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