rev 57079 : imported patch 8234796

   1 /*
   2  * Copyright (c) 1997, 2019, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "code/codeCache.hpp"
  27 #include "code/compiledIC.hpp"
  28 #include "code/icBuffer.hpp"
  29 #include "code/nmethod.hpp"
  30 #include "compiler/compileBroker.hpp"
  31 #include "gc/shared/collectedHeap.hpp"
  32 #include "gc/shared/workgroup.hpp"
  33 #include "jfr/jfrEvents.hpp"
  34 #include "logging/log.hpp"
  35 #include "logging/logStream.hpp"
  36 #include "memory/allocation.inline.hpp"
  37 #include "memory/resourceArea.hpp"
  38 #include "memory/universe.hpp"
  39 #include "oops/method.hpp"
  40 #include "runtime/atomic.hpp"
  41 #include "runtime/interfaceSupport.inline.hpp"
  42 #include "runtime/handshake.hpp"
  43 #include "runtime/mutexLocker.hpp"
  44 #include "runtime/orderAccess.hpp"
  45 #include "runtime/os.hpp"
  46 #include "runtime/sweeper.hpp"
  47 #include "runtime/thread.inline.hpp"
  48 #include "runtime/vmOperations.hpp"
  49 #include "runtime/vmThread.hpp"
  50 #include "utilities/events.hpp"
  51 #include "utilities/xmlstream.hpp"
  52 
  53 #ifdef ASSERT
  54 
  55 #define SWEEP(nm) record_sweep(nm, __LINE__)
  56 // Sweeper logging code
  57 class SweeperRecord {
  58  public:
  59   int traversal;
  60   int compile_id;
  61   long traversal_mark;
  62   int state;
  63   const char* kind;
  64   address vep;
  65   address uep;
  66   int line;
  67 
  68   void print() {
  69       tty->print_cr("traversal = %d compile_id = %d %s uep = " PTR_FORMAT " vep = "
  70                     PTR_FORMAT " state = %d traversal_mark %ld line = %d",
  71                     traversal,
  72                     compile_id,
  73                     kind == NULL ? "" : kind,
  74                     p2i(uep),
  75                     p2i(vep),
  76                     state,
  77                     traversal_mark,
  78                     line);
  79   }
  80 };
  81 
  82 static int _sweep_index = 0;
  83 static SweeperRecord* _records = NULL;
  84 
  85 void NMethodSweeper::report_events(int id, address entry) {
  86   if (_records != NULL) {
  87     for (int i = _sweep_index; i < SweeperLogEntries; i++) {
  88       if (_records[i].uep == entry ||
  89           _records[i].vep == entry ||
  90           _records[i].compile_id == id) {
  91         _records[i].print();
  92       }
  93     }
  94     for (int i = 0; i < _sweep_index; i++) {
  95       if (_records[i].uep == entry ||
  96           _records[i].vep == entry ||
  97           _records[i].compile_id == id) {
  98         _records[i].print();
  99       }
 100     }
 101   }
 102 }
 103 
 104 void NMethodSweeper::report_events() {
 105   if (_records != NULL) {
 106     for (int i = _sweep_index; i < SweeperLogEntries; i++) {
 107       // skip empty records
 108       if (_records[i].vep == NULL) continue;
 109       _records[i].print();
 110     }
 111     for (int i = 0; i < _sweep_index; i++) {
 112       // skip empty records
 113       if (_records[i].vep == NULL) continue;
 114       _records[i].print();
 115     }
 116   }
 117 }
 118 
 119 void NMethodSweeper::record_sweep(CompiledMethod* nm, int line) {
 120   if (_records != NULL) {
 121     _records[_sweep_index].traversal = _traversals;
 122     _records[_sweep_index].traversal_mark = nm->is_nmethod() ? ((nmethod*)nm)->stack_traversal_mark() : 0;
 123     _records[_sweep_index].compile_id = nm->compile_id();
 124     _records[_sweep_index].kind = nm->compile_kind();
 125     _records[_sweep_index].state = nm->get_state();
 126     _records[_sweep_index].vep = nm->verified_entry_point();
 127     _records[_sweep_index].uep = nm->entry_point();
 128     _records[_sweep_index].line = line;
 129     _sweep_index = (_sweep_index + 1) % SweeperLogEntries;
 130   }
 131 }
 132 
 133 void NMethodSweeper::init_sweeper_log() {
 134  if (LogSweeper && _records == NULL) {
 135    // Create the ring buffer for the logging code
 136    _records = NEW_C_HEAP_ARRAY(SweeperRecord, SweeperLogEntries, mtGC);
 137    memset(_records, 0, sizeof(SweeperRecord) * SweeperLogEntries);
 138   }
 139 }
 140 #else
 141 #define SWEEP(nm)
 142 #endif
 143 
 144 CompiledMethodIterator NMethodSweeper::_current(CompiledMethodIterator::all_blobs); // Current compiled method
 145 long     NMethodSweeper::_traversals                   = 0;    // Stack scan count, also sweep ID.
