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 "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 log_debug(safepoint)("Entering safepoint region: %s", VMThread::vm_safepoint_description()); 400 } 401 402 RuntimeService::record_safepoint_synchronized(); 403 if (PrintSafepointStatistics) { 404 update_statistics_on_sync_end(os::javaTimeNanos()); 405 } 406 407 // Call stuff that needs to be run when a safepoint is just about to be completed 408 { 409 EventSafepointCleanup cleanup_event; 410 do_cleanup_tasks(); 411 if (cleanup_event.should_commit()) { 412 cleanup_event.set_safepointId(safepoint_counter()); 413 cleanup_event.commit(); 414 } 415 } 416 417 if (PrintSafepointStatistics) { 418 // Record how much time spend on the above cleanup tasks 419 update_statistics_on_cleanup_end(os::javaTimeNanos()); 420 } 421 if (begin_event.should_commit()) { 422 begin_event.set_safepointId(safepoint_counter()); 423 begin_event.set_totalThreadCount(nof_threads); 424 begin_event.set_jniCriticalThreadCount(_current_jni_active_count); 425 begin_event.commit(); 426 } 427 } 428 429 // Wake up all threads, so they are ready to resume execution after the safepoint 430 // operation has been carried out 431 void SafepointSynchronize::end() { 432 EventSafepointEnd event; 433 int safepoint_id = safepoint_counter(); // Keep the odd counter as "id" 434 435 assert(Threads_lock->owned_by_self(), "must hold Threads_lock"); 436 assert((_safepoint_counter & 0x1) == 1, "must be odd"); 437 _safepoint_counter ++; 438 // memory fence isn't required here since an odd _safepoint_counter 439 // value can do no harm and a fence is issued below anyway. 440 441 DEBUG_ONLY(Thread* myThread = Thread::current();) 442 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint"); 443 444 if (PrintSafepointStatistics) { 445 end_statistics(os::javaTimeNanos()); 446 } 447 448 #ifdef ASSERT 449 // A pending_exception cannot be installed during a safepoint. The threads 450 // may install an async exception after they come back from a safepoint into 451 // pending_exception after they unblock. But that should happen later. 452 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) { 453 assert (!(cur->has_pending_exception() && 454 cur->safepoint_state()->is_at_poll_safepoint()), 455 "safepoint installed a pending exception"); 456 } 457 #endif // ASSERT 458 459 if (PageArmed) { 460 // Make polling safepoint aware 461 os::make_polling_page_readable(); 462 PageArmed = 0 ; 463 } 464 465 // Remove safepoint check from interpreter 466 Interpreter::ignore_safepoints(); 467 468 { 469 MutexLocker mu(Safepoint_lock); 470 471 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization"); 472 473 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method 474 // when they get restarted. 475 _state = _not_synchronized; 476 OrderAccess::fence(); 477 478 log_debug(safepoint)("Leaving safepoint region"); 479 480 // Start suspended threads 481 for(JavaThread *current = Threads::first(); current; current = current->next()) { 482 // A problem occurring on Solaris is when attempting to restart threads 483 // the first #cpus - 1 go well, but then the VMThread is preempted when we get 484 // to the next one (since it has been running the longest). We then have 485 // to wait for a cpu to become available before we can continue restarting 486 // threads. 487 // FIXME: This causes the performance of the VM to degrade when active and with 488 // large numbers of threads. Apparently this is due to the synchronous nature 489 // of suspending threads. 490 // 491 // TODO-FIXME: the comments above are vestigial and no longer apply. 