src/share/vm/runtime/sweeper.cpp
Index Unified diffs Context diffs Sdiffs Patch New Old Previous File Next File 8015774 Sdiff src/share/vm/runtime

src/share/vm/runtime/sweeper.cpp

Print this page




 110 }
 111 
 112 void NMethodSweeper::record_sweep(nmethod* nm, int line) {
 113   if (_records != NULL) {
 114     _records[_sweep_index].traversal = _traversals;
 115     _records[_sweep_index].traversal_mark = nm->_stack_traversal_mark;
 116     _records[_sweep_index].invocation = _sweep_fractions_left;
 117     _records[_sweep_index].compile_id = nm->compile_id();
 118     _records[_sweep_index].kind = nm->compile_kind();
 119     _records[_sweep_index].state = nm->_state;
 120     _records[_sweep_index].vep = nm->verified_entry_point();
 121     _records[_sweep_index].uep = nm->entry_point();
 122     _records[_sweep_index].line = line;
 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;    // Stack scan count, also sweep ID.
 132 long     NMethodSweeper::_total_nof_code_cache_sweeps  = 0;    // Total number of full sweeps of the code cache
 133 long     NMethodSweeper::_time_counter                 = 0;    // Virtual time used to periodically invoke sweeper
 134 long     NMethodSweeper::_last_sweep                   = 0;    // Value of _time_counter when the last sweep happened
 135 int      NMethodSweeper::_seen                         = 0;    // Nof. nmethod we have currently processed in current pass of CodeCache
 136 int      NMethodSweeper::_flushed_count                = 0;    // Nof. nmethods flushed in current sweep
 137 int      NMethodSweeper::_zombified_count              = 0;    // Nof. nmethods made zombie in current sweep
 138 int      NMethodSweeper::_marked_for_reclamation_count = 0;    // Nof. nmethods marked for reclaim in current sweep
 139 
 140 volatile bool NMethodSweeper::_should_sweep            = true; // Indicates if we should invoke the sweeper
 141 volatile int  NMethodSweeper::_sweep_fractions_left    = 0;    // Nof. invocations left until we are completed with this pass
 142 volatile int  NMethodSweeper::_sweep_started           = 0;    // Flag to control conc sweeper
 143 volatile int  NMethodSweeper::_bytes_changed           = 0;    // Counts the total nmethod size if the nmethod changed from:
 144                                                                //   1) alive       -> not_entrant
 145                                                                //   2) not_entrant -> zombie
 146                                                                //   3) zombie      -> marked_for_reclamation
 147 int    NMethodSweeper::_hotness_counter_reset_val       = 0;
 148 
 149 long   NMethodSweeper::_total_nof_methods_reclaimed     = 0;    // Accumulated nof methods flushed
 150 long   NMethodSweeper::_total_nof_c2_methods_reclaimed  = 0;    // Accumulated nof methods flushed
 151 size_t NMethodSweeper::_total_flushed_size              = 0;    // Total number of bytes flushed from the code cache
 152 Tickspan  NMethodSweeper::_total_time_sweeping;                 // Accumulated time sweeping
 153 Tickspan  NMethodSweeper::_total_time_this_sweep;               // Total time this sweep
 154 Tickspan  NMethodSweeper::_peak_sweep_time;                     // Peak time for a full sweep
 155 Tickspan  NMethodSweeper::_peak_sweep_fraction_time;            // Peak time sweeping one fraction
 156 
 157 
 158 
 159 class MarkActivationClosure: public CodeBlobClosure {
 160 public:
 161   virtual void do_code_blob(CodeBlob* cb) {
 162     if (cb->is_nmethod()) {
 163       nmethod* nm = (nmethod*)cb;
 164       nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val());
 165       // If we see an activation belonging to a non_entrant nmethod, we mark it.
 166       if (nm->is_not_entrant()) {
 167         nm->mark_as_seen_on_stack();
 168       }
 169     }
 170   }
 171 };
 172 static MarkActivationClosure mark_activation_closure;
 173 
 174 class SetHotnessClosure: public CodeBlobClosure {
 175 public:
 176   virtual void do_code_blob(CodeBlob* cb) {
 177     if (cb->is_nmethod()) {
 178       nmethod* nm = (nmethod*)cb;
 179       nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val());
 180     }
 181   }
 182 };
 183 static SetHotnessClosure set_hotness_closure;
 184 
 185 
 186 int NMethodSweeper::hotness_counter_reset_val() {
 187   if (_hotness_counter_reset_val == 0) {
 188     _hotness_counter_reset_val = (ReservedCodeCacheSize < M) ? 1 : (ReservedCodeCacheSize / M) * 2;
 189   }
 190   return _hotness_counter_reset_val;
 191 }
 192 bool NMethodSweeper::sweep_in_progress() {
 193   return (_current != NULL);
 194 }
 195 
 196 // Scans the stacks of all Java threads and marks activations of not-entrant methods.
 197 // No need to synchronize access, since 'mark_active_nmethods' is always executed at a
 198 // safepoint.
 199 void NMethodSweeper::mark_active_nmethods() {
 200   assert(SafepointSynchronize::is_at_safepoint(), "must be executed at a safepoint");
 201   // If we do not want to reclaim not-entrant or zombie methods there is no need
 202   // to scan stacks
 203   if (!MethodFlushing) {
 204     return;
 205   }
 206 
 207   // Increase time so that we can estimate when to invoke the sweeper again.
 208   _time_counter++;
 209 
 210   // Check for restart
 211   assert(CodeCache::find_blob_unsafe(_current) == _current, "Sweeper nmethod cached state invalid");
 212   if (!sweep_in_progress()) {
 213     _seen = 0;
 214     _sweep_fractions_left = NmethodSweepFraction;
 215     _current = CodeCache::first_nmethod();

