1 /*
2 * Copyright (c) 1997, 2016, 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 "logging/log.hpp"
32 #include "logging/logStream.hpp"
33 #include "memory/resourceArea.hpp"
34 #include "oops/method.hpp"
35 #include "runtime/atomic.hpp"
36 #include "runtime/compilationPolicy.hpp"
37 #include "runtime/mutexLocker.hpp"
38 #include "runtime/orderAccess.inline.hpp"
39 #include "runtime/os.hpp"
40 #include "runtime/sweeper.hpp"
41 #include "runtime/thread.inline.hpp"
42 #include "runtime/vm_operations.hpp"
43 #include "trace/tracing.hpp"
44 #include "utilities/events.hpp"
45 #include "utilities/ticks.inline.hpp"
46 #include "utilities/xmlstream.hpp"
47
48 #ifdef ASSERT
49
50 #define SWEEP(nm) record_sweep(nm, __LINE__)
51 // Sweeper logging code
52 class SweeperRecord {
53 public:
54 int traversal;
55 int compile_id;
56 long traversal_mark;
57 int state;
58 const char* kind;
59 address vep;
60 address uep;
61 int line;
62
63 void print() {
64 tty->print_cr("traversal = %d compile_id = %d %s uep = " PTR_FORMAT " vep = "
65 PTR_FORMAT " state = %d traversal_mark %ld line = %d",
66 traversal,
67 compile_id,
68 kind == NULL ? "" : kind,
69 p2i(uep),
70 p2i(vep),
71 state,
72 traversal_mark,
73 line);
74 }
75 };
76
77 static int _sweep_index = 0;
78 static SweeperRecord* _records = NULL;
79
80 void NMethodSweeper::report_events(int id, address entry) {
81 if (_records != NULL) {
82 for (int i = _sweep_index; i < SweeperLogEntries; i++) {
83 if (_records[i].uep == entry ||
84 _records[i].vep == entry ||
85 _records[i].compile_id == id) {
86 _records[i].print();
87 }
88 }
89 for (int i = 0; i < _sweep_index; i++) {
90 if (_records[i].uep == entry ||
91 _records[i].vep == entry ||
92 _records[i].compile_id == id) {
93 _records[i].print();
94 }
95 }
96 }
97 }
98
99 void NMethodSweeper::report_events() {
100 if (_records != NULL) {
101 for (int i = _sweep_index; i < SweeperLogEntries; i++) {
102 // skip empty records
103 if (_records[i].vep == NULL) continue;
104 _records[i].print();
105 }
106 for (int i = 0; i < _sweep_index; i++) {
107 // skip empty records
108 if (_records[i].vep == NULL) continue;
109 _records[i].print();
110 }
111 }
112 }
113
114 void NMethodSweeper::record_sweep(CompiledMethod* nm, int line) {
115 if (_records != NULL) {
116 _records[_sweep_index].traversal = _traversals;
117 _records[_sweep_index].traversal_mark = nm->is_nmethod() ? ((nmethod*)nm)->_stack_traversal_mark : 0;
118 _records[_sweep_index].compile_id = nm->compile_id();
119 _records[_sweep_index].kind = nm->compile_kind();
120 _records[_sweep_index].state = nm->get_state();
121 _records[_sweep_index].vep = nm->verified_entry_point();
122 _records[_sweep_index].uep = nm->entry_point();
123 _records[_sweep_index].line = line;
124 _sweep_index = (_sweep_index + 1) % SweeperLogEntries;
125 }
126 }
127
128 void NMethodSweeper::init_sweeper_log() {
129 if (LogSweeper && _records == NULL) {
130 // Create the ring buffer for the logging code
131 _records = NEW_C_HEAP_ARRAY(SweeperRecord, SweeperLogEntries, mtGC);
132 memset(_records, 0, sizeof(SweeperRecord) * SweeperLogEntries);
133 }
134 }
135 #else
136 #define SWEEP(nm)
137 #endif
138
139 CompiledMethodIterator NMethodSweeper::_current; // Current compiled method
140 long NMethodSweeper::_traversals = 0; // Stack scan count, also sweep ID.
