1 /* 2 * Copyright (c) 1997, 2017, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #include "precompiled.hpp" 26 #include "classfile/stringTable.hpp" 27 #include "classfile/symbolTable.hpp" 28 #include "classfile/systemDictionary.hpp" 29 #include "code/codeCache.hpp" 30 #include "code/icBuffer.hpp" 31 #include "code/nmethod.hpp" 32 #include "code/pcDesc.hpp" 33 #include "code/scopeDesc.hpp" 34 #include "gc/shared/collectedHeap.hpp" 35 #include "gc/shared/gcLocker.inline.hpp" 36 #include "gc/shared/strongRootsScope.hpp" 37 #include "gc/shared/workgroup.hpp" 38 #include "interpreter/interpreter.hpp" 39 #include "logging/log.hpp" 40 #include "logging/logStream.hpp" 41 #include "memory/resourceArea.hpp" 42 #include "memory/universe.inline.hpp" 43 #include "oops/oop.inline.hpp" 44 #include "oops/symbol.hpp" 45 #include "runtime/atomic.hpp" 46 #include "runtime/compilationPolicy.hpp" 47 #include "runtime/deoptimization.hpp" 48 #include "runtime/frame.inline.hpp" 49 #include "runtime/interfaceSupport.hpp" 50 #include "runtime/mutexLocker.hpp" 51 #include "runtime/orderAccess.inline.hpp" 52 #include "runtime/osThread.hpp" 53 #include "runtime/safepoint.hpp" 54 #include "runtime/safepointMechanism.inline.hpp" 55 #include "runtime/signature.hpp" 56 #include "runtime/stubCodeGenerator.hpp" 57 #include "runtime/stubRoutines.hpp" 58 #include "runtime/sweeper.hpp" 59 #include "runtime/synchronizer.hpp" 60 #include "runtime/thread.inline.hpp" 61 #include "runtime/timerTrace.hpp" 62 #include "services/runtimeService.hpp" 63 #include "trace/tracing.hpp" 64 #include "trace/traceMacros.hpp" 65 #include "utilities/events.hpp" 66 #include "utilities/macros.hpp" 67 #ifdef COMPILER1 68 #include "c1/c1_globals.hpp" 69 #endif 70 71 // -------------------------------------------------------------------------------------------------- 72 // Implementation of Safepoint begin/end 73 74 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized; 75 volatile int SafepointSynchronize::_waiting_to_block = 0; 76 volatile int SafepointSynchronize::_safepoint_counter = 0; 77 int SafepointSynchronize::_current_jni_active_count = 0; 78 long SafepointSynchronize::_end_of_last_safepoint = 0; 79 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE 80 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only 81 static bool timeout_error_printed = false; 82 83 // Roll all threads forward to a safepoint and suspend them all 84 void SafepointSynchronize::begin() { 85 EventSafepointBegin begin_event; 86 Thread* myThread = Thread::current(); 87 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint"); 88 89 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) { 90 _safepoint_begin_time = os::javaTimeNanos(); 91 _ts_of_current_safepoint = tty->time_stamp().seconds(); 92 } 93 94 Universe::heap()->safepoint_synchronize_begin(); 95 96 // By getting the Threads_lock, we assure that no threads are about to start or 97 // exit. It is released again in SafepointSynchronize::end(). 98 Threads_lock->lock(); 99 100 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state"); 101 102 int nof_threads = Threads::number_of_threads(); 103 104 log_debug(safepoint)("Safepoint synchronization initiated. (%d)", nof_threads); 105 106 RuntimeService::record_safepoint_begin(); 107 108 MutexLocker mu(Safepoint_lock); 109 110 // Reset the count of active JNI critical threads 111 _current_jni_active_count = 0; 112 113 // Set number of threads to wait for, before we initiate the callbacks 114 _waiting_to_block = nof_threads; 115 TryingToBlock = 0 ; 116 int still_running = nof_threads; 117 118 // Save the starting time, so that it can be compared to see if this has taken 119 // too long to complete. 120 jlong safepoint_limit_time = 0; 121 timeout_error_printed = false; 122 123 // PrintSafepointStatisticsTimeout can be specified separately. When 124 // specified, PrintSafepointStatistics will be set to true in 125 // deferred_initialize_stat method. The initialization has to be done 126 // early enough to avoid any races. See bug 6880029 for details. 127 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) { 128 deferred_initialize_stat(); 129 } 130 131 // Begin the process of bringing the system to a safepoint. 132 // Java threads can be in several different states and are 133 // stopped by different mechanisms: 134 // 135 // 1. Running interpreted 136 // The interpreter dispatch table is changed to force it to 137 // check for a safepoint condition between bytecodes. 138 // 2. Running in native code 139 // When returning from the native code, a Java thread must check 140 // the safepoint _state to see if we must block. If the 141 // VM thread sees a Java thread in native, it does 142 // not wait for this thread to block. The order of the memory 143 // writes and reads of both the safepoint state and the Java 144 // threads state is critical. In order to guarantee that the 145 // memory writes are serialized with respect to each other, 146 // the VM thread issues a memory barrier instruction 147 // (on MP systems). In order to avoid the overhead of issuing 148 // a memory barrier for each Java thread making native calls, each Java 149 // thread performs a write to a single memory page after changing 150 // the thread state. The VM thread performs a sequence of 151 // mprotect OS calls which forces all previous writes from all 152 // Java threads to be serialized. This is done in the 153 // os::serialize_thread_states() call. This has proven to be 154 // much more efficient than executing a membar instruction 155 // on every call to native code. 156 // 3. Running compiled Code 157 // Compiled code reads a global (Safepoint Polling) page that 158 // is set to fault if we are trying to get to a safepoint. 159 // 4. Blocked 160 // A thread which is blocked will not be allowed to return from the 161 // block condition until the safepoint operation is complete. 162 // 5. In VM or Transitioning between states 163 // If a Java thread is currently running in the VM or transitioning 164 // between states, the safepointing code will wait for the thread to 165 // block itself when it attempts transitions to a new state. 166 // 167 { 168 EventSafepointStateSynchronization sync_event; 169 int initial_running = 0; 170 171 _state = _synchronizing; 172 173 if (SafepointMechanism::uses_thread_local_poll()) { 174 // Arming the per thread poll while having _state != _not_synchronized means safepointing 175 log_trace(safepoint)("Setting thread local yield flag for threads"); 176 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) { 177 // Make sure the threads start polling, it is time to yield. 