sweeper.cpp revision 6402:2377269bd73d
1/* 2 * Copyright (c) 1997, 2013, 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 50class SweeperRecord { 51 public: 52 int traversal; 53 int invocation; 54 int compile_id; 55 long traversal_mark; 56 int state; 57 const char* kind; 58 address vep; 59 address uep; 60 int line; 61 62 void print() { 63 tty->print_cr("traversal = %d invocation = %d compile_id = %d %s uep = " PTR_FORMAT " vep = " 64 PTR_FORMAT " state = %d traversal_mark %d line = %d", 65 traversal, 66 invocation, 67 compile_id, 68 kind == NULL ? "" : kind, 69 uep, 70 vep, 71 state, 72 traversal_mark, 73 line); 74 } 75}; 76 77static int _sweep_index = 0; 78static SweeperRecord* _records = NULL; 79 80void 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 99void 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 114void 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].invocation = _sweep_fractions_left; 119 _records[_sweep_index].compile_id = nm->compile_id(); 120 _records[_sweep_index].kind = nm->compile_kind(); 121 _records[_sweep_index].state = nm->_state; 122 _records[_sweep_index].vep = nm->verified_entry_point(); 123 _records[_sweep_index].uep = nm->entry_point(); 124 _records[_sweep_index].line = line; 125 _sweep_index = (_sweep_index + 1) % SweeperLogEntries; 126 } 127} 128#else 129#define SWEEP(nm) 130#endif 131 132nmethod* NMethodSweeper::_current = NULL; // Current nmethod 133long NMethodSweeper::_traversals = 0; // Stack scan count, also sweep ID. 134long NMethodSweeper::_total_nof_code_cache_sweeps = 0; // Total number of full sweeps of the code cache 135long NMethodSweeper::_time_counter = 0; // Virtual time used to periodically invoke sweeper 136long NMethodSweeper::_last_sweep = 0; // Value of _time_counter when the last sweep happened 137int NMethodSweeper::_seen = 0; // Nof. nmethod we have currently processed in current pass of CodeCache 138int NMethodSweeper::_flushed_count = 0; // Nof. nmethods flushed in current sweep 139int NMethodSweeper::_zombified_count = 0; // Nof. nmethods made zombie in current sweep 140int NMethodSweeper::_marked_for_reclamation_count = 0; // Nof. nmethods marked for reclaim in current sweep 141 142volatile bool NMethodSweeper::_should_sweep = true; // Indicates if we should invoke the sweeper 143volatile int NMethodSweeper::_sweep_fractions_left = 0; // Nof. invocations left until we are completed with this pass 144volatile int NMethodSweeper::_sweep_started = 0; // Flag to control conc sweeper 145volatile int NMethodSweeper::_bytes_changed = 0; // Counts the total nmethod size if the nmethod changed from: 146 // 1) alive -> not_entrant 147 // 2) not_entrant -> zombie 148 // 3) zombie -> marked_for_reclamation 149int NMethodSweeper::_hotness_counter_reset_val = 0; 150 151long NMethodSweeper::_total_nof_methods_reclaimed = 0; // Accumulated nof methods flushed 152long NMethodSweeper::_total_nof_c2_methods_reclaimed = 0; // Accumulated nof methods flushed 153size_t NMethodSweeper::_total_flushed_size = 0; // Total number of bytes flushed from the code cache 154Tickspan NMethodSweeper::_total_time_sweeping; // Accumulated time sweeping 155Tickspan NMethodSweeper::_total_time_this_sweep; // Total time this sweep 156Tickspan NMethodSweeper::_peak_sweep_time; // Peak time for a full sweep 157Tickspan NMethodSweeper::_peak_sweep_fraction_time; // Peak time sweeping one fraction 158 159 160 161class MarkActivationClosure: public CodeBlobClosure { 162public: 163 virtual void do_code_blob(CodeBlob* cb) { 164 if (cb->is_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}; 174static MarkActivationClosure mark_activation_closure; 175 176class SetHotnessClosure: public CodeBlobClosure { 177public: 178 virtual void do_code_blob(CodeBlob* cb) { 179 if (cb->is_nmethod()) { 180 nmethod* nm = (nmethod*)cb; 181 nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val()); 182 } 183 } 184}; 185static SetHotnessClosure set_hotness_closure; 186 187 188int NMethodSweeper::hotness_counter_reset_val() { 189 if (_hotness_counter_reset_val == 0) { 190 _hotness_counter_reset_val = (ReservedCodeCacheSize < M) ? 