1 /* 2 * Copyright (c) 1997, 2014, 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.inline.hpp" 34 #include "runtime/compilationPolicy.hpp" 35 #include "runtime/mutexLocker.hpp" 36 #include "runtime/orderAccess.inline.hpp" 37 #include "runtime/os.hpp" 38 #include "runtime/sweeper.hpp" 39 #include "runtime/thread.inline.hpp" 40 #include "runtime/vm_operations.hpp" 41 #include "trace/tracing.hpp" 42 #include "utilities/events.hpp" 43 #include "utilities/ticks.inline.hpp" 44 #include "utilities/xmlstream.hpp" 45 46 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC 47 48 #ifdef ASSERT 49 50 #define SWEEP(nm) record_sweep(nm, __LINE__) 51 // Sweeper logging code 52 class SweeperRecord { 53 public: 54 int traversal; 55 int compile_id; 56 long traversal_mark; 57 int state; 58 const char* kind; 59 address vep; 60 address uep; 61 int line; 62 63 void print() { 64 tty->print_cr("traversal = %d compile_id = %d %s uep = " PTR_FORMAT " vep = " 65 PTR_FORMAT " state = %d traversal_mark %d line = %d", 66 traversal, 67 compile_id, 68 kind == NULL ? "" : kind, 69 uep, 70 vep, 71 state, 72 traversal_mark, 73 line); 74 } 75 }; 76 77 static int _sweep_index = 0; 78 static SweeperRecord* _records = NULL; 79 80 void NMethodSweeper::report_events(int id, address entry) { 81 if (_records != NULL) { 82 for (int i = _sweep_index; i < SweeperLogEntries; i++) { 83 if (_records[i].uep == entry || 84 _records[i].vep == entry || 85 _records[i].compile_id == id) { 86 _records[i].print(); 87 } 88 } 89 for (int i = 0; i < _sweep_index; i++) { 90 if (_records[i].uep == entry || 91 _records[i].vep == entry || 92 _records[i].compile_id == id) { 93 _records[i].print(); 94 } 95 } 96 } 97 } 98 99 void NMethodSweeper::report_events() { 100 if (_records != NULL) { 101 for (int i = _sweep_index; i < SweeperLogEntries; i++) { 102 // skip empty records 103 if (_records[i].vep == NULL) continue; 104 _records[i].print(); 105 } 106 for (int i = 0; i < _sweep_index; i++) { 107 // skip empty records 108 if (_records[i].vep == NULL) continue; 109 _records[i].print(); 110 } 111 } 112 } 113 114 void NMethodSweeper::record_sweep(nmethod* nm, int line) { 115 if (_records != NULL) { 116 _records[_sweep_index].traversal = _traversals; 117 _records[_sweep_index].traversal_mark = nm->_stack_traversal_mark; 118 _records[_sweep_index].compile_id = nm->compile_id(); 119 _records[_sweep_index].kind = nm->compile_kind(); 120 _records[_sweep_index].state = nm->_state; 121 _records[_sweep_index].vep = nm->verified_entry_point(); 122 _records[_sweep_index].uep = nm->entry_point(); 123 _records[_sweep_index].line = line; 124 _sweep_index = (_sweep_index + 1) % SweeperLogEntries; 125 } 126 } 127 128 void NMethodSweeper::init_sweeper_log() { 129 if (LogSweeper && _records == NULL) { 130 // Create the ring buffer for the logging code 131 _records = NEW_C_HEAP_ARRAY(SweeperRecord, SweeperLogEntries, mtGC); 132 memset(_records, 0, sizeof(SweeperRecord) * SweeperLogEntries); 133 } 134 } 135 #else 136 #define SWEEP(nm) 137 #endif 138 139 NMethodIterator NMethodSweeper::_current; // Current nmethod 140 long NMethodSweeper::_traversals = 0; // Stack scan count, also sweep ID. 141 long NMethodSweeper::_total_nof_code_cache_sweeps = 0; // Total number of full sweeps of the code cache 142 long NMethodSweeper::_time_counter = 0; // Virtual time used to periodically invoke sweeper 143 long NMethodSweeper::_last_sweep = 0; // Value of _time_counter when the last sweep happened 144 int NMethodSweeper::_seen = 0; // Nof. nmethod we have currently processed in current pass of CodeCache 145 146 volatile bool NMethodSweeper::_should_sweep = true; // Indicates if we should invoke the sweeper 