src/share/vm/runtime/sweeper.cpp

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 110 
 111 void NMethodSweeper::record_sweep(nmethod* nm, int line) {
 112   if (_records != NULL) {
 113     _records[_sweep_index].traversal = _traversals;
 114     _records[_sweep_index].traversal_mark = nm->_stack_traversal_mark;
 115     _records[_sweep_index].invocation = _invocations;
 116     _records[_sweep_index].compile_id = nm->compile_id();
 117     _records[_sweep_index].kind = nm->compile_kind();
 118     _records[_sweep_index].state = nm->_state;
 119     _records[_sweep_index].vep = nm->verified_entry_point();
 120     _records[_sweep_index].uep = nm->entry_point();
 121     _records[_sweep_index].line = line;
 122 
 123     _sweep_index = (_sweep_index + 1) % SweeperLogEntries;
 124   }
 125 }
 126 #else
 127 #define SWEEP(nm)
 128 #endif
 129 
 130 
 131 long      NMethodSweeper::_traversals = 0;   // No. of stack traversals performed
 132 nmethod*  NMethodSweeper::_current = NULL;   // Current nmethod
 133 int       NMethodSweeper::_seen = 0 ;        // No. of nmethods we have currently processed in current pass of CodeCache

 134 int       NMethodSweeper::_flushed_count = 0;   // Nof. nmethods flushed in current sweep
 135 int       NMethodSweeper::_zombified_count = 0; // Nof. nmethods made zombie in current sweep
 136 int       NMethodSweeper::_marked_count = 0;    // Nof. nmethods marked for reclaim in current sweep
 137 
 138 volatile int NMethodSweeper::_invocations = 0;   // No. of invocations left until we are completed with this pass
 139 volatile int NMethodSweeper::_sweep_started = 0; // Whether a sweep is in progress.
 140 
 141 jint      NMethodSweeper::_locked_seen = 0;
 142 jint      NMethodSweeper::_not_entrant_seen_on_stack = 0;
 143 bool      NMethodSweeper::_resweep = false;
 144 jint      NMethodSweeper::_flush_token = 0;
 145 jlong     NMethodSweeper::_last_full_flush_time = 0;
 146 int       NMethodSweeper::_highest_marked = 0;
 147 int       NMethodSweeper::_dead_compile_ids = 0;
 148 long      NMethodSweeper::_last_flush_traversal_id = 0;
 149 
 150 int       NMethodSweeper::_number_of_flushes = 0; // Total of full traversals caused by full cache
 151 int       NMethodSweeper::_total_nof_methods_reclaimed = 0;
 152 jlong     NMethodSweeper::_total_time_sweeping = 0;
 153 jlong     NMethodSweeper::_total_time_this_sweep = 0;
 154 jlong     NMethodSweeper::_peak_sweep_time = 0;
 155 jlong     NMethodSweeper::_peak_sweep_fraction_time = 0;
 156 jlong     NMethodSweeper::_total_disconnect_time = 0;
 157 jlong     NMethodSweeper::_peak_disconnect_time = 0;
 158 
 159 class MarkActivationClosure: public CodeBlobClosure {
 160 public:
 161   virtual void do_code_blob(CodeBlob* cb) {



 162     // If we see an activation belonging to a non_entrant nmethod, we mark it.
 163     if (cb->is_nmethod() && ((nmethod*)cb)->is_not_entrant()) {
 164       ((nmethod*)cb)->mark_as_seen_on_stack();

 165     }
 166   }
 167 };
 168 static MarkActivationClosure mark_activation_closure;
 169 


















 170 bool NMethodSweeper::sweep_in_progress() {
 171   return (_current != NULL);
 172 }
 173 
 174 void NMethodSweeper::scan_stacks() {



 175   assert(SafepointSynchronize::is_at_safepoint(), "must be executed at a safepoint");
 176   if (!MethodFlushing) return;
 177 
 178   // No need to synchronize access, since this is always executed at a
 179   // safepoint.

 180 
 181   // Make sure CompiledIC_lock in unlocked, since we might update some
 182   // inline caches. If it is, we just bail-out and try later.
 183   if (CompiledIC_lock->is_locked() || Patching_lock->is_locked()) return;
 184 

 185   // Check for restart
 186   assert(CodeCache::find_blob_unsafe(_current) == _current, "Sweeper nmethod cached state invalid");
 187   if (!sweep_in_progress() && _resweep) {
 188     _seen        = 0;
 189     _invocations = NmethodSweepFraction;
 190     _current     = CodeCache::first_nmethod();
 191     _traversals  += 1;
 192     _total_time_this_sweep = 0;
 193 
 194     if (PrintMethodFlushing) {
 195       tty->print_cr("### Sweep: stack traversal %d", _traversals);
 196     }
 197     Threads::nmethods_do(&mark_activation_closure);
 198 
 199     // reset the flags since we started a scan from the beginning.
 200     _resweep = false;
 201     _locked_seen = 0;
 202     _not_entrant_seen_on_stack = 0;
 203   }
 204 
 205   if (UseCodeCacheFlushing) {
 206     // only allow new flushes after the interval is complete.
 207     jlong now           = os::javaTimeMillis();
 208     jlong max_interval  = (jlong)MinCodeCacheFlushingInterval * (jlong)1000;
 209     jlong curr_interval = now - _last_full_flush_time;
 210     if (curr_interval > max_interval) {
 211       _flush_token = 0;
 212     }
 213 
 214     if (!CodeCache::needs_flushing() && !CompileBroker::should_compile_new_jobs()) {
 215       CompileBroker::set_should_compile_new_jobs(CompileBroker::run_compilation);
 216       log_sweep("restart_compiler");
 217     }
 218   }
 219 }
 220 
 221 void NMethodSweeper::possibly_sweep() {
 222   assert(JavaThread::current()->thread_state() == _thread_in_vm, "must run in vm mode");
 223   if (!MethodFlushing || !sweep_in_progress()) return;