1 : (ReservedCodeCacheSize / M) * 2; 191 } 192 return _hotness_counter_reset_val; 193} 194bool NMethodSweeper::sweep_in_progress() { 195 return (_current != NULL); 196} 197 198// Scans the stacks of all Java threads and marks activations of not-entrant methods. 199// No need to synchronize access, since 'mark_active_nmethods' is always executed at a 200// safepoint. 201void 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 assert(CodeCache::find_blob_unsafe(_current) == _current, "Sweeper nmethod cached state invalid"); 214 if (!sweep_in_progress()) { 215 _seen = 0; 216 _sweep_fractions_left = NmethodSweepFraction; 217 _current = CodeCache::first_nmethod(); 218 _traversals += 1; 219 _total_time_this_sweep = Tickspan(); 220 221 if (PrintMethodFlushing) { 222 tty->print_cr("### Sweep: stack traversal %d", _traversals); 223 } 224 Threads::nmethods_do(&mark_activation_closure); 225 226 } else { 227 // Only set hotness counter 228 Threads::nmethods_do(&set_hotness_closure); 229 } 230 231 OrderAccess::storestore(); 232} 233/** 234 * This function invokes the sweeper if at least one of the three conditions is met: 235 * (1) The code cache is getting full 236 * (2) There are sufficient state changes in/since the last sweep. 237 * (3) We have not been sweeping for 'some time' 238 */ 239void NMethodSweeper::possibly_sweep() { 240 assert(JavaThread::current()->thread_state() == _thread_in_vm, "must run in vm mode"); 241 // Only compiler threads are allowed to sweep 242 if (!MethodFlushing || !sweep_in_progress() || !Thread::current()->is_Compiler_thread()) { 243 return; 244 } 245 246 // If there was no state change while nmethod sweeping, 'should_sweep' will be false. 247 // This is one of the two places where should_sweep can be set to true. The general 248 // idea is as follows: If there is enough free space in the code cache, there is no 249 // need to invoke the sweeper. The following formula (which determines whether to invoke 250 // the sweeper or not) depends on the assumption that for larger ReservedCodeCacheSizes 251 // we need less frequent sweeps than for smaller ReservedCodecCacheSizes. Furthermore, 252 // the formula considers how much space in the code cache is currently used. Here are 253 // some examples that will (hopefully) help in understanding. 254 // 255 // Small ReservedCodeCacheSizes: (e.g., < 16M) We invoke the sweeper every time, since 256 // the result of the division is 0. This 257 // keeps the used code cache size small 258 // (important for embedded Java) 259 // Large ReservedCodeCacheSize : (e.g., 256M + code cache is 10% full). The formula 260 // computes: (256 / 16) - 1 = 15 261 // As a result, we invoke the sweeper after 262 // 15 invocations of 'mark_active_nmethods. 263 // Large ReservedCodeCacheSize: (e.g., 256M + code Cache is 90% full). The formula 264 // computes: (256 / 16) - 10 = 6. 265 if (!_should_sweep) { 266 const int time_since_last_sweep = _time_counter - _last_sweep; 267 // ReservedCodeCacheSize has an 'unsigned' type. We need a 'signed' type for max_wait_time, 268 // since 'time_since_last_sweep' can be larger than 'max_wait_time'. If that happens using 269 // an unsigned type would cause an underflow (wait_until_next_sweep becomes a large positive 270 // value) that disables the intended periodic sweeps. 