1 /* 2 * Copyright (c) 1997, 2019, 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/classLoaderDataGraph.inline.hpp" 27 #include "classfile/dictionary.hpp" 28 #include "classfile/stringTable.hpp" 29 #include "classfile/symbolTable.hpp" 30 #include "classfile/systemDictionary.hpp" 31 #include "code/codeCache.hpp" 32 #include "code/icBuffer.hpp" 33 #include "code/nmethod.hpp" 34 #include "code/pcDesc.hpp" 35 #include "code/scopeDesc.hpp" 36 #include "gc/shared/collectedHeap.hpp" 37 #include "gc/shared/gcLocker.hpp" 38 #include "gc/shared/oopStorage.hpp" 39 #include "gc/shared/strongRootsScope.hpp" 40 #include "gc/shared/workgroup.hpp" 41 #include "interpreter/interpreter.hpp" 42 #include "jfr/jfrEvents.hpp" 43 #include "logging/log.hpp" 44 #include "logging/logStream.hpp" 45 #include "memory/resourceArea.hpp" 46 #include "memory/universe.hpp" 47 #include "oops/oop.inline.hpp" 48 #include "oops/symbol.hpp" 49 #include "runtime/atomic.hpp" 50 #include "runtime/compilationPolicy.hpp" 51 #include "runtime/deoptimization.hpp" 52 #include "runtime/frame.inline.hpp" 53 #include "runtime/handles.inline.hpp" 54 #include "runtime/interfaceSupport.inline.hpp" 55 #include "runtime/mutexLocker.hpp" 56 #include "runtime/orderAccess.hpp" 57 #include "runtime/osThread.hpp" 58 #include "runtime/safepoint.hpp" 59 #include "runtime/safepointMechanism.inline.hpp" 60 #include "runtime/signature.hpp" 61 #include "runtime/stubCodeGenerator.hpp" 62 #include "runtime/stubRoutines.hpp" 63 #include "runtime/sweeper.hpp" 64 #include "runtime/synchronizer.hpp" 65 #include "runtime/thread.inline.hpp" 66 #include "runtime/threadSMR.hpp" 67 #include "runtime/timerTrace.hpp" 68 #include "services/runtimeService.hpp" 69 #include "utilities/events.hpp" 70 #include "utilities/macros.hpp" 71 72 static void post_safepoint_begin_event(EventSafepointBegin& event, 73 uint64_t safepoint_id, 74 int thread_count, 75 int critical_thread_count) { 76 if (event.should_commit()) { 77 event.set_safepointId(safepoint_id); 78 event.set_totalThreadCount(thread_count); 79 event.set_jniCriticalThreadCount(critical_thread_count); 80 event.commit(); 81 } 82 } 83 84 static void post_safepoint_cleanup_event(EventSafepointCleanup& event, uint64_t safepoint_id) { 85 if (event.should_commit()) { 86 event.set_safepointId(safepoint_id); 87 event.commit(); 88 } 89 } 90 91 static void post_safepoint_synchronize_event(EventSafepointStateSynchronization& event, 92 uint64_t safepoint_id, 93 int initial_number_of_threads, 94 int threads_waiting_to_block, 95 uint64_t iterations) { 96 if (event.should_commit()) { 97 event.set_safepointId(safepoint_id); 98 event.set_initialThreadCount(initial_number_of_threads); 99 event.set_runningThreadCount(threads_waiting_to_block); 100 event.set_iterations(iterations); 101 event.commit(); 102 } 103 } 104 105 static void post_safepoint_cleanup_task_event(EventSafepointCleanupTask& event, 106 uint64_t safepoint_id, 107 const char* name) { 108 if (event.should_commit()) { 109 event.set_safepointId(safepoint_id); 110 event.set_name(name); 111 event.commit(); 112 } 113 } 114 115 static void post_safepoint_end_event(EventSafepointEnd& event, uint64_t safepoint_id) { 116 if (event.should_commit()) { 117 event.set_safepointId(safepoint_id); 118 event.commit(); 119 } 120 } 121 122 // SafepointCheck 123 SafepointStateTracker::SafepointStateTracker(uint64_t safepoint_id, bool at_safepoint) 124 : _safepoint_id(safepoint_id), _at_safepoint(at_safepoint) {} 125 126 bool SafepointStateTracker::safepoint_state_changed() { 127 return _safepoint_id != SafepointSynchronize::safepoint_id() || 128 _at_safepoint != SafepointSynchronize::is_at_safepoint(); 129 } 130 131 // -------------------------------------------------------------------------------------------------- 132 // Implementation of Safepoint begin/end 133 134 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized; 135 int SafepointSynchronize::_waiting_to_block = 0; 136 volatile uint64_t SafepointSynchronize::_safepoint_counter = 0; 137 uint64_t SafepointSynchronize::_safepoint_id = 0; 138 const uint64_t SafepointSynchronize::InactiveSafepointCounter = 0; 139 int SafepointSynchronize::_current_jni_active_count = 0; 140 141 WaitBarrier* SafepointSynchronize::_wait_barrier; 142 143 static volatile bool PageArmed = false; // safepoint polling page is RO|RW vs PROT_NONE 144 static bool timeout_error_printed = false; 145 146 // Statistic related 147 static jlong _safepoint_begin_time = 0; 148 static volatile int _nof_threads_hit_polling_page = 0; 149 150 void SafepointSynchronize::init(Thread* vmthread) { 151 // WaitBarrier should never be destroyed since we will have 152 // threads waiting on it while exiting. 153 _wait_barrier = new WaitBarrier(vmthread); 154 SafepointTracing::init(); 155 } 156 157 void SafepointSynchronize::increment_jni_active_count() { 158 assert(Thread::current()->is_VM_thread(), "Only VM thread may increment"); 159 ++_current_jni_active_count; 160 } 161 162 void SafepointSynchronize::decrement_waiting_to_block() { 163 assert(_waiting_to_block > 0, "sanity check"); 164 assert(Thread::current()->is_VM_thread(), "Only VM thread may decrement"); 165 --_waiting_to_block; 166 } 167 168 bool SafepointSynchronize::thread_not_running(ThreadSafepointState *cur_state) { 169 if (!cur_state->is_running()) { 170 return true; 171 } 172 cur_state->examine_state_of_thread(SafepointSynchronize::safepoint_counter()); 173 if (!cur_state->is_running()) { 174 return true; 175 } 176 LogTarget(Trace, safepoint) lt; 177 if (lt.is_enabled()) { 178 ResourceMark rm; 179 LogStream ls(lt); 180 cur_state->print_on(&ls); 181 } 182 return false; 183 } 184 185 #ifdef ASSERT 186 static void assert_list_is_valid(const ThreadSafepointState* tss_head, int still_running) { 187 int a = 0; 188 const ThreadSafepointState *tmp_tss = tss_head; 189 while (tmp_tss != NULL) { 190 ++a; 191 assert(tmp_tss->is_running(), "Illegal initial state"); 192 tmp_tss = tmp_tss->get_next(); 193 } 194 assert(a == still_running, "Must be the same"); 195 } 196 #endif // ASSERT 197 198 static void back_off(int64_t start_time) { 199 // We start with fine-grained nanosleeping until a millisecond has 200 // passed, at which point we resort to plain naked_short_sleep. 