1 /* 2 * Copyright (c) 1997, 2018, 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 "gc/shared/collectedHeap.hpp" 32 #include "gc/shared/workgroup.hpp" 33 #include "jfr/jfrEvents.hpp" 34 #include "logging/log.hpp" 35 #include "logging/logStream.hpp" 36 #include "memory/allocation.inline.hpp" 37 #include "memory/resourceArea.hpp" 38 #include "memory/universe.hpp" 39 #include "oops/method.hpp" 40 #include "runtime/atomic.hpp" 41 #include "runtime/compilationPolicy.hpp" 42 #include "runtime/interfaceSupport.inline.hpp" 43 #include "runtime/handshake.hpp" 44 #include "runtime/mutexLocker.hpp" 45 #include "runtime/orderAccess.hpp" 46 #include "runtime/os.hpp" 47 #include "runtime/sweeper.hpp" 48 #include "runtime/thread.inline.hpp" 49 #include "runtime/vm_operations.hpp" 50 #include "runtime/vmThread.hpp" 51 #include "utilities/events.hpp" 52 #include "utilities/xmlstream.hpp" 53 54 #ifdef ASSERT 55 56 #define SWEEP(nm) record_sweep(nm, __LINE__) 57 // Sweeper logging code 58 class SweeperRecord { 59 public: 60 int traversal; 61 int compile_id; 62 long traversal_mark; 63 int state; 64 const char* kind; 65 address vep; 66 address uep; 67 int line; 68 69 void print() { 70 tty->print_cr("traversal = %d compile_id = %d %s uep = " PTR_FORMAT " vep = " 71 PTR_FORMAT " state = %d traversal_mark %ld line = %d", 72 traversal, 73 compile_id, 74 kind == NULL ? "" : kind, 75 p2i(uep), 76 p2i(vep), 77 state, 78 traversal_mark, 79 line); 80 } 81 }; 82 83 static int _sweep_index = 0; 84 static SweeperRecord* _records = NULL; 85 86 void NMethodSweeper::report_events(int id, address entry) { 87 if (_records != NULL) { 88 for (int i = _sweep_index; i < SweeperLogEntries; i++) { 89 if (_records[i].uep == entry || 90 _records[i].vep == entry || 91 _records[i].compile_id == id) { 92 _records[i].print(); 93 } 94 } 95 for (int i = 0; i < _sweep_index; i++) { 96 if (_records[i].uep == entry || 97 _records[i].vep == entry || 98 _records[i].compile_id == id) { 99 _records[i].print(); 100 } 101 } 102 } 103 } 104 105 void NMethodSweeper::report_events() { 106 if (_records != NULL) { 107 for (int i = _sweep_index; i < SweeperLogEntries; i++) { 108 // skip empty records 109 if (_records[i].vep == NULL) continue; 110 _records[i].print(); 111 } 112 for (int i = 0; i < _sweep_index; i++) { 113 // skip empty records 114 if (_records[i].vep == NULL) continue; 115 _records[i].print(); 116 } 117 } 118 } 119 120 void NMethodSweeper::record_sweep(CompiledMethod* nm, int line) { 121 if (_records != NULL) { 122 _records[_sweep_index].traversal = _traversals; 123 _records[_sweep_index].traversal_mark = nm->is_nmethod() ? ((nmethod*)nm)->stack_traversal_mark() : 0; 124 _records[_sweep_index].compile_id = nm->compile_id(); 125 _records[_sweep_index].kind = nm->compile_kind(); 126 _records[_sweep_index].state = nm->get_state(); 127 _records[_sweep_index].vep = nm->verified_entry_point(); 128 _records[_sweep_index].uep = nm->entry_point(); 129 _records[_sweep_index].line = line; 130 _sweep_index = (_sweep_index + 1) % SweeperLogEntries; 131 } 132 } 133 134 void NMethodSweeper::init_sweeper_log() { 135 if (LogSweeper && _records == NULL) { 136 // Create the ring buffer for the logging code 137 _records = NEW_C_HEAP_ARRAY(SweeperRecord, SweeperLogEntries, mtGC); 138 memset(_records, 0, sizeof(SweeperRecord) * SweeperLogEntries); 139 } 140 } 141 #else 142 #define SWEEP(nm) 143 #endif 144 145 CompiledMethodIterator NMethodSweeper::_current(false /* only_alive */, false /* only_not_unloading */); // Current compiled method 146 long NMethodSweeper::_traversals = 0; // Stack scan count, also sweep ID. 147 long NMethodSweeper::_total_nof_code_cache_sweeps = 0; // Total number of full sweeps of the code cache 148 long NMethodSweeper::_time_counter = 0; // Virtual time used to periodically invoke sweeper 149 long NMethodSweeper::_last_sweep = 0; // Value of _time_counter when the last sweep happened 150 int NMethodSweeper::_seen = 0; // Nof. nmethod we have currently processed in current pass of CodeCache 151 152 volatile bool NMethodSweeper::_should_sweep = true; // Indicates if we should invoke the sweeper 153 volatile bool NMethodSweeper::_force_sweep = false;// Indicates if we should force a sweep 154 