141 long NMethodSweeper::_total_nof_code_cache_sweeps = 0; // Total number of full sweeps of the code cache
142 long NMethodSweeper::_time_counter = 0; // Virtual time used to periodically invoke sweeper
143 long NMethodSweeper::_last_sweep = 0; // Value of _time_counter when the last sweep happened
144 int NMethodSweeper::_seen = 0; // Nof. nmethod we have currently processed in current pass of CodeCache
145
146 volatile bool NMethodSweeper::_should_sweep = true; // Indicates if we should invoke the sweeper
147 volatile bool NMethodSweeper::_force_sweep = false;// Indicates if we should force a sweep
148 volatile int NMethodSweeper::_bytes_changed = 0; // Counts the total nmethod size if the nmethod changed from:
149 // 1) alive -> not_entrant
150 // 2) not_entrant -> zombie
151 int NMethodSweeper::_hotness_counter_reset_val = 0;
152
153 long NMethodSweeper::_total_nof_methods_reclaimed = 0; // Accumulated nof methods flushed
154 long NMethodSweeper::_total_nof_c2_methods_reclaimed = 0; // Accumulated nof methods flushed
155 size_t NMethodSweeper::_total_flushed_size = 0; // Total number of bytes flushed from the code cache
156 Tickspan NMethodSweeper::_total_time_sweeping; // Accumulated time sweeping
157 Tickspan NMethodSweeper::_total_time_this_sweep; // Total time this sweep
158 Tickspan NMethodSweeper::_peak_sweep_time; // Peak time for a full sweep
159 Tickspan NMethodSweeper::_peak_sweep_fraction_time; // Peak time sweeping one fraction
160
161 Monitor* NMethodSweeper::_stat_lock = new Monitor(Mutex::special, "Sweeper::Statistics", true, Monitor::_safepoint_check_sometimes);
162
163 class MarkActivationClosure: public CodeBlobClosure {
164 public:
165 virtual void do_code_blob(CodeBlob* cb) {
166 assert(cb->is_nmethod(), "CodeBlob should be nmethod");
167 nmethod* nm = (nmethod*)cb;
168 nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val());
169 // If we see an activation belonging to a non_entrant nmethod, we mark it.
170 if (nm->is_not_entrant()) {
171 nm->mark_as_seen_on_stack();
172 }
173 }
174 };
175 static MarkActivationClosure mark_activation_closure;
176
177 class SetHotnessClosure: public CodeBlobClosure {
178 public:
179 virtual void do_code_blob(CodeBlob* cb) {
180 assert(cb->is_nmethod(), "CodeBlob should be nmethod");
181 nmethod* nm = (nmethod*)cb;
182 nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val());
183 }
184 };
185 static SetHotnessClosure set_hotness_closure;
186
187
188 int NMethodSweeper::hotness_counter_reset_val() {
189 if (_hotness_counter_reset_val == 0) {
190 _hotness_counter_reset_val = (ReservedCodeCacheSize < M) ? 1 : (ReservedCodeCacheSize / M) * 2;
191 }
192 return _hotness_counter_reset_val;
193 }
194 bool NMethodSweeper::wait_for_stack_scanning() {
195 return _current.end();
196 }
197
198 /**
199 * Scans the stacks of all Java threads and marks activations of not-entrant methods.
200 * No need to synchronize access, since 'mark_active_nmethods' is always executed at a
201 * safepoint.
202 */
203 void NMethodSweeper::mark_active_nmethods() {
204 assert(SafepointSynchronize::is_at_safepoint(), "must be executed at a safepoint");
205 // If we do not want to reclaim not-entrant or zombie methods there is no need
206 // to scan stacks
207 if (!MethodFlushing) {
208 return;
209 }
210
211 // Increase time so that we can estimate when to invoke the sweeper again.