201 if (os::javaTimeNanos() - start_time < NANOSECS_PER_MILLISEC) { 202 os::naked_short_nanosleep(10 * (NANOUNITS / MICROUNITS)); 203 } else { 204 os::naked_short_sleep(1); 205 } 206 } 207 208 int SafepointSynchronize::synchronize_threads(jlong safepoint_limit_time, int nof_threads, int* initial_running) 209 { 210 JavaThreadIteratorWithHandle jtiwh; 211 212 #ifdef ASSERT 213 for (; JavaThread *cur = jtiwh.next(); ) { 214 assert(cur->safepoint_state()->is_running(), "Illegal initial state"); 215 } 216 jtiwh.rewind(); 217 #endif // ASSERT 218 219 // Iterate through all threads until it has been determined how to stop them all at a safepoint. 220 int still_running = nof_threads; 221 ThreadSafepointState *tss_head = NULL; 222 ThreadSafepointState **p_prev = &tss_head; 223 for (; JavaThread *cur = jtiwh.next(); ) { 224 ThreadSafepointState *cur_tss = cur->safepoint_state(); 225 assert(cur_tss->get_next() == NULL, "Must be NULL"); 226 if (thread_not_running(cur_tss)) { 227 --still_running; 228 } else { 229 *p_prev = cur_tss; 230 p_prev = cur_tss->next_ptr(); 231 } 232 } 233 *p_prev = NULL; 234 235 DEBUG_ONLY(assert_list_is_valid(tss_head, still_running);) 236 237 *initial_running = still_running; 238 239 // If there is no thread still running, we are already done. 240 if (still_running <= 0) { 241 assert(tss_head == NULL, "Must be empty"); 242 return 1; 243 } 244 245 int iterations = 1; // The first iteration is above. 246 int64_t start_time = os::javaTimeNanos(); 247 248 do { 249 // Check if this has taken too long: 250 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) { 251 print_safepoint_timeout(); 252 } 253 if (int(iterations) == -1) { // overflow - something is wrong. 254 // We can only overflow here when we are using global 255 // polling pages. We keep this guarantee in its original 256 // form so that searches of the bug database for this 257 // failure mode find the right bugs. 258 guarantee (!PageArmed, "invariant"); 259 } 260 261 p_prev = &tss_head; 262 ThreadSafepointState *cur_tss = tss_head; 263 while (cur_tss != NULL) { 264 assert(cur_tss->is_running(), "Illegal initial state"); 265 if (thread_not_running(cur_tss)) { 266 --still_running; 267 *p_prev = NULL; 268 ThreadSafepointState *tmp = cur_tss; 269 cur_tss = cur_tss->get_next(); 270 tmp->set_next(NULL); 271 } else { 272 *p_prev = cur_tss; 273 p_prev = cur_tss->next_ptr(); 274 cur_tss = cur_tss->get_next(); 275 } 276 } 277 278 DEBUG_ONLY(assert_list_is_valid(tss_head, still_running);) 279 280 if (still_running > 0) { 281 back_off(start_time); 282 } 283 284 iterations++; 285 } while (still_running > 0); 286 287 assert(tss_head == NULL, "Must be empty"); 288 289 return iterations; 290 } 291 292 void SafepointSynchronize::arm_safepoint() { 293 // Begin the process of bringing the system to a safepoint. 294 // Java threads can be in several different states and are 295 // stopped by different mechanisms: 296 // 297 // 1. Running interpreted 298 // When executing branching/returning byte codes interpreter 299 // checks if the poll is armed, if so blocks in SS::block(). 300 // When using global polling the interpreter dispatch table 301 // is changed to force it to check for a safepoint condition 302 // between bytecodes. 303 // 2. Running in native code 304 // When returning from the native code, a Java thread must check 305 // the safepoint _state to see if we must block. If the 306 // VM thread sees a Java thread in native, it does 307 // not wait for this thread to block. The order of the memory 308 // writes and reads of both the safepoint state and the Java 309 // threads state is critical. In order to guarantee that the 310 // memory writes are serialized with respect to each other, 311 // the VM thread issues a memory barrier instruction. 312 // 3. Running compiled Code 313 // Compiled code reads the local polling page that 314 // is set to fault if we are trying to get to a safepoint. 315 // 4. Blocked 316 // A thread which is blocked will not be allowed to return from the 317 // block condition until the safepoint operation is complete. 318 // 5. In VM or Transitioning between states 319 // If a Java thread is currently running in the VM or transitioning 320 // between states, the safepointing code will poll the thread state 321 // until the thread blocks itself when it attempts transitions to a 322 // new state or locking a safepoint checked monitor. 323 324 // We must never miss a thread with correct safepoint id, so we must make sure we arm 325 // the wait barrier for the next safepoint id/counter. 326 // Arming must be done after resetting _current_jni_active_count, _waiting_to_block. 327 _wait_barrier->arm(static_cast<int>(_safepoint_counter + 1)); 328 329 assert((_safepoint_counter & 0x1) == 0, "must be even"); 330 // The store to _safepoint_counter must happen after any stores in arming. 331 OrderAccess::release_store(&_safepoint_counter, _safepoint_counter + 1); 332 333 // We are synchronizing 334 OrderAccess::storestore(); // Ordered with _safepoint_counter 335 _state = _synchronizing; 336 337 if (SafepointMechanism::uses_thread_local_poll()) { 338 // Arming the per thread poll while having _state != _not_synchronized means safepointing 339 log_trace(safepoint)("Setting thread local yield flag for threads"); 340 OrderAccess::storestore(); // storestore, global state -> local state 341 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur = jtiwh.next(); ) { 342 // Make sure the threads start polling, it is time to yield. 343 SafepointMechanism::arm_local_poll(cur); 344 } 345 } 346 OrderAccess::fence(); // storestore|storeload, global state -> local state 347 348 if (SafepointMechanism::uses_global_page_poll()) { 349 // Make interpreter safepoint aware 350 Interpreter::notice_safepoints(); 351 352 // Make polling safepoint aware 353 guarantee (!PageArmed, "invariant") ; 354 PageArmed = true; 355 os::make_polling_page_unreadable(); 356 } 357 } 358 359 // Roll all threads forward to a safepoint and suspend them all 360 void SafepointSynchronize::begin() { 361 assert(Thread::current()->is_VM_thread(), "Only VM thread may execute a safepoint"); 362 363 EventSafepointBegin begin_event; 364 SafepointTracing::begin(VMThread::vm_op_type()); 365 366 Universe::heap()->safepoint_synchronize_begin(); 367 368 // By getting the Threads_lock, we assure that no threads are about to start or 369 // exit. It is released again in SafepointSynchronize::end(). 