sweeper.cpp revision 3465:d2a62e0f25eb
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 44class 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 71static int _sweep_index = 0; 72static SweeperRecord* _records = NULL; 73 74void NMethodSweeper::report_events(int id, address entry) { 75 if (_records != NULL) { 76 for (int 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 (int 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 93void NMethodSweeper::report_events() { 94 if (_records != NULL) { 95 for (int i = _sweep_index; i < SweeperLogEntries; i++) { 96 // skip empty records 97 if (_records[i].vep == NULL) continue; 98 _records[i].print(); 99 } 100 for (int 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 108void 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 128long NMethodSweeper::_traversals = 0; // No. of stack traversals performed 129nmethod* NMethodSweeper::_current = NULL; // Current nmethod 130int NMethodSweeper::_seen = 0 ; // No. of nmethods we have currently processed in current pass of CodeCache 131 132volatile int NMethodSweeper::_invocations = 0; // No. of invocations left until we are completed with this pass 133volatile int NMethodSweeper::_sweep_started = 0; // Whether a sweep is in progress. 134 135jint NMethodSweeper::_locked_seen = 0; 136jint NMethodSweeper::_not_entrant_seen_on_stack = 0; 137bool NMethodSweeper::_rescan = false; 138bool NMethodSweeper::_do_sweep = false; 139bool NMethodSweeper::_was_full = false; 140jint NMethodSweeper::_advise_to_sweep = 0; 141jlong NMethodSweeper::_last_was_full = 0; 142uint NMethodSweeper::_highest_marked = 0; 143long NMethodSweeper::_was_full_traversal = 0; 144 145class MarkActivationClosure: public CodeBlobClosure { 146public: 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}; 154static MarkActivationClosure mark_activation_closure; 155 156void 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 218void 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, mtGC); 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 243void 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 if (SafepointSynchronize::is_synchronizing()) { // Safepoint request 270 if (PrintMethodFlushing && Verbose) { 271 tty->print_cr("### Sweep at %d out of %d, invocation: %d, yielding to safepoint", _seen, CodeCache::nof_nmethods(), _invocations); 272 } 273 MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag); 274 275 assert(Thread::current()->is_Java_thread(), "should be java thread"); 276 JavaThread* thread = (JavaThread*)Thread::current(); 277 ThreadBlockInVM tbivm(thread); 278 thread->java_suspend_self(); 279 } 280 // Since we will give up the CodeCache_lock, always skip ahead 281 // to the next nmethod. Other blobs can be deleted by other 282 // threads but nmethods are only reclaimed by the sweeper. 283 nmethod* next = CodeCache::next_nmethod(_current); 284 285 // Now ready to process nmethod and give up CodeCache_lock 286 { 287 MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag); 288 process_nmethod(_current); 289 } 290 _seen++; 291 _current = next; 292 } 293 } 294 295 assert(_invocations > 1 || _current == NULL, "must have scanned the whole cache"); 296 297 if (_current == NULL && !_rescan && (_locked_seen || _not_entrant_seen_on_stack)) { 298 // we've completed a scan without making progress but there were 299 // nmethods we were unable to process either because they were 300 // locked or were still on stack. We don't have to aggresively 301 // clean them up so just stop scanning. We could scan once more 302 // but that complicates the control logic and it's unlikely to 303 // matter much. 304 if (PrintMethodFlushing) { 305 tty->print_cr("### Couldn't make progress on some nmethods so stopping sweep"); 306 } 307 } 308 309#ifdef ASSERT 310 if(PrintMethodFlushing) { 311 jlong sweep_end = os::javaTimeMillis(); 312 tty->print_cr("### sweeper: sweep time(%d): " INT64_FORMAT, _invocations, sweep_end - sweep_start); 313 } 314#endif 315 316 if (_invocations == 1) { 317 log_sweep("finished"); 318 } 319} 320 321class NMethodMarker: public StackObj { 322 private: 323 CompilerThread* _thread; 324 public: 325 NMethodMarker(nmethod* nm) { 326 _thread = CompilerThread::current(); 327 _thread->set_scanned_nmethod(nm); 328 } 329 ~NMethodMarker() { 330 _thread->set_scanned_nmethod(NULL); 331 } 332}; 333 334 335void NMethodSweeper::process_nmethod(nmethod *nm) { 336 assert(!CodeCache_lock->owned_by_self(), "just checking"); 337 338 // Make sure this nmethod doesn't get unloaded during the scan, 339 // since the locks acquired below might safepoint. 