annotate src/hotspot/share/runtime/safepoint.cpp @ 51582:7f462e8383f6

8206003: SafepointSynchronize with TLH: StoreStore barriers should be moved out of the loop Reviewed-by: eosterlund, rehn, dholmes
author mdoerr
date Mon, 02 Jul 2018 11:46:15 +0200
parents 83aec1d357d4
children f939a67fea30
rev   line source
duke@1 1 /*
coleenp@49492 2 * Copyright (c) 1997, 2018, Oracle and/or its affiliates. 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 *
trims@5547 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
trims@5547 20 * or visit www.oracle.com if you need additional information or have any
trims@5547 21 * questions.
duke@1 22 *
duke@1 23 */
duke@1 24
stefank@7397 25 #include "precompiled.hpp"
gziemski@47955 26 #include "classfile/classLoaderData.hpp"
gziemski@24426 27 #include "classfile/stringTable.hpp"
mgronlun@34666 28 #include "classfile/symbolTable.hpp"
stefank@7397 29 #include "classfile/systemDictionary.hpp"
stefank@7397 30 #include "code/codeCache.hpp"
stefank@7397 31 #include "code/icBuffer.hpp"
stefank@7397 32 #include "code/nmethod.hpp"
stefank@7397 33 #include "code/pcDesc.hpp"
stefank@7397 34 #include "code/scopeDesc.hpp"
pliden@30764 35 #include "gc/shared/collectedHeap.hpp"
stefank@50089 36 #include "gc/shared/gcLocker.hpp"
rkennke@46702 37 #include "gc/shared/strongRootsScope.hpp"
rkennke@46702 38 #include "gc/shared/workgroup.hpp"
stefank@7397 39 #include "interpreter/interpreter.hpp"
egahlin@50662 40 #include "jfr/jfrEvents.hpp"
rprotacio@33763 41 #include "logging/log.hpp"
stuefe@46701 42 #include "logging/logStream.hpp"
stefank@7397 43 #include "memory/resourceArea.hpp"
stefank@49824 44 #include "memory/universe.hpp"
stefank@7397 45 #include "oops/oop.inline.hpp"
coleenp@8076 46 #include "oops/symbol.hpp"
dholmes@40655 47 #include "runtime/atomic.hpp"
stefank@7397 48 #include "runtime/compilationPolicy.hpp"
stefank@7397 49 #include "runtime/deoptimization.hpp"
stefank@7397 50 #include "runtime/frame.inline.hpp"
coleenp@49914 51 #include "runtime/interfaceSupport.inline.hpp"
stefank@7397 52 #include "runtime/mutexLocker.hpp"
coleenp@51033 53 #include "runtime/orderAccess.hpp"
stefank@7397 54 #include "runtime/osThread.hpp"
stefank@7397 55 #include "runtime/safepoint.hpp"
rehn@48069 56 #include "runtime/safepointMechanism.inline.hpp"
stefank@7397 57 #include "runtime/signature.hpp"
stefank@7397 58 #include "runtime/stubCodeGenerator.hpp"
stefank@7397 59 #include "runtime/stubRoutines.hpp"
stefank@7397 60 #include "runtime/sweeper.hpp"
stefank@7397 61 #include "runtime/synchronizer.hpp"
stefank@14583 62 #include "runtime/thread.inline.hpp"
dcubed@48321 63 #include "runtime/threadSMR.hpp"
rehn@37161 64 #include "runtime/timerTrace.hpp"
stefank@7397 65 #include "services/runtimeService.hpp"
stefank@7397 66 #include "utilities/events.hpp"
jprovino@15482 67 #include "utilities/macros.hpp"
stefank@7397 68 #ifdef COMPILER1
stefank@7397 69 #include "c1/c1_globals.hpp"
stefank@7397 70 #endif
duke@1 71
egahlin@50662 72 template <typename E>
egahlin@50662 73 static void set_current_safepoint_id(E* event, int adjustment = 0) {
egahlin@50662 74 assert(event != NULL, "invariant");
egahlin@50662 75 event->set_safepointId(SafepointSynchronize::safepoint_counter() + adjustment);
egahlin@50662 76 }
egahlin@50662 77
egahlin@50662 78 static void post_safepoint_begin_event(EventSafepointBegin* event,
egahlin@50662 79 int thread_count,
egahlin@50662 80 int critical_thread_count) {
egahlin@50662 81 assert(event != NULL, "invariant");
egahlin@50662 82 assert(event->should_commit(), "invariant");
egahlin@50662 83 set_current_safepoint_id(event);
egahlin@50662 84 event->set_totalThreadCount(thread_count);
egahlin@50662 85 event->set_jniCriticalThreadCount(critical_thread_count);
egahlin@50662 86 event->commit();
egahlin@50662 87 }
egahlin@50662 88
egahlin@50662 89 static void post_safepoint_cleanup_event(EventSafepointCleanup* event) {
egahlin@50662 90 assert(event != NULL, "invariant");
egahlin@50662 91 assert(event->should_commit(), "invariant");
egahlin@50662 92 set_current_safepoint_id(event);
egahlin@50662 93 event->commit();
egahlin@50662 94 }
egahlin@50662 95
egahlin@50662 96 static void post_safepoint_synchronize_event(EventSafepointStateSynchronization* event,
egahlin@50662 97 int initial_number_of_threads,
egahlin@50662 98 int threads_waiting_to_block,
egahlin@50662 99 unsigned int iterations) {
egahlin@50662 100 assert(event != NULL, "invariant");
egahlin@50662 101 if (event->should_commit()) {
egahlin@50662 102 // Group this event together with the ones committed after the counter is increased
egahlin@50662 103 set_current_safepoint_id(event, 1);
egahlin@50662 104 event->set_initialThreadCount(initial_number_of_threads);
egahlin@50662 105 event->set_runningThreadCount(threads_waiting_to_block);
egahlin@50662 106 event->set_iterations(iterations);
egahlin@50662 107 event->commit();
egahlin@50662 108 }
egahlin@50662 109 }
egahlin@50662 110
egahlin@50662 111 static void post_safepoint_wait_blocked_event(EventSafepointWaitBlocked* event,
egahlin@50662 112 int initial_threads_waiting_to_block) {
egahlin@50662 113 assert(event != NULL, "invariant");
egahlin@50662 114 assert(event->should_commit(), "invariant");
egahlin@50662 115 set_current_safepoint_id(event);
egahlin@50662 116 event->set_runningThreadCount(initial_threads_waiting_to_block);
egahlin@50662 117 event->commit();
egahlin@50662 118 }
egahlin@50662 119
egahlin@50662 120 static void post_safepoint_cleanup_task_event(EventSafepointCleanupTask* event,
egahlin@50662 121 const char* name) {
egahlin@50662 122 assert(event != NULL, "invariant");
egahlin@50662 123 if (event->should_commit()) {
egahlin@50662 124 set_current_safepoint_id(event);
egahlin@50662 125 event->set_name(name);
egahlin@50662 126 event->commit();
egahlin@50662 127 }
egahlin@50662 128 }
egahlin@50662 129
egahlin@50662 130 static void post_safepoint_end_event(EventSafepointEnd* event) {
egahlin@50662 131 assert(event != NULL, "invariant");
egahlin@50662 132 if (event->should_commit()) {
egahlin@50662 133 // Group this event together with the ones committed before the counter increased
egahlin@50662 134 set_current_safepoint_id(event, -1);
egahlin@50662 135 event->commit();
egahlin@50662 136 }
egahlin@50662 137 }
egahlin@50662 138
duke@1 139 // --------------------------------------------------------------------------------------------------
duke@1 140 // Implementation of Safepoint begin/end
duke@1 141
duke@1 142 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
duke@1 143 volatile int SafepointSynchronize::_waiting_to_block = 0;
duke@1 144 volatile int SafepointSynchronize::_safepoint_counter = 0;
never@11631 145 int SafepointSynchronize::_current_jni_active_count = 0;
xlu@5042 146 long SafepointSynchronize::_end_of_last_safepoint = 0;
hseigel@49600 147 int SafepointSynchronize::_defer_thr_suspend_loop_count = 4000;
hseigel@49600 148 static const int safepoint_spin_before_yield = 2000;
duke@1 149 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE
duke@1 150 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only
duke@1 151 static bool timeout_error_printed = false;
duke@1 152
duke@1 153 // Roll all threads forward to a safepoint and suspend them all
duke@1 154 void SafepointSynchronize::begin() {
dsimms@37176 155 EventSafepointBegin begin_event;
duke@1 156 Thread* myThread = Thread::current();
duke@1 157 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint");
duke@1 158
xlu@5042 159 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
xlu@5042 160 _safepoint_begin_time = os::javaTimeNanos();
xlu@5042 161 _ts_of_current_safepoint = tty->time_stamp().seconds();
xlu@5042 162 }
duke@1 163
eosterlund@47791 164 Universe::heap()->safepoint_synchronize_begin();
duke@1 165
duke@1 166 // By getting the Threads_lock, we assure that no threads are about to start or
duke@1 167 // exit. It is released again in SafepointSynchronize::end().