 146 long     NMethodSweeper::_total_nof_code_cache_sweeps  = 0;    // Total number of full sweeps of the code cache
 147 long     NMethodSweeper::_time_counter                 = 0;    // Virtual time used to periodically invoke sweeper
 148 long     NMethodSweeper::_last_sweep                   = 0;    // Value of _time_counter when the last sweep happened
 149 int      NMethodSweeper::_seen                         = 0;    // Nof. nmethod we have currently processed in current pass of CodeCache
 150 
 151 volatile bool NMethodSweeper::_should_sweep            = false;// Indicates if we should invoke the sweeper
 152 volatile bool NMethodSweeper::_force_sweep             = false;// Indicates if we should force a sweep
 153 volatile int  NMethodSweeper::_bytes_changed           = 0;    // Counts the total nmethod size if the nmethod changed from:
 154                                                                //   1) alive       -> not_entrant
 155                                                                //   2) not_entrant -> zombie
 156 int    NMethodSweeper::_hotness_counter_reset_val       = 0;
 157 
 158 long   NMethodSweeper::_total_nof_methods_reclaimed     = 0;   // Accumulated nof methods flushed
 159 long   NMethodSweeper::_total_nof_c2_methods_reclaimed  = 0;   // Accumulated nof methods flushed
 160 size_t NMethodSweeper::_total_flushed_size              = 0;   // Total number of bytes flushed from the code cache
 161 Tickspan NMethodSweeper::_total_time_sweeping;                 // Accumulated time sweeping
 162 Tickspan NMethodSweeper::_total_time_this_sweep;               // Total time this sweep
 163 Tickspan NMethodSweeper::_peak_sweep_time;                     // Peak time for a full sweep
 164 Tickspan NMethodSweeper::_peak_sweep_fraction_time;            // Peak time sweeping one fraction
 165 
 166 class MarkActivationClosure: public CodeBlobClosure {
 167 public:
 168   virtual void do_code_blob(CodeBlob* cb) {
 169     assert(cb->is_nmethod(), "CodeBlob should be nmethod");
 170     nmethod* nm = (nmethod*)cb;
 171     nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val());
 172     // If we see an activation belonging to a non_entrant nmethod, we mark it.
 173     if (nm->is_not_entrant()) {
 174       nm->mark_as_seen_on_stack();
 175     }
 176   }
 177 };
 178 static MarkActivationClosure mark_activation_closure;
 179 
 180 class SetHotnessClosure: public CodeBlobClosure {
 181 public:
 182   virtual void do_code_blob(CodeBlob* cb) {
 183     assert(cb->is_nmethod(), "CodeBlob should be nmethod");
 184     nmethod* nm = (nmethod*)cb;
 185     nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val());
 186   }
 187 };
 188 static SetHotnessClosure set_hotness_closure;
 189 
 190 
 191 int NMethodSweeper::hotness_counter_reset_val() {
 192   if (_hotness_counter_reset_val == 0) {
 193     _hotness_counter_reset_val = (ReservedCodeCacheSize < M) ? 1 : (ReservedCodeCacheSize / M) * 2;
 194   }
 195   return _hotness_counter_reset_val;
 196 }
 197 bool NMethodSweeper::wait_for_stack_scanning() {
 198   return _current.end();
 199 }
 200 
 201 class NMethodMarkingThreadClosure : public ThreadClosure {
 202 private:
 203   CodeBlobClosure* _cl;
 204 public:
 205   NMethodMarkingThreadClosure(CodeBlobClosure* cl) : _cl(cl) {}
 206   void do_thread(Thread* thread) {
 207     if (thread->is_Java_thread() && ! thread->is_Code_cache_sweeper_thread()) {
 208       JavaThread* jt = (JavaThread*) thread;
 209       jt->nmethods_do(_cl);
 210     }
 211   }
 212 };
 213 
 214 class NMethodMarkingTask : public AbstractGangTask {
 215 private:
 216   NMethodMarkingThreadClosure* _cl;
 217 public:
 218   NMethodMarkingTask(NMethodMarkingThreadClosure* cl) :
 219     AbstractGangTask("Parallel NMethod Marking"),
 220     _cl(cl) {
 221     Threads::change_thread_claim_token();
 222   }
 223 
 224   ~NMethodMarkingTask() {
 225     Threads::assert_all_threads_claimed();
 226   }
 227 
 228   void work(uint worker_id) {
 229     Threads::possibly_parallel_threads_do(true, _cl);
 230   }
 231 };
 232 
 233 /**
 234   * Scans the stacks of all Java threads and marks activations of not-entrant methods.
