safepoint.cpp revision 2721:f08d439fab8c
1/* 2 * Copyright (c) 1997, 2011, 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/systemDictionary.hpp" 27#include "code/codeCache.hpp" 28#include "code/icBuffer.hpp" 29#include "code/nmethod.hpp" 30#include "code/pcDesc.hpp" 31#include "code/scopeDesc.hpp" 32#include "gc_interface/collectedHeap.hpp" 33#include "interpreter/interpreter.hpp" 34#include "memory/resourceArea.hpp" 35#include "memory/universe.inline.hpp" 36#include "oops/oop.inline.hpp" 37#include "oops/symbol.hpp" 38#include "runtime/compilationPolicy.hpp" 39#include "runtime/deoptimization.hpp" 40#include "runtime/frame.inline.hpp" 41#include "runtime/interfaceSupport.hpp" 42#include "runtime/mutexLocker.hpp" 43#include "runtime/osThread.hpp" 44#include "runtime/safepoint.hpp" 45#include "runtime/signature.hpp" 46#include "runtime/stubCodeGenerator.hpp" 47#include "runtime/stubRoutines.hpp" 48#include "runtime/sweeper.hpp" 49#include "runtime/synchronizer.hpp" 50#include "services/runtimeService.hpp" 51#include "utilities/events.hpp" 52#ifdef TARGET_ARCH_x86 53# include "nativeInst_x86.hpp" 54# include "vmreg_x86.inline.hpp" 55#endif 56#ifdef TARGET_ARCH_sparc 57# include "nativeInst_sparc.hpp" 58# include "vmreg_sparc.inline.hpp" 59#endif 60#ifdef TARGET_ARCH_zero 61# include "nativeInst_zero.hpp" 62# include "vmreg_zero.inline.hpp" 63#endif 64#ifdef TARGET_ARCH_arm 65# include "nativeInst_arm.hpp" 66# include "vmreg_arm.inline.hpp" 67#endif 68#ifdef TARGET_ARCH_ppc 69# include "nativeInst_ppc.hpp" 70# include "vmreg_ppc.inline.hpp" 71#endif 72#ifdef TARGET_OS_FAMILY_linux 73# include "thread_linux.inline.hpp" 74#endif 75#ifdef TARGET_OS_FAMILY_solaris 76# include "thread_solaris.inline.hpp" 77#endif 78#ifdef TARGET_OS_FAMILY_windows 79# include "thread_windows.inline.hpp" 80#endif 81#ifdef TARGET_OS_FAMILY_bsd 82# include "thread_bsd.inline.hpp" 83#endif 84#ifndef SERIALGC 85#include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp" 86#include "gc_implementation/shared/concurrentGCThread.hpp" 87#endif 88#ifdef COMPILER1 89#include "c1/c1_globals.hpp" 90#endif 91 92// -------------------------------------------------------------------------------------------------- 93// Implementation of Safepoint begin/end 94 95SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized; 96volatile int SafepointSynchronize::_waiting_to_block = 0; 97volatile int SafepointSynchronize::_safepoint_counter = 0; 98long SafepointSynchronize::_end_of_last_safepoint = 0; 99static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE 100static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only 101static bool timeout_error_printed = false; 102 103// Roll all threads forward to a safepoint and suspend them all 104void SafepointSynchronize::begin() { 105 106 Thread* myThread = Thread::current(); 107 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint"); 108 109 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) { 110 _safepoint_begin_time = os::javaTimeNanos(); 111 _ts_of_current_safepoint = tty->time_stamp().seconds(); 112 } 113 114#ifndef SERIALGC 115 if (UseConcMarkSweepGC) { 116 // In the future we should investigate whether CMS can use the 117 // more-general mechanism below. DLD (01/05). 118 ConcurrentMarkSweepThread::synchronize(false); 119 } else if (UseG1GC) { 120 ConcurrentGCThread::safepoint_synchronize(); 121 } 122#endif // SERIALGC 123 124 // By getting the Threads_lock, we assure that no threads are about to start or 125 // exit. It is released again in SafepointSynchronize::end(). 126 Threads_lock->lock(); 127 128 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state"); 129 130 int nof_threads = Threads::number_of_threads(); 131 132 if (TraceSafepoint) { 133 tty->print_cr("Safepoint synchronization initiated. (%d)", nof_threads); 134 } 135 136 RuntimeService::record_safepoint_begin(); 137 138 { 139 MutexLocker mu(Safepoint_lock); 140 141 // Set number of threads to wait for, before we initiate the callbacks 142 _waiting_to_block = nof_threads; 143 TryingToBlock = 0 ; 144 int still_running = nof_threads; 145 146 // Save the starting time, so that it can be compared to see if this has taken 147 // too long to complete. 148 jlong safepoint_limit_time; 149 timeout_error_printed = false; 150 151 // PrintSafepointStatisticsTimeout can be specified separately. When 152 // specified, PrintSafepointStatistics will be set to true in 153 // deferred_initialize_stat method. The initialization has to be done 154 // early enough to avoid any races. See bug 6880029 for details. 155 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) { 156 deferred_initialize_stat(); 157 } 158 159 // Begin the process of bringing the system to a safepoint. 160 // Java threads can be in several different states and are 161 // stopped by different mechanisms: 162 // 163 // 1. Running interpreted 164 // The interpeter dispatch table is changed to force it to 165 // check for a safepoint condition between bytecodes. 166 // 2. Running in native code 167 // When returning from the native code, a Java thread must check 168 // the safepoint _state to see if we must block. If the 169 // VM thread sees a Java thread in native, it does 170 // not wait for this thread to block. The order of the memory 171 // writes and reads of both the safepoint state and the Java 172 // threads state is critical. In order to guarantee that the 173 // memory writes are serialized with respect to each other, 174 // the VM thread issues a memory barrier instruction 175 // (on MP systems). In order to avoid the overhead of issuing 176 // a memory barrier for each Java thread making native calls, each Java 177 // thread performs a write to a single memory page after changing 178 // the thread state. The VM thread performs a sequence of 179 // mprotect OS calls which forces all previous writes from all 180 // Java threads to be serialized. This is done in the 181 // os::serialize_thread_states() call. This has proven to be 182 // much more efficient than executing a membar instruction 183 // on every call to native code. 184 // 3. Running compiled Code 185 // Compiled code reads a global (Safepoint Polling) page that 186 // is set to fault if we are trying to get to a safepoint. 