 224 
 225   if (_invocations > 0) {
 226     // Only one thread at a time will sweep
 227     jint old = Atomic::cmpxchg( 1, &_sweep_started, 0 );
 228     if (old != 0) {
 229       return;
 230     }
 231 #ifdef ASSERT
 232     if (LogSweeper && _records == NULL) {
 233       // Create the ring buffer for the logging code
 234       _records = NEW_C_HEAP_ARRAY(SweeperRecord, SweeperLogEntries, mtGC);
 235       memset(_records, 0, sizeof(SweeperRecord) * SweeperLogEntries);
 236     }
 237 #endif
 238     if (_invocations > 0) {
 239       sweep_code_cache();
 240       _invocations--;
 241     }
 242     _sweep_started = 0;
 243   }
 244 }
 245 
 246 void NMethodSweeper::sweep_code_cache() {
 247 
 248   jlong sweep_start_counter = os::elapsed_counter();
 249 
 250   _flushed_count   = 0;
 251   _zombified_count = 0;
 252   _marked_count    = 0;
 253 
 254   if (PrintMethodFlushing && Verbose) {
 255     tty->print_cr("### Sweep at %d out of %d. Invocations left: %d", _seen, CodeCache::nof_nmethods(), _invocations);
 256   }
 257 
 258   if (!CompileBroker::should_compile_new_jobs()) {
 259     // If we have turned off compilations we might as well do full sweeps
 260     // in order to reach the clean state faster. Otherwise the sleeping compiler
 261     // threads will slow down sweeping. After a few iterations the cache
 262     // will be clean and sweeping stops (_resweep will not be set)
 263     _invocations = 1;
 264   }
 265 
 266   // We want to visit all nmethods after NmethodSweepFraction
 267   // invocations so divide the remaining number of nmethods by the
 268   // remaining number of invocations.  This is only an estimate since
 269   // the number of nmethods changes during the sweep so the final
 270   // stage must iterate until it there are no more nmethods.
 271   int todo = (CodeCache::nof_nmethods() - _seen) / _invocations;
 272 
 273   assert(!SafepointSynchronize::is_at_safepoint(), "should not be in safepoint when we get here");
 274   assert(!CodeCache_lock->owned_by_self(), "just checking");
 275 
 276   {
 277     MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
 278 
 279     // The last invocation iterates until there are no more nmethods
 280     for (int i = 0; (i < todo || _invocations == 1) && _current != NULL; i++) {
 281       if (SafepointSynchronize::is_synchronizing()) { // Safepoint request
 282         if (PrintMethodFlushing && Verbose) {
 283           tty->print_cr("### Sweep at %d out of %d, invocation: %d, yielding to safepoint", _seen, CodeCache::nof_nmethods(), _invocations);
 284         }
 285         MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
 286 
 287         assert(Thread::current()->is_Java_thread(), "should be java thread");
 288         JavaThread* thread = (JavaThread*)Thread::current();
 289         ThreadBlockInVM tbivm(thread);
 290         thread->java_suspend_self();
 291       }
 292       // Since we will give up the CodeCache_lock, always skip ahead
 293       // to the next nmethod.  Other blobs can be deleted by other
 294       // threads but nmethods are only reclaimed by the sweeper.
 295       nmethod* next = CodeCache::next_nmethod(_current);
 296 
 297       // Now ready to process nmethod and give up CodeCache_lock
 298       {
 299         MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
 300         process_nmethod(_current);
 301       }
 302       _seen++;
 303       _current = next;
 304     }
 305   }
 306 
 307   assert(_invocations > 1 || _current == NULL, "must have scanned the whole cache");
 308 
 309   if (!sweep_in_progress() && !_resweep && (_locked_seen || _not_entrant_seen_on_stack)) {
 310     // we've completed a scan without making progress but there were
 311     // nmethods we were unable to process either because they were
 312     // locked or were still on stack.  We don't have to aggresively
 313     // clean them up so just stop scanning.  We could scan once more
 314     // but that complicates the control logic and it's unlikely to
 315     // matter much.
 316     if (PrintMethodFlushing) {
 317       tty->print_cr("### Couldn't make progress on some nmethods so stopping sweep");
 318     }
 319   }
 320 
 321   jlong sweep_end_counter = os::elapsed_counter();
 322   jlong sweep_time = sweep_end_counter - sweep_start_counter;
 323   _total_time_sweeping  += sweep_time;
 324   _total_time_this_sweep += sweep_time;
 325   _peak_sweep_fraction_time = MAX2(sweep_time, _peak_sweep_fraction_time);
 326   _total_nof_methods_reclaimed += _flushed_count;
 327 
 328   EventSweepCodeCache event(UNTIMED);
 329   if (event.should_commit()) {
 330     event.set_starttime(sweep_start_counter);
 331     event.set_endtime(sweep_end_counter);
 332     event.set_sweepIndex(_traversals);
 333     event.set_sweepFractionIndex(NmethodSweepFraction - _invocations + 1);
 334     event.set_sweptCount(todo);
 335     event.set_flushedCount(_flushed_count);
 336     event.set_markedCount(_marked_count);
 337     event.set_zombifiedCount(_zombified_count);
 338     event.commit();
 339   }
 340 
 341 #ifdef ASSERT
 342   if(PrintMethodFlushing) {
 343     tty->print_cr("### sweeper:      sweep time(%d): " INT64_FORMAT, _invocations, (jlong)sweep_time);
 344   }
 345 #endif
 346 
 347   if (_invocations == 1) {
 348     _peak_sweep_time = MAX2(_peak_sweep_time, _total_time_this_sweep);
 349     log_sweep("finished");
 350   }
 351 
 352   // Sweeper is the only case where memory is released,
 353   // check here if it is time to restart the compiler.
 354   if (UseCodeCacheFlushing && !CompileBroker::should_compile_new_jobs() && !CodeCache::needs_flushing()) {






