java thread in native, it does 150 // not wait for this thread to block. The order of the memory 151 // writes and reads of both the safepoint state and the Java 152 // threads state is critical. In order to guarantee that the 153 // memory writes are serialized with respect to each other, 154 // the VM thread issues a memory barrier instruction 155 // (on MP systems). In order to avoid the overhead of issuing 156 // a memory barrier for each Java thread making native calls, each Java 157 // thread performs a write to a single memory page after changing 158 // the thread state. The VM thread performs a sequence of 159 // mprotect OS calls which forces all previous writes from all 160 // Java threads to be serialized. This is done in the 161 // os::serialize_thread_states() call. This has proven to be 162 // much more efficient than executing a membar instruction 163 // on every call to native code. 164 // 3. Running compiled Code 165 // Compiled code reads a global (Safepoint Polling) page that 166 // is set to fault if we are trying to get to a safepoint. 167 // 4. Blocked 168 // A thread which is blocked will not be allowed to return from the 169 // block condition until the safepoint operation is complete. 170 // 5. In VM or Transitioning between states 171 // If a Java thread is currently running in the VM or transitioning 172 // between states, the safepointing code will wait for the thread to 173 // block itself when it attempts transitions to a new state. 174 // 175 { 176 EventSafepointStateSynchronization sync_event; 177 int initial_running = 0; 178 179 _state = _synchronizing; 180 OrderAccess::fence(); 181 182 // Flush all thread states to memory 183 if (!UseMembar) { 184 os::serialize_thread_states(); 185 } 186 187 // Make interpreter safepoint aware 188 Interpreter::notice_safepoints(); 189 190 if (DeferPollingPageLoopCount < 0) { 191 // Make polling safepoint aware 192 guarantee (PageArmed == 0, "invariant") ; 193 PageArmed = 1 ; 194 os::make_polling_page_unreadable(); 195 } 196 197 // Consider using active_processor_count() ... but that call is expensive. 198 int ncpus = os::processor_count() ; 199 200 #ifdef ASSERT 201 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) { 202 assert(cur->safepoint_state()->is_running(), "Illegal initial state"); 203 // Clear the visited flag to ensure that the critical counts are collected properly. 204 cur->set_visited_for_critical_count(false); 205 } 206 #endif // ASSERT 207 208 if (SafepointTimeout) 209 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS; 210 211 // Iterate through all threads until it have been determined how to stop them all at a safepoint 212 unsigned int iterations = 0; 213 int steps = 0 ; 214 while(still_running > 0) { 215 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) { 216 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended"); 217 ThreadSafepointState *cur_state = cur->safepoint_state(); 218 if (cur_state->is_running()) { 219 cur_state->examine_state_of_thread(); 220 if (!cur_state->is_running()) { 221 still_running--; 222 // consider adjusting steps downward: 223 // steps = 0 224 // steps -= NNN 225 // steps >>= 1 226 // steps = MIN(steps, 2000-100) 227 // if (iterations != 0) steps -= NNN 228 } 229 if (log_is_enabled(Trace, safepoint)) { 230 ResourceMark rm; 231 cur_state->print_on(Log(safepoint)::trace_stream()); 232 } 233 } 234 } 235 236 if (iterations == 0) { 237 initial_running = still_running; 238 if (PrintSafepointStatistics) { 239 begin_statistics(nof_threads, still_running); 240 } 241 } 242 243 if (still_running > 0) { 244 // Check for if it takes to long 245 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) { 246 print_safepoint_timeout(_spinning_timeout); 247 } 248 249 // Spin to avoid context switching. 250 // There's a tension between allowing the mutators to run (and rendezvous) 251 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that 252 // a mutator might otherwise use profitably to reach a safepoint. Excessive 253 // spinning by the VM thread on a saturated system can increase rendezvous latency. 254 // Blocking or yielding incur their own penalties in the form of context switching 255 // and the resultant loss of $ residency. 256 // 257 // Further complicating matters is that yield() does not work as naively expected 258 // on many platforms -- yield() does not guarantee that any other ready threads 259 // will run. As such we revert to naked_short_sleep() after some number of iterations. 260 // nakes_short_sleep() is implemented as a short unconditional sleep. 261 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping 262 // can actually increase the time it takes the VM thread to detect that a system-wide 263 // stop-the-world safepoint has been reached. In a pathological scenario such as that 264 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe. 265 // In that case the mutators will be stalled waiting for the safepoint to complete and the 266 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread 267 // will eventually wake up and detect that all mutators are safe, at which point 268 // we'll again make progress. 269 // 270 // Beware too that that the VMThread typically runs at elevated priority. 271 // Its default priority is higher than the default mutator priority. 272 // Obviously, this complicates spinning. 273 // 274 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0). 275 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will. 276 // 277 // See the comments in synchronizer.cpp for additional remarks on spinning. 278 // 279 // In the future we might: 280 // 1. Modify the safepoint scheme to avoid potentially unbounded spinning. 