178 SafepointMechanism::arm_local_poll(cur); // release store, global state -> local state 179 } 180 } 181 OrderAccess::fence(); // storestore|storeload, global state -> local state 182 183 // Flush all thread states to memory 184 if (!UseMembar) { 185 os::serialize_thread_states(); 186 } 187 188 if (SafepointMechanism::uses_global_page_poll()) { 189 // Make interpreter safepoint aware 190 Interpreter::notice_safepoints(); 191 192 if (DeferPollingPageLoopCount < 0) { 193 // Make polling safepoint aware 194 guarantee (PageArmed == 0, "invariant") ; 195 PageArmed = 1 ; 196 os::make_polling_page_unreadable(); 197 } 198 } 199 200 // Consider using active_processor_count() ... but that call is expensive. 201 int ncpus = os::processor_count() ; 202 203 #ifdef ASSERT 204 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) { 205 assert(cur->safepoint_state()->is_running(), "Illegal initial state"); 206 // Clear the visited flag to ensure that the critical counts are collected properly. 207 cur->set_visited_for_critical_count(false); 208 } 209 #endif // ASSERT 210 211 if (SafepointTimeout) 212 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS; 213 214 // Iterate through all threads until it have been determined how to stop them all at a safepoint 215 unsigned int iterations = 0; 216 int steps = 0 ; 217 while(still_running > 0) { 218 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) { 219 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended"); 220 ThreadSafepointState *cur_state = cur->safepoint_state(); 221 if (cur_state->is_running()) { 222 cur_state->examine_state_of_thread(); 223 if (!cur_state->is_running()) { 224 still_running--; 225 // consider adjusting steps downward: 226 // steps = 0 227 // steps -= NNN 228 // steps >>= 1 229 // steps = MIN(steps, 2000-100) 230 // if (iterations != 0) steps -= NNN 231 } 232 LogTarget(Trace, safepoint) lt; 233 if (lt.is_enabled()) { 234 ResourceMark rm; 235 LogStream ls(lt); 236 cur_state->print_on(&ls); 237 } 238 } 239 } 240 241 if (iterations == 0) { 242 initial_running = still_running; 243 if (PrintSafepointStatistics) { 244 begin_statistics(nof_threads, still_running); 245 } 246 } 247 248 if (still_running > 0) { 249 // Check for if it takes to long 250 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) { 251 print_safepoint_timeout(_spinning_timeout); 252 } 253 254 // Spin to avoid context switching. 255 // There's a tension between allowing the mutators to run (and rendezvous) 256 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that 257 // a mutator might otherwise use profitably to reach a safepoint. Excessive 258 // spinning by the VM thread on a saturated system can increase rendezvous latency. 259 // Blocking or yielding incur their own penalties in the form of context switching 260 // and the resultant loss of $ residency. 261 // 262 // Further complicating matters is that yield() does not work as naively expected 263 // on many platforms -- yield() does not guarantee that any other ready threads 264 // will run. As such we revert to naked_short_sleep() after some number of iterations. 265 // nakes_short_sleep() is implemented as a short unconditional sleep. 266 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping 267 // can actually increase the time it takes the VM thread to detect that a system-wide 268 // stop-the-world safepoint has been reached. In a pathological scenario such as that 269 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe. 270 // In that case the mutators will be stalled waiting for the safepoint to complete and the 271 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread 272 // will eventually wake up and detect that all mutators are safe, at which point 273 // we'll again make progress. 274 // 275 // Beware too that that the VMThread typically runs at elevated priority. 276 // Its default priority is higher than the default mutator priority. 277 // Obviously, this complicates spinning. 278 // 279 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0). 280 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will. 281 // 282 // See the comments in synchronizer.cpp for additional remarks on spinning. 283 // 284 // In the future we might: 285 // 1. Modify the safepoint scheme to avoid potentially unbounded spinning. 286 // This is tricky as the path used by a thread exiting the JVM (say on 287 // on JNI call-out) simply stores into its state field. The burden 288 // is placed on the VM thread, which must poll (spin). 289 // 2. Find something useful to do while spinning. If the safepoint is GC-related 290 // we might aggressively scan the stacks of threads that are already safe. 291 // 3. Use Solaris schedctl to examine the state of the still-running mutators. 292 // If all the mutators are ONPROC there's no reason to sleep or yield. 293 // 4. YieldTo() any still-running mutators that are ready but OFFPROC. 294 // 5. Check system saturation. If the system is not fully saturated then 295 // simply spin and avoid sleep/yield. 296 // 6. As still-running mutators rendezvous they could unpark the sleeping 297 // VMthread. This works well for still-running mutators that become 298 // safe. The VMthread must still poll for mutators that call-out. 299 // 7. Drive the policy on time-since-begin instead of iterations. 300 // 8. Consider making the spin duration a function of the # of CPUs: 301 // Spin = (((ncpus-1) * M) + K) + F(still_running) 302 // Alternately, instead of counting iterations of the outer loop 303 // we could count the # of threads visited in the inner loop, above. 304 // 9. On windows consider using the return value from SwitchThreadTo() 305 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions. 306 307 if (SafepointMechanism::uses_global_page_poll() && int(iterations) == DeferPollingPageLoopCount) { 308 guarantee (PageArmed == 0, "invariant") ; 309 PageArmed = 1 ; 310 os::make_polling_page_unreadable(); 311 } 312 313 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or 314 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus) 315 ++steps ; 316 if (ncpus > 1 && steps < SafepointSpinBeforeYield) { 317 SpinPause() ; // MP-Polite spin 318 } else 319 if (steps < DeferThrSuspendLoopCount) { 320 os::naked_yield() ; 321 } else { 322 os::naked_short_sleep(1); 323 } 324 325 iterations ++ ; 326 } 327 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long"); 328 } 329 assert(still_running == 0, "sanity check"); 330 331 if (PrintSafepointStatistics) { 332 update_statistics_on_spin_end(); 333 } 334 335 if (sync_event.should_commit()) { 336 // Group this event together with the ones committed after the counter is increased 337 sync_event.set_safepointId(safepoint_counter() + 1); 338 sync_event.set_initialThreadCount(initial_running); 339 sync_event.set_runningThreadCount(_waiting_to_block); 340 sync_event.set_iterations(iterations); 341 sync_event.commit(); 342 } 343 } //EventSafepointStateSync 344 345 // wait until all threads are stopped 346 { 347 EventSafepointWaitBlocked wait_blocked_event; 348 int initial_waiting_to_block = _waiting_to_block; 349 350 while (_waiting_to_block > 0) { 351 log_debug(safepoint)("Waiting for %d thread(s) to block", _waiting_to_block); 352 if (!SafepointTimeout || timeout_error_printed) { 353 Safepoint_lock->wait(true); // true, means with no safepoint checks 354 } else { 355 // Compute remaining time 356 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos(); 357 358 // If there is no remaining time, then there is an error 359 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) { 360 print_safepoint_timeout(_blocking_timeout); 361 } 362 } 363 } 364 assert(_waiting_to_block == 0, "sanity check"); 365 366 #ifndef PRODUCT 367 if (SafepointTimeout) { 368 jlong current_time = os::javaTimeNanos(); 369 if (safepoint_limit_time < current_time) { 370 tty->print_cr("# SafepointSynchronize: Finished after " 371 INT64_FORMAT_W(6) " ms", 372 (int64_t)((current_time - safepoint_limit_time) / MICROUNITS + 373 (jlong)SafepointTimeoutDelay)); 374 } 375 } 376 #endif 377 378 assert((_safepoint_counter & 0x1) == 0, "must be even"); 379 assert(Threads_lock->owned_by_self(), "must hold Threads_lock"); 380 _safepoint_counter ++; 381 382 // Record state 383 _state = _synchronized; 384 385 OrderAccess::fence(); 386 387 if (wait_blocked_event.should_commit()) { 388 wait_blocked_event.set_safepointId(safepoint_counter()); 389 wait_blocked_event.set_runningThreadCount(initial_waiting_to_block); 390 wait_blocked_event.commit(); 391 } 392 } // EventSafepointWaitBlocked 393 394 #ifdef ASSERT 395 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) { 396 // make sure all the threads were visited 397 assert(cur->was_visited_for_critical_count(), "missed a thread"); 398 } 399 #endif // ASSERT 400 401 // Update the count of active JNI critical regions 402 GCLocker::set_jni_lock_count(_current_jni_active_count); 403 404 if (log_is_enabled(Debug, safepoint)) { 405 log_debug(safepoint)("Entering safepoint region: %s", VMThread::vm_safepoint_description()); 406 } 407 408 RuntimeService::record_safepoint_synchronized(); 409 if (PrintSafepointStatistics) { 410 update_statistics_on_sync_end(os::javaTimeNanos()); 411 } 412 413 // Call stuff that needs to be run when a safepoint is just about to be completed 414 { 415 EventSafepointCleanup cleanup_event; 416 do_cleanup_tasks(); 417 if (cleanup_event.should_commit()) { 418 cleanup_event.set_safepointId(safepoint_counter()); 419 cleanup_event.commit(); 420 } 421 } 422 423 if (PrintSafepointStatistics) { 424 // Record how much time spend on the above cleanup tasks 425 update_statistics_on_cleanup_end(os::javaTimeNanos()); 426 } 427 if (begin_event.should_commit()) { 428 begin_event.set_safepointId(safepoint_counter()); 429 begin_event.set_totalThreadCount(nof_threads); 430 begin_event.set_jniCriticalThreadCount(_current_jni_active_count); 431 begin_event.commit(); 432 } 433 } 434 435 // Wake up all threads, so they are ready to resume execution after the safepoint 436 // operation has been carried out 437 void SafepointSynchronize::end() { 438 EventSafepointEnd event; 439 int safepoint_id = safepoint_counter(); // Keep the odd counter as "id" 440 441 assert(Threads_lock->owned_by_self(), "must hold Threads_lock"); 442 assert((_safepoint_counter & 0x1) == 1, "must be odd"); 443 _safepoint_counter ++; 444 // memory fence isn't required here since an odd _safepoint_counter 445 // value can do no harm and a fence is issued below anyway. 446 447 DEBUG_ONLY(Thread* myThread = Thread::current();) 448 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint"); 449 450 if (PrintSafepointStatistics) { 451 end_statistics(os::javaTimeNanos()); 452 } 453 454 #ifdef ASSERT 455 // A pending_exception cannot be installed during a safepoint. The threads 456 // may install an async exception after they come back from a safepoint into 457 // pending_exception after they unblock. But that should happen later. 458 for (JavaThread *cur = Threads::first(); cur; cur = cur->next()) { 459 assert (!(cur->has_pending_exception() && 460 cur->safepoint_state()->is_at_poll_safepoint()), 461 "safepoint installed a pending exception"); 462 } 463 #endif // ASSERT 464 465 if (PageArmed) { 466 assert(SafepointMechanism::uses_global_page_poll(), "sanity"); 467 // Make polling safepoint aware 468 os::make_polling_page_readable(); 469 PageArmed = 0 ; 470 } 471 472 if (SafepointMechanism::uses_global_page_poll()) { 473 // Remove safepoint check from interpreter 474 Interpreter::ignore_safepoints(); 475 } 476 477 { 478 MutexLocker mu(Safepoint_lock); 479 480 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization"); 481 482 if (SafepointMechanism::uses_thread_local_poll()) { 483 _state = _not_synchronized; 484 OrderAccess::storestore(); // global state -> local state 485 for (JavaThread *current = Threads::first(); current; current = current->next()) { 486 ThreadSafepointState* cur_state = current->safepoint_state(); 487 cur_state->restart(); // TSS _running 488 SafepointMechanism::disarm_local_poll(current); // release store, local state -> polling page 489 } 490 log_debug(safepoint)("Leaving safepoint region"); 491 } else { 492 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method 493 // when they get restarted. 494 _state = _not_synchronized; 495 OrderAccess::fence(); 496 497 log_debug(safepoint)("Leaving safepoint region"); 498 499 // Start suspended threads 500 for (JavaThread *current = Threads::first(); current; current = current->next()) { 501 // A problem occurring on Solaris is when attempting to restart threads 502 // the first #cpus - 1 go well, but then the VMThread is preempted when we get 503 // to the next one (since it has been running the longest). We then have 504 // to wait for a cpu to become available before we can continue restarting 505 // threads. 506 // FIXME: This causes the performance of the VM to degrade when active and with 507 // large numbers of threads. Apparently this is due to the synchronous nature 508 // of suspending threads. 509 // 510 // TODO-FIXME: the comments above are vestigial and no longer apply. 511 // Furthermore, using solaris' schedctl in this particular context confers no benefit 512 if (VMThreadHintNoPreempt) { 513 os::hint_no_preempt(); 514 } 515 ThreadSafepointState* cur_state = current->safepoint_state(); 516 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint"); 517 cur_state->restart(); 518 assert(cur_state->is_running(), "safepoint state has not been reset"); 519 } 520 } 521 522 RuntimeService::record_safepoint_end(); 523 524 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads 525 // blocked in signal_thread_blocked 526 Threads_lock->unlock(); 527 528 } 529 Universe::heap()->safepoint_synchronize_end(); 530 // record this time so VMThread can keep track how much time has elapsed 531 // since last safepoint. 