187 // 4. Blocked 188 // A thread which is blocked will not be allowed to return from the 189 // block condition until the safepoint operation is complete. 190 // 5. In VM or Transitioning between states 191 // If a Java thread is currently running in the VM or transitioning 192 // between states, the safepointing code will wait for the thread to 193 // block itself when it attempts transitions to a new state. 194 // 195 _state = _synchronizing; 196 OrderAccess::fence(); 197 198 // Flush all thread states to memory 199 if (!UseMembar) { 200 os::serialize_thread_states(); 201 } 202 203 // Make interpreter safepoint aware 204 Interpreter::notice_safepoints(); 205 206 if (UseCompilerSafepoints && DeferPollingPageLoopCount < 0) { 207 // Make polling safepoint aware 208 guarantee (PageArmed == 0, "invariant") ; 209 PageArmed = 1 ; 210 os::make_polling_page_unreadable(); 211 } 212 213 // Consider using active_processor_count() ... but that call is expensive. 214 int ncpus = os::processor_count() ; 215 216#ifdef ASSERT 217 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) { 218 assert(cur->safepoint_state()->is_running(), "Illegal initial state"); 219 } 220#endif // ASSERT 221 222 if (SafepointTimeout) 223 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS; 224 225 // Iterate through all threads until it have been determined how to stop them all at a safepoint 226 unsigned int iterations = 0; 227 int steps = 0 ; 228 while(still_running > 0) { 229 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) { 230 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended"); 231 ThreadSafepointState *cur_state = cur->safepoint_state(); 232 if (cur_state->is_running()) { 233 cur_state->examine_state_of_thread(); 234 if (!cur_state->is_running()) { 235 still_running--; 236 // consider adjusting steps downward: 237 // steps = 0 238 // steps -= NNN 239 // steps >>= 1 240 // steps = MIN(steps, 2000-100) 241 // if (iterations != 0) steps -= NNN 242 } 243 if (TraceSafepoint && Verbose) cur_state->print(); 244 } 245 } 246 247 if (PrintSafepointStatistics && iterations == 0) { 248 begin_statistics(nof_threads, still_running); 249 } 250 251 if (still_running > 0) { 252 // Check for if it takes to long 253 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) { 254 print_safepoint_timeout(_spinning_timeout); 255 } 256 257 // Spin to avoid context switching. 258 // There's a tension between allowing the mutators to run (and rendezvous) 259 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that 260 // a mutator might otherwise use profitably to reach a safepoint. Excessive 261 // spinning by the VM thread on a saturated system can increase rendezvous latency. 262 // Blocking or yielding incur their own penalties in the form of context switching 263 // and the resultant loss of $ residency. 264 // 265 // Further complicating matters is that yield() does not work as naively expected 266 // on many platforms -- yield() does not guarantee that any other ready threads 267 // will run. As such we revert yield_all() after some number of iterations. 268 // Yield_all() is implemented as a short unconditional sleep on some platforms. 269 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping 270 // can actually increase the time it takes the VM thread to detect that a system-wide 271 // stop-the-world safepoint has been reached. In a pathological scenario such as that 272 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe. 273 // In that case the mutators will be stalled waiting for the safepoint to complete and the 274 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread 275 // will eventually wake up and detect that all mutators are safe, at which point 276 // we'll again make progress. 277 // 278 // Beware too that that the VMThread typically runs at elevated priority. 279 // Its default priority is higher than the default mutator priority. 280 // Obviously, this complicates spinning. 281 // 282 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0). 283 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will. 284 // 285 // See the comments in synchronizer.cpp for additional remarks on spinning. 286 // 287 // In the future we might: 288 // 1. Modify the safepoint scheme to avoid potentally unbounded spinning. 289 // This is tricky as the path used by a thread exiting the JVM (say on 290 // on JNI call-out) simply stores into its state field. The burden 291 // is placed on the VM thread, which must poll (spin). 292 // 2. Find something useful to do while spinning. If the safepoint is GC-related 293 // we might aggressively scan the stacks of threads that are already safe. 294 // 3. Use Solaris schedctl to examine the state of the still-running mutators. 295 // If all the mutators are ONPROC there's no reason to sleep or yield. 296 // 4. YieldTo() any still-running mutators that are ready but OFFPROC. 297 // 5. Check system saturation. If the system is not fully saturated then 298 // simply spin and avoid sleep/yield. 299 // 6. As still-running mutators rendezvous they could unpark the sleeping 300 // VMthread. This works well for still-running mutators that become 301 // safe. The VMthread must still poll for mutators that call-out. 302 // 7. Drive the policy on time-since-begin instead of iterations. 303 // 8. Consider making the spin duration a function of the # of CPUs: 304 // Spin = (((ncpus-1) * M) + K) + F(still_running) 305 // Alternately, instead of counting iterations of the outer loop 306 // we could count the # of threads visited in the inner loop, above. 