1 /*
2 * Copyright (c) 1997, 2018, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "code/codeCache.hpp"
27 #include "code/compiledIC.hpp"
28 #include "code/icBuffer.hpp"
29 #include "code/nmethod.hpp"
30 #include "compiler/compileBroker.hpp"
31 #include "jfr/jfrEvents.hpp"
32 #include "logging/log.hpp"
33 #include "logging/logStream.hpp"
34 #include "memory/allocation.inline.hpp"
35 #include "memory/resourceArea.hpp"
36 #include "oops/method.hpp"
37 #include "runtime/atomic.hpp"
38 #include "runtime/compilationPolicy.hpp"
39 #include "runtime/interfaceSupport.inline.hpp"
40 #include "runtime/mutexLocker.hpp"
41 #include "runtime/orderAccess.hpp"
42 #include "runtime/os.hpp"
43 #include "runtime/sweeper.hpp"
44 #include "runtime/thread.inline.hpp"
45 #include "runtime/vm_operations.hpp"
46 #include "runtime/vmThread.hpp"
47 #include "utilities/events.hpp"
48 #include "utilities/xmlstream.hpp"
49
50 #ifdef ASSERT
51
52 #define SWEEP(nm) record_sweep(nm, __LINE__)
53 // Sweeper logging code
54 class SweeperRecord {
55 public:
56 int traversal;
57 int compile_id;
58 long traversal_mark;
59 int state;
60 const char* kind;
61 address vep;
62 address uep;
63 int line;
64
65 void print() {
66 tty->print_cr("traversal = %d compile_id = %d %s uep = " PTR_FORMAT " vep = "
67 PTR_FORMAT " state = %d traversal_mark %ld line = %d",
68 traversal,
69 compile_id,
70 kind == NULL ? "" : kind,
71 p2i(uep),
72 p2i(vep),
73 state,
74 traversal_mark,
75 line);
76 }
77 };
78
79 static int _sweep_index = 0;
80 static SweeperRecord* _records = NULL;
81
82 void NMethodSweeper::report_events(int id, address entry) {
83 if (_records != NULL) {
84 for (int i = _sweep_index; i < SweeperLogEntries; i++) {
85 if (_records[i].uep == entry ||
86 _records[i].vep == entry ||
87 _records[i].compile_id == id) {
88 _records[i].print();
89 }
90 }
91 for (int i = 0; i < _sweep_index; i++) {
92 if (_records[i].uep == entry ||
93 _records[i].vep == entry ||
94 _records[i].compile_id == id) {
95 _records[i].print();
96 }
97 }
98 }
99 }
100
101 void NMethodSweeper::report_events() {
102 if (_records != NULL) {
103 for (int i = _sweep_index; i < SweeperLogEntries; i++) {
104 // skip empty records
105 if (_records[i].vep == NULL) continue;
106 _records[i].print();
107 }
108 for (int i = 0; i < _sweep_index; i++) {
109 // skip empty records
110 if (_records[i].vep == NULL) continue;
111 _records[i].print();
112 }
113 }
114 }
115
116 void NMethodSweeper::record_sweep(CompiledMethod* nm, int line) {
117 if (_records != NULL) {
118 _records[_sweep_index].traversal = _traversals;
119 _records[_sweep_index].traversal_mark = nm->is_nmethod() ? ((nmethod*)nm)->stack_traversal_mark() : 0;
120 _records[_sweep_index].compile_id = nm->compile_id();
121 _records[_sweep_index].kind = nm->compile_kind();
122 _records[_sweep_index].state = nm->get_state();
123 _records[_sweep_index].vep = nm->verified_entry_point();
124 _records[_sweep_index].uep = nm->entry_point();
125 _records[_sweep_index].line = line;
126 _sweep_index = (_sweep_index + 1) % SweeperLogEntries;
127 }
128 }
129
130 void NMethodSweeper::init_sweeper_log() {
131 if (LogSweeper && _records == NULL) {
132 // Create the ring buffer for the logging code
133 _records = NEW_C_HEAP_ARRAY(SweeperRecord, SweeperLogEntries, mtGC);
134 memset(_records, 0, sizeof(SweeperRecord) * SweeperLogEntries);
135 }
136 }
137 #else
138 #define SWEEP(nm)
139 #endif
140
141 CompiledMethodIterator NMethodSweeper::_current; // Current compiled method
142 long NMethodSweeper::_traversals = 0; // Stack scan count, also sweep ID.
