annotate hotspot/src/share/vm/runtime/safepoint.cpp @ 5042:f86707fd195a

6933402: RFE: Improve PrintSafepointStatistics output to track cleanup time Summary: Improve the usability of safepoint statistics data. See bug evaluation for more details. Reviewed-by: ysr, dholmes
author xlu
date Wed, 10 Mar 2010 21:42:26 -0800
parents 7be2d5b3b15c
children ebccc0bb7b8e
rev   line source
duke@1 1 /*
xdono@2105 2 * Copyright 1997-2009 Sun Microsystems, Inc. All Rights Reserved.
duke@1 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
duke@1 4 *
duke@1 5 * This code is free software; you can redistribute it and/or modify it
duke@1 6 * under the terms of the GNU General Public License version 2 only, as
duke@1 7 * published by the Free Software Foundation.
duke@1 8 *
duke@1 9 * This code is distributed in the hope that it will be useful, but WITHOUT
duke@1 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
duke@1 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
duke@1 12 * version 2 for more details (a copy is included in the LICENSE file that
duke@1 13 * accompanied this code).
duke@1 14 *
duke@1 15 * You should have received a copy of the GNU General Public License version
duke@1 16 * 2 along with this work; if not, write to the Free Software Foundation,
duke@1 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
duke@1 18 *
duke@1 19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
duke@1 20 * CA 95054 USA or visit www.sun.com if you need additional information or
duke@1 21 * have any questions.
duke@1 22 *
duke@1 23 */
duke@1 24
duke@1 25 # include "incls/_precompiled.incl"
duke@1 26 # include "incls/_safepoint.cpp.incl"
duke@1 27
duke@1 28 // --------------------------------------------------------------------------------------------------
duke@1 29 // Implementation of Safepoint begin/end
duke@1 30
duke@1 31 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
duke@1 32 volatile int SafepointSynchronize::_waiting_to_block = 0;
duke@1 33 volatile int SafepointSynchronize::_safepoint_counter = 0;
xlu@5042 34 long SafepointSynchronize::_end_of_last_safepoint = 0;
duke@1 35 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE
duke@1 36 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only
duke@1 37 static bool timeout_error_printed = false;
duke@1 38
duke@1 39 // Roll all threads forward to a safepoint and suspend them all
duke@1 40 void SafepointSynchronize::begin() {
duke@1 41
duke@1 42 Thread* myThread = Thread::current();
duke@1 43 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint");
duke@1 44
xlu@5042 45 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
xlu@5042 46 _safepoint_begin_time = os::javaTimeNanos();
xlu@5042 47 _ts_of_current_safepoint = tty->time_stamp().seconds();
xlu@5042 48 }
duke@1 49
duke@1 50 #ifndef SERIALGC
duke@1 51 if (UseConcMarkSweepGC) {
duke@1 52 // In the future we should investigate whether CMS can use the
duke@1 53 // more-general mechanism below. DLD (01/05).
duke@1 54 ConcurrentMarkSweepThread::synchronize(false);
ysr@3262 55 } else if (UseG1GC) {
duke@1 56 ConcurrentGCThread::safepoint_synchronize();
duke@1 57 }
duke@1 58 #endif // SERIALGC
duke@1 59
duke@1 60 // By getting the Threads_lock, we assure that no threads are about to start or
duke@1 61 // exit. It is released again in SafepointSynchronize::end().
duke@1 62 Threads_lock->lock();
duke@1 63
duke@1 64 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
duke@1 65
duke@1 66 int nof_threads = Threads::number_of_threads();
duke@1 67
duke@1 68 if (TraceSafepoint) {
duke@1 69 tty->print_cr("Safepoint synchronization initiated. (%d)", nof_threads);
duke@1 70 }
duke@1 71
duke@1 72 RuntimeService::record_safepoint_begin();
duke@1 73
duke@1 74 {
duke@1 75 MutexLocker mu(Safepoint_lock);
duke@1 76
duke@1 77 // Set number of threads to wait for, before we initiate the callbacks
duke@1 78 _waiting_to_block = nof_threads;
duke@1 79 TryingToBlock = 0 ;
duke@1 80 int still_running = nof_threads;
duke@1 81
duke@1 82 // Save the starting time, so that it can be compared to see if this has taken
duke@1 83 // too long to complete.
duke@1 84 jlong safepoint_limit_time;
duke@1 85 timeout_error_printed = false;
duke@1 86
xlu@4006 87 // PrintSafepointStatisticsTimeout can be specified separately. When
xlu@4006 88 // specified, PrintSafepointStatistics will be set to true in
xlu@4006 89 // deferred_initialize_stat method. The initialization has to be done
xlu@4006 90 // early enough to avoid any races. See bug 6880029 for details.
xlu@4006 91 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
xlu@4006 92 deferred_initialize_stat();
xlu@4006 93 }
xlu@4006 94
duke@1 95 // Begin the process of bringing the system to a safepoint.
duke@1 96 // Java threads can be in several different states and are
duke@1 97 // stopped by different mechanisms:
duke@1 98 //
duke@1 99 // 1. Running interpreted
duke@1 100 // The interpeter dispatch table is changed to force it to
duke@1 101 // check for a safepoint condition between bytecodes.
duke@1 102 // 2. Running in native code
duke@1 103 // When returning from the native code, a Java thread must check
duke@1 104 // the safepoint _state to see if we must block. If the
duke@1 105 // VM thread sees a Java thread in native, it does
duke@1 106 // not wait for this thread to block. The order of the memory
duke@1 107 // writes and reads of both the safepoint state and the Java
duke@1 108 // threads state is critical. In order to guarantee that the
duke@1 109 // memory writes are serialized with respect to each other,
duke@1 110 // the VM thread issues a memory barrier instruction
duke@1 111 // (on MP systems). In order to avoid the overhead of issuing
duke@1 112 // a memory barrier for each Java thread making native calls, each Java
duke@1 113 // thread performs a write to a single memory page after changing
duke@1 114 // the thread state. The VM thread performs a sequence of
duke@1 115 // mprotect OS calls which forces all previous writes from all
duke@1 116 // Java threads to be serialized. This is done in the
duke@1 117 // os::serialize_thread_states() call. This has proven to be
duke@1 118 // much more efficient than executing a membar instruction
duke@1 119 // on every call to native code.
duke@1 120 // 3. Running compiled Code
duke@1 121 // Compiled code reads a global (Safepoint Polling) page that
duke@1 122 // is set to fault if we are trying to get to a safepoint.
duke@1 123 // 4. Blocked
duke@1 124 // A thread which is blocked will not be allowed to return from the
duke@1 125 // block condition until the safepoint operation is complete.
duke@1 126 // 5. In VM or Transitioning between states
duke@1 127 // If a Java thread is currently running in the VM or transitioning
duke@1 128 // between states, the safepointing code will wait for the thread to
duke@1 129 // block itself when it attempts transitions to a new state.
duke@1 130 //
duke@1 131 _state = _synchronizing;
duke@1 132 OrderAccess::fence();
duke@1 133
duke@1 134 // Flush all thread states to memory
duke@1 135 if (!UseMembar) {
duke@1 136 os::serialize_thread_states();
duke@1 137 }
duke@1 138
duke@1 139 // Make interpreter safepoint aware
duke@1 140 Interpreter::notice_safepoints();
duke@1 141
duke@1 142 if (UseCompilerSafepoints && DeferPollingPageLoopCount < 0) {
duke@1 143 // Make polling safepoint aware
duke@1 144 guarantee (PageArmed == 0, "invariant") ;
duke@1 145 PageArmed = 1 ;
duke@1 146 os::make_polling_page_unreadable();
duke@1 147 }
duke@1 148
duke@1 149 // Consider using active_processor_count() ... but that call is expensive.