volatile int NMethodSweeper::_bytes_changed = 0; // Counts the total nmethod size if the nmethod changed from: 155 // 1) alive -> not_entrant 156 // 2) not_entrant -> zombie 157 int NMethodSweeper::_hotness_counter_reset_val = 0; 158 159 long NMethodSweeper::_total_nof_methods_reclaimed = 0; // Accumulated nof methods flushed 160 long NMethodSweeper::_total_nof_c2_methods_reclaimed = 0; // Accumulated nof methods flushed 161 size_t NMethodSweeper::_total_flushed_size = 0; // Total number of bytes flushed from the code cache 162 Tickspan NMethodSweeper::_total_time_sweeping; // Accumulated time sweeping 163 Tickspan NMethodSweeper::_total_time_this_sweep; // Total time this sweep 164 Tickspan NMethodSweeper::_peak_sweep_time; // Peak time for a full sweep 165 Tickspan NMethodSweeper::_peak_sweep_fraction_time; // Peak time sweeping one fraction 166 167 class MarkActivationClosure: public CodeBlobClosure { 168 public: 169 virtual void do_code_blob(CodeBlob* cb) { 170 assert(cb->is_nmethod(), "CodeBlob should be nmethod"); 171 nmethod* nm = (nmethod*)cb; 172 nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val()); 173 // If we see an activation belonging to a non_entrant nmethod, we mark it. 174 if (nm->is_not_entrant()) { 175 nm->mark_as_seen_on_stack(); 176 } 177 } 178 }; 179 static MarkActivationClosure mark_activation_closure; 180 181 class SetHotnessClosure: public CodeBlobClosure { 182 public: 183 virtual void do_code_blob(CodeBlob* cb) { 184 assert(cb->is_nmethod(), "CodeBlob should be nmethod"); 185 nmethod* nm = (nmethod*)cb; 186 nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val()); 187 } 188 }; 189 static SetHotnessClosure set_hotness_closure; 190 191 192 int NMethodSweeper::hotness_counter_reset_val() { 193 if (_hotness_counter_reset_val == 0) { 194 _hotness_counter_reset_val = (ReservedCodeCacheSize < M) ? 1 : (ReservedCodeCacheSize / M) * 2; 195 } 196 return _hotness_counter_reset_val; 197 } 198 bool NMethodSweeper::wait_for_stack_scanning() { 199 return _current.end(); 200 } 201 202 class NMethodMarkingThreadClosure : public ThreadClosure { 203 private: 204 CodeBlobClosure* _cl; 205 public: 206 NMethodMarkingThreadClosure(CodeBlobClosure* cl) : _cl(cl) {} 207 void do_thread(Thread* thread) { 208 if (thread->is_Java_thread() && ! thread->is_Code_cache_sweeper_thread()) { 209 JavaThread* jt = (JavaThread*) thread; 210 jt->nmethods_do(_cl); 211 } 212 } 213 }; 214 215 class NMethodMarkingTask : public AbstractGangTask { 216 private: 217 NMethodMarkingThreadClosure* _cl; 218 public: 219 NMethodMarkingTask(NMethodMarkingThreadClosure* cl) : 220 AbstractGangTask("Parallel NMethod Marking"), 221 _cl(cl) { 222 Threads::change_thread_claim_parity(); 223 } 224 225 ~NMethodMarkingTask() { 226 Threads::assert_all_threads_claimed(); 227 } 228 229 void work(uint worker_id) { 230 Threads::possibly_parallel_threads_do(true, _cl); 231 } 232 }; 233 234 /** 235 * Scans the stacks of all Java threads and marks activations of not-entrant methods. 236 * No need to synchronize access, since 'mark_active_nmethods' is always executed at a 237 * safepoint. 238 */ 239 void NMethodSweeper::mark_active_nmethods() { 240 CodeBlobClosure* cl = prepare_mark_active_nmethods(); 241 if (cl != NULL) { 242 WorkGang* workers = Universe::heap()->get_safepoint_workers(); 243 if (workers != NULL) { 244 NMethodMarkingThreadClosure tcl(cl); 245 NMethodMarkingTask task(&tcl); 246 workers->run_task(&task); 247 } else { 248 Threads::nmethods_do(cl); 249 } 250 } 251 } 252 253 CodeBlobClosure* NMethodSweeper::prepare_mark_active_nmethods() { 254 #ifdef ASSERT 255 if (ThreadLocalHandshakes) { 256 assert(Thread::current()->is_Code_cache_sweeper_thread(), "must be executed under CodeCache_lock and in sweeper thread"); 257 assert_lock_strong(CodeCache_lock); 258 } else { 259 assert(SafepointSynchronize::is_at_safepoint(), "must be executed at a safepoint"); 260 } 261 #endif 262 263 // If we do not want to reclaim not-entrant or zombie methods there is no need 264 // to scan stacks 265 if (!MethodFlushing) { 266 return NULL; 267 } 268 269 // Increase time so that we can estimate when to invoke the sweeper again. 