110
111 void NMethodSweeper::record_sweep(nmethod* nm, int line) {
112 if (_records != NULL) {
113 _records[_sweep_index].traversal = _traversals;
114 _records[_sweep_index].traversal_mark = nm->_stack_traversal_mark;
115 _records[_sweep_index].invocation = _invocations;
116 _records[_sweep_index].compile_id = nm->compile_id();
117 _records[_sweep_index].kind = nm->compile_kind();
118 _records[_sweep_index].state = nm->_state;
119 _records[_sweep_index].vep = nm->verified_entry_point();
120 _records[_sweep_index].uep = nm->entry_point();
121 _records[_sweep_index].line = line;
122
123 _sweep_index = (_sweep_index + 1) % SweeperLogEntries;
124 }
125 }
126 #else
127 #define SWEEP(nm)
128 #endif
129
130
131 long NMethodSweeper::_traversals = 0; // No. of stack traversals performed
132 nmethod* NMethodSweeper::_current = NULL; // Current nmethod
133 int NMethodSweeper::_seen = 0 ; // No. of nmethods we have currently processed in current pass of CodeCache
134 int NMethodSweeper::_flushed_count = 0; // Nof. nmethods flushed in current sweep
135 int NMethodSweeper::_zombified_count = 0; // Nof. nmethods made zombie in current sweep
136 int NMethodSweeper::_marked_count = 0; // Nof. nmethods marked for reclaim in current sweep
137
138 volatile int NMethodSweeper::_invocations = 0; // No. of invocations left until we are completed with this pass
139 volatile int NMethodSweeper::_sweep_started = 0; // Whether a sweep is in progress.
140
141 jint NMethodSweeper::_locked_seen = 0;
142 jint NMethodSweeper::_not_entrant_seen_on_stack = 0;
143 bool NMethodSweeper::_resweep = false;
144 jint NMethodSweeper::_flush_token = 0;
145 jlong NMethodSweeper::_last_full_flush_time = 0;
146 int NMethodSweeper::_highest_marked = 0;
147 int NMethodSweeper::_dead_compile_ids = 0;
148 long NMethodSweeper::_last_flush_traversal_id = 0;
149
150 int NMethodSweeper::_number_of_flushes = 0; // Total of full traversals caused by full cache
151 int NMethodSweeper::_total_nof_methods_reclaimed = 0;
152 jlong NMethodSweeper::_total_time_sweeping = 0;
153 jlong NMethodSweeper::_total_time_this_sweep = 0;
154 jlong NMethodSweeper::_peak_sweep_time = 0;
155 jlong NMethodSweeper::_peak_sweep_fraction_time = 0;
156 jlong NMethodSweeper::_total_disconnect_time = 0;
157 jlong NMethodSweeper::_peak_disconnect_time = 0;
158
159 class MarkActivationClosure: public CodeBlobClosure {
160 public:
161 virtual void do_code_blob(CodeBlob* cb) {
162 // If we see an activation belonging to a non_entrant nmethod, we mark it.
163 if (cb->is_nmethod() && ((nmethod*)cb)->is_not_entrant()) {
164 ((nmethod*)cb)->mark_as_seen_on_stack();
165 }
166 }
167 };
168 static MarkActivationClosure mark_activation_closure;
169
170 bool NMethodSweeper::sweep_in_progress() {
171 return (_current != NULL);
172 }
173
174 void NMethodSweeper::scan_stacks() {
175 assert(SafepointSynchronize::is_at_safepoint(), "must be executed at a safepoint");
176 if (!MethodFlushing) return;
177
178 // No need to synchronize access, since this is always executed at a
179 // safepoint.
180
181 // Make sure CompiledIC_lock in unlocked, since we might update some
182 // inline caches. If it is, we just bail-out and try later.
183 if (CompiledIC_lock->is_locked() || Patching_lock->is_locked()) return;
184
185 // Check for restart
186 assert(CodeCache::find_blob_unsafe(_current) == _current, "Sweeper nmethod cached state invalid");
187 if (!sweep_in_progress() && _resweep) {
188 _seen = 0;
189 _invocations = NmethodSweepFraction;
190 _current = CodeCache::first_nmethod();
191 _traversals += 1;
192 _total_time_this_sweep = 0;
193
194 if (PrintMethodFlushing) {
195 tty->print_cr("### Sweep: stack traversal %d", _traversals);
196 }
197 Threads::nmethods_do(&mark_activation_closure);
198
199 // reset the flags since we started a scan from the beginning.
200 _resweep = false;
201 _locked_seen = 0;
202 _not_entrant_seen_on_stack = 0;
203 }
204
205 if (UseCodeCacheFlushing) {
206 // only allow new flushes after the interval is complete.