duke@1 150 int ncpus = os::processor_count() ;
duke@1 151
duke@1 152 #ifdef ASSERT
duke@1 153 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
duke@1 154 assert(cur->safepoint_state()->is_running(), "Illegal initial state");
duke@1 155 }
duke@1 156 #endif // ASSERT
duke@1 157
duke@1 158 if (SafepointTimeout)
duke@1 159 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
duke@1 160
duke@1 161 // Iterate through all threads until it have been determined how to stop them all at a safepoint
duke@1 162 unsigned int iterations = 0;
duke@1 163 int steps = 0 ;
duke@1 164 while(still_running > 0) {
duke@1 165 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
duke@1 166 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
duke@1 167 ThreadSafepointState *cur_state = cur->safepoint_state();
duke@1 168 if (cur_state->is_running()) {
duke@1 169 cur_state->examine_state_of_thread();
duke@1 170 if (!cur_state->is_running()) {
duke@1 171 still_running--;
duke@1 172 // consider adjusting steps downward:
duke@1 173 // steps = 0
duke@1 174 // steps -= NNN
duke@1 175 // steps >>= 1
duke@1 176 // steps = MIN(steps, 2000-100)
duke@1 177 // if (iterations != 0) steps -= NNN
duke@1 178 }
duke@1 179 if (TraceSafepoint && Verbose) cur_state->print();
duke@1 180 }
duke@1 181 }
duke@1 182
xlu@4006 183 if (PrintSafepointStatistics && iterations == 0) {
duke@1 184 begin_statistics(nof_threads, still_running);
duke@1 185 }
duke@1 186
duke@1 187 if (still_running > 0) {
duke@1 188 // Check for if it takes to long
duke@1 189 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
duke@1 190 print_safepoint_timeout(_spinning_timeout);
duke@1 191 }
duke@1 192
duke@1 193 // Spin to avoid context switching.
duke@1 194 // There's a tension between allowing the mutators to run (and rendezvous)
duke@1 195 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that
duke@1 196 // a mutator might otherwise use profitably to reach a safepoint. Excessive
duke@1 197 // spinning by the VM thread on a saturated system can increase rendezvous latency.
duke@1 198 // Blocking or yielding incur their own penalties in the form of context switching
duke@1 199 // and the resultant loss of $ residency.
duke@1 200 //
duke@1 201 // Further complicating matters is that yield() does not work as naively expected
duke@1 202 // on many platforms -- yield() does not guarantee that any other ready threads
duke@1 203 // will run. As such we revert yield_all() after some number of iterations.
duke@1 204 // Yield_all() is implemented as a short unconditional sleep on some platforms.
duke@1 205 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
duke@1 206 // can actually increase the time it takes the VM thread to detect that a system-wide
duke@1 207 // stop-the-world safepoint has been reached. In a pathological scenario such as that
duke@1 208 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
duke@1 209 // In that case the mutators will be stalled waiting for the safepoint to complete and the
duke@1 210 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread
duke@1 211 // will eventually wake up and detect that all mutators are safe, at which point
duke@1 212 // we'll again make progress.
duke@1 213 //
duke@1 214 // Beware too that that the VMThread typically runs at elevated priority.
duke@1 215 // Its default priority is higher than the default mutator priority.
duke@1 216 // Obviously, this complicates spinning.
duke@1 217 //
duke@1 218 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
duke@1 219 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
duke@1 220 //
duke@1 221 // See the comments in synchronizer.cpp for additional remarks on spinning.
duke@1 222 //
duke@1 223 // In the future we might:
duke@1 224 // 1. Modify the safepoint scheme to avoid potentally unbounded spinning.
duke@1 225 // This is tricky as the path used by a thread exiting the JVM (say on
duke@1 226 // on JNI call-out) simply stores into its state field. The burden
duke@1 227 // is placed on the VM thread, which must poll (spin).
duke@1 228 // 2. Find something useful to do while spinning. If the safepoint is GC-related
duke@1 229 // we might aggressively scan the stacks of threads that are already safe.
duke@1 230 // 3. Use Solaris schedctl to examine the state of the still-running mutators.
duke@1 231 // If all the mutators are ONPROC there's no reason to sleep or yield.
duke@1 232 // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
duke@1 233 // 5. Check system saturation. If the system is not fully saturated then
duke@1 234 // simply spin and avoid sleep/yield.
duke@1 235 // 6. As still-running mutators rendezvous they could unpark the sleeping
duke@1 236 // VMthread. This works well for still-running mutators that become
duke@1 237 // safe. The VMthread must still poll for mutators that call-out.
duke@1 238 // 7. Drive the policy on time-since-begin instead of iterations.
duke@1 239 // 8. Consider making the spin duration a function of the # of CPUs:
duke@1 240 // Spin = (((ncpus-1) * M) + K) + F(still_running)
duke@1 241 // Alternately, instead of counting iterations of the outer loop
duke@1 242 // we could count the # of threads visited in the inner loop, above.
duke@1 243 // 9. On windows consider using the return value from SwitchThreadTo()
duke@1 244 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
duke@1 245
duke@1 246 if (UseCompilerSafepoints && int(iterations) == DeferPollingPageLoopCount) {
duke@1 247 guarantee (PageArmed == 0, "invariant") ;
duke@1 248 PageArmed = 1 ;
duke@1 249 os::make_polling_page_unreadable();
duke@1 250 }
duke@1 251
duke@1 252 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
duke@1 253 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
duke@1 254 ++steps ;
duke@1 255 if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
duke@1 256 SpinPause() ; // MP-Polite spin
duke@1 257 } else
duke@1 258 if (steps < DeferThrSuspendLoopCount) {
duke@1 259 os::NakedYield() ;
duke@1 260 } else {
duke@1 261 os::yield_all(steps) ;
duke@1 262 // Alternately, the VM thread could transiently depress its scheduling priority or
duke@1 263 // transiently increase the priority of the tardy mutator(s).
duke@1 264 }
duke@1 265
duke@1 266 iterations ++ ;
duke@1 267 }
duke@1 268 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
duke@1 269 }
duke@1 270 assert(still_running == 0, "sanity check");
duke@1 271
duke@1 272 if (PrintSafepointStatistics) {
duke@1 273 update_statistics_on_spin_end();
duke@1 274 }
duke@1 275
duke@1 276 // wait until all threads are stopped
duke@1 277 while (_waiting_to_block > 0) {
duke@1 278 if (TraceSafepoint) tty->print_cr("Waiting for %d thread(s) to block", _waiting_to_block);
duke@1 279 if (!SafepointTimeout || timeout_error_printed) {
duke@1 280 Safepoint_lock->wait(true); // true, means with no safepoint checks
duke@1 281 } else {
duke@1 282 // Compute remaining time
duke@1 283 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
duke@1 284
duke@1 285 // If there is no remaining time, then there is an error
duke@1 286 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
duke@1 287 print_safepoint_timeout(_blocking_timeout);
duke@1 288 }
duke@1 289 }
duke@1 290 }
duke@1 291 assert(_waiting_to_block == 0, "sanity check");
duke@1 292
duke@1 293 #ifndef PRODUCT
duke@1 294 if (SafepointTimeout) {
duke@1 295 jlong current_time = os::javaTimeNanos();
duke@1 296 if (safepoint_limit_time < current_time) {
duke@1 297 tty->print_cr("# SafepointSynchronize: Finished after "
duke@1 298 INT64_FORMAT_W(6) " ms",
duke@1 299 ((current_time - safepoint_limit_time) / MICROUNITS +
duke@1 300 SafepointTimeoutDelay));
duke@1 301 }
duke@1 302 }
duke@1 303 #endif
duke@1 304
duke@1 305 assert((_safepoint_counter & 0x1) == 0, "must be even");
duke@1 306 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
duke@1 307 _safepoint_counter ++;
duke@1 308
duke@1 309 // Record state
duke@1 310 _state = _synchronized;
duke@1 311
duke@1 312 OrderAccess::fence();
duke@1 313
duke@1 314 if (TraceSafepoint) {
duke@1 315 VM_Operation *op = VMThread::vm_operation();
duke@1 316 tty->print_cr("Entering safepoint region: %s", (op != NULL) ? op->name() : "no vm operation");
duke@1 317 }
duke@1 318
duke@1 319 RuntimeService::record_safepoint_synchronized();
duke@1 320 if (PrintSafepointStatistics) {
duke@1 321 update_statistics_on_sync_end(os::javaTimeNanos());
duke@1 322 }
duke@1 323
duke@1 324 // Call stuff that needs to be run when a safepoint is just about to be completed
duke@1 325 do_cleanup_tasks();
xlu@5042 326
xlu@5042 327 if (PrintSafepointStatistics) {
xlu@5042 328 // Record how much time spend on the above cleanup tasks
xlu@5042 329 update_statistics_on_cleanup_end(os::javaTimeNanos());
xlu@5042 330 }
duke@1 331 }
duke@1 332 }
duke@1 333
duke@1 334 // Wake up all threads, so they are ready to resume execution after the safepoint
duke@1 335 // operation has been carried out
duke@1 336 void SafepointSynchronize::end() {
duke@1 337
duke@1 338 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
duke@1 339 assert((_safepoint_counter & 0x1) == 1, "must be odd");
duke@1 340 _safepoint_counter ++;
duke@1 341 // memory fence isn't required here since an odd _safepoint_counter
duke@1 342 // value can do no harm and a fence is issued below anyway.
