safepoint.cpp revision 9056:dc9930a04ab0
150472Speter/* 21664Sphk * Copyright (c) 1997, 2015, Oracle and/or its affiliates. All rights reserved. 369040Sben * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 469040Sben * 569040Sben * This code is free software; you can redistribute it and/or modify it 669040Sben * under the terms of the GNU General Public License version 2 only, as 73023Srgrimes * published by the Free Software Foundation. 83023Srgrimes * 93023Srgrimes * This code is distributed in the hope that it will be useful, but WITHOUT 101664Sphk * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 113023Srgrimes * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 123023Srgrimes * version 2 for more details (a copy is included in the LICENSE file that 131664Sphk * accompanied this code). 141664Sphk * 151664Sphk * You should have received a copy of the GNU General Public License version 1672679Skris * 2 along with this work; if not, write to the Free Software Foundation, 1772878Skris * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 1872878Skris * 1972878Skris * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 2072878Skris * or visit www.oracle.com if you need additional information or have any 2172878Skris * questions. 2272878Skris * 2372878Skris */ 2472878Skris 2572878Skris#include "precompiled.hpp" 2672878Skris#include "classfile/stringTable.hpp" 2772679Skris#include "classfile/systemDictionary.hpp" 2872878Skris#include "code/codeCache.hpp" 2972878Skris#include "code/icBuffer.hpp" 3072878Skris#include "code/nmethod.hpp" 3158648Skris#include "code/pcDesc.hpp" 3268917Sdougb#include "code/scopeDesc.hpp" 3358648Skris#include "gc/shared/collectedHeap.hpp" 3468917Sdougb#include "gc/shared/gcLocker.inline.hpp" 3558648Skris#include "interpreter/interpreter.hpp" 3658648Skris#include "memory/resourceArea.hpp" 3758648Skris#include "memory/universe.inline.hpp" 381664Sphk#include "oops/oop.inline.hpp" 3929281Sjkh#include "oops/symbol.hpp" 401664Sphk#include "runtime/atomic.inline.hpp" 4159006Sobrien#include "runtime/compilationPolicy.hpp" 4259006Sobrien#include "runtime/deoptimization.hpp" 4359006Sobrien#include "runtime/frame.inline.hpp" 4459006Sobrien#include "runtime/interfaceSupport.hpp" 451664Sphk#include "runtime/mutexLocker.hpp" 4659006Sobrien#include "runtime/orderAccess.inline.hpp" 4759006Sobrien#include "runtime/osThread.hpp" 4862136Sobrien#include "runtime/safepoint.hpp" 4962136Sobrien#include "runtime/signature.hpp" 5062136Sobrien#include "runtime/stubCodeGenerator.hpp" 5162136Sobrien#include "runtime/stubRoutines.hpp" 5262136Sobrien#include "runtime/sweeper.hpp" 5362136Sobrien#include "runtime/synchronizer.hpp" 5462136Sobrien#include "runtime/thread.inline.hpp" 5562136Sobrien#include "services/runtimeService.hpp" 5662136Sobrien#include "utilities/events.hpp" 5768917Sdougb#include "utilities/macros.hpp" 5868263Sobrien#if INCLUDE_ALL_GCS 5968263Sobrien#include "gc/cms/concurrentMarkSweepThread.hpp" 6068263Sobrien#include "gc/g1/suspendibleThreadSet.hpp" 6165380Sobrien#endif // INCLUDE_ALL_GCS 6265380Sobrien#ifdef COMPILER1 6365380Sobrien#include "c1/c1_globals.hpp" 6442325Sobrien#endif 6535222Sache 6635222SachePRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC 6765884Sache 6865957Sache// -------------------------------------------------------------------------------------------------- 6965884Sache// Implementation of Safepoint begin/end 7068559Sru 7164576SimpSafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized; 7234651Sjkhvolatile int SafepointSynchronize::_waiting_to_block = 0; 7350883Smarkmvolatile int SafepointSynchronize::_safepoint_counter = 0; 7450883Smarkmint SafepointSynchronize::_current_jni_active_count = 0; 7550883Smarkmlong SafepointSynchronize::_end_of_last_safepoint = 0; 7664803Sbrianstatic volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE 7764803Sbrianstatic volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only 7864803Sbrianstatic bool timeout_error_printed = false; 7968705Sgreen 8068705Sgreen// Roll all threads forward to a safepoint and suspend them all 8168705Sgreenvoid SafepointSynchronize::begin() { 8251299Speter 8357542Skris Thread* myThread = Thread::current(); 8459124Sasmodai assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint"); 8557542Skris 8661139Shoek if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) { 8758859Ssheldonh _safepoint_begin_time = os::javaTimeNanos(); 8859884Schuckr _ts_of_current_safepoint = tty->time_stamp().seconds(); 8957764Skris } 9057542Skris 9157542Skris#if INCLUDE_ALL_GCS 9257542Skris if (UseConcMarkSweepGC) { 9358418Sobrien // In the future we should investigate whether CMS can use the 9459338Sobrien // more-general mechanism below. DLD (01/05). 9558280Skris ConcurrentMarkSweepThread::synchronize(false); 9657553Skris } else if (UseG1GC) { 9757542Skris SuspendibleThreadSet::synchronize(); 9857542Skris } 9957542Skris#endif // INCLUDE_ALL_GCS 10072679Skris 10165381Sobrien // By getting the Threads_lock, we assure that no threads are about to start or 10257553Skris // exit. It is released again in SafepointSynchronize::end(). 10357542Skris Threads_lock->lock(); 10458390Sdan 10535206Sphk assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state"); 10661744Sobrien 10761744Sobrien int nof_threads = Threads::number_of_threads(); 10861744Sobrien 10957458Smarkm if (TraceSafepoint) { 11062482Speter tty->print_cr("Safepoint synchronization initiated. (%d)", nof_threads); 11162482Speter } 11262482Speter 11362482Speter RuntimeService::record_safepoint_begin(); 11462482Speter 11562482Speter MutexLocker mu(Safepoint_lock); 11662482Speter 11762482Speter // Reset the count of active JNI critical threads 11862482Speter _current_jni_active_count = 0; 11963123Speter 12062482Speter // Set number of threads to wait for, before we initiate the callbacks 12157071Srwatson _waiting_to_block = nof_threads; 12257071Srwatson TryingToBlock = 0 ; 12357071Srwatson int still_running = nof_threads; 1241684Scsgr 1251684Scsgr // Save the starting time, so that it can be compared to see if this has taken 1261684Scsgr // too long to complete. 1279509Srgrimes jlong safepoint_limit_time; 1281697Sache timeout_error_printed = false; 1291697Sache 13020847Speter // PrintSafepointStatisticsTimeout can be specified separately. When 13120847Speter // specified, PrintSafepointStatistics will be set to true in 13220847Speter // deferred_initialize_stat method. The initialization has to be done 13320847Speter // early enough to avoid any races. See bug 6880029 for details. 