212 _time_counter++;
213
214 // Check for restart
215 if (_current.method() != NULL) {
216 if (_current.method()->is_nmethod()) {
217 assert(CodeCache::find_blob_unsafe(_current.method()) == _current.method(), "Sweeper nmethod cached state invalid");
218 } else if (_current.method()->is_aot()) {
219 assert(CodeCache::find_blob_unsafe(_current.method()->code_begin()) == _current.method(), "Sweeper AOT method cached state invalid");
220 } else {
221 ShouldNotReachHere();
222 }
223 }
224
225 if (wait_for_stack_scanning()) {
226 _seen = 0;
227 _current = CompiledMethodIterator();
228 // Initialize to first nmethod
229 _current.next();
230 _traversals += 1;
231 _total_time_this_sweep = Tickspan();
232
233 if (PrintMethodFlushing) {
234 tty->print_cr("### Sweep: stack traversal %ld", _traversals);
235 }
236 Threads::nmethods_do(&mark_activation_closure);
237
238 } else {
239 // Only set hotness counter
240 Threads::nmethods_do(&set_hotness_closure);
241 }
242
243 OrderAccess::storestore();
244 }
245
246 /**
247 * This function triggers a VM operation that does stack scanning of active
248 * methods. Stack scanning is mandatory for the sweeper to make progress.
249 */
250 void NMethodSweeper::do_stack_scanning() {
251 assert(!CodeCache_lock->owned_by_self(), "just checking");
252 if (wait_for_stack_scanning()) {
253 VM_MarkActiveNMethods op;
254 VMThread::execute(&op);
255 _should_sweep = true;
256 }
257 }
258
259 void NMethodSweeper::sweeper_loop() {
260 bool timeout;
261 while (true) {
262 {
263 ThreadBlockInVM tbivm(JavaThread::current());
264 MutexLockerEx waiter(CodeCache_lock, Mutex::_no_safepoint_check_flag);
265 const long wait_time = 60*60*24 * 1000;
266 timeout = CodeCache_lock->wait(Mutex::_no_safepoint_check_flag, wait_time);
267 }
268 if (!timeout) {
269 possibly_sweep();
270 }
271 }
272 }
273
274 /**
275 * Wakes up the sweeper thread to possibly sweep.
276 */
277 void NMethodSweeper::notify(int code_blob_type) {
278 // Makes sure that we do not invoke the sweeper too often during startup.
279 double start_threshold = 100.0 / (double)StartAggressiveSweepingAt;
280 double aggressive_sweep_threshold = MIN2(start_threshold, 1.1);
281 if (CodeCache::reverse_free_ratio(code_blob_type) >= aggressive_sweep_threshold) {
282 assert_locked_or_safepoint(CodeCache_lock);
283 CodeCache_lock->notify();
284 }
285 }
286
287 /**
288 * Wakes up the sweeper thread and forces a sweep. Blocks until it finished.
289 */
290 void NMethodSweeper::force_sweep() {
291 ThreadBlockInVM tbivm(JavaThread::current());
292 MutexLockerEx waiter(CodeCache_lock, Mutex::_no_safepoint_check_flag);
293 // Request forced sweep
294 _force_sweep = true;
295 while (_force_sweep) {
296 // Notify sweeper that we want to force a sweep and wait for completion.
297 // In case a sweep currently takes place we timeout and try again because
298 // we want to enforce a full sweep.
299 CodeCache_lock->notify();
300 CodeCache_lock->wait(Mutex::_no_safepoint_check_flag, 1000);
301 }
302 }
303
304 /**
305 * Handle a safepoint request
306 */
307 void NMethodSweeper::handle_safepoint_request() {
308 if (SafepointSynchronize::is_synchronizing()) {
309 if (PrintMethodFlushing && Verbose) {
310 tty->print_cr("### Sweep at %d out of %d, yielding to safepoint", _seen, CodeCache::nmethod_count());
311 }
312 MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
313
314 JavaThread* thread = JavaThread::current();
315 ThreadBlockInVM tbivm(thread);
316 thread->java_suspend_self();
317 }
318 }
319
320 /**
321 * This function invokes the sweeper if at least one of the three conditions is met:
322 * (1) The code cache is getting full
323 * (2) There are sufficient state changes in/since the last sweep.
324 * (3) We have not been sweeping for 'some time'
325 */
326 void NMethodSweeper::possibly_sweep() {
327 assert(JavaThread::current()->thread_state() == _thread_in_vm, "must run in vm mode");
328 // If there was no state change while nmethod sweeping, 'should_sweep' will be false.
329 // This is one of the two places where should_sweep can be set to true. The general
330 // idea is as follows: If there is enough free space in the code cache, there is no
331 // need to invoke the sweeper. The following formula (which determines whether to invoke
332 // the sweeper or not) depends on the assumption that for larger ReservedCodeCacheSizes
333 // we need less frequent sweeps than for smaller ReservedCodecCacheSizes. Furthermore,
334 // the formula considers how much space in the code cache is currently used. Here are
335 // some examples that will (hopefully) help in understanding.