532 _end_of_last_safepoint = os::javaTimeMillis(); 533 534 if (event.should_commit()) { 535 event.set_safepointId(safepoint_id); 536 event.commit(); 537 } 538 } 539 540 bool SafepointSynchronize::is_cleanup_needed() { 541 // Need a safepoint if there are many monitors to deflate. 542 if (ObjectSynchronizer::is_cleanup_needed()) return true; 543 // Need a safepoint if some inline cache buffers is non-empty 544 if (!InlineCacheBuffer::is_empty()) return true; 545 return false; 546 } 547 548 static void event_safepoint_cleanup_task_commit(EventSafepointCleanupTask& event, const char* name) { 549 if (event.should_commit()) { 550 event.set_safepointId(SafepointSynchronize::safepoint_counter()); 551 event.set_name(name); 552 event.commit(); 553 } 554 } 555 556 class ParallelSPCleanupThreadClosure : public ThreadClosure { 557 private: 558 CodeBlobClosure* _nmethod_cl; 559 DeflateMonitorCounters* _counters; 560 561 public: 562 ParallelSPCleanupThreadClosure(DeflateMonitorCounters* counters) : 563 _counters(counters), 564 _nmethod_cl(NMethodSweeper::prepare_mark_active_nmethods()) {} 565 566 void do_thread(Thread* thread) { 567 ObjectSynchronizer::deflate_thread_local_monitors(thread, _counters); 568 if (_nmethod_cl != NULL && thread->is_Java_thread() && 569 ! thread->is_Code_cache_sweeper_thread()) { 570 JavaThread* jt = (JavaThread*) thread; 571 jt->nmethods_do(_nmethod_cl); 572 } 573 } 574 }; 575 576 class ParallelSPCleanupTask : public AbstractGangTask { 577 private: 578 SubTasksDone _subtasks; 579 ParallelSPCleanupThreadClosure _cleanup_threads_cl; 580 uint _num_workers; 581 DeflateMonitorCounters* _counters; 582 public: 583 ParallelSPCleanupTask(uint num_workers, DeflateMonitorCounters* counters) : 584 AbstractGangTask("Parallel Safepoint Cleanup"), 585 _cleanup_threads_cl(ParallelSPCleanupThreadClosure(counters)), 586 _num_workers(num_workers), 587 _subtasks(SubTasksDone(SafepointSynchronize::SAFEPOINT_CLEANUP_NUM_TASKS)), 588 _counters(counters) {} 589 590 void work(uint worker_id) { 591 // All threads deflate monitors and mark nmethods (if necessary). 592 Threads::possibly_parallel_threads_do(true, &_cleanup_threads_cl); 593 594 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_DEFLATE_MONITORS)) { 595 const char* name = "deflating idle monitors"; 596 EventSafepointCleanupTask event; 597 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup)); 598 ObjectSynchronizer::deflate_idle_monitors(_counters); 599 event_safepoint_cleanup_task_commit(event, name); 600 } 601 602 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_UPDATE_INLINE_CACHES)) { 603 const char* name = "updating inline caches"; 604 EventSafepointCleanupTask event; 605 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup)); 606 InlineCacheBuffer::update_inline_caches(); 607 event_safepoint_cleanup_task_commit(event, name); 608 } 609 610 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_COMPILATION_POLICY)) { 611 const char* name = "compilation policy safepoint handler"; 612 EventSafepointCleanupTask event; 613 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup)); 614 CompilationPolicy::policy()->do_safepoint_work(); 615 event_safepoint_cleanup_task_commit(event, name); 616 } 617 618 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_SYMBOL_TABLE_REHASH)) { 619 if (SymbolTable::needs_rehashing()) { 620 const char* name = "rehashing symbol table"; 621 EventSafepointCleanupTask event; 622 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup)); 623 SymbolTable::rehash_table(); 624 event_safepoint_cleanup_task_commit(event, name); 625 } 626 } 627 628 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_STRING_TABLE_REHASH)) { 629 if (StringTable::needs_rehashing()) { 630 const char* name = "rehashing string table"; 631 EventSafepointCleanupTask event; 632 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup)); 633 StringTable::rehash_table(); 634 event_safepoint_cleanup_task_commit(event, name); 635 } 636 } 637 638 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_CLD_PURGE)) { 639 // CMS delays purging the CLDG until the beginning of the next safepoint and to 640 // make sure concurrent sweep is done 641 const char* name = "purging class loader data graph"; 642 EventSafepointCleanupTask event; 643 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup)); 644 ClassLoaderDataGraph::purge_if_needed(); 645 event_safepoint_cleanup_task_commit(event, name); 646 } 647 _subtasks.all_tasks_completed(_num_workers); 648 } 649 }; 650 651 // Various cleaning tasks that should be done periodically at safepoints. 652 void SafepointSynchronize::do_cleanup_tasks() { 653 654 TraceTime timer("safepoint cleanup tasks", TRACETIME_LOG(Info, safepoint, cleanup)); 655 656 // Prepare for monitor deflation. 657 DeflateMonitorCounters deflate_counters; 658 ObjectSynchronizer::prepare_deflate_idle_monitors(&deflate_counters); 659 660 CollectedHeap* heap = Universe::heap(); 661 assert(heap != NULL, "heap not initialized yet?"); 662 WorkGang* cleanup_workers = heap->get_safepoint_workers(); 663 if (cleanup_workers != NULL) { 664 // Parallel cleanup using GC provided thread pool. 665 uint num_cleanup_workers = cleanup_workers->active_workers(); 666 ParallelSPCleanupTask cleanup(num_cleanup_workers, &deflate_counters); 667 StrongRootsScope srs(num_cleanup_workers); 668 cleanup_workers->run_task(&cleanup); 669 } else { 670 // Serial cleanup using VMThread. 671 ParallelSPCleanupTask cleanup(1, &deflate_counters); 672 StrongRootsScope srs(1); 673 cleanup.work(0); 674 } 675 676 // Finish monitor deflation. 677 ObjectSynchronizer::finish_deflate_idle_monitors(&deflate_counters); 678 } 679 680 681 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) { 682 switch(state) { 683 case _thread_in_native: 684 // native threads are safe if they have no java stack or have walkable stack 685 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable(); 686 687 // blocked threads should have already have walkable stack 688 case _thread_blocked: 689 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable"); 690 return true; 691 692 default: 693 return false; 694 } 695 } 696 697 698 // See if the thread is running inside a lazy critical native and 699 // update the thread critical count if so. Also set a suspend flag to 700 // cause the native wrapper to return into the JVM to do the unlock 701 // once the native finishes. 