 355     CompileBroker::set_should_compile_new_jobs(CompileBroker::run_compilation);
 356     log_sweep("restart_compiler");
 357   }
 358 }
 359 
 360 class NMethodMarker: public StackObj {
 361  private:
 362   CompilerThread* _thread;
 363  public:
 364   NMethodMarker(nmethod* nm) {
 365     _thread = CompilerThread::current();
 366     if (!nm->is_zombie() && !nm->is_unloaded()) {
 367       // Only expose live nmethods for scanning
 368     _thread->set_scanned_nmethod(nm);
 369   }
 370   }
 371   ~NMethodMarker() {
 372     _thread->set_scanned_nmethod(NULL);
 373   }
 374 };
 375 
 376 void NMethodSweeper::release_nmethod(nmethod *nm) {
 377   // Clean up any CompiledICHolders
 378   {
 379     ResourceMark rm;
 380     MutexLocker ml_patch(CompiledIC_lock);
 381     RelocIterator iter(nm);
 382     while (iter.next()) {
 383       if (iter.type() == relocInfo::virtual_call_type) {
 384         CompiledIC::cleanup_call_site(iter.virtual_call_reloc());
 385       }
 386     }
 387   }
 388 
 389   MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
 390   nm->flush();
 391 }
 392 
 393 void NMethodSweeper::process_nmethod(nmethod *nm) {
 394   assert(!CodeCache_lock->owned_by_self(), "just checking");
 395 

 396   // Make sure this nmethod doesn't get unloaded during the scan,
 397   // since the locks acquired below might safepoint.
 398   NMethodMarker nmm(nm);
 399 
 400   SWEEP(nm);
 401 
 402   // Skip methods that are currently referenced by the VM
 403   if (nm->is_locked_by_vm()) {
 404     // But still remember to clean-up inline caches for alive nmethods
 405     if (nm->is_alive()) {
 406       // Clean-up all inline caches that points to zombie/non-reentrant methods
 407       MutexLocker cl(CompiledIC_lock);
 408       nm->cleanup_inline_caches();
 409       SWEEP(nm);
 410     } else {
 411       _locked_seen++;
 412       SWEEP(nm);
 413     }
 414     return;
 415   }
 416 
 417   if (nm->is_zombie()) {
 418     // If it is first time, we see nmethod then we mark it. Otherwise,
 419     // we reclame it. When we have seen a zombie method twice, we know that
 420     // there are no inline caches that refer to it.
 421     if (nm->is_marked_for_reclamation()) {
 422       assert(!nm->is_locked_by_vm(), "must not flush locked nmethods");
 423       if (PrintMethodFlushing && Verbose) {
 424         tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (marked for reclamation) being flushed", nm->compile_id(), nm);
 425       }

 426       release_nmethod(nm);
 427       _flushed_count++;
 428     } else {
 429       if (PrintMethodFlushing && Verbose) {
 430         tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (zombie) being marked for reclamation", nm->compile_id(), nm);
 431       }
 432       nm->mark_for_reclamation();
 433       _resweep = true;
 434       _marked_count++;
 435       SWEEP(nm);
 436     }
 437   } else if (nm->is_not_entrant()) {
 438     // If there is no current activations of this method on the
 439     // stack we can safely convert it to a zombie method
 440     if (nm->can_not_entrant_be_converted()) {
 441       if (PrintMethodFlushing && Verbose) {
 442         tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (not entrant) being made zombie", nm->compile_id(), nm);
 443       }
 444       nm->make_zombie();
 445       _resweep = true;
 446       _zombified_count++;
 447       SWEEP(nm);
 448     } else {
 449       // Still alive, clean up its inline caches
 450       MutexLocker cl(CompiledIC_lock);
 451       nm->cleanup_inline_caches();
 452       // we coudn't transition this nmethod so don't immediately
 453       // request a rescan.  If this method stays on the stack for a
 454       // long time we don't want to keep rescanning the code cache.
 455       _not_entrant_seen_on_stack++;
 456       SWEEP(nm);
 457     }
 458   } else if (nm->is_unloaded()) {
 459     // Unloaded code, just make it a zombie
 460     if (PrintMethodFlushing && Verbose)
 461       tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (unloaded) being made zombie", nm->compile_id(), nm);
 462 
 463     if (nm->is_osr_method()) {
 464       SWEEP(nm);
 465       // No inline caches will ever point to osr methods, so we can just remove it