 216     _traversals += 1;
 217     _total_time_this_sweep = Tickspan();
 218 
 219     if (PrintMethodFlushing) {
 220       tty->print_cr("### Sweep: stack traversal %d", _traversals);
 221     }
 222     Threads::nmethods_do(&mark_activation_closure);
 223 
 224   } else {
 225     // Only set hotness counter
 226     Threads::nmethods_do(&set_hotness_closure);
 227   }
 228 
 229   OrderAccess::storestore();
 230 }
 231 /**
 232  * This function invokes the sweeper if at least one of the three conditions is met:
 233  *    (1) The code cache is getting full
 234  *    (2) There are sufficient state changes in/since the last sweep.
 235  *    (3) We have not been sweeping for 'some time'


 250   // the formula considers how much space in the code cache is currently used. Here are
 251   // some examples that will (hopefully) help in understanding.
 252   //
 253   // Small ReservedCodeCacheSizes:  (e.g., < 16M) We invoke the sweeper every time, since
 254   //                                              the result of the division is 0. This
 255   //                                              keeps the used code cache size small
 256   //                                              (important for embedded Java)
 257   // Large ReservedCodeCacheSize :  (e.g., 256M + code cache is 10% full). The formula
 258   //                                              computes: (256 / 16) - 1 = 15
 259   //                                              As a result, we invoke the sweeper after
 260   //                                              15 invocations of 'mark_active_nmethods.
 261   // Large ReservedCodeCacheSize:   (e.g., 256M + code Cache is 90% full). The formula
 262   //                                              computes: (256 / 16) - 10 = 6.
 263   if (!_should_sweep) {
 264     const int time_since_last_sweep = _time_counter - _last_sweep;
 265     // ReservedCodeCacheSize has an 'unsigned' type. We need a 'signed' type for max_wait_time,
 266     // since 'time_since_last_sweep' can be larger than 'max_wait_time'. If that happens using
 267     // an unsigned type would cause an underflow (wait_until_next_sweep becomes a large positive
 268     // value) that disables the intended periodic sweeps.
 269     const int max_wait_time = ReservedCodeCacheSize / (16 * M);
 270     double wait_until_next_sweep = max_wait_time - time_since_last_sweep - CodeCache::reverse_free_ratio();



