src/share/vm/runtime/sweeper.cpp

Mon, 02 Dec 2013 10:26:14 +0100

author
goetz
date
Mon, 02 Dec 2013 10:26:14 +0100
changeset 6493
3205e78d8193
parent 6131
86e6d691f2e1
child 6503
a9becfeecd1b
permissions
-rw-r--r--

8029396: PPC64 (part 212): Several memory ordering fixes in C-code.
Summary: memory ordering fixes in GC and other runtime code showing on PPC64.
Reviewed-by: kvn, coleenp

duke@435 1 /*
sla@5237 2 * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.
duke@435 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
duke@435 4 *
duke@435 5 * This code is free software; you can redistribute it and/or modify it
duke@435 6 * under the terms of the GNU General Public License version 2 only, as
duke@435 7 * published by the Free Software Foundation.
duke@435 8 *
duke@435 9 * This code is distributed in the hope that it will be useful, but WITHOUT
duke@435 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
duke@435 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
duke@435 12 * version 2 for more details (a copy is included in the LICENSE file that
duke@435 13 * accompanied this code).
duke@435 14 *
duke@435 15 * You should have received a copy of the GNU General Public License version
duke@435 16 * 2 along with this work; if not, write to the Free Software Foundation,
duke@435 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
duke@435 18 *
trims@1907 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
trims@1907 20 * or visit www.oracle.com if you need additional information or have any
trims@1907 21 * questions.
duke@435 22 *
duke@435 23 */
duke@435 24
stefank@2314 25 #include "precompiled.hpp"
stefank@2314 26 #include "code/codeCache.hpp"
coleenp@4037 27 #include "code/compiledIC.hpp"
coleenp@4037 28 #include "code/icBuffer.hpp"
stefank@2314 29 #include "code/nmethod.hpp"
stefank@2314 30 #include "compiler/compileBroker.hpp"
stefank@2314 31 #include "memory/resourceArea.hpp"
coleenp@4037 32 #include "oops/method.hpp"
stefank@2314 33 #include "runtime/atomic.hpp"
stefank@2314 34 #include "runtime/compilationPolicy.hpp"
stefank@2314 35 #include "runtime/mutexLocker.hpp"
stefank@2314 36 #include "runtime/os.hpp"
stefank@2314 37 #include "runtime/sweeper.hpp"
stefank@2314 38 #include "runtime/vm_operations.hpp"
sla@5237 39 #include "trace/tracing.hpp"
stefank@2314 40 #include "utilities/events.hpp"
mgronlun@6131 41 #include "utilities/ticks.inline.hpp"
stefank@2314 42 #include "utilities/xmlstream.hpp"
duke@435 43
never@2916 44 #ifdef ASSERT
never@2916 45
never@2916 46 #define SWEEP(nm) record_sweep(nm, __LINE__)
never@2916 47 // Sweeper logging code
never@2916 48 class SweeperRecord {
never@2916 49 public:
never@2916 50 int traversal;
never@2916 51 int invocation;
never@2916 52 int compile_id;
never@2916 53 long traversal_mark;
never@2916 54 int state;
never@2916 55 const char* kind;
never@2916 56 address vep;
never@2916 57 address uep;
never@2916 58 int line;
never@2916 59
never@2916 60 void print() {
never@2916 61 tty->print_cr("traversal = %d invocation = %d compile_id = %d %s uep = " PTR_FORMAT " vep = "
never@2916 62 PTR_FORMAT " state = %d traversal_mark %d line = %d",
never@2916 63 traversal,
never@2916 64 invocation,
never@2916 65 compile_id,
never@2916 66 kind == NULL ? "" : kind,
never@2916 67 uep,
never@2916 68 vep,
never@2916 69 state,
never@2916 70 traversal_mark,
never@2916 71 line);
never@2916 72 }
never@2916 73 };
never@2916 74
never@2916 75 static int _sweep_index = 0;
never@2916 76 static SweeperRecord* _records = NULL;
never@2916 77
never@2916 78 void NMethodSweeper::report_events(int id, address entry) {
never@2916 79 if (_records != NULL) {
never@2916 80 for (int i = _sweep_index; i < SweeperLogEntries; i++) {
never@2916 81 if (_records[i].uep == entry ||
never@2916 82 _records[i].vep == entry ||
never@2916 83 _records[i].compile_id == id) {
never@2916 84 _records[i].print();
never@2916 85 }
never@2916 86 }
never@2916 87 for (int i = 0; i < _sweep_index; i++) {
never@2916 88 if (_records[i].uep == entry ||
never@2916 89 _records[i].vep == entry ||