 466       release_nmethod(nm);
 467       _flushed_count++;
 468     } else {
 469       nm->make_zombie();
 470       _resweep = true;
 471       _zombified_count++;
 472       SWEEP(nm);
 473     }
 474   } else {
 475     assert(nm->is_alive(), "should be alive");
 476 
 477     if (UseCodeCacheFlushing) {
 478       if (nm->is_speculatively_disconnected() && !nm->is_locked_by_vm() && !nm->is_osr_method() &&
 479           (_traversals > _last_flush_traversal_id + 2) && (nm->compile_id() < _highest_marked)) {
 480         // This method has not been called since the forced cleanup happened












 481         nm->make_not_entrant();

 482       }
 483     }
 484 
 485     // Clean-up all inline caches that points to zombie/non-reentrant methods
 486     MutexLocker cl(CompiledIC_lock);
 487     nm->cleanup_inline_caches();
 488     SWEEP(nm);
 489   }

 490 }
 491 
 492 // Code cache unloading: when compilers notice the code cache is getting full,
 493 // they will call a vm op that comes here. This code attempts to speculatively
 494 // unload the oldest half of the nmethods (based on the compile job id) by
 495 // saving the old code in a list in the CodeCache. Then
 496 // execution resumes. If a method so marked is not called by the second sweeper
 497 // stack traversal after the current one, the nmethod will be marked non-entrant and
 498 // got rid of by normal sweeping. If the method is called, the Method*'s
 499 // _code field is restored and the Method*/nmethod
 500 // go back to their normal state.
 501 void NMethodSweeper::handle_full_code_cache(bool is_full) {
 502 
 503   if (is_full) {
 504     // Since code cache is full, immediately stop new compiles
 505     if (CompileBroker::set_should_compile_new_jobs(CompileBroker::stop_compilation)) {
 506       log_sweep("disable_compiler");
 507     }
 508   }
 509 
 510   // Make sure only one thread can flush
 511   // The token is reset after CodeCacheMinimumFlushInterval in scan stacks,
 512   // no need to check the timeout here.
 513   jint old = Atomic::cmpxchg( 1, &_flush_token, 0 );
 514   if (old != 0) {
 515     return;
 516   }
 517 
 518   VM_HandleFullCodeCache op(is_full);
 519   VMThread::execute(&op);
 520 
 521   // resweep again as soon as possible
 522   _resweep = true;
 523 }
 524 
 525 void NMethodSweeper::speculative_disconnect_nmethods(bool is_full) {
 526   // If there was a race in detecting full code cache, only run
 527   // one vm op for it or keep the compiler shut off
 528 
 529   jlong disconnect_start_counter = os::elapsed_counter();
 530 
 531   // Traverse the code cache trying to dump the oldest nmethods
 532   int curr_max_comp_id = CompileBroker::get_compilation_id();
 533   int flush_target = ((curr_max_comp_id - _dead_compile_ids) / CodeCacheFlushingFraction) + _dead_compile_ids;
 534 
 535   log_sweep("start_cleaning");
 536 
 537   nmethod* nm = CodeCache::alive_nmethod(CodeCache::first());
 538   jint disconnected = 0;
 539   jint made_not_entrant  = 0;
 540   jint nmethod_count = 0;
 541 
 542   while ((nm != NULL)){
 543     int curr_comp_id = nm->compile_id();
 544 
 545     // OSR methods cannot be flushed like this. Also, don't flush native methods
 546     // since they are part of the JDK in most cases
 547     if (!nm->is_osr_method() && !nm->is_locked_by_vm() && !nm->is_native_method()) {
 548 
 549       // only count methods that can be speculatively disconnected
 550       nmethod_count++;
 551 
 552       if (nm->is_in_use() && (curr_comp_id < flush_target)) {
 553         if ((nm->method()->code() == nm)) {
 554           // This method has not been previously considered for
 555           // unloading or it was restored already
 556           CodeCache::speculatively_disconnect(nm);
 557           disconnected++;
 558         } else if (nm->is_speculatively_disconnected()) {
 559           // This method was previously considered for preemptive unloading and was not called since then
 560           CompilationPolicy::policy()->delay_compilation(nm->method());
 561           nm->make_not_entrant();
 562           made_not_entrant++;
 563         }
 564 
 565         if (curr_comp_id > _highest_marked) {
 566           _highest_marked = curr_comp_id;
 567         }
 568       }
 569     }
 570     nm = CodeCache::alive_nmethod(CodeCache::next(nm));
 571   }
 572 
 573   // remember how many compile_ids wheren't seen last flush.
 574   _dead_compile_ids = curr_max_comp_id - nmethod_count;
 575 
 576   log_sweep("stop_cleaning",
 577                        "disconnected='" UINT32_FORMAT "' made_not_entrant='" UINT32_FORMAT "'",
 578                        disconnected, made_not_entrant);
 579 
 580   // Shut off compiler. Sweeper will start over with a new stack scan and
 581   // traversal cycle and turn it back on if it clears enough space.
 582   if (is_full) {
 583     _last_full_flush_time = os::javaTimeMillis();
 584   }
 585 
 586   jlong disconnect_end_counter = os::elapsed_counter();
 587   jlong disconnect_time = disconnect_end_counter - disconnect_start_counter;
 588   _total_disconnect_time += disconnect_time;
 589   _peak_disconnect_time = MAX2(disconnect_time, _peak_disconnect_time);
 590 
 591   EventCleanCodeCache event(UNTIMED);
 592   if (event.should_commit()) {
 593     event.set_starttime(disconnect_start_counter);
 594     event.set_endtime(disconnect_end_counter);
 595     event.set_disconnectedCount(disconnected);
 596     event.set_madeNonEntrantCount(made_not_entrant);
 597     event.commit();
 598   }
 599   _number_of_flushes++;
 600 
 601   // After two more traversals the sweeper will get rid of unrestored nmethods
 602   _last_flush_traversal_id = _traversals;
 603   _resweep = true;
 604 #ifdef ASSERT
 605 
 606   if(PrintMethodFlushing && Verbose) {
 607     tty->print_cr("### sweeper: unload time: " INT64_FORMAT, (jlong)disconnect_time);
 608   }
 609 #endif
 610 }
 611 
 612 
 613 // Print out some state information about the current sweep and the
 614 // state of the code cache if it's requested.
 615 void NMethodSweeper::log_sweep(const char* msg, const char* format, ...) {
 616   if (PrintMethodFlushing) {
 617     stringStream s;
 618     // Dump code cache state into a buffer before locking the tty,
 619     // because log_state() will use locks causing lock conflicts.
 620     CodeCache::log_state(&s);
 621 
 622     ttyLocker ttyl;
 623     tty->print("### sweeper: %s ", msg);
 624     if (format != NULL) {
 625       va_list ap;
 626       va_start(ap, format);
 627       tty->vprint(format, ap);
 628       va_end(ap);
 629     }
 630     tty->print_cr(s.as_string());
 631   }