270 _time_counter++; 271 272 // Check for restart 273 assert(_current.method() == NULL, "should only happen between sweeper cycles"); 274 assert(wait_for_stack_scanning(), "should only happen between sweeper cycles"); 275 276 _seen = 0; 277 _current = CompiledMethodIterator(false /* only_alive */, false /* only_not_unloading */); 278 // Initialize to first nmethod 279 _current.next(); 280 _traversals += 1; 281 _total_time_this_sweep = Tickspan(); 282 283 if (PrintMethodFlushing) { 284 tty->print_cr("### Sweep: stack traversal %ld", _traversals); 285 } 286 return &mark_activation_closure; 287 } 288 289 CodeBlobClosure* NMethodSweeper::prepare_reset_hotness_counters() { 290 assert(SafepointSynchronize::is_at_safepoint(), "must be executed at a safepoint"); 291 292 // If we do not want to reclaim not-entrant or zombie methods there is no need 293 // to scan stacks 294 if (!MethodFlushing) { 295 return NULL; 296 } 297 298 // Increase time so that we can estimate when to invoke the sweeper again. 299 _time_counter++; 300 301 // Check for restart 302 if (_current.method() != NULL) { 303 if (_current.method()->is_nmethod()) { 304 assert(CodeCache::find_blob_unsafe(_current.method()) == _current.method(), "Sweeper nmethod cached state invalid"); 305 } else if (_current.method()->is_aot()) { 306 assert(CodeCache::find_blob_unsafe(_current.method()->code_begin()) == _current.method(), "Sweeper AOT method cached state invalid"); 307 } else { 308 ShouldNotReachHere(); 309 } 310 } 311 312 return &set_hotness_closure; 313 } 314 315 /** 316 * This function triggers a VM operation that does stack scanning of active 317 * methods. Stack scanning is mandatory for the sweeper to make progress. 318 */ 319 void NMethodSweeper::do_stack_scanning() { 320 assert(!CodeCache_lock->owned_by_self(), "just checking"); 321 if (wait_for_stack_scanning()) { 322 if (ThreadLocalHandshakes) { 323 CodeBlobClosure* code_cl; 324 { 325 MutexLockerEx ccl(CodeCache_lock, Mutex::_no_safepoint_check_flag); 326 code_cl = prepare_mark_active_nmethods(); 327 } 328 if (code_cl != NULL) { 329 NMethodMarkingThreadClosure tcl(code_cl); 330 Handshake::execute(&tcl); 331 } 332 } else { 333 VM_MarkActiveNMethods op; 334 VMThread::execute(&op); 335 } 336 } 337 } 338 339 void NMethodSweeper::sweeper_loop() { 340 bool timeout; 341 while (true) { 342 { 343 ThreadBlockInVM tbivm(JavaThread::current()); 344 MutexLockerEx waiter(CodeCache_lock, Mutex::_no_safepoint_check_flag); 345 const long wait_time = 60*60*24 * 1000; 346 timeout = CodeCache_lock->wait(Mutex::_no_safepoint_check_flag, wait_time); 347 } 348 if (!timeout) { 349 possibly_sweep(); 350 } 351 } 352 } 353 354 /** 355 * Wakes up the sweeper thread to possibly sweep. 356 */ 357 void NMethodSweeper::notify(int code_blob_type) { 358 // Makes sure that we do not invoke the sweeper too often during startup. 359 double start_threshold = 100.0 / (double)StartAggressiveSweepingAt; 360 double aggressive_sweep_threshold = MIN2(start_threshold, 1.1); 361 if (CodeCache::reverse_free_ratio(code_blob_type) >= aggressive_sweep_threshold) { 362 assert_locked_or_safepoint(CodeCache_lock); 363 CodeCache_lock->notify(); 364 } 365 } 366 367 /** 368 * Wakes up the sweeper thread and forces a sweep. Blocks until it finished. 369 */ 370 void NMethodSweeper::force_sweep() { 371 ThreadBlockInVM tbivm(JavaThread::current()); 372 MutexLockerEx waiter(CodeCache_lock, Mutex::_no_safepoint_check_flag); 373 // Request forced sweep 374 _force_sweep = true; 375 while (_force_sweep) { 376 // Notify sweeper that we want to force a sweep and wait for completion. 377 // In case a sweep currently takes place we timeout and try again because 378 // we want to enforce a full sweep. 379 CodeCache_lock->notify(); 380 CodeCache_lock->wait(Mutex::_no_safepoint_check_flag, 1000); 381 } 382 } 383 384 /** 385 * Handle a safepoint request 386 */ 387 void NMethodSweeper::handle_safepoint_request() { 388 JavaThread* thread = JavaThread::current(); 389 if (SafepointMechanism::should_block(thread)) { 390 if (PrintMethodFlushing && Verbose) { 391 tty->print_cr("### Sweep at %d out of %d, yielding to safepoint", _seen, CodeCache::nmethod_count()); 392 } 393 MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag); 394 395 ThreadBlockInVM tbivm(thread); 396 thread->java_suspend_self(); 397 } 398 } 399 400 /** 401 * This function invokes the sweeper if at least one of the three conditions is met: 402 * (1) The code cache is getting full 403 * (2) There are sufficient state changes in/since the last sweep. 