never@2916 90 _records[i].compile_id == id) {
never@2916 91 _records[i].print();
never@2916 92 }
never@2916 93 }
never@2916 94 }
never@2916 95 }
never@2916 96
never@2916 97 void NMethodSweeper::report_events() {
never@2916 98 if (_records != NULL) {
never@2916 99 for (int i = _sweep_index; i < SweeperLogEntries; i++) {
never@2916 100 // skip empty records
never@2916 101 if (_records[i].vep == NULL) continue;
never@2916 102 _records[i].print();
never@2916 103 }
never@2916 104 for (int i = 0; i < _sweep_index; i++) {
never@2916 105 // skip empty records
never@2916 106 if (_records[i].vep == NULL) continue;
never@2916 107 _records[i].print();
never@2916 108 }
never@2916 109 }
never@2916 110 }
never@2916 111
never@2916 112 void NMethodSweeper::record_sweep(nmethod* nm, int line) {
never@2916 113 if (_records != NULL) {
never@2916 114 _records[_sweep_index].traversal = _traversals;
never@2916 115 _records[_sweep_index].traversal_mark = nm->_stack_traversal_mark;
anoll@6099 116 _records[_sweep_index].invocation = _sweep_fractions_left;
never@2916 117 _records[_sweep_index].compile_id = nm->compile_id();
never@2916 118 _records[_sweep_index].kind = nm->compile_kind();
never@2916 119 _records[_sweep_index].state = nm->_state;
never@2916 120 _records[_sweep_index].vep = nm->verified_entry_point();
never@2916 121 _records[_sweep_index].uep = nm->entry_point();
never@2916 122 _records[_sweep_index].line = line;
never@2916 123 _sweep_index = (_sweep_index + 1) % SweeperLogEntries;
never@2916 124 }
never@2916 125 }
never@2916 126 #else
never@2916 127 #define SWEEP(nm)
never@2916 128 #endif
never@2916 129
anoll@6099 130 nmethod* NMethodSweeper::_current = NULL; // Current nmethod
anoll@6099 131 long NMethodSweeper::_traversals = 0; // Stack scan count, also sweep ID.
anoll@6099 132 long NMethodSweeper::_time_counter = 0; // Virtual time used to periodically invoke sweeper
anoll@6099 133 long NMethodSweeper::_last_sweep = 0; // Value of _time_counter when the last sweep happened
anoll@6099 134 int NMethodSweeper::_seen = 0; // Nof. nmethod we have currently processed in current pass of CodeCache
anoll@6099 135 int NMethodSweeper::_flushed_count = 0; // Nof. nmethods flushed in current sweep
anoll@6099 136 int NMethodSweeper::_zombified_count = 0; // Nof. nmethods made zombie in current sweep
anoll@6099 137 int NMethodSweeper::_marked_for_reclamation_count = 0; // Nof. nmethods marked for reclaim in current sweep
never@2916 138
anoll@6099 139 volatile bool NMethodSweeper::_should_sweep = true; // Indicates if we should invoke the sweeper
anoll@6099 140 volatile int NMethodSweeper::_sweep_fractions_left = 0; // Nof. invocations left until we are completed with this pass
anoll@6099 141 volatile int NMethodSweeper::_sweep_started = 0; // Flag to control conc sweeper
anoll@6099 142 volatile int NMethodSweeper::_bytes_changed = 0; // Counts the total nmethod size if the nmethod changed from:
anoll@6099 143 // 1) alive -> not_entrant
anoll@6099 144 // 2) not_entrant -> zombie
anoll@6099 145 // 3) zombie -> marked_for_reclamation
duke@435 146
anoll@6099 147 int NMethodSweeper::_total_nof_methods_reclaimed = 0; // Accumulated nof methods flushed
mgronlun@6131 148 Tickspan NMethodSweeper::_total_time_sweeping; // Accumulated time sweeping
mgronlun@6131 149 Tickspan NMethodSweeper::_total_time_this_sweep; // Total time this sweep
mgronlun@6131 150 Tickspan NMethodSweeper::_peak_sweep_time; // Peak time for a full sweep
mgronlun@6131 151 Tickspan NMethodSweeper::_peak_sweep_fraction_time; // Peak time sweeping one fraction
anoll@6099 152 int NMethodSweeper::_hotness_counter_reset_val = 0;
anoll@5792 153
sla@5237 154
jrose@1424 155 class MarkActivationClosure: public CodeBlobClosure {
jrose@1424 156 public:
jrose@1424 157 virtual void do_code_blob(CodeBlob* cb) {
anoll@5792 158 if (cb->is_nmethod()) {
anoll@5792 159 nmethod* nm = (nmethod*)cb;
anoll@5792 160 nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val());
anoll@5792 161 // If we see an activation belonging to a non_entrant nmethod, we mark it.