281 // This is tricky as the path used by a thread exiting the JVM (say on 282 // on JNI call-out) simply stores into its state field. The burden 283 // is placed on the VM thread, which must poll (spin). 284 // 2. Find something useful to do while spinning. If the safepoint is GC-related 285 // we might aggressively scan the stacks of threads that are already safe. 286 // 3. Use Solaris schedctl to examine the state of the still-running mutators. 287 // If all the mutators are ONPROC there's no reason to sleep or yield. 288 // 4. YieldTo() any still-running mutators that are ready but OFFPROC. 289 // 5. Check system saturation. If the system is not fully saturated then 290 // simply spin and avoid sleep/yield. 291 // 6. As still-running mutators rendezvous they could unpark the sleeping 292 // VMthread. This works well for still-running mutators that become 293 // safe. The VMthread must still poll for mutators that call-out. 294 // 7. Drive the policy on time-since-begin instead of iterations. 295 // 8. Consider making the spin duration a function of the # of CPUs: 296 // Spin = (((ncpus-1) * M) + K) + F(still_running) 297 // Alternately, instead of counting iterations of the outer loop 298 // we could count the # of threads visited in the inner loop, above. 299 // 9. On windows consider using the return value from SwitchThreadTo() 300 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions. 301 302 if (int(iterations) == DeferPollingPageLoopCount) { 303 guarantee (PageArmed == 0, "invariant") ; 304 PageArmed = 1 ; 305 os::make_polling_page_unreadable(); 306 } 307 308 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or 309 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus) 310 ++steps ; 311 if (ncpus > 1 && steps < SafepointSpinBeforeYield) { 312 SpinPause() ; // MP-Polite spin 313 } else 314 if (steps < DeferThrSuspendLoopCount) { 315 os::naked_yield() ; 316 } else { 317 os::naked_short_sleep(1); 318 } 319 320 iterations ++ ; 321 } 322 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long"); 323 } 324 assert(still_running == 0, "sanity check"); 325 326 if (PrintSafepointStatistics) { 327 update_statistics_on_spin_end(); 328 } 329 330 if (sync_event.should_commit()) { 331 sync_event.set_safepointId(safepoint_counter()); 332 sync_event.set_initialThreadCount(initial_running); 333 sync_event.set_runningThreadCount(_waiting_to_block); 334 sync_event.set_iterations(iterations); 335 sync_event.commit(); 336 } 337 } //EventSafepointStateSync 338 339 // wait until all threads are stopped 340 { 341 EventSafepointWaitBlocked wait_blocked_event; 342 int initial_waiting_to_block = _waiting_to_block; 343 344 while (_waiting_to_block > 0) { 345 log_debug(safepoint)("Waiting for %d thread(s) to block", _waiting_to_block); 346 if (!SafepointTimeout || timeout_error_printed) { 347 Safepoint_lock->wait(true); // true, means with no safepoint checks 348 } else { 349 // Compute remaining time 350 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos(); 351 352 // If there is no remaining time, then there is an error 353 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) { 354 print_safepoint_timeout(_blocking_timeout); 355 } 356 } 357 } 358 assert(_waiting_to_block == 0, "sanity check"); 359 360 #ifndef PRODUCT 361 if (SafepointTimeout) { 362 jlong current_time = os::javaTimeNanos(); 363 if (safepoint_limit_time < current_time) { 364 tty->print_cr("# SafepointSynchronize: Finished after " 365 INT64_FORMAT_W(6) " ms", 366 ((current_time - safepoint_limit_time) / MICROUNITS + 367 (jlong)SafepointTimeoutDelay)); 368 } 369 } 370 #endif 371 372 assert((_safepoint_counter & 0x1) == 0, "must be even"); 373 assert(Threads_lock->owned_by_self(), "must hold Threads_lock"); 374 _safepoint_counter ++; 375 376 // Record state 377 _state = _synchronized; 378 379 OrderAccess::fence(); 380 381 if (wait_blocked_event.should_commit()) { 382 wait_blocked_event.set_safepointId(safepoint_counter()); 383 wait_blocked_event.set_runningThreadCount(initial_waiting_to_block); 384 wait_blocked_event.commit(); 385 } 386 } // EventSafepointWaitBlocked 387 388 #ifdef ASSERT 389 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) { 390 // make sure all the threads were visited 391 assert(cur->was_visited_for_critical_count(), "missed a thread"); 392 } 393 #endif // ASSERT 394 395 // Update the count of active JNI critical regions 396 GCLocker::set_jni_lock_count(_current_jni_active_count); 397 398 if (log_is_enabled(Debug, safepoint)) { 399 VM_Operation *op = VMThread::vm_operation(); 400 log_debug(safepoint)("Entering safepoint region: %s", 401 (op != NULL) ? op->name() : "no vm operation"); 402 } 403 404 RuntimeService::record_safepoint_synchronized(); 405 if (PrintSafepointStatistics) { 406 update_statistics_on_sync_end(os::javaTimeNanos()); 407 } 408 409 // Call stuff that needs to be run when a safepoint is just about to be completed 410 { 411 EventSafepointCleanup cleanup_event; 412 do_cleanup_tasks(); 413 if (cleanup_event.should_commit()) { 414 cleanup_event.set_safepointId(safepoint_counter()); 415 cleanup_event.commit(); 416 } 417 } 418 419 if (PrintSafepointStatistics) { 420 // Record how much time spend on the above cleanup tasks 421 update_statistics_on_cleanup_end(os::javaTimeNanos()); 422 } 423 if (begin_event.should_commit()) { 424 begin_event.set_safepointId(safepoint_counter()); 425 begin_event.set_totalThreadCount(nof_threads); 426 begin_event.set_jniCriticalThreadCount(_current_jni_active_count); 427 begin_event.commit(); 428 } 429 } 430 431 // Wake up all threads, so they are ready to resume execution after the safepoint 432 // operation has been carried out 433 void SafepointSynchronize::end() { 434 EventSafepointEnd event; 435 int safepoint_id = safepoint_counter(); // Keep the odd counter as "id" 436 437 assert(Threads_lock->owned_by_self(), "must hold Threads_lock"); 438 assert((_safepoint_counter & 0x1) == 1, "must be odd"); 439 _safepoint_counter ++; 440 // memory fence isn't required here since an odd _safepoint_counter 441 // value can do no harm and a fence is issued below anyway. 