404 * (3) We have not been sweeping for 'some time' 405 */ 406 void NMethodSweeper::possibly_sweep() { 407 assert(JavaThread::current()->thread_state() == _thread_in_vm, "must run in vm mode"); 408 // If there was no state change while nmethod sweeping, 'should_sweep' will be false. 409 // This is one of the two places where should_sweep can be set to true. The general 410 // idea is as follows: If there is enough free space in the code cache, there is no 411 // need to invoke the sweeper. The following formula (which determines whether to invoke 412 // the sweeper or not) depends on the assumption that for larger ReservedCodeCacheSizes 413 // we need less frequent sweeps than for smaller ReservedCodecCacheSizes. Furthermore, 414 // the formula considers how much space in the code cache is currently used. Here are 415 // some examples that will (hopefully) help in understanding. 416 // 417 // Small ReservedCodeCacheSizes: (e.g., < 16M) We invoke the sweeper every time, since 418 // the result of the division is 0. This 419 // keeps the used code cache size small 420 // (important for embedded Java) 421 // Large ReservedCodeCacheSize : (e.g., 256M + code cache is 10% full). The formula 422 // computes: (256 / 16) - 1 = 15 423 // As a result, we invoke the sweeper after 424 // 15 invocations of 'mark_active_nmethods. 425 // Large ReservedCodeCacheSize: (e.g., 256M + code Cache is 90% full). The formula 426 // computes: (256 / 16) - 10 = 6. 427 if (!_should_sweep) { 428 const int time_since_last_sweep = _time_counter - _last_sweep; 429 // ReservedCodeCacheSize has an 'unsigned' type. We need a 'signed' type for max_wait_time, 430 // since 'time_since_last_sweep' can be larger than 'max_wait_time'. If that happens using 431 // an unsigned type would cause an underflow (wait_until_next_sweep becomes a large positive 432 // value) that disables the intended periodic sweeps. 433 const int max_wait_time = ReservedCodeCacheSize / (16 * M); 434 double wait_until_next_sweep = max_wait_time - time_since_last_sweep - 435 MAX2(CodeCache::reverse_free_ratio(CodeBlobType::MethodProfiled), 436 CodeCache::reverse_free_ratio(CodeBlobType::MethodNonProfiled)); 437 assert(wait_until_next_sweep <= (double)max_wait_time, "Calculation of code cache sweeper interval is incorrect"); 438 439 if ((wait_until_next_sweep <= 0.0) || !CompileBroker::should_compile_new_jobs()) { 440 _should_sweep = true; 441 } 442 } 443 444 // Remember if this was a forced sweep 445 bool forced = _force_sweep; 446 447 // Force stack scanning if there is only 10% free space in the code cache. 448 // We force stack scanning only if the non-profiled code heap gets full, since critical 449 // allocations go to the non-profiled heap and we must be make sure that there is 450 // enough space. 451 double free_percent = 1 / CodeCache::reverse_free_ratio(CodeBlobType::MethodNonProfiled) * 100; 452 if (free_percent <= StartAggressiveSweepingAt || forced || _should_sweep) { 453 do_stack_scanning(); 454 } 455 456 if (_should_sweep || forced) { 457 init_sweeper_log(); 458 sweep_code_cache(); 459 } 460 461 // We are done with sweeping the code cache once. 462 _total_nof_code_cache_sweeps++; 463 _last_sweep = _time_counter; 464 // Reset flag; temporarily disables sweeper 465 _should_sweep = false; 466 // If there was enough state change, 'possibly_enable_sweeper()' 467 // sets '_should_sweep' to true 468 possibly_enable_sweeper(); 469 // Reset _bytes_changed only if there was enough state change. _bytes_changed 470 // can further increase by calls to 'report_state_change'. 