307 // 9. On windows consider using the return value from SwitchThreadTo() 308 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions. 309 310 if (UseCompilerSafepoints && int(iterations) == DeferPollingPageLoopCount) { 311 guarantee (PageArmed == 0, "invariant") ; 312 PageArmed = 1 ; 313 os::make_polling_page_unreadable(); 314 } 315 316 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or 317 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus) 318 ++steps ; 319 if (ncpus > 1 && steps < SafepointSpinBeforeYield) { 320 SpinPause() ; // MP-Polite spin 321 } else 322 if (steps < DeferThrSuspendLoopCount) { 323 os::NakedYield() ; 324 } else { 325 os::yield_all(steps) ; 326 // Alternately, the VM thread could transiently depress its scheduling priority or 327 // transiently increase the priority of the tardy mutator(s). 328 } 329 330 iterations ++ ; 331 } 332 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long"); 333 } 334 assert(still_running == 0, "sanity check"); 335 336 if (PrintSafepointStatistics) { 337 update_statistics_on_spin_end(); 338 } 339 340 // wait until all threads are stopped 341 while (_waiting_to_block > 0) { 342 if (TraceSafepoint) tty->print_cr("Waiting for %d thread(s) to block", _waiting_to_block); 343 if (!SafepointTimeout || timeout_error_printed) { 344 Safepoint_lock->wait(true); // true, means with no safepoint checks 345 } else { 346 // Compute remaining time 347 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos(); 348 349 // If there is no remaining time, then there is an error 350 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) { 351 print_safepoint_timeout(_blocking_timeout); 352 } 353 } 354 } 355 assert(_waiting_to_block == 0, "sanity check"); 356 357#ifndef PRODUCT 358 if (SafepointTimeout) { 359 jlong current_time = os::javaTimeNanos(); 360 if (safepoint_limit_time < current_time) { 361 tty->print_cr("# SafepointSynchronize: Finished after " 362 INT64_FORMAT_W(6) " ms", 363 ((current_time - safepoint_limit_time) / MICROUNITS + 364 SafepointTimeoutDelay)); 365 } 366 } 367#endif 368 369 assert((_safepoint_counter & 0x1) == 0, "must be even"); 370 assert(Threads_lock->owned_by_self(), "must hold Threads_lock"); 371 _safepoint_counter ++; 372 373 // Record state 374 _state = _synchronized; 375 376 OrderAccess::fence(); 377 378 if (TraceSafepoint) { 379 VM_Operation *op = VMThread::vm_operation(); 380 tty->print_cr("Entering safepoint region: %s", (op != NULL) ? op->name() : "no vm operation"); 381 } 382 383 RuntimeService::record_safepoint_synchronized(); 384 if (PrintSafepointStatistics) { 385 update_statistics_on_sync_end(os::javaTimeNanos()); 386 } 387 388 // Call stuff that needs to be run when a safepoint is just about to be completed 389 do_cleanup_tasks(); 390 391 if (PrintSafepointStatistics) { 392 // Record how much time spend on the above cleanup tasks 393 update_statistics_on_cleanup_end(os::javaTimeNanos()); 394 } 395 } 396} 397 398// Wake up all threads, so they are ready to resume execution after the safepoint 399// operation has been carried out 400void SafepointSynchronize::end() { 401 402 assert(Threads_lock->owned_by_self(), "must hold Threads_lock"); 403 assert((_safepoint_counter & 0x1) == 1, "must be odd"); 404 _safepoint_counter ++; 405 // memory fence isn't required here since an odd _safepoint_counter 406 // value can do no harm and a fence is issued below anyway. 407 408 DEBUG_ONLY(Thread* myThread = Thread::current();) 409 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint"); 410 411 if (PrintSafepointStatistics) { 412 end_statistics(os::javaTimeNanos()); 413 } 414 415#ifdef ASSERT 416 // A pending_exception cannot be installed during a safepoint. The threads 417 // may install an async exception after they come back from a safepoint into 418 // pending_exception after they unblock. But that should happen later. 419 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) { 420 assert (!(cur->has_pending_exception() && 421 cur->safepoint_state()->is_at_poll_safepoint()), 422 "safepoint installed a pending exception"); 423 } 424#endif // ASSERT 425 426 if (PageArmed) { 427 // Make polling safepoint aware 428 os::make_polling_page_readable(); 429 PageArmed = 0 ; 430 } 431 432 // Remove safepoint check from interpreter 433 Interpreter::ignore_safepoints(); 434 435 { 436 MutexLocker mu(Safepoint_lock); 437 438 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization"); 439 440 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method 441 // when they get restarted. 442 _state = _not_synchronized; 443 OrderAccess::fence(); 444 445 if (TraceSafepoint) { 446 tty->print_cr("Leaving safepoint region"); 447 } 448 449 // Start suspended threads 450 for(JavaThread *current = Threads::first(); current; current = current->next()) { 451 // A problem occurring on Solaris is when attempting to restart threads 452 // the first #cpus - 1 go well, but then the VMThread is preempted when we get 453 // to the next one (since it has been running the longest). We then have 454 // to wait for a cpu to become available before we can continue restarting 455 // threads. 456 // FIXME: This causes the performance of the VM to degrade when active and with 457 // large numbers of threads. Apparently this is due to the synchronous nature 458 // of suspending threads. 459 // 460 // TODO-FIXME: the comments above are vestigial and no longer apply. 461 // Furthermore, using solaris' schedctl in this particular context confers no benefit 462 if (VMThreadHintNoPreempt) { 463 os::hint_no_preempt(); 464 } 465 ThreadSafepointState* cur_state = current->safepoint_state(); 466 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint"); 467 cur_state->restart(); 468 assert(cur_state->is_running(), "safepoint state has not been reset"); 469 } 470 471 RuntimeService::record_safepoint_end(); 472 473 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads 474 // blocked in signal_thread_blocked 475 Threads_lock->unlock(); 476 477 } 478#ifndef SERIALGC 479 // If there are any concurrent GC threads resume them. 480 if (UseConcMarkSweepGC) { 481 ConcurrentMarkSweepThread::desynchronize(false); 482 } else if (UseG1GC) { 483 ConcurrentGCThread::safepoint_desynchronize(); 484 } 485#endif // SERIALGC 486 // record this time so VMThread can keep track how much time has elasped 487 // since last safepoint. 