duke@1 343
duke@1 344 DEBUG_ONLY(Thread* myThread = Thread::current();)
duke@1 345 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
duke@1 346
duke@1 347 if (PrintSafepointStatistics) {
duke@1 348 end_statistics(os::javaTimeNanos());
duke@1 349 }
duke@1 350
duke@1 351 #ifdef ASSERT
duke@1 352 // A pending_exception cannot be installed during a safepoint. The threads
duke@1 353 // may install an async exception after they come back from a safepoint into
duke@1 354 // pending_exception after they unblock. But that should happen later.
duke@1 355 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
duke@1 356 assert (!(cur->has_pending_exception() &&
duke@1 357 cur->safepoint_state()->is_at_poll_safepoint()),
duke@1 358 "safepoint installed a pending exception");
duke@1 359 }
duke@1 360 #endif // ASSERT
duke@1 361
duke@1 362 if (PageArmed) {
duke@1 363 // Make polling safepoint aware
duke@1 364 os::make_polling_page_readable();
duke@1 365 PageArmed = 0 ;
duke@1 366 }
duke@1 367
duke@1 368 // Remove safepoint check from interpreter
duke@1 369 Interpreter::ignore_safepoints();
duke@1 370
duke@1 371 {
duke@1 372 MutexLocker mu(Safepoint_lock);
duke@1 373
duke@1 374 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
duke@1 375
duke@1 376 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
duke@1 377 // when they get restarted.
duke@1 378 _state = _not_synchronized;
duke@1 379 OrderAccess::fence();
duke@1 380
duke@1 381 if (TraceSafepoint) {
duke@1 382 tty->print_cr("Leaving safepoint region");
duke@1 383 }
duke@1 384
duke@1 385 // Start suspended threads
duke@1 386 for(JavaThread *current = Threads::first(); current; current = current->next()) {
twisti@2131 387 // A problem occurring on Solaris is when attempting to restart threads
duke@1 388 // the first #cpus - 1 go well, but then the VMThread is preempted when we get
duke@1 389 // to the next one (since it has been running the longest). We then have
duke@1 390 // to wait for a cpu to become available before we can continue restarting
duke@1 391 // threads.
duke@1 392 // FIXME: This causes the performance of the VM to degrade when active and with
duke@1 393 // large numbers of threads. Apparently this is due to the synchronous nature
duke@1 394 // of suspending threads.
duke@1 395 //
duke@1 396 // TODO-FIXME: the comments above are vestigial and no longer apply.
duke@1 397 // Furthermore, using solaris' schedctl in this particular context confers no benefit
duke@1 398 if (VMThreadHintNoPreempt) {
duke@1 399 os::hint_no_preempt();
duke@1 400 }
duke@1 401 ThreadSafepointState* cur_state = current->safepoint_state();
duke@1 402 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
duke@1 403 cur_state->restart();
duke@1 404 assert(cur_state->is_running(), "safepoint state has not been reset");
duke@1 405 }
duke@1 406
duke@1 407 RuntimeService::record_safepoint_end();
duke@1 408
duke@1 409 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads
duke@1 410 // blocked in signal_thread_blocked
duke@1 411 Threads_lock->unlock();
duke@1 412
duke@1 413 }
duke@1 414 #ifndef SERIALGC
duke@1 415 // If there are any concurrent GC threads resume them.
duke@1 416 if (UseConcMarkSweepGC) {
duke@1 417 ConcurrentMarkSweepThread::desynchronize(false);
ysr@3262 418 } else if (UseG1GC) {
duke@1 419 ConcurrentGCThread::safepoint_desynchronize();
duke@1 420 }
duke@1 421 #endif // SERIALGC
xlu@5042 422 // record this time so VMThread can keep track how much time has elasped
xlu@5042 423 // since last safepoint.
xlu@5042 424 _end_of_last_safepoint = os::javaTimeMillis();
duke@1 425 }
duke@1 426
duke@1 427 bool SafepointSynchronize::is_cleanup_needed() {
duke@1 428 // Need a safepoint if some inline cache buffers is non-empty
duke@1 429 if (!InlineCacheBuffer::is_empty()) return true;
duke@1 430 return false;
duke@1 431 }
duke@1 432
duke@1 433 jlong CounterDecay::_last_timestamp = 0;
duke@1 434
duke@1 435 static void do_method(methodOop m) {
duke@1 436 m->invocation_counter()->decay();
duke@1 437 }
duke@1 438
duke@1 439 void CounterDecay::decay() {
duke@1 440 _last_timestamp = os::javaTimeMillis();
duke@1 441
duke@1 442 // This operation is going to be performed only at the end of a safepoint
duke@1 443 // and hence GC's will not be going on, all Java mutators are suspended
duke@1 444 // at this point and hence SystemDictionary_lock is also not needed.
