1 /* 2 * Copyright (c) 1997, 2016, 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/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 #ifdef ASSERT 47 48 #define SWEEP(nm) record_sweep(nm, __LINE__) 49 // Sweeper logging code 50 class SweeperRecord { 51 public: 52 int traversal; 53 int compile_id; 54 long traversal_mark; 55 int state; 56 const char* kind; 57 address vep; 58 address uep; 59 int line; 60 61 void print() { 62 tty->print_cr("traversal = %d compile_id = %d %s uep = " PTR_FORMAT " vep = " 63 PTR_FORMAT " state = %d traversal_mark %ld line = %d", 64 traversal, 65 compile_id, 66 kind == NULL ? "" : kind, 67 p2i(uep), 68 p2i(vep), 69 state, 70 traversal_mark, 71 line); 72 } 73 }; 74 75 static int _sweep_index = 0; 76 static SweeperRecord* _records = NULL; 77 78 void NMethodSweeper::report_events(int id, address entry) { 79 if (_records != NULL) { 80 for (int i = _sweep_index; i < SweeperLogEntries; i++) { 81 if (_records[i].uep == entry || 82 _records[i].vep == entry || 83 _records[i].compile_id == id) { 84 _records[i].print(); 85 } 86 } 87 for (int i = 0; i < _sweep_index; i++) { 88 if (_records[i].uep == entry || 89 _records[i].vep == entry || 90 _records[i].compile_id == id) { 91 _records[i].print(); 92 } 93 } 94 } 95 } 96 97 void NMethodSweeper::report_events() { 98 if (_records != NULL) { 99 for (int i = _sweep_index; i < SweeperLogEntries; i++) { 100 // skip empty records 101 if (_records[i].vep == NULL) continue; 102 _records[i].print(); 103 } 104 for (int i = 0; i < _sweep_index; i++) { 105 // skip empty records 106 if (_records[i].vep == NULL) continue; 107 _records[i].print(); 108 } 109 } 110 } 111 112 void NMethodSweeper::record_sweep(CompiledMethod* nm, int line) { 113 if (_records != NULL) { 114 _records[_sweep_index].traversal = _traversals; 115 _records[_sweep_index].traversal_mark = nm->is_nmethod() ? ((nmethod*)nm)->_stack_traversal_mark : 0; 116 _records[_sweep_index].compile_id = nm->compile_id(); 117 _records[_sweep_index].kind = nm->compile_kind(); 118 _records[_sweep_index].state = nm->get_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 _sweep_index = (_sweep_index + 1) % SweeperLogEntries; 123 } 124 } 125 126 void NMethodSweeper::init_sweeper_log() { 127 if (LogSweeper && _records == NULL) { 128 // Create the ring buffer for the logging code 129 _records = NEW_C_HEAP_ARRAY(SweeperRecord, SweeperLogEntries, mtGC); 130 memset(_records, 0, sizeof(SweeperRecord) * SweeperLogEntries); 131 } 132 } 133 #else 134 #define SWEEP(nm) 135 #endif 136 137 CompiledMethodIterator NMethodSweeper::_current; // Current compiled method 138 long NMethodSweeper::_traversals = 0; // Stack scan count, also sweep ID. 139 long NMethodSweeper::_total_nof_code_cache_sweeps = 0; // Total number of full sweeps of the code cache 140 long NMethodSweeper::_time_counter = 0; // Virtual time used to periodically invoke sweeper 141 long NMethodSweeper::_last_sweep = 0; // Value of _time_counter when the last sweep happened 142 int NMethodSweeper::_seen = 0; // Nof. nmethod we have currently processed in current pass of CodeCache 143 144 volatile bool NMethodSweeper::_should_sweep = true; // Indicates if we should invoke the sweeper 145 volatile bool NMethodSweeper::_force_sweep = false;// Indicates if we should force a sweep 146 volatile int NMethodSweeper::_bytes_changed = 0; // Counts the total nmethod size if the nmethod changed from: 147 // 1) alive -> not_entrant 148 // 2) not_entrant -> zombie 149 int NMethodSweeper::_hotness_counter_reset_val = 0; 150 151 long NMethodSweeper::_total_nof_methods_reclaimed = 0; // Accumulated nof methods flushed 152 long NMethodSweeper::_total_nof_c2_methods_reclaimed = 0; // Accumulated nof methods flushed 153 size_t NMethodSweeper::_total_flushed_size = 0; // Total number of bytes flushed from the code cache 154 Tickspan NMethodSweeper::_total_time_sweeping; // Accumulated time sweeping 155 Tickspan NMethodSweeper::_total_time_this_sweep; // Total time this sweep 156 Tickspan NMethodSweeper::_peak_sweep_time; // Peak time for a full sweep 157 Tickspan NMethodSweeper::_peak_sweep_fraction_time; // Peak time sweeping one fraction 158 159 Monitor* NMethodSweeper::_stat_lock = new Monitor(Mutex::special, "Sweeper::Statistics", true, Monitor::_safepoint_check_sometimes); 160 161 class MarkActivationClosure: public CodeBlobClosure { 162 public: 163 virtual void do_code_blob(CodeBlob* cb) { 164 assert(cb->is_nmethod(), "CodeBlob should be nmethod"); 165 nmethod* nm = (nmethod*)cb; 166 nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val()); 167 // If we see an activation belonging to a non_entrant nmethod, we mark it. 168 if (nm->is_not_entrant()) { 169 nm->mark_as_seen_on_stack(); 170 } 171 } 172 }; 173 static MarkActivationClosure mark_activation_closure; 174 175 class SetHotnessClosure: public CodeBlobClosure { 176 public: 177 virtual void do_code_blob(CodeBlob* cb) { 178 assert(cb->is_nmethod(), "CodeBlob should be nmethod"); 179 nmethod* nm = (nmethod*)cb; 180 nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val()); 181 } 182 }; 183 static SetHotnessClosure set_hotness_closure; 184 185 186 int NMethodSweeper::hotness_counter_reset_val() { 187 if (_hotness_counter_reset_val == 0) { 188 _hotness_counter_reset_val = (ReservedCodeCacheSize < M) ? 1 : (ReservedCodeCacheSize / M) * 2; 189 } 190 return _hotness_counter_reset_val; 191 } 192 bool NMethodSweeper::wait_for_stack_scanning() { 193 return _current.end(); 194 } 195 196 /** 197 * Scans the stacks of all Java threads and marks activations of not-entrant methods. 198 * No need to synchronize access, since 'mark_active_nmethods' is always executed at a 199 * safepoint. 200 */ 201 void NMethodSweeper::mark_active_nmethods() { 202 assert(SafepointSynchronize::is_at_safepoint(), "must be executed at a safepoint"); 203 // If we do not want to reclaim not-entrant or zombie methods there is no need 204 // to scan stacks 205 if (!MethodFlushing) { 206 return; 207 } 208 209 // Increase time so that we can estimate when to invoke the sweeper again. 210 _time_counter++; 211 212 // Check for restart 213 if (_current.method() != NULL) { 214 if (_current.method()->is_nmethod()) { 215 assert(CodeCache::find_blob_unsafe(_current.method()) == _current.method(), "Sweeper nmethod cached state invalid"); 216 } else if (_current.method()->is_aot()) { 217 assert(CodeCache::find_blob_unsafe(_current.method()->code_begin()) == _current.method(), "Sweeper AOT method cached state invalid"); 218 } else { 219 ShouldNotReachHere(); 220 } 221 } 222 223 if (wait_for_stack_scanning()) { 224 _seen = 0; 225 _current = CompiledMethodIterator(); 226 // Initialize to first nmethod 227 _current.next(); 228 _traversals += 1; 229 _total_time_this_sweep = Tickspan(); 230 231 if (PrintMethodFlushing) { 232 tty->print_cr("### Sweep: stack traversal %ld", _traversals); 233 } 234 Threads::nmethods_do(&mark_activation_closure); 235 236 } else { 237 // Only set hotness counter 238 Threads::nmethods_do(&set_hotness_closure); 239 } 240 241 OrderAccess::storestore(); 242 } 243 244 /** 245 * This function triggers a VM operation that does stack scanning of active 246 * methods. Stack scanning is mandatory for the sweeper to make progress. 