anoll@5792 162 if (nm->is_not_entrant()) {
anoll@5792 163 nm->mark_as_seen_on_stack();
anoll@5792 164 }
jrose@1424 165 }
jrose@1424 166 }
jrose@1424 167 };
jrose@1424 168 static MarkActivationClosure mark_activation_closure;
jrose@1424 169
anoll@5792 170 class SetHotnessClosure: public CodeBlobClosure {
anoll@5792 171 public:
anoll@5792 172 virtual void do_code_blob(CodeBlob* cb) {
anoll@5792 173 if (cb->is_nmethod()) {
anoll@5792 174 nmethod* nm = (nmethod*)cb;
anoll@5792 175 nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val());
anoll@5792 176 }
anoll@5792 177 }
anoll@5792 178 };
anoll@5792 179 static SetHotnessClosure set_hotness_closure;
anoll@5792 180
anoll@5792 181
anoll@5792 182 int NMethodSweeper::hotness_counter_reset_val() {
anoll@5792 183 if (_hotness_counter_reset_val == 0) {
anoll@5792 184 _hotness_counter_reset_val = (ReservedCodeCacheSize < M) ? 1 : (ReservedCodeCacheSize / M) * 2;
anoll@5792 185 }
anoll@5792 186 return _hotness_counter_reset_val;
anoll@5792 187 }
neliasso@5038 188 bool NMethodSweeper::sweep_in_progress() {
neliasso@5038 189 return (_current != NULL);
neliasso@5038 190 }
neliasso@5038 191
anoll@5792 192 // Scans the stacks of all Java threads and marks activations of not-entrant methods.
anoll@5792 193 // No need to synchronize access, since 'mark_active_nmethods' is always executed at a
anoll@5792 194 // safepoint.
anoll@5792 195 void NMethodSweeper::mark_active_nmethods() {
duke@435 196 assert(SafepointSynchronize::is_at_safepoint(), "must be executed at a safepoint");
anoll@5792 197 // If we do not want to reclaim not-entrant or zombie methods there is no need
anoll@5792 198 // to scan stacks
anoll@5792 199 if (!MethodFlushing) {
anoll@5792 200 return;
anoll@5792 201 }
duke@435 202
anoll@6099 203 // Increase time so that we can estimate when to invoke the sweeper again.
anoll@6099 204 _time_counter++;
anoll@6099 205
duke@435 206 // Check for restart
duke@435 207 assert(CodeCache::find_blob_unsafe(_current) == _current, "Sweeper nmethod cached state invalid");
anoll@6099 208 if (!sweep_in_progress()) {
anoll@6099 209 _seen = 0;
anoll@6099 210 _sweep_fractions_left = NmethodSweepFraction;
anoll@6099 211 _current = CodeCache::first_nmethod();
anoll@6099 212 _traversals += 1;
mgronlun@6131 213 _total_time_this_sweep = Tickspan();
sla@5237 214
duke@435 215 if (PrintMethodFlushing) {
duke@435 216 tty->print_cr("### Sweep: stack traversal %d", _traversals);
duke@435 217 }
jrose@1424 218 Threads::nmethods_do(&mark_activation_closure);
duke@435 219
anoll@5792 220 } else {
anoll@5792 221 // Only set hotness counter
anoll@5792 222 Threads::nmethods_do(&set_hotness_closure);
duke@435 223 }
duke@435 224
anoll@5792 225 OrderAccess::storestore();
duke@435 226 }
anoll@6099 227 /**
anoll@6099 228 * This function invokes the sweeper if at least one of the three conditions is met:
anoll@6099 229 * (1) The code cache is getting full
anoll@6099 230 * (2) There are sufficient state changes in/since the last sweep.
anoll@6099 231 * (3) We have not been sweeping for 'some time'
anoll@6099 232 */
never@1893 233 void NMethodSweeper::possibly_sweep() {
never@1999 234 assert(JavaThread::current()->thread_state() == _thread_in_vm, "must run in vm mode");
anoll@6114 235 // Only compiler threads are allowed to sweep
anoll@6114 236 if (!MethodFlushing || !sweep_in_progress() || !Thread::current()->is_Compiler_thread()) {
anoll@5792 237 return;
anoll@5792 238 }
never@1893 239
anoll@6099 240 // If there was no state change while nmethod sweeping, 'should_sweep' will be false.