duke@1 445 assert(SafepointSynchronize::is_at_safepoint(), "can only be executed at a safepoint");
duke@1 446 int nclasses = SystemDictionary::number_of_classes();
duke@1 447 double classes_per_tick = nclasses * (CounterDecayMinIntervalLength * 1e-3 /
duke@1 448 CounterHalfLifeTime);
duke@1 449 for (int i = 0; i < classes_per_tick; i++) {
duke@1 450 klassOop k = SystemDictionary::try_get_next_class();
duke@1 451 if (k != NULL && k->klass_part()->oop_is_instance()) {
duke@1 452 instanceKlass::cast(k)->methods_do(do_method);
duke@1 453 }
duke@1 454 }
duke@1 455 }
duke@1 456
duke@1 457 // Various cleaning tasks that should be done periodically at safepoints
duke@1 458 void SafepointSynchronize::do_cleanup_tasks() {
xlu@5042 459 {
xlu@5042 460 TraceTime t1("deflating idle monitors", TraceSafepoint);
xlu@5042 461 ObjectSynchronizer::deflate_idle_monitors();
duke@1 462 }
duke@1 463
xlu@5042 464 {
xlu@5042 465 TraceTime t2("updating inline caches", TraceSafepoint);
xlu@5042 466 InlineCacheBuffer::update_inline_caches();
xlu@5042 467 }
xlu@5042 468
duke@1 469 if(UseCounterDecay && CounterDecay::is_decay_needed()) {
xlu@5042 470 TraceTime t3("decaying counter", TraceSafepoint);
duke@1 471 CounterDecay::decay();
duke@1 472 }
xlu@5042 473
xlu@5042 474 TraceTime t4("sweeping nmethods", TraceSafepoint);
duke@1 475 NMethodSweeper::sweep();
duke@1 476 }
duke@1 477
duke@1 478
duke@1 479 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
duke@1 480 switch(state) {
duke@1 481 case _thread_in_native:
duke@1 482 // native threads are safe if they have no java stack or have walkable stack
duke@1 483 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
duke@1 484
duke@1 485 // blocked threads should have already have walkable stack
duke@1 486 case _thread_blocked:
duke@1 487 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
duke@1 488 return true;
duke@1 489
duke@1 490 default:
duke@1 491 return false;
duke@1 492 }
duke@1 493 }
duke@1 494
duke@1 495
duke@1 496 // -------------------------------------------------------------------------------------------------------
duke@1 497 // Implementation of Safepoint callback point
duke@1 498
duke@1 499 void SafepointSynchronize::block(JavaThread *thread) {
duke@1 500 assert(thread != NULL, "thread must be set");
duke@1 501 assert(thread->is_Java_thread(), "not a Java thread");
duke@1 502
duke@1 503 // Threads shouldn't block if they are in the middle of printing, but...
duke@1 504 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
duke@1 505
duke@1 506 // Only bail from the block() call if the thread is gone from the
duke@1 507 // thread list; starting to exit should still block.
duke@1 508 if (thread->is_terminated()) {
duke@1 509 // block current thread if we come here from native code when VM is gone
duke@1 510 thread->block_if_vm_exited();
duke@1 511
duke@1 512 // otherwise do nothing
duke@1 513 return;
duke@1 514 }
duke@1 515
duke@1 516 JavaThreadState state = thread->thread_state();
duke@1 517 thread->frame_anchor()->make_walkable(thread);
duke@1 518
duke@1 519 // Check that we have a valid thread_state at this point
duke@1 520 switch(state) {
duke@1 521 case _thread_in_vm_trans:
duke@1 522 case _thread_in_Java: // From compiled code
duke@1 523
duke@1 524 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
duke@1 525 // we pretend we are still in the VM.
duke@1 526 thread->set_thread_state(_thread_in_vm);
duke@1 527
duke@1 528 if (is_synchronizing()) {
duke@1 529 Atomic::inc (&TryingToBlock) ;
duke@1 530 }
duke@1 531
duke@1 532 // We will always be holding the Safepoint_lock when we are examine the state
duke@1 533 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
duke@1 534 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
duke@1 535 Safepoint_lock->lock_without_safepoint_check();
duke@1 536 if (is_synchronizing()) {
duke@1 537 // Decrement the number of threads to wait for and signal vm thread
duke@1 538 assert(_waiting_to_block > 0, "sanity check");
duke@1 539 _waiting_to_block--;
duke@1 540 thread->safepoint_state()->set_has_called_back(true);
duke@1 541
duke@1 542 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
duke@1 543 if (_waiting_to_block == 0) {
duke@1 544 Safepoint_lock->notify_all();
duke@1 545 }
duke@1 546 }
duke@1 547
duke@1 548 // We transition the thread to state _thread_blocked here, but
duke@1 549 // we can't do our usual check for external suspension and then
duke@1 550 // self-suspend after the lock_without_safepoint_check() call
duke@1 551 // below because we are often called during transitions while
duke@1 552 // we hold different locks. That would leave us suspended while
duke@1 553 // holding a resource which results in deadlocks.
duke@1 554 thread->set_thread_state(_thread_blocked);
duke@1 555 Safepoint_lock->unlock();
duke@1 556
duke@1 557 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
duke@1 558 // the entire safepoint, the threads will all line up here during the safepoint.
duke@1 559 Threads_lock->lock_without_safepoint_check();
duke@1 560 // restore original state. This is important if the thread comes from compiled code, so it
duke@1 561 // will continue to execute with the _thread_in_Java state.
duke@1 562 thread->set_thread_state(state);
duke@1 563 Threads_lock->unlock();
duke@1 564 break;
duke@1 565
duke@1 566 case _thread_in_native_trans:
duke@1 567 case _thread_blocked_trans:
duke@1 568 case _thread_new_trans:
duke@1 569 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
duke@1 570 thread->print_thread_state();
duke@1 571 fatal("Deadlock in safepoint code. "
duke@1 572 "Should have called back to the VM before blocking.");
duke@1 573 }
duke@1 574
duke@1 575 // We transition the thread to state _thread_blocked here, but
duke@1 576 // we can't do our usual check for external suspension and then
duke@1 577 // self-suspend after the lock_without_safepoint_check() call
duke@1 578 // below because we are often called during transitions while
duke@1 579 // we hold different locks. That would leave us suspended while
duke@1 580 // holding a resource which results in deadlocks.
duke@1 581 thread->set_thread_state(_thread_blocked);
duke@1 582
duke@1 583 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
duke@1 584 // the safepoint code might still be waiting for it to block. We need to change the state here,
duke@1 585 // so it can see that it is at a safepoint.
duke@1 586
duke@1 587 // Block until the safepoint operation is completed.
duke@1 588 Threads_lock->lock_without_safepoint_check();
duke@1 589
duke@1 590 // Restore state
duke@1 591 thread->set_thread_state(state);
duke@1 592
duke@1 593 Threads_lock->unlock();
duke@1 594 break;
duke@1 595
duke@1 596 default:
duke@1 597 fatal1("Illegal threadstate encountered: %d", state);
duke@1 598 }
duke@1 599
duke@1 600 // Check for pending. async. exceptions or suspends - except if the
duke@1 601 // thread was blocked inside the VM. has_special_runtime_exit_condition()
duke@1 602 // is called last since it grabs a lock and we only want to do that when
duke@1 603 // we must.
duke@1 604 //
duke@1 605 // Note: we never deliver an async exception at a polling point as the
duke@1 606 // compiler may not have an exception handler for it. The polling
duke@1 607 // code will notice the async and deoptimize and the exception will
duke@1 608 // be delivered. (Polling at a return point is ok though). Sure is
duke@1 609 // a lot of bother for a deprecated feature...
duke@1 610 //
duke@1 611 // We don't deliver an async exception if the thread state is
duke@1 612 // _thread_in_native_trans so JNI functions won't be called with
duke@1 613 // a surprising pending exception. If the thread state is going back to java,
duke@1 614 // async exception is checked in check_special_condition_for_native_trans().