 271     assert(wait_until_next_sweep <= (double)max_wait_time, "Calculation of code cache sweeper interval is incorrect");
 272 
 273     if ((wait_until_next_sweep <= 0.0) || !CompileBroker::should_compile_new_jobs()) {
 274       _should_sweep = true;
 275     }
 276   }
 277 
 278   if (_should_sweep && _sweep_fractions_left > 0) {
 279     // Only one thread at a time will sweep
 280     jint old = Atomic::cmpxchg( 1, &_sweep_started, 0 );
 281     if (old != 0) {
 282       return;
 283     }
 284 #ifdef ASSERT
 285     if (LogSweeper && _records == NULL) {
 286       // Create the ring buffer for the logging code
 287       _records = NEW_C_HEAP_ARRAY(SweeperRecord, SweeperLogEntries, mtGC);
 288       memset(_records, 0, sizeof(SweeperRecord) * SweeperLogEntries);
 289     }
 290 #endif


 332     _sweep_fractions_left = 1;
 333   }
 334 
 335   // We want to visit all nmethods after NmethodSweepFraction
 336   // invocations so divide the remaining number of nmethods by the
 337   // remaining number of invocations.  This is only an estimate since
 338   // the number of nmethods changes during the sweep so the final
 339   // stage must iterate until it there are no more nmethods.
 340   int todo = (CodeCache::nof_nmethods() - _seen) / _sweep_fractions_left;
 341   int swept_count = 0;
 342 
 343 
 344   assert(!SafepointSynchronize::is_at_safepoint(), "should not be in safepoint when we get here");
 345   assert(!CodeCache_lock->owned_by_self(), "just checking");
 346 
 347   int freed_memory = 0;
 348   {
 349     MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
 350 
 351     // The last invocation iterates until there are no more nmethods
 352     for (int i = 0; (i < todo || _sweep_fractions_left == 1) && _current != NULL; i++) {
 353       swept_count++;
 354       if (SafepointSynchronize::is_synchronizing()) { // Safepoint request
 355         if (PrintMethodFlushing && Verbose) {
 356           tty->print_cr("### Sweep at %d out of %d, invocation: %d, yielding to safepoint", _seen, CodeCache::nof_nmethods(), _sweep_fractions_left);
 357         }
 358         MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
 359 
 360         assert(Thread::current()->is_Java_thread(), "should be java thread");
 361         JavaThread* thread = (JavaThread*)Thread::current();
 362         ThreadBlockInVM tbivm(thread);
 363         thread->java_suspend_self();
 364       }
 365       // Since we will give up the CodeCache_lock, always skip ahead
 366       // to the next nmethod.  Other blobs can be deleted by other
 367       // threads but nmethods are only reclaimed by the sweeper.
 368       nmethod* next = CodeCache::next_nmethod(_current);
 369 
 370       // Now ready to process nmethod and give up CodeCache_lock
 371       {
 372         MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
 373         freed_memory += process_nmethod(_current);
 374       }
 375       _seen++;
 376       _current = next;







 377     }
 378   }
 379 
 380   assert(_sweep_fractions_left > 1 || _current == NULL, "must have scanned the whole cache");
 381 
 382   const Ticks sweep_end_counter = Ticks::now();
 383   const Tickspan sweep_time = sweep_end_counter - sweep_start_counter;
 384   _total_time_sweeping  += sweep_time;
 385   _total_time_this_sweep += sweep_time;
 386   _peak_sweep_fraction_time = MAX2(sweep_time, _peak_sweep_fraction_time);
 387   _total_flushed_size += freed_memory;
 388   _total_nof_methods_reclaimed += _flushed_count;
 389 
 390   EventSweepCodeCache event(UNTIMED);
 391   if (event.should_commit()) {
 392     event.set_starttime(sweep_start_counter);
 393     event.set_endtime(sweep_end_counter);
 394     event.set_sweepIndex(_traversals);
 395     event.set_sweepFractionIndex(NmethodSweepFraction - _sweep_fractions_left + 1);
 396     event.set_sweptCount(swept_count);
 397     event.set_flushedCount(_flushed_count);
 398     event.set_markedCount(_marked_for_reclamation_count);
 399     event.set_zombifiedCount(_zombified_count);
 400     event.commit();