anoll@6099 241 // This is one of the two places where should_sweep can be set to true. The general
anoll@6099 242 // idea is as follows: If there is enough free space in the code cache, there is no
anoll@6099 243 // need to invoke the sweeper. The following formula (which determines whether to invoke
anoll@6099 244 // the sweeper or not) depends on the assumption that for larger ReservedCodeCacheSizes
anoll@6099 245 // we need less frequent sweeps than for smaller ReservedCodecCacheSizes. Furthermore,
anoll@6099 246 // the formula considers how much space in the code cache is currently used. Here are
anoll@6099 247 // some examples that will (hopefully) help in understanding.
anoll@6099 248 //
anoll@6099 249 // Small ReservedCodeCacheSizes: (e.g., < 16M) We invoke the sweeper every time, since
anoll@6099 250 // the result of the division is 0. This
anoll@6099 251 // keeps the used code cache size small
anoll@6099 252 // (important for embedded Java)
anoll@6099 253 // Large ReservedCodeCacheSize : (e.g., 256M + code cache is 10% full). The formula
anoll@6099 254 // computes: (256 / 16) - 1 = 15
anoll@6099 255 // As a result, we invoke the sweeper after
anoll@6099 256 // 15 invocations of 'mark_active_nmethods.
anoll@6099 257 // Large ReservedCodeCacheSize: (e.g., 256M + code Cache is 90% full). The formula
anoll@6099 258 // computes: (256 / 16) - 10 = 6.
anoll@6099 259 if (!_should_sweep) {
anoll@6099 260 int time_since_last_sweep = _time_counter - _last_sweep;
anoll@6099 261 double wait_until_next_sweep = (ReservedCodeCacheSize / (16 * M)) - time_since_last_sweep -
anoll@6099 262 CodeCache::reverse_free_ratio();
anoll@6099 263
anoll@6099 264 if ((wait_until_next_sweep <= 0.0) || !CompileBroker::should_compile_new_jobs()) {
anoll@6099 265 _should_sweep = true;
anoll@6099 266 }
anoll@6099 267 }
anoll@6099 268
anoll@6099 269 if (_should_sweep && _sweep_fractions_left > 0) {
never@1893 270 // Only one thread at a time will sweep
never@1893 271 jint old = Atomic::cmpxchg( 1, &_sweep_started, 0 );
never@1893 272 if (old != 0) {
never@1893 273 return;
never@1893 274 }
never@2916 275 #ifdef ASSERT
never@2916 276 if (LogSweeper && _records == NULL) {
never@2916 277 // Create the ring buffer for the logging code
zgu@3900 278 _records = NEW_C_HEAP_ARRAY(SweeperRecord, SweeperLogEntries, mtGC);
never@2916 279 memset(_records, 0, sizeof(SweeperRecord) * SweeperLogEntries);
never@2916 280 }
never@2916 281 #endif
anoll@6099 282
anoll@6099 283 if (_sweep_fractions_left > 0) {
never@1999 284 sweep_code_cache();
anoll@6099 285 _sweep_fractions_left--;
anoll@6099 286 }
anoll@6099 287
anoll@6099 288 // We are done with sweeping the code cache once.
anoll@6099 289 if (_sweep_fractions_left == 0) {
anoll@6099 290 _last_sweep = _time_counter;
anoll@6099 291 // Reset flag; temporarily disables sweeper
anoll@6099 292 _should_sweep = false;
anoll@6099 293 // If there was enough state change, 'possibly_enable_sweeper()'
anoll@6099 294 // sets '_should_sweep' to true
anoll@6099 295 possibly_enable_sweeper();
anoll@6099 296 // Reset _bytes_changed only if there was enough state change. _bytes_changed
anoll@6099 297 // can further increase by calls to 'report_state_change'.
anoll@6099 298 if (_should_sweep) {
anoll@6099 299 _bytes_changed = 0;
anoll@6099 300 }
never@1999 301 }
goetz@6493 302 // Release work, because another compiler thread could continue.
goetz@6493 303 OrderAccess::release_store((int*)&_sweep_started, 0);
never@1893 304 }
never@1893 305 }
never@1893 306
never@1893 307 void NMethodSweeper::sweep_code_cache() {
mgronlun@6131 308 Ticks sweep_start_counter = Ticks::now();
sla@5237 309
anoll@6099 310 _flushed_count = 0;
anoll@6099 311 _zombified_count = 0;
anoll@6099 312 _marked_for_reclamation_count = 0;
sla@5237 313
never@1893 314 if (PrintMethodFlushing && Verbose) {
anoll@6099 315 tty->print_cr("### Sweep at %d out of %d. Invocations left: %d", _seen, CodeCache::nof_nmethods(), _sweep_fractions_left);
never@1893 316 }
never@1893 317
neliasso@5038 318 if (!CompileBroker::should_compile_new_jobs()) {
neliasso@5038 319 // If we have turned off compilations we might as well do full sweeps
neliasso@5038 320 // in order to reach the clean state faster. Otherwise the sleeping compiler
anoll@5792 321 // threads will slow down sweeping.