13420847Speter if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) { 13520847Speter deferred_initialize_stat(); 13647318Sobrien } 13747430Sobrien 13820847Speter // Begin the process of bringing the system to a safepoint. 13920847Speter // Java threads can be in several different states and are 14014403Sasami // stopped by different mechanisms: 14114403Sasami // 14214403Sasami // 1. Running interpreted 14314403Sasami // The interpreter dispatch table is changed to force it to 14414403Sasami // check for a safepoint condition between bytecodes. 14514403Sasami // 2. Running in native code 1461697Sache // When returning from the native code, a Java thread must check 1471697Sache // the safepoint _state to see if we must block. If the 1481697Sache // VM thread sees a Java thread in native, it does 14925424Sandreas // not wait for this thread to block. The order of the memory 1501733Sadam // writes and reads of both the safepoint state and the Java 1511733Sadam // threads state is critical. In order to guarantee that the 15214102Sadam // memory writes are serialized with respect to each other, 15314102Sadam // the VM thread issues a memory barrier instruction 15414102Sadam // (on MP systems). In order to avoid the overhead of issuing 15514102Sadam // a memory barrier for each Java thread making native calls, each Java 1561733Sadam // thread performs a write to a single memory page after changing 1571740Sadam // the thread state. The VM thread performs a sequence of 1583023Srgrimes // mprotect OS calls which forces all previous writes from all 1591733Sadam // Java threads to be serialized. This is done in the 16018927Spst // os::serialize_thread_states() call. This has proven to be 16126522Sbde // much more efficient than executing a membar instruction 16226522Sbde // on every call to native code. 1631733Sadam // 3. Running compiled Code 16418927Spst // Compiled code reads a global (Safepoint Polling) page that 16549190Snik // is set to fault if we are trying to get to a safepoint. 16618927Spst // 4. Blocked 16749190Snik // A thread which is blocked will not be allowed to return from the 16849190Snik // block condition until the safepoint operation is complete. 16918928Spst // 5. In VM or Transitioning between states 17018927Spst // If a Java thread is currently running in the VM or transitioning 17126522Sbde // between states, the safepointing code will wait for the thread to 17226522Sbde // block itself when it attempts transitions to a new state. 17318927Spst // 17426522Sbde _state = _synchronizing; 17518927Spst OrderAccess::fence(); 17668310Sps 17768310Sps // Flush all thread states to memory 17868310Sps if (!UseMembar) { 17968310Sps os::serialize_thread_states(); 18018927Spst } 18168310Sps 18268310Sps // Make interpreter safepoint aware 1834224Sphk Interpreter::notice_safepoints(); 18415334Sasami 18515334Sasami if (DeferPollingPageLoopCount < 0) { 1863023Srgrimes // Make polling safepoint aware 1874224Sphk guarantee (PageArmed == 0, "invariant") ; 1883023Srgrimes PageArmed = 1 ; 1893023Srgrimes os::make_polling_page_unreadable(); 19015212Sasami } 19115212Sasami 19215212Sasami // Consider using active_processor_count() ... but that call is expensive. 19335221Sache int ncpus = os::processor_count() ; 19415212Sasami 19515334Sasami#ifdef ASSERT 19615334Sasami for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) { 19715334Sasami assert(cur->safepoint_state()->is_running(), "Illegal initial state"); 19815212Sasami // Clear the visited flag to ensure that the critical counts are collected properly. 19915334Sasami cur->set_visited_for_critical_count(false); 20015212Sasami } 20115212Sasami#endif // ASSERT 20229949Sjkh 20329949Sjkh if (SafepointTimeout) 20429949Sjkh safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS; 20529949Sjkh 20622638Sjkh // Iterate through all threads until it have been determined how to stop them all at a safepoint 20729949Sjkh unsigned int iterations = 0; 20829949Sjkh int steps = 0 ; 20929949Sjkh while(still_running > 0) { 21068481Sjkh for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) { 21168481Sjkh assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended"); 21268481Sjkh ThreadSafepointState *cur_state = cur->safepoint_state(); 21368481Sjkh if (cur_state->is_running()) { 21435222Sache cur_state->examine_state_of_thread(); 21535222Sache if (!cur_state->is_running()) { 21635222Sache still_running--; 21768481Sjkh // consider adjusting steps downward: 21868481Sjkh // steps = 0 21969820Sdes // steps -= NNN 22068481Sjkh // steps >>= 1 22168481Sjkh // steps = MIN(steps, 2000-100) 22268481Sjkh // if (iterations != 0) steps -= NNN 22368481Sjkh } 22468481Sjkh if (TraceSafepoint && Verbose) cur_state->print(); 22536263Sjkh } 22624951Sasami } 22724951Sasami 22824951Sasami if (PrintSafepointStatistics && iterations == 0) { 22924951Sasami begin_statistics(nof_threads, still_running); 23024951Sasami } 23124951Sasami 23224951Sasami if (still_running > 0) { 23342876Sasami // Check for if it takes to long 23424951Sasami if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) { 23524951Sasami print_safepoint_timeout(_spinning_timeout); 23624951Sasami } 23724951Sasami 23824951Sasami // Spin to avoid context switching. 23924951Sasami // There's a tension between allowing the mutators to run (and rendezvous) 24024951Sasami // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that 24124951Sasami // a mutator might otherwise use profitably to reach a safepoint. Excessive 24224951Sasami // spinning by the VM thread on a saturated system can increase rendezvous latency. 24324951Sasami // Blocking or yielding incur their own penalties in the form of context switching 24424951Sasami // and the resultant loss of $ residency. 24533880Sfenner // 24624951Sasami // Further complicating matters is that yield() does not work as naively expected 24724951Sasami // on many platforms -- yield() does not guarantee that any other ready threads 24824951Sasami // will run. As such we revert to naked_short_sleep() after some number of iterations. 24967431Sknu // nakes_short_sleep() is implemented as a short unconditional sleep. 