 235   * No need to synchronize access, since 'mark_active_nmethods' is always executed at a
 236   * safepoint.
 237   */
 238 void NMethodSweeper::mark_active_nmethods() {
 239   CodeBlobClosure* cl = prepare_mark_active_nmethods();
 240   if (cl != NULL) {
 241     WorkGang* workers = Universe::heap()->get_safepoint_workers();
 242     if (workers != NULL) {
 243       NMethodMarkingThreadClosure tcl(cl);
 244       NMethodMarkingTask task(&tcl);
 245       workers->run_task(&task);
 246     } else {
 247       Threads::nmethods_do(cl);
 248     }
 249   }
 250 }
 251 
 252 CodeBlobClosure* NMethodSweeper::prepare_mark_active_nmethods() {
 253 #ifdef ASSERT
 254   if (ThreadLocalHandshakes) {
 255     assert(Thread::current()->is_Code_cache_sweeper_thread(), "must be executed under CodeCache_lock and in sweeper thread");
 256     assert_lock_strong(CodeCache_lock);
 257   } else {
 258     assert(SafepointSynchronize::is_at_safepoint(), "must be executed at a safepoint");
 259   }
 260 #endif
 261 
 262   // If we do not want to reclaim not-entrant or zombie methods there is no need
 263   // to scan stacks
 264   if (!MethodFlushing) {
 265     return NULL;
 266   }
 267 
 268   // Increase time so that we can estimate when to invoke the sweeper again.
 269   _time_counter++;
 270 
 271   // Check for restart
 272   assert(_current.method() == NULL, "should only happen between sweeper cycles");
 273   assert(wait_for_stack_scanning(), "should only happen between sweeper cycles");
 274 
 275   _seen = 0;
 276   _current = CompiledMethodIterator(CompiledMethodIterator::all_blobs);
 277   // Initialize to first nmethod
 278   _current.next();
 279   _traversals += 1;
 280   _total_time_this_sweep = Tickspan();
 281 
 282   if (PrintMethodFlushing) {
 283     tty->print_cr("### Sweep: stack traversal %ld", _traversals);
 284   }
 285   return &mark_activation_closure;
 286 }
 287 
 288 CodeBlobClosure* NMethodSweeper::prepare_reset_hotness_counters() {
 289   assert(SafepointSynchronize::is_at_safepoint(), "must be executed at a safepoint");
 290 
 291   // If we do not want to reclaim not-entrant or zombie methods there is no need
 292   // to scan stacks
 293   if (!MethodFlushing) {
 294     return NULL;
 295   }
 296 
 297   // Increase time so that we can estimate when to invoke the sweeper again.
 298   _time_counter++;
 299 
 300   // Check for restart
 301   if (_current.method() != NULL) {
 302     if (_current.method()->is_nmethod()) {
 303       assert(CodeCache::find_blob_unsafe(_current.method()) == _current.method(), "Sweeper nmethod cached state invalid");
 304     } else if (_current.method()->is_aot()) {
 305       assert(CodeCache::find_blob_unsafe(_current.method()->code_begin()) == _current.method(), "Sweeper AOT method cached state invalid");
 306     } else {
 307       ShouldNotReachHere();
 308     }
 309   }
 310 
 311   return &set_hotness_closure;
 312 }
 313 









 314 /**
 315   * This function triggers a VM operation that does stack scanning of active
 316   * methods. Stack scanning is mandatory for the sweeper to make progress.
 317   */
 318 void NMethodSweeper::do_stack_scanning() {
 319   assert(!CodeCache_lock->owned_by_self(), "just checking");
 320   if (wait_for_stack_scanning()) {
 321     if (ThreadLocalHandshakes) {
 322       CodeBlobClosure* code_cl;
 323       {
 324         MutexLocker ccl(CodeCache_lock, Mutex::_no_safepoint_check_flag);
 325         code_cl = prepare_mark_active_nmethods();
 326       }
 327       if (code_cl != NULL) {
 328         NMethodMarkingThreadClosure tcl(code_cl);
 329         Handshake::execute(&tcl);

 330       }
 331     } else {
 332       VM_MarkActiveNMethods op;
 333       VMThread::execute(&op);
 334     }
 335   }
 336 }
 337 
 338 void NMethodSweeper::sweeper_loop() {
 339   bool timeout;
 340   while (true) {
 341     {
 342       ThreadBlockInVM tbivm(JavaThread::current());
 343       MonitorLocker waiter(CodeCache_lock, Mutex::_no_safepoint_check_flag);
 344       const long wait_time = 60*60*24 * 1000;
 345       timeout = waiter.wait(wait_time);
 346     }
 347     if (!timeout) {
 348       possibly_sweep();
 349     }
 350   }
 351 }
 352 
 353 /**
 354   * Wakes up the sweeper thread to possibly sweep.