anoll@6099 322 _sweep_fractions_left = 1;
neliasso@5038 323 }
neliasso@5038 324
never@1999 325 // We want to visit all nmethods after NmethodSweepFraction
never@1999 326 // invocations so divide the remaining number of nmethods by the
never@1999 327 // remaining number of invocations. This is only an estimate since
never@1999 328 // the number of nmethods changes during the sweep so the final
never@1999 329 // stage must iterate until it there are no more nmethods.
anoll@6099 330 int todo = (CodeCache::nof_nmethods() - _seen) / _sweep_fractions_left;
anoll@5734 331 int swept_count = 0;
never@1893 332
anoll@5792 333
never@1893 334 assert(!SafepointSynchronize::is_at_safepoint(), "should not be in safepoint when we get here");
never@1893 335 assert(!CodeCache_lock->owned_by_self(), "just checking");
never@1893 336
anoll@5792 337 int freed_memory = 0;
never@1893 338 {
never@1893 339 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
never@1893 340
never@1999 341 // The last invocation iterates until there are no more nmethods
anoll@6099 342 for (int i = 0; (i < todo || _sweep_fractions_left == 1) && _current != NULL; i++) {
anoll@5734 343 swept_count++;
iveresov@3572 344 if (SafepointSynchronize::is_synchronizing()) { // Safepoint request
iveresov@3572 345 if (PrintMethodFlushing && Verbose) {
anoll@6099 346 tty->print_cr("### Sweep at %d out of %d, invocation: %d, yielding to safepoint", _seen, CodeCache::nof_nmethods(), _sweep_fractions_left);
iveresov@3572 347 }
iveresov@3572 348 MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
never@1893 349
iveresov@3572 350 assert(Thread::current()->is_Java_thread(), "should be java thread");
iveresov@3572 351 JavaThread* thread = (JavaThread*)Thread::current();
iveresov@3572 352 ThreadBlockInVM tbivm(thread);
iveresov@3572 353 thread->java_suspend_self();
iveresov@3572 354 }
never@1999 355 // Since we will give up the CodeCache_lock, always skip ahead
never@1999 356 // to the next nmethod. Other blobs can be deleted by other
never@1999 357 // threads but nmethods are only reclaimed by the sweeper.
never@1970 358 nmethod* next = CodeCache::next_nmethod(_current);
never@1893 359
never@1893 360 // Now ready to process nmethod and give up CodeCache_lock
never@1893 361 {
never@1893 362 MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
anoll@5792 363 freed_memory += process_nmethod(_current);
never@1893 364 }
never@1893 365 _seen++;
never@1893 366 _current = next;
never@1893 367 }
never@1893 368 }
never@1893 369
anoll@6099 370 assert(_sweep_fractions_left > 1 || _current == NULL, "must have scanned the whole cache");
never@1893 371
mgronlun@6131 372 const Ticks sweep_end_counter = Ticks::now();
mgronlun@6131 373 const Tickspan sweep_time = sweep_end_counter - sweep_start_counter;
sla@5237 374 _total_time_sweeping += sweep_time;
sla@5237 375 _total_time_this_sweep += sweep_time;
sla@5237 376 _peak_sweep_fraction_time = MAX2(sweep_time, _peak_sweep_fraction_time);
sla@5237 377 _total_nof_methods_reclaimed += _flushed_count;
sla@5237 378
sla@5237 379 EventSweepCodeCache event(UNTIMED);
sla@5237 380 if (event.should_commit()) {
sla@5237 381 event.set_starttime(sweep_start_counter);
sla@5237 382 event.set_endtime(sweep_end_counter);
sla@5237 383 event.set_sweepIndex(_traversals);
anoll@6099 384 event.set_sweepFractionIndex(NmethodSweepFraction - _sweep_fractions_left + 1);
anoll@5734 385 event.set_sweptCount(swept_count);
sla@5237 386 event.set_flushedCount(_flushed_count);
anoll@6099 387 event.set_markedCount(_marked_for_reclamation_count);
sla@5237 388 event.set_zombifiedCount(_zombified_count);
sla@5237 389 event.commit();
sla@5237 390 }
sla@5237 391
never@1893 392 #ifdef ASSERT
never@1893 393 if(PrintMethodFlushing) {
mgronlun@6131 394 tty->print_cr("### sweeper: sweep time(%d): "
mgronlun@6131 395 INT64_FORMAT, _sweep_fractions_left, (jlong)sweep_time.value());
never@1893 396 }
never@1893 397 #endif
never@1999 398
anoll@6099 399 if (_sweep_fractions_left == 1) {
sla@5237 400 _peak_sweep_time = MAX2(_peak_sweep_time, _total_time_this_sweep);
never@1999 401 log_sweep("finished");
never@1999 402 }
neliasso@5038 403
anoll@5792 404 // Sweeper is the only case where memory is released, check here if it
anoll@5792 405 // is time to restart the compiler. Only checking if there is a certain
anoll@5792 406 // amount of free memory in the code cache might lead to re-enabling
anoll@5792 407 // compilation although no memory has been released. For example, there are
anoll@5792 408 // cases when compilation was disabled although there is 4MB (or more) free
anoll@5792 409 // memory in the code cache. The reason is code cache fragmentation. Therefore,
anoll@5792 410 // it only makes sense to re-enable compilation if we have actually freed memory.