370 Threads_lock->lock(); 371 372 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state"); 373 374 int nof_threads = Threads::number_of_threads(); 375 376 _nof_threads_hit_polling_page = 0; 377 378 log_debug(safepoint)("Safepoint synchronization initiated using %s wait barrier. (%d threads)", _wait_barrier->description(), nof_threads); 379 380 // Reset the count of active JNI critical threads 381 _current_jni_active_count = 0; 382 383 // Set number of threads to wait for 384 _waiting_to_block = nof_threads; 385 386 jlong safepoint_limit_time = 0; 387 if (SafepointTimeout) { 388 // Set the limit time, so that it can be compared to see if this has taken 389 // too long to complete. 390 safepoint_limit_time = SafepointTracing::start_of_safepoint() + (jlong)SafepointTimeoutDelay * (NANOUNITS / MILLIUNITS); 391 timeout_error_printed = false; 392 } 393 394 EventSafepointStateSynchronization sync_event; 395 int initial_running = 0; 396 397 // Arms the safepoint, _current_jni_active_count and _waiting_to_block must be set before. 398 arm_safepoint(); 399 400 // Will spin until all threads are safe. 401 int iterations = synchronize_threads(safepoint_limit_time, nof_threads, &initial_running); 402 assert(_waiting_to_block == 0, "No thread should be running"); 403 404 #ifndef PRODUCT 405 if (safepoint_limit_time != 0) { 406 jlong current_time = os::javaTimeNanos(); 407 if (safepoint_limit_time < current_time) { 408 log_warning(safepoint)("# SafepointSynchronize: Finished after " 409 INT64_FORMAT_W(6) " ms", 410 (int64_t)(current_time - SafepointTracing::start_of_safepoint()) / (NANOUNITS / MILLIUNITS)); 411 } 412 } 413 #endif 414 415 assert(Threads_lock->owned_by_self(), "must hold Threads_lock"); 416 417 // Record state 418 _state = _synchronized; 419 420 OrderAccess::fence(); 421 422 // Set the new id 423 ++_safepoint_id; 424 425 #ifdef ASSERT 426 // Make sure all the threads were visited. 427 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur = jtiwh.next(); ) { 428 assert(cur->was_visited_for_critical_count(_safepoint_counter), "missed a thread"); 429 } 430 #endif // ASSERT 431 432 // Update the count of active JNI critical regions 433 GCLocker::set_jni_lock_count(_current_jni_active_count); 434 435 post_safepoint_synchronize_event(sync_event, 436 _safepoint_id, 437 initial_running, 438 _waiting_to_block, iterations); 439 440 SafepointTracing::synchronized(nof_threads, initial_running, _nof_threads_hit_polling_page); 441 442 // We do the safepoint cleanup first since a GC related safepoint 443 // needs cleanup to be completed before running the GC op. 444 EventSafepointCleanup cleanup_event; 445 do_cleanup_tasks(); 446 post_safepoint_cleanup_event(cleanup_event, _safepoint_id); 447 448 post_safepoint_begin_event(begin_event, _safepoint_id, nof_threads, _current_jni_active_count); 449 SafepointTracing::cleanup(); 450 } 451 452 void SafepointSynchronize::disarm_safepoint() { 453 uint64_t active_safepoint_counter = _safepoint_counter; 454 { 455 JavaThreadIteratorWithHandle jtiwh; 456 #ifdef ASSERT 457 // A pending_exception cannot be installed during a safepoint. The threads 458 // may install an async exception after they come back from a safepoint into 459 // pending_exception after they unblock. But that should happen later. 460 for (; JavaThread *cur = jtiwh.next(); ) { 461 assert (!(cur->has_pending_exception() && 462 cur->safepoint_state()->is_at_poll_safepoint()), 463 "safepoint installed a pending exception"); 464 } 465 #endif // ASSERT 466 467 if (SafepointMechanism::uses_global_page_poll()) { 468 guarantee (PageArmed, "invariant"); 469 // Make polling safepoint aware 470 os::make_polling_page_readable(); 471 PageArmed = false; 472 // Remove safepoint check from interpreter 473 Interpreter::ignore_safepoints(); 474 } 475 476 OrderAccess::fence(); // keep read and write of _state from floating up 477 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization"); 478 479 // Change state first to _not_synchronized. 480 // No threads should see _synchronized when running. 481 _state = _not_synchronized; 482 483 // Set the next dormant (even) safepoint id. 484 assert((_safepoint_counter & 0x1) == 1, "must be odd"); 485 OrderAccess::release_store(&_safepoint_counter, _safepoint_counter + 1); 486 487 OrderAccess::fence(); // Keep the local state from floating up. 488 489 jtiwh.rewind(); 490 for (; JavaThread *current = jtiwh.next(); ) { 491 // Clear the visited flag to ensure that the critical counts are collected properly. 492 DEBUG_ONLY(current->reset_visited_for_critical_count(active_safepoint_counter);) 493 ThreadSafepointState* cur_state = current->safepoint_state(); 494 assert(!cur_state->is_running(), "Thread not suspended at safepoint"); 495 cur_state->restart(); // TSS _running 496 assert(cur_state->is_running(), "safepoint state has not been reset"); 497 498 SafepointMechanism::disarm_if_needed(current, false /* NO release */); 499 } 500 } // ~JavaThreadIteratorWithHandle 501 502 // Release threads lock, so threads can be created/destroyed again. 503 Threads_lock->unlock(); 504 505 // Wake threads after local state is correctly set. 506 _wait_barrier->disarm(); 507 } 508 509 // Wake up all threads, so they are ready to resume execution after the safepoint 510 // operation has been carried out 511 void SafepointSynchronize::end() { 512 assert(Threads_lock->owned_by_self(), "must hold Threads_lock"); 513 EventSafepointEnd event; 514 assert(Thread::current()->is_VM_thread(), "Only VM thread can execute a safepoint"); 515 516 disarm_safepoint(); 517 518 Universe::heap()->safepoint_synchronize_end(); 519 520 SafepointTracing::end(); 521 522 post_safepoint_end_event(event, safepoint_id()); 523 } 524 525 bool SafepointSynchronize::is_cleanup_needed() { 526 // Need a safepoint if there are many monitors to deflate. 