1 /* 2 * Copyright (c) 1997, 2011, 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/nmethod.hpp" 28 #include "compiler/compileBroker.hpp" 29 #include "memory/resourceArea.hpp" 30 #include "oops/methodOop.hpp" 31 #include "runtime/atomic.hpp" 32 #include "runtime/compilationPolicy.hpp" 33 #include "runtime/mutexLocker.hpp" 34 #include "runtime/os.hpp" 35 #include "runtime/sweeper.hpp" 36 #include "runtime/vm_operations.hpp" 37 #include "utilities/events.hpp" 38 #include "utilities/xmlstream.hpp" 39 40 #ifdef ASSERT 41 42 #define SWEEP(nm) record_sweep(nm, __LINE__) 43 // Sweeper logging code 44 class SweeperRecord { 45 public: 46 int traversal; 47 int invocation; 48 int compile_id; 49 long traversal_mark; 50 int state; 51 const char* kind; 52 address vep; 53 address uep; 54 int line; 55 56 void print() { 57 tty->print_cr("traversal = %d invocation = %d compile_id = %d %s uep = " PTR_FORMAT " vep = " 58 PTR_FORMAT " state = %d traversal_mark %d line = %d", 59 traversal, 60 invocation, 61 compile_id, 62 kind == NULL ? "" : kind, 63 uep, 64 vep, 65 state, 66 traversal_mark, 67 line); 68 } 69 }; 70 71 static uint _sweep_index = 0; 72 static SweeperRecord* _records = NULL; 73 74 void NMethodSweeper::report_events(int id, address entry) { 75 if (_records != NULL) { 76 for (uint i = _sweep_index; i < SweeperLogEntries; i++) { 77 if (_records[i].uep == entry || 78 _records[i].vep == entry || 79 _records[i].compile_id == id) { 80 _records[i].print(); 81 } 82 } 83 for (uint i = 0; i < _sweep_index; i++) { 84 if (_records[i].uep == entry || 85 _records[i].vep == entry || 86 _records[i].compile_id == id) { 87 _records[i].print(); 88 } 89 } 90 } 91 } 92 93 void NMethodSweeper::report_events() { 94 if (_records != NULL) { 95 for (uint i = _sweep_index; i < SweeperLogEntries; i++) { 96 // skip empty records 97 if (_records[i].vep == NULL) continue; 98 _records[i].print(); 99 } 100 for (uint i = 0; i < _sweep_index; i++) { 101 // skip empty records 102 if (_records[i].vep == NULL) continue; 103 _records[i].print(); 104 } 105 } 106 } 107 108 void NMethodSweeper::record_sweep(nmethod* nm, int line) { 109 if (_records != NULL) { 110 _records[_sweep_index].traversal = _traversals; 111 _records[_sweep_index].traversal_mark = nm->_stack_traversal_mark; 112 _records[_sweep_index].invocation = _invocations; 113 _records[_sweep_index].compile_id = nm->compile_id(); 114 _records[_sweep_index].kind = nm->compile_kind(); 115 _records[_sweep_index].state = nm->_state; 116 _records[_sweep_index].vep = nm->verified_entry_point(); 117 _records[_sweep_index].uep = nm->entry_point(); 118 _records[_sweep_index].line = line; 119 120 _sweep_index = (_sweep_index + 1) % SweeperLogEntries; 121 } 122 } 123 #else 124 #define SWEEP(nm) 125 #endif 126 127 128 long NMethodSweeper::_traversals = 0; // No. of stack traversals performed 129 nmethod* NMethodSweeper::_current = NULL; // Current nmethod 130 int NMethodSweeper::_seen = 0 ; // No. of nmethods we have currently processed in current pass of CodeCache 131 132 volatile int NMethodSweeper::_invocations = 0; // No. of invocations left until we are completed with this pass 133 volatile int NMethodSweeper::_sweep_started = 0; // Whether a sweep is in progress. 134 135 jint NMethodSweeper::_locked_seen = 0; 136 jint NMethodSweeper::_not_entrant_seen_on_stack = 0; 137 bool NMethodSweeper::_rescan = false; 138 bool NMethodSweeper::_do_sweep = false; 139 bool NMethodSweeper::_was_full = false; 140 jint NMethodSweeper::_advise_to_sweep = 0; 141 jlong NMethodSweeper::_last_was_full = 0; 142 uint NMethodSweeper::_highest_marked = 0; 143 long NMethodSweeper::_was_full_traversal = 0; 144 145 class MarkActivationClosure: public CodeBlobClosure { 146 public: 147 virtual void do_code_blob(CodeBlob* cb) { 148 // If we see an activation belonging to a non_entrant