340 NMethodMarker nmm(nm); 341 342 SWEEP(nm); 343 344 // Skip methods that are currently referenced by the VM 345 if (nm->is_locked_by_vm()) { 346 // But still remember to clean-up inline caches for alive nmethods 347 if (nm->is_alive()) { 348 // Clean-up all inline caches that points to zombie/non-reentrant methods 349 MutexLocker cl(CompiledIC_lock); 350 nm->cleanup_inline_caches(); 351 SWEEP(nm); 352 } else { 353 _locked_seen++; 354 SWEEP(nm); 355 } 356 return; 357 } 358 359 if (nm->is_zombie()) { 360 // If it is first time, we see nmethod then we mark it. Otherwise, 361 // we reclame it. When we have seen a zombie method twice, we know that 362 // there are no inline caches that refer to it. 363 if (nm->is_marked_for_reclamation()) { 364 assert(!nm->is_locked_by_vm(), "must not flush locked nmethods"); 365 if (PrintMethodFlushing && Verbose) { 366 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (marked for reclamation) being flushed", nm->compile_id(), nm); 367 } 368 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag); 369 nm->flush(); 370 } else { 371 if (PrintMethodFlushing && Verbose) { 372 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (zombie) being marked for reclamation", nm->compile_id(), nm); 373 } 374 nm->mark_for_reclamation(); 375 _rescan = true; 376 SWEEP(nm); 377 } 378 } else if (nm->is_not_entrant()) { 379 // If there is no current activations of this method on the 380 // stack we can safely convert it to a zombie method 381 if (nm->can_not_entrant_be_converted()) { 382 if (PrintMethodFlushing && Verbose) { 383 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (not entrant) being made zombie", nm->compile_id(), nm); 384 } 385 nm->make_zombie(); 386 _rescan = true; 387 SWEEP(nm); 388 } else { 389 // Still alive, clean up its inline caches 390 MutexLocker cl(CompiledIC_lock); 391 nm->cleanup_inline_caches(); 392 // we coudn't transition this nmethod so don't immediately 393 // request a rescan. If this method stays on the stack for a 394 // long time we don't want to keep rescanning the code cache. 395 _not_entrant_seen_on_stack++; 396 SWEEP(nm); 397 } 398 } else if (nm->is_unloaded()) { 399 // Unloaded code, just make it a zombie 400 if (PrintMethodFlushing && Verbose) 401 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (unloaded) being made zombie", nm->compile_id(), nm); 402 if (nm->is_osr_method()) { 403 // No inline caches will ever point to osr methods, so we can just remove it 404 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag); 405 SWEEP(nm); 406 nm->flush(); 407 } else { 408 nm->make_zombie(); 409 _rescan = true; 410 SWEEP(nm); 411 } 412 } else { 413 assert(nm->is_alive(), "should be alive"); 414 415 if (UseCodeCacheFlushing) { 416 if ((nm->method()->code() != nm) && !(nm->is_locked_by_vm()) && !(nm->is_osr_method()) && 417 (_traversals > _was_full_traversal+2) && (((uint)nm->compile_id()) < _highest_marked) && 418 CodeCache::needs_flushing()) { 419 // This method has not been called since the forced cleanup happened 420 nm->make_not_entrant(); 421 } 422 } 423 424 // Clean-up all inline caches that points to zombie/non-reentrant methods 425 MutexLocker cl(CompiledIC_lock); 426 nm->cleanup_inline_caches(); 427 SWEEP(nm); 428 } 429} 430 431// Code cache unloading: when compilers notice the code cache is getting full, 432// they will call a vm op that comes here. This code attempts to speculatively 433// unload the oldest half of the nmethods (based on the compile job id) by 434// saving the old code in a list in the CodeCache. Then 435// execution resumes. If a method so marked is not called by the second sweeper 436// stack traversal after the current one, the nmethod will be marked non-entrant and 437// got rid of by normal sweeping. If the method is called, the methodOop's 438// _code field is restored and the methodOop/nmethod 439// go back to their normal state. 