527 if (ObjectSynchronizer::is_cleanup_needed()) return true; 528 // Need a safepoint if some inline cache buffers is non-empty 529 if (!InlineCacheBuffer::is_empty()) return true; 530 if (StringTable::needs_rehashing()) return true; 531 if (SymbolTable::needs_rehashing()) return true; 532 return false; 533 } 534 535 class ParallelSPCleanupThreadClosure : public ThreadClosure { 536 private: 537 CodeBlobClosure* _nmethod_cl; 538 DeflateMonitorCounters* _counters; 539 540 public: 541 ParallelSPCleanupThreadClosure(DeflateMonitorCounters* counters) : 542 _nmethod_cl(UseCodeAging ? NMethodSweeper::prepare_reset_hotness_counters() : NULL), 543 _counters(counters) {} 544 545 void do_thread(Thread* thread) { 546 ObjectSynchronizer::deflate_thread_local_monitors(thread, _counters); 547 if (_nmethod_cl != NULL && thread->is_Java_thread() && 548 ! thread->is_Code_cache_sweeper_thread()) { 549 JavaThread* jt = (JavaThread*) thread; 550 jt->nmethods_do(_nmethod_cl); 551 } 552 } 553 }; 554 555 class ParallelSPCleanupTask : public AbstractGangTask { 556 private: 557 SubTasksDone _subtasks; 558 ParallelSPCleanupThreadClosure _cleanup_threads_cl; 559 uint _num_workers; 560 DeflateMonitorCounters* _counters; 561 public: 562 ParallelSPCleanupTask(uint num_workers, DeflateMonitorCounters* counters) : 563 AbstractGangTask("Parallel Safepoint Cleanup"), 564 _subtasks(SubTasksDone(SafepointSynchronize::SAFEPOINT_CLEANUP_NUM_TASKS)), 565 _cleanup_threads_cl(ParallelSPCleanupThreadClosure(counters)), 566 _num_workers(num_workers), 567 _counters(counters) {} 568 569 void work(uint worker_id) { 570 uint64_t safepoint_id = SafepointSynchronize::safepoint_id(); 571 // All threads deflate monitors and mark nmethods (if necessary). 572 Threads::possibly_parallel_threads_do(true, &_cleanup_threads_cl); 573 574 if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_DEFLATE_MONITORS)) { 575 const char* name = "deflating global idle monitors"; 576 EventSafepointCleanupTask event; 577 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup)); 578 ObjectSynchronizer::deflate_idle_monitors(_counters); 579 580 post_safepoint_cleanup_task_event(event, safepoint_id, name); 581 } 582 583 if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_UPDATE_INLINE_CACHES)) { 584 const char* name = "updating inline caches"; 585 EventSafepointCleanupTask event; 586 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup)); 587 InlineCacheBuffer::update_inline_caches(); 588 589 post_safepoint_cleanup_task_event(event, safepoint_id, name); 590 } 591 592 if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_COMPILATION_POLICY)) { 593 const char* name = "compilation policy safepoint handler"; 594 EventSafepointCleanupTask event; 595 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup)); 596 CompilationPolicy::policy()->do_safepoint_work(); 597 598 post_safepoint_cleanup_task_event(event, safepoint_id, name); 599 } 600 601 if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_SYMBOL_TABLE_REHASH)) { 602 if (SymbolTable::needs_rehashing()) { 603 const char* name = "rehashing symbol table"; 604 EventSafepointCleanupTask event; 605 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup)); 606 SymbolTable::rehash_table(); 607 608 post_safepoint_cleanup_task_event(event, safepoint_id, name); 609 } 610 } 611 612 if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_STRING_TABLE_REHASH)) { 613 if (StringTable::needs_rehashing()) { 614 const char* name = "rehashing string table"; 615 EventSafepointCleanupTask event; 616 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup)); 617 StringTable::rehash_table(); 618 619 post_safepoint_cleanup_task_event(event, safepoint_id, name); 620 } 621 } 622 623 if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_CLD_PURGE)) { 624 if (ClassLoaderDataGraph::should_purge_and_reset()) { 625 // CMS delays purging the CLDG until the beginning of the next safepoint and to 626 // make sure concurrent sweep is done 627 const char* name = "purging class loader data graph"; 628 EventSafepointCleanupTask event; 629 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup)); 630 ClassLoaderDataGraph::purge(); 631 632 post_safepoint_cleanup_task_event(event, safepoint_id, name); 633 } 634 } 635 636 if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_SYSTEM_DICTIONARY_RESIZE)) { 637 if (Dictionary::does_any_dictionary_needs_resizing()) { 638 const char* name = "resizing system dictionaries"; 639 EventSafepointCleanupTask event; 640 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup)); 641 ClassLoaderDataGraph::resize_dictionaries(); 642 643 post_safepoint_cleanup_task_event(event, safepoint_id, name); 644 } 645 } 646 647 if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_REQUEST_OOPSTORAGE_CLEANUP)) { 648 // Don't bother reporting event or time for this very short operation. 649 // To have any utility we'd also want to report whether needed. 650 OopStorage::trigger_cleanup_if_needed(); 651 } 652 653 _subtasks.all_tasks_completed(_num_workers); 654 } 655 }; 656 657 // Various cleaning tasks that should be done periodically at safepoints. 658 void SafepointSynchronize::do_cleanup_tasks() { 659 660 TraceTime timer("safepoint cleanup tasks", TRACETIME_LOG(Info, safepoint, cleanup)); 661 662 // Prepare for monitor deflation. 663 DeflateMonitorCounters deflate_counters; 664 ObjectSynchronizer::prepare_deflate_idle_monitors(&deflate_counters); 665 666 CollectedHeap* heap = Universe::heap(); 667 assert(heap != NULL, "heap not initialized yet?"); 668 WorkGang* cleanup_workers = heap->get_safepoint_workers(); 669 if (cleanup_workers != NULL) { 670 // Parallel cleanup using GC provided thread pool. 671 uint num_cleanup_workers = cleanup_workers->active_workers(); 672 ParallelSPCleanupTask cleanup(num_cleanup_workers, &deflate_counters); 673 StrongRootsScope srs(num_cleanup_workers); 674 cleanup_workers->run_task(&cleanup); 675 } else { 676 // Serial cleanup using VMThread. 677 ParallelSPCleanupTask cleanup(1, &deflate_counters); 678 StrongRootsScope srs(1); 679 cleanup.work(0); 680 } 681 682 // Needs to be done single threaded by the VMThread. This walks 683 // the thread stacks looking for references to metadata before 684 // deciding to remove it from the metaspaces. 