nmethod, we mark it. 149 if (cb->is_nmethod() && ((nmethod*)cb)->is_not_entrant()) { 150 ((nmethod*)cb)->mark_as_seen_on_stack(); 151 } 152 } 153 }; 154 static MarkActivationClosure mark_activation_closure; 155 156 void NMethodSweeper::scan_stacks() { 157 assert(SafepointSynchronize::is_at_safepoint(), "must be executed at a safepoint"); 158 if (!MethodFlushing) return; 159 _do_sweep = true; 160 161 // No need to synchronize access, since this is always executed at a 162 // safepoint. If we aren't in the middle of scan and a rescan 163 // hasn't been requested then just return. If UseCodeCacheFlushing is on and 164 // code cache flushing is in progress, don't skip sweeping to help make progress 165 // clearing space in the code cache. 166 if ((_current == NULL && !_rescan) && !(UseCodeCacheFlushing && !CompileBroker::should_compile_new_jobs())) { 167 _do_sweep = false; 168 return; 169 } 170 171 // Make sure CompiledIC_lock in unlocked, since we might update some 172 // inline caches. If it is, we just bail-out and try later. 173 if (CompiledIC_lock->is_locked() || Patching_lock->is_locked()) return; 174 175 // Check for restart 176 assert(CodeCache::find_blob_unsafe(_current) == _current, "Sweeper nmethod cached state invalid"); 177 if (_current == NULL) { 178 _seen = 0; 179 _invocations = NmethodSweepFraction; 180 _current = CodeCache::first_nmethod(); 181 _traversals += 1; 182 if (PrintMethodFlushing) { 183 tty->print_cr("### Sweep: stack traversal %d", _traversals); 184 } 185 Threads::nmethods_do(&mark_activation_closure); 186 187 // reset the flags since we started a scan from the beginning. 188 _rescan = false; 189 _locked_seen = 0; 190 _not_entrant_seen_on_stack = 0; 191 } 192 193 if (UseCodeCacheFlushing) { 194 if (!CodeCache::needs_flushing()) { 195 // scan_stacks() runs during a safepoint, no race with setters 196 _advise_to_sweep = 0; 197 } 198 199 if (was_full()) { 200 // There was some progress so attempt to restart the compiler 201 jlong now = os::javaTimeMillis(); 202 jlong max_interval = (jlong)MinCodeCacheFlushingInterval * (jlong)1000; 203 jlong curr_interval = now - _last_was_full; 204 if ((!CodeCache::needs_flushing()) && (curr_interval > max_interval)) { 205 CompileBroker::set_should_compile_new_jobs(CompileBroker::run_compilation); 206 set_was_full(false); 207 208 // Update the _last_was_full time so we can tell how fast the 209 // code cache is filling up 210 _last_was_full = os::javaTimeMillis(); 211 212 log_sweep("restart_compiler"); 213 } 214 } 215 } 216 } 217 218 void NMethodSweeper::possibly_sweep() { 219 assert(JavaThread::current()->thread_state() == _thread_in_vm, "must run in vm mode"); 220 if ((!MethodFlushing) || (!_do_sweep)) return; 221 222 if (_invocations > 0) { 223 // Only one thread at a time will sweep 224 jint old = Atomic::cmpxchg( 1, &_sweep_started, 0 ); 225 if (old != 0) { 226 return; 227 } 228 #ifdef ASSERT 229 if (LogSweeper && _records == NULL) { 230 // Create the ring buffer for the logging code 231 _records = NEW_C_HEAP_ARRAY(SweeperRecord, SweeperLogEntries); 232 memset(_records, 0, sizeof(SweeperRecord) * SweeperLogEntries); 233 } 234 #endif 235 if (_invocations > 0) { 236 sweep_code_cache(); 237 _invocations--; 238 } 239 _sweep_started = 0; 240 } 241 } 242 243 void NMethodSweeper::sweep_code_cache() { 244 #ifdef ASSERT 245 jlong sweep_start; 246 if (PrintMethodFlushing) { 247 sweep_start = os::javaTimeMillis(); 248 } 249 #endif 250 if (PrintMethodFlushing && Verbose) { 251 tty->print_cr("### Sweep at %d out of %d. Invocations left: %d", _seen, CodeCache::nof_nmethods(), _invocations); 252 } 253 254 // We want to visit all nmethods after NmethodSweepFraction 255 // invocations so divide the remaining number of nmethods by the 256 // remaining number of invocations. This is only an estimate since 257 // the number of nmethods changes during the sweep so the final 258 // stage must iterate until it there are no more nmethods. 