336 //
337 // Small ReservedCodeCacheSizes: (e.g., < 16M) We invoke the sweeper every time, since
338 // the result of the division is 0. This
339 // keeps the used code cache size small
340 // (important for embedded Java)
341 // Large ReservedCodeCacheSize : (e.g., 256M + code cache is 10% full). The formula
342 // computes: (256 / 16) - 1 = 15
343 // As a result, we invoke the sweeper after
344 // 15 invocations of 'mark_active_nmethods.
345 // Large ReservedCodeCacheSize: (e.g., 256M + code Cache is 90% full). The formula
346 // computes: (256 / 16) - 10 = 6.
347 if (!_should_sweep) {
348 const int time_since_last_sweep = _time_counter - _last_sweep;
349 // ReservedCodeCacheSize has an 'unsigned' type. We need a 'signed' type for max_wait_time,
350 // since 'time_since_last_sweep' can be larger than 'max_wait_time'. If that happens using
351 // an unsigned type would cause an underflow (wait_until_next_sweep becomes a large positive
352 // value) that disables the intended periodic sweeps.
353 const int max_wait_time = ReservedCodeCacheSize / (16 * M);
354 double wait_until_next_sweep = max_wait_time - time_since_last_sweep -
355 MAX2(CodeCache::reverse_free_ratio(CodeBlobType::MethodProfiled),
356 CodeCache::reverse_free_ratio(CodeBlobType::MethodNonProfiled));
357 assert(wait_until_next_sweep <= (double)max_wait_time, "Calculation of code cache sweeper interval is incorrect");
358
359 if ((wait_until_next_sweep <= 0.0) || !CompileBroker::should_compile_new_jobs()) {
360 _should_sweep = true;
361 }
362 }
363
364 // Remember if this was a forced sweep
365 bool forced = _force_sweep;
366
367 // Force stack scanning if there is only 10% free space in the code cache.
368 // We force stack scanning only if the non-profiled code heap gets full, since critical
369 // allocations go to the non-profiled heap and we must be make sure that there is
370 // enough space.
371 double free_percent = 1 / CodeCache::reverse_free_ratio(CodeBlobType::MethodNonProfiled) * 100;
372 if (free_percent <= StartAggressiveSweepingAt) {
373 do_stack_scanning();
374 }
375
376 if (_should_sweep || forced) {
377 init_sweeper_log();
378 sweep_code_cache();
379 }
380
381 // We are done with sweeping the code cache once.
382 _total_nof_code_cache_sweeps++;
383 _last_sweep = _time_counter;
384 // Reset flag; temporarily disables sweeper
385 _should_sweep = false;
386 // If there was enough state change, 'possibly_enable_sweeper()'
387 // sets '_should_sweep' to true
388 possibly_enable_sweeper();
389 // Reset _bytes_changed only if there was enough state change. _bytes_changed
390 // can further increase by calls to 'report_state_change'.
391 if (_should_sweep) {
392 _bytes_changed = 0;
393 }
394
395 if (forced) {
396 // Notify requester that forced sweep finished
397 assert(_force_sweep, "Should be a forced sweep");
398 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
399 _force_sweep = false;
400 CodeCache_lock->notify();
401 }
402 }
403
404 void NMethodSweeper::sweep_code_cache() {
405 ResourceMark rm;
406 Ticks sweep_start_counter = Ticks::now();
407
408 log_debug(codecache, sweep, start)("CodeCache flushing");
409
410 int flushed_count = 0;
411 int zombified_count = 0;
412 int flushed_c2_count = 0;
413
414 if (PrintMethodFlushing && Verbose) {
415 tty->print_cr("### Sweep at %d out of %d", _seen, CodeCache::nmethod_count());
416 }
417
418 int swept_count = 0;
419 assert(!SafepointSynchronize::is_at_safepoint(), "should not be in safepoint when we get here");
420 assert(!CodeCache_lock->owned_by_self(), "just checking");
421
422 int freed_memory = 0;
423 {
424 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
425
426 while (!_current.end()) {
427 swept_count++;
428 // Since we will give up the CodeCache_lock, always skip ahead
429 // to the next nmethod. Other blobs can be deleted by other
430 // threads but nmethods are only reclaimed by the sweeper.