147 volatile bool NMethodSweeper::_force_sweep = false;// Indicates if we should force a sweep 148 volatile int NMethodSweeper::_bytes_changed = 0; // Counts the total nmethod size if the nmethod changed from: 149 // 1) alive -> not_entrant 150 // 2) not_entrant -> zombie 151 // 3) zombie -> marked_for_reclamation 152 int NMethodSweeper::_hotness_counter_reset_val = 0; 153 154 long NMethodSweeper::_total_nof_methods_reclaimed = 0; // Accumulated nof methods flushed 155 long NMethodSweeper::_total_nof_c2_methods_reclaimed = 0; // Accumulated nof methods flushed 156 size_t NMethodSweeper::_total_flushed_size = 0; // Total number of bytes flushed from the code cache 157 Tickspan NMethodSweeper::_total_time_sweeping; // Accumulated time sweeping 158 Tickspan NMethodSweeper::_total_time_this_sweep; // Total time this sweep 159 Tickspan NMethodSweeper::_peak_sweep_time; // Peak time for a full sweep 160 Tickspan NMethodSweeper::_peak_sweep_fraction_time; // Peak time sweeping one fraction 161 162 Monitor* NMethodSweeper::_stat_lock = new Monitor(Mutex::special, "Sweeper::Statistics", true, Monitor::_safepoint_check_sometimes); 163 164 class MarkActivationClosure: public CodeBlobClosure { 165 public: 166 virtual void do_code_blob(CodeBlob* cb) { 167 assert(cb->is_nmethod(), "CodeBlob should be nmethod"); 168 nmethod* nm = (nmethod*)cb; 169 nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val()); 170 // If we see an activation belonging to a non_entrant nmethod, we mark it. 171 if (nm->is_not_entrant()) { 172 nm->mark_as_seen_on_stack(); 173 } 174 } 175 }; 176 static MarkActivationClosure mark_activation_closure; 177 178 class SetHotnessClosure: public CodeBlobClosure { 179 public: 180 virtual void do_code_blob(CodeBlob* cb) { 181 assert(cb->is_nmethod(), "CodeBlob should be nmethod"); 182 nmethod* nm = (nmethod*)cb; 183 nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val()); 184 } 185 }; 186 static SetHotnessClosure set_hotness_closure; 187 188 189 int NMethodSweeper::hotness_counter_reset_val() { 190 if (_hotness_counter_reset_val == 0) { 191 _hotness_counter_reset_val = (ReservedCodeCacheSize < M) ? 1 : (ReservedCodeCacheSize / M) * 2; 192 } 193 return _hotness_counter_reset_val; 194 } 195 bool NMethodSweeper::wait_for_stack_scanning() { 196 return _current.end(); 197 } 198 199 /** 200 * Scans the stacks of all Java threads and marks activations of not-entrant methods. 201 * No need to synchronize access, since 'mark_active_nmethods' is always executed at a 202 * safepoint. 203 */ 204 void NMethodSweeper::mark_active_nmethods() { 205 assert(SafepointSynchronize::is_at_safepoint(), "must be executed at a safepoint"); 206 // If we do not want to reclaim not-entrant or zombie methods there is no need 207 // to scan stacks 208 if (!MethodFlushing) { 209 return; 210 } 211 212 // Increase time so that we can estimate when to invoke the sweeper again. 213 _time_counter++; 214 215 // Check for restart 216 assert(CodeCache::find_blob_unsafe(_current.method()) == _current.method(), "Sweeper nmethod cached state invalid"); 217 if (wait_for_stack_scanning()) { 218 _seen = 0; 219 _current = NMethodIterator(); 220 // Initialize to first nmethod 221 _current.next(); 222 _traversals += 1; 223 _total_time_this_sweep = Tickspan(); 224 225 if (PrintMethodFlushing) { 226 tty->print_cr("### Sweep: stack traversal %d", _traversals); 227 } 228 Threads::nmethods_do(&mark_activation_closure); 229 230 } else { 231 // Only set hotness counter 232 Threads::nmethods_do(&set_hotness_closure); 233 } 234 235 OrderAccess::storestore(); 236 } 237 238 /** 239 * This function triggers a VM operation that does stack scanning of active 240 * methods. Stack scanning is mandatory for the sweeper to make progress. 