492 // Furthermore, using solaris' schedctl in this particular context confers no benefit 493 if (VMThreadHintNoPreempt) { 494 os::hint_no_preempt(); 495 } 496 ThreadSafepointState* cur_state = current->safepoint_state(); 497 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint"); 498 cur_state->restart(); 499 assert(cur_state->is_running(), "safepoint state has not been reset"); 500 } 501 502 RuntimeService::record_safepoint_end(); 503 504 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads 505 // blocked in signal_thread_blocked 506 Threads_lock->unlock(); 507 508 } 509 #if INCLUDE_ALL_GCS 510 // If there are any concurrent GC threads resume them. 511 if (UseConcMarkSweepGC) { 512 ConcurrentMarkSweepThread::desynchronize(false); 513 } else if (UseG1GC) { 514 SuspendibleThreadSet::desynchronize(); 515 } 516 #endif // INCLUDE_ALL_GCS 517 // record this time so VMThread can keep track how much time has elapsed 518 // since last safepoint. 519 _end_of_last_safepoint = os::javaTimeMillis(); 520 521 if (event.should_commit()) { 522 event.set_safepointId(safepoint_id); 523 event.commit(); 524 } 525 } 526 527 bool SafepointSynchronize::is_cleanup_needed() { 528 // Need a safepoint if there are many monitors to deflate. 529 if (ObjectSynchronizer::is_cleanup_needed()) return true; 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 fatal("Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.", 849 SafepointTimeoutDelay, VMThread::vm_safepoint_description()); 850 } 851 } 852 853 854 // ------------------------------------------------------------------------------------------------------- 855 // Implementation of ThreadSafepointState 856 857 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) { 858 _thread = thread; 859 _type = _running; 860 _has_called_back = false; 861 _at_poll_safepoint = false; 862 } 863 864 void ThreadSafepointState::create(JavaThread *thread) { 865 ThreadSafepointState *state = new ThreadSafepointState(thread); 866 thread->set_safepoint_state(state); 867 } 868 869 void ThreadSafepointState::destroy(JavaThread *thread) { 870 if (thread->safepoint_state()) { 871 delete(thread->safepoint_state()); 872 thread->set_safepoint_state(NULL); 873 } 874 } 875 876 void ThreadSafepointState::examine_state_of_thread() { 877 assert(is_running(), "better be running or just have hit safepoint poll"); 878 879 JavaThreadState state = _thread->thread_state(); 880 881 // Save the state at the start of safepoint processing. 882 _orig_thread_state = state; 883 884 // Check for a thread that is suspended. Note that thread resume tries 885 // to grab the Threads_lock which we own here, so a thread cannot be 886 // resumed during safepoint synchronization. 887 888 // We check to see if this thread is suspended without locking to 889 // avoid deadlocking with a third thread that is waiting for this 890 // thread to be suspended. The third thread can notice the safepoint 891 // that we're trying to start at the beginning of its SR_lock->wait() 892 // call. If that happens, then the third thread will block on the 893 // safepoint while still holding the underlying SR_lock. We won't be 894 // able to get the SR_lock and we'll deadlock. 895 // 896 // We don't need to grab the SR_lock here for two reasons: 897 // 1) The suspend flags are both volatile and are set with an 898 // Atomic::cmpxchg() call so we should see the suspended 899 // state right away. 900 // 2) We're being called from the safepoint polling loop; if 901 // we don't see the suspended state on this iteration, then 902 // we'll come around again. 903 // 904 bool is_suspended = _thread->is_ext_suspended(); 905 if (is_suspended) { 906 roll_forward(_at_safepoint); 907 return; 908 } 909 910 // Some JavaThread states have an initial safepoint state of 911 // running, but are actually at a safepoint. We will happily 912 // agree and update the safepoint state here. 913 if (SafepointSynchronize::safepoint_safe(_thread, state)) { 914 SafepointSynchronize::check_for_lazy_critical_native(_thread, state); 915 roll_forward(_at_safepoint); 916 return; 917 } 918 919 if (state == _thread_in_vm) { 920 roll_forward(_call_back); 921 return; 922 } 923 924 // All other thread states will continue to run until they 925 // transition and self-block in state _blocked 926 // Safepoint polling in compiled code causes the Java threads to do the same. 927 // Note: new threads may require a malloc so they must be allowed to finish 928 929 assert(is_running(), "examine_state_of_thread on non-running thread"); 930 return; 931 } 932 933 // Returns true is thread could not be rolled forward at present position. 