25024951Sasami // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping 25133880Sfenner // can actually increase the time it takes the VM thread to detect that a system-wide 25267431Sknu // stop-the-world safepoint has been reached. In a pathological scenario such as that 25368164Srse // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe. 25433880Sfenner // In that case the mutators will be stalled waiting for the safepoint to complete and the 25533880Sfenner // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread 25647726Sbillf // will eventually wake up and detect that all mutators are safe, at which point 25767431Sknu // we'll again make progress. 25842876Sasami // 25942876Sasami // Beware too that that the VMThread typically runs at elevated priority. 26042876Sasami // Its default priority is higher than the default mutator priority. 26144748Sbillf // Obviously, this complicates spinning. 26244748Sbillf // 26367491Sknu // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0). 26467491Sknu // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will. 26567431Sknu // 26667431Sknu // See the comments in synchronizer.cpp for additional remarks on spinning. 26724951Sasami // 26867431Sknu // In the future we might: 26967431Sknu // 1. Modify the safepoint scheme to avoid potentially unbounded spinning. 27067431Sknu // This is tricky as the path used by a thread exiting the JVM (say on 27167431Sknu // on JNI call-out) simply stores into its state field. The burden 27267431Sknu // is placed on the VM thread, which must poll (spin). 27367431Sknu // 2. Find something useful to do while spinning. If the safepoint is GC-related 27424951Sasami // we might aggressively scan the stacks of threads that are already safe. 27567431Sknu // 3. Use Solaris schedctl to examine the state of the still-running mutators. 27667431Sknu // If all the mutators are ONPROC there's no reason to sleep or yield. 2773241Scsgr // 4. YieldTo() any still-running mutators that are ready but OFFPROC. 27829931Smarkm // 5. Check system saturation. If the system is not fully saturated then 2793241Scsgr // simply spin and avoid sleep/yield. 28029931Smarkm // 6. As still-running mutators rendezvous they could unpark the sleeping 28110758Sache // VMthread. This works well for still-running mutators that become 28210758Sache // safe. The VMthread must still poll for mutators that call-out. 28356553Smarkm // 7. Drive the policy on time-since-begin instead of iterations. 28456553Smarkm // 8. Consider making the spin duration a function of the # of CPUs: 28556553Smarkm // Spin = (((ncpus-1) * M) + K) + F(still_running) 28656553Smarkm // Alternately, instead of counting iterations of the outer loop 28756553Smarkm // we could count the # of threads visited in the inner loop, above. 28856553Smarkm // 9. On windows consider using the return value from SwitchThreadTo() 28956553Smarkm // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions. 29056553Smarkm 29156553Smarkm if (int(iterations) == DeferPollingPageLoopCount) { 29256553Smarkm guarantee (PageArmed == 0, "invariant") ; 29338003Sdima PageArmed = 1 ; 29456553Smarkm os::make_polling_page_unreadable(); 29556553Smarkm } 29638003Sdima 29756553Smarkm // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or 29838003Sdima // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus) 29938003Sdima ++steps ; 30037162Sjkh if (ncpus > 1 && steps < SafepointSpinBeforeYield) { 30137162Sjkh SpinPause() ; // MP-Polite spin 30237162Sjkh } else 30310758Sache if (steps < DeferThrSuspendLoopCount) { 30410758Sache os::naked_yield() ; 30518716Sache } else { 30620545Sache os::naked_short_sleep(1); 30749777Ssheldonh } 30864605Sjoe 30918716Sache iterations ++ ; 31018716Sache } 31147651Sbillf assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long"); 31254670Sbillf } 31324225Sjoerg assert(still_running == 0, "sanity check"); 31424225Sjoerg 31524225Sjoerg if (PrintSafepointStatistics) { 31624225Sjoerg update_statistics_on_spin_end(); 31724225Sjoerg } 31824225Sjoerg 31924225Sjoerg // wait until all threads are stopped 32058449Snik while (_waiting_to_block > 0) { 32158449Snik if (TraceSafepoint) tty->print_cr("Waiting for %d thread(s) to block", _waiting_to_block); 32258449Snik if (!SafepointTimeout || timeout_error_printed) { 32358449Snik Safepoint_lock->wait(true); // true, means with no safepoint checks 32458449Snik } else { 32558449Snik // Compute remaining time 32665970Sgshapiro jlong remaining_time = safepoint_limit_time - os::javaTimeNanos(); 32765970Sgshapiro 32865970Sgshapiro // If there is no remaining time, then there is an error 32972846Sgshapiro if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) { 33072846Sgshapiro print_safepoint_timeout(_blocking_timeout); 33172846Sgshapiro } 33272846Sgshapiro } 33372846Sgshapiro } 33472846Sgshapiro assert(_waiting_to_block == 0, "sanity check"); 33572846Sgshapiro 33672846Sgshapiro#ifndef PRODUCT 33765970Sgshapiro if (SafepointTimeout) { 33865970Sgshapiro jlong current_time = os::javaTimeNanos(); 33965970Sgshapiro if (safepoint_limit_time < current_time) { 34065970Sgshapiro tty->print_cr("# SafepointSynchronize: Finished after " 34165970Sgshapiro INT64_FORMAT_W(6) " ms", 34265970Sgshapiro ((current_time - safepoint_limit_time) / MICROUNITS + 34365970Sgshapiro SafepointTimeoutDelay)); 34465970Sgshapiro } 34569380Sgshapiro } 34669380Sgshapiro#endif 34769380Sgshapiro 34869380Sgshapiro assert((_safepoint_counter & 0x1) == 0, "must be even"); 34969380Sgshapiro assert(Threads_lock->owned_by_self(), "must hold Threads_lock"); 35069380Sgshapiro _safepoint_counter ++; 35165970Sgshapiro 35265970Sgshapiro // Record state 35365970Sgshapiro _state = _synchronized; 35465970Sgshapiro 355 OrderAccess::fence(); 356 357#ifdef ASSERT 358 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) { 359 // make sure all the threads were visited 360 assert(cur->was_visited_for_critical_count(), "missed a thread"); 361 } 362#endif // ASSERT 363 364 // Update the count of active JNI critical regions 365 GC_locker::set_jni_lock_count(_current_jni_active_count); 366 367 if (TraceSafepoint) { 368 VM_Operation *op = VMThread::vm_operation(); 369 tty->print_cr("Entering safepoint region: %s", (op != NULL) ? op->name() : "no vm operation"); 370 } 371 372 RuntimeService::record_safepoint_synchronized(); 373 if (PrintSafepointStatistics) { 374 update_statistics_on_sync_end(os::javaTimeNanos()); 375 } 376 377 // Call stuff that needs to be run when a safepoint is just about to be completed 378 do_cleanup_tasks(); 379 380 if (PrintSafepointStatistics) { 381 // Record how much time spend on the above cleanup tasks 382 update_statistics_on_cleanup_end(os::javaTimeNanos()); 383 } 384} 385 386// Wake up all threads, so they are ready to resume execution after the safepoint 387// operation has been carried out 388void SafepointSynchronize::end() { 389 390 assert(Threads_lock->owned_by_self(), "must hold Threads_lock"); 391 assert((_safepoint_counter & 0x1) == 1, "must be odd"); 392 _safepoint_counter ++; 393 // memory fence isn't required here since an odd _safepoint_counter 394 // value can do no harm and a fence is issued below anyway. 