 355   */
 356 void NMethodSweeper::notify(int code_blob_type) {
 357   // Makes sure that we do not invoke the sweeper too often during startup.
 358   double start_threshold = 100.0 / (double)StartAggressiveSweepingAt;
 359   double aggressive_sweep_threshold = MIN2(start_threshold, 1.1);
 360   if (CodeCache::reverse_free_ratio(code_blob_type) >= aggressive_sweep_threshold) {
 361     assert_locked_or_safepoint(CodeCache_lock);
 362     CodeCache_lock->notify();
 363   }
 364 }
 365 
 366 /**
 367   * Wakes up the sweeper thread and forces a sweep. Blocks until it finished.
 368   */
 369 void NMethodSweeper::force_sweep() {
 370   ThreadBlockInVM tbivm(JavaThread::current());
 371   MonitorLocker waiter(CodeCache_lock, Mutex::_no_safepoint_check_flag);
 372   // Request forced sweep
 373   _force_sweep = true;
 374   while (_force_sweep) {
 375     // Notify sweeper that we want to force a sweep and wait for completion.
 376     // In case a sweep currently takes place we timeout and try again because
 377     // we want to enforce a full sweep.
 378     CodeCache_lock->notify();
 379     waiter.wait(1000);
 380   }
 381 }
 382 
 383 /**
 384  * Handle a safepoint request
 385  */
 386 void NMethodSweeper::handle_safepoint_request() {
 387   JavaThread* thread = JavaThread::current();
 388   if (SafepointMechanism::should_block(thread)) {
 389     if (PrintMethodFlushing && Verbose) {
 390       tty->print_cr("### Sweep at %d out of %d, yielding to safepoint", _seen, CodeCache::nmethod_count());
 391     }
 392     MutexUnlocker mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
 393 
 394     ThreadBlockInVM tbivm(thread);
 395     thread->java_suspend_self();
 396   }
 397 }
 398 
 399 /**
 400  * This function invokes the sweeper if at least one of the three conditions is met:
 401  *    (1) The code cache is getting full
 402  *    (2) There are sufficient state changes in/since the last sweep.
 403  *    (3) We have not been sweeping for 'some time'
 404  */
 405 void NMethodSweeper::possibly_sweep() {
 406   assert(JavaThread::current()->thread_state() == _thread_in_vm, "must run in vm mode");
 407   // If there was no state change while nmethod sweeping, 'should_sweep' will be false.
 408   // This is one of the two places where should_sweep can be set to true. The general
 409   // idea is as follows: If there is enough free space in the code cache, there is no
 410   // need to invoke the sweeper. The following formula (which determines whether to invoke
 411   // the sweeper or not) depends on the assumption that for larger ReservedCodeCacheSizes
 412   // we need less frequent sweeps than for smaller ReservedCodecCacheSizes. Furthermore,
 413   // the formula considers how much space in the code cache is currently used. Here are
 414   // some examples that will (hopefully) help in understanding.
 415   //
 416   // Small ReservedCodeCacheSizes:  (e.g., < 16M) We invoke the sweeper every time, since
 417   //                                              the result of the division is 0. This
 418   //                                              keeps the used code cache size small
 419   //                                              (important for embedded Java)
 420   // Large ReservedCodeCacheSize :  (e.g., 256M + code cache is 10% full). The formula
 421   //                                              computes: (256 / 16) - 1 = 15
 422   //                                              As a result, we invoke the sweeper after
 423   //                                              15 invocations of 'mark_active_nmethods.
 424   // Large ReservedCodeCacheSize:   (e.g., 256M + code Cache is 90% full). The formula
 425   //                                              computes: (256 / 16) - 10 = 6.
 426   if (!_should_sweep) {
 427     const int time_since_last_sweep = _time_counter - _last_sweep;
 428     // ReservedCodeCacheSize has an 'unsigned' type. We need a 'signed' type for max_wait_time,
 429     // since 'time_since_last_sweep' can be larger than 'max_wait_time'. If that happens using
 430     // an unsigned type would cause an underflow (wait_until_next_sweep becomes a large positive
 431     // value) that disables the intended periodic sweeps.
 432     const int max_wait_time = ReservedCodeCacheSize / (16 * M);
 433     double wait_until_next_sweep = max_wait_time - time_since_last_sweep -
 434         MAX2(CodeCache::reverse_free_ratio(CodeBlobType::MethodProfiled),
 435              CodeCache::reverse_free_ratio(CodeBlobType::MethodNonProfiled));
 436     assert(wait_until_next_sweep <= (double)max_wait_time, "Calculation of code cache sweeper interval is incorrect");
 437 
 438     if ((wait_until_next_sweep <= 0.0) || !CompileBroker::should_compile_new_jobs()) {
 439       _should_sweep = true;
 440     }
 441   }
 442 
 443   // Remember if this was a forced sweep
 444   bool forced = _force_sweep;
 445 
 446   // Force stack scanning if there is only 10% free space in the code cache.