207 jlong now = os::javaTimeMillis();
208 jlong max_interval = (jlong)MinCodeCacheFlushingInterval * (jlong)1000;
209 jlong curr_interval = now - _last_full_flush_time;
210 if (curr_interval > max_interval) {
211 _flush_token = 0;
212 }
213
214 if (!CodeCache::needs_flushing() && !CompileBroker::should_compile_new_jobs()) {
215 CompileBroker::set_should_compile_new_jobs(CompileBroker::run_compilation);
216 log_sweep("restart_compiler");
217 }
218 }
219 }
220
221 void NMethodSweeper::possibly_sweep() {
222 assert(JavaThread::current()->thread_state() == _thread_in_vm, "must run in vm mode");
223 if (!MethodFlushing || !sweep_in_progress()) return;
224
225 if (_invocations > 0) {
226 // Only one thread at a time will sweep
227 jint old = Atomic::cmpxchg( 1, &_sweep_started, 0 );
228 if (old != 0) {
229 return;
230 }
231 #ifdef ASSERT
232 if (LogSweeper && _records == NULL) {
233 // Create the ring buffer for the logging code
234 _records = NEW_C_HEAP_ARRAY(SweeperRecord, SweeperLogEntries, mtGC);
235 memset(_records, 0, sizeof(SweeperRecord) * SweeperLogEntries);
236 }
237 #endif
238 if (_invocations > 0) {
239 sweep_code_cache();
240 _invocations--;
241 }
242 _sweep_started = 0;
243 }
244 }
245
246 void NMethodSweeper::sweep_code_cache() {
247
248 jlong sweep_start_counter = os::elapsed_counter();
249
250 _flushed_count = 0;
251 _zombified_count = 0;
252 _marked_count = 0;
253
254 if (PrintMethodFlushing && Verbose) {
255 tty->print_cr("### Sweep at %d out of %d. Invocations left: %d", _seen, CodeCache::nof_nmethods(), _invocations);
256 }
257
258 if (!CompileBroker::should_compile_new_jobs()) {
259 // If we have turned off compilations we might as well do full sweeps
260 // in order to reach the clean state faster. Otherwise the sleeping compiler
261 // threads will slow down sweeping. After a few iterations the cache
262 // will be clean and sweeping stops (_resweep will not be set)
263 _invocations = 1;
264 }
265
266 // We want to visit all nmethods after NmethodSweepFraction
267 // invocations so divide the remaining number of nmethods by the
268 // remaining number of invocations. This is only an estimate since
269 // the number of nmethods changes during the sweep so the final
270 // stage must iterate until it there are no more nmethods.
271 int todo = (CodeCache::nof_nmethods() - _seen) / _invocations;
272
273 assert(!SafepointSynchronize::is_at_safepoint(), "should not be in safepoint when we get here");
274 assert(!CodeCache_lock->owned_by_self(), "just checking");
275
276 {
277 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
278
279 // The last invocation iterates until there are no more nmethods
280 for (int i = 0; (i < todo || _invocations == 1) && _current != NULL; i++) {
281 if (SafepointSynchronize::is_synchronizing()) { // Safepoint request
282 if (PrintMethodFlushing && Verbose) {
283 tty->print_cr("### Sweep at %d out of %d, invocation: %d, yielding to safepoint", _seen, CodeCache::nof_nmethods(), _invocations);
284 }
285 MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
286
287 assert(Thread::current()->is_Java_thread(), "should be java thread");
288 JavaThread* thread = (JavaThread*)Thread::current();
289 ThreadBlockInVM tbivm(thread);
290 thread->java_suspend_self();
291 }
292 // Since we will give up the CodeCache_lock, always skip ahead
293 // to the next nmethod. Other blobs can be deleted by other
294 // threads but nmethods are only reclaimed by the sweeper.
295 nmethod* next = CodeCache::next_nmethod(_current);
296
297 // Now ready to process nmethod and give up CodeCache_lock
298 {
299 MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
300 process_nmethod(_current);
301 }
302 _seen++;
303 _current = next;
304 }
305 }
306
307 assert(_invocations > 1 || _current == NULL, "must have scanned the whole cache");
308
309 if (!sweep_in_progress() && !_resweep && (_locked_seen || _not_entrant_seen_on_stack)) {
310 // we've completed a scan without making progress but there were
311 // nmethods we were unable to process either because they were
312 // locked or were still on stack. We don't have to aggresively
313 // clean them up so just stop scanning. We could scan once more
314 // but that complicates the control logic and it's unlikely to
315 // matter much.