440void NMethodSweeper::handle_full_code_cache(bool is_full) { 441 // Only the first one to notice can advise us to start early cleaning 442 if (!is_full){ 443 jint old = Atomic::cmpxchg( 1, &_advise_to_sweep, 0 ); 444 if (old != 0) { 445 return; 446 } 447 } 448 449 if (is_full) { 450 // Since code cache is full, immediately stop new compiles 451 bool did_set = CompileBroker::set_should_compile_new_jobs(CompileBroker::stop_compilation); 452 if (!did_set) { 453 // only the first to notice can start the cleaning, 454 // others will go back and block 455 return; 456 } 457 set_was_full(true); 458 459 // If we run out within MinCodeCacheFlushingInterval of the last unload time, give up 460 jlong now = os::javaTimeMillis(); 461 jlong max_interval = (jlong)MinCodeCacheFlushingInterval * (jlong)1000; 462 jlong curr_interval = now - _last_was_full; 463 if (curr_interval < max_interval) { 464 _rescan = true; 465 log_sweep("disable_compiler", "flushing_interval='" UINT64_FORMAT "'", 466 curr_interval/1000); 467 return; 468 } 469 } 470 471 VM_HandleFullCodeCache op(is_full); 472 VMThread::execute(&op); 473 474 // rescan again as soon as possible 475 _rescan = true; 476} 477 478void NMethodSweeper::speculative_disconnect_nmethods(bool is_full) { 479 // If there was a race in detecting full code cache, only run 480 // one vm op for it or keep the compiler shut off 481 482 debug_only(jlong start = os::javaTimeMillis();) 483 484 if ((!was_full()) && (is_full)) { 485 if (!CodeCache::needs_flushing()) { 486 log_sweep("restart_compiler"); 487 CompileBroker::set_should_compile_new_jobs(CompileBroker::run_compilation); 488 return; 489 } 490 } 491 492 // Traverse the code cache trying to dump the oldest nmethods 493 uint curr_max_comp_id = CompileBroker::get_compilation_id(); 494 uint flush_target = ((curr_max_comp_id - _highest_marked) >> 1) + _highest_marked; 495 log_sweep("start_cleaning"); 496 497 nmethod* nm = CodeCache::alive_nmethod(CodeCache::first()); 498 jint disconnected = 0; 499 jint made_not_entrant = 0; 500 while ((nm != NULL)){ 501 uint curr_comp_id = nm->compile_id(); 502 503 // OSR methods cannot be flushed like this. Also, don't flush native methods 504 // since they are part of the JDK in most cases 505 if (nm->is_in_use() && (!nm->is_osr_method()) && (!nm->is_locked_by_vm()) && 506 (!nm->is_native_method()) && ((curr_comp_id < flush_target))) { 507 508 if ((nm->method()->code() == nm)) { 509 // This method has not been previously considered for 510 // unloading or it was restored already 511 CodeCache::speculatively_disconnect(nm); 512 disconnected++; 513 } else if (nm->is_speculatively_disconnected()) { 514 // This method was previously considered for preemptive unloading and was not called since then 515 CompilationPolicy::policy()->delay_compilation(nm->method()); 516 nm->make_not_entrant(); 517 made_not_entrant++; 518 } 519 520 if (curr_comp_id > _highest_marked) { 521 _highest_marked = curr_comp_id; 522 } 523 } 524 nm = CodeCache::alive_nmethod(CodeCache::next(nm)); 525 } 526 527 log_sweep("stop_cleaning", 528 "disconnected='" UINT32_FORMAT "' made_not_entrant='" UINT32_FORMAT "'", 529 disconnected, made_not_entrant); 530 531 // Shut off compiler. Sweeper will start over with a new stack scan and 532 // traversal cycle and turn it back on if it clears enough space. 533 if (was_full()) { 534 _last_was_full = os::javaTimeMillis(); 535 CompileBroker::set_should_compile_new_jobs(CompileBroker::stop_compilation); 536 } 537 538 // After two more traversals the sweeper will get rid of unrestored nmethods 539 _was_full_traversal = _traversals; 540#ifdef ASSERT 541 jlong end = os::javaTimeMillis(); 542 if(PrintMethodFlushing && Verbose) { 543 tty->print_cr("### sweeper: unload time: " INT64_FORMAT, end-start); 544 } 545#endif 546} 547 548 549// Print out some state information about the current sweep and the 550// state of the code cache if it's requested. 551void NMethodSweeper::log_sweep(const char* msg, const char* format, ...) { 552 if (PrintMethodFlushing) { 553 stringStream s; 554 // Dump code cache state into a buffer before locking the tty, 555 // because log_state() will use locks causing lock conflicts. 556 CodeCache::log_state(&s); 557 558 ttyLocker ttyl; 559 tty->print("### sweeper: %s ", msg); 560 if (format != NULL) { 561 va_list ap; 562 va_start(ap, format); 563 tty->vprint(format, ap); 564 va_end(ap); 565 } 566 tty->print_cr(s.as_string()); 567 } 568 569 if (LogCompilation && (xtty != NULL)) { 570 stringStream s; 571 // Dump code cache state into a buffer before locking the tty, 572 // because log_state() will use locks causing lock conflicts. 573 CodeCache::log_state(&s); 574 575 ttyLocker ttyl; 576 xtty->begin_elem("sweeper state='%s' traversals='" INTX_FORMAT "' ", msg, (intx)traversal_count()); 577 if (format != NULL) { 578 va_list ap; 579 va_start(ap, format); 580 xtty->vprint(format, ap); 581 va_end(ap); 582 } 583 xtty->print(s.as_string()); 584 xtty->stamp(); 585 xtty->end_elem(); 586 } 587} 588