 110 
 111 void NMethodSweeper::record_sweep(nmethod* nm, int line) {
 112   if (_records != NULL) {
 113     _records[_sweep_index].traversal = _traversals;
 114     _records[_sweep_index].traversal_mark = nm->_stack_traversal_mark;
 115     _records[_sweep_index].invocation = _invocations;
 116     _records[_sweep_index].compile_id = nm->compile_id();
 117     _records[_sweep_index].kind = nm->compile_kind();
 118     _records[_sweep_index].state = nm->_state;
 119     _records[_sweep_index].vep = nm->verified_entry_point();
 120     _records[_sweep_index].uep = nm->entry_point();
 121     _records[_sweep_index].line = line;
 122 
 123     _sweep_index = (_sweep_index + 1) % SweeperLogEntries;
 124   }
 125 }
 126 #else
 127 #define SWEEP(nm)
 128 #endif
 129 


 130 nmethod*  NMethodSweeper::_current         = NULL; // Current nmethod
 131 long      NMethodSweeper::_traversals      = 0;    // Nof. stack traversals performed
 132 int       NMethodSweeper::_seen            = 0;    // Nof. nmethods we have currently processed in current pass of CodeCache
 133 int       NMethodSweeper::_flushed_count   = 0;    // Nof. nmethods flushed in current sweep
 134 int       NMethodSweeper::_zombified_count = 0;    // Nof. nmethods made zombie in current sweep
 135 int       NMethodSweeper::_marked_count    = 0;    // Nof. nmethods marked for reclaim in current sweep
 136 
 137 volatile int NMethodSweeper::_invocations   = 0; // Nof. invocations left until we are completed with this pass
 138 volatile int NMethodSweeper::_sweep_started = 0; // Whether a sweep is in progress.
 139 
 140 jint      NMethodSweeper::_locked_seen               = 0;
 141 jint      NMethodSweeper::_not_entrant_seen_on_stack = 0;
 142 bool      NMethodSweeper::_request_mark_phase        = false;