anoll@5792 411 // Note that typically several kB are released for sweeping 16MB of the code
anoll@5792 412 // cache. As a result, 'freed_memory' > 0 to restart the compiler.
anoll@6099 413 if (!CompileBroker::should_compile_new_jobs() && (freed_memory > 0)) {
neliasso@5038 414 CompileBroker::set_should_compile_new_jobs(CompileBroker::run_compilation);
neliasso@5038 415 log_sweep("restart_compiler");
neliasso@5038 416 }
never@1893 417 }
never@1893 418
anoll@6099 419 /**
anoll@6099 420 * This function updates the sweeper statistics that keep track of nmethods
anoll@6099 421 * state changes. If there is 'enough' state change, the sweeper is invoked
anoll@6099 422 * as soon as possible. There can be data races on _bytes_changed. The data
anoll@6099 423 * races are benign, since it does not matter if we loose a couple of bytes.
anoll@6099 424 * In the worst case we call the sweeper a little later. Also, we are guaranteed
anoll@6099 425 * to invoke the sweeper if the code cache gets full.
anoll@6099 426 */
anoll@6099 427 void NMethodSweeper::report_state_change(nmethod* nm) {
anoll@6099 428 _bytes_changed += nm->total_size();
anoll@6099 429 possibly_enable_sweeper();
anoll@6099 430 }
anoll@6099 431
anoll@6099 432 /**
anoll@6099 433 * Function determines if there was 'enough' state change in the code cache to invoke
anoll@6099 434 * the sweeper again. Currently, we determine 'enough' as more than 1% state change in
anoll@6099 435 * the code cache since the last sweep.
anoll@6099 436 */
anoll@6099 437 void NMethodSweeper::possibly_enable_sweeper() {
anoll@6099 438 double percent_changed = ((double)_bytes_changed / (double)ReservedCodeCacheSize) * 100;
anoll@6099 439 if (percent_changed > 1.0) {
anoll@6099 440 _should_sweep = true;
anoll@6099 441 }
anoll@6099 442 }
anoll@6099 443
never@2916 444 class NMethodMarker: public StackObj {
never@2916 445 private:
never@2916 446 CompilerThread* _thread;
never@2916 447 public:
never@2916 448 NMethodMarker(nmethod* nm) {
never@2916 449 _thread = CompilerThread::current();
coleenp@4037 450 if (!nm->is_zombie() && !nm->is_unloaded()) {
coleenp@4037 451 // Only expose live nmethods for scanning
anoll@5792 452 _thread->set_scanned_nmethod(nm);
anoll@5792 453 }
coleenp@4037 454 }
never@2916 455 ~NMethodMarker() {
never@2916 456 _thread->set_scanned_nmethod(NULL);
never@2916 457 }
never@2916 458 };
never@2916 459
coleenp@4037 460 void NMethodSweeper::release_nmethod(nmethod *nm) {
coleenp@4037 461 // Clean up any CompiledICHolders
coleenp@4037 462 {
coleenp@4037 463 ResourceMark rm;
coleenp@4037 464 MutexLocker ml_patch(CompiledIC_lock);
coleenp@4037 465 RelocIterator iter(nm);
coleenp@4037 466 while (iter.next()) {
coleenp@4037 467 if (iter.type() == relocInfo::virtual_call_type) {
coleenp@4037 468 CompiledIC::cleanup_call_site(iter.virtual_call_reloc());
coleenp@4037 469 }
coleenp@4037 470 }
coleenp@4037 471 }
coleenp@4037 472
coleenp@4037 473 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
coleenp@4037 474 nm->flush();
coleenp@4037 475 }
duke@435 476
anoll@5792 477 int NMethodSweeper::process_nmethod(nmethod *nm) {
never@1893 478 assert(!CodeCache_lock->owned_by_self(), "just checking");
never@1893 479
anoll@5792 480 int freed_memory = 0;
never@2916 481 // Make sure this nmethod doesn't get unloaded during the scan,
anoll@5792 482 // since safepoints may happen during acquired below locks.