271 const int max_wait_time = ReservedCodeCacheSize / (16 * M); 272 double wait_until_next_sweep = max_wait_time - time_since_last_sweep - CodeCache::reverse_free_ratio(); 273 assert(wait_until_next_sweep <= (double)max_wait_time, "Calculation of code cache sweeper interval is incorrect"); 274 275 if ((wait_until_next_sweep <= 0.0) || !CompileBroker::should_compile_new_jobs()) { 276 _should_sweep = true; 277 } 278 } 279 280 if (_should_sweep && _sweep_fractions_left > 0) { 281 // Only one thread at a time will sweep 282 jint old = Atomic::cmpxchg( 1, &_sweep_started, 0 ); 283 if (old != 0) { 284 return; 285 } 286#ifdef ASSERT 287 if (LogSweeper && _records == NULL) { 288 // Create the ring buffer for the logging code 289 _records = NEW_C_HEAP_ARRAY(SweeperRecord, SweeperLogEntries, mtGC); 290 memset(_records, 0, sizeof(SweeperRecord) * SweeperLogEntries); 291 } 292#endif 293 294 if (_sweep_fractions_left > 0) { 295 sweep_code_cache(); 296 _sweep_fractions_left--; 297 } 298 299 // We are done with sweeping the code cache once. 300 if (_sweep_fractions_left == 0) { 301 _total_nof_code_cache_sweeps++; 302 _last_sweep = _time_counter; 303 // Reset flag; temporarily disables sweeper 304 _should_sweep = false; 305 // If there was enough state change, 'possibly_enable_sweeper()' 306 // sets '_should_sweep' to true 307 possibly_enable_sweeper(); 308 // Reset _bytes_changed only if there was enough state change. _bytes_changed 309 // can further increase by calls to 'report_state_change'. 310 if (_should_sweep) { 311 _bytes_changed = 0; 312 } 313 } 314 // Release work, because another compiler thread could continue. 315 OrderAccess::release_store((int*)&_sweep_started, 0); 316 } 317} 318 319void NMethodSweeper::sweep_code_cache() { 320 Ticks sweep_start_counter = Ticks::now(); 321 322 _flushed_count = 0; 323 _zombified_count = 0; 324 _marked_for_reclamation_count = 0; 325 326 if (PrintMethodFlushing && Verbose) { 327 tty->print_cr("### Sweep at %d out of %d. Invocations left: %d", _seen, CodeCache::nof_nmethods(), _sweep_fractions_left); 328 } 329 330 if (!CompileBroker::should_compile_new_jobs()) { 331 // If we have turned off compilations we might as well do full sweeps 332 // in order to reach the clean state faster. Otherwise the sleeping compiler 333 // threads will slow down sweeping. 334 _sweep_fractions_left = 1; 335 } 336 337 // We want to visit all nmethods after NmethodSweepFraction 338 // invocations so divide the remaining number of nmethods by the 339 // remaining number of invocations. This is only an estimate since 340 // the number of nmethods changes during the sweep so the final 341 // stage must iterate until it there are no more nmethods. 342 int todo = (CodeCache::nof_nmethods() - _seen) / _sweep_fractions_left; 343 int swept_count = 0; 344 345 346 assert(!SafepointSynchronize::is_at_safepoint(), "should not be in safepoint when we get here"); 347 assert(!CodeCache_lock->owned_by_self(), "just checking"); 348 349 int freed_memory = 0; 350 { 351 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag); 352 353 // The last invocation iterates until there are no more nmethods 354 for (int i = 0; (i < todo || _sweep_fractions_left == 1) && _current != NULL; i++) { 355 swept_count++; 356 if (SafepointSynchronize::is_synchronizing()) { // Safepoint request 357 if (PrintMethodFlushing && Verbose) { 358 tty->print_cr("### Sweep at %d out of %d, invocation: %d, yielding to safepoint", _seen, CodeCache::nof_nmethods(), _sweep_fractions_left); 359 } 360 MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag); 361 362 assert(Thread::current()->is_Java_thread(), "should be java thread"); 363 JavaThread* thread = (JavaThread*)Thread::current(); 364 ThreadBlockInVM tbivm(thread); 365 thread->java_suspend_self(); 366 } 367 // Since we will give up the CodeCache_lock, always skip ahead 368 // to the next nmethod. Other blobs can be deleted by other 369 // threads but nmethods are only reclaimed by the sweeper. 