259 int todo = (CodeCache::nof_nmethods() - _seen) / _invocations; 260 261 assert(!SafepointSynchronize::is_at_safepoint(), "should not be in safepoint when we get here"); 262 assert(!CodeCache_lock->owned_by_self(), "just checking"); 263 264 { 265 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag); 266 267 // The last invocation iterates until there are no more nmethods 268 for (int i = 0; (i < todo || _invocations == 1) && _current != NULL; i++) { 269 270 // Since we will give up the CodeCache_lock, always skip ahead 271 // to the next nmethod. Other blobs can be deleted by other 272 // threads but nmethods are only reclaimed by the sweeper. 273 nmethod* next = CodeCache::next_nmethod(_current); 274 275 // Now ready to process nmethod and give up CodeCache_lock 276 { 277 MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag); 278 process_nmethod(_current); 279 } 280 _seen++; 281 _current = next; 282 } 283 } 284 285 assert(_invocations > 1 || _current == NULL, "must have scanned the whole cache"); 286 287 if (_current == NULL && !_rescan && (_locked_seen || _not_entrant_seen_on_stack)) { 288 // we've completed a scan without making progress but there were 289 // nmethods we were unable to process either because they were 290 // locked or were still on stack. We don't have to aggresively 291 // clean them up so just stop scanning. We could scan once more 292 // but that complicates the control logic and it's unlikely to 293 // matter much. 294 if (PrintMethodFlushing) { 295 tty->print_cr("### Couldn't make progress on some nmethods so stopping sweep"); 296 } 297 } 298 299 #ifdef ASSERT 300 if(PrintMethodFlushing) { 301 jlong sweep_end = os::javaTimeMillis(); 302 tty->print_cr("### sweeper: sweep time(%d): " INT64_FORMAT, _invocations, sweep_end - sweep_start); 303 } 304 #endif 305 306 if (_invocations == 1) { 307 log_sweep("finished"); 308 } 309 } 310 311 class NMethodMarker: public StackObj { 312 private: 313 CompilerThread* _thread; 314 public: 315 NMethodMarker(nmethod* nm) { 316 _thread = CompilerThread::current(); 317 _thread->set_scanned_nmethod(nm); 318 } 319 ~NMethodMarker() { 320 _thread->set_scanned_nmethod(NULL); 321 } 322 }; 323 324 325 void NMethodSweeper::process_nmethod(nmethod *nm) { 326 assert(!CodeCache_lock->owned_by_self(), "just checking"); 327 328 // Make sure this nmethod doesn't get unloaded during the scan, 329 // since the locks acquired below might safepoint. 330 NMethodMarker nmm(nm); 331 332 SWEEP(nm); 333 334 // Skip methods that are currently referenced by the VM 335 if (nm->is_locked_by_vm()) { 336 // But still remember to clean-up inline caches for alive nmethods 337 if (nm->is_alive()) { 338 // Clean-up all inline caches that points to zombie/non-reentrant methods 339 MutexLocker cl(CompiledIC_lock); 340 nm->cleanup_inline_caches(); 341 SWEEP(nm); 342 } else { 343 _locked_seen++; 344 SWEEP(nm); 345 } 346 return; 347 } 348 349 if (nm->is_zombie()) { 350 // If it is first time, we see nmethod then we mark it. Otherwise, 351 // we reclame it. When we have seen a zombie method twice, we know that 352 // there are no inline caches that refer to it. 353 if (nm->is_marked_for_reclamation()) { 354 assert(!nm->is_locked_by_vm(), "must not flush locked nmethods"); 355 if (PrintMethodFlushing && Verbose) { 356 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (marked for reclamation) being flushed", nm->compile_id(), nm); 357 } 358 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag); 359 nm->flush(); 360 } else { 361 if (PrintMethodFlushing && Verbose) { 362 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (zombie) being marked for reclamation", nm->compile_id(), nm); 363 } 364 