 468   }
 469 };
 470 
 471 void NMethodSweeper::release_nmethod(nmethod *nm) {
 472   // Clean up any CompiledICHolders
 473   {
 474     ResourceMark rm;
 475     MutexLocker ml_patch(CompiledIC_lock);
 476     RelocIterator iter(nm);
 477     while (iter.next()) {
 478       if (iter.type() == relocInfo::virtual_call_type) {
 479         CompiledIC::cleanup_call_site(iter.virtual_call_reloc());
 480       }
 481     }
 482   }
 483 
 484   MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
 485   nm->flush();
 486 }
 487 
 488 int NMethodSweeper::process_nmethod(nmethod *nm) {
 489   assert(!CodeCache_lock->owned_by_self(), "just checking");
 490 
 491   int freed_memory = 0;
 492   // Make sure this nmethod doesn't get unloaded during the scan,
 493   // since safepoints may happen during acquired below locks.
 494   NMethodMarker nmm(nm);
 495   SWEEP(nm);
 496 
 497   // Skip methods that are currently referenced by the VM
 498   if (nm->is_locked_by_vm()) {
 499     // But still remember to clean-up inline caches for alive nmethods
 500     if (nm->is_alive()) {
 501       // Clean inline caches that point to zombie/non-entrant methods
 502       MutexLocker cl(CompiledIC_lock);
 503       nm->cleanup_inline_caches();
 504       SWEEP(nm);
 505     }
 506     return freed_memory;
 507   }
 508 


 560       if (nm->is_compiled_by_c2()) {
 561         _total_nof_c2_methods_reclaimed++;
 562       }
 563       release_nmethod(nm);
 564       _flushed_count++;
 565     } else {
 566       // Code cache state change is tracked in make_zombie()
 567       nm->make_zombie();
 568       _zombified_count++;
 569       SWEEP(nm);
 570     }
 571   } else {
 572     if (UseCodeCacheFlushing) {
 573       if (!nm->is_locked_by_vm() && !nm->is_osr_method() && !nm->is_native_method()) {
 574         // Do not make native methods and OSR-methods not-entrant
 575         nm->dec_hotness_counter();
 576         // Get the initial value of the hotness counter. This value depends on the
 577         // ReservedCodeCacheSize
 578         int reset_val = hotness_counter_reset_val();
 579         int time_since_reset = reset_val - nm->hotness_counter();
 580         double threshold = -reset_val + (CodeCache::reverse_free_ratio() * NmethodSweepActivity);
 581         // The less free space in the code cache we have - the bigger reverse_free_ratio() is.
 582         // I.e., 'threshold' increases with lower available space in the code cache and a higher
 583         // NmethodSweepActivity. If the current hotness counter - which decreases from its initial
 584         // value until it is reset by stack walking - is smaller than the computed threshold, the
 585         // corresponding nmethod is considered for removal.
 586         if ((NmethodSweepActivity > 0) && (nm->hotness_counter() < threshold) && (time_since_reset > 10)) {
 587           // A method is marked as not-entrant if the method is
 588           // 1) 'old enough': nm->hotness_counter() < threshold
 589           // 2) The method was in_use for a minimum amount of time: (time_since_reset > 10)
 590           //    The second condition is necessary if we are dealing with very small code cache
 591           //    sizes (e.g., <10m) and the code cache size is too small to hold all hot methods.
 592           //    The second condition ensures that methods are not immediately made not-entrant
 593           //    after compilation.
 594           nm->make_not_entrant();
 595           // Code cache state change is tracked in make_not_entrant()
 596           if (PrintMethodFlushing && Verbose) {
 597             tty->print_cr("### Nmethod %d/" PTR_FORMAT "made not-entrant: hotness counter %d/%d threshold %f",
 598                           nm->compile_id(), nm, nm->hotness_counter(), reset_val, threshold);
 599           }
 600         }