duke@1 168 Threads_lock->lock();
duke@1 169
duke@1 170 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
duke@1 171
duke@1 172 int nof_threads = Threads::number_of_threads();
duke@1 173
coleenp@48775 174 log_debug(safepoint)("Safepoint synchronization initiated. (%d threads)", nof_threads);
duke@1 175
duke@1 176 RuntimeService::record_safepoint_begin();
duke@1 177
duke@1 178 MutexLocker mu(Safepoint_lock);
duke@1 179
never@11631 180 // Reset the count of active JNI critical threads
never@11631 181 _current_jni_active_count = 0;
never@11631 182
duke@1 183 // Set number of threads to wait for, before we initiate the callbacks
duke@1 184 _waiting_to_block = nof_threads;
duke@1 185 TryingToBlock = 0 ;
duke@1 186 int still_running = nof_threads;
duke@1 187
duke@1 188 // Save the starting time, so that it can be compared to see if this has taken
duke@1 189 // too long to complete.
goetz@33589 190 jlong safepoint_limit_time = 0;
duke@1 191 timeout_error_printed = false;
duke@1 192
xlu@4006 193 // PrintSafepointStatisticsTimeout can be specified separately. When
xlu@4006 194 // specified, PrintSafepointStatistics will be set to true in
xlu@4006 195 // deferred_initialize_stat method. The initialization has to be done
xlu@4006 196 // early enough to avoid any races. See bug 6880029 for details.
xlu@4006 197 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
xlu@4006 198 deferred_initialize_stat();
xlu@4006 199 }
xlu@4006 200
duke@1 201 // Begin the process of bringing the system to a safepoint.
duke@1 202 // Java threads can be in several different states and are
duke@1 203 // stopped by different mechanisms:
duke@1 204 //
duke@1 205 // 1. Running interpreted
jwilhelm@22551 206 // The interpreter dispatch table is changed to force it to
duke@1 207 // check for a safepoint condition between bytecodes.
duke@1 208 // 2. Running in native code
duke@1 209 // When returning from the native code, a Java thread must check
duke@1 210 // the safepoint _state to see if we must block. If the
duke@1 211 // VM thread sees a Java thread in native, it does
duke@1 212 // not wait for this thread to block. The order of the memory
duke@1 213 // writes and reads of both the safepoint state and the Java
duke@1 214 // threads state is critical. In order to guarantee that the
duke@1 215 // memory writes are serialized with respect to each other,
duke@1 216 // the VM thread issues a memory barrier instruction
duke@1 217 // (on MP systems). In order to avoid the overhead of issuing
duke@1 218 // a memory barrier for each Java thread making native calls, each Java
duke@1 219 // thread performs a write to a single memory page after changing
duke@1 220 // the thread state. The VM thread performs a sequence of
duke@1 221 // mprotect OS calls which forces all previous writes from all
duke@1 222 // Java threads to be serialized. This is done in the
duke@1 223 // os::serialize_thread_states() call. This has proven to be
duke@1 224 // much more efficient than executing a membar instruction
duke@1 225 // on every call to native code.
duke@1 226 // 3. Running compiled Code
duke@1 227 // Compiled code reads a global (Safepoint Polling) page that
duke@1 228 // is set to fault if we are trying to get to a safepoint.
duke@1 229 // 4. Blocked
duke@1 230 // A thread which is blocked will not be allowed to return from the
duke@1 231 // block condition until the safepoint operation is complete.
duke@1 232 // 5. In VM or Transitioning between states
duke@1 233 // If a Java thread is currently running in the VM or transitioning
duke@1 234 // between states, the safepointing code will wait for the thread to
duke@1 235 // block itself when it attempts transitions to a new state.
duke@1 236 //
dsimms@37176 237 {
egahlin@40664 238 EventSafepointStateSynchronization sync_event;
dsimms@37176 239 int initial_running = 0;
duke@1 240
dsimms@37176 241 _state = _synchronizing;
rehn@48069 242
rehn@48069 243 if (SafepointMechanism::uses_thread_local_poll()) {
rehn@48069 244 // Arming the per thread poll while having _state != _not_synchronized means safepointing
rehn@48069 245 log_trace(safepoint)("Setting thread local yield flag for threads");
mdoerr@51582 246 OrderAccess::storestore(); // storestore, global state -> local state
dcubed@48321 247 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur = jtiwh.next(); ) {
rehn@48069 248 // Make sure the threads start polling, it is time to yield.
mdoerr@51582 249 SafepointMechanism::arm_local_poll(cur);
rehn@48069 250 }
rehn@48069 251 }
rehn@48069 252 OrderAccess::fence(); // storestore|storeload, global state -> local state
duke@1 253
dsimms@37176 254 // Flush all thread states to memory
dsimms@37176 255 if (!UseMembar) {
dsimms@37176 256 os::serialize_thread_states();
dsimms@37176 257 }
duke@1 258
rehn@48069 259 if (SafepointMechanism::uses_global_page_poll()) {
rehn@48069 260 // Make interpreter safepoint aware
rehn@48069 261 Interpreter::notice_safepoints();
duke@1 262
hseigel@49600 263 // Make polling safepoint aware
hseigel@49600 264 guarantee (PageArmed == 0, "invariant") ;
hseigel@49600 265 PageArmed = 1 ;
hseigel@49600 266 os::make_polling_page_unreadable();
dsimms@37176 267 }
dsimms@37176 268
dsimms@37176 269 // Consider using active_processor_count() ... but that call is expensive.
dsimms@37176 270 int ncpus = os::processor_count() ;
dcubed@48321 271 unsigned int iterations = 0;
duke@1 272
dcubed@48321 273 {
dcubed@48321 274 JavaThreadIteratorWithHandle jtiwh;
duke@1 275 #ifdef ASSERT
dcubed@48321 276 for (; JavaThread *cur = jtiwh.next(); ) {
dcubed@48321 277 assert(cur->safepoint_state()->is_running(), "Illegal initial state");
dcubed@48321 278 // Clear the visited flag to ensure that the critical counts are collected properly.
dcubed@48321 279 cur->set_visited_for_critical_count(false);
dcubed@48321 280 }
duke@1 281 #endif // ASSERT
duke@1 282
dcubed@48321 283 if (SafepointTimeout)
dcubed@48321 284 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
duke@1 285
dcubed@48321 286 // Iterate through all threads until it have been determined how to stop them all at a safepoint
dcubed@48321 287 int steps = 0 ;
dcubed@48321 288 while(still_running > 0) {
dcubed@48321 289 jtiwh.rewind();
dcubed@48321 290 for (; JavaThread *cur = jtiwh.next(); ) {
dcubed@48321 291 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
dcubed@48321 292 ThreadSafepointState *cur_state = cur->safepoint_state();
dcubed@48321 293 if (cur_state->is_running()) {
dcubed@48321 294 cur_state->examine_state_of_thread();
dcubed@48321 295 if (!cur_state->is_running()) {
dcubed@48321 296 still_running--;
dcubed@48321 297 // consider adjusting steps downward:
dcubed@48321 298 // steps = 0
dcubed@48321 299 // steps -= NNN
dcubed@48321 300 // steps >>= 1
dcubed@48321 301 // steps = MIN(steps, 2000-100)
dcubed@48321 302 // if (iterations != 0) steps -= NNN
dcubed@48321 303 }
dcubed@48321 304 LogTarget(Trace, safepoint) lt;
dcubed@48321 305 if (lt.is_enabled()) {
dcubed@48321 306 ResourceMark rm;
dcubed@48321 307 LogStream ls(lt);
dcubed@48321 308 cur_state->print_on(&ls);
dcubed@48321 309 }
dsimms@37176 310 }
duke@1 311 }
dsimms@37176 312
dcubed@48321 313 if (iterations == 0) {
dcubed@48321 314 initial_running = still_running;
dcubed@48321 315 if (PrintSafepointStatistics) {
dcubed@48321 316 begin_statistics(nof_threads, still_running);
dcubed@48321 317 }
dsimms@37176 318 }
dsimms@37176 319
dcubed@48321 320 if (still_running > 0) {
dcubed@48321 321 // Check for if it takes to long
dcubed@48321 322 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
dcubed@48321 323 print_safepoint_timeout(_spinning_timeout);
dsimms@37176 324 }
dsimms@37176 325
dcubed@48321 326 // Spin to avoid context switching.
dcubed@48321 327 // There's a tension between allowing the mutators to run (and rendezvous)
dcubed@48321 328 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that
dcubed@48321 329 // a mutator might otherwise use profitably to reach a safepoint. Excessive
dcubed@48321 330 // spinning by the VM thread on a saturated system can increase rendezvous latency.
dcubed@48321 331 // Blocking or yielding incur their own penalties in the form of context switching
dcubed@48321 332 // and the resultant loss of $ residency.
dcubed@48321 333 //
dcubed@48321 334 // Further complicating matters is that yield() does not work as naively expected
dcubed@48321 335 // on many platforms -- yield() does not guarantee that any other ready threads
dcubed@48321 336 // will run. As such we revert to naked_short_sleep() after some number of iterations.
dcubed@48321 337 // nakes_short_sleep() is implemented as a short unconditional sleep.
dcubed@48321 338 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
dcubed@48321 339 // can actually increase the time it takes the VM thread to detect that a system-wide
dcubed@48321 340 // stop-the-world safepoint has been reached. In a pathological scenario such as that
dcubed@48321 341 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
dcubed@48321 342 // In that case the mutators will be stalled waiting for the safepoint to complete and the
dcubed@48321 343 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread
dcubed@48321 344 // will eventually wake up and detect that all mutators are safe, at which point
dcubed@48321 345 // we'll again make progress.
dcubed@48321 346 //
dcubed@48321 347 // Beware too that that the VMThread typically runs at elevated priority.
dcubed@48321 348 // Its default priority is higher than the default mutator priority.
dcubed@48321 349 // Obviously, this complicates spinning.