685 if (ClassLoaderDataGraph::should_clean_metaspaces_and_reset()) { 686 const char* name = "cleanup live ClassLoaderData metaspaces"; 687 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup)); 688 ClassLoaderDataGraph::walk_metadata_and_clean_metaspaces(); 689 } 690 691 // Finish monitor deflation. 692 ObjectSynchronizer::finish_deflate_idle_monitors(&deflate_counters); 693 694 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 695 } 696 697 // Methods for determining if a JavaThread is safepoint safe. 698 699 // False means unsafe with undetermined state. 700 // True means a determined state, but it may be an unsafe state. 701 // If called from a non-safepoint context safepoint_count MUST be InactiveSafepointCounter. 702 bool SafepointSynchronize::try_stable_load_state(JavaThreadState *state, JavaThread *thread, uint64_t safepoint_count) { 703 assert((safepoint_count != InactiveSafepointCounter && 704 Thread::current() == (Thread*)VMThread::vm_thread() && 705 SafepointSynchronize::_state != _not_synchronized) 706 || safepoint_count == InactiveSafepointCounter, "Invalid check"); 707 708 // To handle the thread_blocked state on the backedge of the WaitBarrier from 709 // previous safepoint and reading the reset value (0/InactiveSafepointCounter) we 710 // re-read state after we read thread safepoint id. The JavaThread changes its 711 // thread state from thread_blocked before resetting safepoint id to 0. 712 // This guarantees the second read will be from an updated thread state. It can 713 // either be different state making this an unsafe state or it can see blocked 714 // again. When we see blocked twice with a 0 safepoint id, either: 715 // - It is normally blocked, e.g. on Mutex, TBIVM. 716 // - It was in SS:block(), looped around to SS:block() and is blocked on the WaitBarrier. 717 // - It was in SS:block() but now on a Mutex. 718 // All of these cases are safe. 719 720 *state = thread->thread_state(); 721 OrderAccess::loadload(); 722 uint64_t sid = thread->safepoint_state()->get_safepoint_id(); // Load acquire 723 if (sid != InactiveSafepointCounter && sid != safepoint_count) { 724 // In an old safepoint, state not relevant. 725 return false; 726 } 727 return *state == thread->thread_state(); 728 } 729 730 static bool safepoint_safe_with(JavaThread *thread, JavaThreadState state) { 731 switch(state) { 732 case _thread_in_native: 733 // native threads are safe if they have no java stack or have walkable stack 734 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable(); 735 736 case _thread_blocked: 737 // On wait_barrier or blocked. 738 // Blocked threads should already have walkable stack. 739 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable"); 740 return true; 741 742 default: 743 return false; 744 } 745 } 746 747 bool SafepointSynchronize::handshake_safe(JavaThread *thread) { 748 // This function must be called with the Threads_lock held so an externally 749 // suspended thread cannot be resumed thus it is safe. 750 assert(Threads_lock->owned_by_self() && Thread::current()->is_VM_thread(), 751 "Must hold Threads_lock and be VMThread"); 752 if (thread->is_ext_suspended() || thread->is_terminated()) { 753 return true; 754 } 755 JavaThreadState stable_state; 756 if (try_stable_load_state(&stable_state, thread, InactiveSafepointCounter)) { 757 return safepoint_safe_with(thread, stable_state); 758 } 759 return false; 760 } 761 762 // See if the thread is running inside a lazy critical native and 763 // update the thread critical count if so. Also set a suspend flag to 764 // cause the native wrapper to return into the JVM to do the unlock 765 // once the native finishes. 766 static void check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) { 767 if (state == _thread_in_native && 768 thread->has_last_Java_frame() && 769 thread->frame_anchor()->walkable()) { 770 // This thread might be in a critical native nmethod so look at 771 // the top of the stack and increment the critical count if it 772 // is. 773 frame wrapper_frame = thread->last_frame(); 774 CodeBlob* stub_cb = wrapper_frame.cb(); 775 if (stub_cb != NULL && 776 stub_cb->is_nmethod() && 777 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) { 778 // A thread could potentially be in a critical native across 779 // more than one safepoint, so only update the critical state on 780 // the first one. When it returns it will perform the unlock. 781 if (!thread->do_critical_native_unlock()) { 782 #ifdef ASSERT 783 if (!thread->in_critical()) { 784 GCLocker::increment_debug_jni_lock_count(); 785 } 786 #endif 787 thread->enter_critical(); 788 // Make sure the native wrapper calls back on return to 789 // perform the needed critical unlock. 790 thread->set_critical_native_unlock(); 791 } 792 } 793 } 794 } 795 796 // ------------------------------------------------------------------------------------------------------- 797 // Implementation of Safepoint blocking point 798 799 void SafepointSynchronize::block(JavaThread *thread) { 800 assert(thread != NULL, "thread must be set"); 801 assert(thread->is_Java_thread(), "not a Java thread"); 802 803 // Threads shouldn't block if they are in the middle of printing, but... 804 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id()); 805 806 // Only bail from the block() call if the thread is gone from the 807 // thread list; starting to exit should still block. 808 if (thread->is_terminated()) { 809 // block current thread if we come here from native code when VM is gone 810 thread->block_if_vm_exited(); 811 812 // otherwise do nothing 813 return; 814 } 815 816 JavaThreadState state = thread->thread_state(); 817 thread->frame_anchor()->make_walkable(thread); 818 819 uint64_t safepoint_id = SafepointSynchronize::safepoint_counter(); 820 // Check that we have a valid thread_state at this point 821 switch(state) { 822 case _thread_in_vm_trans: 823 case _thread_in_Java: // From compiled code 824 case _thread_in_native_trans: 825 case _thread_blocked_trans: 826 case _thread_new_trans: 827 828 // We have no idea where the VMThread is, it might even be at next safepoint. 829 // So we can miss this poll, but stop at next. 830 831 // Load dependent store, it must not pass loading of safepoint_id. 832 thread->safepoint_state()->set_safepoint_id(safepoint_id); // Release store 833 834 // This part we can skip if we notice we miss or are in a future safepoint. 