 110 }
 111 
 112 void NMethodSweeper::record_sweep(nmethod* nm, int line) {
 113   if (_records != NULL) {
 114     _records[_sweep_index].traversal = _traversals;
 115     _records[_sweep_index].traversal_mark = nm->_stack_traversal_mark;
 116     _records[_sweep_index].invocation = _sweep_fractions_left;
 117     _records[_sweep_index].compile_id = nm->compile_id();
 118     _records[_sweep_index].kind = nm->compile_kind();
 119     _records[_sweep_index].state = nm->_state;
 120     _records[_sweep_index].vep = nm->verified_entry_point();
 121     _records[_sweep_index].uep = nm->entry_point();
 122     _records[_sweep_index].line = line;
 123     _sweep_index = (_sweep_index + 1) % SweeperLogEntries;
 124   }
 125 }
 126 #else
 127 #define SWEEP(nm)
 128 #endif
 129 
 130 nmethod* NMethodSweeper::_current_nmethod              = NULL; // Current nmethod
 131 int      NMethodSweeper::_current_type                 = 0;    // Current CodeBlobType
 132 long     NMethodSweeper::_traversals                   = 0;    // Stack scan count, also sweep ID.
 133 long     NMethodSweeper::_total_nof_code_cache_sweeps  = 0;    // Total number of full sweeps of the code cache
 134 long     NMethodSweeper::_time_counter                 = 0;    // Virtual time used to periodically invoke sweeper
 135 long     NMethodSweeper::_last_sweep                   = 0;    // Value of _time_counter when the last sweep happened
 136 int      NMethodSweeper::_seen                         = 0;    // Nof. nmethod we have currently processed in current pass of CodeCache
 137 int      NMethodSweeper::_flushed_count                = 0;    // Nof. nmethods flushed in current sweep
 138 int      NMethodSweeper::_zombified_count              = 0;    // Nof. nmethods made zombie in current sweep
 139 int      NMethodSweeper::_marked_for_reclamation_count = 0;    // Nof. nmethods marked for reclaim in current sweep
 140 
 141 volatile bool NMethodSweeper::_should_sweep            = true; // Indicates if we should invoke the sweeper
 142 volatile int  NMethodSweeper::_sweep_fractions_left    = 0;    // Nof. invocations left until we are completed with this pass
 143 volatile int  NMethodSweeper::_sweep_started           = 0;    // Flag to control conc sweeper
 144 volatile int  NMethodSweeper::_bytes_changed           = 0;    // Counts the total nmethod size if the nmethod changed from:
 145                                                                //   1) alive       -> not_entrant
 146                                                                //   2) not_entrant -> zombie
 147                                                                //   3) zombie      -> marked_for_reclamation
 148 int    NMethodSweeper::_hotness_counter_reset_val       = 0;
 149 
 150 long   NMethodSweeper::_total_nof_methods_reclaimed     = 0;   // Accumulated nof methods flushed
 151 long   NMethodSweeper::_total_nof_c2_methods_reclaimed  = 0;   // Accumulated nof methods flushed
 152 size_t NMethodSweeper::_total_flushed_size              = 0;   // Total number of bytes flushed from the code cache
 153 Tickspan NMethodSweeper::_total_time_sweeping;                 // Accumulated time sweeping
 154 Tickspan NMethodSweeper::_total_time_this_sweep;               // Total time this sweep
 155 Tickspan NMethodSweeper::_peak_sweep_time;                     // Peak time for a full sweep
 156 Tickspan NMethodSweeper::_peak_sweep_fraction_time;            // Peak time sweeping one fraction
 157 
 158 

 159 class MarkActivationClosure: public CodeBlobClosure {
 160 public:
 161   virtual void do_code_blob(CodeBlob* cb) {
 162     assert(cb->is_nmethod(), "CodeBlob should be nmethod");
 163     nmethod* nm = (nmethod*)cb;
 164     nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val());
 165     // If we see an activation belonging to a non_entrant nmethod, we mark it.
 166     if (nm->is_not_entrant()) {
 167       nm->mark_as_seen_on_stack();
 168     }
 169   }

 170 };
 171 static MarkActivationClosure mark_activation_closure;
 172 
 173 class SetHotnessClosure: public CodeBlobClosure {
 174 public:
 175   virtual void do_code_blob(CodeBlob* cb) {
 176     assert(cb->is_nmethod(), "CodeBlob should be nmethod");
 177     nmethod* nm = (nmethod*)cb;
 178     nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val());
 179   }