488 _end_of_last_safepoint = os::javaTimeMillis(); 489} 490 491bool SafepointSynchronize::is_cleanup_needed() { 492 // Need a safepoint if some inline cache buffers is non-empty 493 if (!InlineCacheBuffer::is_empty()) return true; 494 return false; 495} 496 497 498 499// Various cleaning tasks that should be done periodically at safepoints 500void SafepointSynchronize::do_cleanup_tasks() { 501 { 502 TraceTime t1("deflating idle monitors", TraceSafepointCleanupTime); 503 ObjectSynchronizer::deflate_idle_monitors(); 504 } 505 506 { 507 TraceTime t2("updating inline caches", TraceSafepointCleanupTime); 508 InlineCacheBuffer::update_inline_caches(); 509 } 510 { 511 TraceTime t3("compilation policy safepoint handler", TraceSafepointCleanupTime); 512 CompilationPolicy::policy()->do_safepoint_work(); 513 } 514 515 TraceTime t4("sweeping nmethods", TraceSafepointCleanupTime); 516 NMethodSweeper::scan_stacks(); 517 518 // rotate log files? 519 if (UseGCLogFileRotation) { 520 gclog_or_tty->rotate_log(); 521 } 522} 523 524 525bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) { 526 switch(state) { 527 case _thread_in_native: 528 // native threads are safe if they have no java stack or have walkable stack 529 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable(); 530 531 // blocked threads should have already have walkable stack 532 case _thread_blocked: 533 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable"); 534 return true; 535 536 default: 537 return false; 538 } 539} 540 541 542// ------------------------------------------------------------------------------------------------------- 543// Implementation of Safepoint callback point 544 545void SafepointSynchronize::block(JavaThread *thread) { 546 assert(thread != NULL, "thread must be set"); 547 assert(thread->is_Java_thread(), "not a Java thread"); 548 549 // Threads shouldn't block if they are in the middle of printing, but... 550 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id()); 551 552 // Only bail from the block() call if the thread is gone from the 553 // thread list; starting to exit should still block. 554 if (thread->is_terminated()) { 555 // block current thread if we come here from native code when VM is gone 556 thread->block_if_vm_exited(); 557 558 // otherwise do nothing 559 return; 560 } 561 562 JavaThreadState state = thread->thread_state(); 563 thread->frame_anchor()->make_walkable(thread); 564 565 // Check that we have a valid thread_state at this point 566 switch(state) { 567 case _thread_in_vm_trans: 568 case _thread_in_Java: // From compiled code 569 570 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case, 571 // we pretend we are still in the VM. 572 thread->set_thread_state(_thread_in_vm); 573 574 if (is_synchronizing()) { 575 Atomic::inc (&TryingToBlock) ; 576 } 577 578 // We will always be holding the Safepoint_lock when we are examine the state 579 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and 580 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code 581 Safepoint_lock->lock_without_safepoint_check(); 582 if (is_synchronizing()) { 583 // Decrement the number of threads to wait for and signal vm thread 584 assert(_waiting_to_block > 0, "sanity check"); 585 _waiting_to_block--; 586 thread->safepoint_state()->set_has_called_back(true); 587 588 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread 589 if (_waiting_to_block == 0) { 590 Safepoint_lock->notify_all(); 591 } 592 } 593 594 // We transition the thread to state _thread_blocked here, but 595 // we can't do our usual check for external suspension and then 596 // self-suspend after the lock_without_safepoint_check() call 597 // below because we are often called during transitions while 598 // we hold different locks. That would leave us suspended while 599 // holding a resource which results in deadlocks. 600 thread->set_thread_state(_thread_blocked); 601 Safepoint_lock->unlock(); 602 603 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during 604 // the entire safepoint, the threads will all line up here during the safepoint. 605 Threads_lock->lock_without_safepoint_check(); 606 // restore original state. This is important if the thread comes from compiled code, so it 607 // will continue to execute with the _thread_in_Java state. 608 thread->set_thread_state(state); 609 Threads_lock->unlock(); 610 break; 611 612 case _thread_in_native_trans: 613 case _thread_blocked_trans: 614 case _thread_new_trans: 615 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) { 616 thread->print_thread_state(); 617 fatal("Deadlock in safepoint code. " 618 "Should have called back to the VM before blocking."); 619 } 620 621 // We transition the thread to state _thread_blocked here, but 622 // we can't do our usual check for external suspension and then 623 // self-suspend after the lock_without_safepoint_check() call 624 // below because we are often called during transitions while 625 // we hold different locks. That would leave us suspended while 626 // holding a resource which results in deadlocks. 627 thread->set_thread_state(_thread_blocked); 628 629 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence, 630 // the safepoint code might still be waiting for it to block. We need to change the state here, 631 // so it can see that it is at a safepoint. 632 633 // Block until the safepoint operation is completed. 634 Threads_lock->lock_without_safepoint_check(); 635 636 // Restore state 637 thread->set_thread_state(state); 638 639 Threads_lock->unlock(); 640 break; 641 642 default: 643 fatal(err_msg("Illegal threadstate encountered: %d", state)); 644 } 645 646 // Check for pending. async. exceptions or suspends - except if the 647 // thread was blocked inside the VM. has_special_runtime_exit_condition() 648 // is called last since it grabs a lock and we only want to do that when 649 // we must. 650 // 651 // Note: we never deliver an async exception at a polling point as the 652 // compiler may not have an exception handler for it. The polling 653 // code will notice the async and deoptimize and the exception will 654 // be delivered. (Polling at a return point is ok though). Sure is 655 // a lot of bother for a deprecated feature... 