143 long NMethodSweeper::_total_nof_code_cache_sweeps = 0; // Total number of full sweeps of the code cache
144 long NMethodSweeper::_time_counter = 0; // Virtual time used to periodically invoke sweeper
145 long NMethodSweeper::_last_sweep = 0; // Value of _time_counter when the last sweep happened
146 int NMethodSweeper::_seen = 0; // Nof. nmethod we have currently processed in current pass of CodeCache
147
148 volatile bool NMethodSweeper::_should_sweep = true; // Indicates if we should invoke the sweeper
149 volatile bool NMethodSweeper::_force_sweep = false;// Indicates if we should force a sweep
150 volatile int NMethodSweeper::_bytes_changed = 0; // Counts the total nmethod size if the nmethod changed from:
151 // 1) alive -> not_entrant
152 // 2) not_entrant -> zombie
153 int NMethodSweeper::_hotness_counter_reset_val = 0;
154
155 long NMethodSweeper::_total_nof_methods_reclaimed = 0; // Accumulated nof methods flushed
156 long NMethodSweeper::_total_nof_c2_methods_reclaimed = 0; // Accumulated nof methods flushed
157 size_t NMethodSweeper::_total_flushed_size = 0; // Total number of bytes flushed from the code cache
158 Tickspan NMethodSweeper::_total_time_sweeping; // Accumulated time sweeping
159 Tickspan NMethodSweeper::_total_time_this_sweep; // Total time this sweep
160 Tickspan NMethodSweeper::_peak_sweep_time; // Peak time for a full sweep
161 Tickspan NMethodSweeper::_peak_sweep_fraction_time; // Peak time sweeping one fraction
162
163 Monitor* NMethodSweeper::_stat_lock = new Monitor(Mutex::special, "Sweeper::Statistics", true, Monitor::_safepoint_check_sometimes);
164
165 class MarkActivationClosure: public CodeBlobClosure {
166 public:
167 virtual void do_code_blob(CodeBlob* cb) {
168 assert(cb->is_nmethod(), "CodeBlob should be nmethod");
169 nmethod* nm = (nmethod*)cb;
170 nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val());
171 // If we see an activation belonging to a non_entrant nmethod, we mark it.
172 if (nm->is_not_entrant()) {
173 nm->mark_as_seen_on_stack();
174 }
175 }
176 };
177 static MarkActivationClosure mark_activation_closure;
178
179 class SetHotnessClosure: public CodeBlobClosure {
180 public:
181 virtual void do_code_blob(CodeBlob* cb) {
182 assert(cb->is_nmethod(), "CodeBlob should be nmethod");
183 nmethod* nm = (nmethod*)cb;
184 nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val());
185 }
186 };
187 static SetHotnessClosure set_hotness_closure;
188
189
190 int NMethodSweeper::hotness_counter_reset_val() {
191 if (_hotness_counter_reset_val == 0) {
192 _hotness_counter_reset_val = (ReservedCodeCacheSize < M) ? 1 : (ReservedCodeCacheSize / M) * 2;
193 }
194 return _hotness_counter_reset_val;
195 }
196 bool NMethodSweeper::wait_for_stack_scanning() {
197 return _current.end();
198 }
199
200 /**
201 * Scans the stacks of all Java threads and marks activations of not-entrant methods.
202 * No need to synchronize access, since 'mark_active_nmethods' is always executed at a
203 * safepoint.
204 */
205 void NMethodSweeper::mark_active_nmethods() {
206 CodeBlobClosure* cl = prepare_mark_active_nmethods();
207 if (cl != NULL) {
208 Threads::nmethods_do(cl);
209 }
210 }
211
212 CodeBlobClosure* NMethodSweeper::prepare_mark_active_nmethods() {
213 assert(SafepointSynchronize::is_at_safepoint(), "must be executed at a safepoint");
214 // If we do not want to reclaim not-entrant or zombie methods there is no need
215 // to scan stacks
216 if (!MethodFlushing) {
217 return NULL;
218 }
219
220 // Increase time so that we can estimate when to invoke the sweeper again.