 143 

 144 int       NMethodSweeper::_total_nof_methods_reclaimed = 0;
 145 jlong     NMethodSweeper::_total_time_sweeping         = 0;
 146 jlong     NMethodSweeper::_total_time_this_sweep       = 0;
 147 jlong     NMethodSweeper::_peak_sweep_time             = 0;
 148 jlong     NMethodSweeper::_peak_sweep_fraction_time    = 0;
 149 int       NMethodSweeper::_hotness_counter_reset_val   = 0;
 150 
 151 
 152 class MarkActivationClosure: public CodeBlobClosure {
 153 public:
 154   virtual void do_code_blob(CodeBlob* cb) {
 155     if (cb->is_nmethod()) {
 156       nmethod* nm = (nmethod*)cb;
 157       nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val());
 158       // If we see an activation belonging to a non_entrant nmethod, we mark it.
 159       if (nm->is_not_entrant()) {
 160         nm->mark_as_seen_on_stack();
 161       }
 162     }
 163   }
 164 };
 165 static MarkActivationClosure mark_activation_closure;
 166 
 167 class SetHotnessClosure: public CodeBlobClosure {
 168 public:
 169   virtual void do_code_blob(CodeBlob* cb) {
 170     if (cb->is_nmethod()) {
 171       nmethod* nm = (nmethod*)cb;
 172       nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val());
 173     }
 174   }
 175 };
 176 static SetHotnessClosure set_hotness_closure;
 177 
 178 
 179 int NMethodSweeper::hotness_counter_reset_val() {
 180   if (_hotness_counter_reset_val == 0) {
 181     _hotness_counter_reset_val = (ReservedCodeCacheSize < M) ? 1 : (ReservedCodeCacheSize / M) * 2;
 182   }
 183   return _hotness_counter_reset_val;
 184 }
 185 bool NMethodSweeper::sweep_in_progress() {
 186   return (_current != NULL);
 187 }
 188 
 189 // Scans the stacks of all Java threads and marks activations of not-entrant methods.
 190 // No need to synchronize access, since 'mark_active_nmethods' is always executed at a
 191 // safepoint.
 192 void NMethodSweeper::mark_active_nmethods() {
 193   assert(SafepointSynchronize::is_at_safepoint(), "must be executed at a safepoint");
 194   // If we do not want to reclaim not-entrant or zombie methods there is no need
 195   // to scan stacks
 196   if (!MethodFlushing) {
 197     return;
 198   }
 199 
 200   // Make sure CompiledIC_lock in unlocked, since we might update some
 201   // inline caches. If it is, we just bail-out and try later.
 202   if (CompiledIC_lock->is_locked() || Patching_lock->is_locked()) return;
 203 
 204 
 205   // Check for restart
 206   assert(CodeCache::find_blob_unsafe(_current) == _current, "Sweeper nmethod cached state invalid");
 207   if (!sweep_in_progress() && need_marking_phase()) {
 208     _seen        = 0;
 209     _invocations = NmethodSweepFraction;
 210     _current     = CodeCache::first_nmethod();
 211     _traversals  += 1;
 212     _total_time_this_sweep = 0;
 213 
 214     if (PrintMethodFlushing) {
 215       tty->print_cr("### Sweep: stack traversal %d", _traversals);
 216     }
 217     Threads::nmethods_do(&mark_activation_closure);
 218 
 219     // reset the flags since we started a scan from the beginning.
 220     reset_nmethod_marking();
 221     _locked_seen = 0;
 222     _not_entrant_seen_on_stack = 0;
 223   // Only set hotness counter
 224   } else {
 225     Threads::nmethods_do(&set_hotness_closure);












 226   }
 227 }
 228 
 229 void NMethodSweeper::possibly_sweep() {
 230   assert(JavaThread::current()->thread_state() == _thread_in_vm, "must run in vm mode");
 231   if (!MethodFlushing || !sweep_in_progress()) {
 232     return;
 233   }
 234 
 235   if (_invocations > 0) {
 236     // Only one thread at a time will sweep
 237     jint old = Atomic::cmpxchg( 1, &_sweep_started, 0 );
 238     if (old != 0) {
 239       return;
 240     }
 241 #ifdef ASSERT
 242     if (LogSweeper && _records == NULL) {
 243       // Create the ring buffer for the logging code
 244       _records = NEW_C_HEAP_ARRAY(SweeperRecord, SweeperLogEntries, mtGC);
 245       memset(_records, 0, sizeof(SweeperRecord) * SweeperLogEntries);
 246     }
 247 #endif
 248     if (_invocations > 0) {
 249       sweep_code_cache();
 250       _invocations--;
 251     }
 252     _sweep_started = 0;
 253   }
 254 }
 255 
 256 void NMethodSweeper::sweep_code_cache() {
 257 
 258   jlong sweep_start_counter = os::elapsed_counter();
 259 
 260   _flushed_count   = 0;
 261   _zombified_count = 0;
 262   _marked_count    = 0;
 263 
 264   if (PrintMethodFlushing && Verbose) {
 265     tty->print_cr("### Sweep at %d out of %d. Invocations left: %d", _seen, CodeCache::nof_nmethods(), _invocations);
 266   }
 267 
 268   if (!CompileBroker::should_compile_new_jobs()) {
 269     // If we have turned off compilations we might as well do full sweeps
 270     // in order to reach the clean state faster. Otherwise the sleeping compiler
 271     // threads will slow down sweeping.

 272     _invocations = 1;
 273   }
 274 
 275   // We want to visit all nmethods after NmethodSweepFraction
 276   // invocations so divide the remaining number of nmethods by the
 277   // remaining number of invocations.  This is only an estimate since
 278   // the number of nmethods changes during the sweep so the final
 279   // stage must iterate until it there are no more nmethods.
 280   int todo = (CodeCache::nof_nmethods() - _seen) / _invocations;