247 */ 248 void NMethodSweeper::do_stack_scanning() { 249 assert(!CodeCache_lock->owned_by_self(), "just checking"); 250 if (wait_for_stack_scanning()) { 251 VM_MarkActiveNMethods op; 252 VMThread::execute(&op); 253 _should_sweep = true; 254 } 255 } 256 257 void NMethodSweeper::sweeper_loop() { 258 bool timeout; 259 while (true) { 260 { 261 ThreadBlockInVM tbivm(JavaThread::current()); 262 MutexLockerEx waiter(CodeCache_lock, Mutex::_no_safepoint_check_flag); 263 const long wait_time = 60*60*24 * 1000; 264 timeout = CodeCache_lock->wait(Mutex::_no_safepoint_check_flag, wait_time); 265 } 266 if (!timeout) { 267 possibly_sweep(); 268 } 269 } 270 } 271 272 /** 273 * Wakes up the sweeper thread to possibly sweep. 274 */ 275 void NMethodSweeper::notify(int code_blob_type) { 276 // Makes sure that we do not invoke the sweeper too often during startup. 277 double start_threshold = 100.0 / (double)StartAggressiveSweepingAt; 278 double aggressive_sweep_threshold = MIN2(start_threshold, 1.1); 279 if (CodeCache::reverse_free_ratio(code_blob_type) >= aggressive_sweep_threshold) { 280 assert_locked_or_safepoint(CodeCache_lock); 281 CodeCache_lock->notify(); 282 } 283 } 284 285 /** 286 * Wakes up the sweeper thread and forces a sweep. Blocks until it finished. 287 */ 288 void NMethodSweeper::force_sweep() { 289 ThreadBlockInVM tbivm(JavaThread::current()); 290 MutexLockerEx waiter(CodeCache_lock, Mutex::_no_safepoint_check_flag); 291 // Request forced sweep 292 _force_sweep = true; 293 while (_force_sweep) { 294 // Notify sweeper that we want to force a sweep and wait for completion. 295 // In case a sweep currently takes place we timeout and try again because 296 // we want to enforce a full sweep. 297 CodeCache_lock->notify(); 298 CodeCache_lock->wait(Mutex::_no_safepoint_check_flag, 1000); 299 } 300 } 301 302 /** 303 * Handle a safepoint request 304 */ 305 void NMethodSweeper::handle_safepoint_request() { 306 if (SafepointSynchronize::is_synchronizing()) { 307 if (PrintMethodFlushing && Verbose) { 308 tty->print_cr("### Sweep at %d out of %d, yielding to safepoint", _seen, CodeCache::nmethod_count()); 309 } 310 MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag); 311 312 JavaThread* thread = JavaThread::current(); 313 ThreadBlockInVM tbivm(thread); 314 thread->java_suspend_self(); 315 } 316 } 317 318 /** 319 * This function invokes the sweeper if at least one of the three conditions is met: 320 * (1) The code cache is getting full 321 * (2) There are sufficient state changes in/since the last sweep. 322 * (3) We have not been sweeping for 'some time' 323 */ 324 void NMethodSweeper::possibly_sweep() { 325 assert(JavaThread::current()->thread_state() == _thread_in_vm, "must run in vm mode"); 326 // If there was no state change while nmethod sweeping, 'should_sweep' will be false. 327 // This is one of the two places where should_sweep can be set to true. The general 328 // idea is as follows: If there is enough free space in the code cache, there is no 329 // need to invoke the sweeper. The following formula (which determines whether to invoke 330 // the sweeper or not) depends on the assumption that for larger ReservedCodeCacheSizes 331 // we need less frequent sweeps than for smaller ReservedCodecCacheSizes. Furthermore, 332 // the formula considers how much space in the code cache is currently used. Here are 333 // some examples that will (hopefully) help in understanding. 334 // 335 // Small ReservedCodeCacheSizes: (e.g., < 16M) We invoke the sweeper every time, since 336 // the result of the division is 0. This 337 // keeps the used code cache size small 338 // (important for embedded Java) 339 // Large ReservedCodeCacheSize : (e.g., 256M + code cache is 10% full). The formula 340 // computes: (256 / 16) - 1 = 15 341 // As a result, we invoke the sweeper after 342 // 15 invocations of 'mark_active_nmethods. 343 // Large ReservedCodeCacheSize: (e.g., 256M + code Cache is 90% full). The formula 344 // computes: (256 / 16) - 10 = 6. 345 if (!