221 _time_counter++;
222
223 // Check for restart
224 if (_current.method() != NULL) {
225 if (_current.method()->is_nmethod()) {
226 assert(CodeCache::find_blob_unsafe(_current.method()) == _current.method(), "Sweeper nmethod cached state invalid");
227 } else if (_current.method()->is_aot()) {
228 assert(CodeCache::find_blob_unsafe(_current.method()->code_begin()) == _current.method(), "Sweeper AOT method cached state invalid");
229 } else {
230 ShouldNotReachHere();
231 }
232 }
233
234 if (wait_for_stack_scanning()) {
235 _seen = 0;
236 _current = CompiledMethodIterator();
237 // Initialize to first nmethod
238 _current.next();
239 _traversals += 1;
240 _total_time_this_sweep = Tickspan();
241
242 if (PrintMethodFlushing) {
243 tty->print_cr("### Sweep: stack traversal %ld", _traversals);
244 }
245 return &mark_activation_closure;
246
247 } else {
248 // Only set hotness counter
249 return &set_hotness_closure;
250 }
251
252 }
253
254 /**
255 * This function triggers a VM operation that does stack scanning of active
256 * methods. Stack scanning is mandatory for the sweeper to make progress.
257 */
258 void NMethodSweeper::do_stack_scanning() {
259 assert(!CodeCache_lock->owned_by_self(), "just checking");
260 if (wait_for_stack_scanning()) {
261 VM_MarkActiveNMethods op;
262 VMThread::execute(&op);
263 _should_sweep = true;
264 }
265 }
266
267 void NMethodSweeper::sweeper_loop() {
268 bool timeout;
269 while (true) {
270 {
271 ThreadBlockInVM tbivm(JavaThread::current());
272 MutexLockerEx waiter(CodeCache_lock, Mutex::_no_safepoint_check_flag);
273 const long wait_time = 60*60*24 * 1000;
274 timeout = CodeCache_lock->wait(Mutex::_no_safepoint_check_flag, wait_time);
275 }
276 if (!timeout) {
277 possibly_sweep();
278 }
279 }
280 }
281
282 /**
283 * Wakes up the sweeper thread to possibly sweep.
284 */
285 void NMethodSweeper::notify(int code_blob_type) {
286 // Makes sure that we do not invoke the sweeper too often during startup.
287 double start_threshold = 100.0 / (double)StartAggressiveSweepingAt;
288 double aggressive_sweep_threshold = MIN2(start_threshold, 1.1);
289 if (CodeCache::reverse_free_ratio(code_blob_type) >= aggressive_sweep_threshold) {
290 assert_locked_or_safepoint(CodeCache_lock);
291 CodeCache_lock->notify();
292 }
293 }
294
295 /**
296 * Wakes up the sweeper thread and forces a sweep. Blocks until it finished.
297 */
298 void NMethodSweeper::force_sweep() {
299 ThreadBlockInVM tbivm(JavaThread::current());
300 MutexLockerEx waiter(CodeCache_lock, Mutex::_no_safepoint_check_flag);
301 // Request forced sweep
302 _force_sweep = true;
303 while (_force_sweep) {
304 // Notify sweeper that we want to force a sweep and wait for completion.
305 // In case a sweep currently takes place we timeout and try again because
306 // we want to enforce a full sweep.
307 CodeCache_lock->notify();
308 CodeCache_lock->wait(Mutex::_no_safepoint_check_flag, 1000);
309 }
310 }
311
312 /**
313 * Handle a safepoint request
314 */
315 void NMethodSweeper::handle_safepoint_request() {
316 if (SafepointSynchronize::is_synchronizing()) {
317 if (PrintMethodFlushing && Verbose) {
318 tty->print_cr("### Sweep at %d out of %d, yielding to safepoint", _seen, CodeCache::nmethod_count());
319 }
320 MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
321
322 JavaThread* thread = JavaThread::current();
323 ThreadBlockInVM tbivm(thread);
324 thread->java_suspend_self();
325 }
326 }
327
328 /**
329 * This function invokes the sweeper if at least one of the three conditions is met:
330 * (1) The code cache is getting full
331 * (2) There are sufficient state changes in/since the last sweep.
332 * (3) We have not been sweeping for 'some time'
333 */
334 void NMethodSweeper::possibly_sweep() {
335 assert(JavaThread::current()->thread_state() == _thread_in_vm, "must run in vm mode");
336 // If there was no state change while nmethod sweeping, 'should_sweep' will be false.