never@2916 483 NMethodMarker nmm(nm);
never@2916 484 SWEEP(nm);
never@2916 485
duke@435 486 // Skip methods that are currently referenced by the VM
duke@435 487 if (nm->is_locked_by_vm()) {
duke@435 488 // But still remember to clean-up inline caches for alive nmethods
duke@435 489 if (nm->is_alive()) {
anoll@5792 490 // Clean inline caches that point to zombie/non-entrant methods
never@1893 491 MutexLocker cl(CompiledIC_lock);
duke@435 492 nm->cleanup_inline_caches();
never@2916 493 SWEEP(nm);
duke@435 494 }
anoll@5792 495 return freed_memory;
duke@435 496 }
duke@435 497
duke@435 498 if (nm->is_zombie()) {
anoll@5792 499 // If it is the first time we see nmethod then we mark it. Otherwise,
anoll@5792 500 // we reclaim it. When we have seen a zombie method twice, we know that
never@1999 501 // there are no inline caches that refer to it.
duke@435 502 if (nm->is_marked_for_reclamation()) {
duke@435 503 assert(!nm->is_locked_by_vm(), "must not flush locked nmethods");
ysr@1376 504 if (PrintMethodFlushing && Verbose) {
kvn@1637 505 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (marked for reclamation) being flushed", nm->compile_id(), nm);
ysr@1376 506 }
anoll@5792 507 freed_memory = nm->total_size();
coleenp@4037 508 release_nmethod(nm);
sla@5237 509 _flushed_count++;
duke@435 510 } else {
ysr@1376 511 if (PrintMethodFlushing && Verbose) {
kvn@1637 512 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (zombie) being marked for reclamation", nm->compile_id(), nm);
ysr@1376 513 }
duke@435 514 nm->mark_for_reclamation();
anoll@6099 515 // Keep track of code cache state change
anoll@6099 516 _bytes_changed += nm->total_size();
anoll@6099 517 _marked_for_reclamation_count++;
never@2916 518 SWEEP(nm);
duke@435 519 }
duke@435 520 } else if (nm->is_not_entrant()) {
anoll@5792 521 // If there are no current activations of this method on the
duke@435 522 // stack we can safely convert it to a zombie method
duke@435 523 if (nm->can_not_entrant_be_converted()) {
ysr@1376 524 if (PrintMethodFlushing && Verbose) {
kvn@1637 525 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (not entrant) being made zombie", nm->compile_id(), nm);
ysr@1376 526 }
anoll@6099 527 // Code cache state change is tracked in make_zombie()
duke@435 528 nm->make_zombie();
sla@5237 529 _zombified_count++;
never@2916 530 SWEEP(nm);
duke@435 531 } else {
duke@435 532 // Still alive, clean up its inline caches
never@1893 533 MutexLocker cl(CompiledIC_lock);
duke@435 534 nm->cleanup_inline_caches();
never@2916 535 SWEEP(nm);
duke@435 536 }
duke@435 537 } else if (nm->is_unloaded()) {
duke@435 538 // Unloaded code, just make it a zombie
anoll@5792 539 if (PrintMethodFlushing && Verbose) {
kvn@1637 540 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (unloaded) being made zombie", nm->compile_id(), nm);
anoll@5792 541 }
ysr@1376 542 if (nm->is_osr_method()) {
coleenp@4037 543 SWEEP(nm);
duke@435 544 // No inline caches will ever point to osr methods, so we can just remove it
anoll@5792 545 freed_memory = nm->total_size();
coleenp@4037 546 release_nmethod(nm);
sla@5237 547 _flushed_count++;
duke@435 548 } else {
anoll@6099 549 // Code cache state change is tracked in make_zombie()
duke@435 550 nm->make_zombie();
sla@5237 551 _zombified_count++;
never@2916 552 SWEEP(nm);
duke@435 553 }
duke@435 554 } else {
kvn@1637 555 if (UseCodeCacheFlushing) {
anoll@5792 556 if (!nm->is_locked_by_vm() && !nm->is_osr_method() && !nm->is_native_method()) {
anoll@5792 557 // Do not make native methods and OSR-methods not-entrant
anoll@5792 558 nm->dec_hotness_counter();
anoll@5792 559 // Get the initial value of the hotness counter. This value depends on the
anoll@5792 560 // ReservedCodeCacheSize
anoll@5792 561 int reset_val = hotness_counter_reset_val();
anoll@5792 562 int time_since_reset = reset_val - nm->hotness_counter();
anoll@5792 563 double threshold = -reset_val + (CodeCache::reverse_free_ratio() * NmethodSweepActivity);
anoll@5792 564 // The less free space in the code cache we have - the bigger reverse_free_ratio() is.