241 */ 242 void NMethodSweeper::do_stack_scanning() { 243 assert(!CodeCache_lock->owned_by_self(), "just checking"); 244 if (wait_for_stack_scanning()) { 245 VM_MarkActiveNMethods op; 246 VMThread::execute(&op); 247 _should_sweep = true; 248 } 249 } 250 251 void NMethodSweeper::sweeper_loop() { 252 bool timeout; 253 while (true) { 254 { 255 ThreadBlockInVM tbivm(JavaThread::current()); 256 MutexLockerEx waiter(CodeCache_lock, Mutex::_no_safepoint_check_flag); 257 const long wait_time = 60*60*24 * 1000; 258 timeout = CodeCache_lock->wait(Mutex::_no_safepoint_check_flag, wait_time); 259 } 260 if (!timeout) { 261 possibly_sweep(); 262 } 263 } 264 } 265 266 /** 267 * Wakes up the sweeper thread to possibly sweep. 268 */ 269 void NMethodSweeper::notify(int code_blob_type) { 270 // Makes sure that we do not invoke the sweeper too often during startup. 271 double start_threshold = 100.0 / (double)StartAggressiveSweepingAt; 272 double aggressive_sweep_threshold = MIN2(start_threshold, 1.1); 273 if (CodeCache::reverse_free_ratio(code_blob_type) >= aggressive_sweep_threshold) { 274 assert_locked_or_safepoint(CodeCache_lock); 275 CodeCache_lock->notify(); 276 } 277 } 278 279 /** 280 * Wakes up the sweeper thread and forces a sweep. Blocks until it finished. 281 */ 282 void NMethodSweeper::force_sweep() { 283 ThreadBlockInVM tbivm(JavaThread::current()); 284 MutexLockerEx waiter(CodeCache_lock, Mutex::_no_safepoint_check_flag); 285 // Request forced sweep 286 _force_sweep = true; 287 while (_force_sweep) { 288 // Notify sweeper that we want to force a sweep and wait for completion. 289 // In case a sweep currently takes place we timeout and try again because 290 // we want to enforce a full sweep. 291 CodeCache_lock->notify(); 292 CodeCache_lock->wait(Mutex::_no_safepoint_check_flag, 1000); 293 } 294 } 295 296 /** 297 * Handle a safepoint request 298 */ 299 void NMethodSweeper::handle_safepoint_request() { 300 if (SafepointSynchronize::is_synchronizing()) { 301 if (PrintMethodFlushing && Verbose) { 302 tty->print_cr("### Sweep at %d out of %d, yielding to safepoint", _seen, CodeCache::nof_nmethods()); 303 } 304 MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag); 305 306 JavaThread* thread = JavaThread::current(); 307 ThreadBlockInVM tbivm(thread); 308 thread->java_suspend_self(); 309 } 310 } 311 312 /** 313 * This function invokes the sweeper if at least one of the three conditions is met: 314 * (1) The code cache is getting full 315 * (2) There are sufficient state changes in/since the last sweep. 316 * (3) We have not been sweeping for 'some time' 317 */ 318 void NMethodSweeper::possibly_sweep() { 319 assert(JavaThread::current()->thread_state() == _thread_in_vm, "must run in vm mode"); 320 // If there was no state change while nmethod sweeping, 'should_sweep' will be false. 321 // This is one of the two places where should_sweep can be set to true. The general 322 // idea is as follows: If there is enough free space in the code cache, there is no 323 // need to invoke the sweeper. The following formula (which determines whether to invoke 324 // the sweeper or not) depends on the assumption that for larger ReservedCodeCacheSizes 325 // we need less frequent sweeps than for smaller ReservedCodecCacheSizes. Furthermore, 326 // the formula considers how much space in the code cache is currently used. Here are 327 // some examples that will (hopefully) help in understanding. 