_should_sweep) { 346 const int time_since_last_sweep = _time_counter - _last_sweep; 347 // ReservedCodeCacheSize has an 'unsigned' type. We need a 'signed' type for max_wait_time, 348 // since 'time_since_last_sweep' can be larger than 'max_wait_time'. If that happens using 349 // an unsigned type would cause an underflow (wait_until_next_sweep becomes a large positive 350 // value) that disables the intended periodic sweeps. 351 const int max_wait_time = ReservedCodeCacheSize / (16 * M); 352 double wait_until_next_sweep = max_wait_time - time_since_last_sweep - 353 MAX2(CodeCache::reverse_free_ratio(CodeBlobType::MethodProfiled), 354 CodeCache::reverse_free_ratio(CodeBlobType::MethodNonProfiled)); 355 assert(wait_until_next_sweep <= (double)max_wait_time, "Calculation of code cache sweeper interval is incorrect"); 356 357 if ((wait_until_next_sweep <= 0.0) || !CompileBroker::should_compile_new_jobs()) { 358 _should_sweep = true; 359 } 360 } 361 362 // Remember if this was a forced sweep 363 bool forced = _force_sweep; 364 365 // Force stack scanning if there is only 10% free space in the code cache. 366 // We force stack scanning only if the non-profiled code heap gets full, since critical 367 // allocations go to the non-profiled heap and we must be make sure that there is 368 // enough space. 369 double free_percent = 1 / CodeCache::reverse_free_ratio(CodeBlobType::MethodNonProfiled) * 100; 370 if (free_percent <= StartAggressiveSweepingAt) { 371 do_stack_scanning(); 372 } 373 374 if (_should_sweep || forced) { 375 init_sweeper_log(); 376 sweep_code_cache(); 377 } 378 379 // We are done with sweeping the code cache once. 380 _total_nof_code_cache_sweeps++; 381 _last_sweep = _time_counter; 382 // Reset flag; temporarily disables sweeper 383 _should_sweep = false; 384 // If there was enough state change, 'possibly_enable_sweeper()' 385 // sets '_should_sweep' to true 386 possibly_enable_sweeper(); 387 // Reset _bytes_changed only if there was enough state change. _bytes_changed 388 // can further increase by calls to 'report_state_change'. 389 if (_should_sweep) { 390 _bytes_changed = 0; 391 } 392 393 if (forced) { 394 // Notify requester that forced sweep finished 395 assert(_force_sweep, "Should be a forced sweep"); 396 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag); 397 _force_sweep = false; 398 CodeCache_lock->notify(); 399 } 400 } 401 402 void NMethodSweeper::sweep_code_cache() { 403 ResourceMark rm; 404 Ticks sweep_start_counter = Ticks::now(); 405 406 log_debug(codecache, sweep, start)("CodeCache flushing"); 407 408 int flushed_count = 0; 409 int zombified_count = 0; 410 int flushed_c2_count = 0; 411 412 if (PrintMethodFlushing && Verbose) { 413 tty->print_cr("### Sweep at %d out of %d", _seen, CodeCache::nmethod_count()); 414 } 415 416 int swept_count = 0; 417 assert(!SafepointSynchronize::is_at_safepoint(), "should not be in safepoint when we get here"); 418 assert(!CodeCache_lock->owned_by_self(), "just checking"); 419 420 int freed_memory = 0; 421 { 422 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag); 423 424 while (!_current.end()) { 425 swept_count++; 426 // Since we will give up the CodeCache_lock, always skip ahead 427 // to the next nmethod. Other blobs can be deleted by other 428 // threads but nmethods are only reclaimed by the sweeper. 