316 if (PrintMethodFlushing) {
317 tty->print_cr("### Couldn't make progress on some nmethods so stopping sweep");
318 }
319 }
320
321 jlong sweep_end_counter = os::elapsed_counter();
322 jlong sweep_time = sweep_end_counter - sweep_start_counter;
323 _total_time_sweeping += sweep_time;
324 _total_time_this_sweep += sweep_time;
325 _peak_sweep_fraction_time = MAX2(sweep_time, _peak_sweep_fraction_time);
326 _total_nof_methods_reclaimed += _flushed_count;
327
328 EventSweepCodeCache event(UNTIMED);
329 if (event.should_commit()) {
330 event.set_starttime(sweep_start_counter);
331 event.set_endtime(sweep_end_counter);
332 event.set_sweepIndex(_traversals);
333 event.set_sweepFractionIndex(NmethodSweepFraction - _invocations + 1);
334 event.set_sweptCount(todo);
335 event.set_flushedCount(_flushed_count);
336 event.set_markedCount(_marked_count);
337 event.set_zombifiedCount(_zombified_count);
338 event.commit();
339 }
340
341 #ifdef ASSERT
342 if(PrintMethodFlushing) {
343 tty->print_cr("### sweeper: sweep time(%d): " INT64_FORMAT, _invocations, (jlong)sweep_time);
344 }
345 #endif
346
347 if (_invocations == 1) {
348 _peak_sweep_time = MAX2(_peak_sweep_time, _total_time_this_sweep);
349 log_sweep("finished");
350 }
351
352 // Sweeper is the only case where memory is released,
353 // check here if it is time to restart the compiler.
354 if (UseCodeCacheFlushing && !CompileBroker::should_compile_new_jobs() && !CodeCache::needs_flushing()) {
355 CompileBroker::set_should_compile_new_jobs(CompileBroker::run_compilation);
356 log_sweep("restart_compiler");
357 }
358 }
359
360 class NMethodMarker: public StackObj {
361 private:
362 CompilerThread* _thread;
363 public:
364 NMethodMarker(nmethod* nm) {
365 _thread = CompilerThread::current();
366 if (!nm->is_zombie() && !nm->is_unloaded()) {
367 // Only expose live nmethods for scanning
368 _thread->set_scanned_nmethod(nm);
369 }
370 }
371 ~NMethodMarker() {
372 _thread->set_scanned_nmethod(NULL);
373 }
374 };
375
376 void NMethodSweeper::release_nmethod(nmethod *nm) {
377 // Clean up any CompiledICHolders
378 {
379 ResourceMark rm;
380 MutexLocker ml_patch(CompiledIC_lock);
381 RelocIterator iter(nm);
382 while (iter.next()) {
383 if (iter.type() == relocInfo::virtual_call_type) {
384 CompiledIC::cleanup_call_site(iter.virtual_call_reloc());
385 }
386 }
387 }
388
389 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
390 nm->flush();
391 }
392
393 void NMethodSweeper::process_nmethod(nmethod *nm) {
394 assert(!CodeCache_lock->owned_by_self(), "just checking");
395
396 // Make sure this nmethod doesn't get unloaded during the scan,
397 // since the locks acquired below might safepoint.
398 NMethodMarker nmm(nm);
399
400 SWEEP(nm);
401
402 // Skip methods that are currently referenced by the VM
403 if (nm->is_locked_by_vm()) {
404 // But still remember to clean-up inline caches for alive nmethods
405 if (nm->is_alive()) {
406 // Clean-up all inline caches that points to zombie/non-reentrant methods
407 MutexLocker cl(CompiledIC_lock);
408 nm->cleanup_inline_caches();
409 SWEEP(nm);
410 } else {
411 _locked_seen++;
412 SWEEP(nm);
413 }
414 return;
415 }
416
417 if (nm->is_zombie()) {
418 // If it is first time, we see nmethod then we mark it. Otherwise,
419 // we reclame it. When we have seen a zombie method twice, we know that
420 // there are no inline caches that refer to it.
421 if (nm->is_marked_for_reclamation()) {
422 assert(!nm->is_locked_by_vm(), "must not flush locked nmethods");
423 if (PrintMethodFlushing && Verbose) {
424 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (marked for reclamation) being flushed", nm->compile_id(), nm);
425 }
426 release_nmethod(nm);
427 _flushed_count++;
428 } else {
429 if (PrintMethodFlushing && Verbose) {
430 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (zombie) being marked for reclamation", nm->compile_id(), nm);
431 }
432 nm->mark_for_reclamation();
433 _resweep = true;
434 _marked_count++;
435 SWEEP(nm);
436 }
437 } else if (nm->is_not_entrant()) {
438 // If there is no current activations of this method on the
439 // stack we can safely convert it to a zombie method
440 if (nm->can_not_entrant_be_converted()) {
441 if (PrintMethodFlushing && Verbose) {
442 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (not entrant) being made zombie", nm->compile_id(), nm);
443 }
444 nm->make_zombie();
445 _resweep = true;
446 _zombified_count++;
447 SWEEP(nm);
448 } else {
449 // Still alive, clean up its inline caches
450 MutexLocker cl(CompiledIC_lock);
451 nm->cleanup_inline_caches();
452 // we coudn't transition this nmethod so don't immediately
453 // request a rescan. If this method stays on the stack for a
454 // long time we don't want to keep rescanning the code cache.