328 // 329 // Small ReservedCodeCacheSizes: (e.g., < 16M) We invoke the sweeper every time, since 330 // the result of the division is 0. This 331 // keeps the used code cache size small 332 // (important for embedded Java) 333 // Large ReservedCodeCacheSize : (e.g., 256M + code cache is 10% full). The formula 334 // computes: (256 / 16) - 1 = 15 335 // As a result, we invoke the sweeper after 336 // 15 invocations of 'mark_active_nmethods. 337 // Large ReservedCodeCacheSize: (e.g., 256M + code Cache is 90% full). The formula 338 // computes: (256 / 16) - 10 = 6. 339 if (!_should_sweep) { 340 const int time_since_last_sweep = _time_counter - _last_sweep; 341 // ReservedCodeCacheSize has an 'unsigned' type. We need a 'signed' type for max_wait_time, 342 // since 'time_since_last_sweep' can be larger than 'max_wait_time'. If that happens using 343 // an unsigned type would cause an underflow (wait_until_next_sweep becomes a large positive 344 // value) that disables the intended periodic sweeps. 345 const int max_wait_time = ReservedCodeCacheSize / (16 * M); 346 double wait_until_next_sweep = max_wait_time - time_since_last_sweep - 347 MAX2(CodeCache::reverse_free_ratio(CodeBlobType::MethodProfiled), 348 CodeCache::reverse_free_ratio(CodeBlobType::MethodNonProfiled)); 349 assert(wait_until_next_sweep <= (double)max_wait_time, "Calculation of code cache sweeper interval is incorrect"); 350 351 if ((wait_until_next_sweep <= 0.0) || !CompileBroker::should_compile_new_jobs()) { 352 _should_sweep = true; 353 } 354 } 355 356 // Remember if this was a forced sweep 357 bool forced = _force_sweep; 358 359 // Force stack scanning if there is only 10% free space in the code cache. 360 // We force stack scanning only non-profiled code heap gets full, since critical 361 // allocation go to the non-profiled heap and we must be make sure that there is 362 // enough space. 363 double free_percent = 1 / CodeCache::reverse_free_ratio(CodeBlobType::MethodNonProfiled) * 100; 364 if (free_percent <= StartAggressiveSweepingAt) { 365 do_stack_scanning(); 366 } 367 368 if (_should_sweep || forced) { 369 init_sweeper_log(); 370 sweep_code_cache(); 371 } 372 373 // We are done with sweeping the code cache once. 374 _total_nof_code_cache_sweeps++; 375 _last_sweep = _time_counter; 376 // Reset flag; temporarily disables sweeper 377 _should_sweep = false; 378 // If there was enough state change, 'possibly_enable_sweeper()' 379 // sets '_should_sweep' to true 380 possibly_enable_sweeper(); 381 // Reset _bytes_changed only if there was enough state change. _bytes_changed 382 // can further increase by calls to 'report_state_change'. 383 if (_should_sweep) { 384 _bytes_changed = 0; 385 } 386 387 if (forced) { 388 // Notify requester that forced sweep finished 389 assert(_force_sweep, "Should be a forced sweep"); 390 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag); 391 _force_sweep = false; 392 CodeCache_lock->notify(); 393 } 394 } 395 396 void NMethodSweeper::sweep_code_cache() { 397 ResourceMark rm; 398 Ticks sweep_start_counter = Ticks::now(); 399 400 int flushed_count = 0; 401 int zombified_count = 0; 402 int marked_for_reclamation_count = 0; 403 int flushed_c2_count = 0; 404 405 if (PrintMethodFlushing && Verbose) { 406 tty->print_cr("### Sweep at %d out of %d", _seen, CodeCache::nof_nmethods()); 407 } 408 409 int swept_count = 0; 410 assert(!SafepointSynchronize::is_at_safepoint(), "should not be in safepoint when we get here"); 411 assert(!CodeCache_lock->owned_by_self(), "just checking"); 412 413 int freed_memory = 0; 414 { 415 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag); 416 417 while (!_current.end()) { 418 swept_count++; 419 // Since we will give up the CodeCache_lock, always skip ahead 420 // to the next nmethod. Other blobs can be deleted by other 421 // threads but nmethods are only reclaimed by the sweeper. 