395 396 DEBUG_ONLY(Thread* myThread = Thread::current();) 397 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint"); 398 399 if (PrintSafepointStatistics) { 400 end_statistics(os::javaTimeNanos()); 401 } 402 403#ifdef ASSERT 404 // A pending_exception cannot be installed during a safepoint. The threads 405 // may install an async exception after they come back from a safepoint into 406 // pending_exception after they unblock. But that should happen later. 407 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) { 408 assert (!(cur->has_pending_exception() && 409 cur->safepoint_state()->is_at_poll_safepoint()), 410 "safepoint installed a pending exception"); 411 } 412#endif // ASSERT 413 414 if (PageArmed) { 415 // Make polling safepoint aware 416 os::make_polling_page_readable(); 417 PageArmed = 0 ; 418 } 419 420 // Remove safepoint check from interpreter 421 Interpreter::ignore_safepoints(); 422 423 { 424 MutexLocker mu(Safepoint_lock); 425 426 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization"); 427 428 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method 429 // when they get restarted. 430 _state = _not_synchronized; 431 OrderAccess::fence(); 432 433 if (TraceSafepoint) { 434 tty->print_cr("Leaving safepoint region"); 435 } 436 437 // Start suspended threads 438 for(JavaThread *current = Threads::first(); current; current = current->next()) { 439 // A problem occurring on Solaris is when attempting to restart threads 440 // the first #cpus - 1 go well, but then the VMThread is preempted when we get 441 // to the next one (since it has been running the longest). We then have 442 // to wait for a cpu to become available before we can continue restarting 443 // threads. 444 // FIXME: This causes the performance of the VM to degrade when active and with 445 // large numbers of threads. Apparently this is due to the synchronous nature 446 // of suspending threads. 447 // 448 // TODO-FIXME: the comments above are vestigial and no longer apply. 449 // Furthermore, using solaris' schedctl in this particular context confers no benefit 450 if (VMThreadHintNoPreempt) { 451 os::hint_no_preempt(); 452 } 453 ThreadSafepointState* cur_state = current->safepoint_state(); 454 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint"); 455 cur_state->restart(); 456 assert(cur_state->is_running(), "safepoint state has not been reset"); 457 } 458 459 RuntimeService::record_safepoint_end(); 460 461 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads 462 // blocked in signal_thread_blocked 463 Threads_lock->unlock(); 464 465 } 466#if INCLUDE_ALL_GCS 467 // If there are any concurrent GC threads resume them. 468 if (UseConcMarkSweepGC) { 469 ConcurrentMarkSweepThread::desynchronize(false); 470 } else if (UseG1GC) { 471 SuspendibleThreadSet::desynchronize(); 472 } 473#endif // INCLUDE_ALL_GCS 474 // record this time so VMThread can keep track how much time has elapsed 475 // since last safepoint. 476 _end_of_last_safepoint = os::javaTimeMillis(); 477} 478 479bool SafepointSynchronize::is_cleanup_needed() { 480 // Need a safepoint if some inline cache buffers is non-empty 481 if (!InlineCacheBuffer::is_empty()) return true; 482 return false; 483} 484 485 486 487// Various cleaning tasks that should be done periodically at safepoints 488void SafepointSynchronize::do_cleanup_tasks() { 489 { 490 TraceTime t1("deflating idle monitors", TraceSafepointCleanupTime); 491 ObjectSynchronizer::deflate_idle_monitors(); 492 } 493 494 { 495 TraceTime t2("updating inline caches", TraceSafepointCleanupTime); 496 InlineCacheBuffer::update_inline_caches(); 497 } 498 { 499 TraceTime t3("compilation policy safepoint handler", TraceSafepointCleanupTime); 500 CompilationPolicy::policy()->do_safepoint_work(); 501 } 502 503 { 504 TraceTime t4("mark nmethods", TraceSafepointCleanupTime); 505 NMethodSweeper::mark_active_nmethods(); 506 } 507 508 if (SymbolTable::needs_rehashing()) { 509 TraceTime t5("rehashing symbol table", TraceSafepointCleanupTime); 510 SymbolTable::rehash_table(); 511 } 512 513 if (StringTable::needs_rehashing()) { 514 TraceTime t6("rehashing string table", TraceSafepointCleanupTime); 515 StringTable::rehash_table(); 516 } 517 518 // rotate log files? 519 if (UseGCLogFileRotation) { 520 gclog_or_tty->rotate_log(false); 521 } 522 523 { 524 // CMS delays purging the CLDG until the beginning of the next safepoint and to 525 // make sure concurrent sweep is done 526 TraceTime t7("purging class loader data graph", TraceSafepointCleanupTime); 527 ClassLoaderDataGraph::purge_if_needed(); 528 } 529} 530 531 532bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) { 533 switch(state) { 534 case _thread_in_native: 535 // native threads are safe if they have no java stack or have walkable stack 536 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable(); 537 538 // blocked threads should have already have walkable stack 539 case _thread_blocked: 540 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable"); 541 return true; 542 543 default: 544 return false; 545 } 546} 547 548 549// See if the thread is running inside a lazy critical native and 550// update the thread critical count if so. Also set a suspend flag to 551// cause the native wrapper to return into the JVM to do the unlock 552// once the native finishes. 553void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) { 554 if (state == _thread_in_native && 555 thread->has_last_Java_frame() && 556 thread->frame_anchor()->walkable()) { 557 // This thread might be in a critical native nmethod so look at 558 // the top of the stack and increment the critical count if it 559 // is. 560 frame wrapper_frame = thread->last_frame(); 561 CodeBlob* stub_cb = wrapper_frame.cb(); 562 if (stub_cb != NULL && 563 stub_cb->is_nmethod() && 564 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) { 565 // A thread could potentially be in a critical native across 566 // more than one safepoint, so only update the critical state on 567 // the first one. When it returns it will perform the unlock. 