656 // 657 // We don't deliver an async exception if the thread state is 658 // _thread_in_native_trans so JNI functions won't be called with 659 // a surprising pending exception. If the thread state is going back to java, 660 // async exception is checked in check_special_condition_for_native_trans(). 661 662 if (state != _thread_blocked_trans && 663 state != _thread_in_vm_trans && 664 thread->has_special_runtime_exit_condition()) { 665 thread->handle_special_runtime_exit_condition( 666 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans)); 667 } 668} 669 670// ------------------------------------------------------------------------------------------------------ 671// Exception handlers 672 673#ifndef PRODUCT 674#ifdef _LP64 675#define PTR_PAD "" 676#else 677#define PTR_PAD " " 678#endif 679 680static void print_ptrs(intptr_t oldptr, intptr_t newptr, bool wasoop) { 681 bool is_oop = newptr ? ((oop)newptr)->is_oop() : false; 682 tty->print_cr(PTR_FORMAT PTR_PAD " %s %c " PTR_FORMAT PTR_PAD " %s %s", 683 oldptr, wasoop?"oop":" ", oldptr == newptr ? ' ' : '!', 684 newptr, is_oop?"oop":" ", (wasoop && !is_oop) ? "STALE" : ((wasoop==false&&is_oop==false&&oldptr !=newptr)?"STOMP":" ")); 685} 686 687static void print_longs(jlong oldptr, jlong newptr, bool wasoop) { 688 bool is_oop = newptr ? ((oop)(intptr_t)newptr)->is_oop() : false; 689 tty->print_cr(PTR64_FORMAT " %s %c " PTR64_FORMAT " %s %s", 690 oldptr, wasoop?"oop":" ", oldptr == newptr ? ' ' : '!', 691 newptr, is_oop?"oop":" ", (wasoop && !is_oop) ? "STALE" : ((wasoop==false&&is_oop==false&&oldptr !=newptr)?"STOMP":" ")); 692} 693 694#ifdef SPARC 695static void print_me(intptr_t *new_sp, intptr_t *old_sp, bool *was_oops) { 696#ifdef _LP64 697 tty->print_cr("--------+------address-----+------before-----------+-------after----------+"); 698 const int incr = 1; // Increment to skip a long, in units of intptr_t 699#else 700 tty->print_cr("--------+--address-+------before-----------+-------after----------+"); 701 const int incr = 2; // Increment to skip a long, in units of intptr_t 702#endif 703 tty->print_cr("---SP---|"); 704 for( int i=0; i<16; i++ ) { 705 tty->print("blob %c%d |"PTR_FORMAT" ","LO"[i>>3],i&7,new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); } 706 tty->print_cr("--------|"); 707 for( int i1=0; i1<frame::memory_parameter_word_sp_offset-16; i1++ ) { 708 tty->print("argv pad|"PTR_FORMAT" ",new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); } 709 tty->print(" pad|"PTR_FORMAT" ",new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); 710 tty->print_cr("--------|"); 711 tty->print(" G1 |"PTR_FORMAT" ",new_sp); print_longs(*(jlong*)old_sp,*(jlong*)new_sp,was_oops[incr-1]); old_sp += incr; new_sp += incr; was_oops += incr; 712 tty->print(" G3 |"PTR_FORMAT" ",new_sp); print_longs(*(jlong*)old_sp,*(jlong*)new_sp,was_oops[incr-1]); old_sp += incr; new_sp += incr; was_oops += incr; 713 tty->print(" G4 |"PTR_FORMAT" ",new_sp); print_longs(*(jlong*)old_sp,*(jlong*)new_sp,was_oops[incr-1]); old_sp += incr; new_sp += incr; was_oops += incr; 714 tty->print(" G5 |"PTR_FORMAT" ",new_sp); print_longs(*(jlong*)old_sp,*(jlong*)new_sp,was_oops[incr-1]); old_sp += incr; new_sp += incr; was_oops += incr; 715 tty->print_cr(" FSR |"PTR_FORMAT" "PTR64_FORMAT" "PTR64_FORMAT,new_sp,*(jlong*)old_sp,*(jlong*)new_sp); 716 old_sp += incr; new_sp += incr; was_oops += incr; 717 // Skip the floats 718 tty->print_cr("--Float-|"PTR_FORMAT,new_sp); 719 tty->print_cr("---FP---|"); 720 old_sp += incr*32; new_sp += incr*32; was_oops += incr*32; 721 for( int i2=0; i2<16; i2++ ) { 722 tty->print("call %c%d |"PTR_FORMAT" ","LI"[i2>>3],i2&7,new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); } 723 tty->print_cr(""); 724} 725#endif // SPARC 726#endif // PRODUCT 727 728 729void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) { 730 assert(thread->is_Java_thread(), "polling reference encountered by VM thread"); 731 assert(thread->thread_state() == _thread_in_Java, "should come from Java code"); 732 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization"); 733 734 // Uncomment this to get some serious before/after printing of the 735 // Sparc safepoint-blob frame structure. 736 /* 737 intptr_t* sp = thread->last_Java_sp(); 738 intptr_t stack_copy[150]; 739 for( int i=0; i<150; i++ ) stack_copy[i] = sp[i]; 740 bool was_oops[150]; 741 for( int i=0; i<150; i++ ) 742 was_oops[i] = stack_copy[i] ? ((oop)stack_copy[i])->is_oop() : false; 743 */ 744 745 if (ShowSafepointMsgs) { 746 tty->print("handle_polling_page_exception: "); 747 } 748 749 if (PrintSafepointStatistics) { 750 inc_page_trap_count(); 751 } 752 753 ThreadSafepointState* state = thread->safepoint_state(); 754 755 state->handle_polling_page_exception(); 756 // print_me(sp,stack_copy,was_oops); 757} 758 759 760void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) { 761 if (!timeout_error_printed) { 762 timeout_error_printed = true; 763 // Print out the thread infor which didn't reach the safepoint for debugging 764 // purposes (useful when there are lots of threads in the debugger). 765 tty->print_cr(""); 766 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:"); 767 if (reason == _spinning_timeout) { 768 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint."); 769 } else if (reason == _blocking_timeout) { 770 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop."); 771 } 772 773 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:"); 774 ThreadSafepointState *cur_state; 775 ResourceMark rm; 776 for(JavaThread *cur_thread = Threads::first(); cur_thread; 777 cur_thread = cur_thread->next()) { 778 cur_state = cur_thread->safepoint_state(); 779 780 if (cur_thread->thread_state() != _thread_blocked && 781 ((reason == _spinning_timeout && cur_state->is_running()) || 782 (reason == _blocking_timeout && !cur_state->has_called_back()))) { 783 tty->print("# "); 784 cur_thread->print(); 785 tty->print_cr(""); 786 } 787 } 788 tty->print_cr("# SafepointSynchronize::begin: (End of list)"); 789 } 790 791 // To debug the long safepoint, specify both DieOnSafepointTimeout & 792 // ShowMessageBoxOnError. 