370 nmethod* next = CodeCache::next_nmethod(_current); 371 372 // Now ready to process nmethod and give up CodeCache_lock 373 { 374 MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag); 375 freed_memory += process_nmethod(_current); 376 } 377 _seen++; 378 _current = next; 379 } 380 } 381 382 assert(_sweep_fractions_left > 1 || _current == NULL, "must have scanned the whole cache"); 383 384 const Ticks sweep_end_counter = Ticks::now(); 385 const Tickspan sweep_time = sweep_end_counter - sweep_start_counter; 386 _total_time_sweeping += sweep_time; 387 _total_time_this_sweep += sweep_time; 388 _peak_sweep_fraction_time = MAX2(sweep_time, _peak_sweep_fraction_time); 389 _total_flushed_size += freed_memory; 390 _total_nof_methods_reclaimed += _flushed_count; 391 392 EventSweepCodeCache event(UNTIMED); 393 if (event.should_commit()) { 394 event.set_starttime(sweep_start_counter); 395 event.set_endtime(sweep_end_counter); 396 event.set_sweepIndex(_traversals); 397 event.set_sweepFractionIndex(NmethodSweepFraction - _sweep_fractions_left + 1); 398 event.set_sweptCount(swept_count); 399 event.set_flushedCount(_flushed_count); 400 event.set_markedCount(_marked_for_reclamation_count); 401 event.set_zombifiedCount(_zombified_count); 402 event.commit(); 403 } 404 405#ifdef ASSERT 406 if(PrintMethodFlushing) { 407 tty->print_cr("### sweeper: sweep time(%d): " 408 INT64_FORMAT, _sweep_fractions_left, (jlong)sweep_time.value()); 409 } 410#endif 411 412 if (_sweep_fractions_left == 1) { 413 _peak_sweep_time = MAX2(_peak_sweep_time, _total_time_this_sweep); 414 log_sweep("finished"); 415 } 416 417 // Sweeper is the only case where memory is released, check here if it 418 // is time to restart the compiler. Only checking if there is a certain 419 // amount of free memory in the code cache might lead to re-enabling 420 // compilation although no memory has been released. For example, there are 421 // cases when compilation was disabled although there is 4MB (or more) free 422 // memory in the code cache. The reason is code cache fragmentation. Therefore, 423 // it only makes sense to re-enable compilation if we have actually freed memory. 424 // Note that typically several kB are released for sweeping 16MB of the code 425 // cache. As a result, 'freed_memory' > 0 to restart the compiler. 426 if (!CompileBroker::should_compile_new_jobs() && (freed_memory > 0)) { 427 CompileBroker::set_should_compile_new_jobs(CompileBroker::run_compilation); 428 log_sweep("restart_compiler"); 429 } 430} 431 432/** 433 * This function updates the sweeper statistics that keep track of nmethods 434 * state changes. If there is 'enough' state change, the sweeper is invoked 435 * as soon as possible. There can be data races on _bytes_changed. The data 436 * races are benign, since it does not matter if we loose a couple of bytes. 437 * In the worst case we call the sweeper a little later. Also, we are guaranteed 438 * to invoke the sweeper if the code cache gets full. 439 */ 440void NMethodSweeper::report_state_change(nmethod* nm) { 441 _bytes_changed += nm->total_size(); 442 possibly_enable_sweeper(); 443} 444 445/** 446 * Function determines if there was 'enough' state change in the code cache to invoke 447 * the sweeper again. Currently, we determine 'enough' as more than 1% state change in 448 * the code cache since the last sweep. 