702 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) { 703 if (state == _thread_in_native && 704 thread->has_last_Java_frame() && 705 thread->frame_anchor()->walkable()) { 706 // This thread might be in a critical native nmethod so look at 707 // the top of the stack and increment the critical count if it 708 // is. 709 frame wrapper_frame = thread->last_frame(); 710 CodeBlob* stub_cb = wrapper_frame.cb(); 711 if (stub_cb != NULL && 712 stub_cb->is_nmethod() && 713 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) { 714 // A thread could potentially be in a critical native across 715 // more than one safepoint, so only update the critical state on 716 // the first one. When it returns it will perform the unlock. 717 if (!thread->do_critical_native_unlock()) { 718 #ifdef ASSERT 719 if (!thread->in_critical()) { 720 GCLocker::increment_debug_jni_lock_count(); 721 } 722 #endif 723 thread->enter_critical(); 724 // Make sure the native wrapper calls back on return to 725 // perform the needed critical unlock. 726 thread->set_critical_native_unlock(); 727 } 728 } 729 } 730 } 731 732 733 734 // ------------------------------------------------------------------------------------------------------- 735 // Implementation of Safepoint callback point 736 737 void SafepointSynchronize::block(JavaThread *thread) { 738 assert(thread != NULL, "thread must be set"); 739 assert(thread->is_Java_thread(), "not a Java thread"); 740 741 // Threads shouldn't block if they are in the middle of printing, but... 742 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id()); 743 744 // Only bail from the block() call if the thread is gone from the 745 // thread list; starting to exit should still block. 746 if (thread->is_terminated()) { 747 // block current thread if we come here from native code when VM is gone 748 thread->block_if_vm_exited(); 749 750 // otherwise do nothing 751 return; 752 } 753 754 JavaThreadState state = thread->thread_state(); 755 thread->frame_anchor()->make_walkable(thread); 756 757 // Check that we have a valid thread_state at this point 758 switch(state) { 759 case _thread_in_vm_trans: 760 case _thread_in_Java: // From compiled code 761 762 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case, 763 // we pretend we are still in the VM. 764 thread->set_thread_state(_thread_in_vm); 765 766 if (is_synchronizing()) { 767 Atomic::inc (&TryingToBlock) ; 768 } 769 770 // We will always be holding the Safepoint_lock when we are examine the state 771 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and 772 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code 773 Safepoint_lock->lock_without_safepoint_check(); 774 if (is_synchronizing()) { 775 // Decrement the number of threads to wait for and signal vm thread 776 assert(_waiting_to_block > 0, "sanity check"); 777 _waiting_to_block--; 778 thread->safepoint_state()->set_has_called_back(true); 779 780 DEBUG_ONLY(thread->set_visited_for_critical_count(true)); 781 if (thread->in_critical()) { 782 // Notice that this thread is in a critical section 783 increment_jni_active_count(); 784 } 785 786 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread 787 if (_waiting_to_block == 0) { 788 Safepoint_lock->notify_all(); 789 } 790 } 791 792 // We transition the thread to state _thread_blocked here, but 793 // we can't do our usual check for external suspension and then 794 // self-suspend after the lock_without_safepoint_check() call 795 // below because we are often called during transitions while 796 // we hold different locks. That would leave us suspended while 797 // holding a resource which results in deadlocks. 798 thread->set_thread_state(_thread_blocked); 799 Safepoint_lock->unlock(); 800 801 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during 802 // the entire safepoint, the threads will all line up here during the safepoint. 803 Threads_lock->lock_without_safepoint_check(); 804 // restore original state. This is important if the thread comes from compiled code, so it 805 // will continue to execute with the _thread_in_Java state. 806 thread->set_thread_state(state); 807 Threads_lock->unlock(); 808 break; 809 810 case _thread_in_native_trans: 811 case _thread_blocked_trans: 812 case _thread_new_trans: 813 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) { 814 thread->print_thread_state(); 815 fatal("Deadlock in safepoint code. " 816 "Should have called back to the VM before blocking."); 817 } 818 819 // We transition the thread to state _thread_blocked here, but 820 // we can't do our usual check for external suspension and then 821 // self-suspend after the lock_without_safepoint_check() call 822 // below because we are often called during transitions while 823 // we hold different locks. That would leave us suspended while 824 // holding a resource which results in deadlocks. 825 thread->set_thread_state(_thread_blocked); 826 827 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence, 828 // the safepoint code might still be waiting for it to block. We need to change the state here, 829 // so it can see that it is at a safepoint. 830 831 // Block until the safepoint operation is completed. 832 Threads_lock->lock_without_safepoint_check(); 833 834 // Restore state 835 thread->set_thread_state(state); 836 837 Threads_lock->unlock(); 838 break; 839 840 default: 841 fatal("Illegal threadstate encountered: %d", state); 842 } 843 844 // Check for pending. async. exceptions or suspends - except if the 845 // thread was blocked inside the VM. has_special_runtime_exit_condition() 846 // is called last since it grabs a lock and we only want to do that when 847 // we must. 848 // 849 // Note: we never deliver an async exception at a polling point as the 850 // compiler may not have an exception handler for it. The polling 851 // code will notice the async and deoptimize and the exception will 852 // be delivered. (Polling at a return point is ok though). Sure is 853 // a lot of bother for a deprecated feature... 854 // 855 // We don't deliver an async exception if the thread state is 856 // _thread_in_native_trans so JNI functions won't be called with 857 // a surprising pending exception. If the thread state is going back to java, 858 // async exception is checked in check_special_condition_for_native_trans(). 859 860 if (state != _thread_blocked_trans && 861 state != _thread_in_vm_trans && 862 thread->has_special_runtime_exit_condition()) { 863 thread->handle_special_runtime_exit_condition( 864 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans)); 865 } 866 } 867 868 // ------------------------------------------------------------------------------------------------------ 869 // Exception handlers 870 871 872 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) { 873 assert(thread->is_Java_thread(), "polling reference encountered by VM thread"); 874 assert(thread->thread_state() == _thread_in_Java, "should come from Java code"); 875 if (!ThreadLocalHandshakes) { 876 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization"); 877 } 878 879 if (ShowSafepointMsgs) { 880 tty->print("handle_polling_page_exception: "); 881 } 882 883 if (PrintSafepointStatistics) { 884 inc_page_trap_count(); 885 } 886 887 ThreadSafepointState* state = thread->safepoint_state(); 888 889 state->handle_polling_page_exception(); 890 } 891 892 893 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) { 894 if (!timeout_error_printed) { 895 timeout_error_printed = true; 896 // Print out the thread info which didn't reach the safepoint for debugging 897 // purposes (useful when there are lots of threads in the debugger). 