 447   // We force stack scanning only if the non-profiled code heap gets full, since critical
 448   // allocations go to the non-profiled heap and we must be make sure that there is
 449   // enough space.
 450   double free_percent = 1 / CodeCache::reverse_free_ratio(CodeBlobType::MethodNonProfiled) * 100;
 451   if (free_percent <= StartAggressiveSweepingAt || forced || _should_sweep) {
 452     do_stack_scanning();
 453   }
 454 
 455   if (_should_sweep || forced) {
 456     init_sweeper_log();
 457     sweep_code_cache();
 458   }
 459 
 460   // We are done with sweeping the code cache once.
 461   _total_nof_code_cache_sweeps++;
 462   _last_sweep = _time_counter;
 463   // Reset flag; temporarily disables sweeper
 464   _should_sweep = false;
 465   // If there was enough state change, 'possibly_enable_sweeper()'
 466   // sets '_should_sweep' to true
 467   possibly_enable_sweeper();
 468   // Reset _bytes_changed only if there was enough state change. _bytes_changed
 469   // can further increase by calls to 'report_state_change'.
 470   if (_should_sweep) {
 471     _bytes_changed = 0;
 472   }
 473 
 474   if (forced) {
 475     // Notify requester that forced sweep finished
 476     assert(_force_sweep, "Should be a forced sweep");
 477     MutexLocker mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
 478     _force_sweep = false;
 479     CodeCache_lock->notify();
 480   }
 481 }
 482 
 483 static void post_sweep_event(EventSweepCodeCache* event,
 484                              const Ticks& start,
 485                              const Ticks& end,
 486                              s4 traversals,
 487                              int swept,
 488                              int flushed,
 489                              int zombified) {
 490   assert(event != NULL, "invariant");
 491   assert(event->should_commit(), "invariant");
 492   event->set_starttime(start);
 493   event->set_endtime(end);
 494   event->set_sweepId(traversals);
 495   event->set_sweptCount(swept);
 496   event->set_flushedCount(flushed);
 497   event->set_zombifiedCount(zombified);
 498   event->commit();
 499 }
 500 
 501 void NMethodSweeper::sweep_code_cache() {
 502   ResourceMark rm;
 503   Ticks sweep_start_counter = Ticks::now();
 504 
 505   log_debug(codecache, sweep, start)("CodeCache flushing");
 506 
 507   int flushed_count                = 0;
 508   int zombified_count              = 0;
 509   int flushed_c2_count     = 0;
 510 
 511   if (PrintMethodFlushing && Verbose) {
 512     tty->print_cr("### Sweep at %d out of %d", _seen, CodeCache::nmethod_count());
 513   }
 514 
 515   int swept_count = 0;
 516   assert(!SafepointSynchronize::is_at_safepoint(), "should not be in safepoint when we get here");
 517   assert(!CodeCache_lock->owned_by_self(), "just checking");
 518 
 519   int freed_memory = 0;
 520   {
 521     MutexLocker mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
 522 
 523     while (!_current.end()) {
 524       swept_count++;
 525       // Since we will give up the CodeCache_lock, always skip ahead
 526       // to the next nmethod.  Other blobs can be deleted by other
 527       // threads but nmethods are only reclaimed by the sweeper.
 528       CompiledMethod* nm = _current.method();
 529       _current.next();
 530 
 531       // Now ready to process nmethod and give up CodeCache_lock
 532       {
 533         MutexUnlocker mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
 534         // Save information before potentially flushing the nmethod
 535         // Only flushing nmethods so size only matters for them.