449 */ 450void NMethodSweeper::possibly_enable_sweeper() { 451 double percent_changed = ((double)_bytes_changed / (double)ReservedCodeCacheSize) * 100; 452 if (percent_changed > 1.0) { 453 _should_sweep = true; 454 } 455} 456 457class NMethodMarker: public StackObj { 458 private: 459 CompilerThread* _thread; 460 public: 461 NMethodMarker(nmethod* nm) { 462 _thread = CompilerThread::current(); 463 if (!nm->is_zombie() && !nm->is_unloaded()) { 464 // Only expose live nmethods for scanning 465 _thread->set_scanned_nmethod(nm); 466 } 467 } 468 ~NMethodMarker() { 469 _thread->set_scanned_nmethod(NULL); 470 } 471}; 472 473void NMethodSweeper::release_nmethod(nmethod *nm) { 474 // Clean up any CompiledICHolders 475 { 476 ResourceMark rm; 477 MutexLocker ml_patch(CompiledIC_lock); 478 RelocIterator iter(nm); 479 while (iter.next()) { 480 if (iter.type() == relocInfo::virtual_call_type) { 481 CompiledIC::cleanup_call_site(iter.virtual_call_reloc()); 482 } 483 } 484 } 485 486 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag); 487 nm->flush(); 488} 489 490int NMethodSweeper::process_nmethod(nmethod *nm) { 491 assert(!CodeCache_lock->owned_by_self(), "just checking"); 492 493 int freed_memory = 0; 494 // Make sure this nmethod doesn't get unloaded during the scan, 495 // since safepoints may happen during acquired below locks. 496 NMethodMarker nmm(nm); 497 SWEEP(nm); 498 499 // Skip methods that are currently referenced by the VM 500 if (nm->is_locked_by_vm()) { 501 // But still remember to clean-up inline caches for alive nmethods 502 if (nm->is_alive()) { 503 // Clean inline caches that point to zombie/non-entrant methods 504 MutexLocker cl(CompiledIC_lock); 505 nm->cleanup_inline_caches(); 506 SWEEP(nm); 507 } 508 return freed_memory; 509 } 510 511 if (nm->is_zombie()) { 512 // If it is the first time we see nmethod then we mark it. Otherwise, 513 // we reclaim it. When we have seen a zombie method twice, we know that 514 // there are no inline caches that refer to it. 515 if (nm->is_marked_for_reclamation()) { 516 assert(!nm->is_locked_by_vm(), "must not flush locked nmethods"); 517 if (PrintMethodFlushing && Verbose) { 518 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (marked for reclamation) being flushed", nm->compile_id(), nm); 519 } 520 freed_memory = nm->total_size(); 521 if (nm->is_compiled_by_c2()) { 522 _total_nof_c2_methods_reclaimed++; 523 } 524 release_nmethod(nm); 525 _flushed_count++; 526 } else { 527 if (PrintMethodFlushing && Verbose) { 528 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (zombie) being marked for reclamation", nm->compile_id(), nm); 529 } 530 nm->mark_for_reclamation(); 531 // Keep track of code cache state change 532 _bytes_changed += nm->total_size(); 533 _marked_for_reclamation_count++; 534 SWEEP(nm); 535 } 536 } else if (nm->is_not_entrant()) { 537 // If there are no current activations of this method on the 538 // stack we can safely convert it to a zombie method 539 if (nm->can_not_entrant_be_converted()) { 540 if (PrintMethodFlushing && Verbose) { 541 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (not entrant) being made zombie", nm->compile_id(), nm); 542 } 543 // Code cache state change is tracked in make_zombie() 544 nm->make_zombie(); 545 _zombified_count++; 546 SWEEP(nm); 547 } else { 548 // Still alive, clean up its inline caches 549 MutexLocker cl(CompiledIC_lock); 550 nm->cleanup_inline_caches(); 551 SWEEP(nm); 552 } 553 } else if (nm->is_unloaded()) { 554 // Unloaded code, just make it a zombie 555 if (PrintMethodFlushing && Verbose) { 556 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (unloaded) being made zombie", nm->compile_id(), nm); 557 } 558 if (nm->is_osr_method()) { 559 SWEEP(nm); 560 // No inline caches will ever point to osr methods, so we can just remove it 561 freed_memory = nm->total_size(); 562 if (nm->is_compiled_by_c2()) { 563 _total_nof_c2_methods_reclaimed++; 564 } 565 release_nmethod(nm); 566 _flushed_count++; 567 } else { 568 // Code cache state change is tracked in make_zombie() 569 nm->make_zombie(); 570 _zombified_count++; 571 SWEEP(nm); 572 } 573 } else { 574 if (UseCodeCacheFlushing) { 