431 CompiledMethod* nm = _current.method();
432 _current.next();
433
434 // Now ready to process nmethod and give up CodeCache_lock
435 {
436 MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
437 // Save information before potentially flushing the nmethod
438 // Only flushing nmethods so size only matters for them.
439 int size = nm->is_nmethod() ? ((nmethod*)nm)->total_size() : 0;
440 bool is_c2_method = nm->is_compiled_by_c2();
441 bool is_osr = nm->is_osr_method();
442 int compile_id = nm->compile_id();
443 intptr_t address = p2i(nm);
444 const char* state_before = nm->state();
445 const char* state_after = "";
446
447 MethodStateChange type = process_compiled_method(nm);
448 switch (type) {
449 case Flushed:
450 state_after = "flushed";
451 freed_memory += size;
452 ++flushed_count;
453 if (is_c2_method) {
454 ++flushed_c2_count;
455 }
456 break;
457 case MadeZombie:
458 state_after = "made zombie";
459 ++zombified_count;
460 break;
461 case None:
462 break;
463 default:
464 ShouldNotReachHere();
465 }
466 if (PrintMethodFlushing && Verbose && type != None) {
467 tty->print_cr("### %s nmethod %3d/" PTR_FORMAT " (%s) %s", is_osr ? "osr" : "", compile_id, address, state_before, state_after);
468 }
469 }
470
471 _seen++;
472 handle_safepoint_request();
473 }
474 }
475
476 assert(_current.end(), "must have scanned the whole cache");
477
478 const Ticks sweep_end_counter = Ticks::now();
479 const Tickspan sweep_time = sweep_end_counter - sweep_start_counter;
480 {
481 MutexLockerEx mu(_stat_lock, Mutex::_no_safepoint_check_flag);
482 _total_time_sweeping += sweep_time;
483 _total_time_this_sweep += sweep_time;
484 _peak_sweep_fraction_time = MAX2(sweep_time, _peak_sweep_fraction_time);
485 _total_flushed_size += freed_memory;
486 _total_nof_methods_reclaimed += flushed_count;
487 _total_nof_c2_methods_reclaimed += flushed_c2_count;
488 _peak_sweep_time = MAX2(_peak_sweep_time, _total_time_this_sweep);
489 }
490 EventSweepCodeCache event(UNTIMED);
491 if (event.should_commit()) {
492 event.set_starttime(sweep_start_counter);
493 event.set_endtime(sweep_end_counter);
494 event.set_sweepId(_traversals);
495 event.set_sweptCount(swept_count);
496 event.set_flushedCount(flushed_count);
497 event.set_zombifiedCount(zombified_count);
498 event.commit();
499 }
500
501 #ifdef ASSERT
502 if(PrintMethodFlushing) {
503 tty->print_cr("### sweeper: sweep time(" JLONG_FORMAT "): ", sweep_time.value());
504 }
505 #endif
506
507 Log(codecache, sweep) log;
508 if (log.is_debug()) {
509 LogStream ls(log.debug());
510 CodeCache::print_summary(&ls, false);
511 }
512 log_sweep("finished");
513
514 // Sweeper is the only case where memory is released, check here if it
515 // is time to restart the compiler. Only checking if there is a certain
516 // amount of free memory in the code cache might lead to re-enabling
517 // compilation although no memory has been released. For example, there are
518 // cases when compilation was disabled although there is 4MB (or more) free
519 // memory in the code cache. The reason is code cache fragmentation. Therefore,
520 // it only makes sense to re-enable compilation if we have actually freed memory.
521 // Note that typically several kB are released for sweeping 16MB of the code
522 // cache. As a result, 'freed_memory' > 0 to restart the compiler.
523 if (!CompileBroker::should_compile_new_jobs() && (freed_memory > 0)) {
524 CompileBroker::set_should_compile_new_jobs(CompileBroker::run_compilation);
525 log.debug("restart compiler");
526 log_sweep("restart_compiler");
527 }
528 }
529
530 /**
531 * This function updates the sweeper statistics that keep track of nmethods
532 * state changes. If there is 'enough' state change, the sweeper is invoked
533 * as soon as possible. There can be data races on _bytes_changed. The data
534 * races are benign, since it does not matter if we loose a couple of bytes.