898 tty->cr(); 899 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:"); 900 if (reason == _spinning_timeout) { 901 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint."); 902 } else if (reason == _blocking_timeout) { 903 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop."); 904 } 905 906 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:"); 907 ThreadSafepointState *cur_state; 908 ResourceMark rm; 909 for (JavaThread *cur_thread = Threads::first(); cur_thread; 910 cur_thread = cur_thread->next()) { 911 cur_state = cur_thread->safepoint_state(); 912 913 if (cur_thread->thread_state() != _thread_blocked && 914 ((reason == _spinning_timeout && cur_state->is_running()) || 915 (reason == _blocking_timeout && !cur_state->has_called_back()))) { 916 tty->print("# "); 917 cur_thread->print(); 918 tty->cr(); 919 } 920 } 921 tty->print_cr("# SafepointSynchronize::begin: (End of list)"); 922 } 923 924 // To debug the long safepoint, specify both DieOnSafepointTimeout & 925 // ShowMessageBoxOnError. 926 if (DieOnSafepointTimeout) { 927 fatal("Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.", 928 SafepointTimeoutDelay, VMThread::vm_safepoint_description()); 929 } 930 } 931 932 933 // ------------------------------------------------------------------------------------------------------- 934 // Implementation of ThreadSafepointState 935 936 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) { 937 _thread = thread; 938 _type = _running; 939 _has_called_back = false; 940 _at_poll_safepoint = false; 941 } 942 943 void ThreadSafepointState::create(JavaThread *thread) { 944 ThreadSafepointState *state = new ThreadSafepointState(thread); 945 thread->set_safepoint_state(state); 946 } 947 948 void ThreadSafepointState::destroy(JavaThread *thread) { 949 if (thread->safepoint_state()) { 950 delete(thread->safepoint_state()); 951 thread->set_safepoint_state(NULL); 952 } 953 } 954 955 void ThreadSafepointState::examine_state_of_thread() { 956 assert(is_running(), "better be running or just have hit safepoint poll"); 957 958 JavaThreadState state = _thread->thread_state(); 959 960 // Save the state at the start of safepoint processing. 961 _orig_thread_state = state; 962 963 // Check for a thread that is suspended. Note that thread resume tries 964 // to grab the Threads_lock which we own here, so a thread cannot be 965 // resumed during safepoint synchronization. 966 967 // We check to see if this thread is suspended without locking to 968 // avoid deadlocking with a third thread that is waiting for this 969 // thread to be suspended. The third thread can notice the safepoint 970 // that we're trying to start at the beginning of its SR_lock->wait() 971 // call. If that happens, then the third thread will block on the 972 // safepoint while still holding the underlying SR_lock. We won't be 973 // able to get the SR_lock and we'll deadlock. 974 // 975 // We don't need to grab the SR_lock here for two reasons: 976 // 1) The suspend flags are both volatile and are set with an 977 // Atomic::cmpxchg() call so we should see the suspended 978 // state right away. 979 // 2) We're being called from the safepoint polling loop; if 980 // we don't see the suspended state on this iteration, then 981 // we'll come around again. 982 // 983 bool is_suspended = _thread->is_ext_suspended(); 984 if (is_suspended) { 985 roll_forward(_at_safepoint); 986 return; 987 } 988 989 // Some JavaThread states have an initial safepoint state of 990 // running, but are actually at a safepoint. We will happily 991 // agree and update the safepoint state here. 992 if (SafepointSynchronize::safepoint_safe(_thread, state)) { 993 SafepointSynchronize::check_for_lazy_critical_native(_thread, state); 994 roll_forward(_at_safepoint); 995 return; 996 } 997 998 if (state == _thread_in_vm) { 999 roll_forward(_call_back); 1000 return; 1001 } 1002 1003 // All other thread states will continue to run until they 1004 // transition and self-block in state _blocked 1005 // Safepoint polling in compiled code causes the Java threads to do the same. 1006 // Note: new threads may require a malloc so they must be allowed to finish 1007 1008 assert(is_running(), "examine_state_of_thread on non-running thread"); 1009 return; 1010 } 1011 1012 // Returns true is thread could not be rolled forward at present position. 1013 void ThreadSafepointState::roll_forward(suspend_type type) { 1014 _type = type; 1015 1016 switch(_type) { 1017 case _at_safepoint: 1018 SafepointSynchronize::signal_thread_at_safepoint(); 1019 DEBUG_ONLY(_thread->set_visited_for_critical_count(true)); 1020 if (_thread->in_critical()) { 1021 // Notice that this thread is in a critical section 1022 SafepointSynchronize::increment_jni_active_count(); 1023 } 1024 break; 1025 1026 case _call_back: 1027 set_has_called_back(false); 1028 break; 1029 1030 case _running: 1031 default: 1032 ShouldNotReachHere(); 1033 } 1034 } 1035 1036 void ThreadSafepointState::restart() { 1037 switch(type()) { 1038 case _at_safepoint: 1039 case _call_back: 1040 break; 1041 1042 case _running: 1043 default: 1044 tty->print_cr("restart thread " INTPTR_FORMAT " with state %d", 1045 p2i(_thread), _type); 1046 _thread->print(); 1047 ShouldNotReachHere(); 1048 } 1049 _type = _running; 1050 set_has_called_back(false); 1051 } 1052 1053 1054 void ThreadSafepointState::print_on(outputStream *st) const { 1055 const char *s = NULL; 1056 1057 switch(_type) { 1058 case _running : s = "_running"; break; 1059 case _at_safepoint : s = "_at_safepoint"; break; 1060 case _call_back : s = "_call_back"; break; 1061 default: 1062 ShouldNotReachHere(); 1063 } 1064 1065 st->print_cr("Thread: " INTPTR_FORMAT 1066 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d", 1067 p2i(_thread), _thread->osthread()->thread_id(), s, _has_called_back, 1068 _at_poll_safepoint); 1069 1070 _thread->print_thread_state_on(st); 1071 } 1072 1073 // --------------------------------------------------------------------------------------------------------------------- 1074 1075 // Block the thread at poll or poll return for safepoint/handshake. 