1 /*
2 * Copyright (c) 1997, 2014, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "code/codeCache.hpp"
27 #include "code/compiledIC.hpp"
28 #include "code/icBuffer.hpp"
29 #include "code/nmethod.hpp"
30 #include "compiler/compileBroker.hpp"
31 #include "memory/resourceArea.hpp"
32 #include "oops/method.hpp"
33 #include "runtime/atomic.inline.hpp"
34 #include "runtime/compilationPolicy.hpp"
35 #include "runtime/mutexLocker.hpp"
36 #include "runtime/orderAccess.inline.hpp"
37 #include "runtime/os.hpp"
38 #include "runtime/sweeper.hpp"
39 #include "runtime/thread.inline.hpp"
40 #include "runtime/vm_operations.hpp"
41 #include "trace/tracing.hpp"
42 #include "utilities/events.hpp"
43 #include "utilities/ticks.inline.hpp"
44 #include "utilities/xmlstream.hpp"
45
46 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
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 %d line = %d",
66 traversal,
67 compile_id,
68 kind == NULL ? "" : kind,
69 uep,
70 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(nmethod* nm, int line) {
115 if (_records != NULL) {
116 _records[_sweep_index].traversal = _traversals;
117 _records[_sweep_index].traversal_mark = nm->_stack_traversal_mark;
118 _records[_sweep_index].compile_id = nm->compile_id();
119 _records[_sweep_index].kind = nm->compile_kind();
120 _records[_sweep_index].state = nm->_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 NMethodIterator NMethodSweeper::_current; // Current nmethod
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 int NMethodSweeper::_bytes_changed = 0; // Counts the total nmethod size if the nmethod changed from:
148 // 1) alive -> not_entrant
149 // 2) not_entrant -> zombie
150 // 3) zombie -> marked_for_reclamation
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 assert(CodeCache::find_blob_unsafe(_current.method()) == _current.method(), "Sweeper nmethod cached state invalid");
216 if (wait_for_stack_scanning()) {
217 _seen = 0;
218 _current = NMethodIterator();
219 // Initialize to first nmethod
220 _current.next();
221 _traversals += 1;
222 _total_time_this_sweep = Tickspan();
223
224 if (PrintMethodFlushing) {
225 tty->print_cr("### Sweep: stack traversal %d", _traversals);
226 }
227 Threads::nmethods_do(&mark_activation_closure);
228
229 } else {
230 // Only set hotness counter
231 Threads::nmethods_do(&set_hotness_closure);
232 }
233
234 OrderAccess::storestore();
235 }
236
237 /**
238 * This function triggers a VM operation that does stack scanning of active
239 * methods. Stack scanning is mandatory for the sweeper to make progress.
240 */
241 void NMethodSweeper::do_stack_scanning() {
242 assert(!CodeCache_lock->owned_by_self(), "just checking");
243 if (wait_for_stack_scanning()) {
244 VM_MarkActiveNMethods op;
245 VMThread::execute(&op);
246 _should_sweep = true;
247 }
248 }
249
250 void NMethodSweeper::sweeper_loop() {
251 bool timeout;
252 while (true) {
253 {
254 ThreadBlockInVM tbivm(JavaThread::current());
255 MutexLockerEx waiter(CodeCache_lock, Mutex::_no_safepoint_check_flag);
256 const long wait_time = 60*60*24 * 1000;
257 timeout = CodeCache_lock->wait(Mutex::_no_safepoint_check_flag, wait_time);
258 }
259 if (!timeout) {
260 possibly_sweep();
261 }
262 }
263 }
264
265 /**
266 * Wakes up the sweeper thread to possibly sweep.
267 */
268 void NMethodSweeper::notify(int code_blob_type) {
269 // Makes sure that we do not invoke the sweeper too often during startup.