 536         int size = nm->is_nmethod() ? ((nmethod*)nm)->total_size() : 0;
 537         bool is_c2_method = nm->is_compiled_by_c2();
 538         bool is_osr = nm->is_osr_method();
 539         int compile_id = nm->compile_id();
 540         intptr_t address = p2i(nm);
 541         const char* state_before = nm->state();
 542         const char* state_after = "";
 543 
 544         MethodStateChange type = process_compiled_method(nm);
 545         switch (type) {
 546           case Flushed:
 547             state_after = "flushed";
 548             freed_memory += size;
 549             ++flushed_count;
 550             if (is_c2_method) {
 551               ++flushed_c2_count;
 552             }
 553             break;
 554           case MadeZombie:
 555             state_after = "made zombie";
 556             ++zombified_count;
 557             break;
 558           case None:
 559             break;
 560           default:
 561            ShouldNotReachHere();
 562         }
 563         if (PrintMethodFlushing && Verbose && type != None) {
 564           tty->print_cr("### %s nmethod %3d/" PTR_FORMAT " (%s) %s", is_osr ? "osr" : "", compile_id, address, state_before, state_after);
 565         }
 566       }
 567 
 568       _seen++;
 569       handle_safepoint_request();
 570     }
 571   }
 572 
 573   assert(_current.end(), "must have scanned the whole cache");
 574 
 575   const Ticks sweep_end_counter = Ticks::now();
 576   const Tickspan sweep_time = sweep_end_counter - sweep_start_counter;
 577   {
 578     MutexLocker mu(NMethodSweeperStats_lock, Mutex::_no_safepoint_check_flag);
 579     _total_time_sweeping  += sweep_time;
 580     _total_time_this_sweep += sweep_time;
 581     _peak_sweep_fraction_time = MAX2(sweep_time, _peak_sweep_fraction_time);
 582     _total_flushed_size += freed_memory;
 583     _total_nof_methods_reclaimed += flushed_count;
 584     _total_nof_c2_methods_reclaimed += flushed_c2_count;
 585     _peak_sweep_time = MAX2(_peak_sweep_time, _total_time_this_sweep);
 586   }
 587 
 588   EventSweepCodeCache event(UNTIMED);
 589   if (event.should_commit()) {
 590     post_sweep_event(&event, sweep_start_counter, sweep_end_counter, (s4)_traversals, swept_count, flushed_count, zombified_count);
 591   }
 592 
 593 #ifdef ASSERT
 594   if(PrintMethodFlushing) {
 595     tty->print_cr("### sweeper:      sweep time(" JLONG_FORMAT "): ", sweep_time.value());
 596   }
 597 #endif
 598 
 599   Log(codecache, sweep) log;
 600   if (log.is_debug()) {
 601     LogStream ls(log.debug());
 602     CodeCache::print_summary(&ls, false);
 603   }
 604   log_sweep("finished");
 605 
 606   // Sweeper is the only case where memory is released, check here if it
 607   // is time to restart the compiler. Only checking if there is a certain
 608   // amount of free memory in the code cache might lead to re-enabling
 609   // compilation although no memory has been released. For example, there are
 610   // cases when compilation was disabled although there is 4MB (or more) free
 611   // memory in the code cache. The reason is code cache fragmentation. Therefore,
 612   // it only makes sense to re-enable compilation if we have actually freed memory.
 613   // Note that typically several kB are released for sweeping 16MB of the code
 614   // cache. As a result, 'freed_memory' > 0 to restart the compiler.
 615   if (!CompileBroker::should_compile_new_jobs() && (freed_memory > 0)) {
 616     CompileBroker::set_should_compile_new_jobs(CompileBroker::run_compilation);
 617     log.debug("restart compiler");
 618     log_sweep("restart_compiler");
 619   }
 620 }
 621 
 622 /**
 623  * This function updates the sweeper statistics that keep track of nmethods
 624  * state changes. If there is 'enough' state change, the sweeper is invoked
 625  * as soon as possible. There can be data races on _bytes_changed. The data
 626  * races are benign, since it does not matter if we loose a couple of bytes.
 627  * In the worst case we call the sweeper a little later. Also, we are guaranteed
 628  * to invoke the sweeper if the code cache gets full.
 629  */
 630 void NMethodSweeper::report_state_change(nmethod* nm) {
 631   _bytes_changed += nm->total_size();
 632   possibly_enable_sweeper();
 633 }
 634 
 635 /**
 636  * Function determines if there was 'enough' state change in the code cache to invoke
 637  * the sweeper again. Currently, we determine 'enough' as more than 1% state change in
 638  * the code cache since the last sweep.
 639  */
 640 void NMethodSweeper::possibly_enable_sweeper() {
 641   double percent_changed = ((double)_bytes_changed / (double)ReservedCodeCacheSize) * 100;
 642   if (percent_changed > 1.0) {
 643     _should_sweep = true;
 644   }
 645 }
 646 
 647 class CompiledMethodMarker: public StackObj {
 648  private:
 649   CodeCacheSweeperThread* _thread;
 650  public:
 651   CompiledMethodMarker(CompiledMethod* cm) {
 652     JavaThread* current = JavaThread::current();
 653     assert (current->is_Code_cache_sweeper_thread(), "Must be");
 654     _thread = (CodeCacheSweeperThread*)current;
 655     if (!cm->is_zombie() && !cm->is_unloading()) {
 656       // Only expose live nmethods for scanning
 657       _thread->set_scanned_compiled_method(cm);
 658     }
 659   }
 660   ~CompiledMethodMarker() {
 661     _thread->set_scanned_compiled_method(NULL);
 662   }
 663 };
 664 
 665 NMethodSweeper::MethodStateChange NMethodSweeper::process_compiled_method(CompiledMethod* cm) {
 666   assert(cm != NULL, "sanity");
 667   assert(!CodeCache_lock->owned_by_self(), "just checking");
 668 
 669   MethodStateChange result = None;
 670   // Make sure this nmethod doesn't get unloaded during the scan,
 671   // since safepoints may happen during acquired below locks.