nm->mark_for_reclamation(); 365 _rescan = true; 366 SWEEP(nm); 367 } 368 } else if (nm->is_not_entrant()) { 369 // If there is no current activations of this method on the 370 // stack we can safely convert it to a zombie method 371 if (nm->can_not_entrant_be_converted()) { 372 if (PrintMethodFlushing && Verbose) { 373 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (not entrant) being made zombie", nm->compile_id(), nm); 374 } 375 nm->make_zombie(); 376 _rescan = true; 377 SWEEP(nm); 378 } else { 379 // Still alive, clean up its inline caches 380 MutexLocker cl(CompiledIC_lock); 381 nm->cleanup_inline_caches(); 382 // we coudn't transition this nmethod so don't immediately 383 // request a rescan. If this method stays on the stack for a 384 // long time we don't want to keep rescanning the code cache. 385 _not_entrant_seen_on_stack++; 386 SWEEP(nm); 387 } 388 } else if (nm->is_unloaded()) { 389 // Unloaded code, just make it a zombie 390 if (PrintMethodFlushing && Verbose) 391 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (unloaded) being made zombie", nm->compile_id(), nm); 392 if (nm->is_osr_method()) { 393 // No inline caches will ever point to osr methods, so we can just remove it 394 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag); 395 SWEEP(nm); 396 nm->flush(); 397 } else { 398 nm->make_zombie(); 399 _rescan = true; 400 SWEEP(nm); 401 } 402 } else { 403 assert(nm->is_alive(), "should be alive"); 404 405 if (UseCodeCacheFlushing) { 406 if ((nm->method()->code() != nm) && !(nm->is_locked_by_vm()) && !(nm->is_osr_method()) && 407 (_traversals > _was_full_traversal+2) && (((uint)nm->compile_id()) < _highest_marked) && 408 CodeCache::needs_flushing()) { 409 // This method has not been called since the forced cleanup happened 410 nm->make_not_entrant(); 411 } 412 } 413 414 // Clean-up all inline caches that points to zombie/non-reentrant methods 415 MutexLocker cl(CompiledIC_lock); 416 nm->cleanup_inline_caches(); 417 SWEEP(nm); 418 } 419 } 420 421 // Code cache unloading: when compilers notice the code cache is getting full, 422 // they will call a vm op that comes here. This code attempts to speculatively 423 // unload the oldest half of the nmethods (based on the compile job id) by 424 // saving the old code in a list in the CodeCache. Then 425 // execution resumes. If a method so marked is not called by the second sweeper 426 // stack traversal after the current one, the nmethod will be marked non-entrant and 427 // got rid of by normal sweeping. If the method is called, the methodOop's 428 // _code field is restored and the methodOop/nmethod 429 // go back to their normal state. 430 void NMethodSweeper::handle_full_code_cache(bool is_full) { 431 // Only the first one to notice can advise us to start early cleaning 432 if (!is_full){ 433 jint old = Atomic::cmpxchg( 1, &_advise_to_sweep, 0 ); 434 if (old != 0) { 435 return; 436 } 437 } 438 439 if (is_full) { 440 // Since code cache is full, immediately stop new compiles 441 bool did_set = CompileBroker::set_should_compile_new_jobs(CompileBroker::stop_compilation); 442 if (!did_set) { 443 // only the first to notice can start the cleaning, 444 // others will go back and block 445 return; 446 } 447 set_was_full(true); 448 449 // If we run out within MinCodeCacheFlushingInterval of the last unload time, give up 450 jlong now = os::javaTimeMillis(); 451 jlong max_interval = (jlong)MinCodeCacheFlushingInterval * (jlong)1000; 452 jlong curr_interval = now - _last_was_full; 453 if (curr_interval < max_interval) { 454 _rescan = true; 455 log_sweep("disable_compiler", "flushing_interval='" UINT64_FORMAT "'", 456 curr_interval/1000); 457 return; 458 } 459 } 460 461 VM_HandleFullCodeCache op(is_full); 462 VMThread::execute(&op); 463 464 // rescan again as soon as possible 465 _rescan = true; 466 } 467 