793 if (DieOnSafepointTimeout) { 794 char msg[1024]; 795 VM_Operation *op = VMThread::vm_operation(); 796 sprintf(msg, "Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.", 797 SafepointTimeoutDelay, 798 op != NULL ? op->name() : "no vm operation"); 799 fatal(msg); 800 } 801} 802 803 804// ------------------------------------------------------------------------------------------------------- 805// Implementation of ThreadSafepointState 806 807ThreadSafepointState::ThreadSafepointState(JavaThread *thread) { 808 _thread = thread; 809 _type = _running; 810 _has_called_back = false; 811 _at_poll_safepoint = false; 812} 813 814void ThreadSafepointState::create(JavaThread *thread) { 815 ThreadSafepointState *state = new ThreadSafepointState(thread); 816 thread->set_safepoint_state(state); 817} 818 819void ThreadSafepointState::destroy(JavaThread *thread) { 820 if (thread->safepoint_state()) { 821 delete(thread->safepoint_state()); 822 thread->set_safepoint_state(NULL); 823 } 824} 825 826void ThreadSafepointState::examine_state_of_thread() { 827 assert(is_running(), "better be running or just have hit safepoint poll"); 828 829 JavaThreadState state = _thread->thread_state(); 830 831 // Save the state at the start of safepoint processing. 832 _orig_thread_state = state; 833 834 // Check for a thread that is suspended. Note that thread resume tries 835 // to grab the Threads_lock which we own here, so a thread cannot be 836 // resumed during safepoint synchronization. 837 838 // We check to see if this thread is suspended without locking to 839 // avoid deadlocking with a third thread that is waiting for this 840 // thread to be suspended. The third thread can notice the safepoint 841 // that we're trying to start at the beginning of its SR_lock->wait() 842 // call. If that happens, then the third thread will block on the 843 // safepoint while still holding the underlying SR_lock. We won't be 844 // able to get the SR_lock and we'll deadlock. 845 // 846 // We don't need to grab the SR_lock here for two reasons: 847 // 1) The suspend flags are both volatile and are set with an 848 // Atomic::cmpxchg() call so we should see the suspended 849 // state right away. 850 // 2) We're being called from the safepoint polling loop; if 851 // we don't see the suspended state on this iteration, then 852 // we'll come around again. 853 // 854 bool is_suspended = _thread->is_ext_suspended(); 855 if (is_suspended) { 856 roll_forward(_at_safepoint); 857 return; 858 } 859 860 // Some JavaThread states have an initial safepoint state of 861 // running, but are actually at a safepoint. We will happily 862 // agree and update the safepoint state here. 863 if (SafepointSynchronize::safepoint_safe(_thread, state)) { 864 roll_forward(_at_safepoint); 865 return; 866 } 867 868 if (state == _thread_in_vm) { 869 roll_forward(_call_back); 870 return; 871 } 872 873 // All other thread states will continue to run until they 874 // transition and self-block in state _blocked 875 // Safepoint polling in compiled code causes the Java threads to do the same. 876 // Note: new threads may require a malloc so they must be allowed to finish 877 878 assert(is_running(), "examine_state_of_thread on non-running thread"); 879 return; 880} 881 882// Returns true is thread could not be rolled forward at present position. 883void ThreadSafepointState::roll_forward(suspend_type type) { 884 _type = type; 885 886 switch(_type) { 887 case _at_safepoint: 888 SafepointSynchronize::signal_thread_at_safepoint(); 889 break; 890 891 case _call_back: 892 set_has_called_back(false); 893 break; 894 895 case _running: 896 default: 897 ShouldNotReachHere(); 898 } 899} 900 901void ThreadSafepointState::restart() { 902 switch(type()) { 903 case _at_safepoint: 904 case _call_back: 905 break; 906 907 case _running: 908 default: 909 tty->print_cr("restart thread "INTPTR_FORMAT" with state %d", 910 _thread, _type); 911 _thread->print(); 912 ShouldNotReachHere(); 913 } 914 _type = _running; 915 set_has_called_back(false); 916} 917 918 919void ThreadSafepointState::print_on(outputStream *st) const { 920 const char *s; 921 922 switch(_type) { 923 case _running : s = "_running"; break; 924 case _at_safepoint : s = "_at_safepoint"; break; 925 case _call_back : s = "_call_back"; break; 926 default: 927 ShouldNotReachHere(); 928 } 929 930 st->print_cr("Thread: " INTPTR_FORMAT 931 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d", 932 _thread, _thread->osthread()->thread_id(), s, _has_called_back, 933 _at_poll_safepoint); 934 935 _thread->print_thread_state_on(st); 936} 937 938 939// --------------------------------------------------------------------------------------------------------------------- 940 941// Block the thread at the safepoint poll or poll return. 942void ThreadSafepointState::handle_polling_page_exception() { 943 944 // Check state. block() will set thread state to thread_in_vm which will 945 // cause the safepoint state _type to become _call_back. 946 assert(type() == ThreadSafepointState::_running, 947 "polling page exception on thread not running state"); 948 949 // Step 1: Find the nmethod from the return address 950 if (ShowSafepointMsgs && Verbose) { 951 tty->print_cr("Polling page exception at " INTPTR_FORMAT, thread()->saved_exception_pc()); 952 } 953 address real_return_addr = thread()->saved_exception_pc(); 954 955 CodeBlob *cb = CodeCache::find_blob(real_return_addr); 956 assert(cb != NULL && cb->is_nmethod(), "return address should be in nmethod"); 957 nmethod* nm = (nmethod*)cb; 958 959 // Find frame of caller 960 frame stub_fr = thread()->last_frame(); 961 CodeBlob* stub_cb = stub_fr.cb(); 962 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub"); 963 RegisterMap map(thread(), true); 964 frame caller_fr = stub_fr.sender(&map); 965 966 // Should only be poll_return or poll 967 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" ); 968 969 // This is a poll immediately before a return. The exception handling code 970 // has already had the effect of causing the return to occur, so the execution 971 // will continue immediately after the call. In addition, the oopmap at the 972 // return point does not mark the return value as an oop (if it is), so 973 // it needs a handle here to be updated. 