dcubed@48321 350 //
dcubed@48321 351 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
dcubed@48321 352 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
dcubed@48321 353 //
dcubed@48321 354 // See the comments in synchronizer.cpp for additional remarks on spinning.
dcubed@48321 355 //
dcubed@48321 356 // In the future we might:
dcubed@48321 357 // 1. Modify the safepoint scheme to avoid potentially unbounded spinning.
dcubed@48321 358 // This is tricky as the path used by a thread exiting the JVM (say on
dcubed@48321 359 // on JNI call-out) simply stores into its state field. The burden
dcubed@48321 360 // is placed on the VM thread, which must poll (spin).
dcubed@48321 361 // 2. Find something useful to do while spinning. If the safepoint is GC-related
dcubed@48321 362 // we might aggressively scan the stacks of threads that are already safe.
dcubed@48321 363 // 3. Use Solaris schedctl to examine the state of the still-running mutators.
dcubed@48321 364 // If all the mutators are ONPROC there's no reason to sleep or yield.
dcubed@48321 365 // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
dcubed@48321 366 // 5. Check system saturation. If the system is not fully saturated then
dcubed@48321 367 // simply spin and avoid sleep/yield.
dcubed@48321 368 // 6. As still-running mutators rendezvous they could unpark the sleeping
dcubed@48321 369 // VMthread. This works well for still-running mutators that become
dcubed@48321 370 // safe. The VMthread must still poll for mutators that call-out.
dcubed@48321 371 // 7. Drive the policy on time-since-begin instead of iterations.
dcubed@48321 372 // 8. Consider making the spin duration a function of the # of CPUs:
dcubed@48321 373 // Spin = (((ncpus-1) * M) + K) + F(still_running)
dcubed@48321 374 // Alternately, instead of counting iterations of the outer loop
dcubed@48321 375 // we could count the # of threads visited in the inner loop, above.
dcubed@48321 376 // 9. On windows consider using the return value from SwitchThreadTo()
dcubed@48321 377 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
dcubed@48321 378
hseigel@49600 379 if (int(iterations) == -1) { // overflow - something is wrong.
hseigel@49600 380 // We can only overflow here when we are using global
hseigel@49600 381 // polling pages. We keep this guarantee in its original
hseigel@49600 382 // form so that searches of the bug database for this
hseigel@49600 383 // failure mode find the right bugs.
hseigel@49600 384 guarantee (PageArmed == 0, "invariant");
dcubed@48321 385 }
dcubed@48321 386
dcubed@48321 387 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
dcubed@48321 388 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
dcubed@48321 389 ++steps ;
hseigel@49600 390 if (ncpus > 1 && steps < safepoint_spin_before_yield) {
dcubed@48321 391 SpinPause() ; // MP-Polite spin
dcubed@48321 392 } else
hseigel@49600 393 if (steps < _defer_thr_suspend_loop_count) {
dcubed@48321 394 os::naked_yield() ;
dcubed@48321 395 } else {
dcubed@48321 396 os::naked_short_sleep(1);
dcubed@48321 397 }
dcubed@48321 398
dcubed@48321 399 iterations ++ ;
dcubed@48321 400 }
dcubed@48321 401 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
dsimms@37176 402 }
dcubed@48321 403 } // ThreadsListHandle destroyed here.
dsimms@37176 404 assert(still_running == 0, "sanity check");
dsimms@37176 405
dsimms@37176 406 if (PrintSafepointStatistics) {
dsimms@37176 407 update_statistics_on_spin_end();
dsimms@37176 408 }
dsimms@37176 409 if (sync_event.should_commit()) {
egahlin@50662 410 post_safepoint_synchronize_event(&sync_event, initial_running, _waiting_to_block, iterations);
dsimms@37176 411 }
egahlin@50662 412 }
dsimms@37176 413
dsimms@37176 414 // wait until all threads are stopped
dsimms@37176 415 {
dsimms@37176 416 EventSafepointWaitBlocked wait_blocked_event;
dsimms@37176 417 int initial_waiting_to_block = _waiting_to_block;
dsimms@37176 418
dsimms@37176 419 while (_waiting_to_block > 0) {
dsimms@37176 420 log_debug(safepoint)("Waiting for %d thread(s) to block", _waiting_to_block);
dsimms@37176 421 if (!SafepointTimeout || timeout_error_printed) {
dsimms@37176 422 Safepoint_lock->wait(true); // true, means with no safepoint checks
dsimms@37176 423 } else {
dsimms@37176 424 // Compute remaining time
dsimms@37176 425 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
dsimms@37176 426
dsimms@37176 427 // If there is no remaining time, then there is an error
dsimms@37176 428 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
dsimms@37176 429 print_safepoint_timeout(_blocking_timeout);
rprotacio@33763 430 }
duke@1 431 }
duke@1 432 }
dsimms@37176 433 assert(_waiting_to_block == 0, "sanity check");
duke@1 434
dsimms@37176 435 #ifndef PRODUCT
dsimms@37176 436 if (SafepointTimeout) {
dsimms@37176 437 jlong current_time = os::javaTimeNanos();
dsimms@37176 438 if (safepoint_limit_time < current_time) {
dsimms@37176 439 tty->print_cr("# SafepointSynchronize: Finished after "
dsimms@37176 440 INT64_FORMAT_W(6) " ms",
jwilhelm@46630 441 (int64_t)((current_time - safepoint_limit_time) / MICROUNITS +
jwilhelm@46630 442 (jlong)SafepointTimeoutDelay));
duke@1 443 }
duke@1 444 }
duke@1 445 #endif
duke@1 446
dsimms@37176 447 assert((_safepoint_counter & 0x1) == 0, "must be even");
dsimms@37176 448 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
dsimms@37176 449 _safepoint_counter ++;
duke@1 450
dsimms@37176 451 // Record state
dsimms@37176 452 _state = _synchronized;
duke@1 453
dsimms@37176 454 OrderAccess::fence();
dsimms@37176 455 if (wait_blocked_event.should_commit()) {
egahlin@50662 456 post_safepoint_wait_blocked_event(&wait_blocked_event, initial_waiting_to_block);
dsimms@37176 457 }
egahlin@50662 458 }
duke@1 459
never@12108 460 #ifdef ASSERT
dcubed@48321 461 // Make sure all the threads were visited.
dcubed@48321 462 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur = jtiwh.next(); ) {
never@12108 463 assert(cur->was_visited_for_critical_count(), "missed a thread");
never@12108 464 }
never@12108 465 #endif // ASSERT
never@12108 466
never@11631 467 // Update the count of active JNI critical regions
david@35492 468 GCLocker::set_jni_lock_count(_current_jni_active_count);
never@11631 469
coleenp@48775 470 log_info(safepoint)("Entering safepoint region: %s", VMThread::vm_safepoint_description());
duke@1 471
duke@1 472 RuntimeService::record_safepoint_synchronized();
duke@1 473 if (PrintSafepointStatistics) {
duke@1 474 update_statistics_on_sync_end(os::javaTimeNanos());
duke@1 475 }
duke@1 476
duke@1 477 // Call stuff that needs to be run when a safepoint is just about to be completed
dsimms@37176 478 {
dsimms@37176 479 EventSafepointCleanup cleanup_event;
dsimms@37176 480 do_cleanup_tasks();
dsimms@37176 481 if (cleanup_event.should_commit()) {
egahlin@50662 482 post_safepoint_cleanup_event(&cleanup_event);
dsimms@37176 483 }
dsimms@37176 484 }
xlu@5042 485
xlu@5042 486 if (PrintSafepointStatistics) {
xlu@5042 487 // Record how much time spend on the above cleanup tasks
xlu@5042 488 update_statistics_on_cleanup_end(os::javaTimeNanos());
xlu@5042 489 }
egahlin@50662 490
dsimms@37176 491 if (begin_event.should_commit()) {
egahlin@50662 492 post_safepoint_begin_event(&begin_event, nof_threads, _current_jni_active_count);
dsimms@37176 493 }
duke@1 494 }
duke@1 495
duke@1 496 // Wake up all threads, so they are ready to resume execution after the safepoint
duke@1 497 // operation has been carried out
duke@1 498 void SafepointSynchronize::end() {
duke@1 499 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
duke@1 500 assert((_safepoint_counter & 0x1) == 1, "must be odd");
egahlin@50662 501 EventSafepointEnd event;
duke@1 502 _safepoint_counter ++;
duke@1 503 // memory fence isn't required here since an odd _safepoint_counter
duke@1 504 // value can do no harm and a fence is issued below anyway.
duke@1 505
duke@1 506 DEBUG_ONLY(Thread* myThread = Thread::current();)
duke@1 507 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
duke@1 508
duke@1 509 if (PrintSafepointStatistics) {
duke@1 510 end_statistics(os::javaTimeNanos());
duke@1 511 }
duke@1 512
dcubed@48321 513 {
dcubed@48321 514 JavaThreadIteratorWithHandle jtiwh;
duke@1 515 #ifdef ASSERT
dcubed@48321 516 // A pending_exception cannot be installed during a safepoint. The threads
dcubed@48321 517 // may install an async exception after they come back from a safepoint into
dcubed@48321 518 // pending_exception after they unblock. But that should happen later.