471 if (_should_sweep) { 472 _bytes_changed = 0; 473 } 474 475 if (forced) { 476 // Notify requester that forced sweep finished 477 assert(_force_sweep, "Should be a forced sweep"); 478 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag); 479 _force_sweep = false; 480 CodeCache_lock->notify(); 481 } 482 } 483 484 static void post_sweep_event(EventSweepCodeCache* event, 485 const Ticks& start, 486 const Ticks& end, 487 s4 traversals, 488 int swept, 489 int flushed, 490 int zombified) { 491 assert(event != NULL, "invariant"); 492 assert(event->should_commit(), "invariant"); 493 event->set_starttime(start); 494 event->set_endtime(end); 495 event->set_sweepId(traversals); 496 event->set_sweptCount(swept); 497 event->set_flushedCount(flushed); 498 event->set_zombifiedCount(zombified); 499 event->commit(); 500 } 501 502 void NMethodSweeper::sweep_code_cache() { 503 ResourceMark rm; 504 Ticks sweep_start_counter = Ticks::now(); 505 506 log_debug(codecache, sweep, start)("CodeCache flushing"); 507 508 int flushed_count = 0; 509 int zombified_count = 0; 510 int flushed_c2_count = 0; 511 512 if (PrintMethodFlushing && Verbose) { 513 tty->print_cr("### Sweep at %d out of %d", _seen, CodeCache::nmethod_count()); 514 } 515 516 int swept_count = 0; 517 assert(!SafepointSynchronize::is_at_safepoint(), "should not be in safepoint when we get here"); 518 assert(!CodeCache_lock->owned_by_self(), "just checking"); 519 520 int freed_memory = 0; 521 { 522 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag); 523 524 while (!_current.end()) { 525 swept_count++; 526 // Since we will give up the CodeCache_lock, always skip ahead 527 // to the next nmethod. Other blobs can be deleted by other 528 // threads but nmethods are only reclaimed by the sweeper. 529 CompiledMethod* nm = _current.method(); 530 _current.next(); 531 532 // Now ready to process nmethod and give up CodeCache_lock 533 { 534 MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag); 535 // Save information before potentially flushing the nmethod 536 // Only flushing nmethods so size only matters for them. 537 int size = nm->is_nmethod() ? ((nmethod*)nm)->total_size() : 0; 538 bool is_c2_method = nm->is_compiled_by_c2(); 539 bool is_osr = nm->is_osr_method(); 540 int compile_id = nm->compile_id(); 541 intptr_t address = p2i(nm); 542 const char* state_before = nm->state(); 543 const char* state_after = ""; 544 545 MethodStateChange type = process_compiled_method(nm); 546 switch (type) { 547 case Flushed: 548 state_after = "flushed"; 549 freed_memory += size; 550 ++flushed_count; 551 if (is_c2_method) { 552 ++flushed_c2_count; 553 } 554 break; 555 case MadeZombie: 556 state_after = "made zombie"; 557 ++zombified_count; 558 break; 559 case None: 560 break; 561 default: 562 ShouldNotReachHere(); 563 } 564 if (PrintMethodFlushing && Verbose && type != None) { 565 tty->print_cr("### %s nmethod %3d/" PTR_FORMAT " (%s) %s", is_osr ? "osr" : "", compile_id, address, state_before, state_after); 566 } 567 } 568 569 _seen++; 570 handle_safepoint_request(); 571 } 572 } 573 574 assert(_current.end(), "must have scanned the whole cache"); 575 576 const Ticks sweep_end_counter = Ticks::now(); 577 const Tickspan sweep_time = sweep_end_counter - sweep_start_counter; 578 { 579 MutexLockerEx mu(NMethodSweeperStats_lock, Mutex::_no_safepoint_check_flag); 580 _total_time_sweeping += sweep_time; 581 _total_time_this_sweep += sweep_time; 582 _peak_sweep_fraction_time = MAX2(sweep_time, _peak_sweep_fraction_time); 583 _total_flushed_size += freed_memory; 584 _total_nof_methods_reclaimed += flushed_count; 585 _total_nof_c2_methods_reclaimed += flushed_c2_count; 586 _peak_sweep_time = MAX2(_peak_sweep_time, _total_time_this_sweep); 587 } 588 589 EventSweepCodeCache event(UNTIMED); 590 if (event.should_commit()) { 591 post_sweep_event(&event, sweep_start_counter, sweep_end_counter, (s4)_traversals, swept_count, flushed_count, zombified_count); 592 } 593 594 #ifdef ASSERT 595 if(PrintMethodFlushing) { 596 tty->print_cr("### sweeper: sweep time(" JLONG_FORMAT "): ", sweep_time.value()); 597 } 598 #endif 599 600 Log(codecache, sweep) log; 601 if (log.is_debug()) { 602 LogStream ls(log.debug()); 603 CodeCache::print_summary(&ls, false); 604 } 605 log_sweep("finished"); 606 607 // Sweeper is the only case where memory is released, check here if it 608 // is time to restart the compiler. Only checking if there is a certain 609 // amount of free memory in the code cache might lead to re-enabling 610 // compilation although no memory has been released. For example, there are 611 // cases when compilation was disabled although there is 4MB (or more) free 612 // memory in the code cache. The reason is code cache fragmentation. Therefore, 613 // it only makes sense to re-enable compilation if we have actually freed memory. 