455 _not_entrant_seen_on_stack++;
456 SWEEP(nm);
457 }
458 } else if (nm->is_unloaded()) {
459 // Unloaded code, just make it a zombie
460 if (PrintMethodFlushing && Verbose)
461 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (unloaded) being made zombie", nm->compile_id(), nm);
462
463 if (nm->is_osr_method()) {
464 SWEEP(nm);
465 // No inline caches will ever point to osr methods, so we can just remove it
466 release_nmethod(nm);
467 _flushed_count++;
468 } else {
469 nm->make_zombie();
470 _resweep = true;
471 _zombified_count++;
472 SWEEP(nm);
473 }
474 } else {
475 assert(nm->is_alive(), "should be alive");
476
477 if (UseCodeCacheFlushing) {
478 if (nm->is_speculatively_disconnected() && !nm->is_locked_by_vm() && !nm->is_osr_method() &&
479 (_traversals > _last_flush_traversal_id + 2) && (nm->compile_id() < _highest_marked)) {
480 // This method has not been called since the forced cleanup happened
481 nm->make_not_entrant();
482 }
483 }
484
485 // Clean-up all inline caches that points to zombie/non-reentrant methods
486 MutexLocker cl(CompiledIC_lock);
487 nm->cleanup_inline_caches();
488 SWEEP(nm);
489 }
490 }
491
492 // Code cache unloading: when compilers notice the code cache is getting full,
493 // they will call a vm op that comes here. This code attempts to speculatively
494 // unload the oldest half of the nmethods (based on the compile job id) by
495 // saving the old code in a list in the CodeCache. Then
496 // execution resumes. If a method so marked is not called by the second sweeper
497 // stack traversal after the current one, the nmethod will be marked non-entrant and
498 // got rid of by normal sweeping. If the method is called, the Method*'s
499 // _code field is restored and the Method*/nmethod
500 // go back to their normal state.
501 void NMethodSweeper::handle_full_code_cache(bool is_full) {
502
503 if (is_full) {
504 // Since code cache is full, immediately stop new compiles
505 if (CompileBroker::set_should_compile_new_jobs(CompileBroker::stop_compilation)) {
506 log_sweep("disable_compiler");
507 }
508 }
509
510 // Make sure only one thread can flush
511 // The token is reset after CodeCacheMinimumFlushInterval in scan stacks,
512 // no need to check the timeout here.
513 jint old = Atomic::cmpxchg( 1, &_flush_token, 0 );
514 if (old != 0) {
515 return;
516 }
517
518 VM_HandleFullCodeCache op(is_full);
519 VMThread::execute(&op);
520
521 // resweep again as soon as possible
522 _resweep = true;
523 }
524
525 void NMethodSweeper::speculative_disconnect_nmethods(bool is_full) {
526 // If there was a race in detecting full code cache, only run
527 // one vm op for it or keep the compiler shut off
528
529 jlong disconnect_start_counter = os::elapsed_counter();
530
531 // Traverse the code cache trying to dump the oldest nmethods
532 int curr_max_comp_id = CompileBroker::get_compilation_id();
533 int flush_target = ((curr_max_comp_id - _dead_compile_ids) / CodeCacheFlushingFraction) + _dead_compile_ids;
534
535 log_sweep("start_cleaning");
536
537 nmethod* nm = CodeCache::alive_nmethod(CodeCache::first());
538 jint disconnected = 0;
539 jint made_not_entrant = 0;
540 jint nmethod_count = 0;
541
542 while ((nm != NULL)){
543 int curr_comp_id = nm->compile_id();
544
545 // OSR methods cannot be flushed like this. Also, don't flush native methods
546 // since they are part of the JDK in most cases
547 if (!nm->is_osr_method() && !nm->is_locked_by_vm() && !nm->is_native_method()) {
548
549 // only count methods that can be speculatively disconnected
550 nmethod_count++;
551
552 if (nm->is_in_use() && (curr_comp_id < flush_target)) {
553 if ((nm->method()->code() == nm)) {
554 // This method has not been previously considered for
555 // unloading or it was restored already
556 CodeCache::speculatively_disconnect(nm);
557 disconnected++;
558 } else if (nm->is_speculatively_disconnected()) {
559 // This method was previously considered for preemptive unloading and was not called since then
560 CompilationPolicy::policy()->delay_compilation(nm->method());
561 nm->make_not_entrant();
562 made_not_entrant++;
563 }
564
565 if (curr_comp_id > _highest_marked) {
566 _highest_marked = curr_comp_id;
567 }
568 }
569 }
570 nm = CodeCache::alive_nmethod(CodeCache::next(nm));
571 }
572
573 // remember how many compile_ids wheren't seen last flush.
574 _dead_compile_ids = curr_max_comp_id - nmethod_count;
575
576 log_sweep("stop_cleaning",
577 "disconnected='" UINT32_FORMAT "' made_not_entrant='" UINT32_FORMAT "'",
578 disconnected, made_not_entrant);
579
580 // Shut off compiler. Sweeper will start over with a new stack scan and
581 // traversal cycle and turn it back on if it clears enough space.