duke@1 615
duke@1 616 if (state != _thread_blocked_trans &&
duke@1 617 state != _thread_in_vm_trans &&
duke@1 618 thread->has_special_runtime_exit_condition()) {
duke@1 619 thread->handle_special_runtime_exit_condition(
duke@1 620 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
duke@1 621 }
duke@1 622 }
duke@1 623
duke@1 624 // ------------------------------------------------------------------------------------------------------
duke@1 625 // Exception handlers
duke@1 626
duke@1 627 #ifndef PRODUCT
duke@1 628 #ifdef _LP64
duke@1 629 #define PTR_PAD ""
duke@1 630 #else
duke@1 631 #define PTR_PAD " "
duke@1 632 #endif
duke@1 633
duke@1 634 static void print_ptrs(intptr_t oldptr, intptr_t newptr, bool wasoop) {
duke@1 635 bool is_oop = newptr ? ((oop)newptr)->is_oop() : false;
duke@1 636 tty->print_cr(PTR_FORMAT PTR_PAD " %s %c " PTR_FORMAT PTR_PAD " %s %s",
duke@1 637 oldptr, wasoop?"oop":" ", oldptr == newptr ? ' ' : '!',
duke@1 638 newptr, is_oop?"oop":" ", (wasoop && !is_oop) ? "STALE" : ((wasoop==false&&is_oop==false&&oldptr !=newptr)?"STOMP":" "));
duke@1 639 }
duke@1 640
duke@1 641 static void print_longs(jlong oldptr, jlong newptr, bool wasoop) {
duke@1 642 bool is_oop = newptr ? ((oop)(intptr_t)newptr)->is_oop() : false;
duke@1 643 tty->print_cr(PTR64_FORMAT " %s %c " PTR64_FORMAT " %s %s",
duke@1 644 oldptr, wasoop?"oop":" ", oldptr == newptr ? ' ' : '!',
duke@1 645 newptr, is_oop?"oop":" ", (wasoop && !is_oop) ? "STALE" : ((wasoop==false&&is_oop==false&&oldptr !=newptr)?"STOMP":" "));
duke@1 646 }
duke@1 647
duke@1 648 #ifdef SPARC
duke@1 649 static void print_me(intptr_t *new_sp, intptr_t *old_sp, bool *was_oops) {
duke@1 650 #ifdef _LP64
duke@1 651 tty->print_cr("--------+------address-----+------before-----------+-------after----------+");
duke@1 652 const int incr = 1; // Increment to skip a long, in units of intptr_t
duke@1 653 #else
duke@1 654 tty->print_cr("--------+--address-+------before-----------+-------after----------+");
duke@1 655 const int incr = 2; // Increment to skip a long, in units of intptr_t
duke@1 656 #endif
duke@1 657 tty->print_cr("---SP---|");
duke@1 658 for( int i=0; i<16; i++ ) {
duke@1 659 tty->print("blob %c%d |"PTR_FORMAT" ","LO"[i>>3],i&7,new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); }
duke@1 660 tty->print_cr("--------|");
duke@1 661 for( int i1=0; i1<frame::memory_parameter_word_sp_offset-16; i1++ ) {
duke@1 662 tty->print("argv pad|"PTR_FORMAT" ",new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); }
duke@1 663 tty->print(" pad|"PTR_FORMAT" ",new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++);
duke@1 664 tty->print_cr("--------|");
duke@1 665 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;
duke@1 666 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;
duke@1 667 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;
duke@1 668 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;
duke@1 669 tty->print_cr(" FSR |"PTR_FORMAT" "PTR64_FORMAT" "PTR64_FORMAT,new_sp,*(jlong*)old_sp,*(jlong*)new_sp);
duke@1 670 old_sp += incr; new_sp += incr; was_oops += incr;
duke@1 671 // Skip the floats
duke@1 672 tty->print_cr("--Float-|"PTR_FORMAT,new_sp);
duke@1 673 tty->print_cr("---FP---|");
duke@1 674 old_sp += incr*32; new_sp += incr*32; was_oops += incr*32;
duke@1 675 for( int i2=0; i2<16; i2++ ) {
duke@1 676 tty->print("call %c%d |"PTR_FORMAT" ","LI"[i2>>3],i2&7,new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); }
duke@1 677 tty->print_cr("");
duke@1 678 }
duke@1 679 #endif // SPARC
duke@1 680 #endif // PRODUCT
duke@1 681
duke@1 682
duke@1 683 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
duke@1 684 assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
duke@1 685 assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
duke@1 686 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
duke@1 687
duke@1 688 // Uncomment this to get some serious before/after printing of the
duke@1 689 // Sparc safepoint-blob frame structure.
duke@1 690 /*
duke@1 691 intptr_t* sp = thread->last_Java_sp();
duke@1 692 intptr_t stack_copy[150];
duke@1 693 for( int i=0; i<150; i++ ) stack_copy[i] = sp[i];
duke@1 694 bool was_oops[150];
duke@1 695 for( int i=0; i<150; i++ )
duke@1 696 was_oops[i] = stack_copy[i] ? ((oop)stack_copy[i])->is_oop() : false;
duke@1 697 */
duke@1 698
duke@1 699 if (ShowSafepointMsgs) {
duke@1 700 tty->print("handle_polling_page_exception: ");
duke@1 701 }
duke@1 702
duke@1 703 if (PrintSafepointStatistics) {
duke@1 704 inc_page_trap_count();
duke@1 705 }
duke@1 706
duke@1 707 ThreadSafepointState* state = thread->safepoint_state();
duke@1 708
duke@1 709 state->handle_polling_page_exception();
duke@1 710 // print_me(sp,stack_copy,was_oops);
duke@1 711 }
duke@1 712
duke@1 713
duke@1 714 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
duke@1 715 if (!timeout_error_printed) {
duke@1 716 timeout_error_printed = true;
duke@1 717 // Print out the thread infor which didn't reach the safepoint for debugging
duke@1 718 // purposes (useful when there are lots of threads in the debugger).
duke@1 719 tty->print_cr("");
duke@1 720 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
duke@1 721 if (reason == _spinning_timeout) {
duke@1 722 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
duke@1 723 } else if (reason == _blocking_timeout) {
duke@1 724 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
duke@1 725 }
duke@1 726
duke@1 727 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
duke@1 728 ThreadSafepointState *cur_state;
duke@1 729 ResourceMark rm;
duke@1 730 for(JavaThread *cur_thread = Threads::first(); cur_thread;
duke@1 731 cur_thread = cur_thread->next()) {
duke@1 732 cur_state = cur_thread->safepoint_state();
duke@1 733
duke@1 734 if (cur_thread->thread_state() != _thread_blocked &&
duke@1 735 ((reason == _spinning_timeout && cur_state->is_running()) ||
duke@1 736 (reason == _blocking_timeout && !cur_state->has_called_back()))) {
duke@1 737 tty->print("# ");
duke@1 738 cur_thread->print();
duke@1 739 tty->print_cr("");
duke@1 740 }
duke@1 741 }
duke@1 742 tty->print_cr("# SafepointSynchronize::begin: (End of list)");
duke@1 743 }
duke@1 744
duke@1 745 // To debug the long safepoint, specify both DieOnSafepointTimeout &
duke@1 746 // ShowMessageBoxOnError.
duke@1 747 if (DieOnSafepointTimeout) {
duke@1 748 char msg[1024];
duke@1 749 VM_Operation *op = VMThread::vm_operation();
xlu@1889 750 sprintf(msg, "Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
duke@1 751 SafepointTimeoutDelay,
duke@1 752 op != NULL ? op->name() : "no vm operation");
duke@1 753 fatal(msg);
duke@1 754 }
duke@1 755 }
duke@1 756
duke@1 757
duke@1 758 // -------------------------------------------------------------------------------------------------------
duke@1 759 // Implementation of ThreadSafepointState
duke@1 760
duke@1 761 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
duke@1 762 _thread = thread;
duke@1 763 _type = _running;
duke@1 764 _has_called_back = false;
duke@1 765 _at_poll_safepoint = false;
duke@1 766 }
duke@1 767
duke@1 768 void ThreadSafepointState::create(JavaThread *thread) {
duke@1 769 ThreadSafepointState *state = new ThreadSafepointState(thread);
duke@1 770 thread->set_safepoint_state(state);
duke@1 771 }
duke@1 772
duke@1 773 void ThreadSafepointState::destroy(JavaThread *thread) {
duke@1 774 if (thread->safepoint_state()) {
duke@1 775 delete(thread->safepoint_state());
duke@1 776 thread->set_safepoint_state(NULL);
duke@1 777 }
duke@1 778 }
duke@1 779
duke@1 780 void ThreadSafepointState::examine_state_of_thread() {
duke@1 781 assert(is_running(), "better be running or just have hit safepoint poll");
duke@1 782
duke@1 783 JavaThreadState state = _thread->thread_state();
duke@1 784
duke@1 785 // Check for a thread that is suspended. Note that thread resume tries
duke@1 786 // to grab the Threads_lock which we own here, so a thread cannot be
duke@1 787 // resumed during safepoint synchronization.