422 nmethod* nm = _current.method(); 423 _current.next(); 424 425 // Now ready to process nmethod and give up CodeCache_lock 426 { 427 MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag); 428 int size = nm->total_size(); 429 bool is_c2_method = nm->is_compiled_by_c2(); 430 431 MethodStateChange type = process_nmethod(nm); 432 switch (type) { 433 case Flushed: 434 freed_memory += size; 435 ++flushed_count; 436 if (is_c2_method) { 437 ++flushed_c2_count; 438 } 439 break; 440 case MarkedForReclamation: 441 ++marked_for_reclamation_count; 442 break; 443 case MadeZombie: 444 ++zombified_count; 445 break; 446 case None: 447 break; 448 default: 449 ShouldNotReachHere(); 450 } 451 } 452 _seen++; 453 handle_safepoint_request(); 454 } 455 } 456 457 assert(_current.end(), "must have scanned the whole cache"); 458 459 const Ticks sweep_end_counter = Ticks::now(); 460 const Tickspan sweep_time = sweep_end_counter - sweep_start_counter; 461 { 462 MutexLockerEx mu(_stat_lock, Mutex::_no_safepoint_check_flag); 463 _total_time_sweeping += sweep_time; 464 _total_time_this_sweep += sweep_time; 465 _peak_sweep_fraction_time = MAX2(sweep_time, _peak_sweep_fraction_time); 466 _total_flushed_size += freed_memory; 467 _total_nof_methods_reclaimed += flushed_count; 468 _total_nof_c2_methods_reclaimed += flushed_c2_count; 469 _peak_sweep_time = MAX2(_peak_sweep_time, _total_time_this_sweep); 470 } 471 EventSweepCodeCache event(UNTIMED); 472 if (event.should_commit()) { 473 event.set_starttime(sweep_start_counter); 474 event.set_endtime(sweep_end_counter); 475 event.set_sweepIndex(_traversals); 476 event.set_sweptCount(swept_count); 477 event.set_flushedCount(flushed_count); 478 event.set_markedCount(marked_for_reclamation_count); 479 event.set_zombifiedCount(zombified_count); 480 event.commit(); 481 } 482 483 #ifdef ASSERT 484 if(PrintMethodFlushing) { 485 tty->print_cr("### sweeper: sweep time(%d): ", (jlong)sweep_time.value()); 486 } 487 #endif 488 489 log_sweep("finished"); 490 491 // Sweeper is the only case where memory is released, check here if it 492 // is time to restart the compiler. Only checking if there is a certain 493 // amount of free memory in the code cache might lead to re-enabling 494 // compilation although no memory has been released. For example, there are 495 // cases when compilation was disabled although there is 4MB (or more) free 496 // memory in the code cache. The reason is code cache fragmentation. Therefore, 497 // it only makes sense to re-enable compilation if we have actually freed memory. 498 // Note that typically several kB are released for sweeping 16MB of the code 499 // cache. As a result, 'freed_memory' > 0 to restart the compiler. 500 if (!CompileBroker::should_compile_new_jobs() && (freed_memory > 0)) { 501 CompileBroker::set_should_compile_new_jobs(CompileBroker::run_compilation); 502 log_sweep("restart_compiler"); 503 } 504 } 505 506 /** 507 * This function updates the sweeper statistics that keep track of nmethods 508 * state changes. If there is 'enough' state change, the sweeper is invoked 509 * as soon as possible. There can be data races on _bytes_changed. The data 510 * races are benign, since it does not matter if we loose a couple of bytes. 511 * In the worst case we call the sweeper a little later. Also, we are guaranteed 512 * to invoke the sweeper if the code cache gets full. 513 */ 514 void NMethodSweeper::report_state_change(nmethod* nm) { 515 _bytes_changed += nm->total_size(); 516 possibly_enable_sweeper(); 517 } 518 519 /** 520 * Function determines if there was 'enough' state change in the code cache to invoke 521 * the sweeper again. Currently, we determine 'enough' as more than 1% state change in 522 * the code cache since the last sweep. 