337 // This is one of the two places where should_sweep can be set to true. The general
338 // idea is as follows: If there is enough free space in the code cache, there is no
339 // need to invoke the sweeper. The following formula (which determines whether to invoke
340 // the sweeper or not) depends on the assumption that for larger ReservedCodeCacheSizes
341 // we need less frequent sweeps than for smaller ReservedCodecCacheSizes. Furthermore,
342 // the formula considers how much space in the code cache is currently used. Here are
343 // some examples that will (hopefully) help in understanding.
344 //
345 // Small ReservedCodeCacheSizes: (e.g., < 16M) We invoke the sweeper every time, since
346 // the result of the division is 0. This
347 // keeps the used code cache size small
348 // (important for embedded Java)
349 // Large ReservedCodeCacheSize : (e.g., 256M + code cache is 10% full). The formula
350 // computes: (256 / 16) - 1 = 15
351 // As a result, we invoke the sweeper after
352 // 15 invocations of 'mark_active_nmethods.
353 // Large ReservedCodeCacheSize: (e.g., 256M + code Cache is 90% full). The formula
354 // computes: (256 / 16) - 10 = 6.
355 if (!_should_sweep) {
356 const int time_since_last_sweep = _time_counter - _last_sweep;
357 // ReservedCodeCacheSize has an 'unsigned' type. We need a 'signed' type for max_wait_time,
358 // since 'time_since_last_sweep' can be larger than 'max_wait_time'. If that happens using
359 // an unsigned type would cause an underflow (wait_until_next_sweep becomes a large positive
360 // value) that disables the intended periodic sweeps.
361 const int max_wait_time = ReservedCodeCacheSize / (16 * M);
362 double wait_until_next_sweep = max_wait_time - time_since_last_sweep -
363 MAX2(CodeCache::reverse_free_ratio(CodeBlobType::MethodProfiled),
364 CodeCache::reverse_free_ratio(CodeBlobType::MethodNonProfiled));
365 assert(wait_until_next_sweep <= (double)max_wait_time, "Calculation of code cache sweeper interval is incorrect");
366
367 if ((wait_until_next_sweep <= 0.0) || !CompileBroker::should_compile_new_jobs()) {
368 _should_sweep = true;
369 }
370 }
371
372 // Remember if this was a forced sweep
373 bool forced = _force_sweep;
374
375 // Force stack scanning if there is only 10% free space in the code cache.
376 // We force stack scanning only if the non-profiled code heap gets full, since critical
377 // allocations go to the non-profiled heap and we must be make sure that there is
378 // enough space.
379 double free_percent = 1 / CodeCache::reverse_free_ratio(CodeBlobType::MethodNonProfiled) * 100;
380 if (free_percent <= StartAggressiveSweepingAt) {
381 do_stack_scanning();
382 }
383
384 if (_should_sweep || forced) {
385 init_sweeper_log();
386 sweep_code_cache();
387 }
388
389 // We are done with sweeping the code cache once.
390 _total_nof_code_cache_sweeps++;
391 _last_sweep = _time_counter;
392 // Reset flag; temporarily disables sweeper
393 _should_sweep = false;
394 // If there was enough state change, 'possibly_enable_sweeper()'
395 // sets '_should_sweep' to true
396 possibly_enable_sweeper();
397 // Reset _bytes_changed only if there was enough state change. _bytes_changed
398 // can further increase by calls to 'report_state_change'.
399 if (_should_sweep) {
400 _bytes_changed = 0;
401 }
402
403 if (forced) {
404 // Notify requester that forced sweep finished
405 assert(_force_sweep, "Should be a forced sweep");
406 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
407 _force_sweep = false;
408 CodeCache_lock->notify();
409 }
410 }
411
412 static void post_sweep_event(EventSweepCodeCache* event,
413 const Ticks& start,
414 const Ticks& end,
415 s4 traversals,
416 int swept,
417 int flushed,
418 int zombified) {
419 assert(event != NULL, "invariant");
420 assert(event->should_commit(), "invariant");
421 event->set_starttime(start);
422 event->set_endtime(end);
423 event->set_sweepId(traversals);
424 event->set_sweptCount(swept);
425 event->set_flushedCount(flushed);
426 event->set_zombifiedCount(zombified);
427 event->commit();
428 }
429
430 void NMethodSweeper::sweep_code_cache() {
431 ResourceMark rm;
432 Ticks sweep_start_counter = Ticks::now();
433
434 log_debug(codecache, sweep, start)("CodeCache flushing");
435
436 int flushed_count = 0;
437 int zombified_count = 0;
438 int flushed_c2_count = 0;
439
440 if (PrintMethodFlushing && Verbose) {
441 tty->print_cr("### Sweep at %d out of %d", _seen, CodeCache::nmethod_count());
442 }
443
444 int swept_count = 0;
445 assert(!SafepointSynchronize::is_at_safepoint(), "should not be in safepoint when we get here");
446 assert(!CodeCache_lock->owned_by_self(), "just checking");
447
448 int freed_memory = 0;
449 {
450 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
451
452 while (!_current.end()) {
453 swept_count++;
454 // Since we will give up the CodeCache_lock, always skip ahead
455 // to the next nmethod. Other blobs can be deleted by other
456 // threads but nmethods are only reclaimed by the sweeper.