 180 };
 181 static SetHotnessClosure set_hotness_closure;
 182 
 183 
 184 int NMethodSweeper::hotness_counter_reset_val() {
 185   if (_hotness_counter_reset_val == 0) {
 186     _hotness_counter_reset_val = (ReservedCodeCacheSize < M) ? 1 : (ReservedCodeCacheSize / M) * 2;
 187   }
 188   return _hotness_counter_reset_val;
 189 }
 190 bool NMethodSweeper::sweep_in_progress() {
 191   return (_current_nmethod != NULL);
 192 }
 193 
 194 // Scans the stacks of all Java threads and marks activations of not-entrant methods.
 195 // No need to synchronize access, since 'mark_active_nmethods' is always executed at a
 196 // safepoint.
 197 void NMethodSweeper::mark_active_nmethods() {
 198   assert(SafepointSynchronize::is_at_safepoint(), "must be executed at a safepoint");
 199   // If we do not want to reclaim not-entrant or zombie methods there is no need
 200   // to scan stacks
 201   if (!MethodFlushing) {
 202     return;
 203   }
 204 
 205   // Increase time so that we can estimate when to invoke the sweeper again.
 206   _time_counter++;
 207 
 208   // Check for restart
 209   assert(CodeCache::find_blob_unsafe(_current_nmethod) == _current_nmethod, "Sweeper nmethod cached state invalid");
 210   if (!sweep_in_progress()) {
 211     _seen = 0;
 212     _sweep_fractions_left = NmethodSweepFraction;
 213     _current_nmethod = (nmethod*)CodeCache::first_blob(CodeBlobType::MethodNonProfiled);
 214     _current_type = CodeBlobType::MethodNonProfiled;
 215     _traversals += 1;
 216     _total_time_this_sweep = Tickspan();
 217 
 218     if (PrintMethodFlushing) {
 219       tty->print_cr("### Sweep: stack traversal %d", _traversals);
 220     }
 221     Threads::nmethods_do(&mark_activation_closure);
 222 
 223   } else {
 224     // Only set hotness counter
 225     Threads::nmethods_do(&set_hotness_closure);
 226   }
 227 
 228   OrderAccess::storestore();
 229 }
 230 /**
 231  * This function invokes the sweeper if at least one of the three conditions is met:
 232  *    (1) The code cache is getting full
 233  *    (2) There are sufficient state changes in/since the last sweep.
 234  *    (3) We have not been sweeping for 'some time'


 249   // the formula considers how much space in the code cache is currently used. Here are
 250   // some examples that will (hopefully) help in understanding.
 251   //
 252   // Small ReservedCodeCacheSizes:  (e.g., < 16M) We invoke the sweeper every time, since
 253   //                                              the result of the division is 0. This
 254   //                                              keeps the used code cache size small
 255   //                                              (important for embedded Java)
 256   // Large ReservedCodeCacheSize :  (e.g., 256M + code cache is 10% full). The formula
 257   //                                              computes: (256 / 16) - 1 = 15
 258   //                                              As a result, we invoke the sweeper after
 259   //                                              15 invocations of 'mark_active_nmethods.
 260   // Large ReservedCodeCacheSize:   (e.g., 256M + code Cache is 90% full). The formula
 261   //                                              computes: (256 / 16) - 10 = 6.
 262   if (!_should_sweep) {
 263     const int time_since_last_sweep = _time_counter - _last_sweep;
 264     // ReservedCodeCacheSize has an 'unsigned' type. We need a 'signed' type for max_wait_time,
 265     // since 'time_since_last_sweep' can be larger than 'max_wait_time'. If that happens using
 266     // an unsigned type would cause an underflow (wait_until_next_sweep becomes a large positive
 267     // value) that disables the intended periodic sweeps.
 268     const int max_wait_time = ReservedCodeCacheSize / (16 * M);
 269     // Use only signed types
 270     double wait_until_next_sweep = max_wait_time - time_since_last_sweep -
 271         MAX2(CodeCache::reverse_free_ratio(CodeBlobType::MethodProfiled),
 272              CodeCache::reverse_free_ratio(CodeBlobType::MethodNonProfiled));
 273     assert(wait_until_next_sweep <= (double)max_wait_time, "Calculation of code cache sweeper interval is incorrect");
 274 
 275     if ((wait_until_next_sweep <= 0.0) || !CompileBroker::should_compile_new_jobs()) {
 276       _should_sweep = true;
 277     }
 278   }
 279 
 280   if (_should_sweep && _sweep_fractions_left > 0) {
 281     // Only one thread at a time will sweep
 282     jint old = Atomic::cmpxchg( 1, &_sweep_started, 0 );
 283     if (old != 0) {
 284       return;
 285     }
 286 #ifdef ASSERT
 287     if (LogSweeper && _records == NULL) {
 288       // Create the ring buffer for the logging code
 289       _records = NEW_C_HEAP_ARRAY(SweeperRecord, SweeperLogEntries, mtGC);
 290       memset(_records, 0, sizeof(SweeperRecord) * SweeperLogEntries);
 291     }
 292 #endif