835 OrderAccess::storestore(); 836 // Load in wait barrier should not float up 837 thread->set_thread_state_fence(_thread_blocked); 838 839 _wait_barrier->wait(static_cast<int>(safepoint_id)); 840 assert(_state != _synchronized, "Can't be"); 841 842 // If barrier is disarmed stop store from floating above loads in barrier. 843 OrderAccess::loadstore(); 844 thread->set_thread_state(state); 845 846 // Then we reset the safepoint id to inactive. 847 thread->safepoint_state()->reset_safepoint_id(); // Release store 848 849 OrderAccess::fence(); 850 851 break; 852 853 default: 854 fatal("Illegal threadstate encountered: %d", state); 855 } 856 guarantee(thread->safepoint_state()->get_safepoint_id() == InactiveSafepointCounter, 857 "The safepoint id should be set only in block path"); 858 859 // Check for pending. async. exceptions or suspends - except if the 860 // thread was blocked inside the VM. has_special_runtime_exit_condition() 861 // is called last since it grabs a lock and we only want to do that when 862 // we must. 863 // 864 // Note: we never deliver an async exception at a polling point as the 865 // compiler may not have an exception handler for it. The polling 866 // code will notice the async and deoptimize and the exception will 867 // be delivered. (Polling at a return point is ok though). Sure is 868 // a lot of bother for a deprecated feature... 869 // 870 // We don't deliver an async exception if the thread state is 871 // _thread_in_native_trans so JNI functions won't be called with 872 // a surprising pending exception. If the thread state is going back to java, 873 // async exception is checked in check_special_condition_for_native_trans(). 874 875 if (state != _thread_blocked_trans && 876 state != _thread_in_vm_trans && 877 thread->has_special_runtime_exit_condition()) { 878 thread->handle_special_runtime_exit_condition( 879 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans)); 880 } 881 882 // cross_modify_fence is done by SafepointMechanism::block_if_requested_slow 883 // which is the only caller here. 884 } 885 886 // ------------------------------------------------------------------------------------------------------ 887 // Exception handlers 888 889 890 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) { 891 assert(thread->is_Java_thread(), "polling reference encountered by VM thread"); 892 assert(thread->thread_state() == _thread_in_Java, "should come from Java code"); 893 if (!ThreadLocalHandshakes) { 894 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization"); 895 } 896 897 if (log_is_enabled(Info, safepoint, stats)) { 898 Atomic::inc(&_nof_threads_hit_polling_page); 899 } 900 901 ThreadSafepointState* state = thread->safepoint_state(); 902 903 state->handle_polling_page_exception(); 904 } 905 906 907 void SafepointSynchronize::print_safepoint_timeout() { 908 if (!timeout_error_printed) { 909 timeout_error_printed = true; 910 // Print out the thread info which didn't reach the safepoint for debugging 911 // purposes (useful when there are lots of threads in the debugger). 912 LogTarget(Warning, safepoint) lt; 913 if (lt.is_enabled()) { 914 ResourceMark rm; 915 LogStream ls(lt); 916 917 ls.cr(); 918 ls.print_cr("# SafepointSynchronize::begin: Timeout detected:"); 919 ls.print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint."); 920 ls.print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:"); 921 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur_thread = jtiwh.next(); ) { 922 if (cur_thread->safepoint_state()->is_running()) { 923 ls.print("# "); 924 cur_thread->print_on(&ls); 925 ls.cr(); 926 } 927 } 928 ls.print_cr("# SafepointSynchronize::begin: (End of list)"); 929 } 930 } 931 932 // To debug the long safepoint, specify both AbortVMOnSafepointTimeout & 933 // ShowMessageBoxOnError. 934 if (AbortVMOnSafepointTimeout) { 935 // Send the blocking thread a signal to terminate and write an error file. 936 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur_thread = jtiwh.next(); ) { 937 if (cur_thread->safepoint_state()->is_running()) { 938 if (!os::signal_thread(cur_thread, SIGILL, "blocking a safepoint")) { 939 break; // Could not send signal. Report fatal error. 940 } 941 // Give cur_thread a chance to report the error and terminate the VM. 942 os::naked_sleep(3000); 943 } 944 } 945 fatal("Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.", 946 SafepointTimeoutDelay, VMThread::vm_operation()->name()); 947 } 948 } 949 950 // ------------------------------------------------------------------------------------------------------- 951 // Implementation of ThreadSafepointState 952 953 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) 954 : _at_poll_safepoint(false), _thread(thread), _safepoint_safe(false), 955 _safepoint_id(SafepointSynchronize::InactiveSafepointCounter), _next(NULL) { 956 } 957 958 void ThreadSafepointState::create(JavaThread *thread) { 959 ThreadSafepointState *state = new ThreadSafepointState(thread); 960 thread->set_safepoint_state(state); 961 } 962 963 void ThreadSafepointState::destroy(JavaThread *thread) { 964 if (thread->safepoint_state()) { 965 delete(thread->safepoint_state()); 966 thread->set_safepoint_state(NULL); 967 } 968 } 969 970 uint64_t ThreadSafepointState::get_safepoint_id() const { 971 return OrderAccess::load_acquire(&_safepoint_id); 972 } 973 974 void ThreadSafepointState::reset_safepoint_id() { 975 OrderAccess::release_store(&_safepoint_id, SafepointSynchronize::InactiveSafepointCounter); 976 } 977 978 void ThreadSafepointState::set_safepoint_id(uint64_t safepoint_id) { 979 OrderAccess::release_store(&_safepoint_id, safepoint_id); 980 } 981 982 void ThreadSafepointState::examine_state_of_thread(uint64_t safepoint_count) { 983 assert(is_running(), "better be running or just have hit safepoint poll"); 984 985 JavaThreadState stable_state; 986 if (!SafepointSynchronize::try_stable_load_state(&stable_state, _thread, safepoint_count)) { 987 // We could not get stable state of the JavaThread. 988 // Consider it running and just return. 989 return; 990 } 991 992 // Check for a thread that is suspended. Note that thread resume tries 993 // to grab the Threads_lock which we own here, so a thread cannot be 994 // resumed during safepoint synchronization. 