270 double start_threshold = 100.0 / (double)StartAggressiveSweepingAt;
271 double aggressive_sweep_threshold = MIN2(start_threshold, 1.1);
272 if (CodeCache::reverse_free_ratio(code_blob_type) >= aggressive_sweep_threshold) {
273 assert_locked_or_safepoint(CodeCache_lock);
274 CodeCache_lock->notify();
275 }
276 }
277
278 /**
279 * Handle a safepoint request
280 */
281 void NMethodSweeper::handle_safepoint_request() {
282 if (SafepointSynchronize::is_synchronizing()) {
283 if (PrintMethodFlushing && Verbose) {
284 tty->print_cr("### Sweep at %d out of %d, yielding to safepoint", _seen, CodeCache::nof_nmethods());
285 }
286 MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
287
288 JavaThread* thread = JavaThread::current();
289 ThreadBlockInVM tbivm(thread);
290 thread->java_suspend_self();
291 }
292 }
293
294 /**
295 * This function invokes the sweeper if at least one of the three conditions is met:
296 * (1) The code cache is getting full
297 * (2) There are sufficient state changes in/since the last sweep.
298 * (3) We have not been sweeping for 'some time'
299 */
300 void NMethodSweeper::possibly_sweep() {
301 assert(JavaThread::current()->thread_state() == _thread_in_vm, "must run in vm mode");
302 // If there was no state change while nmethod sweeping, 'should_sweep' will be false.
303 // This is one of the two places where should_sweep can be set to true. The general
304 // idea is as follows: If there is enough free space in the code cache, there is no
305 // need to invoke the sweeper. The following formula (which determines whether to invoke
306 // the sweeper or not) depends on the assumption that for larger ReservedCodeCacheSizes
307 // we need less frequent sweeps than for smaller ReservedCodecCacheSizes. Furthermore,
308 // the formula considers how much space in the code cache is currently used. Here are
309 // some examples that will (hopefully) help in understanding.
310 //
311 // Small ReservedCodeCacheSizes: (e.g., < 16M) We invoke the sweeper every time, since
312 // the result of the division is 0. This
313 // keeps the used code cache size small
314 // (important for embedded Java)
315 // Large ReservedCodeCacheSize : (e.g., 256M + code cache is 10% full). The formula
316 // computes: (256 / 16) - 1 = 15
317 // As a result, we invoke the sweeper after
318 // 15 invocations of 'mark_active_nmethods.
319 // Large ReservedCodeCacheSize: (e.g., 256M + code Cache is 90% full). The formula
320 // computes: (256 / 16) - 10 = 6.
321 if (!_should_sweep) {
322 const int time_since_last_sweep = _time_counter - _last_sweep;
323 // ReservedCodeCacheSize has an 'unsigned' type. We need a 'signed' type for max_wait_time,
324 // since 'time_since_last_sweep' can be larger than 'max_wait_time'. If that happens using
325 // an unsigned type would cause an underflow (wait_until_next_sweep becomes a large positive
326 // value) that disables the intended periodic sweeps.
327 const int max_wait_time = ReservedCodeCacheSize / (16 * M);
328 double wait_until_next_sweep = max_wait_time - time_since_last_sweep -
329 MAX2(CodeCache::reverse_free_ratio(CodeBlobType::MethodProfiled),
330 CodeCache::reverse_free_ratio(CodeBlobType::MethodNonProfiled));
331 assert(wait_until_next_sweep <= (double)max_wait_time, "Calculation of code cache sweeper interval is incorrect");
332
333 if ((wait_until_next_sweep <= 0.0) || !CompileBroker::should_compile_new_jobs()) {
334 _should_sweep = true;
335 }
336 }
337
338 // Force stack scanning if there is only 10% free space in the code cache.
339 // We force stack scanning only non-profiled code heap gets full, since critical
340 // allocation go to the non-profiled heap and we must be make sure that there is
341 // enough space.
342 double free_percent = 1 / CodeCache::reverse_free_ratio(CodeBlobType::MethodNonProfiled) * 100;
343 if (free_percent <= StartAggressiveSweepingAt) {
344 do_stack_scanning();
345 }
346
347 if (_should_sweep) {
348 init_sweeper_log();
349 sweep_code_cache();
350 }
351
352 // We are done with sweeping the code cache once.
353 _total_nof_code_cache_sweeps++;
354 _last_sweep = _time_counter;
355 // Reset flag; temporarily disables sweeper
356 _should_sweep = false;
357 // If there was enough state change, 'possibly_enable_sweeper()'
358 // sets '_should_sweep' to true
359 possibly_enable_sweeper();
360 // Reset _bytes_changed only if there was enough state change. _bytes_changed
361 // can further increase by calls to 'report_state_change'.