523 */ 524 void NMethodSweeper::possibly_enable_sweeper() { 525 double percent_changed = ((double)_bytes_changed / (double)ReservedCodeCacheSize) * 100; 526 if (percent_changed > 1.0) { 527 _should_sweep = true; 528 } 529 } 530 531 class NMethodMarker: public StackObj { 532 private: 533 CodeCacheSweeperThread* _thread; 534 public: 535 NMethodMarker(nmethod* nm) { 536 JavaThread* current = JavaThread::current(); 537 assert (current->is_Code_cache_sweeper_thread(), "Must be"); 538 _thread = (CodeCacheSweeperThread*)JavaThread::current(); 539 if (!nm->is_zombie() && !nm->is_unloaded()) { 540 // Only expose live nmethods for scanning 541 _thread->set_scanned_nmethod(nm); 542 } 543 } 544 ~NMethodMarker() { 545 _thread->set_scanned_nmethod(NULL); 546 } 547 }; 548 549 void NMethodSweeper::release_nmethod(nmethod* nm) { 550 // Clean up any CompiledICHolders 551 { 552 ResourceMark rm; 553 MutexLocker ml_patch(CompiledIC_lock); 554 RelocIterator iter(nm); 555 while (iter.next()) { 556 if (iter.type() == relocInfo::virtual_call_type) { 557 CompiledIC::cleanup_call_site(iter.virtual_call_reloc()); 558 } 559 } 560 } 561 562 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag); 563 nm->flush(); 564 } 565 566 NMethodSweeper::MethodStateChange NMethodSweeper::process_nmethod(nmethod* nm) { 567 assert(nm != NULL, "sanity"); 568 assert(!CodeCache_lock->owned_by_self(), "just checking"); 569 570 MethodStateChange result = None; 571 // Make sure this nmethod doesn't get unloaded during the scan, 572 // since safepoints may happen during acquired below locks. 573 NMethodMarker nmm(nm); 574 SWEEP(nm); 575 576 // Skip methods that are currently referenced by the VM 577 if (nm->is_locked_by_vm()) { 578 // But still remember to clean-up inline caches for alive nmethods 579 if (nm->is_alive()) { 580 // Clean inline caches that point to zombie/non-entrant methods 581 MutexLocker cl(CompiledIC_lock); 582 nm->cleanup_inline_caches(); 583 SWEEP(nm); 584 } 585 return result; 586 } 587 588 if (nm->is_zombie()) { 589 // If it is the first time we see nmethod then we mark it. Otherwise, 590 // we reclaim it. When we have seen a zombie method twice, we know that 591 // there are no inline caches that refer to it. 592 if (nm->is_marked_for_reclamation()) { 593 assert(!nm->is_locked_by_vm(), "must not flush locked nmethods"); 594 if (PrintMethodFlushing && Verbose) { 595 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (marked for reclamation) being flushed", nm->compile_id(), nm); 596 } 597 release_nmethod(nm); 598 assert(result == None, "sanity"); 599 result = Flushed; 600 } else { 601 if (PrintMethodFlushing && Verbose) { 602 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (zombie) being marked for reclamation", nm->compile_id(), nm); 603 } 604 nm->mark_for_reclamation(); 605 // Keep track of code cache state change 606 _bytes_changed += nm->total_size(); 607 SWEEP(nm); 608 assert(result == None, "sanity"); 609 result = MarkedForReclamation; 610 } 611 } else if (nm->is_not_entrant()) { 612 // If there are no current activations of this method on the 613 // stack we can safely convert it to a zombie method 614 if (nm->can_convert_to_zombie()) { 615 // Clear ICStubs to prevent back patching stubs of zombie or unloaded 616 // nmethods during the next safepoint (see ICStub::finalize). 