614 // Note that typically several kB are released for sweeping 16MB of the code 615 // cache. As a result, 'freed_memory' > 0 to restart the compiler. 616 if (!CompileBroker::should_compile_new_jobs() && (freed_memory > 0)) { 617 CompileBroker::set_should_compile_new_jobs(CompileBroker::run_compilation); 618 log.debug("restart compiler"); 619 log_sweep("restart_compiler"); 620 } 621 } 622 623 /** 624 * This function updates the sweeper statistics that keep track of nmethods 625 * state changes. If there is 'enough' state change, the sweeper is invoked 626 * as soon as possible. There can be data races on _bytes_changed. The data 627 * races are benign, since it does not matter if we loose a couple of bytes. 628 * In the worst case we call the sweeper a little later. Also, we are guaranteed 629 * to invoke the sweeper if the code cache gets full. 630 */ 631 void NMethodSweeper::report_state_change(nmethod* nm) { 632 _bytes_changed += nm->total_size(); 633 possibly_enable_sweeper(); 634 } 635 636 /** 637 * Function determines if there was 'enough' state change in the code cache to invoke 638 * the sweeper again. Currently, we determine 'enough' as more than 1% state change in 639 * the code cache since the last sweep. 640 */ 641 void NMethodSweeper::possibly_enable_sweeper() { 642 double percent_changed = ((double)_bytes_changed / (double)ReservedCodeCacheSize) * 100; 643 if (percent_changed > 1.0) { 644 _should_sweep = true; 645 } 646 } 647 648 class CompiledMethodMarker: public StackObj { 649 private: 650 CodeCacheSweeperThread* _thread; 651 public: 652 CompiledMethodMarker(CompiledMethod* cm) { 653 JavaThread* current = JavaThread::current(); 654 assert (current->is_Code_cache_sweeper_thread(), "Must be"); 655 _thread = (CodeCacheSweeperThread*)current; 656 if (!cm->is_zombie() && !cm->is_unloading()) { 657 // Only expose live nmethods for scanning 658 _thread->set_scanned_compiled_method(cm); 659 } 660 } 661 ~CompiledMethodMarker() { 662 _thread->set_scanned_compiled_method(NULL); 663 } 664 }; 665 666 void NMethodSweeper::release_compiled_method(CompiledMethod* nm) { 667 // Make sure the released nmethod is no longer referenced by the sweeper thread 668 CodeCacheSweeperThread* thread = (CodeCacheSweeperThread*)JavaThread::current(); 669 thread->set_scanned_compiled_method(NULL); 670 671 // Clean up any CompiledICHolders 672 { 673 ResourceMark rm; 674 RelocIterator iter(nm); 675 CompiledICLocker ml(nm); 676 while (iter.next()) { 677 if (iter.type() == relocInfo::virtual_call_type) { 678 CompiledIC::cleanup_call_site(iter.virtual_call_reloc(), nm); 679 } 680 } 681 } 682 683 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag); 684 nm->flush(); 685 } 686 687 NMethodSweeper::MethodStateChange NMethodSweeper::process_compiled_method(CompiledMethod* cm) { 688 assert(cm != NULL, "sanity"); 689 assert(!CodeCache_lock->owned_by_self(), "just checking"); 690 691 MethodStateChange result = None; 692 // Make sure this nmethod doesn't get unloaded during the scan, 693 // since safepoints may happen during acquired below locks. 694 CompiledMethodMarker nmm(cm); 695 SWEEP(cm); 696 697 // Skip methods that are currently referenced by the VM 698 if (cm->is_locked_by_vm()) { 699 // But still remember to clean-up inline caches for alive nmethods 700 if (cm->is_alive() && !cm->is_unloading()) { 701 // Clean inline caches that point to zombie/non-entrant/unloaded nmethods 702 CompiledICLocker ml(cm); 703 cm->cleanup_inline_caches(false); 704 SWEEP(cm); 705 } 706 return result; 707 } 708 709 if (cm->is_zombie()) { 710 // All inline caches that referred to this nmethod were cleaned in the 711 // previous sweeper cycle. Now flush the nmethod from the code cache. 712 assert(!cm->is_locked_by_vm(), "must not flush locked Compiled Methods"); 713 release_compiled_method(cm); 714 assert(result == None, "sanity"); 715 result = Flushed; 716 } else if (cm->is_not_entrant()) { 717 // If there are no current activations of this method on the 718 // stack we can safely convert it to a zombie method 719 OrderAccess::loadload(); // _stack_traversal_mark and _state 720 if (cm->can_convert_to_zombie()) { 721 // Clear ICStubs to prevent back patching stubs of zombie or flushed 722 // nmethods during the next safepoint (see ICStub::finalize). 