362 if (_should_sweep) {
363 _bytes_changed = 0;
364 }
365 }
366
367 void NMethodSweeper::sweep_code_cache() {
368 ResourceMark rm;
369 Ticks sweep_start_counter = Ticks::now();
370
371 int flushed_count = 0;
372 int zombified_count = 0;
373 int marked_for_reclamation_count = 0;
374 int flushed_c2_count = 0;
375
376 if (PrintMethodFlushing && Verbose) {
377 tty->print_cr("### Sweep at %d out of %d", _seen, CodeCache::nof_nmethods());
378 }
379
380 int swept_count = 0;
381 assert(!SafepointSynchronize::is_at_safepoint(), "should not be in safepoint when we get here");
382 assert(!CodeCache_lock->owned_by_self(), "just checking");
383
384 int freed_memory = 0;
385 {
386 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
387
388 while (!_current.end()) {
389 swept_count++;
390 // Since we will give up the CodeCache_lock, always skip ahead
391 // to the next nmethod. Other blobs can be deleted by other
392 // threads but nmethods are only reclaimed by the sweeper.
393 nmethod* nm = _current.method();
394 _current.next();
395
396 // Now ready to process nmethod and give up CodeCache_lock
397 {
398 MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
399 int size = nm->total_size();
400 bool is_c2_method = nm->is_compiled_by_c2();
401
402 MethodStateChange type = process_nmethod(nm);
403 switch (type) {
404 case Flushed:
405 freed_memory += size;
406 ++flushed_count;
407 if (is_c2_method) {
408 ++flushed_c2_count;
409 }
410 break;
411 case MarkedForReclamation:
412 ++marked_for_reclamation_count;
413 break;
414 case MadeZombie:
415 ++zombified_count;
416 break;
417 case None:
418 break;
419 default:
420 ShouldNotReachHere();
421 }
422 }
423 _seen++;
424 handle_safepoint_request();
425 }
426 }
427
428 assert(_current.end(), "must have scanned the whole cache");
429
430 const Ticks sweep_end_counter = Ticks::now();
431 const Tickspan sweep_time = sweep_end_counter - sweep_start_counter;
432 {
433 MutexLockerEx mu(_stat_lock, Mutex::_no_safepoint_check_flag);
434 _total_time_sweeping += sweep_time;
435 _total_time_this_sweep += sweep_time;
436 _peak_sweep_fraction_time = MAX2(sweep_time, _peak_sweep_fraction_time);
437 _total_flushed_size += freed_memory;
438 _total_nof_methods_reclaimed += flushed_count;
439 _total_nof_c2_methods_reclaimed += flushed_c2_count;
440 _peak_sweep_time = MAX2(_peak_sweep_time, _total_time_this_sweep);
441 }
442 EventSweepCodeCache event(UNTIMED);
443 if (event.should_commit()) {
444 event.set_starttime(sweep_start_counter);
445 event.set_endtime(sweep_end_counter);
446 event.set_sweepIndex(_traversals);
447 event.set_sweptCount(swept_count);
448 event.set_flushedCount(flushed_count);
449 event.set_markedCount(marked_for_reclamation_count);
450 event.set_zombifiedCount(zombified_count);
451 event.commit();
452 }
453
454 #ifdef ASSERT
455 if(PrintMethodFlushing) {
456 tty->print_cr("### sweeper: sweep time(%d): ", (jlong)sweep_time.value());
457 }
458 #endif
459
460 log_sweep("finished");
461
462 // Sweeper is the only case where memory is released, check here if it
463 // is time to restart the compiler. Only checking if there is a certain
464 // amount of free memory in the code cache might lead to re-enabling
465 // compilation although no memory has been released. For example, there are
466 // cases when compilation was disabled although there is 4MB (or more) free
467 // memory in the code cache. The reason is code cache fragmentation. Therefore,
468 // it only makes sense to re-enable compilation if we have actually freed memory.
469 // Note that typically several kB are released for sweeping 16MB of the code
470 // cache. As a result, 'freed_memory' > 0 to restart the compiler.