457 CompiledMethod* nm = _current.method();
458 _current.next();
459
460 // Now ready to process nmethod and give up CodeCache_lock
461 {
462 MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
463 // Save information before potentially flushing the nmethod
464 // Only flushing nmethods so size only matters for them.
465 int size = nm->is_nmethod() ? ((nmethod*)nm)->total_size() : 0;
466 bool is_c2_method = nm->is_compiled_by_c2();
467 bool is_osr = nm->is_osr_method();
468 int compile_id = nm->compile_id();
469 intptr_t address = p2i(nm);
470 const char* state_before = nm->state();
471 const char* state_after = "";
472
473 MethodStateChange type = process_compiled_method(nm);
474 switch (type) {
475 case Flushed:
476 state_after = "flushed";
477 freed_memory += size;
478 ++flushed_count;
479 if (is_c2_method) {
480 ++flushed_c2_count;
481 }
482 break;
483 case MadeZombie:
484 state_after = "made zombie";
485 ++zombified_count;
486 break;
487 case None:
488 break;
489 default:
490 ShouldNotReachHere();
491 }
492 if (PrintMethodFlushing && Verbose && type != None) {
493 tty->print_cr("### %s nmethod %3d/" PTR_FORMAT " (%s) %s", is_osr ? "osr" : "", compile_id, address, state_before, state_after);
494 }
495 }
496
497 _seen++;
498 handle_safepoint_request();
499 }
500 }
501
502 assert(_current.end(), "must have scanned the whole cache");
503
504 const Ticks sweep_end_counter = Ticks::now();
505 const Tickspan sweep_time = sweep_end_counter - sweep_start_counter;
506 {
507 MutexLockerEx mu(_stat_lock, Mutex::_no_safepoint_check_flag);
508 _total_time_sweeping += sweep_time;
509 _total_time_this_sweep += sweep_time;
510 _peak_sweep_fraction_time = MAX2(sweep_time, _peak_sweep_fraction_time);
511 _total_flushed_size += freed_memory;
512 _total_nof_methods_reclaimed += flushed_count;
513 _total_nof_c2_methods_reclaimed += flushed_c2_count;
514 _peak_sweep_time = MAX2(_peak_sweep_time, _total_time_this_sweep);
515 }
516
517 EventSweepCodeCache event(UNTIMED);
518 if (event.should_commit()) {
519 post_sweep_event(&event, sweep_start_counter, sweep_end_counter, (s4)_traversals, swept_count, flushed_count, zombified_count);
520 }
521
522 #ifdef ASSERT
523 if(PrintMethodFlushing) {
524 tty->print_cr("### sweeper: sweep time(" JLONG_FORMAT "): ", sweep_time.value());
525 }
526 #endif
527
528 Log(codecache, sweep) log;
529 if (log.is_debug()) {
530 LogStream ls(log.debug());
531 CodeCache::print_summary(&ls, false);
532 }
533 log_sweep("finished");
534
535 // Sweeper is the only case where memory is released, check here if it
536 // is time to restart the compiler. Only checking if there is a certain
537 // amount of free memory in the code cache might lead to re-enabling
538 // compilation although no memory has been released. For example, there are
539 // cases when compilation was disabled although there is 4MB (or more) free
540 // memory in the code cache. The reason is code cache fragmentation. Therefore,
541 // it only makes sense to re-enable compilation if we have actually freed memory.
542 // Note that typically several kB are released for sweeping 16MB of the code
543 // cache. As a result, 'freed_memory' > 0 to restart the compiler.