723 { 724 CompiledICLocker ml(cm); 725 cm->clear_ic_stubs(); 726 } 727 // Code cache state change is tracked in make_zombie() 728 cm->make_zombie(); 729 SWEEP(cm); 730 // The nmethod may have been locked by JVMTI after being made zombie (see 731 // JvmtiDeferredEvent::compiled_method_unload_event()). If so, we cannot 732 // flush the osr nmethod directly but have to wait for a later sweeper cycle. 733 if (cm->is_osr_method() && !cm->is_locked_by_vm()) { 734 // No inline caches will ever point to osr methods, so we can just remove it. 735 // Make sure that we unregistered the nmethod with the heap and flushed all 736 // dependencies before removing the nmethod (done in make_zombie()). 737 assert(cm->is_zombie(), "nmethod must be unregistered"); 738 release_compiled_method(cm); 739 assert(result == None, "sanity"); 740 result = Flushed; 741 } else { 742 assert(result == None, "sanity"); 743 result = MadeZombie; 744 assert(cm->is_zombie(), "nmethod must be zombie"); 745 } 746 } else { 747 // Still alive, clean up its inline caches 748 CompiledICLocker ml(cm); 749 cm->cleanup_inline_caches(false); 750 SWEEP(cm); 751 } 752 } else if (cm->is_unloaded()) { 753 // Code is unloaded, so there are no activations on the stack. 754 // Convert the nmethod to zombie or flush it directly in the OSR case. 755 { 756 // Clean ICs of unloaded nmethods as well because they may reference other 757 // unloaded nmethods that may be flushed earlier in the sweeper cycle. 758 CompiledICLocker ml(cm); 759 cm->cleanup_inline_caches(false); 760 } 761 if (cm->is_osr_method()) { 762 SWEEP(cm); 763 // No inline caches will ever point to osr methods, so we can just remove it 764 release_compiled_method(cm); 765 assert(result == None, "sanity"); 766 result = Flushed; 767 } else { 768 // Code cache state change is tracked in make_zombie() 769 cm->make_zombie(); 770 SWEEP(cm); 771 assert(result == None, "sanity"); 772 result = MadeZombie; 773 } 774 } else { 775 if (cm->is_nmethod()) { 776 possibly_flush((nmethod*)cm); 777 } 778 // Clean inline caches that point to zombie/non-entrant/unloaded nmethods 779 CompiledICLocker ml(cm); 780 cm->cleanup_inline_caches(false); 781 SWEEP(cm); 782 } 783 return result; 784 } 785 786 787 void NMethodSweeper::possibly_flush(nmethod* nm) { 788 if (UseCodeCacheFlushing) { 789 if (!nm->is_locked_by_vm() && !nm->is_native_method() && !nm->is_not_installed() && !nm->is_unloading()) { 790 bool make_not_entrant = false; 791 792 // Do not make native methods not-entrant 793 nm->dec_hotness_counter(); 794 // Get the initial value of the hotness counter. This value depends on the 795 // ReservedCodeCacheSize 796 int reset_val = hotness_counter_reset_val(); 797 int time_since_reset = reset_val - nm->hotness_counter(); 798 int code_blob_type = CodeCache::get_code_blob_type(nm); 799 double threshold = -reset_val + (CodeCache::reverse_free_ratio(code_blob_type) * NmethodSweepActivity); 800 // The less free space in the code cache we have - the bigger reverse_free_ratio() is. 801 // I.e., 'threshold' increases with lower available space in the code cache and a higher 802 // NmethodSweepActivity. If the current hotness counter - which decreases from its initial 803 // value until it is reset by stack walking - is smaller than the computed threshold, the 804 // corresponding nmethod is considered for removal. 805 if ((NmethodSweepActivity > 0) && (nm->hotness_counter() < threshold) && (time_since_reset > MinPassesBeforeFlush)) { 806 // A method is marked as not-entrant if the method is 807 // 1) 'old enough': nm->hotness_counter() < threshold 808 // 2) The method was in_use for a minimum amount of time: (time_since_reset > MinPassesBeforeFlush) 809 // The second condition is necessary if we are dealing with very small code cache 810 // sizes (e.g., <10m) and the code cache size is too small to hold all hot methods. 811 // The second condition ensures that methods are not immediately made not-entrant 812 // after compilation. 