442 443 DEBUG_ONLY(Thread* myThread = Thread::current();) 444 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint"); 445 446 if (PrintSafepointStatistics) { 447 end_statistics(os::javaTimeNanos()); 448 } 449 450 #ifdef ASSERT 451 // A pending_exception cannot be installed during a safepoint. The threads 452 // may install an async exception after they come back from a safepoint into 453 // pending_exception after they unblock. But that should happen later. 454 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) { 455 assert (!(cur->has_pending_exception() && 456 cur->safepoint_state()->is_at_poll_safepoint()), 457 "safepoint installed a pending exception"); 458 } 459 #endif // ASSERT 460 461 if (PageArmed) { 462 // Make polling safepoint aware 463 os::make_polling_page_readable(); 464 PageArmed = 0 ; 465 } 466 467 // Remove safepoint check from interpreter 468 Interpreter::ignore_safepoints(); 469 470 { 471 MutexLocker mu(Safepoint_lock); 472 473 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization"); 474 475 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method 476 // when they get restarted. 477 _state = _not_synchronized; 478 OrderAccess::fence(); 479 480 log_debug(safepoint)("Leaving safepoint region"); 481 482 // Start suspended threads 483 for(JavaThread *current = Threads::first(); current; current = current->next()) { 484 // A problem occurring on Solaris is when attempting to restart threads 485 // the first #cpus - 1 go well, but then the VMThread is preempted when we get 486 // to the next one (since it has been running the longest). We then have 487 // to wait for a cpu to become available before we can continue restarting 488 // threads. 489 // FIXME: This causes the performance of the VM to degrade when active and with 490 // large numbers of threads. Apparently this is due to the synchronous nature 491 // of suspending threads. 492 // 493 // TODO-FIXME: the comments above are vestigial and no longer apply. 494 // Furthermore, using solaris' schedctl in this particular context confers no benefit 495 if (VMThreadHintNoPreempt) { 496 os::hint_no_preempt(); 497 } 498 ThreadSafepointState* cur_state = current->safepoint_state(); 499 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint"); 500 cur_state->restart(); 501 assert(cur_state->is_running(), "safepoint state has not been reset"); 502 } 503 504 RuntimeService::record_safepoint_end(); 505 506 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads 507 // blocked in signal_thread_blocked 508 Threads_lock->unlock(); 509 510 } 511 #if INCLUDE_ALL_GCS 512 // If there are any concurrent GC threads resume them. 513 if (UseConcMarkSweepGC) { 514 ConcurrentMarkSweepThread::desynchronize(false); 515 } else if (UseG1GC) { 516 SuspendibleThreadSet::desynchronize(); 517 } 518 #endif // INCLUDE_ALL_GCS 519 // record this time so VMThread can keep track how much time has elapsed 520 // since last safepoint. 521 _end_of_last_safepoint = os::javaTimeMillis(); 522 523 if (event.should_commit()) { 524 event.set_safepointId(safepoint_id); 525 event.commit(); 526 } 527 } 528 529 bool SafepointSynchronize::is_cleanup_needed() { 530 // Need a safepoint if some inline cache buffers is non-empty 531 if (!InlineCacheBuffer::is_empty()) return true; 532 return false; 533 } 534 535 static void event_safepoint_cleanup_task_commit(EventSafepointCleanupTask& event, const char* name) { 536 if (event.should_commit()) { 537 event.set_safepointId(SafepointSynchronize::safepoint_counter()); 538 event.set_name(name); 539 event.commit(); 540 } 541 } 542 543 // Various cleaning tasks that should be done periodically at safepoints 544 void SafepointSynchronize::do_cleanup_tasks() { 545 { 546 const char* name = "deflating idle monitors"; 547 EventSafepointCleanupTask event; 548 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup)); 549 ObjectSynchronizer::deflate_idle_monitors(); 550 event_safepoint_cleanup_task_commit(event, name); 551 } 552 553 { 554 const char* name = "updating inline caches"; 555 EventSafepointCleanupTask event; 556 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup)); 557 InlineCacheBuffer::update_inline_caches(); 558 event_safepoint_cleanup_task_commit(event, name); 559 } 560 { 561 const char* name = "compilation policy safepoint handler"; 562 EventSafepointCleanupTask event; 563 TraceTime timer("compilation policy safepoint handler", TRACETIME_LOG(Info, safepoint, cleanup)); 564 CompilationPolicy::policy()->do_safepoint_work(); 565 event_safepoint_cleanup_task_commit(event, name); 566 } 567 568 { 569 const char* name = "mark nmethods"; 570 EventSafepointCleanupTask event; 571 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup)); 572 NMethodSweeper::mark_active_nmethods(); 573 event_safepoint_cleanup_task_commit(event, name); 574 } 575 576 if (SymbolTable::needs_rehashing()) { 577 const char* name = "rehashing symbol table"; 578 EventSafepointCleanupTask event; 579 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup)); 580 SymbolTable::rehash_table(); 581 event_safepoint_cleanup_task_commit(event, name); 582 } 583 584 if (StringTable::needs_rehashing()) { 585 const char* name = "rehashing string table"; 