1076 void ThreadSafepointState::handle_polling_page_exception() { 1077 1078 // Check state. block() will set thread state to thread_in_vm which will 1079 // cause the safepoint state _type to become _call_back. 1080 suspend_type t = type(); 1081 assert(!SafepointMechanism::uses_global_page_poll() || t == ThreadSafepointState::_running, 1082 "polling page exception on thread not running state: %u", uint(t)); 1083 1084 // Step 1: Find the nmethod from the return address 1085 if (ShowSafepointMsgs && Verbose) { 1086 tty->print_cr("Polling page exception at " INTPTR_FORMAT, p2i(thread()->saved_exception_pc())); 1087 } 1088 address real_return_addr = thread()->saved_exception_pc(); 1089 1090 CodeBlob *cb = CodeCache::find_blob(real_return_addr); 1091 assert(cb != NULL && cb->is_compiled(), "return address should be in nmethod"); 1092 CompiledMethod* nm = (CompiledMethod*)cb; 1093 1094 // Find frame of caller 1095 frame stub_fr = thread()->last_frame(); 1096 CodeBlob* stub_cb = stub_fr.cb(); 1097 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub"); 1098 RegisterMap map(thread(), true); 1099 frame caller_fr = stub_fr.sender(&map); 1100 1101 // Should only be poll_return or poll 1102 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" ); 1103 1104 // This is a poll immediately before a return. The exception handling code 1105 // has already had the effect of causing the return to occur, so the execution 1106 // will continue immediately after the call. In addition, the oopmap at the 1107 // return point does not mark the return value as an oop (if it is), so 1108 // it needs a handle here to be updated. 1109 if( nm->is_at_poll_return(real_return_addr) ) { 1110 // See if return type is an oop. 1111 bool return_oop = nm->method()->is_returning_oop(); 1112 Handle return_value; 1113 if (return_oop) { 1114 // The oop result has been saved on the stack together with all 1115 // the other registers. In order to preserve it over GCs we need 1116 // to keep it in a handle. 1117 oop result = caller_fr.saved_oop_result(&map); 1118 assert(oopDesc::is_oop_or_null(result), "must be oop"); 1119 return_value = Handle(thread(), result); 1120 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer"); 1121 } 1122 1123 // Block the thread 1124 SafepointMechanism::block_if_requested(thread()); 1125 1126 // restore oop result, if any 1127 if (return_oop) { 1128 caller_fr.set_saved_oop_result(&map, return_value()); 1129 } 1130 } 1131 1132 // This is a safepoint poll. Verify the return address and block. 1133 else { 1134 set_at_poll_safepoint(true); 1135 1136 // verify the blob built the "return address" correctly 1137 assert(real_return_addr == caller_fr.pc(), "must match"); 1138 1139 // Block the thread 1140 SafepointMechanism::block_if_requested(thread()); 1141 set_at_poll_safepoint(false); 1142 1143 // If we have a pending async exception deoptimize the frame 1144 // as otherwise we may never deliver it. 1145 if (thread()->has_async_condition()) { 1146 ThreadInVMfromJavaNoAsyncException __tiv(thread()); 1147 Deoptimization::deoptimize_frame(thread(), caller_fr.id()); 1148 } 1149 1150 // If an exception has been installed we must check for a pending deoptimization 1151 // Deoptimize frame if exception has been thrown. 1152 1153 if (thread()->has_pending_exception() ) { 1154 RegisterMap map(thread(), true); 1155 frame caller_fr = stub_fr.sender(&map); 1156 if (caller_fr.is_deoptimized_frame()) { 1157 // The exception patch will destroy registers that are still 1158 // live and will be needed during deoptimization. Defer the 1159 // Async exception should have deferred the exception until the 1160 // next safepoint which will be detected when we get into 1161 // the interpreter so if we have an exception now things 1162 // are messed up. 1163 1164 fatal("Exception installed and deoptimization is pending"); 1165 } 1166 } 1167 } 1168 } 1169 1170 1171 // 1172 // Statistics & Instrumentations 1173 // 1174 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL; 1175 jlong SafepointSynchronize::_safepoint_begin_time = 0; 1176 int SafepointSynchronize::_cur_stat_index = 0; 1177 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating]; 1178 julong SafepointSynchronize::_coalesced_vmop_count = 0; 1179 jlong SafepointSynchronize::_max_sync_time = 0; 1180 jlong SafepointSynchronize::_max_vmop_time = 0; 1181 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f; 1182 1183 static jlong cleanup_end_time = 0; 1184 static bool need_to_track_page_armed_status = false; 1185 static bool init_done = false; 1186 1187 // Helper method to print the header. 1188 static void print_header() { 1189 // The number of spaces is significant here, and should match the format 1190 // specifiers in print_statistics(). 1191 1192 tty->print(" vmop " 1193 "[ threads: total initially_running wait_to_block ]" 1194 "[ time: spin block sync cleanup vmop ] "); 1195 1196 // no page armed status printed out if it is always armed. 1197 if (need_to_track_page_armed_status) { 1198 tty->print("page_armed "); 1199 } 1200 1201 tty->print_cr("page_trap_count"); 1202 } 1203 1204 void SafepointSynchronize::deferred_initialize_stat() { 1205 if (init_done) return; 1206 1207 // If PrintSafepointStatisticsTimeout is specified, the statistics data will 1208 // be printed right away, in which case, _safepoint_stats will regress to 1209 // a single element array. Otherwise, it is a circular ring buffer with default 1210 // size of PrintSafepointStatisticsCount. 1211 int stats_array_size; 1212 if (PrintSafepointStatisticsTimeout > 0) { 1213 stats_array_size = 1; 1214 PrintSafepointStatistics = true; 1215 } else { 1216 stats_array_size = PrintSafepointStatisticsCount; 1217 } 1218 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size 1219 * sizeof(SafepointStats), mtInternal); 1220 guarantee(_safepoint_stats != NULL, 1221 "not enough memory for safepoint instrumentation data"); 1222 1223 if (DeferPollingPageLoopCount >= 0) { 1224 need_to_track_page_armed_status = true; 1225 } 1226 init_done = true; 1227 } 1228 1229 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) { 1230 assert(init_done, "safepoint statistics array hasn't been initialized"); 1231 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1232 1233 spstat->_time_stamp = _ts_of_current_safepoint; 1234 1235 VM_Operation *op = VMThread::vm_operation(); 1236 spstat->_vmop_type = (op != NULL ? op->type() : -1); 1237 if (op != NULL) { 1238 _safepoint_reasons[spstat->_vmop_type]++; 1239 } 1240 1241 spstat->_nof_total_threads = nof_threads; 1242 spstat->_nof_initial_running_threads = nof_running; 1243 spstat->_nof_threads_hit_page_trap = 0; 1244 1245 // Records the start time of spinning. The real time spent on spinning 1246 // will be adjusted when spin is done. Same trick is applied for time 1247 // spent on waiting for threads to block. 