995 996 // We check to see if this thread is suspended without locking to 997 // avoid deadlocking with a third thread that is waiting for this 998 // thread to be suspended. The third thread can notice the safepoint 999 // that we're trying to start at the beginning of its SR_lock->wait() 1000 // call. If that happens, then the third thread will block on the 1001 // safepoint while still holding the underlying SR_lock. We won't be 1002 // able to get the SR_lock and we'll deadlock. 1003 // 1004 // We don't need to grab the SR_lock here for two reasons: 1005 // 1) The suspend flags are both volatile and are set with an 1006 // Atomic::cmpxchg() call so we should see the suspended 1007 // state right away. 1008 // 2) We're being called from the safepoint polling loop; if 1009 // we don't see the suspended state on this iteration, then 1010 // we'll come around again. 1011 // 1012 bool is_suspended = _thread->is_ext_suspended(); 1013 if (is_suspended) { 1014 account_safe_thread(); 1015 return; 1016 } 1017 1018 if (safepoint_safe_with(_thread, stable_state)) { 1019 check_for_lazy_critical_native(_thread, stable_state); 1020 account_safe_thread(); 1021 return; 1022 } 1023 1024 // All other thread states will continue to run until they 1025 // transition and self-block in state _blocked 1026 // Safepoint polling in compiled code causes the Java threads to do the same. 1027 // Note: new threads may require a malloc so they must be allowed to finish 1028 1029 assert(is_running(), "examine_state_of_thread on non-running thread"); 1030 return; 1031 } 1032 1033 void ThreadSafepointState::account_safe_thread() { 1034 SafepointSynchronize::decrement_waiting_to_block(); 1035 if (_thread->in_critical()) { 1036 // Notice that this thread is in a critical section 1037 SafepointSynchronize::increment_jni_active_count(); 1038 } 1039 DEBUG_ONLY(_thread->set_visited_for_critical_count(SafepointSynchronize::safepoint_counter());) 1040 assert(!_safepoint_safe, "Must be unsafe before safe"); 1041 _safepoint_safe = true; 1042 } 1043 1044 void ThreadSafepointState::restart() { 1045 assert(_safepoint_safe, "Must be safe before unsafe"); 1046 _safepoint_safe = false; 1047 } 1048 1049 void ThreadSafepointState::print_on(outputStream *st) const { 1050 const char *s = _safepoint_safe ? "_at_safepoint" : "_running"; 1051 1052 st->print_cr("Thread: " INTPTR_FORMAT 1053 " [0x%2x] State: %s _at_poll_safepoint %d", 1054 p2i(_thread), _thread->osthread()->thread_id(), s, _at_poll_safepoint); 1055 1056 _thread->print_thread_state_on(st); 1057 } 1058 1059 // --------------------------------------------------------------------------------------------------------------------- 1060 1061 // Block the thread at poll or poll return for safepoint/handshake. 1062 void ThreadSafepointState::handle_polling_page_exception() { 1063 1064 // If we're using a global poll, then the thread should not be 1065 // marked as safepoint safe yet. 1066 assert(!SafepointMechanism::uses_global_page_poll() || !_safepoint_safe, 1067 "polling page exception on thread safepoint safe"); 1068 1069 // Step 1: Find the nmethod from the return address 1070 address real_return_addr = thread()->saved_exception_pc(); 1071 1072 CodeBlob *cb = CodeCache::find_blob(real_return_addr); 1073 assert(cb != NULL && cb->is_compiled(), "return address should be in nmethod"); 1074 CompiledMethod* nm = (CompiledMethod*)cb; 1075 1076 // Find frame of caller 1077 frame stub_fr = thread()->last_frame(); 1078 CodeBlob* stub_cb = stub_fr.cb(); 1079 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub"); 1080 RegisterMap map(thread(), true); 1081 frame caller_fr = stub_fr.sender(&map); 1082 1083 // Should only be poll_return or poll 1084 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" ); 1085 1086 // This is a poll immediately before a return. The exception handling code 1087 // has already had the effect of causing the return to occur, so the execution 1088 // will continue immediately after the call. In addition, the oopmap at the 1089 // return point does not mark the return value as an oop (if it is), so 1090 // it needs a handle here to be updated. 1091 if( nm->is_at_poll_return(real_return_addr) ) { 1092 // See if return type is an oop. 1093 bool return_oop = nm->method()->is_returning_oop(); 1094 Handle return_value; 1095 if (return_oop) { 1096 // The oop result has been saved on the stack together with all 1097 // the other registers. In order to preserve it over GCs we need 1098 // to keep it in a handle. 1099 oop result = caller_fr.saved_oop_result(&map); 1100 assert(oopDesc::is_oop_or_null(result), "must be oop"); 1101 return_value = Handle(thread(), result); 1102 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer"); 1103 } 1104 1105 // Block the thread 1106 SafepointMechanism::block_if_requested(thread()); 1107 1108 // restore oop result, if any 1109 if (return_oop) { 1110 caller_fr.set_saved_oop_result(&map, return_value()); 1111 } 1112 } 1113 1114 // This is a safepoint poll. Verify the return address and block. 1115 else { 1116 set_at_poll_safepoint(true); 1117 1118 // verify the blob built the "return address" correctly 1119 assert(real_return_addr == caller_fr.pc(), "must match"); 1120 1121 // Block the thread 1122 SafepointMechanism::block_if_requested(thread()); 1123 set_at_poll_safepoint(false); 1124 1125 // If we have a pending async exception deoptimize the frame 1126 // as otherwise we may never deliver it. 1127 if (thread()->has_async_condition()) { 1128 ThreadInVMfromJavaNoAsyncException __tiv(thread()); 1129 Deoptimization::deoptimize_frame(thread(), caller_fr.id()); 1130 } 1131 1132 // If an exception has been installed we must check for a pending deoptimization 1133 // Deoptimize frame if exception has been thrown. 