471 if (!CompileBroker::should_compile_new_jobs() && (freed_memory > 0)) {
472 CompileBroker::set_should_compile_new_jobs(CompileBroker::run_compilation);
473 log_sweep("restart_compiler");
474 }
475 }
476
477 /**
478 * This function updates the sweeper statistics that keep track of nmethods
479 * state changes. If there is 'enough' state change, the sweeper is invoked
480 * as soon as possible. There can be data races on _bytes_changed. The data
481 * races are benign, since it does not matter if we loose a couple of bytes.
482 * In the worst case we call the sweeper a little later. Also, we are guaranteed
483 * to invoke the sweeper if the code cache gets full.
484 */
485 void NMethodSweeper::report_state_change(nmethod* nm) {
486 _bytes_changed += nm->total_size();
487 possibly_enable_sweeper();
488 }
489
490 /**
491 * Function determines if there was 'enough' state change in the code cache to invoke
492 * the sweeper again. Currently, we determine 'enough' as more than 1% state change in
493 * the code cache since the last sweep.
494 */
495 void NMethodSweeper::possibly_enable_sweeper() {
496 double percent_changed = ((double)_bytes_changed / (double)ReservedCodeCacheSize) * 100;
497 if (percent_changed > 1.0) {
498 _should_sweep = true;
499 }
500 }
501
502 class NMethodMarker: public StackObj {
503 private:
504 CodeCacheSweeperThread* _thread;
505 public:
506 NMethodMarker(nmethod* nm) {
507 JavaThread* current = JavaThread::current();
508 assert (current->is_Code_cache_sweeper_thread(), "Must be");
509 _thread = (CodeCacheSweeperThread*)JavaThread::current();
510 if (!nm->is_zombie() && !nm->is_unloaded()) {
511 // Only expose live nmethods for scanning
512 _thread->set_scanned_nmethod(nm);
513 }
514 }
515 ~NMethodMarker() {
516 _thread->set_scanned_nmethod(NULL);
517 }
518 };
519
520 void NMethodSweeper::release_nmethod(nmethod* nm) {
521 // Clean up any CompiledICHolders
522 {
523 ResourceMark rm;
524 MutexLocker ml_patch(CompiledIC_lock);
525 RelocIterator iter(nm);
526 while (iter.next()) {
527 if (iter.type() == relocInfo::virtual_call_type) {
528 CompiledIC::cleanup_call_site(iter.virtual_call_reloc());
529 }
530 }
531 }
532
533 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
534 nm->flush();
535 }
536
537 NMethodSweeper::MethodStateChange NMethodSweeper::process_nmethod(nmethod* nm) {
538 assert(nm != NULL, "sanity");
539 assert(!CodeCache_lock->owned_by_self(), "just checking");
540
541 MethodStateChange result = None;
542 // Make sure this nmethod doesn't get unloaded during the scan,
543 // since safepoints may happen during acquired below locks.
544 NMethodMarker nmm(nm);
545 SWEEP(nm);
546
547 // Skip methods that are currently referenced by the VM
548 if (nm->is_locked_by_vm()) {
549 // But still remember to clean-up inline caches for alive nmethods
550 if (nm->is_alive()) {
551 // Clean inline caches that point to zombie/non-entrant methods
552 MutexLocker cl(CompiledIC_lock);
553 nm->cleanup_inline_caches();
554 SWEEP(nm);
555 }
556 return result;
557 }
558
559 if (nm->is_zombie()) {
560 // If it is the first time we see nmethod then we mark it. Otherwise,
561 // we reclaim it. When we have seen a zombie method twice, we know that
562 // there are no inline caches that refer to it.
563 if (nm->is_marked_for_reclamation()) {
564 assert(!nm->is_locked_by_vm(), "must not flush locked nmethods");
565 if (PrintMethodFlushing && Verbose) {
566 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (marked for reclamation) being flushed", nm->compile_id(), nm);
567 }
568 release_nmethod(nm);
569 assert(result == None, "sanity");
570 result = Flushed;
571 } else {
572 if (PrintMethodFlushing && Verbose) {
573 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (zombie) being marked for reclamation", nm->compile_id(), nm);
574 }
575 nm->mark_for_reclamation();
576 // Keep track of code cache state change
577 _bytes_changed += nm->total_size();
578 SWEEP(nm);
579 assert(result == None, "sanity");
580 result = MarkedForReclamation;
581 }
582 } else if (nm->is_not_entrant()) {
583 // If there are no current activations of this method on the
584 // stack we can safely convert it to a zombie method
585 if (nm->can_not_entrant_be_converted()) {
586 // Clear ICStubs to prevent back patching stubs of zombie or unloaded
587 // nmethods during the next safepoint (see ICStub::finalize).