568 if (!thread->do_critical_native_unlock()) { 569#ifdef ASSERT 570 if (!thread->in_critical()) { 571 GC_locker::increment_debug_jni_lock_count(); 572 } 573#endif 574 thread->enter_critical(); 575 // Make sure the native wrapper calls back on return to 576 // perform the needed critical unlock. 577 thread->set_critical_native_unlock(); 578 } 579 } 580 } 581} 582 583 584 585// ------------------------------------------------------------------------------------------------------- 586// Implementation of Safepoint callback point 587 588void SafepointSynchronize::block(JavaThread *thread) { 589 assert(thread != NULL, "thread must be set"); 590 assert(thread->is_Java_thread(), "not a Java thread"); 591 592 // Threads shouldn't block if they are in the middle of printing, but... 593 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id()); 594 595 // Only bail from the block() call if the thread is gone from the 596 // thread list; starting to exit should still block. 597 if (thread->is_terminated()) { 598 // block current thread if we come here from native code when VM is gone 599 thread->block_if_vm_exited(); 600 601 // otherwise do nothing 602 return; 603 } 604 605 JavaThreadState state = thread->thread_state(); 606 thread->frame_anchor()->make_walkable(thread); 607 608 // Check that we have a valid thread_state at this point 609 switch(state) { 610 case _thread_in_vm_trans: 611 case _thread_in_Java: // From compiled code 612 613 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case, 614 // we pretend we are still in the VM. 615 thread->set_thread_state(_thread_in_vm); 616 617 if (is_synchronizing()) { 618 Atomic::inc (&TryingToBlock) ; 619 } 620 621 // We will always be holding the Safepoint_lock when we are examine the state 622 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and 623 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code 624 Safepoint_lock->lock_without_safepoint_check(); 625 if (is_synchronizing()) { 626 // Decrement the number of threads to wait for and signal vm thread 627 assert(_waiting_to_block > 0, "sanity check"); 628 _waiting_to_block--; 629 thread->safepoint_state()->set_has_called_back(true); 630 631 DEBUG_ONLY(thread->set_visited_for_critical_count(true)); 632 if (thread->in_critical()) { 633 // Notice that this thread is in a critical section 634 increment_jni_active_count(); 635 } 636 637 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread 638 if (_waiting_to_block == 0) { 639 Safepoint_lock->notify_all(); 640 } 641 } 642 643 // We transition the thread to state _thread_blocked here, but 644 // we can't do our usual check for external suspension and then 645 // self-suspend after the lock_without_safepoint_check() call 646 // below because we are often called during transitions while 647 // we hold different locks. That would leave us suspended while 648 // holding a resource which results in deadlocks. 649 thread->set_thread_state(_thread_blocked); 650 Safepoint_lock->unlock(); 651 652 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during 653 // the entire safepoint, the threads will all line up here during the safepoint. 654 Threads_lock->lock_without_safepoint_check(); 655 // restore original state. This is important if the thread comes from compiled code, so it 656 // will continue to execute with the _thread_in_Java state. 657 thread->set_thread_state(state); 658 Threads_lock->unlock(); 659 break; 660 661 case _thread_in_native_trans: 662 case _thread_blocked_trans: 663 case _thread_new_trans: 664 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) { 665 thread->print_thread_state(); 666 fatal("Deadlock in safepoint code. " 667 "Should have called back to the VM before blocking."); 668 } 669 670 // We transition the thread to state _thread_blocked here, but 671 // we can't do our usual check for external suspension and then 672 // self-suspend after the lock_without_safepoint_check() call 673 // below because we are often called during transitions while 674 // we hold different locks. That would leave us suspended while 675 // holding a resource which results in deadlocks. 676 thread->set_thread_state(_thread_blocked); 677 678 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence, 679 // the safepoint code might still be waiting for it to block. We need to change the state here, 680 // so it can see that it is at a safepoint. 681 682 // Block until the safepoint operation is completed. 683 Threads_lock->lock_without_safepoint_check(); 684 685 // Restore state 686 thread->set_thread_state(state); 687 688 Threads_lock->unlock(); 689 break; 690 691 default: 692 fatal("Illegal threadstate encountered: %d", state); 693 } 694 695 // Check for pending. async. exceptions or suspends - except if the 696 // thread was blocked inside the VM. has_special_runtime_exit_condition() 697 // is called last since it grabs a lock and we only want to do that when 698 // we must. 699 // 700 // Note: we never deliver an async exception at a polling point as the 701 // compiler may not have an exception handler for it. The polling 702 // code will notice the async and deoptimize and the exception will 703 // be delivered. (Polling at a return point is ok though). Sure is 704 // a lot of bother for a deprecated feature... 705 // 706 // We don't deliver an async exception if the thread state is 707 // _thread_in_native_trans so JNI functions won't be called with 708 // a surprising pending exception. If the thread state is going back to java, 709 // async exception is checked in check_special_condition_for_native_trans(). 710 711 if (state != _thread_blocked_trans && 712 state != _thread_in_vm_trans && 713 thread->has_special_runtime_exit_condition()) { 714 thread->handle_special_runtime_exit_condition( 715 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans)); 716 } 717} 718 719// ------------------------------------------------------------------------------------------------------ 720// Exception handlers 721 722 723void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) { 724 assert(thread->is_Java_thread(), "polling reference encountered by VM thread"); 725 assert(thread->thread_state() == _thread_in_Java, "should come from Java code"); 726 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization"); 727 728 if (ShowSafepointMsgs) { 729 tty->print("handle_polling_page_exception: "); 730 } 731 732 if (PrintSafepointStatistics) { 733 inc_page_trap_count(); 734 } 735 736 ThreadSafepointState* state = thread->safepoint_state(); 737 738 state->handle_polling_page_exception(); 739} 740 741 742void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) { 743 if (!timeout_error_printed) { 744 timeout_error_printed = true; 745 // Print out the thread info which didn't reach the safepoint for debugging 746 // purposes (useful when there are lots of threads in the debugger). 