575 if (!nm->is_locked_by_vm() && !nm->is_osr_method() && !nm->is_native_method()) { 576 // Do not make native methods and OSR-methods not-entrant 577 nm->dec_hotness_counter(); 578 // Get the initial value of the hotness counter. This value depends on the 579 // ReservedCodeCacheSize 580 int reset_val = hotness_counter_reset_val(); 581 int time_since_reset = reset_val - nm->hotness_counter(); 582 double threshold = -reset_val + (CodeCache::reverse_free_ratio() * NmethodSweepActivity); 583 // The less free space in the code cache we have - the bigger reverse_free_ratio() is. 584 // I.e., 'threshold' increases with lower available space in the code cache and a higher 585 // NmethodSweepActivity. If the current hotness counter - which decreases from its initial 586 // value until it is reset by stack walking - is smaller than the computed threshold, the 587 // corresponding nmethod is considered for removal. 588 if ((NmethodSweepActivity > 0) && (nm->hotness_counter() < threshold) && (time_since_reset > 10)) { 589 // A method is marked as not-entrant if the method is 590 // 1) 'old enough': nm->hotness_counter() < threshold 591 // 2) The method was in_use for a minimum amount of time: (time_since_reset > 10) 592 // The second condition is necessary if we are dealing with very small code cache 593 // sizes (e.g., <10m) and the code cache size is too small to hold all hot methods. 594 // The second condition ensures that methods are not immediately made not-entrant 595 // after compilation. 596 nm->make_not_entrant(); 597 // Code cache state change is tracked in make_not_entrant() 598 if (PrintMethodFlushing && Verbose) { 599 tty->print_cr("### Nmethod %d/" PTR_FORMAT "made not-entrant: hotness counter %d/%d threshold %f", 600 nm->compile_id(), nm, nm->hotness_counter(), reset_val, threshold); 601 } 602 } 603 } 604 } 605 // Clean-up all inline caches that point to zombie/non-reentrant methods 606 MutexLocker cl(CompiledIC_lock); 607 nm->cleanup_inline_caches(); 608 SWEEP(nm); 609 } 610 return freed_memory; 611} 612 613// Print out some state information about the current sweep and the 614// state of the code cache if it's requested. 615void NMethodSweeper::log_sweep(const char* msg, const char* format, ...) { 616 if (PrintMethodFlushing) { 617 stringStream s; 618 // Dump code cache state into a buffer before locking the tty, 619 // because log_state() will use locks causing lock conflicts. 620 CodeCache::log_state(&s); 621 622 ttyLocker ttyl; 623 tty->print("### sweeper: %s ", msg); 624 if (format != NULL) { 625 va_list ap; 626 va_start(ap, format); 627 tty->vprint(format, ap); 628 va_end(ap); 629 } 630 tty->print_cr(s.as_string()); 631 } 632 633 if (LogCompilation && (xtty != NULL)) { 634 stringStream s; 635 // Dump code cache state into a buffer before locking the tty, 636 // because log_state() will use locks causing lock conflicts. 637 CodeCache::log_state(&s); 638 639 ttyLocker ttyl; 640 xtty->begin_elem("sweeper state='%s' traversals='" INTX_FORMAT "' ", msg, (intx)traversal_count()); 641 if (format != NULL) { 642 va_list ap; 643 va_start(ap, format); 644 xtty->vprint(format, ap); 645 va_end(ap); 646 } 647 xtty->print(s.as_string()); 648 xtty->stamp(); 649 xtty->end_elem(); 650 } 651} 652 653void NMethodSweeper::print() { 654 ttyLocker ttyl; 655 tty->print_cr("Code cache sweeper statistics:"); 656 tty->print_cr(" Total sweep time: %1.0lfms", (double)_total_time_sweeping.value()/1000000); 657 tty->print_cr(" Total number of full sweeps: %ld", _total_nof_code_cache_sweeps); 658 tty->print_cr(" Total number of flushed methods: %ld(%ld C2 methods)", _total_nof_methods_reclaimed, 659 _total_nof_c2_methods_reclaimed); 660 tty->print_cr(" Total size of flushed methods: " SIZE_FORMAT "kB", _total_flushed_size/K); 661} 662