dcubed@48321 519 for (; JavaThread *cur = jtiwh.next(); ) {
dcubed@48321 520 assert (!(cur->has_pending_exception() &&
dcubed@48321 521 cur->safepoint_state()->is_at_poll_safepoint()),
dcubed@48321 522 "safepoint installed a pending exception");
dcubed@48321 523 }
duke@1 524 #endif // ASSERT
duke@1 525
dcubed@48321 526 if (PageArmed) {
dcubed@48321 527 assert(SafepointMechanism::uses_global_page_poll(), "sanity");
dcubed@48321 528 // Make polling safepoint aware
dcubed@48321 529 os::make_polling_page_readable();
dcubed@48321 530 PageArmed = 0 ;
duke@1 531 }
duke@1 532
dcubed@48321 533 if (SafepointMechanism::uses_global_page_poll()) {
dcubed@48321 534 // Remove safepoint check from interpreter
dcubed@48321 535 Interpreter::ignore_safepoints();
dcubed@48321 536 }
duke@1 537
dcubed@48321 538 {
dcubed@48321 539 MutexLocker mu(Safepoint_lock);
duke@1 540
dcubed@48321 541 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
dcubed@48321 542
dcubed@48321 543 if (SafepointMechanism::uses_thread_local_poll()) {
dcubed@48321 544 _state = _not_synchronized;
dcubed@48321 545 OrderAccess::storestore(); // global state -> local state
dcubed@48321 546 jtiwh.rewind();
dcubed@48321 547 for (; JavaThread *current = jtiwh.next(); ) {
dcubed@48321 548 ThreadSafepointState* cur_state = current->safepoint_state();
dcubed@48321 549 cur_state->restart(); // TSS _running
mdoerr@51582 550 SafepointMechanism::disarm_local_poll(current);
dcubed@48321 551 }
coleenp@48775 552 log_info(safepoint)("Leaving safepoint region");
dcubed@48321 553 } else {
dcubed@48321 554 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
dcubed@48321 555 // when they get restarted.
dcubed@48321 556 _state = _not_synchronized;
dcubed@48321 557 OrderAccess::fence();
dcubed@48321 558
coleenp@48775 559 log_info(safepoint)("Leaving safepoint region");
dcubed@48321 560
dcubed@48321 561 // Start suspended threads
dcubed@48321 562 jtiwh.rewind();
dcubed@48321 563 for (; JavaThread *current = jtiwh.next(); ) {
dcubed@48321 564 // A problem occurring on Solaris is when attempting to restart threads
dcubed@48321 565 // the first #cpus - 1 go well, but then the VMThread is preempted when we get
dcubed@48321 566 // to the next one (since it has been running the longest). We then have
dcubed@48321 567 // to wait for a cpu to become available before we can continue restarting
dcubed@48321 568 // threads.
dcubed@48321 569 // FIXME: This causes the performance of the VM to degrade when active and with
dcubed@48321 570 // large numbers of threads. Apparently this is due to the synchronous nature
dcubed@48321 571 // of suspending threads.
dcubed@48321 572 //
dcubed@48321 573 // TODO-FIXME: the comments above are vestigial and no longer apply.
dcubed@48321 574 // Furthermore, using solaris' schedctl in this particular context confers no benefit
dcubed@48321 575 if (VMThreadHintNoPreempt) {
dcubed@48321 576 os::hint_no_preempt();
dcubed@48321 577 }
dcubed@48321 578 ThreadSafepointState* cur_state = current->safepoint_state();
dcubed@48321 579 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
dcubed@48321 580 cur_state->restart();
dcubed@48321 581 assert(cur_state->is_running(), "safepoint state has not been reset");
dcubed@48321 582 }
dcubed@48321 583 }
dcubed@48321 584
dcubed@48321 585 RuntimeService::record_safepoint_end();
dcubed@48321 586
dcubed@48321 587 // Release threads lock, so threads can be created/destroyed again.
dcubed@48321 588 // It will also release all threads blocked in signal_thread_blocked.
dcubed@48321 589 Threads_lock->unlock();
dcubed@48321 590 }
dcubed@48321 591 } // ThreadsListHandle destroyed here.
dcubed@48321 592
eosterlund@47791 593 Universe::heap()->safepoint_synchronize_end();
jwilhelm@22551 594 // record this time so VMThread can keep track how much time has elapsed
xlu@5042 595 // since last safepoint.
xlu@5042 596 _end_of_last_safepoint = os::javaTimeMillis();
dsimms@37176 597 if (event.should_commit()) {
egahlin@50662 598 post_safepoint_end_event(&event);
dsimms@37176 599 }
duke@1 600 }
duke@1 601
duke@1 602 bool SafepointSynchronize::is_cleanup_needed() {
rehn@46541 603 // Need a safepoint if there are many monitors to deflate.
rehn@46541 604 if (ObjectSynchronizer::is_cleanup_needed()) return true;
duke@1 605 // Need a safepoint if some inline cache buffers is non-empty
duke@1 606 if (!InlineCacheBuffer::is_empty()) return true;
duke@1 607 return false;
duke@1 608 }
duke@1 609
rkennke@46702 610 class ParallelSPCleanupThreadClosure : public ThreadClosure {
rkennke@46702 611 private:
rkennke@46702 612 CodeBlobClosure* _nmethod_cl;
rkennke@46702 613 DeflateMonitorCounters* _counters;
rkennke@46702 614
rkennke@46702 615 public:
rkennke@46702 616 ParallelSPCleanupThreadClosure(DeflateMonitorCounters* counters) :
rkennke@46702 617 _counters(counters),
rkennke@46702 618 _nmethod_cl(NMethodSweeper::prepare_mark_active_nmethods()) {}
rkennke@46702 619
rkennke@46702 620 void do_thread(Thread* thread) {
rkennke@46702 621 ObjectSynchronizer::deflate_thread_local_monitors(thread, _counters);
rkennke@46702 622 if (_nmethod_cl != NULL && thread->is_Java_thread() &&
rkennke@46702 623 ! thread->is_Code_cache_sweeper_thread()) {
rkennke@46702 624 JavaThread* jt = (JavaThread*) thread;
rkennke@46702 625 jt->nmethods_do(_nmethod_cl);
rkennke@46702 626 }
rkennke@46702 627 }
rkennke@46702 628 };
rkennke@46702 629
rkennke@46702 630 class ParallelSPCleanupTask : public AbstractGangTask {
rkennke@46702 631 private:
rkennke@46702 632 SubTasksDone _subtasks;
rkennke@46702 633 ParallelSPCleanupThreadClosure _cleanup_threads_cl;
rkennke@46702 634 uint _num_workers;
rkennke@46702 635 DeflateMonitorCounters* _counters;
rkennke@46702 636 public:
rkennke@46702 637 ParallelSPCleanupTask(uint num_workers, DeflateMonitorCounters* counters) :
rkennke@46702 638 AbstractGangTask("Parallel Safepoint Cleanup"),
rkennke@46702 639 _cleanup_threads_cl(ParallelSPCleanupThreadClosure(counters)),
rkennke@46702 640 _num_workers(num_workers),
rkennke@46702 641 _subtasks(SubTasksDone(SafepointSynchronize::SAFEPOINT_CLEANUP_NUM_TASKS)),
rkennke@46702 642 _counters(counters) {}
rkennke@46702 643
rkennke@46702 644 void work(uint worker_id) {
rkennke@46702 645 // All threads deflate monitors and mark nmethods (if necessary).
rkennke@47792 646 Threads::possibly_parallel_threads_do(true, &_cleanup_threads_cl);
rkennke@46702 647
rkennke@46702 648 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_DEFLATE_MONITORS)) {
rkennke@46702 649 const char* name = "deflating idle monitors";
rkennke@46702 650 EventSafepointCleanupTask event;
rkennke@46702 651 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
rkennke@46702 652 ObjectSynchronizer::deflate_idle_monitors(_counters);
egahlin@50662 653 if (event.should_commit()) {
egahlin@50662 654 post_safepoint_cleanup_task_event(&event, name);
egahlin@50662 655 }
rkennke@46702 656 }
rkennke@46702 657
rkennke@46702 658 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_UPDATE_INLINE_CACHES)) {
rkennke@46702 659 const char* name = "updating inline caches";
rkennke@46702 660 EventSafepointCleanupTask event;
rkennke@46702 661 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
rkennke@46702 662 InlineCacheBuffer::update_inline_caches();
egahlin@50662 663 if (event.should_commit()) {
egahlin@50662 664 post_safepoint_cleanup_task_event(&event, name);
egahlin@50662 665 }
rkennke@46702 666 }
rkennke@46702 667
rkennke@46702 668 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_COMPILATION_POLICY)) {
rkennke@46702 669 const char* name = "compilation policy safepoint handler";
rkennke@46702 670 EventSafepointCleanupTask event;
rkennke@46702 671 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
rkennke@46702 672 CompilationPolicy::policy()->do_safepoint_work();
egahlin@50662 673 if (event.should_commit()) {
egahlin@50662 674 post_safepoint_cleanup_task_event(&event, name);
egahlin@50662 675 }
rkennke@46702 676 }
rkennke@46702 677
rkennke@46702 678 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_SYMBOL_TABLE_REHASH)) {
rkennke@46702 679 if (SymbolTable::needs_rehashing()) {
rkennke@46702 680 const char* name = "rehashing symbol table";
rkennke@46702 681 EventSafepointCleanupTask event;
rkennke@46702 682 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
rkennke@46702 683 SymbolTable::rehash_table();
egahlin@50662 684 if (event.should_commit()) {
egahlin@50662 685 post_safepoint_cleanup_task_event(&event, name);
egahlin@50662 686 }
rkennke@46702 687 }
rkennke@46702 688 }
rkennke@46702 689
rkennke@46702 690 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_STRING_TABLE_REHASH)) {
rkennke@46702 691 if (StringTable::needs_rehashing()) {
rkennke@46702 692 const char* name = "rehashing string table";
rkennke@46702 693 EventSafepointCleanupTask event;
rkennke@46702 694 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
rkennke@46702 695 StringTable::rehash_table();
egahlin@50662 696 if (event.should_commit()) {
egahlin@50662 697 post_safepoint_cleanup_task_event(&event, name);
egahlin@50662 698 }
rkennke@46702 699 }
rkennke@46702 700 }
rkennke@46702 701
rkennke@46702 702 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_CLD_PURGE)) {
rkennke@46702 703 // CMS delays purging the CLDG until the beginning of the next safepoint and to
rkennke@46702 704 // make sure concurrent sweep is done
rkennke@46702 705 const char* name = "purging class loader data graph";
rkennke@46702 706 EventSafepointCleanupTask event;
rkennke@46702 707 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
rkennke@46702 708 ClassLoaderDataGraph::purge_if_needed();
egahlin@50662 709 if (event.should_commit()) {
egahlin@50662 710 post_safepoint_cleanup_task_event(&event, name);
egahlin@50662 711 }
rkennke@46702 712 }
gziemski@47955 713
gziemski@47955 714 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_SYSTEM_DICTIONARY_RESIZE)) {
gziemski@47955 715 const char* name = "resizing system dictionaries";
gziemski@47955 716 EventSafepointCleanupTask event;
gziemski@47955 717 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
gziemski@47955 718 ClassLoaderDataGraph::resize_if_needed();
egahlin@50662 719 if (event.should_commit()) {
egahlin@50662 720 post_safepoint_cleanup_task_event(&event, name);
egahlin@50662 721 }
gziemski@47955 722 }
rkennke@46702 723 _subtasks.all_tasks_completed(_num_workers);
rkennke@46702 724 }
rkennke@46702 725 };
rkennke@46702 726
rkennke@46702 727 // Various cleaning tasks that should be done periodically at safepoints.