535 * In the worst case we call the sweeper a little later. Also, we are guaranteed
536 * to invoke the sweeper if the code cache gets full.
537 */
538 void NMethodSweeper::report_state_change(nmethod* nm) {
539 _bytes_changed += nm->total_size();
540 possibly_enable_sweeper();
541 }
542
543 /**
544 * Function determines if there was 'enough' state change in the code cache to invoke
545 * the sweeper again. Currently, we determine 'enough' as more than 1% state change in
546 * the code cache since the last sweep.
547 */
548 void NMethodSweeper::possibly_enable_sweeper() {
549 double percent_changed = ((double)_bytes_changed / (double)ReservedCodeCacheSize) * 100;
550 if (percent_changed > 1.0) {
551 _should_sweep = true;
552 }
553 }
554
555 class CompiledMethodMarker: public StackObj {
556 private:
557 CodeCacheSweeperThread* _thread;
558 public:
559 CompiledMethodMarker(CompiledMethod* cm) {
560 JavaThread* current = JavaThread::current();
561 assert (current->is_Code_cache_sweeper_thread(), "Must be");
562 _thread = (CodeCacheSweeperThread*)current;
563 if (!cm->is_zombie() && !cm->is_unloaded()) {
564 // Only expose live nmethods for scanning
565 _thread->set_scanned_compiled_method(cm);
566 }
567 }
568 ~CompiledMethodMarker() {
569 _thread->set_scanned_compiled_method(NULL);
570 }
571 };
572
573 void NMethodSweeper::release_compiled_method(CompiledMethod* nm) {
574 // Make sure the released nmethod is no longer referenced by the sweeper thread
575 CodeCacheSweeperThread* thread = (CodeCacheSweeperThread*)JavaThread::current();
576 thread->set_scanned_compiled_method(NULL);
577
578 // Clean up any CompiledICHolders
579 {
580 ResourceMark rm;
581 MutexLocker ml_patch(CompiledIC_lock);
582 RelocIterator iter(nm);
583 while (iter.next()) {
584 if (iter.type() == relocInfo::virtual_call_type) {
585 CompiledIC::cleanup_call_site(iter.virtual_call_reloc(), nm);
586 }
587 }
588 }
589
590 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
591 nm->flush();
592 }
593
594 NMethodSweeper::MethodStateChange NMethodSweeper::process_compiled_method(CompiledMethod* cm) {
595 assert(cm != NULL, "sanity");
596 assert(!CodeCache_lock->owned_by_self(), "just checking");
597
598 MethodStateChange result = None;
599 // Make sure this nmethod doesn't get unloaded during the scan,
600 // since safepoints may happen during acquired below locks.
601 CompiledMethodMarker nmm(cm);
602 SWEEP(cm);
603
604 // Skip methods that are currently referenced by the VM
605 if (cm->is_locked_by_vm()) {
606 // But still remember to clean-up inline caches for alive nmethods
607 if (cm->is_alive()) {
608 // Clean inline caches that point to zombie/non-entrant/unloaded nmethods
609 MutexLocker cl(CompiledIC_lock);
610 cm->cleanup_inline_caches();
611 SWEEP(cm);
612 }
613 return result;
614 }
615
616 if (cm->is_zombie()) {
617 // All inline caches that referred to this nmethod were cleaned in the
618 // previous sweeper cycle. Now flush the nmethod from the code cache.
619 assert(!cm->is_locked_by_vm(), "must not flush locked Compiled Methods");
620 release_compiled_method(cm);
621 assert(result == None, "sanity");
622 result = Flushed;
623 } else if (cm->is_not_entrant()) {
624 // If there are no current activations of this method on the
625 // stack we can safely convert it to a zombie method
626 if (cm->can_convert_to_zombie()) {
627 // Clear ICStubs to prevent back patching stubs of zombie or flushed
628 // nmethods during the next safepoint (see ICStub::finalize).
629 {
630 MutexLocker cl(CompiledIC_lock);
631 cm->clear_ic_stubs();
632 }
633 // Code cache state change is tracked in make_zombie()
634 cm->make_zombie();
635 SWEEP(cm);
636 // The nmethod may have been locked by JVMTI after being made zombie (see
637 // JvmtiDeferredEvent::compiled_method_unload_event()). If so, we cannot
638 // flush the osr nmethod directly but have to wait for a later sweeper cycle.