586 EventSafepointCleanupTask event; 587 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup)); 588 StringTable::rehash_table(); 589 event_safepoint_cleanup_task_commit(event, name); 590 } 591 592 { 593 // CMS delays purging the CLDG until the beginning of the next safepoint and to 594 // make sure concurrent sweep is done 595 const char* name = "purging class loader data graph"; 596 EventSafepointCleanupTask event; 597 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup)); 598 ClassLoaderDataGraph::purge_if_needed(); 599 event_safepoint_cleanup_task_commit(event, name); 600 } 601 } 602 603 604 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) { 605 switch(state) { 606 case _thread_in_native: 607 // native threads are safe if they have no java stack or have walkable stack 608 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable(); 609 610 // blocked threads should have already have walkable stack 611 case _thread_blocked: 612 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable"); 613 return true; 614 615 default: 616 return false; 617 } 618 } 619 620 621 // See if the thread is running inside a lazy critical native and 622 // update the thread critical count if so. Also set a suspend flag to 623 // cause the native wrapper to return into the JVM to do the unlock 624 // once the native finishes. 625 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) { 626 if (state == _thread_in_native && 627 thread->has_last_Java_frame() && 628 thread->frame_anchor()->walkable()) { 629 // This thread might be in a critical native nmethod so look at 630 // the top of the stack and increment the critical count if it 631 // is. 632 frame wrapper_frame = thread->last_frame(); 633 CodeBlob* stub_cb = wrapper_frame.cb(); 634 if (stub_cb != NULL && 635 stub_cb->is_nmethod() && 636 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) { 637 // A thread could potentially be in a critical native across 638 // more than one safepoint, so only update the critical state on 639 // the first one. When it returns it will perform the unlock. 640 if (!thread->do_critical_native_unlock()) { 641 #ifdef ASSERT 642 if (!thread->in_critical()) { 643 GCLocker::increment_debug_jni_lock_count(); 644 } 645 #endif 646 thread->enter_critical(); 647 // Make sure the native wrapper calls back on return to 648 // perform the needed critical unlock. 649 thread->set_critical_native_unlock(); 650 } 651 } 652 } 653 } 654 655 656 657 // ------------------------------------------------------------------------------------------------------- 658 // Implementation of Safepoint callback point 659 660 void SafepointSynchronize::block(JavaThread *thread) { 661 assert(thread != NULL, "thread must be set"); 662 assert(thread->is_Java_thread(), "not a Java thread"); 663 664 // Threads shouldn't block if they are in the middle of printing, but... 665 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id()); 666 667 // Only bail from the block() call if the thread is gone from the 668 // thread list; starting to exit should still block. 669 if (thread->is_terminated()) { 670 // block current thread if we come here from native code when VM is gone 671 thread->block_if_vm_exited(); 672 673 // otherwise do nothing 674 return; 675 } 676 677 JavaThreadState state = thread->thread_state(); 678 thread->frame_anchor()->make_walkable(thread); 679 680 // Check that we have a valid thread_state at this point 681 switch(state) { 682 case _thread_in_vm_trans: 683 case _thread_in_Java: // From compiled code 684 685 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case, 686 // we pretend we are still in the VM. 687 thread->set_thread_state(_thread_in_vm); 688 689 if (is_synchronizing()) { 690 Atomic::inc (&TryingToBlock) ; 691 } 692 693 // We will always be holding the Safepoint_lock when we are examine the state 694 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and 695 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code 696 Safepoint_lock->lock_without_safepoint_check(); 697 if (is_synchronizing()) { 698 // Decrement the number of threads to wait for and signal vm thread 699 assert(_waiting_to_block > 0, "sanity check"); 700 _waiting_to_block--; 701 thread->safepoint_state()->set_has_called_back(true); 702 703 DEBUG_ONLY(thread->set_visited_for_critical_count(true)); 704 if (thread->in_critical()) { 705 // Notice that this thread is in a critical section 706 increment_jni_active_count(); 707 } 708 709 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread 710 if (_waiting_to_block == 0) { 711 Safepoint_lock->notify_all(); 712 } 713 } 714 715 // We transition the thread to state _thread_blocked here, but 716 // we can't do our usual check for external suspension and then 717 // self-suspend after the lock_without_safepoint_check() call 718 // below because we are often called during transitions while 719 // we hold different locks. That would leave us suspended while 720 // holding a resource which results in deadlocks. 721 thread->set_thread_state(_thread_blocked); 722 Safepoint_lock->unlock(); 723 724 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during 725 // the entire safepoint, the threads will all line up here during the safepoint. 726 Threads_lock->lock_without_safepoint_check(); 727 // restore original state. This is important if the thread comes from compiled code, so it 728 // will continue to execute with the _thread_in_Java state. 