duke@1 728 void SafepointSynchronize::do_cleanup_tasks() {
rkennke@46702 729
rkennke@46702 730 TraceTime timer("safepoint cleanup tasks", TRACETIME_LOG(Info, safepoint, cleanup));
rkennke@46702 731
rkennke@46702 732 // Prepare for monitor deflation.
rkennke@46702 733 DeflateMonitorCounters deflate_counters;
rkennke@46702 734 ObjectSynchronizer::prepare_deflate_idle_monitors(&deflate_counters);
rkennke@46702 735
rkennke@46702 736 CollectedHeap* heap = Universe::heap();
rkennke@46702 737 assert(heap != NULL, "heap not initialized yet?");
rkennke@46702 738 WorkGang* cleanup_workers = heap->get_safepoint_workers();
rkennke@46702 739 if (cleanup_workers != NULL) {
rkennke@46702 740 // Parallel cleanup using GC provided thread pool.
rkennke@46702 741 uint num_cleanup_workers = cleanup_workers->active_workers();
rkennke@46702 742 ParallelSPCleanupTask cleanup(num_cleanup_workers, &deflate_counters);
rkennke@46702 743 StrongRootsScope srs(num_cleanup_workers);
rkennke@46702 744 cleanup_workers->run_task(&cleanup);
rkennke@46702 745 } else {
rkennke@46702 746 // Serial cleanup using VMThread.
rkennke@46702 747 ParallelSPCleanupTask cleanup(1, &deflate_counters);
rkennke@46702 748 StrongRootsScope srs(1);
rkennke@46702 749 cleanup.work(0);
duke@1 750 }
duke@1 751
rkennke@46702 752 // Finish monitor deflation.
rkennke@46702 753 ObjectSynchronizer::finish_deflate_idle_monitors(&deflate_counters);
duke@1 754 }
duke@1 755
duke@1 756
duke@1 757 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
duke@1 758 switch(state) {
duke@1 759 case _thread_in_native:
duke@1 760 // native threads are safe if they have no java stack or have walkable stack
duke@1 761 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
duke@1 762
duke@1 763 // blocked threads should have already have walkable stack
duke@1 764 case _thread_blocked:
duke@1 765 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
duke@1 766 return true;
duke@1 767
duke@1 768 default:
duke@1 769 return false;
duke@1 770 }
duke@1 771 }
duke@1 772
duke@1 773
never@11637 774 // See if the thread is running inside a lazy critical native and
never@11637 775 // update the thread critical count if so. Also set a suspend flag to
never@11637 776 // cause the native wrapper to return into the JVM to do the unlock
never@11637 777 // once the native finishes.
never@11637 778 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
never@11637 779 if (state == _thread_in_native &&
never@11637 780 thread->has_last_Java_frame() &&
never@11637 781 thread->frame_anchor()->walkable()) {
never@11637 782 // This thread might be in a critical native nmethod so look at
never@11637 783 // the top of the stack and increment the critical count if it
never@11637 784 // is.
never@11637 785 frame wrapper_frame = thread->last_frame();
never@11637 786 CodeBlob* stub_cb = wrapper_frame.cb();
never@11637 787 if (stub_cb != NULL &&
never@11637 788 stub_cb->is_nmethod() &&
never@11637 789 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
never@11637 790 // A thread could potentially be in a critical native across
never@11637 791 // more than one safepoint, so only update the critical state on
never@11637 792 // the first one. When it returns it will perform the unlock.
never@11637 793 if (!thread->do_critical_native_unlock()) {
never@11637 794 #ifdef ASSERT
never@11637 795 if (!thread->in_critical()) {
david@35492 796 GCLocker::increment_debug_jni_lock_count();
never@11637 797 }
never@11637 798 #endif
never@11637 799 thread->enter_critical();
never@11637 800 // Make sure the native wrapper calls back on return to
never@11637 801 // perform the needed critical unlock.
never@11637 802 thread->set_critical_native_unlock();
never@11637 803 }
never@11637 804 }
never@11637 805 }
never@11637 806 }
never@11637 807
never@11637 808
never@11637 809
duke@1 810 // -------------------------------------------------------------------------------------------------------
duke@1 811 // Implementation of Safepoint callback point
duke@1 812
duke@1 813 void SafepointSynchronize::block(JavaThread *thread) {
duke@1 814 assert(thread != NULL, "thread must be set");
duke@1 815 assert(thread->is_Java_thread(), "not a Java thread");
duke@1 816
duke@1 817 // Threads shouldn't block if they are in the middle of printing, but...
duke@1 818 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
duke@1 819
duke@1 820 // Only bail from the block() call if the thread is gone from the
duke@1 821 // thread list; starting to exit should still block.
duke@1 822 if (thread->is_terminated()) {
duke@1 823 // block current thread if we come here from native code when VM is gone
duke@1 824 thread->block_if_vm_exited();
duke@1 825
duke@1 826 // otherwise do nothing
duke@1 827 return;
duke@1 828 }
duke@1 829
duke@1 830 JavaThreadState state = thread->thread_state();
duke@1 831 thread->frame_anchor()->make_walkable(thread);
duke@1 832
duke@1 833 // Check that we have a valid thread_state at this point
duke@1 834 switch(state) {
duke@1 835 case _thread_in_vm_trans:
duke@1 836 case _thread_in_Java: // From compiled code
duke@1 837
duke@1 838 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
duke@1 839 // we pretend we are still in the VM.
duke@1 840 thread->set_thread_state(_thread_in_vm);
duke@1 841
duke@1 842 if (is_synchronizing()) {
duke@1 843 Atomic::inc (&TryingToBlock) ;
duke@1 844 }
duke@1 845
duke@1 846 // We will always be holding the Safepoint_lock when we are examine the state
duke@1 847 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
duke@1 848 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
duke@1 849 Safepoint_lock->lock_without_safepoint_check();
duke@1 850 if (is_synchronizing()) {
duke@1 851 // Decrement the number of threads to wait for and signal vm thread
duke@1 852 assert(_waiting_to_block > 0, "sanity check");
duke@1 853 _waiting_to_block--;
duke@1 854 thread->safepoint_state()->set_has_called_back(true);
duke@1 855
never@12108 856 DEBUG_ONLY(thread->set_visited_for_critical_count(true));
never@11631 857 if (thread->in_critical()) {
never@11631 858 // Notice that this thread is in a critical section
never@11631 859 increment_jni_active_count();
never@11631 860 }
never@11631 861
duke@1 862 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
duke@1 863 if (_waiting_to_block == 0) {
duke@1 864 Safepoint_lock->notify_all();
duke@1 865 }
duke@1 866 }
duke@1 867
duke@1 868 // We transition the thread to state _thread_blocked here, but
duke@1 869 // we can't do our usual check for external suspension and then
duke@1 870 // self-suspend after the lock_without_safepoint_check() call
duke@1 871 // below because we are often called during transitions while
duke@1 872 // we hold different locks. That would leave us suspended while
duke@1 873 // holding a resource which results in deadlocks.
duke@1 874 thread->set_thread_state(_thread_blocked);
duke@1 875 Safepoint_lock->unlock();
duke@1 876
duke@1 877 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
duke@1 878 // the entire safepoint, the threads will all line up here during the safepoint.
duke@1 879 Threads_lock->lock_without_safepoint_check();
duke@1 880 // restore original state. This is important if the thread comes from compiled code, so it
duke@1 881 // will continue to execute with the _thread_in_Java state.