934 void ThreadSafepointState::roll_forward(suspend_type type) { 935 _type = type; 936 937 switch(_type) { 938 case _at_safepoint: 939 SafepointSynchronize::signal_thread_at_safepoint(); 940 DEBUG_ONLY(_thread->set_visited_for_critical_count(true)); 941 if (_thread->in_critical()) { 942 // Notice that this thread is in a critical section 943 SafepointSynchronize::increment_jni_active_count(); 944 } 945 break; 946 947 case _call_back: 948 set_has_called_back(false); 949 break; 950 951 case _running: 952 default: 953 ShouldNotReachHere(); 954 } 955 } 956 957 void ThreadSafepointState::restart() { 958 switch(type()) { 959 case _at_safepoint: 960 case _call_back: 961 break; 962 963 case _running: 964 default: 965 tty->print_cr("restart thread " INTPTR_FORMAT " with state %d", 966 p2i(_thread), _type); 967 _thread->print(); 968 ShouldNotReachHere(); 969 } 970 _type = _running; 971 set_has_called_back(false); 972 } 973 974 975 void ThreadSafepointState::print_on(outputStream *st) const { 976 const char *s = NULL; 977 978 switch(_type) { 979 case _running : s = "_running"; break; 980 case _at_safepoint : s = "_at_safepoint"; break; 981 case _call_back : s = "_call_back"; break; 982 default: 983 ShouldNotReachHere(); 984 } 985 986 st->print_cr("Thread: " INTPTR_FORMAT 987 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d", 988 p2i(_thread), _thread->osthread()->thread_id(), s, _has_called_back, 989 _at_poll_safepoint); 990 991 _thread->print_thread_state_on(st); 992 } 993 994 // --------------------------------------------------------------------------------------------------------------------- 995 996 // Block the thread at the safepoint poll or poll return. 997 void ThreadSafepointState::handle_polling_page_exception() { 998 999 // Check state. block() will set thread state to thread_in_vm which will 1000 // cause the safepoint state _type to become _call_back. 1001 assert(type() == ThreadSafepointState::_running, 1002 "polling page exception on thread not running state"); 1003 1004 // Step 1: Find the nmethod from the return address 1005 if (ShowSafepointMsgs && Verbose) { 1006 tty->print_cr("Polling page exception at " INTPTR_FORMAT, p2i(thread()->saved_exception_pc())); 1007 } 1008 address real_return_addr = thread()->saved_exception_pc(); 1009 1010 CodeBlob *cb = CodeCache::find_blob(real_return_addr); 1011 assert(cb != NULL && cb->is_compiled(), "return address should be in nmethod"); 1012 CompiledMethod* nm = (CompiledMethod*)cb; 1013 1014 // Find frame of caller 1015 frame stub_fr = thread()->last_frame(); 1016 CodeBlob* stub_cb = stub_fr.cb(); 1017 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub"); 1018 RegisterMap map(thread(), true); 1019 frame caller_fr = stub_fr.sender(&map); 1020 1021 // Should only be poll_return or poll 1022 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" ); 1023 1024 // This is a poll immediately before a return. The exception handling code 1025 // has already had the effect of causing the return to occur, so the execution 1026 // will continue immediately after the call. In addition, the oopmap at the 1027 // return point does not mark the return value as an oop (if it is), so 1028 // it needs a handle here to be updated. 1029 if( nm->is_at_poll_return(real_return_addr) ) { 1030 // See if return type is an oop. 1031 bool return_oop = nm->method()->is_returning_oop(); 1032 Handle return_value; 1033 if (return_oop) { 1034 // The oop result has been saved on the stack together with all 1035 // the other registers. In order to preserve it over GCs we need 1036 // to keep it in a handle. 