468 void NMethodSweeper::speculative_disconnect_nmethods(bool is_full) { 469 // If there was a race in detecting full code cache, only run 470 // one vm op for it or keep the compiler shut off 471 472 debug_only(jlong start = os::javaTimeMillis();) 473 474 if ((!was_full()) && (is_full)) { 475 if (!CodeCache::needs_flushing()) { 476 log_sweep("restart_compiler"); 477 CompileBroker::set_should_compile_new_jobs(CompileBroker::run_compilation); 478 return; 479 } 480 } 481 482 // Traverse the code cache trying to dump the oldest nmethods 483 uint curr_max_comp_id = CompileBroker::get_compilation_id(); 484 uint flush_target = ((curr_max_comp_id - _highest_marked) >> 1) + _highest_marked; 485 log_sweep("start_cleaning"); 486 487 nmethod* nm = CodeCache::alive_nmethod(CodeCache::first()); 488 jint disconnected = 0; 489 jint made_not_entrant = 0; 490 while ((nm != NULL)){ 491 uint curr_comp_id = nm->compile_id(); 492 493 // OSR methods cannot be flushed like this. Also, don't flush native methods 494 // since they are part of the JDK in most cases 495 if (nm->is_in_use() && (!nm->is_osr_method()) && (!nm->is_locked_by_vm()) && 496 (!nm->is_native_method()) && ((curr_comp_id < flush_target))) { 497 498 if ((nm->method()->code() == nm)) { 499 // This method has not been previously considered for 500 // unloading or it was restored already 501 CodeCache::speculatively_disconnect(nm); 502 disconnected++; 503 } else if (nm->is_speculatively_disconnected()) { 504 // This method was previously considered for preemptive unloading and was not called since then 505 CompilationPolicy::policy()->delay_compilation(nm->method()); 506 nm->make_not_entrant(); 507 made_not_entrant++; 508 } 509 510 if (curr_comp_id > _highest_marked) { 511 _highest_marked = curr_comp_id; 512 } 513 } 514 nm = CodeCache::alive_nmethod(CodeCache::next(nm)); 515 } 516 517 log_sweep("stop_cleaning", 518 "disconnected='" UINT32_FORMAT "' made_not_entrant='" UINT32_FORMAT "'", 519 disconnected, made_not_entrant); 520 521 // Shut off compiler. Sweeper will start over with a new stack scan and 522 // traversal cycle and turn it back on if it clears enough space. 523 if (was_full()) { 524 _last_was_full = os::javaTimeMillis(); 525 CompileBroker::set_should_compile_new_jobs(CompileBroker::stop_compilation); 526 } 527 528 // After two more traversals the sweeper will get rid of unrestored nmethods 529 _was_full_traversal = _traversals; 530 #ifdef ASSERT 531 jlong end = os::javaTimeMillis(); 532 if(PrintMethodFlushing && Verbose) { 533 tty->print_cr("### sweeper: unload time: " INT64_FORMAT, end-start); 534 } 535 #endif 536 } 537 538 539 // Print out some state information about the current sweep and the 540 // state of the code cache if it's requested. 541 void NMethodSweeper::log_sweep(const char* msg, const char* format, ...) { 542 if (PrintMethodFlushing) { 543 stringStream s; 544 // Dump code cache state into a buffer before locking the tty, 545 // because log_state() will use locks causing lock conflicts. 546 CodeCache::log_state(&s); 547 548 ttyLocker ttyl; 549 tty->print("### sweeper: %s ", msg); 550 if (format != NULL) { 551 va_list ap; 552 va_start(ap, format); 553 tty->vprint(format, ap); 554 va_end(ap); 555 } 556 tty->print_cr(s.as_string()); 557 } 558 559 if (LogCompilation && (xtty != NULL)) { 560 stringStream s; 561 // Dump code cache state into a buffer before locking the tty, 562 // because log_state() will use locks causing lock conflicts. 563 CodeCache::log_state(&s); 564 565 ttyLocker ttyl; 566 xtty->begin_elem("sweeper state='%s' traversals='" INTX_FORMAT "' ", msg, (intx)traversal_count()); 567 if (format != NULL) { 568 va_list ap; 569 va_start(ap, format); 570 xtty->vprint(format, ap); 571 va_end(ap); 572 } 573 xtty->print(s.as_string()); 574 xtty->stamp(); 575 xtty->end_elem(); 576 } 577 }