 672   CompiledMethodMarker nmm(cm);
 673   SWEEP(cm);
 674 
 675   // Skip methods that are currently referenced by the VM
 676   if (cm->is_locked_by_vm()) {
 677     // But still remember to clean-up inline caches for alive nmethods
 678     if (cm->is_alive()) {
 679       // Clean inline caches that point to zombie/non-entrant/unloaded nmethods
 680       cm->cleanup_inline_caches(false);
 681       SWEEP(cm);
 682     }
 683     return result;
 684   }
 685 
 686   if (cm->is_zombie()) {
 687     // All inline caches that referred to this nmethod were cleaned in the
 688     // previous sweeper cycle. Now flush the nmethod from the code cache.
 689     assert(!cm->is_locked_by_vm(), "must not flush locked Compiled Methods");
 690     cm->flush();
 691     assert(result == None, "sanity");
 692     result = Flushed;
 693   } else if (cm->is_not_entrant()) {
 694     // If there are no current activations of this method on the
 695     // stack we can safely convert it to a zombie method
 696     OrderAccess::loadload(); // _stack_traversal_mark and _state
 697     if (cm->can_convert_to_zombie()) {
 698       // Code cache state change is tracked in make_zombie()
 699       cm->make_zombie();
 700       SWEEP(cm);
 701       assert(result == None, "sanity");
 702       result = MadeZombie;
 703       assert(cm->is_zombie(), "nmethod must be zombie");
 704     } else {
 705       // Still alive, clean up its inline caches
 706       cm->cleanup_inline_caches(false);
 707       SWEEP(cm);
 708     }
 709   } else if (cm->is_unloaded()) {
 710     // Code is unloaded, so there are no activations on the stack.
 711     // Convert the nmethod to zombie.
 712     // Code cache state change is tracked in make_zombie()
 713     cm->make_zombie();
 714     SWEEP(cm);
 715     assert(result == None, "sanity");
 716     result = MadeZombie;
 717   } else {
 718     if (cm->is_nmethod()) {
 719       possibly_flush((nmethod*)cm);
 720     }
 721     // Clean inline caches that point to zombie/non-entrant/unloaded nmethods
 722     cm->cleanup_inline_caches(false);
 723     SWEEP(cm);
 724   }
 725   return result;
 726 }
 727 
 728 
 729 void NMethodSweeper::possibly_flush(nmethod* nm) {
 730   if (UseCodeCacheFlushing) {
 731     if (!nm->is_locked_by_vm() && !nm->is_native_method() && !nm->is_not_installed() && !nm->is_unloading()) {
 732       bool make_not_entrant = false;
 733 
 734       // Do not make native methods not-entrant
 735       nm->dec_hotness_counter();
 736       // Get the initial value of the hotness counter. This value depends on the
 737       // ReservedCodeCacheSize
 738       int reset_val = hotness_counter_reset_val();
 739       int time_since_reset = reset_val - nm->hotness_counter();
 740       int code_blob_type = CodeCache::get_code_blob_type(nm);
 741       double threshold = -reset_val + (CodeCache::reverse_free_ratio(code_blob_type) * NmethodSweepActivity);
 742       // The less free space in the code cache we have - the bigger reverse_free_ratio() is.
 743       // I.e., 'threshold' increases with lower available space in the code cache and a higher
 744       // NmethodSweepActivity. If the current hotness counter - which decreases from its initial
 745       // value until it is reset by stack walking - is smaller than the computed threshold, the
 746       // corresponding nmethod is considered for removal.
 747       if ((NmethodSweepActivity > 0) && (nm->hotness_counter() < threshold) && (time_since_reset > MinPassesBeforeFlush)) {
 748         // A method is marked as not-entrant if the method is
 749         // 1) 'old enough': nm->hotness_counter() < threshold
 750         // 2) The method was in_use for a minimum amount of time: (time_since_reset > MinPassesBeforeFlush)
 751         //    The second condition is necessary if we are dealing with very small code cache
 752         //    sizes (e.g., <10m) and the code cache size is too small to hold all hot methods.
 753         //    The second condition ensures that methods are not immediately made not-entrant
 754         //    after compilation.
 755         make_not_entrant = true;
 756       }
 757 
 758       // The stack-scanning low-cost detection may not see the method was used (which can happen for
 759       // flat profiles). Check the age counter for possible data.