639 if (cm->is_osr_method() && !cm->is_locked_by_vm()) {
640 // No inline caches will ever point to osr methods, so we can just remove it.
641 // Make sure that we unregistered the nmethod with the heap and flushed all
642 // dependencies before removing the nmethod (done in make_zombie()).
643 assert(cm->is_zombie(), "nmethod must be unregistered");
644 release_compiled_method(cm);
645 assert(result == None, "sanity");
646 result = Flushed;
647 } else {
648 assert(result == None, "sanity");
649 result = MadeZombie;
650 assert(cm->is_zombie(), "nmethod must be zombie");
651 }
652 } else {
653 // Still alive, clean up its inline caches
654 MutexLocker cl(CompiledIC_lock);
655 cm->cleanup_inline_caches();
656 SWEEP(cm);
657 }
658 } else if (cm->is_unloaded()) {
659 // Code is unloaded, so there are no activations on the stack.
660 // Convert the nmethod to zombie or flush it directly in the OSR case.
661 {
662 // Clean ICs of unloaded nmethods as well because they may reference other
663 // unloaded nmethods that may be flushed earlier in the sweeper cycle.
664 MutexLocker cl(CompiledIC_lock);
665 cm->cleanup_inline_caches();
666 }
667 if (cm->is_osr_method()) {
668 SWEEP(cm);
669 // No inline caches will ever point to osr methods, so we can just remove it
670 release_compiled_method(cm);
671 assert(result == None, "sanity");
672 result = Flushed;
673 } else {
674 // Code cache state change is tracked in make_zombie()
675 cm->make_zombie();
676 SWEEP(cm);
677 assert(result == None, "sanity");
678 result = MadeZombie;
679 }
680 } else {
681 if (cm->is_nmethod()) {
682 possibly_flush((nmethod*)cm);
683 }
684 // Clean inline caches that point to zombie/non-entrant/unloaded nmethods
685 MutexLocker cl(CompiledIC_lock);
686 cm->cleanup_inline_caches();
687 SWEEP(cm);
688 }
689 return result;
690 }
691
692
693 void NMethodSweeper::possibly_flush(nmethod* nm) {
694 if (UseCodeCacheFlushing) {
695 if (!nm->is_locked_by_vm() && !nm->is_native_method()) {
696 bool make_not_entrant = false;
697
698 // Do not make native methods not-entrant
699 nm->dec_hotness_counter();
700 // Get the initial value of the hotness counter. This value depends on the
701 // ReservedCodeCacheSize
702 int reset_val = hotness_counter_reset_val();
703 int time_since_reset = reset_val - nm->hotness_counter();
704 int code_blob_type = CodeCache::get_code_blob_type(nm);
705 double threshold = -reset_val + (CodeCache::reverse_free_ratio(code_blob_type) * NmethodSweepActivity);
706 // The less free space in the code cache we have - the bigger reverse_free_ratio() is.
707 // I.e., 'threshold' increases with lower available space in the code cache and a higher
708 // NmethodSweepActivity. If the current hotness counter - which decreases from its initial
709 // value until it is reset by stack walking - is smaller than the computed threshold, the
710 // corresponding nmethod is considered for removal.
711 if ((NmethodSweepActivity > 0) && (nm->hotness_counter() < threshold) && (time_since_reset > MinPassesBeforeFlush)) {
712 // A method is marked as not-entrant if the method is
713 // 1) 'old enough': nm->hotness_counter() < threshold
714 // 2) The method was in_use for a minimum amount of time: (time_since_reset > MinPassesBeforeFlush)
715 // The second condition is necessary if we are dealing with very small code cache
716 // sizes (e.g., <10m) and the code cache size is too small to hold all hot methods.
717 // The second condition ensures that methods are not immediately made not-entrant
718 // after compilation.
719 make_not_entrant = true;
720 }
721
722 // The stack-scanning low-cost detection may not see the method was used (which can happen for
723 // flat profiles). Check the age counter for possible data.