anoll@5792 565 // I.e., 'threshold' increases with lower available space in the code cache and a higher
anoll@5792 566 // NmethodSweepActivity. If the current hotness counter - which decreases from its initial
anoll@5792 567 // value until it is reset by stack walking - is smaller than the computed threshold, the
anoll@5792 568 // corresponding nmethod is considered for removal.
anoll@5792 569 if ((NmethodSweepActivity > 0) && (nm->hotness_counter() < threshold) && (time_since_reset > 10)) {
anoll@5792 570 // A method is marked as not-entrant if the method is
anoll@5792 571 // 1) 'old enough': nm->hotness_counter() < threshold
anoll@5792 572 // 2) The method was in_use for a minimum amount of time: (time_since_reset > 10)
anoll@5792 573 // The second condition is necessary if we are dealing with very small code cache
anoll@5792 574 // sizes (e.g., <10m) and the code cache size is too small to hold all hot methods.
anoll@5792 575 // The second condition ensures that methods are not immediately made not-entrant
anoll@5792 576 // after compilation.
anoll@5792 577 nm->make_not_entrant();
anoll@6099 578 // Code cache state change is tracked in make_not_entrant()
anoll@6099 579 if (PrintMethodFlushing && Verbose) {
anoll@6099 580 tty->print_cr("### Nmethod %d/" PTR_FORMAT "made not-entrant: hotness counter %d/%d threshold %f",
anoll@6099 581 nm->compile_id(), nm, nm->hotness_counter(), reset_val, threshold);
anoll@6099 582 }
anoll@5792 583 }
kvn@1637 584 }
kvn@1637 585 }
anoll@5792 586 // Clean-up all inline caches that point to zombie/non-reentrant methods
never@1893 587 MutexLocker cl(CompiledIC_lock);
duke@435 588 nm->cleanup_inline_caches();
never@2916 589 SWEEP(nm);
duke@435 590 }
anoll@5792 591 return freed_memory;
duke@435 592 }
kvn@1637 593
never@1999 594 // Print out some state information about the current sweep and the
never@1999 595 // state of the code cache if it's requested.
never@1999 596 void NMethodSweeper::log_sweep(const char* msg, const char* format, ...) {
never@1999 597 if (PrintMethodFlushing) {
iveresov@2764 598 stringStream s;
iveresov@2764 599 // Dump code cache state into a buffer before locking the tty,
iveresov@2764 600 // because log_state() will use locks causing lock conflicts.
iveresov@2764 601 CodeCache::log_state(&s);
iveresov@2764 602
never@1999 603 ttyLocker ttyl;
never@1999 604 tty->print("### sweeper: %s ", msg);
never@1999 605 if (format != NULL) {
never@1999 606 va_list ap;
never@1999 607 va_start(ap, format);
never@1999 608 tty->vprint(format, ap);
never@1999 609 va_end(ap);
never@1999 610 }
iveresov@2764 611 tty->print_cr(s.as_string());
never@1999 612 }
never@1999 613
never@1999 614 if (LogCompilation && (xtty != NULL)) {
iveresov@2764 615 stringStream s;
iveresov@2764 616 // Dump code cache state into a buffer before locking the tty,
iveresov@2764 617 // because log_state() will use locks causing lock conflicts.
iveresov@2764 618 CodeCache::log_state(&s);
iveresov@2764 619
never@1999 620 ttyLocker ttyl;
never@2001 621 xtty->begin_elem("sweeper state='%s' traversals='" INTX_FORMAT "' ", msg, (intx)traversal_count());
never@1999 622 if (format != NULL) {
never@1999 623 va_list ap;
never@1999 624 va_start(ap, format);
never@1999 625 xtty->vprint(format, ap);
never@1999 626 va_end(ap);
never@1999 627 }
iveresov@2764 628 xtty->print(s.as_string());
never@1999 629 xtty->stamp();
never@1999 630 xtty->end_elem();
never@1999 631 }
never@1999 632 }

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