1 /*
   2  * Copyright (c) 1997, 2013, 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 "memory/resourceArea.hpp"
  32 #include "oops/method.hpp"
  33 #include "runtime/atomic.hpp"
  34 #include "runtime/compilationPolicy.hpp"
  35 #include "runtime/mutexLocker.hpp"
  36 #include "runtime/os.hpp"
  37 #include "runtime/sweeper.hpp"
  38 #include "runtime/vm_operations.hpp"
  39 #include "trace/tracing.hpp"
  40 #include "utilities/events.hpp"
  41 #include "utilities/xmlstream.hpp"
  42 
  43 #ifdef ASSERT
  44 
  45 #define SWEEP(nm) record_sweep(nm, __LINE__)
  46 // Sweeper logging code
  47 class SweeperRecord {
  48  public:
  49   int traversal;
  50   int invocation;
  51   int compile_id;
  52   long traversal_mark;
  53   int state;
  54   const char* kind;
  55   address vep;
  56   address uep;
  57   int line;
  58 
  59   void print() {
  60       tty->print_cr("traversal = %d invocation = %d compile_id = %d %s uep = " PTR_FORMAT " vep = "
  61                     PTR_FORMAT " state = %d traversal_mark %d line = %d",
  62                     traversal,
  63                     invocation,
  64                     compile_id,
  65                     kind == NULL ? "" : kind,
  66                     uep,
  67                     vep,
  68                     state,
  69                     traversal_mark,
  70                     line);
  71   }
  72 };
  73 
  74 static int _sweep_index = 0;
  75 static SweeperRecord* _records = NULL;
  76 
  77 void NMethodSweeper::report_events(int id, address entry) {
  78   if (_records != NULL) {
  79     for (int i = _sweep_index; i < SweeperLogEntries; i++) {
  80       if (_records[i].uep == entry ||
  81           _records[i].vep == entry ||
  82           _records[i].compile_id == id) {
  83         _records[i].print();
  84       }
  85     }
  86     for (int i = 0; i < _sweep_index; i++) {
  87       if (_records[i].uep == entry ||
  88           _records[i].vep == entry ||
  89           _records[i].compile_id == id) {
  90         _records[i].print();
  91       }
  92     }
  93   }
  94 }
  95 
  96 void NMethodSweeper::report_events() {
  97   if (_records != NULL) {
  98     for (int i = _sweep_index; i < SweeperLogEntries; i++) {
  99       // skip empty records
 100       if (_records[i].vep == NULL) continue;
 101       _records[i].print();
 102     }
 103     for (int i = 0; i < _sweep_index; i++) {
 104       // skip empty records
 105       if (_records[i].vep == NULL) continue;
 106       _records[i].print();
 107     }
 108   }
 109 }
 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   }
 539 
 540   if (LogCompilation && (xtty != NULL)) {
 541     stringStream s;
 542     // Dump code cache state into a buffer before locking the tty,
 543     // because log_state() will use locks causing lock conflicts.
 544     CodeCache::log_state(&s);
 545 
 546     ttyLocker ttyl;
 547     xtty->begin_elem("sweeper state='%s' traversals='" INTX_FORMAT "' ", msg, (intx)traversal_count());
 548     if (format != NULL) {
 549       va_list ap;
 550       va_start(ap, format);
 551       xtty->vprint(format, ap);
 552       va_end(ap);
 553     }
 554     xtty->print(s.as_string());
 555     xtty->stamp();
 556     xtty->end_elem();
 557   }
 558 }