974 if( nm->is_at_poll_return(real_return_addr) ) { 975 // See if return type is an oop. 976 bool return_oop = nm->method()->is_returning_oop(); 977 Handle return_value; 978 if (return_oop) { 979 // The oop result has been saved on the stack together with all 980 // the other registers. In order to preserve it over GCs we need 981 // to keep it in a handle. 982 oop result = caller_fr.saved_oop_result(&map); 983 assert(result == NULL || result->is_oop(), "must be oop"); 984 return_value = Handle(thread(), result); 985 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer"); 986 } 987 988 // Block the thread 989 SafepointSynchronize::block(thread()); 990 991 // restore oop result, if any 992 if (return_oop) { 993 caller_fr.set_saved_oop_result(&map, return_value()); 994 } 995 } 996 997 // This is a safepoint poll. Verify the return address and block. 998 else { 999 set_at_poll_safepoint(true); 1000 1001 // verify the blob built the "return address" correctly 1002 assert(real_return_addr == caller_fr.pc(), "must match"); 1003 1004 // Block the thread 1005 SafepointSynchronize::block(thread()); 1006 set_at_poll_safepoint(false); 1007 1008 // If we have a pending async exception deoptimize the frame 1009 // as otherwise we may never deliver it. 1010 if (thread()->has_async_condition()) { 1011 ThreadInVMfromJavaNoAsyncException __tiv(thread()); 1012 Deoptimization::deoptimize_frame(thread(), caller_fr.id()); 1013 } 1014 1015 // If an exception has been installed we must check for a pending deoptimization 1016 // Deoptimize frame if exception has been thrown. 1017 1018 if (thread()->has_pending_exception() ) { 1019 RegisterMap map(thread(), true); 1020 frame caller_fr = stub_fr.sender(&map); 1021 if (caller_fr.is_deoptimized_frame()) { 1022 // The exception patch will destroy registers that are still 1023 // live and will be needed during deoptimization. Defer the 1024 // Async exception should have defered the exception until the 1025 // next safepoint which will be detected when we get into 1026 // the interpreter so if we have an exception now things 1027 // are messed up. 1028 1029 fatal("Exception installed and deoptimization is pending"); 1030 } 1031 } 1032 } 1033} 1034 1035 1036// 1037// Statistics & Instrumentations 1038// 1039SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL; 1040jlong SafepointSynchronize::_safepoint_begin_time = 0; 1041int SafepointSynchronize::_cur_stat_index = 0; 1042julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating]; 1043julong SafepointSynchronize::_coalesced_vmop_count = 0; 1044jlong SafepointSynchronize::_max_sync_time = 0; 1045jlong SafepointSynchronize::_max_vmop_time = 0; 1046float SafepointSynchronize::_ts_of_current_safepoint = 0.0f; 1047 1048static jlong cleanup_end_time = 0; 1049static bool need_to_track_page_armed_status = false; 1050static bool init_done = false; 1051 1052// Helper method to print the header. 1053static void print_header() { 1054 tty->print(" vmop " 1055 "[threads: total initially_running wait_to_block] "); 1056 tty->print("[time: spin block sync cleanup vmop] "); 1057 1058 // no page armed status printed out if it is always armed. 1059 if (need_to_track_page_armed_status) { 1060 tty->print("page_armed "); 1061 } 1062 1063 tty->print_cr("page_trap_count"); 1064} 1065 1066void SafepointSynchronize::deferred_initialize_stat() { 1067 if (init_done) return; 1068 1069 if (PrintSafepointStatisticsCount <= 0) { 1070 fatal("Wrong PrintSafepointStatisticsCount"); 1071 } 1072 1073 // If PrintSafepointStatisticsTimeout is specified, the statistics data will 1074 // be printed right away, in which case, _safepoint_stats will regress to 1075 // a single element array. Otherwise, it is a circular ring buffer with default 1076 // size of PrintSafepointStatisticsCount. 1077 int stats_array_size; 1078 if (PrintSafepointStatisticsTimeout > 0) { 1079 stats_array_size = 1; 1080 PrintSafepointStatistics = true; 1081 } else { 1082 stats_array_size = PrintSafepointStatisticsCount; 1083 } 1084 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size 1085 * sizeof(SafepointStats)); 1086 guarantee(_safepoint_stats != NULL, 1087 "not enough memory for safepoint instrumentation data"); 1088 1089 if (UseCompilerSafepoints && DeferPollingPageLoopCount >= 0) { 1090 need_to_track_page_armed_status = true; 1091 } 1092 init_done = true; 1093} 1094 1095void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) { 1096 assert(init_done, "safepoint statistics array hasn't been initialized"); 1097 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1098 1099 spstat->_time_stamp = _ts_of_current_safepoint; 1100 1101 VM_Operation *op = VMThread::vm_operation(); 1102 spstat->_vmop_type = (op != NULL ? op->type() : -1); 1103 if (op != NULL) { 1104 _safepoint_reasons[spstat->_vmop_type]++; 1105 } 1106 1107 spstat->_nof_total_threads = nof_threads; 1108 spstat->_nof_initial_running_threads = nof_running; 1109 spstat->_nof_threads_hit_page_trap = 0; 1110 1111 // Records the start time of spinning. The real time spent on spinning 1112 // will be adjusted when spin is done. Same trick is applied for time 1113 // spent on waiting for threads to block. 