729 thread->set_thread_state(state); 730 Threads_lock->unlock(); 731 break; 732 733 case _thread_in_native_trans: 734 case _thread_blocked_trans: 735 case _thread_new_trans: 736 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) { 737 thread->print_thread_state(); 738 fatal("Deadlock in safepoint code. " 739 "Should have called back to the VM before blocking."); 740 } 741 742 // We transition the thread to state _thread_blocked here, but 743 // we can't do our usual check for external suspension and then 744 // self-suspend after the lock_without_safepoint_check() call 745 // below because we are often called during transitions while 746 // we hold different locks. That would leave us suspended while 747 // holding a resource which results in deadlocks. 748 thread->set_thread_state(_thread_blocked); 749 750 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence, 751 // the safepoint code might still be waiting for it to block. We need to change the state here, 752 // so it can see that it is at a safepoint. 753 754 // Block until the safepoint operation is completed. 755 Threads_lock->lock_without_safepoint_check(); 756 757 // Restore state 758 thread->set_thread_state(state); 759 760 Threads_lock->unlock(); 761 break; 762 763 default: 764 fatal("Illegal threadstate encountered: %d", state); 765 } 766 767 // Check for pending. async. exceptions or suspends - except if the 768 // thread was blocked inside the VM. has_special_runtime_exit_condition() 769 // is called last since it grabs a lock and we only want to do that when 770 // we must. 771 // 772 // Note: we never deliver an async exception at a polling point as the 773 // compiler may not have an exception handler for it. The polling 774 // code will notice the async and deoptimize and the exception will 775 // be delivered. (Polling at a return point is ok though). Sure is 776 // a lot of bother for a deprecated feature... 777 // 778 // We don't deliver an async exception if the thread state is 779 // _thread_in_native_trans so JNI functions won't be called with 780 // a surprising pending exception. If the thread state is going back to java, 781 // async exception is checked in check_special_condition_for_native_trans(). 782 783 if (state != _thread_blocked_trans && 784 state != _thread_in_vm_trans && 785 thread->has_special_runtime_exit_condition()) { 786 thread->handle_special_runtime_exit_condition( 787 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans)); 788 } 789 } 790 791 // ------------------------------------------------------------------------------------------------------ 792 // Exception handlers 793 794 795 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) { 796 assert(thread->is_Java_thread(), "polling reference encountered by VM thread"); 797 assert(thread->thread_state() == _thread_in_Java, "should come from Java code"); 798 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization"); 799 800 if (ShowSafepointMsgs) { 801 tty->print("handle_polling_page_exception: "); 802 } 803 804 if (PrintSafepointStatistics) { 805 inc_page_trap_count(); 806 } 807 808 ThreadSafepointState* state = thread->safepoint_state(); 809 810 state->handle_polling_page_exception(); 811 } 812 813 814 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) { 815 if (!timeout_error_printed) { 816 timeout_error_printed = true; 817 // Print out the thread info which didn't reach the safepoint for debugging 818 // purposes (useful when there are lots of threads in the debugger). 819 tty->cr(); 820 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:"); 821 if (reason == _spinning_timeout) { 822 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint."); 823 } else if (reason == _blocking_timeout) { 824 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop."); 825 } 826 827 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:"); 828 ThreadSafepointState *cur_state; 829 ResourceMark rm; 830 for(JavaThread *cur_thread = Threads::first(); cur_thread; 831 cur_thread = cur_thread->next()) { 832 cur_state = cur_thread->safepoint_state(); 833 834 if (cur_thread->thread_state() != _thread_blocked && 835 ((reason == _spinning_timeout && cur_state->is_running()) || 836 (reason == _blocking_timeout && !cur_state->has_called_back()))) { 837 tty->print("# "); 838 cur_thread->print(); 839 tty->cr(); 840 } 841 } 842 tty->print_cr("# SafepointSynchronize::begin: (End of list)"); 843 } 844 845 // To debug the long safepoint, specify both DieOnSafepointTimeout & 846 // ShowMessageBoxOnError. 847 if (DieOnSafepointTimeout) { 848 VM_Operation *op = VMThread::vm_operation(); 849 fatal("Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.", 850 SafepointTimeoutDelay, 851 op != NULL ? op->name() : "no vm operation"); 852 } 853 } 854 855 856 // ------------------------------------------------------------------------------------------------------- 857 // Implementation of ThreadSafepointState 858 859 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) { 860 _thread = thread; 861 _type = _running; 862 _has_called_back = false; 863 _at_poll_safepoint = false; 864 } 865 866 void ThreadSafepointState::create(JavaThread *thread) { 867 ThreadSafepointState *state = new ThreadSafepointState(thread); 868 thread->set_safepoint_state(state); 869 } 870 871 void ThreadSafepointState::destroy(JavaThread *thread) { 872 if (thread->safepoint_state()) { 873 delete(thread->safepoint_state()); 874 thread->set_safepoint_state(NULL); 875 } 876 } 877 878 void ThreadSafepointState::examine_state_of_thread() { 879 assert(is_running(), "better be running or just have hit safepoint poll"); 880 881 JavaThreadState state = _thread->thread_state(); 882 883 // Save the state at the start of safepoint processing. 884 _orig_thread_state = state; 885 886 // Check for a thread that is suspended. Note that thread resume tries 887 // to grab the Threads_lock which we own here, so a thread cannot be 888 // resumed during safepoint synchronization. 