724 if (UseCodeAging && make_not_entrant && (nm->is_compiled_by_c2() || nm->is_compiled_by_c1())) {
725 MethodCounters* mc = nm->method()->get_method_counters(Thread::current());
726 if (mc != NULL) {
727 // Snapshot the value as it's changed concurrently
728 int age = mc->nmethod_age();
729 if (MethodCounters::is_nmethod_hot(age)) {
730 // The method has gone through flushing, and it became relatively hot that it deopted
731 // before we could take a look at it. Give it more time to appear in the stack traces,
732 // proportional to the number of deopts.
733 MethodData* md = nm->method()->method_data();
734 if (md != NULL && time_since_reset > (int)(MinPassesBeforeFlush * (md->tenure_traps() + 1))) {
735 // It's been long enough, we still haven't seen it on stack.
736 // Try to flush it, but enable counters the next time.
737 mc->reset_nmethod_age();
738 } else {
739 make_not_entrant = false;
740 }
741 } else if (MethodCounters::is_nmethod_warm(age)) {
742 // Method has counters enabled, and the method was used within
743 // previous MinPassesBeforeFlush sweeps. Reset the counter. Stay in the existing
744 // compiled state.
745 mc->reset_nmethod_age();
746 // delay the next check
747 nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val());
748 make_not_entrant = false;
749 } else if (MethodCounters::is_nmethod_age_unset(age)) {
750 // No counters were used before. Set the counters to the detection
751 // limit value. If the method is going to be used again it will be compiled
752 // with counters that we're going to use for analysis the the next time.
753 mc->reset_nmethod_age();
754 } else {
755 // Method was totally idle for 10 sweeps
756 // The counter already has the initial value, flush it and may be recompile
757 // later with counters
758 }
759 }
760 }
761
762 if (make_not_entrant) {
763 nm->make_not_entrant();
764
765 // Code cache state change is tracked in make_not_entrant()
766 if (PrintMethodFlushing && Verbose) {
767 tty->print_cr("### Nmethod %d/" PTR_FORMAT "made not-entrant: hotness counter %d/%d threshold %f",
768 nm->compile_id(), p2i(nm), nm->hotness_counter(), reset_val, threshold);
769 }
770 }
771 }
772 }
773 }
774
775 // Print out some state information about the current sweep and the
776 // state of the code cache if it's requested.
777 void NMethodSweeper::log_sweep(const char* msg, const char* format, ...) {
778 if (PrintMethodFlushing) {
779 ResourceMark rm;
780 stringStream s;
781 // Dump code cache state into a buffer before locking the tty,
782 // because log_state() will use locks causing lock conflicts.
783 CodeCache::log_state(&s);
784
785 ttyLocker ttyl;
786 tty->print("### sweeper: %s ", msg);
787 if (format != NULL) {
788 va_list ap;
789 va_start(ap, format);
790 tty->vprint(format, ap);
791 va_end(ap);
792 }
793 tty->print_cr("%s", s.as_string());
794 }
795
796 if (LogCompilation && (xtty != NULL)) {
797 ResourceMark rm;
798 stringStream s;
799 // Dump code cache state into a buffer before locking the tty,
800 // because log_state() will use locks causing lock conflicts.
801 CodeCache::log_state(&s);
802
803 ttyLocker ttyl;
804 xtty->begin_elem("sweeper state='%s' traversals='" INTX_FORMAT "' ", msg, (intx)traversal_count());
805 if (format != NULL) {
806 va_list ap;
807 va_start(ap, format);
808 xtty->vprint(format, ap);
809 va_end(ap);
810 }
811 xtty->print("%s", s.as_string());
812 xtty->stamp();
813 xtty->end_elem();
814 }
815 }
816
817 void NMethodSweeper::print() {
818 ttyLocker ttyl;
819 tty->print_cr("Code cache sweeper statistics:");
820 tty->print_cr(" Total sweep time: %1.0lfms", (double)_total_time_sweeping.value()/1000000);
821 tty->print_cr(" Total number of full sweeps: %ld", _total_nof_code_cache_sweeps);
822 tty->print_cr(" Total number of flushed methods: %ld(%ld C2 methods)", _total_nof_methods_reclaimed,
823 _total_nof_c2_methods_reclaimed);
824 tty->print_cr(" Total size of flushed methods: " SIZE_FORMAT "kB", _total_flushed_size/K);
825 }