582 if (is_full) {
583 _last_full_flush_time = os::javaTimeMillis();
584 }
585
586 jlong disconnect_end_counter = os::elapsed_counter();
587 jlong disconnect_time = disconnect_end_counter - disconnect_start_counter;
588 _total_disconnect_time += disconnect_time;
589 _peak_disconnect_time = MAX2(disconnect_time, _peak_disconnect_time);
590
591 EventCleanCodeCache event(UNTIMED);
592 if (event.should_commit()) {
593 event.set_starttime(disconnect_start_counter);
594 event.set_endtime(disconnect_end_counter);
595 event.set_disconnectedCount(disconnected);
596 event.set_madeNonEntrantCount(made_not_entrant);
597 event.commit();
598 }
599 _number_of_flushes++;
600
601 // After two more traversals the sweeper will get rid of unrestored nmethods
602 _last_flush_traversal_id = _traversals;
603 _resweep = true;
604 #ifdef ASSERT
605
606 if(PrintMethodFlushing && Verbose) {
607 tty->print_cr("### sweeper: unload time: " INT64_FORMAT, (jlong)disconnect_time);
608 }
609 #endif
610 }
611
612
613 // Print out some state information about the current sweep and the
614 // state of the code cache if it's requested.
615 void 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 }
|
110
111 void NMethodSweeper::record_sweep(nmethod* nm, int line) {
112 if (_records != NULL) {
113 _records[_sweep_index].traversal = _traversals;
114 _records[_sweep_index].traversal_mark = nm->_stack_traversal_mark;
115 _records[_sweep_index].invocation = _invocations;
116 _records[_sweep_index].compile_id = nm->compile_id();
117 _records[_sweep_index].kind = nm->compile_kind();
118 _records[_sweep_index].state = nm->_state;
119 _records[_sweep_index].vep = nm->verified_entry_point();
120 _records[_sweep_index].uep = nm->entry_point();
121 _records[_sweep_index].line = line;
122
123 _sweep_index = (_sweep_index + 1) % SweeperLogEntries;
124 }
125 }
126 #else
127 #define SWEEP(nm)
128 #endif
129
130 nmethod* NMethodSweeper::_current = NULL; // Current nmethod
131 long NMethodSweeper::_traversals = 0; // Nof. stack traversals performed
132 int NMethodSweeper::_seen = 0; // Nof. nmethods we have currently processed in current pass of CodeCache
133 int NMethodSweeper::_flushed_count = 0; // Nof. nmethods flushed in current sweep
134 int NMethodSweeper::_zombified_count = 0; // Nof. nmethods made zombie in current sweep
135 int NMethodSweeper::_marked_count = 0; // Nof. nmethods marked for reclaim in current sweep
136
137 volatile int NMethodSweeper::_invocations = 0; // Nof. invocations left until we are completed with this pass
138 volatile int NMethodSweeper::_sweep_started = 0; // Whether a sweep is in progress.
139
140 jint NMethodSweeper::_locked_seen = 0;
141 jint NMethodSweeper::_not_entrant_seen_on_stack = 0;
142 bool NMethodSweeper::_request_mark_phase = false;
143
144 int NMethodSweeper::_total_nof_methods_reclaimed = 0;
145 jlong NMethodSweeper::_total_time_sweeping = 0;
146 jlong NMethodSweeper::_total_time_this_sweep = 0;
147 jlong NMethodSweeper::_peak_sweep_time = 0;
148 jlong NMethodSweeper::_peak_sweep_fraction_time = 0;
149 int NMethodSweeper::_hotness_counter_reset_val = 0;
150
151
152 class MarkActivationClosure: public CodeBlobClosure {
153 public:
154 virtual void do_code_blob(CodeBlob* cb) {
155 if (cb->is_nmethod()) {
156 nmethod* nm = (nmethod*)cb;
157 nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val());
158 // If we see an activation belonging to a non_entrant nmethod, we mark it.
159 if (nm->is_not_entrant()) {
160 nm->mark_as_seen_on_stack();
161 }
162 }
163 }
164 };
165 static MarkActivationClosure mark_activation_closure;
166
167 class SetHotnessClosure: public CodeBlobClosure {
168 public:
169 virtual void do_code_blob(CodeBlob* cb) {
170 if (cb->is_nmethod()) {
171 nmethod* nm = (nmethod*)cb;
172 nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val());
173 }
174 }
175 };
176 static SetHotnessClosure set_hotness_closure;
177
178
179 int NMethodSweeper::hotness_counter_reset_val() {
180 if (_hotness_counter_reset_val == 0) {
181 _hotness_counter_reset_val = (ReservedCodeCacheSize < M) ? 1 : (ReservedCodeCacheSize / M) * 2;
182 }
183 return _hotness_counter_reset_val;
184 }
185 bool NMethodSweeper::sweep_in_progress() {
186 return (_current != NULL);
187 }
188
189 // Scans the stacks of all Java threads and marks activations of not-entrant methods.