544 if (!CompileBroker::should_compile_new_jobs() && (freed_memory > 0)) {
545 CompileBroker::set_should_compile_new_jobs(CompileBroker::run_compilation);
546 log.debug("restart compiler");
547 log_sweep("restart_compiler");
548 }
549 }
550
551 /**
552 * This function updates the sweeper statistics that keep track of nmethods
553 * state changes. If there is 'enough' state change, the sweeper is invoked
554 * as soon as possible. There can be data races on _bytes_changed. The data
555 * races are benign, since it does not matter if we loose a couple of bytes.
556 * In the worst case we call the sweeper a little later. Also, we are guaranteed
557 * to invoke the sweeper if the code cache gets full.
558 */
559 void NMethodSweeper::report_state_change(nmethod* nm) {
560 _bytes_changed += nm->total_size();
561 possibly_enable_sweeper();
562 }
563
564 /**
565 * Function determines if there was 'enough' state change in the code cache to invoke
566 * the sweeper again. Currently, we determine 'enough' as more than 1% state change in
567 * the code cache since the last sweep.
568 */
569 void NMethodSweeper::possibly_enable_sweeper() {
570 double percent_changed = ((double)_bytes_changed / (double)ReservedCodeCacheSize) * 100;
571 if (percent_changed > 1.0) {
572 _should_sweep = true;
573 }
574 }
575
576 class CompiledMethodMarker: public StackObj {
577 private:
578 CodeCacheSweeperThread* _thread;
579 public:
580 CompiledMethodMarker(CompiledMethod* cm) {
581 JavaThread* current = JavaThread::current();
582 assert (current->is_Code_cache_sweeper_thread(), "Must be");
583 _thread = (CodeCacheSweeperThread*)current;
584 if (!cm->is_zombie() && !cm->is_unloaded()) {
585 // Only expose live nmethods for scanning
586 _thread->set_scanned_compiled_method(cm);
587 }
588 }
589 ~CompiledMethodMarker() {
590 _thread->set_scanned_compiled_method(NULL);
591 }
592 };
593
594 void NMethodSweeper::release_compiled_method(CompiledMethod* nm) {
595 // Make sure the released nmethod is no longer referenced by the sweeper thread
596 CodeCacheSweeperThread* thread = (CodeCacheSweeperThread*)JavaThread::current();
597 thread->set_scanned_compiled_method(NULL);
598
599 // Clean up any CompiledICHolders
600 {
601 ResourceMark rm;
602 MutexLocker ml_patch(CompiledIC_lock);
603 RelocIterator iter(nm);
604 while (iter.next()) {
605 if (iter.type() == relocInfo::virtual_call_type) {
606 CompiledIC::cleanup_call_site(iter.virtual_call_reloc(), nm);
607 }
608 }
609 }
610
611 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
612 nm->flush();
613 }
614
615 NMethodSweeper::MethodStateChange NMethodSweeper::process_compiled_method(CompiledMethod* cm) {
616 assert(cm != NULL, "sanity");
617 assert(!CodeCache_lock->owned_by_self(), "just checking");
618
619 MethodStateChange result = None;
620 // Make sure this nmethod doesn't get unloaded during the scan,
621 // since safepoints may happen during acquired below locks.
622 CompiledMethodMarker nmm(cm);
623 SWEEP(cm);
624
625 // Skip methods that are currently referenced by the VM
626 if (cm->is_locked_by_vm()) {
627 // But still remember to clean-up inline caches for alive nmethods
628 if (cm->is_alive()) {
629 // Clean inline caches that point to zombie/non-entrant/unloaded nmethods
630 MutexLocker cl(CompiledIC_lock);
631 cm->cleanup_inline_caches();
632 SWEEP(cm);
633 }
634 return result;
635 }
636
637 if (cm->is_zombie()) {
638 // All inline caches that referred to this nmethod were cleaned in the
639 // previous sweeper cycle. Now flush the nmethod from the code cache.
640 assert(!cm->is_locked_by_vm(), "must not flush locked Compiled Methods");
641 release_compiled_method(cm);
642 assert(result == None, "sanity");
643 result = Flushed;
644 } else if (cm->is_not_entrant()) {
645 // If there are no current activations of this method on the
646 // stack we can safely convert it to a zombie method
647 OrderAccess::loadload(); // _stack_traversal_mark and _state
648 if (cm->can_convert_to_zombie()) {
649 // Clear ICStubs to prevent back patching stubs of zombie or flushed
650 // nmethods during the next safepoint (see ICStub::finalize).