duke@1 882 thread->set_thread_state(state);
duke@1 883 Threads_lock->unlock();
duke@1 884 break;
duke@1 885
duke@1 886 case _thread_in_native_trans:
duke@1 887 case _thread_blocked_trans:
duke@1 888 case _thread_new_trans:
duke@1 889 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
duke@1 890 thread->print_thread_state();
duke@1 891 fatal("Deadlock in safepoint code. "
duke@1 892 "Should have called back to the VM before blocking.");
duke@1 893 }
duke@1 894
duke@1 895 // We transition the thread to state _thread_blocked here, but
duke@1 896 // we can't do our usual check for external suspension and then
duke@1 897 // self-suspend after the lock_without_safepoint_check() call
duke@1 898 // below because we are often called during transitions while
duke@1 899 // we hold different locks. That would leave us suspended while
duke@1 900 // holding a resource which results in deadlocks.
duke@1 901 thread->set_thread_state(_thread_blocked);
duke@1 902
duke@1 903 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
duke@1 904 // the safepoint code might still be waiting for it to block. We need to change the state here,
duke@1 905 // so it can see that it is at a safepoint.
duke@1 906
duke@1 907 // Block until the safepoint operation is completed.
duke@1 908 Threads_lock->lock_without_safepoint_check();
duke@1 909
duke@1 910 // Restore state
duke@1 911 thread->set_thread_state(state);
duke@1 912
duke@1 913 Threads_lock->unlock();
duke@1 914 break;
duke@1 915
duke@1 916 default:
david@33105 917 fatal("Illegal threadstate encountered: %d", state);
duke@1 918 }
duke@1 919
duke@1 920 // Check for pending. async. exceptions or suspends - except if the
duke@1 921 // thread was blocked inside the VM. has_special_runtime_exit_condition()
duke@1 922 // is called last since it grabs a lock and we only want to do that when
duke@1 923 // we must.
duke@1 924 //
duke@1 925 // Note: we never deliver an async exception at a polling point as the
duke@1 926 // compiler may not have an exception handler for it. The polling
duke@1 927 // code will notice the async and deoptimize and the exception will
duke@1 928 // be delivered. (Polling at a return point is ok though). Sure is
duke@1 929 // a lot of bother for a deprecated feature...
duke@1 930 //
duke@1 931 // We don't deliver an async exception if the thread state is
duke@1 932 // _thread_in_native_trans so JNI functions won't be called with
duke@1 933 // a surprising pending exception. If the thread state is going back to java,
duke@1 934 // async exception is checked in check_special_condition_for_native_trans().
duke@1 935
duke@1 936 if (state != _thread_blocked_trans &&
duke@1 937 state != _thread_in_vm_trans &&
duke@1 938 thread->has_special_runtime_exit_condition()) {
duke@1 939 thread->handle_special_runtime_exit_condition(
duke@1 940 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
duke@1 941 }
duke@1 942 }
duke@1 943
duke@1 944 // ------------------------------------------------------------------------------------------------------
duke@1 945 // Exception handlers
duke@1 946
duke@1 947
duke@1 948 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
duke@1 949 assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
duke@1 950 assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
rehn@48069 951 if (!ThreadLocalHandshakes) {
rehn@48069 952 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
rehn@48069 953 }
duke@1 954
duke@1 955 if (PrintSafepointStatistics) {
duke@1 956 inc_page_trap_count();
duke@1 957 }
duke@1 958
duke@1 959 ThreadSafepointState* state = thread->safepoint_state();
duke@1 960
duke@1 961 state->handle_polling_page_exception();
duke@1 962 }
duke@1 963
duke@1 964
duke@1 965 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
duke@1 966 if (!timeout_error_printed) {
duke@1 967 timeout_error_printed = true;
jwilhelm@22551 968 // Print out the thread info which didn't reach the safepoint for debugging
duke@1 969 // purposes (useful when there are lots of threads in the debugger).
drchase@24424 970 tty->cr();
duke@1 971 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
duke@1 972 if (reason == _spinning_timeout) {
duke@1 973 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
duke@1 974 } else if (reason == _blocking_timeout) {
duke@1 975 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
duke@1 976 }
duke@1 977
duke@1 978 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
duke@1 979 ThreadSafepointState *cur_state;
duke@1 980 ResourceMark rm;
dcubed@48321 981 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur_thread = jtiwh.next(); ) {
duke@1 982 cur_state = cur_thread->safepoint_state();
duke@1 983
duke@1 984 if (cur_thread->thread_state() != _thread_blocked &&
dcubed@48321 985 ((reason == _spinning_timeout && cur_state->is_running()) ||
duke@1 986 (reason == _blocking_timeout && !cur_state->has_called_back()))) {
duke@1 987 tty->print("# ");
duke@1 988 cur_thread->print();
drchase@24424 989 tty->cr();
duke@1 990 }
duke@1 991 }
duke@1 992 tty->print_cr("# SafepointSynchronize::begin: (End of list)");
duke@1 993 }
duke@1 994
duke@1 995 // To debug the long safepoint, specify both DieOnSafepointTimeout &
duke@1 996 // ShowMessageBoxOnError.
duke@1 997 if (DieOnSafepointTimeout) {
david@33105 998 fatal("Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
rehn@46496 999 SafepointTimeoutDelay, VMThread::vm_safepoint_description());
duke@1 1000 }
duke@1 1001 }
duke@1 1002
duke@1 1003
duke@1 1004 // -------------------------------------------------------------------------------------------------------
duke@1 1005 // Implementation of ThreadSafepointState
duke@1 1006
duke@1 1007 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
duke@1 1008 _thread = thread;
duke@1 1009 _type = _running;
duke@1 1010 _has_called_back = false;
duke@1 1011 _at_poll_safepoint = false;
duke@1 1012 }
duke@1 1013
duke@1 1014 void ThreadSafepointState::create(JavaThread *thread) {
duke@1 1015 ThreadSafepointState *state = new ThreadSafepointState(thread);
duke@1 1016 thread->set_safepoint_state(state);
duke@1 1017 }
duke@1 1018
duke@1 1019 void ThreadSafepointState::destroy(JavaThread *thread) {
duke@1 1020 if (thread->safepoint_state()) {
duke@1 1021 delete(thread->safepoint_state());
duke@1 1022 thread->set_safepoint_state(NULL);
duke@1 1023 }
duke@1 1024 }
duke@1 1025
duke@1 1026 void ThreadSafepointState::examine_state_of_thread() {
duke@1 1027 assert(is_running(), "better be running or just have hit safepoint poll");
duke@1 1028
duke@1 1029 JavaThreadState state = _thread->thread_state();
duke@1 1030
never@6269 1031 // Save the state at the start of safepoint processing.
never@6269 1032 _orig_thread_state = state;
never@6269 1033
duke@1 1034 // Check for a thread that is suspended. Note that thread resume tries
duke@1 1035 // to grab the Threads_lock which we own here, so a thread cannot be
duke@1 1036 // resumed during safepoint synchronization.
duke@1 1037
dcubed@3826 1038 // We check to see if this thread is suspended without locking to
dcubed@3826 1039 // avoid deadlocking with a third thread that is waiting for this
dcubed@3826 1040 // thread to be suspended. The third thread can notice the safepoint
dcubed@3826 1041 // that we're trying to start at the beginning of its SR_lock->wait()
dcubed@3826 1042 // call. If that happens, then the third thread will block on the
dcubed@3826 1043 // safepoint while still holding the underlying SR_lock. We won't be
dcubed@3826 1044 // able to get the SR_lock and we'll deadlock.
dcubed@3826 1045 //
dcubed@3826 1046 // We don't need to grab the SR_lock here for two reasons:
dcubed@3826 1047 // 1) The suspend flags are both volatile and are set with an
dcubed@3826 1048 // Atomic::cmpxchg() call so we should see the suspended
dcubed@3826 1049 // state right away.
dcubed@3826 1050 // 2) We're being called from the safepoint polling loop; if
dcubed@3826 1051 // we don't see the suspended state on this iteration, then
dcubed@3826 1052 // we'll come around again.
dcubed@3826 1053 //
dcubed@3826 1054 bool is_suspended = _thread->is_ext_suspended();
duke@1 1055 if (is_suspended) {
duke@1 1056 roll_forward(_at_safepoint);
duke@1 1057 return;
duke@1 1058 }
duke@1 1059
duke@1 1060 // Some JavaThread states have an initial safepoint state of
duke@1 1061 // running, but are actually at a safepoint. We will happily
duke@1 1062 // agree and update the safepoint state here.
duke@1 1063 if (SafepointSynchronize::safepoint_safe(_thread, state)) {
never@12108 1064 SafepointSynchronize::check_for_lazy_critical_native(_thread, state);
never@11631 1065 roll_forward(_at_safepoint);
never@11631 1066 return;
duke@1 1067 }
duke@1 1068
duke@1 1069 if (state == _thread_in_vm) {
duke@1 1070 roll_forward(_call_back);
duke@1 1071 return;
duke@1 1072 }
duke@1 1073
duke@1 1074 // All other thread states will continue to run until they
duke@1 1075 // transition and self-block in state _blocked
duke@1 1076 // Safepoint polling in compiled code causes the Java threads to do the same.
duke@1 1077 // Note: new threads may require a malloc so they must be allowed to finish
duke@1 1078
duke@1 1079 assert(is_running(), "examine_state_of_thread on non-running thread");
duke@1 1080 return;
duke@1 1081 }
duke@1 1082
duke@1 1083 // Returns true is thread could not be rolled forward at present position.