duke@1 788
dcubed@3826 789 // We check to see if this thread is suspended without locking to
dcubed@3826 790 // avoid deadlocking with a third thread that is waiting for this
dcubed@3826 791 // thread to be suspended. The third thread can notice the safepoint
dcubed@3826 792 // that we're trying to start at the beginning of its SR_lock->wait()
dcubed@3826 793 // call. If that happens, then the third thread will block on the
dcubed@3826 794 // safepoint while still holding the underlying SR_lock. We won't be
dcubed@3826 795 // able to get the SR_lock and we'll deadlock.
dcubed@3826 796 //
dcubed@3826 797 // We don't need to grab the SR_lock here for two reasons:
dcubed@3826 798 // 1) The suspend flags are both volatile and are set with an
dcubed@3826 799 // Atomic::cmpxchg() call so we should see the suspended
dcubed@3826 800 // state right away.
dcubed@3826 801 // 2) We're being called from the safepoint polling loop; if
dcubed@3826 802 // we don't see the suspended state on this iteration, then
dcubed@3826 803 // we'll come around again.
dcubed@3826 804 //
dcubed@3826 805 bool is_suspended = _thread->is_ext_suspended();
duke@1 806 if (is_suspended) {
duke@1 807 roll_forward(_at_safepoint);
duke@1 808 return;
duke@1 809 }
duke@1 810
duke@1 811 // Some JavaThread states have an initial safepoint state of
duke@1 812 // running, but are actually at a safepoint. We will happily
duke@1 813 // agree and update the safepoint state here.
duke@1 814 if (SafepointSynchronize::safepoint_safe(_thread, state)) {
duke@1 815 roll_forward(_at_safepoint);
duke@1 816 return;
duke@1 817 }
duke@1 818
duke@1 819 if (state == _thread_in_vm) {
duke@1 820 roll_forward(_call_back);
duke@1 821 return;
duke@1 822 }
duke@1 823
duke@1 824 // All other thread states will continue to run until they
duke@1 825 // transition and self-block in state _blocked
duke@1 826 // Safepoint polling in compiled code causes the Java threads to do the same.
duke@1 827 // Note: new threads may require a malloc so they must be allowed to finish
duke@1 828
duke@1 829 assert(is_running(), "examine_state_of_thread on non-running thread");
duke@1 830 return;
duke@1 831 }
duke@1 832
duke@1 833 // Returns true is thread could not be rolled forward at present position.
duke@1 834 void ThreadSafepointState::roll_forward(suspend_type type) {
duke@1 835 _type = type;
duke@1 836
duke@1 837 switch(_type) {
duke@1 838 case _at_safepoint:
duke@1 839 SafepointSynchronize::signal_thread_at_safepoint();
duke@1 840 break;
duke@1 841
duke@1 842 case _call_back:
duke@1 843 set_has_called_back(false);
duke@1 844 break;
duke@1 845
duke@1 846 case _running:
duke@1 847 default:
duke@1 848 ShouldNotReachHere();
duke@1 849 }
duke@1 850 }
duke@1 851
duke@1 852 void ThreadSafepointState::restart() {
duke@1 853 switch(type()) {
duke@1 854 case _at_safepoint:
duke@1 855 case _call_back:
duke@1 856 break;
duke@1 857
duke@1 858 case _running:
duke@1 859 default:
duke@1 860 tty->print_cr("restart thread "INTPTR_FORMAT" with state %d",
duke@1 861 _thread, _type);
duke@1 862 _thread->print();
duke@1 863 ShouldNotReachHere();
duke@1 864 }
duke@1 865 _type = _running;
duke@1 866 set_has_called_back(false);
duke@1 867 }
duke@1 868
duke@1 869
duke@1 870 void ThreadSafepointState::print_on(outputStream *st) const {
duke@1 871 const char *s;
duke@1 872
duke@1 873 switch(_type) {
duke@1 874 case _running : s = "_running"; break;
duke@1 875 case _at_safepoint : s = "_at_safepoint"; break;
duke@1 876 case _call_back : s = "_call_back"; break;
duke@1 877 default:
duke@1 878 ShouldNotReachHere();
duke@1 879 }
duke@1 880
duke@1 881 st->print_cr("Thread: " INTPTR_FORMAT
duke@1 882 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
duke@1 883 _thread, _thread->osthread()->thread_id(), s, _has_called_back,
duke@1 884 _at_poll_safepoint);
duke@1 885
duke@1 886 _thread->print_thread_state_on(st);
duke@1 887 }
duke@1 888
duke@1 889
duke@1 890 // ---------------------------------------------------------------------------------------------------------------------
duke@1 891
duke@1 892 // Block the thread at the safepoint poll or poll return.
duke@1 893 void ThreadSafepointState::handle_polling_page_exception() {
duke@1 894
duke@1 895 // Check state. block() will set thread state to thread_in_vm which will
duke@1 896 // cause the safepoint state _type to become _call_back.
duke@1 897 assert(type() == ThreadSafepointState::_running,
duke@1 898 "polling page exception on thread not running state");
duke@1 899
duke@1 900 // Step 1: Find the nmethod from the return address
duke@1 901 if (ShowSafepointMsgs && Verbose) {
duke@1 902 tty->print_cr("Polling page exception at " INTPTR_FORMAT, thread()->saved_exception_pc());
duke@1 903 }
duke@1 904 address real_return_addr = thread()->saved_exception_pc();
duke@1 905
duke@1 906 CodeBlob *cb = CodeCache::find_blob(real_return_addr);
duke@1 907 assert(cb != NULL && cb->is_nmethod(), "return address should be in nmethod");
duke@1 908 nmethod* nm = (nmethod*)cb;
duke@1 909
duke@1 910 // Find frame of caller
duke@1 911 frame stub_fr = thread()->last_frame();
duke@1 912 CodeBlob* stub_cb = stub_fr.cb();
duke@1 913 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
duke@1 914 RegisterMap map(thread(), true);
duke@1 915 frame caller_fr = stub_fr.sender(&map);
duke@1 916
duke@1 917 // Should only be poll_return or poll
duke@1 918 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
duke@1 919
duke@1 920 // This is a poll immediately before a return. The exception handling code
duke@1 921 // has already had the effect of causing the return to occur, so the execution
duke@1 922 // will continue immediately after the call. In addition, the oopmap at the
duke@1 923 // return point does not mark the return value as an oop (if it is), so
duke@1 924 // it needs a handle here to be updated.
duke@1 925 if( nm->is_at_poll_return(real_return_addr) ) {
duke@1 926 // See if return type is an oop.
duke@1 927 bool return_oop = nm->method()->is_returning_oop();
duke@1 928 Handle return_value;
duke@1 929 if (return_oop) {
duke@1 930 // The oop result has been saved on the stack together with all
duke@1 931 // the other registers. In order to preserve it over GCs we need
duke@1 932 // to keep it in a handle.
duke@1 933 oop result = caller_fr.saved_oop_result(&map);
duke@1 934 assert(result == NULL || result->is_oop(), "must be oop");
duke@1 935 return_value = Handle(thread(), result);
duke@1 936 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
duke@1 937 }
duke@1 938
duke@1 939 // Block the thread
duke@1 940 SafepointSynchronize::block(thread());
duke@1 941
duke@1 942 // restore oop result, if any
duke@1 943 if (return_oop) {
duke@1 944 caller_fr.set_saved_oop_result(&map, return_value());
duke@1 945 }
duke@1 946 }
duke@1 947
duke@1 948 // This is a safepoint poll. Verify the return address and block.