 760       if (UseCodeAging && make_not_entrant && (nm->is_compiled_by_c2() || nm->is_compiled_by_c1())) {
 761         MethodCounters* mc = nm->method()->get_method_counters(Thread::current());
 762         if (mc != NULL) {
 763           // Snapshot the value as it's changed concurrently
 764           int age = mc->nmethod_age();
 765           if (MethodCounters::is_nmethod_hot(age)) {
 766             // The method has gone through flushing, and it became relatively hot that it deopted
 767             // before we could take a look at it. Give it more time to appear in the stack traces,
 768             // proportional to the number of deopts.
 769             MethodData* md = nm->method()->method_data();
 770             if (md != NULL && time_since_reset > (int)(MinPassesBeforeFlush * (md->tenure_traps() + 1))) {
 771               // It's been long enough, we still haven't seen it on stack.
 772               // Try to flush it, but enable counters the next time.
 773               mc->reset_nmethod_age();
 774             } else {
 775               make_not_entrant = false;
 776             }
 777           } else if (MethodCounters::is_nmethod_warm(age)) {
 778             // Method has counters enabled, and the method was used within
 779             // previous MinPassesBeforeFlush sweeps. Reset the counter. Stay in the existing
 780             // compiled state.
 781             mc->reset_nmethod_age();
 782             // delay the next check
 783             nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val());
 784             make_not_entrant = false;
 785           } else if (MethodCounters::is_nmethod_age_unset(age)) {
 786             // No counters were used before. Set the counters to the detection
 787             // limit value. If the method is going to be used again it will be compiled
 788             // with counters that we're going to use for analysis the the next time.
 789             mc->reset_nmethod_age();
 790           } else {
 791             // Method was totally idle for 10 sweeps
 792             // The counter already has the initial value, flush it and may be recompile
 793             // later with counters
 794           }
 795         }
 796       }
 797 
 798       if (make_not_entrant) {
 799         nm->make_not_entrant();
 800 
 801         // Code cache state change is tracked in make_not_entrant()
 802         if (PrintMethodFlushing && Verbose) {
 803           tty->print_cr("### Nmethod %d/" PTR_FORMAT "made not-entrant: hotness counter %d/%d threshold %f",
 804               nm->compile_id(), p2i(nm), nm->hotness_counter(), reset_val, threshold);
 805         }
 806       }
 807     }
 808   }
 809 }
 810 
 811 // Print out some state information about the current sweep and the
 812 // state of the code cache if it's requested.
 813 void NMethodSweeper::log_sweep(const char* msg, const char* format, ...) {
 814   if (PrintMethodFlushing) {
 815     ResourceMark rm;
 816     stringStream s;
 817     // Dump code cache state into a buffer before locking the tty,
 818     // because log_state() will use locks causing lock conflicts.
 819     CodeCache::log_state(&s);
 820 
 821     ttyLocker ttyl;
 822     tty->print("### sweeper: %s ", msg);
 823     if (format != NULL) {
 824       va_list ap;
 825       va_start(ap, format);
 826       tty->vprint(format, ap);
 827       va_end(ap);
 828     }
 829     tty->print_cr("%s", s.as_string());
 830   }
 831 
 832   if (LogCompilation && (xtty != NULL)) {
 833     ResourceMark rm;
 834     stringStream s;
 835     // Dump code cache state into a buffer before locking the tty,
 836     // because log_state() will use locks causing lock conflicts.
 837     CodeCache::log_state(&s);
 838 
 839     ttyLocker ttyl;
 840     xtty->begin_elem("sweeper state='%s' traversals='" INTX_FORMAT "' ", msg, (intx)traversal_count());
 841     if (format != NULL) {
 842       va_list ap;
 843       va_start(ap, format);
 844       xtty->vprint(format, ap);
 845       va_end(ap);
 846     }
 847     xtty->print("%s", s.as_string());
 848     xtty->stamp();
 849     xtty->end_elem();
 850   }
 851 }
 852 
 853 void NMethodSweeper::print(outputStream* out) {
 854   ttyLocker ttyl;
 855   out = (out == NULL) ? tty : out;
 856   out->print_cr("Code cache sweeper statistics:");
 857   out->print_cr("  Total sweep time:                %1.0lf ms", (double)_total_time_sweeping.value()/1000000);
 858   out->print_cr("  Total number of full sweeps:     %ld", _total_nof_code_cache_sweeps);
 859   out->print_cr("  Total number of flushed methods: %ld (thereof %ld C2 methods)", _total_nof_methods_reclaimed,
 860                                                     _total_nof_c2_methods_reclaimed);
 861   out->print_cr("  Total size of flushed methods:   " SIZE_FORMAT " kB", _total_flushed_size/K);
 862 }
--- EOF ---