 334     _sweep_fractions_left = 1;
 335   }
 336 
 337   // We want to visit all nmethods after NmethodSweepFraction
 338   // invocations so divide the remaining number of nmethods by the
 339   // remaining number of invocations.  This is only an estimate since
 340   // the number of nmethods changes during the sweep so the final
 341   // stage must iterate until it there are no more nmethods.
 342   int todo = (CodeCache::nof_nmethods() - _seen) / _sweep_fractions_left;
 343   int swept_count = 0;
 344 
 345 
 346   assert(!SafepointSynchronize::is_at_safepoint(), "should not be in safepoint when we get here");
 347   assert(!CodeCache_lock->owned_by_self(), "just checking");
 348 
 349   int freed_memory = 0;
 350   {
 351     MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
 352 
 353     // The last invocation iterates until there are no more nmethods
 354     while ((swept_count < todo || _sweep_fractions_left == 1) && _current_nmethod != NULL) {
 355       swept_count++;
 356       if (SafepointSynchronize::is_synchronizing()) { // Safepoint request
 357         if (PrintMethodFlushing && Verbose) {
 358           tty->print_cr("### Sweep at %d out of %d, invocation: %d, yielding to safepoint", _seen, CodeCache::nof_nmethods(), _sweep_fractions_left);
 359         }
 360         MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
 361 
 362         assert(Thread::current()->is_Java_thread(), "should be java thread");
 363         JavaThread* thread = (JavaThread*)Thread::current();
 364         ThreadBlockInVM tbivm(thread);
 365         thread->java_suspend_self();
 366       }
 367       // Since we will give up the CodeCache_lock, always skip ahead
 368       // to the next nmethod.  Other blobs can be deleted by other
 369       // threads but nmethods are only reclaimed by the sweeper.
 370       nmethod* next = (nmethod*)CodeCache::next_blob(_current_nmethod, _current_type);
 371 
 372       // Now ready to process nmethod and give up CodeCache_lock
 373       {
 374         MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
 375         freed_memory += process_nmethod(_current_nmethod, _current_type);
 376       }
 377       _seen++;
 378 
 379       while (next == NULL && _current_type < CodeBlobType::MethodProfiled) {
 380         // We reached the last method of the type
 381         // Go to next type that has methods available
 382         _current_type++;
 383         next = (nmethod*)CodeCache::first_blob(_current_type);
 384       }
 385       _current_nmethod = next;
 386     }
 387   }
 388 
 389   assert(_sweep_fractions_left > 1 || _current_nmethod == NULL, "must have scanned the whole cache");
 390 
 391   const Ticks sweep_end_counter = Ticks::now();
 392   const Tickspan sweep_time = sweep_end_counter - sweep_start_counter;
 393   _total_time_sweeping  += sweep_time;
 394   _total_time_this_sweep += sweep_time;
 395   _peak_sweep_fraction_time = MAX2(sweep_time, _peak_sweep_fraction_time);
 396   _total_flushed_size += freed_memory;
 397   _total_nof_methods_reclaimed += _flushed_count;
 398 
 399   EventSweepCodeCache event(UNTIMED);
 400   if (event.should_commit()) {
 401     event.set_starttime(sweep_start_counter);
 402     event.set_endtime(sweep_end_counter);
 403     event.set_sweepIndex(_traversals);
 404     event.set_sweepFractionIndex(NmethodSweepFraction - _sweep_fractions_left + 1);
 405     event.set_sweptCount(swept_count);
 406     event.set_flushedCount(_flushed_count);
 407     event.set_markedCount(_marked_for_reclamation_count);
 408     event.set_zombifiedCount(_zombified_count);
 409     event.commit();