889 890 // We check to see if this thread is suspended without locking to 891 // avoid deadlocking with a third thread that is waiting for this 892 // thread to be suspended. The third thread can notice the safepoint 893 // that we're trying to start at the beginning of its SR_lock->wait() 894 // call. If that happens, then the third thread will block on the 895 // safepoint while still holding the underlying SR_lock. We won't be 896 // able to get the SR_lock and we'll deadlock. 897 // 898 // We don't need to grab the SR_lock here for two reasons: 899 // 1) The suspend flags are both volatile and are set with an 900 // Atomic::cmpxchg() call so we should see the suspended 901 // state right away. 902 // 2) We're being called from the safepoint polling loop; if 903 // we don't see the suspended state on this iteration, then 904 // we'll come around again. 905 // 906 bool is_suspended = _thread->is_ext_suspended(); 907 if (is_suspended) { 908 roll_forward(_at_safepoint); 909 return; 910 } 911 912 // Some JavaThread states have an initial safepoint state of 913 // running, but are actually at a safepoint. We will happily 914 // agree and update the safepoint state here. 915 if (SafepointSynchronize::safepoint_safe(_thread, state)) { 916 SafepointSynchronize::check_for_lazy_critical_native(_thread, state); 917 roll_forward(_at_safepoint); 918 return; 919 } 920 921 if (state == _thread_in_vm) { 922 roll_forward(_call_back); 923 return; 924 } 925 926 // All other thread states will continue to run until they 927 // transition and self-block in state _blocked 928 // Safepoint polling in compiled code causes the Java threads to do the same. 929 // Note: new threads may require a malloc so they must be allowed to finish 930 931 assert(is_running(), "examine_state_of_thread on non-running thread"); 932 return; 933 } 934 935 // Returns true is thread could not be rolled forward at present position. 936 void ThreadSafepointState::roll_forward(suspend_type type) { 937 _type = type; 938 939 switch(_type) { 940 case _at_safepoint: 941 SafepointSynchronize::signal_thread_at_safepoint(); 942 DEBUG_ONLY(_thread->set_visited_for_critical_count(true)); 943 if (_thread->in_critical()) { 944 // Notice that this thread is in a critical section 945 SafepointSynchronize::increment_jni_active_count(); 946 } 947 break; 948 949 case _call_back: 950 set_has_called_back(false); 951 break; 952 953 case _running: 954 default: 955 ShouldNotReachHere(); 956 } 957 } 958 959 void ThreadSafepointState::restart() { 960 switch(type()) { 961 case _at_safepoint: 962 case _call_back: 963 break; 964 965 case _running: 966 default: 967 tty->print_cr("restart thread " INTPTR_FORMAT " with state %d", 968 p2i(_thread), _type); 969 _thread->print(); 970 ShouldNotReachHere(); 971 } 972 _type = _running; 973 set_has_called_back(false); 974 } 975 976 977 void ThreadSafepointState::print_on(outputStream *st) const { 978 const char *s = NULL; 979 980 switch(_type) { 981 case _running : s = "_running"; break; 982 case _at_safepoint : s = "_at_safepoint"; break; 983 case _call_back : s = "_call_back"; break; 984 default: 985 ShouldNotReachHere(); 986 } 987 988 st->print_cr("Thread: " INTPTR_FORMAT 989 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d", 990 p2i(_thread), _thread->osthread()->thread_id(), s, _has_called_back, 991 _at_poll_safepoint); 992 993 _thread->print_thread_state_on(st); 994 } 995 996 // --------------------------------------------------------------------------------------------------------------------- 997 998 // Block the thread at the safepoint poll or poll return. 999 void ThreadSafepointState::handle_polling_page_exception() { 1000 1001 // Check state. block() will set thread state to thread_in_vm which will 1002 // cause the safepoint state _type to become _call_back. 1003 assert(type() == ThreadSafepointState::_running, 1004 "polling page exception on thread not running state"); 1005 1006 // Step 1: Find the nmethod from the return address 1007 if (ShowSafepointMsgs && Verbose) { 1008 tty->print_cr("Polling page exception at " INTPTR_FORMAT, p2i(thread()->saved_exception_pc())); 1009 } 1010 address real_return_addr = thread()->saved_exception_pc(); 1011 1012 CodeBlob *cb = CodeCache::find_blob(real_return_addr); 1013 assert(cb != NULL && cb->is_compiled(), "return address should be in nmethod"); 1014 CompiledMethod* nm = (CompiledMethod*)cb; 1015 1016 // Find frame of caller 1017 frame stub_fr = thread()->last_frame(); 1018 CodeBlob* stub_cb = stub_fr.cb(); 1019 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub"); 1020 RegisterMap map(thread(), true); 1021 frame caller_fr = stub_fr.sender(&map); 1022 1023 // Should only be poll_return or poll 1024 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" ); 1025 1026 // This is a poll immediately before a return. The exception handling code 1027 // has already had the effect of causing the return to occur, so the execution 1028 // will continue immediately after the call. In addition, the oopmap at the 1029 // return point does not mark the return value as an oop (if it is), so 1030 // it needs a handle here to be updated. 1031 if( nm->is_at_poll_return(real_return_addr) ) { 1032 // See if return type is an oop. 1033 bool return_oop = nm->method()->is_returning_oop(); 1034 Handle return_value; 1035 if (return_oop) { 1036 // The oop result has been saved on the stack together with all 1037 // the other registers. In order to preserve it over GCs we need 1038 // to keep it in a handle. 