duke@1 949 else {
duke@1 950 set_at_poll_safepoint(true);
duke@1 951
duke@1 952 // verify the blob built the "return address" correctly
duke@1 953 assert(real_return_addr == caller_fr.pc(), "must match");
duke@1 954
duke@1 955 // Block the thread
duke@1 956 SafepointSynchronize::block(thread());
duke@1 957 set_at_poll_safepoint(false);
duke@1 958
duke@1 959 // If we have a pending async exception deoptimize the frame
duke@1 960 // as otherwise we may never deliver it.
duke@1 961 if (thread()->has_async_condition()) {
duke@1 962 ThreadInVMfromJavaNoAsyncException __tiv(thread());
duke@1 963 VM_DeoptimizeFrame deopt(thread(), caller_fr.id());
duke@1 964 VMThread::execute(&deopt);
duke@1 965 }
duke@1 966
duke@1 967 // If an exception has been installed we must check for a pending deoptimization
duke@1 968 // Deoptimize frame if exception has been thrown.
duke@1 969
duke@1 970 if (thread()->has_pending_exception() ) {
duke@1 971 RegisterMap map(thread(), true);
duke@1 972 frame caller_fr = stub_fr.sender(&map);
duke@1 973 if (caller_fr.is_deoptimized_frame()) {
duke@1 974 // The exception patch will destroy registers that are still
duke@1 975 // live and will be needed during deoptimization. Defer the
duke@1 976 // Async exception should have defered the exception until the
duke@1 977 // next safepoint which will be detected when we get into
duke@1 978 // the interpreter so if we have an exception now things
duke@1 979 // are messed up.
duke@1 980
duke@1 981 fatal("Exception installed and deoptimization is pending");
duke@1 982 }
duke@1 983 }
duke@1 984 }
duke@1 985 }
duke@1 986
duke@1 987
duke@1 988 //
duke@1 989 // Statistics & Instrumentations
duke@1 990 //
duke@1 991 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL;
xlu@5042 992 jlong SafepointSynchronize::_safepoint_begin_time = 0;
duke@1 993 int SafepointSynchronize::_cur_stat_index = 0;
duke@1 994 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
duke@1 995 julong SafepointSynchronize::_coalesced_vmop_count = 0;
duke@1 996 jlong SafepointSynchronize::_max_sync_time = 0;
xlu@5042 997 jlong SafepointSynchronize::_max_vmop_time = 0;
xlu@5042 998 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f;
duke@1 999
xlu@5042 1000 static jlong cleanup_end_time = 0;
duke@1 1001 static bool need_to_track_page_armed_status = false;
duke@1 1002 static bool init_done = false;
duke@1 1003
xlu@5042 1004 // Helper method to print the header.
xlu@5042 1005 static void print_header() {
xlu@5042 1006 tty->print(" vmop "
xlu@5042 1007 "[threads: total initially_running wait_to_block] ");
xlu@5042 1008 tty->print("[time: spin block sync cleanup vmop] ");
xlu@5042 1009
xlu@5042 1010 // no page armed status printed out if it is always armed.
xlu@5042 1011 if (need_to_track_page_armed_status) {
xlu@5042 1012 tty->print("page_armed ");
xlu@5042 1013 }
xlu@5042 1014
xlu@5042 1015 tty->print_cr("page_trap_count");
xlu@5042 1016 }
xlu@5042 1017
duke@1 1018 void SafepointSynchronize::deferred_initialize_stat() {
duke@1 1019 if (init_done) return;
duke@1 1020
duke@1 1021 if (PrintSafepointStatisticsCount <= 0) {
duke@1 1022 fatal("Wrong PrintSafepointStatisticsCount");
duke@1 1023 }
duke@1 1024
duke@1 1025 // If PrintSafepointStatisticsTimeout is specified, the statistics data will
duke@1 1026 // be printed right away, in which case, _safepoint_stats will regress to
duke@1 1027 // a single element array. Otherwise, it is a circular ring buffer with default
duke@1 1028 // size of PrintSafepointStatisticsCount.
duke@1 1029 int stats_array_size;
duke@1 1030 if (PrintSafepointStatisticsTimeout > 0) {
duke@1 1031 stats_array_size = 1;
duke@1 1032 PrintSafepointStatistics = true;
duke@1 1033 } else {
duke@1 1034 stats_array_size = PrintSafepointStatisticsCount;
duke@1 1035 }
duke@1 1036 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
duke@1 1037 * sizeof(SafepointStats));
duke@1 1038 guarantee(_safepoint_stats != NULL,
duke@1 1039 "not enough memory for safepoint instrumentation data");
duke@1 1040
duke@1 1041 if (UseCompilerSafepoints && DeferPollingPageLoopCount >= 0) {
duke@1 1042 need_to_track_page_armed_status = true;
duke@1 1043 }
duke@1 1044 init_done = true;
duke@1 1045 }
duke@1 1046
duke@1 1047 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
xlu@4006 1048 assert(init_done, "safepoint statistics array hasn't been initialized");
duke@1 1049 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
duke@1 1050
xlu@5042 1051 spstat->_time_stamp = _ts_of_current_safepoint;
xlu@5042 1052
duke@1 1053 VM_Operation *op = VMThread::vm_operation();
duke@1 1054 spstat->_vmop_type = (op != NULL ? op->type() : -1);
duke@1 1055 if (op != NULL) {
duke@1 1056 _safepoint_reasons[spstat->_vmop_type]++;
duke@1 1057 }
duke@1 1058
duke@1 1059 spstat->_nof_total_threads = nof_threads;
duke@1 1060 spstat->_nof_initial_running_threads = nof_running;
duke@1 1061 spstat->_nof_threads_hit_page_trap = 0;
duke@1 1062
duke@1 1063 // Records the start time of spinning. The real time spent on spinning
duke@1 1064 // will be adjusted when spin is done. Same trick is applied for time
duke@1 1065 // spent on waiting for threads to block.
duke@1 1066 if (nof_running != 0) {
duke@1 1067 spstat->_time_to_spin = os::javaTimeNanos();
duke@1 1068 } else {
duke@1 1069 spstat->_time_to_spin = 0;
duke@1 1070 }
duke@1 1071 }
duke@1 1072
duke@1 1073 void SafepointSynchronize::update_statistics_on_spin_end() {
duke@1 1074 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
duke@1 1075
duke@1 1076 jlong cur_time = os::javaTimeNanos();
duke@1 1077
duke@1 1078 spstat->_nof_threads_wait_to_block = _waiting_to_block;
duke@1 1079 if (spstat->_nof_initial_running_threads != 0) {
duke@1 1080 spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
duke@1 1081 }
duke@1 1082
duke@1 1083 if (need_to_track_page_armed_status) {
duke@1 1084 spstat->_page_armed = (PageArmed == 1);
duke@1 1085 }
duke@1 1086
duke@1 1087 // Records the start time of waiting for to block. Updated when block is done.
duke@1 1088 if (_waiting_to_block != 0) {
duke@1 1089 spstat->_time_to_wait_to_block = cur_time;
duke@1 1090 } else {
duke@1 1091 spstat->_time_to_wait_to_block = 0;
duke@1 1092 }
duke@1 1093 }
duke@1 1094
duke@1 1095 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
duke@1 1096 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
duke@1 1097
duke@1 1098 if (spstat->_nof_threads_wait_to_block != 0) {
duke@1 1099 spstat->_time_to_wait_to_block = end_time -
duke@1 1100 spstat->_time_to_wait_to_block;
duke@1 1101 }
duke@1 1102
duke@1 1103 // Records the end time of sync which will be used to calculate the total
duke@1 1104 // vm operation time. Again, the real time spending in syncing will be deducted
duke@1 1105 // from the start of the sync time later when end_statistics is called.