747 tty->cr(); 748 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:"); 749 if (reason == _spinning_timeout) { 750 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint."); 751 } else if (reason == _blocking_timeout) { 752 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop."); 753 } 754 755 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:"); 756 ThreadSafepointState *cur_state; 757 ResourceMark rm; 758 for(JavaThread *cur_thread = Threads::first(); cur_thread; 759 cur_thread = cur_thread->next()) { 760 cur_state = cur_thread->safepoint_state(); 761 762 if (cur_thread->thread_state() != _thread_blocked && 763 ((reason == _spinning_timeout && cur_state->is_running()) || 764 (reason == _blocking_timeout && !cur_state->has_called_back()))) { 765 tty->print("# "); 766 cur_thread->print(); 767 tty->cr(); 768 } 769 } 770 tty->print_cr("# SafepointSynchronize::begin: (End of list)"); 771 } 772 773 // To debug the long safepoint, specify both DieOnSafepointTimeout & 774 // ShowMessageBoxOnError. 775 if (DieOnSafepointTimeout) { 776 VM_Operation *op = VMThread::vm_operation(); 777 fatal("Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.", 778 SafepointTimeoutDelay, 779 op != NULL ? op->name() : "no vm operation"); 780 } 781} 782 783 784// ------------------------------------------------------------------------------------------------------- 785// Implementation of ThreadSafepointState 786 787ThreadSafepointState::ThreadSafepointState(JavaThread *thread) { 788 _thread = thread; 789 _type = _running; 790 _has_called_back = false; 791 _at_poll_safepoint = false; 792} 793 794void ThreadSafepointState::create(JavaThread *thread) { 795 ThreadSafepointState *state = new ThreadSafepointState(thread); 796 thread->set_safepoint_state(state); 797} 798 799void ThreadSafepointState::destroy(JavaThread *thread) { 800 if (thread->safepoint_state()) { 801 delete(thread->safepoint_state()); 802 thread->set_safepoint_state(NULL); 803 } 804} 805 806void ThreadSafepointState::examine_state_of_thread() { 807 assert(is_running(), "better be running or just have hit safepoint poll"); 808 809 JavaThreadState state = _thread->thread_state(); 810 811 // Save the state at the start of safepoint processing. 812 _orig_thread_state = state; 813 814 // Check for a thread that is suspended. Note that thread resume tries 815 // to grab the Threads_lock which we own here, so a thread cannot be 816 // resumed during safepoint synchronization. 817 818 // We check to see if this thread is suspended without locking to 819 // avoid deadlocking with a third thread that is waiting for this 820 // thread to be suspended. The third thread can notice the safepoint 821 // that we're trying to start at the beginning of its SR_lock->wait() 822 // call. If that happens, then the third thread will block on the 823 // safepoint while still holding the underlying SR_lock. We won't be 824 // able to get the SR_lock and we'll deadlock. 825 // 826 // We don't need to grab the SR_lock here for two reasons: 827 // 1) The suspend flags are both volatile and are set with an 828 // Atomic::cmpxchg() call so we should see the suspended 829 // state right away. 830 // 2) We're being called from the safepoint polling loop; if 831 // we don't see the suspended state on this iteration, then 832 // we'll come around again. 833 // 834 bool is_suspended = _thread->is_ext_suspended(); 835 if (is_suspended) { 836 roll_forward(_at_safepoint); 837 return; 838 } 839 840 // Some JavaThread states have an initial safepoint state of 841 // running, but are actually at a safepoint. We will happily 842 // agree and update the safepoint state here. 843 if (SafepointSynchronize::safepoint_safe(_thread, state)) { 844 SafepointSynchronize::check_for_lazy_critical_native(_thread, state); 845 roll_forward(_at_safepoint); 846 return; 847 } 848 849 if (state == _thread_in_vm) { 850 roll_forward(_call_back); 851 return; 852 } 853 854 // All other thread states will continue to run until they 855 // transition and self-block in state _blocked 856 // Safepoint polling in compiled code causes the Java threads to do the same. 857 // Note: new threads may require a malloc so they must be allowed to finish 858 859 assert(is_running(), "examine_state_of_thread on non-running thread"); 860 return; 861} 862 863// Returns true is thread could not be rolled forward at present position. 864void ThreadSafepointState::roll_forward(suspend_type type) { 865 _type = type; 866 867 switch(_type) { 868 case _at_safepoint: 869 SafepointSynchronize::signal_thread_at_safepoint(); 870 DEBUG_ONLY(_thread->set_visited_for_critical_count(true)); 871 if (_thread->in_critical()) { 872 // Notice that this thread is in a critical section 873 SafepointSynchronize::increment_jni_active_count(); 874 } 875 break; 876 877 case _call_back: 878 set_has_called_back(false); 879 break; 880 881 case _running: 882 default: 883 ShouldNotReachHere(); 884 } 885} 886 887void ThreadSafepointState::restart() { 888 switch(type()) { 889 case _at_safepoint: 890 case _call_back: 891 break; 892 893 case _running: 894 default: 895 tty->print_cr("restart thread " INTPTR_FORMAT " with state %d", 896 _thread, _type); 897 _thread->print(); 898 ShouldNotReachHere(); 899 } 900 _type = _running; 901 set_has_called_back(false); 902} 903 904 905void ThreadSafepointState::print_on(outputStream *st) const { 906 const char *s; 907 908 switch(_type) { 909 case _running : s = "_running"; break; 910 case _at_safepoint : s = "_at_safepoint"; break; 911 case _call_back : s = "_call_back"; break; 912 default: 913 ShouldNotReachHere(); 914 } 915 916 st->print_cr("Thread: " INTPTR_FORMAT 917 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d", 918 _thread, _thread->osthread()->thread_id(), s, _has_called_back, 919 _at_poll_safepoint); 920 921 _thread->print_thread_state_on(st); 922} 923 924 925// --------------------------------------------------------------------------------------------------------------------- 926 927// Block the thread at the safepoint poll or poll return. 