429 CompiledMethod* nm = _current.method(); 430 _current.next(); 431 432 // Now ready to process nmethod and give up CodeCache_lock 433 { 434 MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag); 435 // Save information before potentially flushing the nmethod 436 // Only flushing nmethods so size only matters for them. 437 int size = nm->is_nmethod() ? ((nmethod*)nm)->total_size() : 0; 438 bool is_c2_method = nm->is_compiled_by_c2(); 439 bool is_osr = nm->is_osr_method(); 440 int compile_id = nm->compile_id(); 441 intptr_t address = p2i(nm); 442 const char* state_before = nm->state(); 443 const char* state_after = ""; 444 445 MethodStateChange type = process_compiled_method(nm); 446 switch (type) { 447 case Flushed: 448 state_after = "flushed"; 449 freed_memory += size; 450 ++flushed_count; 451 if (is_c2_method) { 452 ++flushed_c2_count; 453 } 454 break; 455 case MadeZombie: 456 state_after = "made zombie"; 457 ++zombified_count; 458 break; 459 case None: 460 break; 461 default: 462 ShouldNotReachHere(); 463 } 464 if (PrintMethodFlushing && Verbose && type != None) { 465 tty->print_cr("### %s nmethod %3d/" PTR_FORMAT " (%s) %s", is_osr ? "osr" : "", compile_id, address, state_before, state_after); 466 } 467 } 468 469 _seen++; 470 handle_safepoint_request(); 471 } 472 } 473 474 assert(_current.end(), "must have scanned the whole cache"); 475 476 const Ticks sweep_end_counter = Ticks::now(); 477 const Tickspan sweep_time = sweep_end_counter - sweep_start_counter; 478 { 479 MutexLockerEx mu(_stat_lock, Mutex::_no_safepoint_check_flag); 480 _total_time_sweeping += sweep_time; 481 _total_time_this_sweep += sweep_time; 482 _peak_sweep_fraction_time = MAX2(sweep_time, _peak_sweep_fraction_time); 483 _total_flushed_size += freed_memory; 484 _total_nof_methods_reclaimed += flushed_count; 485 _total_nof_c2_methods_reclaimed += flushed_c2_count; 486 _peak_sweep_time = MAX2(_peak_sweep_time, _total_time_this_sweep); 487 } 488 EventSweepCodeCache event(UNTIMED); 489 if (event.should_commit()) { 490 event.set_starttime(sweep_start_counter); 491 event.set_endtime(sweep_end_counter); 492 event.set_sweepId(_traversals); 493 event.set_sweptCount(swept_count); 494 event.set_flushedCount(flushed_count); 495 event.set_zombifiedCount(zombified_count); 496 event.commit(); 497 } 498 499 #ifdef ASSERT 500 if(PrintMethodFlushing) { 501 tty->print_cr("### sweeper: sweep time(" JLONG_FORMAT "): ", sweep_time.value()); 502 } 503 #endif 504 505 Log(codecache, sweep) log; 506 if (log.is_debug()) { 507 CodeCache::print_summary(log.debug_stream(), false); 508 } 509 log_sweep("finished"); 510 511 // Sweeper is the only case where memory is released, check here if it 512 // is time to restart the compiler. Only checking if there is a certain 513 // amount of free memory in the code cache might lead to re-enabling 514 // compilation although no memory has been released. For example, there are 515 // cases when compilation was disabled although there is 4MB (or more) free 516 // memory in the code cache. The reason is code cache fragmentation. Therefore, 517 // it only makes sense to re-enable compilation if we have actually freed memory. 518 // Note that typically several kB are released for sweeping 16MB of the code 519 // cache. As a result, 'freed_memory' > 0 to restart the compiler. 520 if (!CompileBroker::should_compile_new_jobs() && (freed_memory > 0)) { 521 CompileBroker::set_should_compile_new_jobs(CompileBroker::run_compilation); 522 log.debug("restart compiler"); 523 log_sweep("restart_compiler"); 524 } 525 } 526 527 /** 528 * This function updates the sweeper statistics that keep track of nmethods 529 * state changes. If there is 'enough' state change, the sweeper is invoked 530 * as soon as possible. There can be data races on _bytes_changed. The data 531 * races are benign, since it does not matter if we loose a couple of bytes. 532 * In the worst case we call the sweeper a little later. Also, we are guaranteed 533 * to invoke the sweeper if the code cache gets full. 534 */ 535 void NMethodSweeper::report_state_change(nmethod* nm) { 536 _bytes_changed += nm->total_size(); 537 possibly_enable_sweeper(); 538 } 539 540 /** 541 * Function determines if there was 'enough' state change in the code cache to invoke 542 * the sweeper again. Currently, we determine 'enough' as more than 1% state change in 543 * the code cache since the last sweep. 