190 // No need to synchronize access, since 'mark_active_nmethods' is always executed at a
191 // safepoint.
192 void NMethodSweeper::mark_active_nmethods() {
193 assert(SafepointSynchronize::is_at_safepoint(), "must be executed at a safepoint");
194 // If we do not want to reclaim not-entrant or zombie methods there is no need
195 // to scan stacks
196 if (!MethodFlushing) {
197 return;
198 }
199
200 // Check for restart
201 assert(CodeCache::find_blob_unsafe(_current) == _current, "Sweeper nmethod cached state invalid");
202 if (!sweep_in_progress() && need_marking_phase()) {
203 _seen = 0;
204 _invocations = NmethodSweepFraction;
205 _current = CodeCache::first_nmethod();
206 _traversals += 1;
207 _total_time_this_sweep = 0;
208
209 if (PrintMethodFlushing) {
210 tty->print_cr("### Sweep: stack traversal %d", _traversals);
211 }
212 Threads::nmethods_do(&mark_activation_closure);
213
214 // reset the flags since we started a scan from the beginning.
215 reset_nmethod_marking();
216 _locked_seen = 0;
217 _not_entrant_seen_on_stack = 0;
218 } else {
219 // Only set hotness counter
220 Threads::nmethods_do(&set_hotness_closure);
221 }
222 }
223
224 void NMethodSweeper::possibly_sweep() {
225 assert(JavaThread::current()->thread_state() == _thread_in_vm, "must run in vm mode");
226 if (!MethodFlushing || !sweep_in_progress()) {
227 return;
228 }
229
230 if (_invocations > 0) {
231 // Only one thread at a time will sweep
232 jint old = Atomic::cmpxchg( 1, &_sweep_started, 0 );
233 if (old != 0) {
234 return;
235 }
236 #ifdef ASSERT
237 if (LogSweeper && _records == NULL) {
238 // Create the ring buffer for the logging code
239 _records = NEW_C_HEAP_ARRAY(SweeperRecord, SweeperLogEntries, mtGC);
240 memset(_records, 0, sizeof(SweeperRecord) * SweeperLogEntries);
241 }
242 #endif
243 if (_invocations > 0) {
244 sweep_code_cache();
245 _invocations--;
246 }
247 _sweep_started = 0;
248 }
249 }
250
251 void NMethodSweeper::sweep_code_cache() {
252
253 jlong sweep_start_counter = os::elapsed_counter();
254
255 _flushed_count = 0;
256 _zombified_count = 0;
257 _marked_count = 0;
258
259 if (PrintMethodFlushing && Verbose) {
260 tty->print_cr("### Sweep at %d out of %d. Invocations left: %d", _seen, CodeCache::nof_nmethods(), _invocations);
261 }
262
263 if (!CompileBroker::should_compile_new_jobs()) {
264 // If we have turned off compilations we might as well do full sweeps
265 // in order to reach the clean state faster. Otherwise the sleeping compiler
266 // threads will slow down sweeping.
267 _invocations = 1;
268 }
269
270 // We want to visit all nmethods after NmethodSweepFraction
271 // invocations so divide the remaining number of nmethods by the
272 // remaining number of invocations. This is only an estimate since
273 // the number of nmethods changes during the sweep so the final
274 // stage must iterate until it there are no more nmethods.
275 int todo = (CodeCache::nof_nmethods() - _seen) / _invocations;
276 assert(!SafepointSynchronize::is_at_safepoint(), "should not be in safepoint when we get here");
277 assert(!CodeCache_lock->owned_by_self(), "just checking");
278 int freed_memory = 0;
279 {
280 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
281
282 // The last invocation iterates until there are no more nmethods
283 for (int i = 0; (i < todo || _invocations == 1) && _current != NULL; i++) {
284 if (SafepointSynchronize::is_synchronizing()) { // Safepoint request
285 if (PrintMethodFlushing && Verbose) {
286 tty->print_cr("### Sweep at %d out of %d, invocation: %d, yielding to safepoint", _seen, CodeCache::nof_nmethods(), _invocations);
287 }
288 MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
289
290 assert(Thread::current()->is_Java_thread(), "should be java thread");
291 JavaThread* thread = (JavaThread*)Thread::current();
292 ThreadBlockInVM tbivm(thread);
293 thread->java_suspend_self();
294 }
295 // Since we will give up the CodeCache_lock, always skip ahead
296 // to the next nmethod. Other blobs can be deleted by other
297 // threads but nmethods are only reclaimed by the sweeper.