1039 oop result = caller_fr.saved_oop_result(&map); 1040 assert(result == NULL || result->is_oop(), "must be oop"); 1041 return_value = Handle(thread(), result); 1042 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer"); 1043 } 1044 1045 // Block the thread 1046 SafepointSynchronize::block(thread()); 1047 1048 // restore oop result, if any 1049 if (return_oop) { 1050 caller_fr.set_saved_oop_result(&map, return_value()); 1051 } 1052 } 1053 1054 // This is a safepoint poll. Verify the return address and block. 1055 else { 1056 set_at_poll_safepoint(true); 1057 1058 // verify the blob built the "return address" correctly 1059 assert(real_return_addr == caller_fr.pc(), "must match"); 1060 1061 // Block the thread 1062 SafepointSynchronize::block(thread()); 1063 set_at_poll_safepoint(false); 1064 1065 // If we have a pending async exception deoptimize the frame 1066 // as otherwise we may never deliver it. 1067 if (thread()->has_async_condition()) { 1068 ThreadInVMfromJavaNoAsyncException __tiv(thread()); 1069 Deoptimization::deoptimize_frame(thread(), caller_fr.id()); 1070 } 1071 1072 // If an exception has been installed we must check for a pending deoptimization 1073 // Deoptimize frame if exception has been thrown. 1074 1075 if (thread()->has_pending_exception() ) { 1076 RegisterMap map(thread(), true); 1077 frame caller_fr = stub_fr.sender(&map); 1078 if (caller_fr.is_deoptimized_frame()) { 1079 // The exception patch will destroy registers that are still 1080 // live and will be needed during deoptimization. Defer the 1081 // Async exception should have deferred the exception until the 1082 // next safepoint which will be detected when we get into 1083 // the interpreter so if we have an exception now things 1084 // are messed up. 1085 1086 fatal("Exception installed and deoptimization is pending"); 1087 } 1088 } 1089 } 1090 } 1091 1092 1093 // 1094 // Statistics & Instrumentations 1095 // 1096 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL; 1097 jlong SafepointSynchronize::_safepoint_begin_time = 0; 1098 int SafepointSynchronize::_cur_stat_index = 0; 1099 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating]; 1100 julong SafepointSynchronize::_coalesced_vmop_count = 0; 1101 jlong SafepointSynchronize::_max_sync_time = 0; 1102 jlong SafepointSynchronize::_max_vmop_time = 0; 1103 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f; 1104 1105 static jlong cleanup_end_time = 0; 1106 static bool need_to_track_page_armed_status = false; 1107 static bool init_done = false; 1108 1109 // Helper method to print the header. 1110 static void print_header() { 1111 tty->print(" vmop " 1112 "[threads: total initially_running wait_to_block] "); 1113 tty->print("[time: spin block sync cleanup vmop] "); 1114 1115 // no page armed status printed out if it is always armed. 1116 if (need_to_track_page_armed_status) { 1117 tty->print("page_armed "); 1118 } 1119 1120 tty->print_cr("page_trap_count"); 1121 } 1122 1123 void SafepointSynchronize::deferred_initialize_stat() { 1124 if (init_done) return; 1125 1126 // If PrintSafepointStatisticsTimeout is specified, the statistics data will 1127 // be printed right away, in which case, _safepoint_stats will regress to 1128 // a single element array. Otherwise, it is a circular ring buffer with default 1129 // size of PrintSafepointStatisticsCount. 1130 int stats_array_size; 1131 if (PrintSafepointStatisticsTimeout > 0) { 1132 stats_array_size = 1; 1133 PrintSafepointStatistics = true; 1134 } else { 1135 stats_array_size = PrintSafepointStatisticsCount; 1136 } 1137 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size 1138 * sizeof(SafepointStats), mtInternal); 1139 guarantee(_safepoint_stats != NULL, 1140 "not enough memory for safepoint instrumentation data"); 1141 1142 if (DeferPollingPageLoopCount >= 0) { 1143 need_to_track_page_armed_status = true; 1144 } 1145 init_done = true; 1146 } 1147 1148 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) { 1149 assert(init_done, "safepoint statistics array hasn't been initialized"); 1150 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1151 1152 spstat->_time_stamp = _ts_of_current_safepoint; 1153 1154 VM_Operation *op = VMThread::vm_operation(); 1155 spstat->_vmop_type = (op != NULL ? op->type() : -1); 1156 if (op != NULL) { 1157 _safepoint_reasons[spstat->_vmop_type]++; 1158 } 1159 1160 spstat->_nof_total_threads = nof_threads; 1161 spstat->_nof_initial_running_threads = nof_running; 1162 spstat->_nof_threads_hit_page_trap = 0; 1163 1164 // Records the start time of spinning. The real time spent on spinning 1165 // will be adjusted when spin is done. Same trick is applied for time 1166 // spent on waiting for threads to block. 1167 if (nof_running != 0) { 1168 spstat->_time_to_spin = os::javaTimeNanos(); 1169 } else { 1170 spstat->_time_to_spin = 0; 1171 } 1172 } 1173 1174 void SafepointSynchronize::update_statistics_on_spin_end() { 1175 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1176 1177 jlong cur_time = os::javaTimeNanos(); 1178 1179 spstat->_nof_threads_wait_to_block = _waiting_to_block; 1180 if (spstat->_nof_initial_running_threads != 0) { 1181 spstat->_time_to_spin = cur_time - spstat->_time_to_spin; 1182 } 1183 1184 if (need_to_track_page_armed_status) { 1185 spstat->_page_armed = (PageArmed == 1); 1186 } 1187 1188 // Records the start time of waiting for to block. Updated when block is done. 1189 if (_waiting_to_block != 0) { 1190 spstat->_time_to_wait_to_block = cur_time; 1191 } else { 1192 spstat->_time_to_wait_to_block = 0; 1193 } 1194 } 1195 1196 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) { 1197 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1198 1199 if (spstat->_nof_threads_wait_to_block != 0) { 1200 spstat->_time_to_wait_to_block = end_time - 1201 spstat->_time_to_wait_to_block; 1202 } 1203 1204 // Records the end time of sync which will be used to calculate the total 1205 // vm operation time. Again, the real time spending in syncing will be deducted 1206 // from the start of the sync time later when end_statistics is called. 