544 */ 545 void NMethodSweeper::possibly_enable_sweeper() { 546 double percent_changed = ((double)_bytes_changed / (double)ReservedCodeCacheSize) * 100; 547 if (percent_changed > 1.0) { 548 _should_sweep = true; 549 } 550 } 551 552 class CompiledMethodMarker: public StackObj { 553 private: 554 CodeCacheSweeperThread* _thread; 555 public: 556 CompiledMethodMarker(CompiledMethod* cm) { 557 JavaThread* current = JavaThread::current(); 558 assert (current->is_Code_cache_sweeper_thread(), "Must be"); 559 _thread = (CodeCacheSweeperThread*)current; 560 if (!cm->is_zombie() && !cm->is_unloaded()) { 561 // Only expose live nmethods for scanning 562 _thread->set_scanned_compiled_method(cm); 563 } 564 } 565 ~CompiledMethodMarker() { 566 _thread->set_scanned_compiled_method(NULL); 567 } 568 }; 569 570 void NMethodSweeper::release_compiled_method(CompiledMethod* nm) { 571 // Make sure the released nmethod is no longer referenced by the sweeper thread 572 CodeCacheSweeperThread* thread = (CodeCacheSweeperThread*)JavaThread::current(); 573 thread->set_scanned_compiled_method(NULL); 574 575 // Clean up any CompiledICHolders 576 { 577 ResourceMark rm; 578 MutexLocker ml_patch(CompiledIC_lock); 579 RelocIterator iter(nm); 580 while (iter.next()) { 581 if (iter.type() == relocInfo::virtual_call_type) { 582 CompiledIC::cleanup_call_site(iter.virtual_call_reloc(), nm); 583 } 584 } 585 } 586 587 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag); 588 nm->flush(); 589 } 590 591 NMethodSweeper::MethodStateChange NMethodSweeper::process_compiled_method(CompiledMethod* cm) { 592 assert(cm != NULL, "sanity"); 593 assert(!CodeCache_lock->owned_by_self(), "just checking"); 594 595 MethodStateChange result = None; 596 // Make sure this nmethod doesn't get unloaded during the scan, 597 // since safepoints may happen during acquired below locks. 598 CompiledMethodMarker nmm(cm); 599 SWEEP(cm); 600 601 // Skip methods that are currently referenced by the VM 602 if (cm->is_locked_by_vm()) { 603 // But still remember to clean-up inline caches for alive nmethods 604 if (cm->is_alive()) { 605 // Clean inline caches that point to zombie/non-entrant/unloaded nmethods 606 MutexLocker cl(CompiledIC_lock); 607 cm->cleanup_inline_caches(); 608 SWEEP(cm); 609 } 610 return result; 611 } 612 613 if (cm->is_zombie()) { 614 // All inline caches that referred to this nmethod were cleaned in the 615 // previous sweeper cycle. Now flush the nmethod from the code cache. 616 assert(!cm->is_locked_by_vm(), "must not flush locked Compiled Methods"); 617 release_compiled_method(cm); 618 assert(result == None, "sanity"); 619 result = Flushed; 620 } else if (cm->is_not_entrant()) { 621 // If there are no current activations of this method on the 622 // stack we can safely convert it to a zombie method 623 if (cm->can_convert_to_zombie()) { 624 // Clear ICStubs to prevent back patching stubs of zombie or flushed 625 // nmethods during the next safepoint (see ICStub::finalize). 626 { 627 MutexLocker cl(CompiledIC_lock); 628 cm->clear_ic_stubs(); 629 } 630 // Code cache state change is tracked in make_zombie() 631 cm->make_zombie(); 632 SWEEP(cm); 633 // The nmethod may have been locked by JVMTI after being made zombie (see 634 // JvmtiDeferredEvent::compiled_method_unload_event()). If so, we cannot 635 // flush the osr nmethod directly but have to wait for a later sweeper cycle. 636 if (cm->is_osr_method() && !cm->is_locked_by_vm()) { 637 // No inline caches will ever point to osr methods, so we can just remove it. 638 // Make sure that we unregistered the nmethod with the heap and flushed all 639 // dependencies before removing the nmethod (done in make_zombie()). 