 477   }
 478 };
 479 
 480 void NMethodSweeper::release_nmethod(nmethod *nm) {
 481   // Clean up any CompiledICHolders
 482   {
 483     ResourceMark rm;
 484     MutexLocker ml_patch(CompiledIC_lock);
 485     RelocIterator iter(nm);
 486     while (iter.next()) {
 487       if (iter.type() == relocInfo::virtual_call_type) {
 488         CompiledIC::cleanup_call_site(iter.virtual_call_reloc());
 489       }
 490     }
 491   }
 492 
 493   MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
 494   nm->flush();
 495 }
 496 
 497 int NMethodSweeper::process_nmethod(nmethod *nm, int code_blob_type) {
 498   assert(!CodeCache_lock->owned_by_self(), "just checking");
 499 
 500   int freed_memory = 0;
 501   // Make sure this nmethod doesn't get unloaded during the scan,
 502   // since safepoints may happen during acquired below locks.
 503   NMethodMarker nmm(nm);
 504   SWEEP(nm);
 505 
 506   // Skip methods that are currently referenced by the VM
 507   if (nm->is_locked_by_vm()) {
 508     // But still remember to clean-up inline caches for alive nmethods
 509     if (nm->is_alive()) {
 510       // Clean inline caches that point to zombie/non-entrant methods
 511       MutexLocker cl(CompiledIC_lock);
 512       nm->cleanup_inline_caches();
 513       SWEEP(nm);
 514     }
 515     return freed_memory;
 516   }
 517 


 569       if (nm->is_compiled_by_c2()) {
 570         _total_nof_c2_methods_reclaimed++;
 571       }
 572       release_nmethod(nm);
 573       _flushed_count++;
 574     } else {
 575       // Code cache state change is tracked in make_zombie()
 576       nm->make_zombie();
 577       _zombified_count++;
 578       SWEEP(nm);
 579     }
 580   } else {
 581     if (UseCodeCacheFlushing) {
 582       if (!nm->is_locked_by_vm() && !nm->is_osr_method() && !nm->is_native_method()) {
 583         // Do not make native methods and OSR-methods not-entrant
 584         nm->dec_hotness_counter();
 585         // Get the initial value of the hotness counter. This value depends on the
 586         // ReservedCodeCacheSize
 587         int reset_val = hotness_counter_reset_val();
 588         int time_since_reset = reset_val - nm->hotness_counter();
 589         double threshold = -reset_val + (CodeCache::reverse_free_ratio(code_blob_type) * NmethodSweepActivity);
 590         // The less free space in the code cache we have - the bigger reverse_free_ratio() is.
 591         // I.e., 'threshold' increases with lower available space in the code cache and a higher
 592         // NmethodSweepActivity. If the current hotness counter - which decreases from its initial
 593         // value until it is reset by stack walking - is smaller than the computed threshold, the
 594         // corresponding nmethod is considered for removal.
 595         if ((NmethodSweepActivity > 0) && (nm->hotness_counter() < threshold) && (time_since_reset > 10)) {
 596           // A method is marked as not-entrant if the method is
 597           // 1) 'old enough': nm->hotness_counter() < threshold
 598           // 2) The method was in_use for a minimum amount of time: (time_since_reset > 10)
 599           //    The second condition is necessary if we are dealing with very small code cache
 600           //    sizes (e.g., <10m) and the code cache size is too small to hold all hot methods.
 601           //    The second condition ensures that methods are not immediately made not-entrant
 602           //    after compilation.
 603           nm->make_not_entrant();
 604           // Code cache state change is tracked in make_not_entrant()
 605           if (PrintMethodFlushing && Verbose) {
 606             tty->print_cr("### Nmethod %d/" PTR_FORMAT "made not-entrant: hotness counter %d/%d threshold %f",
 607                           nm->compile_id(), nm, nm->hotness_counter(), reset_val, threshold);
 608           }
 609         }


src/share/vm/runtime/sweeper.cpp
Index Unified diffs Context diffs Sdiffs Patch New Old Previous File Next File