1037 oop result = caller_fr.saved_oop_result(&map); 1038 assert(result == NULL || result->is_oop(), "must be oop"); 1039 return_value = Handle(thread(), result); 1040 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer"); 1041 } 1042 1043 // Block the thread 1044 SafepointSynchronize::block(thread()); 1045 1046 // restore oop result, if any 1047 if (return_oop) { 1048 caller_fr.set_saved_oop_result(&map, return_value()); 1049 } 1050 } 1051 1052 // This is a safepoint poll. Verify the return address and block. 1053 else { 1054 set_at_poll_safepoint(true); 1055 1056 // verify the blob built the "return address" correctly 1057 assert(real_return_addr == caller_fr.pc(), "must match"); 1058 1059 // Block the thread 1060 SafepointSynchronize::block(thread()); 1061 set_at_poll_safepoint(false); 1062 1063 // If we have a pending async exception deoptimize the frame 1064 // as otherwise we may never deliver it. 1065 if (thread()->has_async_condition()) { 1066 ThreadInVMfromJavaNoAsyncException __tiv(thread()); 1067 Deoptimization::deoptimize_frame(thread(), caller_fr.id()); 1068 } 1069 1070 // If an exception has been installed we must check for a pending deoptimization 1071 // Deoptimize frame if exception has been thrown. 1072 1073 if (thread()->has_pending_exception() ) { 1074 RegisterMap map(thread(), true); 1075 frame caller_fr = stub_fr.sender(&map); 1076 if (caller_fr.is_deoptimized_frame()) { 1077 // The exception patch will destroy registers that are still 1078 // live and will be needed during deoptimization. Defer the 1079 // Async exception should have deferred the exception until the 1080 // next safepoint which will be detected when we get into 1081 // the interpreter so if we have an exception now things 1082 // are messed up. 1083 1084 fatal("Exception installed and deoptimization is pending"); 1085 } 1086 } 1087 } 1088 } 1089 1090 1091 // 1092 // Statistics & Instrumentations 1093 // 1094 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL; 1095 jlong SafepointSynchronize::_safepoint_begin_time = 0; 1096 int SafepointSynchronize::_cur_stat_index = 0; 1097 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating]; 1098 julong SafepointSynchronize::_coalesced_vmop_count = 0; 1099 jlong SafepointSynchronize::_max_sync_time = 0; 1100 jlong SafepointSynchronize::_max_vmop_time = 0; 1101 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f; 1102 1103 static jlong cleanup_end_time = 0; 1104 static bool need_to_track_page_armed_status = false; 1105 static bool init_done = false; 1106 1107 // Helper method to print the header. 1108 static void print_header() { 1109 // The number of spaces is significant here, and should match the format 1110 // specifiers in print_statistics(). 1111 1112 tty->print(" vmop " 1113 "[ threads: total initially_running wait_to_block ]" 1114 "[ time: spin block sync cleanup vmop ] "); 1115 1116 // no page armed status printed out if it is always armed. 1117 if (need_to_track_page_armed_status) { 1118 tty->print("page_armed "); 1119 } 1120 1121 tty->print_cr("page_trap_count"); 1122 } 1123 1124 void SafepointSynchronize::deferred_initialize_stat() { 1125 if (init_done) return; 1126 1127 // If PrintSafepointStatisticsTimeout is specified, the statistics data will 1128 // be printed right away, in which case, _safepoint_stats will regress to 1129 // a single element array. Otherwise, it is a circular ring buffer with default 1130 // size of PrintSafepointStatisticsCount. 