298 nmethod* next = CodeCache::next_nmethod(_current);
299
300 // Now ready to process nmethod and give up CodeCache_lock
301 {
302 MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
303 freed_memory += process_nmethod(_current);
304 }
305 _seen++;
306 _current = next;
307 }
308 }
309
310 assert(_invocations > 1 || _current == NULL, "must have scanned the whole cache");
311
312 if (!sweep_in_progress() && !need_marking_phase() && (_locked_seen || _not_entrant_seen_on_stack)) {
313 // we've completed a scan without making progress but there were
314 // nmethods we were unable to process either because they were
315 // locked or were still on stack. We don't have to aggressively
316 // clean them up so just stop scanning. We could scan once more
317 // but that complicates the control logic and it's unlikely to
318 // matter much.
319 if (PrintMethodFlushing) {
320 tty->print_cr("### Couldn't make progress on some nmethods so stopping sweep");
321 }
322 }
323
324 jlong sweep_end_counter = os::elapsed_counter();
325 jlong sweep_time = sweep_end_counter - sweep_start_counter;
326 _total_time_sweeping += sweep_time;
327 _total_time_this_sweep += sweep_time;
328 _peak_sweep_fraction_time = MAX2(sweep_time, _peak_sweep_fraction_time);
329 _total_nof_methods_reclaimed += _flushed_count;
330
331 EventSweepCodeCache event(UNTIMED);
332 if (event.should_commit()) {
333 event.set_starttime(sweep_start_counter);
334 event.set_endtime(sweep_end_counter);
335 event.set_sweepIndex(_traversals);
336 event.set_sweepFractionIndex(NmethodSweepFraction - _invocations + 1);
337 event.set_sweptCount(todo);
338 event.set_flushedCount(_flushed_count);
339 event.set_markedCount(_marked_count);
340 event.set_zombifiedCount(_zombified_count);
341 event.commit();
342 }
343
344 #ifdef ASSERT
345 if(PrintMethodFlushing) {
346 tty->print_cr("### sweeper: sweep time(%d): " INT64_FORMAT, _invocations, (jlong)sweep_time);
347 }
348 #endif
349
350 if (_invocations == 1) {
351 _peak_sweep_time = MAX2(_peak_sweep_time, _total_time_this_sweep);
352 log_sweep("finished");
353 }
354
355 // Sweeper is the only case where memory is released, check here if it
356 // is time to restart the compiler. Only checking if there is a certain
357 // amount of free memory in the code cache might lead to re-enabling
358 // compilation although no memory has been released. For example, there are
359 // cases when compilation was disabled although there is 4MB (or more) free
360 // memory in the code cache. The reason is code cache fragmentation. Therefore,
361 // it only makes sense to re-enable compilation if we have actually freed memory.
362 // Note that typically several kB are released for sweeping 16MB of the code
363 // cache. As a result, 'freed_memory' > 0 to restart the compiler.
364 if (UseCodeCacheFlushing && (!CompileBroker::should_compile_new_jobs() && (freed_memory > 0))) {
365 CompileBroker::set_should_compile_new_jobs(CompileBroker::run_compilation);
366 log_sweep("restart_compiler");
367 }
368 }
369
370 class NMethodMarker: public StackObj {
371 private:
372 CompilerThread* _thread;
373 public:
374 NMethodMarker(nmethod* nm) {
375 _thread = CompilerThread::current();
376 if (!nm->is_zombie() && !nm->is_unloaded()) {
377 // Only expose live nmethods for scanning
378 _thread->set_scanned_nmethod(nm);
379 }
380 }
381 ~NMethodMarker() {
382 _thread->set_scanned_nmethod(NULL);
383 }
384 };
385
386 void NMethodSweeper::release_nmethod(nmethod *nm) {
387 // Clean up any CompiledICHolders
388 {
389 ResourceMark rm;
390 MutexLocker ml_patch(CompiledIC_lock);
391 RelocIterator iter(nm);
392 while (iter.next()) {
393 if (iter.type() == relocInfo::virtual_call_type) {
394 CompiledIC::cleanup_call_site(iter.virtual_call_reloc());
395 }
396 }
397 }
398
399 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
400 nm->flush();
401 }
402
403 int NMethodSweeper::process_nmethod(nmethod *nm) {
404 assert(!CodeCache_lock->owned_by_self(), "just checking");
405
406 int freed_memory = 0;
407 // Make sure this nmethod doesn't get unloaded during the scan,
408 // since safepoints may happen during acquired below locks.
409 NMethodMarker nmm(nm);
410 SWEEP(nm);
411
412 // Skip methods that are currently referenced by the VM
413 if (nm->is_locked_by_vm()) {
414 // But still remember to clean-up inline caches for alive nmethods
415 if (nm->is_alive()) {
416 // Clean inline caches that point to zombie/non-entrant methods
417 MutexLocker cl(CompiledIC_lock);
418 nm->cleanup_inline_caches();
419 SWEEP(nm);
420 } else {
421 _locked_seen++;
422 SWEEP(nm);
423 }
424 return freed_memory;
425 }
426
427 if (nm->is_zombie()) {
428 // If it is the first time we see nmethod then we mark it. Otherwise,
429 // we reclaim it. When we have seen a zombie method twice, we know that
430 // there are no inline caches that refer to it.