1207 spstat->_time_to_sync = end_time - _safepoint_begin_time; 1208 if (spstat->_time_to_sync > _max_sync_time) { 1209 _max_sync_time = spstat->_time_to_sync; 1210 } 1211 1212 spstat->_time_to_do_cleanups = end_time; 1213 } 1214 1215 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) { 1216 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1217 1218 // Record how long spent in cleanup tasks. 1219 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups; 1220 1221 cleanup_end_time = end_time; 1222 } 1223 1224 void SafepointSynchronize::end_statistics(jlong vmop_end_time) { 1225 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1226 1227 // Update the vm operation time. 1228 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time; 1229 if (spstat->_time_to_exec_vmop > _max_vmop_time) { 1230 _max_vmop_time = spstat->_time_to_exec_vmop; 1231 } 1232 // Only the sync time longer than the specified 1233 // PrintSafepointStatisticsTimeout will be printed out right away. 1234 // By default, it is -1 meaning all samples will be put into the list. 1235 if ( PrintSafepointStatisticsTimeout > 0) { 1236 if (spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) { 1237 print_statistics(); 1238 } 1239 } else { 1240 // The safepoint statistics will be printed out when the _safepoin_stats 1241 // array fills up. 1242 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) { 1243 print_statistics(); 1244 _cur_stat_index = 0; 1245 } else { 1246 _cur_stat_index++; 1247 } 1248 } 1249 } 1250 1251 void SafepointSynchronize::print_statistics() { 1252 SafepointStats* sstats = _safepoint_stats; 1253 1254 for (int index = 0; index <= _cur_stat_index; index++) { 1255 if (index % 30 == 0) { 1256 print_header(); 1257 } 1258 sstats = &_safepoint_stats[index]; 1259 tty->print("%.3f: ", sstats->_time_stamp); 1260 tty->print("%-26s [" 1261 INT32_FORMAT_W(8) INT32_FORMAT_W(11) INT32_FORMAT_W(15) 1262 " ] ", 1263 sstats->_vmop_type == -1 ? "no vm operation" : 1264 VM_Operation::name(sstats->_vmop_type), 1265 sstats->_nof_total_threads, 1266 sstats->_nof_initial_running_threads, 1267 sstats->_nof_threads_wait_to_block); 1268 // "/ MICROUNITS " is to convert the unit from nanos to millis. 1269 tty->print(" [" 1270 INT64_FORMAT_W(6) INT64_FORMAT_W(6) 1271 INT64_FORMAT_W(6) INT64_FORMAT_W(6) 1272 INT64_FORMAT_W(6) " ] ", 1273 sstats->_time_to_spin / MICROUNITS, 1274 sstats->_time_to_wait_to_block / MICROUNITS, 1275 sstats->_time_to_sync / MICROUNITS, 1276 sstats->_time_to_do_cleanups / MICROUNITS, 1277 sstats->_time_to_exec_vmop / MICROUNITS); 1278 1279 if (need_to_track_page_armed_status) { 1280 tty->print(INT32_FORMAT " ", sstats->_page_armed); 1281 } 1282 tty->print_cr(INT32_FORMAT " ", sstats->_nof_threads_hit_page_trap); 1283 } 1284 } 1285 1286 // This method will be called when VM exits. It will first call 1287 // print_statistics to print out the rest of the sampling. Then 1288 // it tries to summarize the sampling. 1289 void SafepointSynchronize::print_stat_on_exit() { 1290 if (_safepoint_stats == NULL) return; 1291 1292 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1293 1294 // During VM exit, end_statistics may not get called and in that 1295 // case, if the sync time is less than PrintSafepointStatisticsTimeout, 1296 // don't print it out. 1297 // Approximate the vm op time. 1298 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop = 1299 os::javaTimeNanos() - cleanup_end_time; 1300 1301 if ( PrintSafepointStatisticsTimeout < 0 || 1302 spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) { 1303 print_statistics(); 1304 } 1305 tty->cr(); 1306 1307 // Print out polling page sampling status. 1308 if (!need_to_track_page_armed_status) { 1309 tty->print_cr("Polling page always armed"); 1310 } else { 1311 tty->print_cr("Defer polling page loop count = " INTX_FORMAT "\n", 1312 DeferPollingPageLoopCount); 1313 } 1314 1315 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) { 1316 if (_safepoint_reasons[index] != 0) { 1317 tty->print_cr("%-26s" UINT64_FORMAT_W(10), VM_Operation::name(index), 1318 _safepoint_reasons[index]); 1319 } 1320 } 1321 1322 tty->print_cr(UINT64_FORMAT_W(5) " VM operations coalesced during safepoint", 1323 _coalesced_vmop_count); 1324 tty->print_cr("Maximum sync time " INT64_FORMAT_W(5) " ms", 1325 _max_sync_time / MICROUNITS); 1326 tty->print_cr("Maximum vm operation time (except for Exit VM operation) " 1327 INT64_FORMAT_W(5) " ms", 1328 _max_vmop_time / MICROUNITS); 1329 } 1330 1331 // ------------------------------------------------------------------------------------------------ 1332 // Non-product code 1333 1334 #ifndef PRODUCT 1335 1336 void SafepointSynchronize::print_state() { 1337 if (_state == _not_synchronized) { 1338 tty->print_cr("not synchronized"); 1339 } else if (_state == _synchronizing || _state == _synchronized) { 1340 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" : 1341 "synchronized"); 1342 1343 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) { 1344 cur->safepoint_state()->print(); 1345 } 1346 } 1347 } 1348 1349 void SafepointSynchronize::safepoint_msg(const char* format, ...) { 1350 if (ShowSafepointMsgs) { 1351 va_list ap; 1352 va_start(ap, format); 1353 tty->vprint_cr(format, ap); 1354 va_end(ap); 1355 } 1356 } 1357 1358 #endif // !PRODUCT