1131 int stats_array_size; 1132 if (PrintSafepointStatisticsTimeout > 0) { 1133 stats_array_size = 1; 1134 PrintSafepointStatistics = true; 1135 } else { 1136 stats_array_size = PrintSafepointStatisticsCount; 1137 } 1138 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size 1139 * sizeof(SafepointStats), mtInternal); 1140 guarantee(_safepoint_stats != NULL, 1141 "not enough memory for safepoint instrumentation data"); 1142 1143 if (DeferPollingPageLoopCount >= 0) { 1144 need_to_track_page_armed_status = true; 1145 } 1146 init_done = true; 1147 } 1148 1149 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) { 1150 assert(init_done, "safepoint statistics array hasn't been initialized"); 1151 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1152 1153 spstat->_time_stamp = _ts_of_current_safepoint; 1154 1155 VM_Operation *op = VMThread::vm_operation(); 1156 spstat->_vmop_type = (op != NULL ? op->type() : -1); 1157 if (op != NULL) { 1158 _safepoint_reasons[spstat->_vmop_type]++; 1159 } 1160 1161 spstat->_nof_total_threads = nof_threads; 1162 spstat->_nof_initial_running_threads = nof_running; 1163 spstat->_nof_threads_hit_page_trap = 0; 1164 1165 // Records the start time of spinning. The real time spent on spinning 1166 // will be adjusted when spin is done. Same trick is applied for time 1167 // spent on waiting for threads to block. 1168 if (nof_running != 0) { 1169 spstat->_time_to_spin = os::javaTimeNanos(); 1170 } else { 1171 spstat->_time_to_spin = 0; 1172 } 1173 } 1174 1175 void SafepointSynchronize::update_statistics_on_spin_end() { 1176 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1177 1178 jlong cur_time = os::javaTimeNanos(); 1179 1180 spstat->_nof_threads_wait_to_block = _waiting_to_block; 1181 if (spstat->_nof_initial_running_threads != 0) { 1182 spstat->_time_to_spin = cur_time - spstat->_time_to_spin; 1183 } 1184 1185 if (need_to_track_page_armed_status) { 1186 spstat->_page_armed = (PageArmed == 1); 1187 } 1188 1189 // Records the start time of waiting for to block. Updated when block is done. 1190 if (_waiting_to_block != 0) { 1191 spstat->_time_to_wait_to_block = cur_time; 1192 } else { 1193 spstat->_time_to_wait_to_block = 0; 1194 } 1195 } 1196 1197 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) { 1198 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1199 1200 if (spstat->_nof_threads_wait_to_block != 0) { 1201 spstat->_time_to_wait_to_block = end_time - 1202 spstat->_time_to_wait_to_block; 1203 } 1204 1205 // Records the end time of sync which will be used to calculate the total 1206 // vm operation time. Again, the real time spending in syncing will be deducted 1207 // from the start of the sync time later when end_statistics is called. 1208 spstat->_time_to_sync = end_time - _safepoint_begin_time; 1209 if (spstat->_time_to_sync > _max_sync_time) { 1210 _max_sync_time = spstat->_time_to_sync; 1211 } 1212 1213 spstat->_time_to_do_cleanups = end_time; 1214 } 1215 1216 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) { 1217 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1218 1219 // Record how long spent in cleanup tasks. 1220 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups; 1221 1222 cleanup_end_time = end_time; 1223 } 1224 1225 void SafepointSynchronize::end_statistics(jlong vmop_end_time) { 1226 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1227 1228 // Update the vm operation time. 1229 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time; 1230 if (spstat->_time_to_exec_vmop > _max_vmop_time) { 1231 _max_vmop_time = spstat->_time_to_exec_vmop; 1232 } 1233 // Only the sync time longer than the specified 1234 // PrintSafepointStatisticsTimeout will be printed out right away. 1235 // By default, it is -1 meaning all samples will be put into the list. 1236 if ( PrintSafepointStatisticsTimeout > 0) { 1237 if (spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) { 1238 print_statistics(); 1239 } 1240 } else { 1241 // The safepoint statistics will be printed out when the _safepoin_stats 1242 // array fills up. 1243 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) { 1244 