617 { 618 MutexLocker cl(CompiledIC_lock); 619 nm->clear_ic_stubs(); 620 } 621 if (PrintMethodFlushing && Verbose) { 622 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (not entrant) being made zombie", nm->compile_id(), nm); 623 } 624 // Code cache state change is tracked in make_zombie() 625 nm->make_zombie(); 626 SWEEP(nm); 627 assert(result == None, "sanity"); 628 result = MadeZombie; 629 assert(nm->is_zombie(), "nmethod must be zombie"); 630 } else { 631 // Still alive, clean up its inline caches 632 MutexLocker cl(CompiledIC_lock); 633 nm->cleanup_inline_caches(); 634 SWEEP(nm); 635 } 636 } else if (nm->is_unloaded()) { 637 // Unloaded code, just make it a zombie 638 if (PrintMethodFlushing && Verbose) { 639 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (unloaded) being made zombie", nm->compile_id(), nm); 640 } 641 if (nm->is_osr_method()) { 642 SWEEP(nm); 643 // No inline caches will ever point to osr methods, so we can just remove it 644 release_nmethod(nm); 645 assert(result == None, "sanity"); 646 result = Flushed; 647 } else { 648 { 649 // Clean ICs of unloaded nmethods as well because they may reference other 650 // unloaded nmethods that may be flushed earlier in the sweeper cycle. 651 MutexLocker cl(CompiledIC_lock); 652 nm->cleanup_inline_caches(); 653 } 654 // Code cache state change is tracked in make_zombie() 655 nm->make_zombie(); 656 SWEEP(nm); 657 assert(result == None, "sanity"); 658 result = MadeZombie; 659 } 660 } else { 661 possibly_flush(nm); 662 // Clean-up all inline caches that point to zombie/non-reentrant methods 663 MutexLocker cl(CompiledIC_lock); 664 nm->cleanup_inline_caches(); 665 SWEEP(nm); 666 } 667 return result; 668 } 669 670 671 void NMethodSweeper::possibly_flush(nmethod* nm) { 672 if (UseCodeCacheFlushing) { 673 if (!nm->is_locked_by_vm() && !nm->is_osr_method() && !nm->is_native_method()) { 674 bool make_not_entrant = false; 675 676 // Do not make native methods and OSR-methods not-entrant 677 nm->dec_hotness_counter(); 678 // Get the initial value of the hotness counter. This value depends on the 679 // ReservedCodeCacheSize 680 int reset_val = hotness_counter_reset_val(); 681 int time_since_reset = reset_val - nm->hotness_counter(); 682 int code_blob_type = CodeCache::get_code_blob_type(nm); 683 double threshold = -reset_val + (CodeCache::reverse_free_ratio(code_blob_type) * NmethodSweepActivity); 684 // The less free space in the code cache we have - the bigger reverse_free_ratio() is. 685 // I.e., 'threshold' increases with lower available space in the code cache and a higher 686 // NmethodSweepActivity. If the current hotness counter - which decreases from its initial 687 // value until it is reset by stack walking - is smaller than the computed threshold, the 688 // corresponding nmethod is considered for removal. 689 if ((NmethodSweepActivity > 0) && (nm->hotness_counter() < threshold) && (time_since_reset > MinPassesBeforeFlush)) { 690 // A method is marked as not-entrant if the method is 691 // 1) 'old enough': nm->hotness_counter() < threshold 692 // 2) The method was in_use for a minimum amount of time: (time_since_reset > MinPassesBeforeFlush) 693 // The second condition is necessary if we are dealing with very small code cache 694 // sizes (e.g., <10m) and the code cache size is too small to hold all hot methods. 695 // The second condition ensures that methods are not immediately made not-entrant 696 // after compilation. 697 make_not_entrant = true; 698 } 699 700 // The stack-scanning low-cost detection may not see the method was used (which can happen for 701 // flat profiles). Check the age counter for possible data. 702 if (UseCodeAging && make_not_entrant && (nm->is_compiled_by_c2() || nm->is_compiled_by_c1())) { 703 MethodCounters* mc = nm->method()->get_method_counters(Thread::current()); 704 if (mc != NULL) { 705 // Snapshot the value as it's changed concurrently 706 int age = mc->nmethod_age(); 707 if (MethodCounters::is_nmethod_hot(age)) { 708 // The method has gone through flushing, and it became relatively hot that it deopted 709 // before we could take a look at it. Give it more time to appear in the stack traces, 710 // proportional to the number of deopts. 