651 {
652 MutexLocker cl(CompiledIC_lock);
653 cm->clear_ic_stubs();
654 }
655 // Code cache state change is tracked in make_zombie()
656 cm->make_zombie();
657 SWEEP(cm);
658 // The nmethod may have been locked by JVMTI after being made zombie (see
659 // JvmtiDeferredEvent::compiled_method_unload_event()). If so, we cannot
660 // flush the osr nmethod directly but have to wait for a later sweeper cycle.
661 if (cm->is_osr_method() && !cm->is_locked_by_vm()) {
662 // No inline caches will ever point to osr methods, so we can just remove it.
663 // Make sure that we unregistered the nmethod with the heap and flushed all
664 // dependencies before removing the nmethod (done in make_zombie()).
665 assert(cm->is_zombie(), "nmethod must be unregistered");
666 release_compiled_method(cm);
667 assert(result == None, "sanity");
668 result = Flushed;
669 } else {
670 assert(result == None, "sanity");
671 result = MadeZombie;
672 assert(cm->is_zombie(), "nmethod must be zombie");
673 }
674 } else {
675 // Still alive, clean up its inline caches
676 MutexLocker cl(CompiledIC_lock);
677 cm->cleanup_inline_caches();
678 SWEEP(cm);
679 }
680 } else if (cm->is_unloaded()) {
681 // Code is unloaded, so there are no activations on the stack.
682 // Convert the nmethod to zombie or flush it directly in the OSR case.
683 {
684 // Clean ICs of unloaded nmethods as well because they may reference other
685 // unloaded nmethods that may be flushed earlier in the sweeper cycle.
686 MutexLocker cl(CompiledIC_lock);
687 cm->cleanup_inline_caches();
688 }
689 if (cm->is_osr_method()) {
690 SWEEP(cm);
691 // No inline caches will ever point to osr methods, so we can just remove it
692 release_compiled_method(cm);
693 assert(result == None, "sanity");
694 result = Flushed;
695 } else {
696 // Code cache state change is tracked in make_zombie()
697 cm->make_zombie();
698 SWEEP(cm);
699 assert(result == None, "sanity");
700 result = MadeZombie;
701 }
702 } else {
703 if (cm->is_nmethod()) {
704 possibly_flush((nmethod*)cm);
705 }
706 // Clean inline caches that point to zombie/non-entrant/unloaded nmethods
707 MutexLocker cl(CompiledIC_lock);
708 cm->cleanup_inline_caches();
709 SWEEP(cm);
710 }
711 return result;
712 }
713
714
715 void NMethodSweeper::possibly_flush(nmethod* nm) {
716 if (UseCodeCacheFlushing) {
717 if (!nm->is_locked_by_vm() && !nm->is_native_method() && !nm->is_not_installed()) {
718 bool make_not_entrant = false;
719
720 // Do not make native methods not-entrant
721 nm->dec_hotness_counter();
722 // Get the initial value of the hotness counter. This value depends on the
723 // ReservedCodeCacheSize
724 int reset_val = hotness_counter_reset_val();
725 int time_since_reset = reset_val - nm->hotness_counter();
726 int code_blob_type = CodeCache::get_code_blob_type(nm);
727 double threshold = -reset_val + (CodeCache::reverse_free_ratio(code_blob_type) * NmethodSweepActivity);
728 // The less free space in the code cache we have - the bigger reverse_free_ratio() is.
729 // I.e., 'threshold' increases with lower available space in the code cache and a higher
730 // NmethodSweepActivity. If the current hotness counter - which decreases from its initial
731 // value until it is reset by stack walking - is smaller than the computed threshold, the
732 // corresponding nmethod is considered for removal.
733 if ((NmethodSweepActivity > 0) && (nm->hotness_counter() < threshold) && (time_since_reset > MinPassesBeforeFlush)) {
734 // A method is marked as not-entrant if the method is
735 // 1) 'old enough': nm->hotness_counter() < threshold
736 // 2) The method was in_use for a minimum amount of time: (time_since_reset > MinPassesBeforeFlush)
737 // The second condition is necessary if we are dealing with very small code cache
738 // sizes (e.g., <10m) and the code cache size is too small to hold all hot methods.
739 // The second condition ensures that methods are not immediately made not-entrant
740 // after compilation.
741 make_not_entrant = true;
742 }
743
744 // The stack-scanning low-cost detection may not see the method was used (which can happen for
745 // flat profiles). Check the age counter for possible data.