print_statistics(); 1245 _cur_stat_index = 0; 1246 } else { 1247 _cur_stat_index++; 1248 } 1249 } 1250 } 1251 1252 void SafepointSynchronize::print_statistics() { 1253 for (int index = 0; index <= _cur_stat_index; index++) { 1254 if (index % 30 == 0) { 1255 print_header(); 1256 } 1257 SafepointStats* sstats = &_safepoint_stats[index]; 1258 tty->print("%8.3f: ", sstats->_time_stamp); 1259 tty->print("%-30s [ " 1260 INT32_FORMAT_W(8) " " INT32_FORMAT_W(17) " " INT32_FORMAT_W(13) " " 1261 "]", 1262 (sstats->_vmop_type == -1 ? "no vm operation" : VM_Operation::name(sstats->_vmop_type)), 1263 sstats->_nof_total_threads, 1264 sstats->_nof_initial_running_threads, 1265 sstats->_nof_threads_wait_to_block); 1266 // "/ MICROUNITS " is to convert the unit from nanos to millis. 1267 tty->print("[ " 1268 INT64_FORMAT_W(7) " " INT64_FORMAT_W(7) " " 1269 INT64_FORMAT_W(7) " " INT64_FORMAT_W(7) " " 1270 INT64_FORMAT_W(7) " ] ", 1271 sstats->_time_to_spin / MICROUNITS, 1272 sstats->_time_to_wait_to_block / MICROUNITS, 1273 sstats->_time_to_sync / MICROUNITS, 1274 sstats->_time_to_do_cleanups / MICROUNITS, 1275 sstats->_time_to_exec_vmop / MICROUNITS); 1276 1277 if (need_to_track_page_armed_status) { 1278 tty->print(INT32_FORMAT_W(10) " ", sstats->_page_armed); 1279 } 1280 tty->print_cr(INT32_FORMAT_W(15) " ", sstats->_nof_threads_hit_page_trap); 1281 } 1282 } 1283 1284 // This method will be called when VM exits. It will first call 1285 // print_statistics to print out the rest of the sampling. Then 1286 // it tries to summarize the sampling. 1287 void SafepointSynchronize::print_stat_on_exit() { 1288 if (_safepoint_stats == NULL) return; 1289 1290 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1291 1292 // During VM exit, end_statistics may not get called and in that 1293 // case, if the sync time is less than PrintSafepointStatisticsTimeout, 1294 // don't print it out. 1295 // Approximate the vm op time. 1296 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop = 1297 os::javaTimeNanos() - cleanup_end_time; 1298 1299 if ( PrintSafepointStatisticsTimeout < 0 || 1300 spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) { 1301 print_statistics(); 1302 } 1303 tty->cr(); 1304 1305 // Print out polling page sampling status. 1306 if (!need_to_track_page_armed_status) { 1307 tty->print_cr("Polling page always armed"); 1308 } else { 1309 tty->print_cr("Defer polling page loop count = " INTX_FORMAT "\n", 1310 DeferPollingPageLoopCount); 1311 } 1312 1313 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) { 1314 if (_safepoint_reasons[index] != 0) { 1315 tty->print_cr("%-26s" UINT64_FORMAT_W(10), VM_Operation::name(index), 1316 _safepoint_reasons[index]); 1317 } 1318 } 1319 1320 tty->print_cr(UINT64_FORMAT_W(5) " VM operations coalesced during safepoint", 1321 _coalesced_vmop_count); 1322 tty->print_cr("Maximum sync time " INT64_FORMAT_W(5) " ms", 1323 _max_sync_time / MICROUNITS); 1324 tty->print_cr("Maximum vm operation time (except for Exit VM operation) " 1325 INT64_FORMAT_W(5) " ms", 1326 _max_vmop_time / MICROUNITS); 1327 } 1328 1329 // ------------------------------------------------------------------------------------------------ 1330 // Non-product code 1331 1332 #ifndef PRODUCT 1333 1334 void SafepointSynchronize::print_state() { 1335 if (_state == _not_synchronized) { 1336 tty->print_cr("not synchronized"); 1337 } else if (_state == _synchronizing || _state == _synchronized) { 1338 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" : 1339 "synchronized"); 1340 1341 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) { 1342 cur->safepoint_state()->print(); 1343 } 1344 } 1345 } 1346 1347 void SafepointSynchronize::safepoint_msg(const char* format, ...) { 1348 if (ShowSafepointMsgs) { 1349 va_list ap; 1350 va_start(ap, format); 1351 tty->vprint_cr(format, ap); 1352 va_end(ap); 1353 } 1354 } 1355 1356 #endif // !PRODUCT