431 if (nm->is_marked_for_reclamation()) {
432 assert(!nm->is_locked_by_vm(), "must not flush locked nmethods");
433 if (PrintMethodFlushing && Verbose) {
434 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (marked for reclamation) being flushed", nm->compile_id(), nm);
435 }
436 freed_memory = nm->total_size();
437 release_nmethod(nm);
438 _flushed_count++;
439 } else {
440 if (PrintMethodFlushing && Verbose) {
441 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (zombie) being marked for reclamation", nm->compile_id(), nm);
442 }
443 nm->mark_for_reclamation();
444 request_nmethod_marking();
445 _marked_count++;
446 SWEEP(nm);
447 }
448 } else if (nm->is_not_entrant()) {
449 // If there are no current activations of this method on the
450 // stack we can safely convert it to a zombie method
451 if (nm->can_not_entrant_be_converted()) {
452 if (PrintMethodFlushing && Verbose) {
453 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (not entrant) being made zombie", nm->compile_id(), nm);
454 }
455 nm->make_zombie();
456 request_nmethod_marking();
457 _zombified_count++;
458 SWEEP(nm);
459 } else {
460 // Still alive, clean up its inline caches
461 MutexLocker cl(CompiledIC_lock);
462 nm->cleanup_inline_caches();
463 // we coudn't transition this nmethod so don't immediately
464 // request a rescan. If this method stays on the stack for a
465 // long time we don't want to keep rescanning the code cache.
466 _not_entrant_seen_on_stack++;
467 SWEEP(nm);
468 }
469 } else if (nm->is_unloaded()) {
470 // Unloaded code, just make it a zombie
471 if (PrintMethodFlushing && Verbose) {
472 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (unloaded) being made zombie", nm->compile_id(), nm);
473 }
474 if (nm->is_osr_method()) {
475 SWEEP(nm);
476 // No inline caches will ever point to osr methods, so we can just remove it
477 freed_memory = nm->total_size();
478 release_nmethod(nm);
479 _flushed_count++;
480 } else {
481 nm->make_zombie();
482 request_nmethod_marking();
483 _zombified_count++;
484 SWEEP(nm);
485 }
486 } else {
487 if (UseCodeCacheFlushing) {
488 if (!nm->is_locked_by_vm() && !nm->is_osr_method() && !nm->is_native_method()) {
489 // Do not make native methods and OSR-methods not-entrant
490 nm->dec_hotness_counter();
491 // Get the initial value of the hotness counter. This value depends on the
492 // ReservedCodeCacheSize
493 int reset_val = hotness_counter_reset_val();
494 int time_since_reset = reset_val - nm->hotness_counter();
495 double threshold = -reset_val + (CodeCache::reverse_free_ratio() * NmethodSweepActivity);
496 // The less free space in the code cache we have - the bigger reverse_free_ratio() is.
497 // I.e., 'threshold' increases with lower available space in the code cache and a higher
498 // NmethodSweepActivity. If the current hotness counter - which decreases from its initial
499 // value until it is reset by stack walking - is smaller than the computed threshold, the
500 // corresponding nmethod is considered for removal.
501 if ((NmethodSweepActivity > 0) && (nm->hotness_counter() < threshold) && (time_since_reset > 10)) {
502 // A method is marked as not-entrant if the method is
503 // 1) 'old enough': nm->hotness_counter() < threshold
504 // 2) The method was in_use for a minimum amount of time: (time_since_reset > 10)
505 // The second condition is necessary if we are dealing with very small code cache
506 // sizes (e.g., <10m) and the code cache size is too small to hold all hot methods.
507 // The second condition ensures that methods are not immediately made not-entrant
508 // after compilation.
509 nm->make_not_entrant();
510 request_nmethod_marking();
511 }
512 }
513 }
514 // Clean-up all inline caches that point to zombie/non-reentrant methods
515 MutexLocker cl(CompiledIC_lock);
516 nm->cleanup_inline_caches();
517 SWEEP(nm);
518 }
519 return freed_memory;
520 }
521
522 // Print out some state information about the current sweep and the
523 // state of the code cache if it's requested.
524 void NMethodSweeper::log_sweep(const char* msg, const char* format, ...) {
525 if (PrintMethodFlushing) {
526 stringStream s;
527 // Dump code cache state into a buffer before locking the tty,
528 // because log_state() will use locks causing lock conflicts.
529 CodeCache::log_state(&s);
530
531 ttyLocker ttyl;
532 tty->print("### sweeper: %s ", msg);
533 if (format != NULL) {
534 va_list ap;
535 va_start(ap, format);
536 tty->vprint(format, ap);
537 va_end(ap);
538 }
539 tty->print_cr(s.as_string());
540 }
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