1134 1135 if (thread()->has_pending_exception() ) { 1136 RegisterMap map(thread(), true); 1137 frame caller_fr = stub_fr.sender(&map); 1138 if (caller_fr.is_deoptimized_frame()) { 1139 // The exception patch will destroy registers that are still 1140 // live and will be needed during deoptimization. Defer the 1141 // Async exception should have deferred the exception until the 1142 // next safepoint which will be detected when we get into 1143 // the interpreter so if we have an exception now things 1144 // are messed up. 1145 1146 fatal("Exception installed and deoptimization is pending"); 1147 } 1148 } 1149 } 1150 } 1151 1152 1153 // ------------------------------------------------------------------------------------------------------- 1154 // Implementation of SafepointTracing 1155 1156 jlong SafepointTracing::_last_safepoint_begin_time_ns = 0; 1157 jlong SafepointTracing::_last_safepoint_sync_time_ns = 0; 1158 jlong SafepointTracing::_last_safepoint_cleanup_time_ns = 0; 1159 jlong SafepointTracing::_last_safepoint_end_time_ns = 0; 1160 jlong SafepointTracing::_last_safepoint_end_time_epoch_ms = 0; 1161 jlong SafepointTracing::_last_app_time_ns = 0; 1162 int SafepointTracing::_nof_threads = 0; 1163 int SafepointTracing::_nof_running = 0; 1164 int SafepointTracing::_page_trap = 0; 1165 VM_Operation::VMOp_Type SafepointTracing::_current_type; 1166 jlong SafepointTracing::_max_sync_time = 0; 1167 jlong SafepointTracing::_max_vmop_time = 0; 1168 uint64_t SafepointTracing::_op_count[VM_Operation::VMOp_Terminating] = {0}; 1169 1170 void SafepointTracing::init() { 1171 // Application start 1172 _last_safepoint_end_time_ns = os::javaTimeNanos(); 1173 // amount of time since epoch 1174 _last_safepoint_end_time_epoch_ms = os::javaTimeMillis(); 1175 } 1176 1177 // Helper method to print the header. 1178 static void print_header(outputStream* st) { 1179 // The number of spaces is significant here, and should match the format 1180 // specifiers in print_statistics(). 1181 1182 st->print("VM Operation " 1183 "[ threads: total initial_running ]" 1184 "[ time: sync cleanup vmop total ]"); 1185 1186 st->print_cr(" page_trap_count"); 1187 } 1188 1189 // This prints a nice table. To get the statistics to not shift due to the logging uptime 1190 // decorator, use the option as: -Xlog:safepoint+stats:[outputfile]:none 1191 void SafepointTracing::statistics_log() { 1192 LogTarget(Info, safepoint, stats) lt; 1193 assert (lt.is_enabled(), "should only be called when printing statistics is enabled"); 1194 LogStream ls(lt); 1195 1196 static int _cur_stat_index = 0; 1197 1198 // Print header every 30 entries 1199 if ((_cur_stat_index % 30) == 0) { 1200 print_header(&ls); 1201 _cur_stat_index = 1; // wrap 1202 } else { 1203 _cur_stat_index++; 1204 } 1205 1206 ls.print("%-28s [ " 1207 INT32_FORMAT_W(8) " " INT32_FORMAT_W(8) " " 1208 "]", 1209 VM_Operation::name(_current_type), 1210 _nof_threads, 1211 _nof_running); 1212 ls.print("[ " 1213 INT64_FORMAT_W(10) " " INT64_FORMAT_W(10) " " 1214 INT64_FORMAT_W(10) " " INT64_FORMAT_W(10) " ]", 1215 (int64_t)(_last_safepoint_sync_time_ns - _last_safepoint_begin_time_ns), 1216 (int64_t)(_last_safepoint_cleanup_time_ns - _last_safepoint_sync_time_ns), 1217 (int64_t)(_last_safepoint_end_time_ns - _last_safepoint_cleanup_time_ns), 1218 (int64_t)(_last_safepoint_end_time_ns - _last_safepoint_begin_time_ns)); 1219 1220 ls.print_cr(INT32_FORMAT_W(16), _page_trap); 1221 } 1222 1223 // This method will be called when VM exits. This tries to summarize the sampling. 1224 // Current thread may already be deleted, so don't use ResourceMark. 1225 void SafepointTracing::statistics_exit_log() { 1226 if (!log_is_enabled(Info, safepoint, stats)) { 1227 return; 1228 } 1229 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) { 1230 if (_op_count[index] != 0) { 1231 log_info(safepoint, stats)("%-28s" UINT64_FORMAT_W(10), VM_Operation::name(index), 1232 _op_count[index]); 1233 } 1234 } 1235 1236 log_info(safepoint, stats)("VM operations coalesced during safepoint " INT64_FORMAT, 1237 VMThread::get_coalesced_count()); 1238 log_info(safepoint, stats)("Maximum sync time " INT64_FORMAT" ns", 1239 (int64_t)(_max_sync_time)); 1240 log_info(safepoint, stats)("Maximum vm operation time (except for Exit VM operation) " 1241 INT64_FORMAT " ns", 1242 (int64_t)(_max_vmop_time)); 1243 } 1244 1245 void SafepointTracing::begin(VM_Operation::VMOp_Type type) { 1246 _op_count[type]++; 1247 _current_type = type; 1248 1249 // update the time stamp to begin recording safepoint time 1250 _last_safepoint_begin_time_ns = os::javaTimeNanos(); 1251 _last_safepoint_sync_time_ns = 0; 1252 _last_safepoint_cleanup_time_ns = 0; 1253 1254 _last_app_time_ns = _last_safepoint_begin_time_ns - _last_safepoint_end_time_ns; 1255 _last_safepoint_end_time_ns = 0; 1256 1257 RuntimeService::record_safepoint_begin(_last_app_time_ns); 1258 } 1259 1260 void SafepointTracing::synchronized(int nof_threads, int nof_running, int traps) { 1261 _last_safepoint_sync_time_ns = os::javaTimeNanos(); 1262 _nof_threads = nof_threads; 1263 _nof_running = nof_running; 1264 _page_trap = traps; 1265 RuntimeService::record_safepoint_synchronized(_last_safepoint_sync_time_ns - _last_safepoint_begin_time_ns); 1266 } 1267 1268 void SafepointTracing::cleanup() { 1269 _last_safepoint_cleanup_time_ns = os::javaTimeNanos(); 1270 } 1271 1272 void SafepointTracing::end() { 1273 _last_safepoint_end_time_ns = os::javaTimeNanos(); 1274 // amount of time since epoch 1275 _last_safepoint_end_time_epoch_ms = os::javaTimeMillis(); 1276 1277 if (_max_sync_time < (_last_safepoint_sync_time_ns - _last_safepoint_begin_time_ns)) { 1278 _max_sync_time = _last_safepoint_sync_time_ns - _last_safepoint_begin_time_ns; 1279 } 1280 if (_max_vmop_time < (_last_safepoint_end_time_ns - _last_safepoint_sync_time_ns)) { 1281 _max_vmop_time = _last_safepoint_end_time_ns - _last_safepoint_sync_time_ns; 1282 } 1283 if (log_is_enabled(Info, safepoint, stats)) { 1284 statistics_log(); 1285 } 1286 1287 log_info(safepoint)( 1288 "Safepoint \"%s\", " 1289 "Time since last: " JLONG_FORMAT " ns, " 1290 "Reaching safepoint: " JLONG_FORMAT " ns, " 1291 "At safepoint: " JLONG_FORMAT " ns, " 1292 "Total: " JLONG_FORMAT " ns", 1293 VM_Operation::name(_current_type), 1294 _last_app_time_ns, 1295 _last_safepoint_cleanup_time_ns - _last_safepoint_begin_time_ns, 1296 _last_safepoint_end_time_ns - _last_safepoint_cleanup_time_ns, 1297 _last_safepoint_end_time_ns - _last_safepoint_begin_time_ns 1298 ); 1299 1300 RuntimeService::record_safepoint_end(_last_safepoint_end_time_ns - _last_safepoint_cleanup_time_ns); 1301 }