1114 if (nof_running != 0) { 1115 spstat->_time_to_spin = os::javaTimeNanos(); 1116 } else { 1117 spstat->_time_to_spin = 0; 1118 } 1119} 1120 1121void SafepointSynchronize::update_statistics_on_spin_end() { 1122 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1123 1124 jlong cur_time = os::javaTimeNanos(); 1125 1126 spstat->_nof_threads_wait_to_block = _waiting_to_block; 1127 if (spstat->_nof_initial_running_threads != 0) { 1128 spstat->_time_to_spin = cur_time - spstat->_time_to_spin; 1129 } 1130 1131 if (need_to_track_page_armed_status) { 1132 spstat->_page_armed = (PageArmed == 1); 1133 } 1134 1135 // Records the start time of waiting for to block. Updated when block is done. 1136 if (_waiting_to_block != 0) { 1137 spstat->_time_to_wait_to_block = cur_time; 1138 } else { 1139 spstat->_time_to_wait_to_block = 0; 1140 } 1141} 1142 1143void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) { 1144 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1145 1146 if (spstat->_nof_threads_wait_to_block != 0) { 1147 spstat->_time_to_wait_to_block = end_time - 1148 spstat->_time_to_wait_to_block; 1149 } 1150 1151 // Records the end time of sync which will be used to calculate the total 1152 // vm operation time. Again, the real time spending in syncing will be deducted 1153 // from the start of the sync time later when end_statistics is called. 1154 spstat->_time_to_sync = end_time - _safepoint_begin_time; 1155 if (spstat->_time_to_sync > _max_sync_time) { 1156 _max_sync_time = spstat->_time_to_sync; 1157 } 1158 1159 spstat->_time_to_do_cleanups = end_time; 1160} 1161 1162void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) { 1163 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1164 1165 // Record how long spent in cleanup tasks. 1166 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups; 1167 1168 cleanup_end_time = end_time; 1169} 1170 1171void SafepointSynchronize::end_statistics(jlong vmop_end_time) { 1172 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1173 1174 // Update the vm operation time. 1175 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time; 1176 if (spstat->_time_to_exec_vmop > _max_vmop_time) { 1177 _max_vmop_time = spstat->_time_to_exec_vmop; 1178 } 1179 // Only the sync time longer than the specified 1180 // PrintSafepointStatisticsTimeout will be printed out right away. 1181 // By default, it is -1 meaning all samples will be put into the list. 1182 if ( PrintSafepointStatisticsTimeout > 0) { 1183 if (spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) { 1184 print_statistics(); 1185 } 1186 } else { 1187 // The safepoint statistics will be printed out when the _safepoin_stats 1188 // array fills up. 1189 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) { 1190 print_statistics(); 1191 _cur_stat_index = 0; 1192 } else { 1193 _cur_stat_index++; 1194 } 1195 } 1196} 1197 1198void SafepointSynchronize::print_statistics() { 1199 SafepointStats* sstats = _safepoint_stats; 1200 1201 for (int index = 0; index <= _cur_stat_index; index++) { 1202 if (index % 30 == 0) { 1203 print_header(); 1204 } 1205 sstats = &_safepoint_stats[index]; 1206 tty->print("%.3f: ", sstats->_time_stamp); 1207 tty->print("%-26s [" 1208 INT32_FORMAT_W(8)INT32_FORMAT_W(11)INT32_FORMAT_W(15) 1209 " ] ", 1210 sstats->_vmop_type == -1 ? "no vm operation" : 1211 VM_Operation::name(sstats->_vmop_type), 1212 sstats->_nof_total_threads, 1213 sstats->_nof_initial_running_threads, 1214 sstats->_nof_threads_wait_to_block); 1215 // "/ MICROUNITS " is to convert the unit from nanos to millis. 1216 tty->print(" [" 1217 INT64_FORMAT_W(6)INT64_FORMAT_W(6) 1218 INT64_FORMAT_W(6)INT64_FORMAT_W(6) 1219 INT64_FORMAT_W(6)" ] ", 1220 sstats->_time_to_spin / MICROUNITS, 1221 sstats->_time_to_wait_to_block / MICROUNITS, 1222 sstats->_time_to_sync / MICROUNITS, 1223 sstats->_time_to_do_cleanups / MICROUNITS, 1224 sstats->_time_to_exec_vmop / MICROUNITS); 1225 1226 if (need_to_track_page_armed_status) { 1227 tty->print(INT32_FORMAT" ", sstats->_page_armed); 1228 } 1229 tty->print_cr(INT32_FORMAT" ", sstats->_nof_threads_hit_page_trap); 1230 } 1231} 1232 1233// This method will be called when VM exits. It will first call 1234// print_statistics to print out the rest of the sampling. Then 1235// it tries to summarize the sampling. 1236void SafepointSynchronize::print_stat_on_exit() { 1237 if (_safepoint_stats == NULL) return; 1238 1239 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1240 1241 // During VM exit, end_statistics may not get called and in that 1242 // case, if the sync time is less than PrintSafepointStatisticsTimeout, 1243 // don't print it out. 1244 // Approximate the vm op time. 1245 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop = 1246 os::javaTimeNanos() - cleanup_end_time; 1247 1248 if ( PrintSafepointStatisticsTimeout < 0 || 1249 spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) { 1250 print_statistics(); 1251 } 1252 tty->print_cr(""); 1253 1254 // Print out polling page sampling status. 1255 if (!need_to_track_page_armed_status) { 1256 if (UseCompilerSafepoints) { 1257 tty->print_cr("Polling page always armed"); 1258 } 1259 } else { 1260 tty->print_cr("Defer polling page loop count = %d\n", 1261 DeferPollingPageLoopCount); 1262 } 1263 1264 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) { 1265 if (_safepoint_reasons[index] != 0) { 1266 tty->print_cr("%-26s"UINT64_FORMAT_W(10), VM_Operation::name(index), 1267 _safepoint_reasons[index]); 1268 } 1269 } 1270 1271 tty->print_cr(UINT64_FORMAT_W(5)" VM operations coalesced during safepoint", 1272 _coalesced_vmop_count); 1273 tty->print_cr("Maximum sync time "INT64_FORMAT_W(5)" ms", 1274 _max_sync_time / MICROUNITS); 1275 tty->print_cr("Maximum vm operation time (except for Exit VM operation) " 1276 INT64_FORMAT_W(5)" ms", 1277 _max_vmop_time / MICROUNITS); 1278} 1279 1280// ------------------------------------------------------------------------------------------------ 1281// Non-product code 1282 1283#ifndef PRODUCT 1284 1285void SafepointSynchronize::print_state() { 1286 if (_state == _not_synchronized) { 1287 tty->print_cr("not synchronized"); 1288 } else if (_state == _synchronizing || _state == _synchronized) { 1289 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" : 1290 "synchronized"); 1291 1292 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) { 1293 cur->safepoint_state()->print(); 1294 } 1295 } 1296} 1297 1298void SafepointSynchronize::safepoint_msg(const char* format, ...) { 1299 if (ShowSafepointMsgs) { 1300 va_list ap; 1301 va_start(ap, format); 1302 tty->vprint_cr(format, ap); 1303 va_end(ap); 1304 } 1305} 1306 1307#endif // !PRODUCT 1308