 281   assert(!SafepointSynchronize::is_at_safepoint(), "should not be in safepoint when we get here");
 282   assert(!CodeCache_lock->owned_by_self(), "just checking");
 283   int flushed_memory = 0;
 284   {
 285     MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
 286 
 287     // The last invocation iterates until there are no more nmethods
 288     for (int i = 0; (i < todo || _invocations == 1) && _current != NULL; i++) {
 289       if (SafepointSynchronize::is_synchronizing()) { // Safepoint request
 290         if (PrintMethodFlushing && Verbose) {
 291           tty->print_cr("### Sweep at %d out of %d, invocation: %d, yielding to safepoint", _seen, CodeCache::nof_nmethods(), _invocations);
 292         }
 293         MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
 294 
 295         assert(Thread::current()->is_Java_thread(), "should be java thread");
 296         JavaThread* thread = (JavaThread*)Thread::current();
 297         ThreadBlockInVM tbivm(thread);
 298         thread->java_suspend_self();
 299       }
 300       // Since we will give up the CodeCache_lock, always skip ahead
 301       // to the next nmethod.  Other blobs can be deleted by other
 302       // threads but nmethods are only reclaimed by the sweeper.
 303       nmethod* next = CodeCache::next_nmethod(_current);
 304 
 305       // Now ready to process nmethod and give up CodeCache_lock
 306       {
 307         MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
 308         flushed_memory += process_nmethod(_current);
 309       }
 310       _seen++;
 311       _current = next;
 312     }
 313   }
 314 
 315   assert(_invocations > 1 || _current == NULL, "must have scanned the whole cache");
 316 
 317   if (!sweep_in_progress() && !need_marking_phase() && (_locked_seen || _not_entrant_seen_on_stack)) {
 318     // we've completed a scan without making progress but there were
 319     // nmethods we were unable to process either because they were
 320     // locked or were still on stack. We don't have to aggressively
 321     // clean them up so just stop scanning. We could scan once more
 322     // but that complicates the control logic and it's unlikely to
 323     // matter much.
 324     if (PrintMethodFlushing) {
 325       tty->print_cr("### Couldn't make progress on some nmethods so stopping sweep");
 326     }
 327   }
 328 
 329   jlong sweep_end_counter = os::elapsed_counter();
 330   jlong sweep_time = sweep_end_counter - sweep_start_counter;
 331   _total_time_sweeping  += sweep_time;
 332   _total_time_this_sweep += sweep_time;
 333   _peak_sweep_fraction_time = MAX2(sweep_time, _peak_sweep_fraction_time);
 334   _total_nof_methods_reclaimed += _flushed_count;
 335 
 336   EventSweepCodeCache event(UNTIMED);
 337   if (event.should_commit()) {
 338     event.set_starttime(sweep_start_counter);
 339     event.set_endtime(sweep_end_counter);
 340     event.set_sweepIndex(_traversals);
 341     event.set_sweepFractionIndex(NmethodSweepFraction - _invocations + 1);
 342     event.set_sweptCount(todo);
 343     event.set_flushedCount(_flushed_count);
 344     event.set_markedCount(_marked_count);
 345     event.set_zombifiedCount(_zombified_count);
 346     event.commit();
 347   }
 348 
 349 #ifdef ASSERT
 350   if(PrintMethodFlushing) {
 351     tty->print_cr("### sweeper:      sweep time(%d): " INT64_FORMAT, _invocations, (jlong)sweep_time);
 352   }
 353 #endif
 354 
 355   if (_invocations == 1) {
 356     _peak_sweep_time = MAX2(_peak_sweep_time, _total_time_this_sweep);
 357     log_sweep("finished");
 358   }
 359 
 360   // Sweeper is the only case where memory is released, check here if it
 361   // is time to restart the compiler. Only checking if there is a certain
 362   // amount of free memory in the code cache might lead to re-enabling
 363   // compilation although no memory has been released. For example, there are
 364   // cases when compilation was disabled although there is 4MB (or more) free
 365   // memory in the code cache. The reason is code cache fragmentation. Therefore,
 366   // it only makes sense to re-enable compilation if we have actually freed memory.
 367   // Note that typically several kB are released per sweep cycle (16MB).
 368   if (UseCodeCacheFlushing && (!CompileBroker::should_compile_new_jobs() && (flushed_memory > 0))) {
 369     CompileBroker::set_should_compile_new_jobs(CompileBroker::run_compilation);
 370     log_sweep("restart_compiler");
 371   }
 372 }
 373 
 374 class NMethodMarker: public StackObj {
 375  private:
 376   CompilerThread* _thread;
 377  public:
 378   NMethodMarker(nmethod* nm) {
 379     _thread = CompilerThread::current();
 380     if (!nm->is_zombie() && !nm->is_unloaded()) {
 381       // Only expose live nmethods for scanning
 382       _thread->set_scanned_nmethod(nm);
 383     }
 384   }
 385   ~NMethodMarker() {
 386     _thread->set_scanned_nmethod(NULL);
 387   }
 388 };
 389 
 390 void NMethodSweeper::release_nmethod(nmethod *nm) {
 391   // Clean up any CompiledICHolders
 392   {
 393     ResourceMark rm;
 394     MutexLocker ml_patch(CompiledIC_lock);
 395     RelocIterator iter(nm);
 396     while (iter.next()) {
 397       if (iter.type() == relocInfo::virtual_call_type) {
 398         CompiledIC::cleanup_call_site(iter.virtual_call_reloc());
 399       }
 400     }
 401   }
 402 
 403   MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
 404   nm->flush();
 405 }
 406 
 407 int NMethodSweeper::process_nmethod(nmethod *nm) {
 408   assert(!CodeCache_lock->owned_by_self(), "just checking");
 409 
 410   int flushed_memory = 0;
 411   // Make sure this nmethod doesn't get unloaded during the scan,
 412   // since the locks acquired might below the safepoint.
 413   NMethodMarker nmm(nm);