928void ThreadSafepointState::handle_polling_page_exception() { 929 930 // Check state. block() will set thread state to thread_in_vm which will 931 // cause the safepoint state _type to become _call_back. 932 assert(type() == ThreadSafepointState::_running, 933 "polling page exception on thread not running state"); 934 935 // Step 1: Find the nmethod from the return address 936 if (ShowSafepointMsgs && Verbose) { 937 tty->print_cr("Polling page exception at " INTPTR_FORMAT, thread()->saved_exception_pc()); 938 } 939 address real_return_addr = thread()->saved_exception_pc(); 940 941 CodeBlob *cb = CodeCache::find_blob(real_return_addr); 942 assert(cb != NULL && cb->is_nmethod(), "return address should be in nmethod"); 943 nmethod* nm = (nmethod*)cb; 944 945 // Find frame of caller 946 frame stub_fr = thread()->last_frame(); 947 CodeBlob* stub_cb = stub_fr.cb(); 948 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub"); 949 RegisterMap map(thread(), true); 950 frame caller_fr = stub_fr.sender(&map); 951 952 // Should only be poll_return or poll 953 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" ); 954 955 // This is a poll immediately before a return. The exception handling code 956 // has already had the effect of causing the return to occur, so the execution 957 // will continue immediately after the call. In addition, the oopmap at the 958 // return point does not mark the return value as an oop (if it is), so 959 // it needs a handle here to be updated. 960 if( nm->is_at_poll_return(real_return_addr) ) { 961 // See if return type is an oop. 962 bool return_oop = nm->method()->is_returning_oop(); 963 Handle return_value; 964 if (return_oop) { 965 // The oop result has been saved on the stack together with all 966 // the other registers. In order to preserve it over GCs we need 967 // to keep it in a handle. 968 oop result = caller_fr.saved_oop_result(&map); 969 assert(result == NULL || result->is_oop(), "must be oop"); 970 return_value = Handle(thread(), result); 971 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer"); 972 } 973 974 // Block the thread 975 SafepointSynchronize::block(thread()); 976 977 // restore oop result, if any 978 if (return_oop) { 979 caller_fr.set_saved_oop_result(&map, return_value()); 980 } 981 } 982 983 // This is a safepoint poll. Verify the return address and block. 984 else { 985 set_at_poll_safepoint(true); 986 987 // verify the blob built the "return address" correctly 988 assert(real_return_addr == caller_fr.pc(), "must match"); 989 990 // Block the thread 991 SafepointSynchronize::block(thread()); 992 set_at_poll_safepoint(false); 993 994 // If we have a pending async exception deoptimize the frame 995 // as otherwise we may never deliver it. 996 if (thread()->has_async_condition()) { 997 ThreadInVMfromJavaNoAsyncException __tiv(thread()); 998 Deoptimization::deoptimize_frame(thread(), caller_fr.id()); 999 } 1000 1001 // If an exception has been installed we must check for a pending deoptimization 1002 // Deoptimize frame if exception has been thrown. 1003 1004 if (thread()->has_pending_exception() ) { 1005 RegisterMap map(thread(), true); 1006 frame caller_fr = stub_fr.sender(&map); 1007 if (caller_fr.is_deoptimized_frame()) { 1008 // The exception patch will destroy registers that are still 1009 // live and will be needed during deoptimization. Defer the 1010 // Async exception should have deferred the exception until the 1011 // next safepoint which will be detected when we get into 1012 // the interpreter so if we have an exception now things 1013 // are messed up. 1014 1015 fatal("Exception installed and deoptimization is pending"); 1016 } 1017 } 1018 } 1019} 1020 1021 1022// 1023// Statistics & Instrumentations 1024// 1025SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL; 1026jlong SafepointSynchronize::_safepoint_begin_time = 0; 1027int SafepointSynchronize::_cur_stat_index = 0; 1028julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating]; 1029julong SafepointSynchronize::_coalesced_vmop_count = 0; 1030jlong SafepointSynchronize::_max_sync_time = 0; 1031jlong SafepointSynchronize::_max_vmop_time = 0; 1032float SafepointSynchronize::_ts_of_current_safepoint = 0.0f; 1033 1034static jlong cleanup_end_time = 0; 1035static bool need_to_track_page_armed_status = false; 1036static bool init_done = false; 1037 1038// Helper method to print the header. 1039static void print_header() { 1040 tty->print(" vmop " 1041 "[threads: total initially_running wait_to_block] "); 1042 tty->print("[time: spin block sync cleanup vmop] "); 1043 1044 // no page armed status printed out if it is always armed. 1045 if (need_to_track_page_armed_status) { 1046 tty->print("page_armed "); 1047 } 1048 1049 tty->print_cr("page_trap_count"); 1050} 1051 1052void SafepointSynchronize::deferred_initialize_stat() { 1053 if (init_done) return; 1054 1055 if (PrintSafepointStatisticsCount <= 0) { 1056 fatal("Wrong PrintSafepointStatisticsCount"); 1057 } 1058 1059 // If PrintSafepointStatisticsTimeout is specified, the statistics data will 1060 // be printed right away, in which case, _safepoint_stats will regress to 1061 // a single element array. Otherwise, it is a circular ring buffer with default 1062 // size of PrintSafepointStatisticsCount. 1063 int stats_array_size; 1064 if (PrintSafepointStatisticsTimeout > 0) { 1065 stats_array_size = 1; 1066 PrintSafepointStatistics = true; 1067 } else { 1068 stats_array_size = PrintSafepointStatisticsCount; 1069 } 1070 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size 1071 * sizeof(SafepointStats), mtInternal); 1072 guarantee(_safepoint_stats != NULL, 1073 "not enough memory for safepoint instrumentation data"); 1074 1075 if (DeferPollingPageLoopCount >= 0) { 1076 need_to_track_page_armed_status = true; 1077 } 1078 init_done = true; 1079} 1080 1081void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) { 1082 assert(init_done, "safepoint statistics array hasn't been initialized"); 1083 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1084 1085 spstat->_time_stamp = _ts_of_current_safepoint; 1086 1087 VM_Operation *op = VMThread::vm_operation(); 1088 spstat->_vmop_type = (op != NULL ? op->type() : -1); 1089 if (op != NULL) { 1090 _safepoint_reasons[spstat->_vmop_type]++; 1091 } 1092 1093 spstat->_nof_total_threads = nof_threads; 1094 spstat->_nof_initial_running_threads = nof_running; 1095 spstat->_nof_threads_hit_page_trap = 0; 1096 1097 // Records the start time of spinning. The real time spent on spinning 1098 // will be adjusted when spin is done. Same trick is applied for time 1099 // spent on waiting for threads to block. 