640 assert(cm->is_zombie(), "nmethod must be unregistered"); 641 release_compiled_method(cm); 642 assert(result == None, "sanity"); 643 result = Flushed; 644 } else { 645 assert(result == None, "sanity"); 646 result = MadeZombie; 647 assert(cm->is_zombie(), "nmethod must be zombie"); 648 } 649 } else { 650 // Still alive, clean up its inline caches 651 MutexLocker cl(CompiledIC_lock); 652 cm->cleanup_inline_caches(); 653 SWEEP(cm); 654 } 655 } else if (cm->is_unloaded()) { 656 // Code is unloaded, so there are no activations on the stack. 657 // Convert the nmethod to zombie or flush it directly in the OSR case. 658 { 659 // Clean ICs of unloaded nmethods as well because they may reference other 660 // unloaded nmethods that may be flushed earlier in the sweeper cycle. 661 MutexLocker cl(CompiledIC_lock); 662 cm->cleanup_inline_caches(); 663 } 664 if (cm->is_osr_method()) { 665 SWEEP(cm); 666 // No inline caches will ever point to osr methods, so we can just remove it 667 release_compiled_method(cm); 668 assert(result == None, "sanity"); 669 result = Flushed; 670 } else { 671 // Code cache state change is tracked in make_zombie() 672 cm->make_zombie(); 673 SWEEP(cm); 674 assert(result == None, "sanity"); 675 result = MadeZombie; 676 } 677 } else { 678 if (cm->is_nmethod()) { 679 possibly_flush((nmethod*)cm); 680 } 681 // Clean inline caches that point to zombie/non-entrant/unloaded nmethods 682 MutexLocker cl(CompiledIC_lock); 683 cm->cleanup_inline_caches(); 684 SWEEP(cm); 685 } 686 return result; 687 } 688 689 690 void NMethodSweeper::possibly_flush(nmethod* nm) { 691 if (UseCodeCacheFlushing) { 692 if (!nm->is_locked_by_vm() && !nm->is_native_method()) { 693 bool make_not_entrant = false; 694 695 // Do not make native methods not-entrant 696 nm->dec_hotness_counter(); 697 // Get the initial value of the hotness counter. This value depends on the 698 // ReservedCodeCacheSize 699 int reset_val = hotness_counter_reset_val(); 700 int time_since_reset = reset_val - nm->hotness_counter(); 701 int code_blob_type = CodeCache::get_code_blob_type(nm); 702 double threshold = -reset_val + (CodeCache::reverse_free_ratio(code_blob_type) * NmethodSweepActivity); 703 // The less free space in the code cache we have - the bigger reverse_free_ratio() is. 704 // I.e., 'threshold' increases with lower available space in the code cache and a higher 705 // NmethodSweepActivity. If the current hotness counter - which decreases from its initial 706 // value until it is reset by stack walking - is smaller than the computed threshold, the 707 // corresponding nmethod is considered for removal. 708 if ((NmethodSweepActivity > 0) && (nm->hotness_counter() < threshold) && (time_since_reset > MinPassesBeforeFlush)) { 709 // A method is marked as not-entrant if the method is 710 // 1) 'old enough': nm->hotness_counter() < threshold 711 // 2) The method was in_use for a minimum amount of time: (time_since_reset > MinPassesBeforeFlush) 712 // The second condition is necessary if we are dealing with very small code cache 713 // sizes (e.g., <10m) and the code cache size is too small to hold all hot methods. 714 // The second condition ensures that methods are not immediately made not-entrant 715 // after compilation. 716 make_not_entrant = true; 717 } 718 719 // The stack-scanning low-cost detection may not see the method was used (which can happen for 720 // flat profiles). Check the age counter for possible data. 721 if (UseCodeAging && make_not_entrant && (nm->is_compiled_by_c2() || nm->is_compiled_by_c1())) { 722 MethodCounters* mc = nm->method()->get_method_counters(Thread::current()); 723 if (mc != NULL) { 724 // Snapshot the value as it's changed concurrently 725 int age = mc->nmethod_age(); 726 if (MethodCounters::is_nmethod_hot(age)) { 727 // The method has gone through flushing, and it became relatively hot that it deopted 728 // before we could take a look at it. Give it more time to appear in the stack traces, 729 // proportional to the number of deopts. 