 414   SWEEP(nm);
 415 
 416   // Skip methods that are currently referenced by the VM
 417   if (nm->is_locked_by_vm()) {
 418     // But still remember to clean-up inline caches for alive nmethods
 419     if (nm->is_alive()) {
 420       // Clean inline caches that point to zombie/non-entrant methods
 421       MutexLocker cl(CompiledIC_lock);
 422       nm->cleanup_inline_caches();
 423       SWEEP(nm);
 424     } else {
 425       _locked_seen++;
 426       SWEEP(nm);
 427     }
 428     return flushed_memory;
 429   }
 430 
 431   if (nm->is_zombie()) {
 432     // If it is the first time we see nmethod then we mark it. Otherwise,
 433     // we reclaim it. When we have seen a zombie method twice, we know that
 434     // there are no inline caches that refer to it.
 435     if (nm->is_marked_for_reclamation()) {
 436       assert(!nm->is_locked_by_vm(), "must not flush locked nmethods");
 437       if (PrintMethodFlushing && Verbose) {
 438         tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (marked for reclamation) being flushed", nm->compile_id(), nm);
 439       }
 440       flushed_memory = nm->total_size();
 441       release_nmethod(nm);
 442       _flushed_count++;
 443     } else {
 444       if (PrintMethodFlushing && Verbose) {
 445         tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (zombie) being marked for reclamation", nm->compile_id(), nm);
 446       }
 447       nm->mark_for_reclamation();
 448       request_nmethod_marking();
 449       _marked_count++;
 450       SWEEP(nm);
 451     }
 452   } else if (nm->is_not_entrant()) {
 453     // If there are no current activations of this method on the
 454     // stack we can safely convert it to a zombie method
 455     if (nm->can_not_entrant_be_converted()) {
 456       if (PrintMethodFlushing && Verbose) {
 457         tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (not entrant) being made zombie", nm->compile_id(), nm);
 458       }
 459       nm->make_zombie();
 460       request_nmethod_marking();
 461       _zombified_count++;
 462       SWEEP(nm);
 463     } else {
 464       // Still alive, clean up its inline caches
 465       MutexLocker cl(CompiledIC_lock);
 466       nm->cleanup_inline_caches();
 467       // we coudn't transition this nmethod so don't immediately
 468       // request a rescan.  If this method stays on the stack for a
 469       // long time we don't want to keep rescanning the code cache.
 470       _not_entrant_seen_on_stack++;
 471       SWEEP(nm);
 472     }
 473   } else if (nm->is_unloaded()) {
 474     // Unloaded code, just make it a zombie
 475     if (PrintMethodFlushing && Verbose) {
 476       tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (unloaded) being made zombie", nm->compile_id(), nm);
 477     }
 478     if (nm->is_osr_method()) {
 479       SWEEP(nm);
 480       // No inline caches will ever point to osr methods, so we can just remove it
 481       flushed_memory = nm->total_size();
 482       release_nmethod(nm);
 483       _flushed_count++;
 484     } else {
 485       nm->make_zombie();
 486       request_nmethod_marking();
 487       _zombified_count++;
 488       SWEEP(nm);
 489     }
 490   } else {


 491     if (UseCodeCacheFlushing) {
 492       if (!nm->is_locked_by_vm() && !nm->is_osr_method() && !nm->is_native_method()) {
 493         // Do not make native methods and OSR-methods not-entrant
 494         nm->dec_hotness_counter();
 495         // This method is cold and the code cache fills up => get rid of it.
 496         int reset_val = hotness_counter_reset_val();
 497         int time_since_reset = reset_val - nm->hotness_counter();
 498         double threshold = -reset_val + (CodeCache::reverse_free_ratio() * NmethodSweepActivity);
 499         // A method is marked as not-entrance if the method is
 500         // 1) 'old enough': nm->hotness_counter() < threshold
 501         // 2) The method was in_use for a minimum amount of time: (time_since_reset > 10)
 502         //    The second condition is necessary if we are dealing with very small code cache
 503         //    sizes (e.g., <10m) and the code cache size is too small to hold all hot methods.
 504         //    The second condition ensures that methods are not immediately made not-entrant
 505         //    just after compilation.
 506         if ((nm->hotness_counter() < threshold) && (time_since_reset > 10)) {
 507            nm->make_not_entrant();
 508            request_nmethod_marking();
 509         }
 510       }
 511     }
 512     // Clean-up all inline caches that point to zombie/non-reentrant methods
 513     MutexLocker cl(CompiledIC_lock);
 514     nm->cleanup_inline_caches();
 515     SWEEP(nm);
 516   }
 517   return flushed_memory;
 518 }

























































































































 519 
 520 // Print out some state information about the current sweep and the
 521 // state of the code cache if it's requested.
 522 void NMethodSweeper::log_sweep(const char* msg, const char* format, ...) {
 523   if (PrintMethodFlushing) {
 524     stringStream s;
 525     // Dump code cache state into a buffer before locking the tty,
 526     // because log_state() will use locks causing lock conflicts.
 527     CodeCache::log_state(&s);
 528 
 529     ttyLocker ttyl;
 530     tty->print("### sweeper: %s ", msg);
 531     if (format != NULL) {
 532       va_list ap;
 533       va_start(ap, format);
 534       tty->vprint(format, ap);
 535       va_end(ap);
 536     }
 537     tty->print_cr(s.as_string());
 538   }