1248 if (nof_running != 0) { 1249 spstat->_time_to_spin = os::javaTimeNanos(); 1250 } else { 1251 spstat->_time_to_spin = 0; 1252 } 1253 } 1254 1255 void SafepointSynchronize::update_statistics_on_spin_end() { 1256 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1257 1258 jlong cur_time = os::javaTimeNanos(); 1259 1260 spstat->_nof_threads_wait_to_block = _waiting_to_block; 1261 if (spstat->_nof_initial_running_threads != 0) { 1262 spstat->_time_to_spin = cur_time - spstat->_time_to_spin; 1263 } 1264 1265 if (need_to_track_page_armed_status) { 1266 spstat->_page_armed = (PageArmed == 1); 1267 } 1268 1269 // Records the start time of waiting for to block. Updated when block is done. 1270 if (_waiting_to_block != 0) { 1271 spstat->_time_to_wait_to_block = cur_time; 1272 } else { 1273 spstat->_time_to_wait_to_block = 0; 1274 } 1275 } 1276 1277 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) { 1278 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1279 1280 if (spstat->_nof_threads_wait_to_block != 0) { 1281 spstat->_time_to_wait_to_block = end_time - 1282 spstat->_time_to_wait_to_block; 1283 } 1284 1285 // Records the end time of sync which will be used to calculate the total 1286 // vm operation time. Again, the real time spending in syncing will be deducted 1287 // from the start of the sync time later when end_statistics is called. 1288 spstat->_time_to_sync = end_time - _safepoint_begin_time; 1289 if (spstat->_time_to_sync > _max_sync_time) { 1290 _max_sync_time = spstat->_time_to_sync; 1291 } 1292 1293 spstat->_time_to_do_cleanups = end_time; 1294 } 1295 1296 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) { 1297 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1298 1299 // Record how long spent in cleanup tasks. 1300 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups; 1301 1302 cleanup_end_time = end_time; 1303 } 1304 1305 void SafepointSynchronize::end_statistics(jlong vmop_end_time) { 1306 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1307 1308 // Update the vm operation time. 1309 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time; 1310 if (spstat->_time_to_exec_vmop > _max_vmop_time) { 1311 _max_vmop_time = spstat->_time_to_exec_vmop; 1312 } 1313 // Only the sync time longer than the specified 1314 // PrintSafepointStatisticsTimeout will be printed out right away. 1315 // By default, it is -1 meaning all samples will be put into the list. 1316 if ( PrintSafepointStatisticsTimeout > 0) { 1317 if (spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) { 1318 print_statistics(); 1319 } 1320 } else { 1321 // The safepoint statistics will be printed out when the _safepoin_stats 1322 // array fills up. 1323 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) { 1324 print_statistics(); 1325 _cur_stat_index = 0; 1326 } else { 1327 _cur_stat_index++; 1328 } 1329 } 1330 } 1331 1332 void SafepointSynchronize::print_statistics() { 1333 for (int index = 0; index <= _cur_stat_index; index++) { 1334 if (index % 30 == 0) { 1335 print_header(); 1336 } 1337 SafepointStats* sstats = &_safepoint_stats[index]; 1338 tty->print("%8.3f: ", sstats->_time_stamp); 1339 tty->print("%-30s [ " 1340 INT32_FORMAT_W(8) " " INT32_FORMAT_W(17) " " INT32_FORMAT_W(13) " " 1341 "]", 1342 (sstats->_vmop_type == -1 ? "no vm operation" : VM_Operation::name(sstats->_vmop_type)), 1343 sstats->_nof_total_threads, 1344 sstats->_nof_initial_running_threads, 1345 sstats->_nof_threads_wait_to_block); 1346 // "/ MICROUNITS " is to convert the unit from nanos to millis. 1347 tty->print("[ " 1348 INT64_FORMAT_W(7) " " INT64_FORMAT_W(7) " " 1349 INT64_FORMAT_W(7) " " INT64_FORMAT_W(7) " " 1350 INT64_FORMAT_W(7) " ] ", 1351 (int64_t)(sstats->_time_to_spin / MICROUNITS), 1352 (int64_t)(sstats->_time_to_wait_to_block / MICROUNITS), 1353 (int64_t)(sstats->_time_to_sync / MICROUNITS), 1354 (int64_t)(sstats->_time_to_do_cleanups / MICROUNITS), 1355 (int64_t)(sstats->_time_to_exec_vmop / MICROUNITS)); 1356 1357 if (need_to_track_page_armed_status) { 1358 tty->print(INT32_FORMAT_W(10) " ", sstats->_page_armed); 1359 } 1360 tty->print_cr(INT32_FORMAT_W(15) " ", sstats->_nof_threads_hit_page_trap); 1361 } 1362 } 1363 1364 // This method will be called when VM exits. It will first call 1365 // print_statistics to print out the rest of the sampling. Then 1366 // it tries to summarize the sampling. 1367 void SafepointSynchronize::print_stat_on_exit() { 1368 if (_safepoint_stats == NULL) return; 1369 1370 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1371 1372 // During VM exit, end_statistics may not get called and in that 1373 // case, if the sync time is less than PrintSafepointStatisticsTimeout, 1374 // don't print it out. 1375 // Approximate the vm op time. 1376 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop = 1377 os::javaTimeNanos() - cleanup_end_time; 1378 1379 if ( PrintSafepointStatisticsTimeout < 0 || 1380 spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) { 1381 print_statistics(); 1382 } 1383 tty->cr(); 1384 1385 // Print out polling page sampling status. 1386 if (!need_to_track_page_armed_status) { 1387 tty->print_cr("Polling page always armed"); 1388 } else { 1389 tty->print_cr("Defer polling page loop count = " INTX_FORMAT "\n", 1390 DeferPollingPageLoopCount); 1391 } 1392 1393 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) { 1394 if (_safepoint_reasons[index] != 0) { 1395 tty->print_cr("%-26s" UINT64_FORMAT_W(10), VM_Operation::name(index), 1396 _safepoint_reasons[index]); 1397 } 1398 } 1399 1400 tty->print_cr(UINT64_FORMAT_W(5) " VM operations coalesced during safepoint", 1401 _coalesced_vmop_count); 1402 tty->print_cr("Maximum sync time " INT64_FORMAT_W(5) " ms", 1403 (int64_t)(_max_sync_time / MICROUNITS)); 1404 tty->print_cr("Maximum vm operation time (except for Exit VM operation) " 1405 INT64_FORMAT_W(5) " ms", 1406 (int64_t)(_max_vmop_time / MICROUNITS)); 1407 } 1408 1409 // ------------------------------------------------------------------------------------------------ 1410 // Non-product code 1411 1412 #ifndef PRODUCT 1413 1414 void SafepointSynchronize::print_state() { 1415 if (_state == _not_synchronized) { 1416 tty->print_cr("not synchronized"); 1417 } else if (_state == _synchronizing || _state == _synchronized) { 1418 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" : 1419 "synchronized"); 1420 1421 for (JavaThread *cur = Threads::first(); cur; cur = cur->next()) { 1422 cur->safepoint_state()->print(); 1423 } 1424 } 1425 } 1426 1427 void SafepointSynchronize::safepoint_msg(const char* format, ...) { 1428 if (ShowSafepointMsgs) { 1429 va_list ap; 1430 va_start(ap, format); 1431 tty->vprint_cr(format, ap); 1432 va_end(ap); 1433 } 1434 } 1435 1436 #endif // !PRODUCT