duke@1 1084 void ThreadSafepointState::roll_forward(suspend_type type) {
duke@1 1085 _type = type;
duke@1 1086
duke@1 1087 switch(_type) {
duke@1 1088 case _at_safepoint:
duke@1 1089 SafepointSynchronize::signal_thread_at_safepoint();
never@12108 1090 DEBUG_ONLY(_thread->set_visited_for_critical_count(true));
never@12108 1091 if (_thread->in_critical()) {
never@12108 1092 // Notice that this thread is in a critical section
never@12108 1093 SafepointSynchronize::increment_jni_active_count();
never@12108 1094 }
duke@1 1095 break;
duke@1 1096
duke@1 1097 case _call_back:
duke@1 1098 set_has_called_back(false);
duke@1 1099 break;
duke@1 1100
duke@1 1101 case _running:
duke@1 1102 default:
duke@1 1103 ShouldNotReachHere();
duke@1 1104 }
duke@1 1105 }
duke@1 1106
duke@1 1107 void ThreadSafepointState::restart() {
duke@1 1108 switch(type()) {
duke@1 1109 case _at_safepoint:
duke@1 1110 case _call_back:
duke@1 1111 break;
duke@1 1112
duke@1 1113 case _running:
duke@1 1114 default:
bpittore@31592 1115 tty->print_cr("restart thread " INTPTR_FORMAT " with state %d",
david@33148 1116 p2i(_thread), _type);
duke@1 1117 _thread->print();
duke@1 1118 ShouldNotReachHere();
duke@1 1119 }
duke@1 1120 _type = _running;
duke@1 1121 set_has_called_back(false);
duke@1 1122 }
duke@1 1123
duke@1 1124
duke@1 1125 void ThreadSafepointState::print_on(outputStream *st) const {
goetz@33589 1126 const char *s = NULL;
duke@1 1127
duke@1 1128 switch(_type) {
duke@1 1129 case _running : s = "_running"; break;
duke@1 1130 case _at_safepoint : s = "_at_safepoint"; break;
duke@1 1131 case _call_back : s = "_call_back"; break;
duke@1 1132 default:
duke@1 1133 ShouldNotReachHere();
duke@1 1134 }
duke@1 1135
duke@1 1136 st->print_cr("Thread: " INTPTR_FORMAT
duke@1 1137 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
david@33148 1138 p2i(_thread), _thread->osthread()->thread_id(), s, _has_called_back,
duke@1 1139 _at_poll_safepoint);
duke@1 1140
duke@1 1141 _thread->print_thread_state_on(st);
duke@1 1142 }
duke@1 1143
duke@1 1144 // ---------------------------------------------------------------------------------------------------------------------
duke@1 1145
rehn@48069 1146 // Block the thread at poll or poll return for safepoint/handshake.
duke@1 1147 void ThreadSafepointState::handle_polling_page_exception() {
duke@1 1148
duke@1 1149 // Check state. block() will set thread state to thread_in_vm which will
duke@1 1150 // cause the safepoint state _type to become _call_back.
rehn@48069 1151 suspend_type t = type();
rehn@48069 1152 assert(!SafepointMechanism::uses_global_page_poll() || t == ThreadSafepointState::_running,
rehn@48069 1153 "polling page exception on thread not running state: %u", uint(t));
duke@1 1154
duke@1 1155 // Step 1: Find the nmethod from the return address
duke@1 1156 address real_return_addr = thread()->saved_exception_pc();
duke@1 1157
duke@1 1158 CodeBlob *cb = CodeCache::find_blob(real_return_addr);
rbackman@38133 1159 assert(cb != NULL && cb->is_compiled(), "return address should be in nmethod");
rbackman@38133 1160 CompiledMethod* nm = (CompiledMethod*)cb;
duke@1 1161
duke@1 1162 // Find frame of caller
duke@1 1163 frame stub_fr = thread()->last_frame();
duke@1 1164 CodeBlob* stub_cb = stub_fr.cb();
duke@1 1165 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
duke@1 1166 RegisterMap map(thread(), true);
duke@1 1167 frame caller_fr = stub_fr.sender(&map);
duke@1 1168
duke@1 1169 // Should only be poll_return or poll
duke@1 1170 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
duke@1 1171
duke@1 1172 // This is a poll immediately before a return. The exception handling code
duke@1 1173 // has already had the effect of causing the return to occur, so the execution
duke@1 1174 // will continue immediately after the call. In addition, the oopmap at the
duke@1 1175 // return point does not mark the return value as an oop (if it is), so
duke@1 1176 // it needs a handle here to be updated.
duke@1 1177 if( nm->is_at_poll_return(real_return_addr) ) {
duke@1 1178 // See if return type is an oop.
duke@1 1179 bool return_oop = nm->method()->is_returning_oop();
duke@1 1180 Handle return_value;
duke@1 1181 if (return_oop) {
duke@1 1182 // The oop result has been saved on the stack together with all
duke@1 1183 // the other registers. In order to preserve it over GCs we need
duke@1 1184 // to keep it in a handle.
duke@1 1185 oop result = caller_fr.saved_oop_result(&map);
coleenp@46968 1186 assert(oopDesc::is_oop_or_null(result), "must be oop");
duke@1 1187 return_value = Handle(thread(), result);
duke@1 1188 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
duke@1 1189 }
duke@1 1190
duke@1 1191 // Block the thread
rehn@48069 1192 SafepointMechanism::block_if_requested(thread());
duke@1 1193
duke@1 1194 // restore oop result, if any
duke@1 1195 if (return_oop) {
duke@1 1196 caller_fr.set_saved_oop_result(&map, return_value());
duke@1 1197 }
duke@1 1198 }
duke@1 1199
duke@1 1200 // This is a safepoint poll. Verify the return address and block.
duke@1 1201 else {
duke@1 1202 set_at_poll_safepoint(true);
duke@1 1203
duke@1 1204 // verify the blob built the "return address" correctly
duke@1 1205 assert(real_return_addr == caller_fr.pc(), "must match");
duke@1 1206
duke@1 1207 // Block the thread
rehn@48069 1208 SafepointMechanism::block_if_requested(thread());
duke@1 1209 set_at_poll_safepoint(false);
duke@1 1210
duke@1 1211 // If we have a pending async exception deoptimize the frame
duke@1 1212 // as otherwise we may never deliver it.
duke@1 1213 if (thread()->has_async_condition()) {
duke@1 1214 ThreadInVMfromJavaNoAsyncException __tiv(thread());
never@7106 1215 Deoptimization::deoptimize_frame(thread(), caller_fr.id());
duke@1 1216 }
duke@1 1217
duke@1 1218 // If an exception has been installed we must check for a pending deoptimization
duke@1 1219 // Deoptimize frame if exception has been thrown.
duke@1 1220
duke@1 1221 if (thread()->has_pending_exception() ) {
duke@1 1222 RegisterMap map(thread(), true);
duke@1 1223 frame caller_fr = stub_fr.sender(&map);
duke@1 1224 if (caller_fr.is_deoptimized_frame()) {
duke@1 1225 // The exception patch will destroy registers that are still
duke@1 1226 // live and will be needed during deoptimization. Defer the
jwilhelm@22551 1227 // Async exception should have deferred the exception until the
duke@1 1228 // next safepoint which will be detected when we get into
duke@1 1229 // the interpreter so if we have an exception now things
duke@1 1230 // are messed up.
duke@1 1231
duke@1 1232 fatal("Exception installed and deoptimization is pending");
duke@1 1233 }
duke@1 1234 }
duke@1 1235 }
duke@1 1236 }
duke@1 1237
duke@1 1238
duke@1 1239 //
duke@1 1240 // Statistics & Instrumentations
duke@1 1241 //
duke@1 1242 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL;
xlu@5042 1243 jlong SafepointSynchronize::_safepoint_begin_time = 0;
duke@1 1244 int SafepointSynchronize::_cur_stat_index = 0;
duke@1 1245 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
duke@1 1246 julong SafepointSynchronize::_coalesced_vmop_count = 0;
duke@1 1247 jlong SafepointSynchronize::_max_sync_time = 0;
xlu@5042 1248 jlong SafepointSynchronize::_max_vmop_time = 0;
xlu@5042 1249 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f;
duke@1 1250
xlu@5042 1251 static jlong cleanup_end_time = 0;
duke@1 1252 static bool init_done = false;
duke@1 1253
xlu@5042 1254 // Helper method to print the header.
xlu@5042 1255 static void print_header() {
shade@46473 1256 // The number of spaces is significant here, and should match the format
shade@46473 1257 // specifiers in print_statistics().
shade@46473 1258
shade@46473 1259 tty->print(" vmop "
shade@46473 1260 "[ threads: total initially_running wait_to_block ]"
shade@46473 1261 "[ time: spin block sync cleanup vmop ] ");
xlu@5042 1262
xlu@5042 1263 tty->print_cr("page_trap_count");
xlu@5042 1264 }
xlu@5042 1265
duke@1 1266 void SafepointSynchronize::deferred_initialize_stat() {
duke@1 1267 if (init_done) return;
duke@1 1268
duke@1 1269 // If PrintSafepointStatisticsTimeout is specified, the statistics data will
duke@1 1270 // be printed right away, in which case, _safepoint_stats will regress to
duke@1 1271 // a single element array. Otherwise, it is a circular ring buffer with default
duke@1 1272 // size of PrintSafepointStatisticsCount.