746 if (UseCodeAging && make_not_entrant && (nm->is_compiled_by_c2() || nm->is_compiled_by_c1())) {
747 MethodCounters* mc = nm->method()->get_method_counters(Thread::current());
748 if (mc != NULL) {
749 // Snapshot the value as it's changed concurrently
750 int age = mc->nmethod_age();
751 if (MethodCounters::is_nmethod_hot(age)) {
752 // The method has gone through flushing, and it became relatively hot that it deopted
753 // before we could take a look at it. Give it more time to appear in the stack traces,
754 // proportional to the number of deopts.
755 MethodData* md = nm->method()->method_data();
756 if (md != NULL && time_since_reset > (int)(MinPassesBeforeFlush * (md->tenure_traps() + 1))) {
757 // It's been long enough, we still haven't seen it on stack.
758 // Try to flush it, but enable counters the next time.
759 mc->reset_nmethod_age();
760 } else {
761 make_not_entrant = false;
762 }
763 } else if (MethodCounters::is_nmethod_warm(age)) {
764 // Method has counters enabled, and the method was used within
765 // previous MinPassesBeforeFlush sweeps. Reset the counter. Stay in the existing
766 // compiled state.
767 mc->reset_nmethod_age();
768 // delay the next check
769 nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val());
770 make_not_entrant = false;
771 } else if (MethodCounters::is_nmethod_age_unset(age)) {
772 // No counters were used before. Set the counters to the detection
773 // limit value. If the method is going to be used again it will be compiled
774 // with counters that we're going to use for analysis the the next time.
775 mc->reset_nmethod_age();
776 } else {
777 // Method was totally idle for 10 sweeps
778 // The counter already has the initial value, flush it and may be recompile
779 // later with counters
780 }
781 }
782 }
783
784 if (make_not_entrant) {
785 nm->make_not_entrant();
786
787 // Code cache state change is tracked in make_not_entrant()
788 if (PrintMethodFlushing && Verbose) {
789 tty->print_cr("### Nmethod %d/" PTR_FORMAT "made not-entrant: hotness counter %d/%d threshold %f",
790 nm->compile_id(), p2i(nm), nm->hotness_counter(), reset_val, threshold);
791 }
792 }
793 }
794 }
795 }
796
797 // Print out some state information about the current sweep and the
798 // state of the code cache if it's requested.
799 void NMethodSweeper::log_sweep(const char* msg, const char* format, ...) {
800 if (PrintMethodFlushing) {
801 ResourceMark rm;
802 stringStream s;
803 // Dump code cache state into a buffer before locking the tty,
804 // because log_state() will use locks causing lock conflicts.
805 CodeCache::log_state(&s);
806
807 ttyLocker ttyl;
808 tty->print("### sweeper: %s ", msg);
809 if (format != NULL) {
810 va_list ap;
811 va_start(ap, format);
812 tty->vprint(format, ap);
813 va_end(ap);
814 }
815 tty->print_cr("%s", s.as_string());
816 }
817
818 if (LogCompilation && (xtty != NULL)) {
819 ResourceMark rm;
820 stringStream s;
821 // Dump code cache state into a buffer before locking the tty,
822 // because log_state() will use locks causing lock conflicts.
823 CodeCache::log_state(&s);
824
825 ttyLocker ttyl;
826 xtty->begin_elem("sweeper state='%s' traversals='" INTX_FORMAT "' ", msg, (intx)traversal_count());
827 if (format != NULL) {
828 va_list ap;
829 va_start(ap, format);
830 xtty->vprint(format, ap);
831 va_end(ap);
832 }
833 xtty->print("%s", s.as_string());
834 xtty->stamp();
835 xtty->end_elem();
836 }
837 }
838
839 void NMethodSweeper::print(outputStream* out) {
840 ttyLocker ttyl;
841 out = (out == NULL) ? tty : out;
842 out->print_cr("Code cache sweeper statistics:");
843 out->print_cr(" Total sweep time: %1.0lf ms", (double)_total_time_sweeping.value()/1000000);
844 out->print_cr(" Total number of full sweeps: %ld", _total_nof_code_cache_sweeps);
845 out->print_cr(" Total number of flushed methods: %ld (thereof %ld C2 methods)", _total_nof_methods_reclaimed,
846 _total_nof_c2_methods_reclaimed);
847 out->print_cr(" Total size of flushed methods: " SIZE_FORMAT " kB", _total_flushed_size/K);
848 }