730 MethodData* md = nm->method()->method_data(); 731 if (md != NULL && time_since_reset > (int)(MinPassesBeforeFlush * (md->tenure_traps() + 1))) { 732 // It's been long enough, we still haven't seen it on stack. 733 // Try to flush it, but enable counters the next time. 734 mc->reset_nmethod_age(); 735 } else { 736 make_not_entrant = false; 737 } 738 } else if (MethodCounters::is_nmethod_warm(age)) { 739 // Method has counters enabled, and the method was used within 740 // previous MinPassesBeforeFlush sweeps. Reset the counter. Stay in the existing 741 // compiled state. 742 mc->reset_nmethod_age(); 743 // delay the next check 744 nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val()); 745 make_not_entrant = false; 746 } else if (MethodCounters::is_nmethod_age_unset(age)) { 747 // No counters were used before. Set the counters to the detection 748 // limit value. If the method is going to be used again it will be compiled 749 // with counters that we're going to use for analysis the the next time. 750 mc->reset_nmethod_age(); 751 } else { 752 // Method was totally idle for 10 sweeps 753 // The counter already has the initial value, flush it and may be recompile 754 // later with counters 755 } 756 } 757 } 758 759 if (make_not_entrant) { 760 nm->make_not_entrant(); 761 762 // Code cache state change is tracked in make_not_entrant() 763 if (PrintMethodFlushing && Verbose) { 764 tty->print_cr("### Nmethod %d/" PTR_FORMAT "made not-entrant: hotness counter %d/%d threshold %f", 765 nm->compile_id(), p2i(nm), nm->hotness_counter(), reset_val, threshold); 766 } 767 } 768 } 769 } 770 } 771 772 // Print out some state information about the current sweep and the 773 // state of the code cache if it's requested. 774 void NMethodSweeper::log_sweep(const char* msg, const char* format, ...) { 775 if (PrintMethodFlushing) { 776 ResourceMark rm; 777 stringStream s; 778 // Dump code cache state into a buffer before locking the tty, 779 // because log_state() will use locks causing lock conflicts. 780 CodeCache::log_state(&s); 781 782 ttyLocker ttyl; 783 tty->print("### sweeper: %s ", msg); 784 if (format != NULL) { 785 va_list ap; 786 va_start(ap, format); 787 tty->vprint(format, ap); 788 va_end(ap); 789 } 790 tty->print_cr("%s", s.as_string()); 791 } 792 793 if (LogCompilation && (xtty != NULL)) { 794 ResourceMark rm; 795 stringStream s; 796 // Dump code cache state into a buffer before locking the tty, 797 // because log_state() will use locks causing lock conflicts. 798 CodeCache::log_state(&s); 799 800 ttyLocker ttyl; 801 xtty->begin_elem("sweeper state='%s' traversals='" INTX_FORMAT "' ", msg, (intx)traversal_count()); 802 if (format != NULL) { 803 va_list ap; 804 va_start(ap, format); 805 xtty->vprint(format, ap); 806 va_end(ap); 807 } 808 xtty->print("%s", s.as_string()); 809 xtty->stamp(); 810 xtty->end_elem(); 811 } 812 } 813 814 void NMethodSweeper::print() { 815 ttyLocker ttyl; 816 tty->print_cr("Code cache sweeper statistics:"); 817 tty->print_cr(" Total sweep time: %1.0lfms", (double)_total_time_sweeping.value()/1000000); 818 tty->print_cr(" Total number of full sweeps: %ld", _total_nof_code_cache_sweeps); 819 tty->print_cr(" Total number of flushed methods: %ld(%ld C2 methods)", _total_nof_methods_reclaimed, 820 _total_nof_c2_methods_reclaimed); 821 tty->print_cr(" Total size of flushed methods: " SIZE_FORMAT "kB", _total_flushed_size/K); 822 }