duke@1 1273 int stats_array_size;
duke@1 1274 if (PrintSafepointStatisticsTimeout > 0) {
duke@1 1275 stats_array_size = 1;
duke@1 1276 PrintSafepointStatistics = true;
duke@1 1277 } else {
duke@1 1278 stats_array_size = PrintSafepointStatisticsCount;
duke@1 1279 }
duke@1 1280 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
zgu@13195 1281 * sizeof(SafepointStats), mtInternal);
duke@1 1282 guarantee(_safepoint_stats != NULL,
duke@1 1283 "not enough memory for safepoint instrumentation data");
duke@1 1284
duke@1 1285 init_done = true;
duke@1 1286 }
duke@1 1287
duke@1 1288 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
xlu@4006 1289 assert(init_done, "safepoint statistics array hasn't been initialized");
duke@1 1290 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
duke@1 1291
xlu@5042 1292 spstat->_time_stamp = _ts_of_current_safepoint;
xlu@5042 1293
duke@1 1294 VM_Operation *op = VMThread::vm_operation();
duke@1 1295 spstat->_vmop_type = (op != NULL ? op->type() : -1);
duke@1 1296 if (op != NULL) {
duke@1 1297 _safepoint_reasons[spstat->_vmop_type]++;
duke@1 1298 }
duke@1 1299
duke@1 1300 spstat->_nof_total_threads = nof_threads;
duke@1 1301 spstat->_nof_initial_running_threads = nof_running;
duke@1 1302 spstat->_nof_threads_hit_page_trap = 0;
duke@1 1303
duke@1 1304 // Records the start time of spinning. The real time spent on spinning
duke@1 1305 // will be adjusted when spin is done. Same trick is applied for time
duke@1 1306 // spent on waiting for threads to block.
duke@1 1307 if (nof_running != 0) {
duke@1 1308 spstat->_time_to_spin = os::javaTimeNanos();
duke@1 1309 } else {
duke@1 1310 spstat->_time_to_spin = 0;
duke@1 1311 }
duke@1 1312 }
duke@1 1313
duke@1 1314 void SafepointSynchronize::update_statistics_on_spin_end() {
duke@1 1315 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
duke@1 1316
duke@1 1317 jlong cur_time = os::javaTimeNanos();
duke@1 1318
duke@1 1319 spstat->_nof_threads_wait_to_block = _waiting_to_block;
duke@1 1320 if (spstat->_nof_initial_running_threads != 0) {
duke@1 1321 spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
duke@1 1322 }
duke@1 1323
duke@1 1324 // Records the start time of waiting for to block. Updated when block is done.
duke@1 1325 if (_waiting_to_block != 0) {
duke@1 1326 spstat->_time_to_wait_to_block = cur_time;
duke@1 1327 } else {
duke@1 1328 spstat->_time_to_wait_to_block = 0;
duke@1 1329 }
duke@1 1330 }
duke@1 1331
duke@1 1332 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
duke@1 1333 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
duke@1 1334
duke@1 1335 if (spstat->_nof_threads_wait_to_block != 0) {
duke@1 1336 spstat->_time_to_wait_to_block = end_time -
duke@1 1337 spstat->_time_to_wait_to_block;
duke@1 1338 }
duke@1 1339
duke@1 1340 // Records the end time of sync which will be used to calculate the total
duke@1 1341 // vm operation time. Again, the real time spending in syncing will be deducted
duke@1 1342 // from the start of the sync time later when end_statistics is called.
xlu@5042 1343 spstat->_time_to_sync = end_time - _safepoint_begin_time;
duke@1 1344 if (spstat->_time_to_sync > _max_sync_time) {
duke@1 1345 _max_sync_time = spstat->_time_to_sync;
duke@1 1346 }
xlu@5042 1347
xlu@5042 1348 spstat->_time_to_do_cleanups = end_time;
xlu@5042 1349 }
xlu@5042 1350
xlu@5042 1351 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
xlu@5042 1352 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
xlu@5042 1353
xlu@5042 1354 // Record how long spent in cleanup tasks.
xlu@5042 1355 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
xlu@5042 1356
xlu@5042 1357 cleanup_end_time = end_time;
duke@1 1358 }
duke@1 1359
duke@1 1360 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
duke@1 1361 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
duke@1 1362
duke@1 1363 // Update the vm operation time.
xlu@5042 1364 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time;
xlu@5042 1365 if (spstat->_time_to_exec_vmop > _max_vmop_time) {
xlu@5042 1366 _max_vmop_time = spstat->_time_to_exec_vmop;
xlu@5042 1367 }
duke@1 1368 // Only the sync time longer than the specified
duke@1 1369 // PrintSafepointStatisticsTimeout will be printed out right away.
duke@1 1370 // By default, it is -1 meaning all samples will be put into the list.
duke@1 1371 if ( PrintSafepointStatisticsTimeout > 0) {
gziemski@33222 1372 if (spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
duke@1 1373 print_statistics();
duke@1 1374 }
duke@1 1375 } else {
duke@1 1376 // The safepoint statistics will be printed out when the _safepoin_stats
duke@1 1377 // array fills up.
xlu@5042 1378 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) {
duke@1 1379 print_statistics();
duke@1 1380 _cur_stat_index = 0;
xlu@5042 1381 } else {
xlu@5042 1382 _cur_stat_index++;
duke@1 1383 }
duke@1 1384 }
duke@1 1385 }
duke@1 1386
duke@1 1387 void SafepointSynchronize::print_statistics() {
xlu@5042 1388 for (int index = 0; index <= _cur_stat_index; index++) {
xlu@5042 1389 if (index % 30 == 0) {
xlu@5042 1390 print_header();
xlu@5042 1391 }
shade@46473 1392 SafepointStats* sstats = &_safepoint_stats[index];
shade@46473 1393 tty->print("%8.3f: ", sstats->_time_stamp);
shade@46473 1394 tty->print("%-30s [ "
shade@46473 1395 INT32_FORMAT_W(8) " " INT32_FORMAT_W(17) " " INT32_FORMAT_W(13) " "
shade@46473 1396 "]",
shade@46473 1397 (sstats->_vmop_type == -1 ? "no vm operation" : VM_Operation::name(sstats->_vmop_type)),
duke@1 1398 sstats->_nof_total_threads,
duke@1 1399 sstats->_nof_initial_running_threads,
duke@1 1400 sstats->_nof_threads_wait_to_block);
duke@1 1401 // "/ MICROUNITS " is to convert the unit from nanos to millis.
shade@46473 1402 tty->print("[ "
shade@46473 1403 INT64_FORMAT_W(7) " " INT64_FORMAT_W(7) " "
shade@46473 1404 INT64_FORMAT_W(7) " " INT64_FORMAT_W(7) " "
shade@46473 1405 INT64_FORMAT_W(7) " ] ",
jwilhelm@46630 1406 (int64_t)(sstats->_time_to_spin / MICROUNITS),
jwilhelm@46630 1407 (int64_t)(sstats->_time_to_wait_to_block / MICROUNITS),
jwilhelm@46630 1408 (int64_t)(sstats->_time_to_sync / MICROUNITS),
jwilhelm@46630 1409 (int64_t)(sstats->_time_to_do_cleanups / MICROUNITS),
jwilhelm@46630 1410 (int64_t)(sstats->_time_to_exec_vmop / MICROUNITS));
duke@1 1411
shade@46473 1412 tty->print_cr(INT32_FORMAT_W(15) " ", sstats->_nof_threads_hit_page_trap);
duke@1 1413 }
duke@1 1414 }
duke@1 1415
duke@1 1416 // This method will be called when VM exits. It will first call
duke@1 1417 // print_statistics to print out the rest of the sampling. Then
duke@1 1418 // it tries to summarize the sampling.
duke@1 1419 void SafepointSynchronize::print_stat_on_exit() {
duke@1 1420 if (_safepoint_stats == NULL) return;
duke@1 1421
duke@1 1422 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
duke@1 1423
duke@1 1424 // During VM exit, end_statistics may not get called and in that
duke@1 1425 // case, if the sync time is less than PrintSafepointStatisticsTimeout,
duke@1 1426 // don't print it out.
duke@1 1427 // Approximate the vm op time.
duke@1 1428 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
xlu@5042 1429 os::javaTimeNanos() - cleanup_end_time;
duke@1 1430
duke@1 1431 if ( PrintSafepointStatisticsTimeout < 0 ||
gziemski@33222 1432 spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
duke@1 1433 print_statistics();
duke@1 1434 }
drchase@24424 1435 tty->cr();
duke@1 1436
duke@1 1437 // Print out polling page sampling status.
hseigel@49600 1438 tty->print_cr("Polling page always armed");
duke@1 1439
duke@1 1440 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
duke@1 1441 if (_safepoint_reasons[index] != 0) {
bpittore@31592 1442 tty->print_cr("%-26s" UINT64_FORMAT_W(10), VM_Operation::name(index),
duke@1 1443 _safepoint_reasons[index]);
duke@1 1444 }
duke@1 1445 }
duke@1 1446
bpittore@31592 1447 tty->print_cr(UINT64_FORMAT_W(5) " VM operations coalesced during safepoint",
duke@1 1448 _coalesced_vmop_count);
bpittore@31592 1449 tty->print_cr("Maximum sync time " INT64_FORMAT_W(5) " ms",
jwilhelm@46630 1450 (int64_t)(_max_sync_time / MICROUNITS));
xlu@5042 1451 tty->print_cr("Maximum vm operation time (except for Exit VM operation) "
bpittore@31592 1452 INT64_FORMAT_W(5) " ms",
jwilhelm@46630 1453 (int64_t)(_max_vmop_time / MICROUNITS));
duke@1 1454 }