813 make_not_entrant = true; 814 } 815 816 // The stack-scanning low-cost detection may not see the method was used (which can happen for 817 // flat profiles). Check the age counter for possible data. 818 if (UseCodeAging && make_not_entrant && (nm->is_compiled_by_c2() || nm->is_compiled_by_c1())) { 819 MethodCounters* mc = nm->method()->get_method_counters(Thread::current()); 820 if (mc != NULL) { 821 // Snapshot the value as it's changed concurrently 822 int age = mc->nmethod_age(); 823 if (MethodCounters::is_nmethod_hot(age)) { 824 // The method has gone through flushing, and it became relatively hot that it deopted 825 // before we could take a look at it. Give it more time to appear in the stack traces, 826 // proportional to the number of deopts. 827 MethodData* md = nm->method()->method_data(); 828 if (md != NULL && time_since_reset > (int)(MinPassesBeforeFlush * (md->tenure_traps() + 1))) { 829 // It's been long enough, we still haven't seen it on stack. 830 // Try to flush it, but enable counters the next time. 831 mc->reset_nmethod_age(); 832 } else { 833 make_not_entrant = false; 834 } 835 } else if (MethodCounters::is_nmethod_warm(age)) { 836 // Method has counters enabled, and the method was used within 837 // previous MinPassesBeforeFlush sweeps. Reset the counter. Stay in the existing 838 // compiled state. 839 mc->reset_nmethod_age(); 840 // delay the next check 841 nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val()); 842 make_not_entrant = false; 843 } else if (MethodCounters::is_nmethod_age_unset(age)) { 844 // No counters were used before. Set the counters to the detection 845 // limit value. If the method is going to be used again it will be compiled 846 // with counters that we're going to use for analysis the the next time. 847 mc->reset_nmethod_age(); 848 } else { 849 // Method was totally idle for 10 sweeps 850 // The counter already has the initial value, flush it and may be recompile 851 // later with counters 852 } 853 } 854 } 855 856 if (make_not_entrant) { 857 nm->make_not_entrant(); 858 859 // Code cache state change is tracked in make_not_entrant() 860 if (PrintMethodFlushing && Verbose) { 861 tty->print_cr("### Nmethod %d/" PTR_FORMAT "made not-entrant: hotness counter %d/%d threshold %f", 862 nm->compile_id(), p2i(nm), nm->hotness_counter(), reset_val, threshold); 863 } 864 } 865 } 866 } 867 } 868 869 // Print out some state information about the current sweep and the 870 // state of the code cache if it's requested. 871 void NMethodSweeper::log_sweep(const char* msg, const char* format, ...) { 872 if (PrintMethodFlushing) { 873 ResourceMark rm; 874 stringStream s; 875 // Dump code cache state into a buffer before locking the tty, 876 // because log_state() will use locks causing lock conflicts. 877 CodeCache::log_state(&s); 878 879 ttyLocker ttyl; 880 tty->print("### sweeper: %s ", msg); 881 if (format != NULL) { 882 va_list ap; 883 va_start(ap, format); 884 tty->vprint(format, ap); 885 va_end(ap); 886 } 887 tty->print_cr("%s", s.as_string()); 888 } 889 890 if (LogCompilation && (xtty != NULL)) { 891 ResourceMark rm; 892 stringStream s; 893 // Dump code cache state into a buffer before locking the tty, 894 // because log_state() will use locks causing lock conflicts. 895 CodeCache::log_state(&s); 896 897 ttyLocker ttyl; 898 xtty->begin_elem("sweeper state='%s' traversals='" INTX_FORMAT "' ", msg, (intx)traversal_count()); 899 if (format != NULL) { 900 va_list ap; 901 va_start(ap, format); 902 xtty->vprint(format, ap); 903 va_end(ap); 904 } 905 xtty->print("%s", s.as_string()); 906 xtty->stamp(); 907 xtty->end_elem(); 908 } 909 } 910 911 void NMethodSweeper::print(outputStream* out) { 912 ttyLocker ttyl; 913 out = (out == NULL) ? tty : out; 914 out->print_cr("Code cache sweeper statistics:"); 915 out->print_cr(" Total sweep time: %1.0lf ms", (double)_total_time_sweeping.value()/1000000); 916 out->print_cr(" Total number of full sweeps: %ld", _total_nof_code_cache_sweeps); 917 out->print_cr(" Total number of flushed methods: %ld (thereof %ld C2 methods)", _total_nof_methods_reclaimed, 918 _total_nof_c2_methods_reclaimed); 919 out->print_cr(" Total size of flushed methods: " SIZE_FORMAT " kB", _total_flushed_size/K); 920 }