xlu@5042 1106 spstat->_time_to_sync = end_time - _safepoint_begin_time;
duke@1 1107 if (spstat->_time_to_sync > _max_sync_time) {
duke@1 1108 _max_sync_time = spstat->_time_to_sync;
duke@1 1109 }
xlu@5042 1110
xlu@5042 1111 spstat->_time_to_do_cleanups = end_time;
xlu@5042 1112 }
xlu@5042 1113
xlu@5042 1114 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
xlu@5042 1115 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
xlu@5042 1116
xlu@5042 1117 // Record how long spent in cleanup tasks.
xlu@5042 1118 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
xlu@5042 1119
xlu@5042 1120 cleanup_end_time = end_time;
duke@1 1121 }
duke@1 1122
duke@1 1123 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
duke@1 1124 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
duke@1 1125
duke@1 1126 // Update the vm operation time.
xlu@5042 1127 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time;
xlu@5042 1128 if (spstat->_time_to_exec_vmop > _max_vmop_time) {
xlu@5042 1129 _max_vmop_time = spstat->_time_to_exec_vmop;
xlu@5042 1130 }
duke@1 1131 // Only the sync time longer than the specified
duke@1 1132 // PrintSafepointStatisticsTimeout will be printed out right away.
duke@1 1133 // By default, it is -1 meaning all samples will be put into the list.
duke@1 1134 if ( PrintSafepointStatisticsTimeout > 0) {
duke@1 1135 if (spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
duke@1 1136 print_statistics();
duke@1 1137 }
duke@1 1138 } else {
duke@1 1139 // The safepoint statistics will be printed out when the _safepoin_stats
duke@1 1140 // array fills up.
xlu@5042 1141 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) {
duke@1 1142 print_statistics();
duke@1 1143 _cur_stat_index = 0;
xlu@5042 1144 } else {
xlu@5042 1145 _cur_stat_index++;
duke@1 1146 }
duke@1 1147 }
duke@1 1148 }
duke@1 1149
duke@1 1150 void SafepointSynchronize::print_statistics() {
duke@1 1151 SafepointStats* sstats = _safepoint_stats;
duke@1 1152
xlu@5042 1153 for (int index = 0; index <= _cur_stat_index; index++) {
xlu@5042 1154 if (index % 30 == 0) {
xlu@5042 1155 print_header();
xlu@5042 1156 }
duke@1 1157 sstats = &_safepoint_stats[index];
xlu@5042 1158 tty->print("%.3f: ", sstats->_time_stamp);
xlu@5042 1159 tty->print("%-26s ["
duke@1 1160 INT32_FORMAT_W(8)INT32_FORMAT_W(11)INT32_FORMAT_W(15)
xlu@5042 1161 " ] ",
duke@1 1162 sstats->_vmop_type == -1 ? "no vm operation" :
duke@1 1163 VM_Operation::name(sstats->_vmop_type),
duke@1 1164 sstats->_nof_total_threads,
duke@1 1165 sstats->_nof_initial_running_threads,
duke@1 1166 sstats->_nof_threads_wait_to_block);
duke@1 1167 // "/ MICROUNITS " is to convert the unit from nanos to millis.
xlu@5042 1168 tty->print(" ["
xlu@5042 1169 INT64_FORMAT_W(6)INT64_FORMAT_W(6)
xlu@5042 1170 INT64_FORMAT_W(6)INT64_FORMAT_W(6)
xlu@5042 1171 INT64_FORMAT_W(6)" ] ",
duke@1 1172 sstats->_time_to_spin / MICROUNITS,
duke@1 1173 sstats->_time_to_wait_to_block / MICROUNITS,
duke@1 1174 sstats->_time_to_sync / MICROUNITS,
xlu@5042 1175 sstats->_time_to_do_cleanups / MICROUNITS,
xlu@5042 1176 sstats->_time_to_exec_vmop / MICROUNITS);
duke@1 1177
duke@1 1178 if (need_to_track_page_armed_status) {
duke@1 1179 tty->print(INT32_FORMAT" ", sstats->_page_armed);
duke@1 1180 }
duke@1 1181 tty->print_cr(INT32_FORMAT" ", sstats->_nof_threads_hit_page_trap);
duke@1 1182 }
duke@1 1183 }
duke@1 1184
duke@1 1185 // This method will be called when VM exits. It will first call
duke@1 1186 // print_statistics to print out the rest of the sampling. Then
duke@1 1187 // it tries to summarize the sampling.
duke@1 1188 void SafepointSynchronize::print_stat_on_exit() {
duke@1 1189 if (_safepoint_stats == NULL) return;
duke@1 1190
duke@1 1191 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
duke@1 1192
duke@1 1193 // During VM exit, end_statistics may not get called and in that
duke@1 1194 // case, if the sync time is less than PrintSafepointStatisticsTimeout,
duke@1 1195 // don't print it out.
duke@1 1196 // Approximate the vm op time.
duke@1 1197 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
xlu@5042 1198 os::javaTimeNanos() - cleanup_end_time;
duke@1 1199
duke@1 1200 if ( PrintSafepointStatisticsTimeout < 0 ||
duke@1 1201 spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
duke@1 1202 print_statistics();
duke@1 1203 }
duke@1 1204 tty->print_cr("");
duke@1 1205
duke@1 1206 // Print out polling page sampling status.
duke@1 1207 if (!need_to_track_page_armed_status) {
duke@1 1208 if (UseCompilerSafepoints) {
duke@1 1209 tty->print_cr("Polling page always armed");
duke@1 1210 }
duke@1 1211 } else {
duke@1 1212 tty->print_cr("Defer polling page loop count = %d\n",
duke@1 1213 DeferPollingPageLoopCount);
duke@1 1214 }
duke@1 1215
duke@1 1216 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
duke@1 1217 if (_safepoint_reasons[index] != 0) {
duke@1 1218 tty->print_cr("%-26s"UINT64_FORMAT_W(10), VM_Operation::name(index),
duke@1 1219 _safepoint_reasons[index]);
duke@1 1220 }
duke@1 1221 }
duke@1 1222
duke@1 1223 tty->print_cr(UINT64_FORMAT_W(5)" VM operations coalesced during safepoint",
duke@1 1224 _coalesced_vmop_count);
duke@1 1225 tty->print_cr("Maximum sync time "INT64_FORMAT_W(5)" ms",
duke@1 1226 _max_sync_time / MICROUNITS);
xlu@5042 1227 tty->print_cr("Maximum vm operation time (except for Exit VM operation) "
xlu@5042 1228 INT64_FORMAT_W(5)" ms",
xlu@5042 1229 _max_vmop_time / MICROUNITS);
duke@1 1230 }
duke@1 1231
duke@1 1232 // ------------------------------------------------------------------------------------------------
duke@1 1233 // Non-product code
duke@1 1234
duke@1 1235 #ifndef PRODUCT
duke@1 1236
duke@1 1237 void SafepointSynchronize::print_state() {
duke@1 1238 if (_state == _not_synchronized) {
duke@1 1239 tty->print_cr("not synchronized");
duke@1 1240 } else if (_state == _synchronizing || _state == _synchronized) {
duke@1 1241 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
duke@1 1242 "synchronized");
duke@1 1243
duke@1 1244 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
duke@1 1245 cur->safepoint_state()->print();
duke@1 1246 }
duke@1 1247 }
duke@1 1248 }
duke@1 1249
duke@1 1250 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
duke@1 1251 if (ShowSafepointMsgs) {
duke@1 1252 va_list ap;
duke@1 1253 va_start(ap, format);
duke@1 1254 tty->vprint_cr(format, ap);
duke@1 1255 va_end(ap);
duke@1 1256 }
duke@1 1257 }
duke@1 1258
duke@1 1259 #endif // !PRODUCT