1100 if (nof_running != 0) { 1101 spstat->_time_to_spin = os::javaTimeNanos(); 1102 } else { 1103 spstat->_time_to_spin = 0; 1104 } 1105} 1106 1107void SafepointSynchronize::update_statistics_on_spin_end() { 1108 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1109 1110 jlong cur_time = os::javaTimeNanos(); 1111 1112 spstat->_nof_threads_wait_to_block = _waiting_to_block; 1113 if (spstat->_nof_initial_running_threads != 0) { 1114 spstat->_time_to_spin = cur_time - spstat->_time_to_spin; 1115 } 1116 1117 if (need_to_track_page_armed_status) { 1118 spstat->_page_armed = (PageArmed == 1); 1119 } 1120 1121 // Records the start time of waiting for to block. Updated when block is done. 1122 if (_waiting_to_block != 0) { 1123 spstat->_time_to_wait_to_block = cur_time; 1124 } else { 1125 spstat->_time_to_wait_to_block = 0; 1126 } 1127} 1128 1129void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) { 1130 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1131 1132 if (spstat->_nof_threads_wait_to_block != 0) { 1133 spstat->_time_to_wait_to_block = end_time - 1134 spstat->_time_to_wait_to_block; 1135 } 1136 1137 // Records the end time of sync which will be used to calculate the total 1138 // vm operation time. Again, the real time spending in syncing will be deducted 1139 // from the start of the sync time later when end_statistics is called. 1140 spstat->_time_to_sync = end_time - _safepoint_begin_time; 1141 if (spstat->_time_to_sync > _max_sync_time) { 1142 _max_sync_time = spstat->_time_to_sync; 1143 } 1144 1145 spstat->_time_to_do_cleanups = end_time; 1146} 1147 1148void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) { 1149 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1150 1151 // Record how long spent in cleanup tasks. 1152 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups; 1153 1154 cleanup_end_time = end_time; 1155} 1156 1157void SafepointSynchronize::end_statistics(jlong vmop_end_time) { 1158 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1159 1160 // Update the vm operation time. 1161 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time; 1162 if (spstat->_time_to_exec_vmop > _max_vmop_time) { 1163 _max_vmop_time = spstat->_time_to_exec_vmop; 1164 } 1165 // Only the sync time longer than the specified 1166 // PrintSafepointStatisticsTimeout will be printed out right away. 1167 // By default, it is -1 meaning all samples will be put into the list. 1168 if ( PrintSafepointStatisticsTimeout > 0) { 1169 if (spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) { 1170 print_statistics(); 1171 } 1172 } else { 1173 // The safepoint statistics will be printed out when the _safepoin_stats 1174 // array fills up. 1175 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) { 1176 print_statistics(); 1177 _cur_stat_index = 0; 1178 } else { 1179 _cur_stat_index++; 1180 } 1181 } 1182} 1183 1184void SafepointSynchronize::print_statistics() { 1185 SafepointStats* sstats = _safepoint_stats; 1186 1187 for (int index = 0; index <= _cur_stat_index; index++) { 1188 if (index % 30 == 0) { 1189 print_header(); 1190 } 1191 sstats = &_safepoint_stats[index]; 1192 tty->print("%.3f: ", sstats->_time_stamp); 1193 tty->print("%-26s [" 1194 INT32_FORMAT_W(8) INT32_FORMAT_W(11) INT32_FORMAT_W(15) 1195 " ] ", 1196 sstats->_vmop_type == -1 ? "no vm operation" : 1197 VM_Operation::name(sstats->_vmop_type), 1198 sstats->_nof_total_threads, 1199 sstats->_nof_initial_running_threads, 1200 sstats->_nof_threads_wait_to_block); 1201 // "/ MICROUNITS " is to convert the unit from nanos to millis. 1202 tty->print(" [" 1203 INT64_FORMAT_W(6) INT64_FORMAT_W(6) 1204 INT64_FORMAT_W(6) INT64_FORMAT_W(6) 1205 INT64_FORMAT_W(6) " ] ", 1206 sstats->_time_to_spin / MICROUNITS, 1207 sstats->_time_to_wait_to_block / MICROUNITS, 1208 sstats->_time_to_sync / MICROUNITS, 1209 sstats->_time_to_do_cleanups / MICROUNITS, 1210 sstats->_time_to_exec_vmop / MICROUNITS); 1211 1212 if (need_to_track_page_armed_status) { 1213 tty->print(INT32_FORMAT " ", sstats->_page_armed); 1214 } 1215 tty->print_cr(INT32_FORMAT " ", sstats->_nof_threads_hit_page_trap); 1216 } 1217} 1218 1219// This method will be called when VM exits. It will first call 1220// print_statistics to print out the rest of the sampling. Then 1221// it tries to summarize the sampling. 1222void SafepointSynchronize::print_stat_on_exit() { 1223 if (_safepoint_stats == NULL) return; 1224 1225 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1226 1227 // During VM exit, end_statistics may not get called and in that 1228 // case, if the sync time is less than PrintSafepointStatisticsTimeout, 1229 // don't print it out. 1230 // Approximate the vm op time. 1231 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop = 1232 os::javaTimeNanos() - cleanup_end_time; 1233 1234 if ( PrintSafepointStatisticsTimeout < 0 || 1235 spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) { 1236 print_statistics(); 1237 } 1238 tty->cr(); 1239 1240 // Print out polling page sampling status. 1241 if (!need_to_track_page_armed_status) { 1242 tty->print_cr("Polling page always armed"); 1243 } else { 1244 tty->print_cr("Defer polling page loop count = %d\n", 1245 DeferPollingPageLoopCount); 1246 } 1247 1248 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) { 1249 if (_safepoint_reasons[index] != 0) { 1250 tty->print_cr("%-26s" UINT64_FORMAT_W(10), VM_Operation::name(index), 1251 _safepoint_reasons[index]); 1252 } 1253 } 1254 1255 tty->print_cr(UINT64_FORMAT_W(5) " VM operations coalesced during safepoint", 1256 _coalesced_vmop_count); 1257 tty->print_cr("Maximum sync time " INT64_FORMAT_W(5) " ms", 1258 _max_sync_time / MICROUNITS); 1259 tty->print_cr("Maximum vm operation time (except for Exit VM operation) " 1260 INT64_FORMAT_W(5) " ms", 1261 _max_vmop_time / MICROUNITS); 1262} 1263 1264// ------------------------------------------------------------------------------------------------ 1265// Non-product code 1266 1267#ifndef PRODUCT 1268 1269void SafepointSynchronize::print_state() { 1270 if (_state == _not_synchronized) { 1271 tty->print_cr("not synchronized"); 1272 } else if (_state == _synchronizing || _state == _synchronized) { 1273 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" : 1274 "synchronized"); 1275 1276 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) { 1277 cur->safepoint_state()->print(); 1278 } 1279 } 1280} 1281 1282void SafepointSynchronize::safepoint_msg(const char* format, ...) { 1283 if (ShowSafepointMsgs) { 1284 va_list ap; 1285 va_start(ap, format); 1286 tty->vprint_cr(format, ap); 1287 va_end(ap); 1288 } 1289} 1290 1291#endif // !PRODUCT 1292