711 MethodData* md = nm->method()->method_data(); 712 if (md != NULL && time_since_reset > (int)(MinPassesBeforeFlush * (md->tenure_traps() + 1))) { 713 // It's been long enough, we still haven't seen it on stack. 714 // Try to flush it, but enable counters the next time. 715 mc->reset_nmethod_age(); 716 } else { 717 make_not_entrant = false; 718 } 719 } else if (MethodCounters::is_nmethod_warm(age)) { 720 // Method has counters enabled, and the method was used within 721 // previous MinPassesBeforeFlush sweeps. Reset the counter. Stay in the existing 722 // compiled state. 723 mc->reset_nmethod_age(); 724 // delay the next check 725 nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val()); 726 make_not_entrant = false; 727 } else if (MethodCounters::is_nmethod_age_unset(age)) { 728 // No counters were used before. Set the counters to the detection 729 // limit value. If the method is going to be used again it will be compiled 730 // with counters that we're going to use for analysis the the next time. 731 mc->reset_nmethod_age(); 732 } else { 733 // Method was totally idle for 10 sweeps 734 // The counter already has the initial value, flush it and may be recompile 735 // later with counters 736 } 737 } 738 } 739 740 if (make_not_entrant) { 741 nm->make_not_entrant(); 742 743 // Code cache state change is tracked in make_not_entrant() 744 if (PrintMethodFlushing && Verbose) { 745 tty->print_cr("### Nmethod %d/" PTR_FORMAT "made not-entrant: hotness counter %d/%d threshold %f", 746 nm->compile_id(), nm, nm->hotness_counter(), reset_val, threshold); 747 } 748 } 749 } 750 } 751 } 752 753 // Print out some state information about the current sweep and the 754 // state of the code cache if it's requested. 755 void NMethodSweeper::log_sweep(const char* msg, const char* format, ...) { 756 if (PrintMethodFlushing) { 757 ResourceMark rm; 758 stringStream s; 759 // Dump code cache state into a buffer before locking the tty, 760 // because log_state() will use locks causing lock conflicts. 761 CodeCache::log_state(&s); 762 763 ttyLocker ttyl; 764 tty->print("### sweeper: %s ", msg); 765 if (format != NULL) { 766 va_list ap; 767 va_start(ap, format); 768 tty->vprint(format, ap); 769 va_end(ap); 770 } 771 tty->print_cr("%s", s.as_string()); 772 } 773 774 if (LogCompilation && (xtty != NULL)) { 775 ResourceMark rm; 776 stringStream s; 777 // Dump code cache state into a buffer before locking the tty, 778 // because log_state() will use locks causing lock conflicts. 779 CodeCache::log_state(&s); 780 781 ttyLocker ttyl; 782 xtty->begin_elem("sweeper state='%s' traversals='" INTX_FORMAT "' ", msg, (intx)traversal_count()); 783 if (format != NULL) { 784 va_list ap; 785 va_start(ap, format); 786 xtty->vprint(format, ap); 787 va_end(ap); 788 } 789 xtty->print("%s", s.as_string()); 790 xtty->stamp(); 791 xtty->end_elem(); 792 } 793 } 794 795 void NMethodSweeper::print() { 796 ttyLocker ttyl; 797 tty->print_cr("Code cache sweeper statistics:"); 798 tty->print_cr(" Total sweep time: %1.0lfms", (double)_total_time_sweeping.value()/1000000); 799 tty->print_cr(" Total number of full sweeps: %ld", _total_nof_code_cache_sweeps); 800 tty->print_cr(" Total number of flushed methods: %ld(%ld C2 methods)", _total_nof_methods_reclaimed, 801 _total_nof_c2_methods_reclaimed); 802 tty->print_cr(" Total size of flushed methods: " SIZE_FORMAT "kB", _total_flushed_size/K); 803 }