588 {
589 MutexLocker cl(CompiledIC_lock);
590 nm->clear_ic_stubs();
591 }
592 // Acquiring the CompiledIC_lock may block for a safepoint and set the
593 // nmethod to zombie (see 'CodeCache::make_marked_nmethods_zombies').
594 // Check if nmethod is still non-entrant at this point.
595 if (nm->is_not_entrant()) {
596 if (PrintMethodFlushing && Verbose) {
597 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (not entrant) being made zombie", nm->compile_id(), nm);
598 }
599 // Code cache state change is tracked in make_zombie()
600 nm->make_zombie();
601 SWEEP(nm);
602 assert(result == None, "sanity");
603 result = MadeZombie;
604 }
605 assert(nm->is_zombie(), "nmethod must be zombie");
606 } else {
607 // Still alive, clean up its inline caches
608 MutexLocker cl(CompiledIC_lock);
609 nm->cleanup_inline_caches();
610 SWEEP(nm);
611 }
612 } else if (nm->is_unloaded()) {
613 // Unloaded code, just make it a zombie
614 if (PrintMethodFlushing && Verbose) {
615 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (unloaded) being made zombie", nm->compile_id(), nm);
616 }
617 if (nm->is_osr_method()) {
618 SWEEP(nm);
619 // No inline caches will ever point to osr methods, so we can just remove it
620 release_nmethod(nm);
621 assert(result == None, "sanity");
622 result = Flushed;
623 } else {
624 // Code cache state change is tracked in make_zombie()
625 nm->make_zombie();
626 SWEEP(nm);
627 assert(result == None, "sanity");
628 result = MadeZombie;
629 }
630 } else {
631 possibly_flush(nm);
632 // Clean-up all inline caches that point to zombie/non-reentrant methods
633 MutexLocker cl(CompiledIC_lock);
634 nm->cleanup_inline_caches();
635 SWEEP(nm);
636 }
637 return result;
638 }
639
640
641 void NMethodSweeper::possibly_flush(nmethod* nm) {
642 if (UseCodeCacheFlushing) {
643 if (!nm->is_locked_by_vm() && !nm->is_osr_method() && !nm->is_native_method()) {
644 bool make_not_entrant = false;
645
646 // Do not make native methods and OSR-methods not-entrant
647 nm->dec_hotness_counter();
648 // Get the initial value of the hotness counter. This value depends on the
649 // ReservedCodeCacheSize
650 int reset_val = hotness_counter_reset_val();
651 int time_since_reset = reset_val - nm->hotness_counter();
652 int code_blob_type = (CodeCache::get_code_blob_type(nm->comp_level()));
653 double threshold = -reset_val + (CodeCache::reverse_free_ratio(code_blob_type) * NmethodSweepActivity);
654 // The less free space in the code cache we have - the bigger reverse_free_ratio() is.
655 // I.e., 'threshold' increases with lower available space in the code cache and a higher
656 // NmethodSweepActivity. If the current hotness counter - which decreases from its initial
657 // value until it is reset by stack walking - is smaller than the computed threshold, the
658 // corresponding nmethod is considered for removal.
659 if ((NmethodSweepActivity > 0) && (nm->hotness_counter() < threshold) && (time_since_reset > MinPassesBeforeFlush)) {
660 // A method is marked as not-entrant if the method is
661 // 1) 'old enough': nm->hotness_counter() < threshold
662 // 2) The method was in_use for a minimum amount of time: (time_since_reset > MinPassesBeforeFlush)
663 // The second condition is necessary if we are dealing with very small code cache
664 // sizes (e.g., <10m) and the code cache size is too small to hold all hot methods.
665 // The second condition ensures that methods are not immediately made not-entrant
666 // after compilation.
667 make_not_entrant = true;
668 }
669
670 // The stack-scanning low-cost detection may not see the method was used (which can happen for
671 // flat profiles). Check the age counter for possible data.
672 if (UseCodeAging && make_not_entrant && (nm->is_compiled_by_c2() || nm->is_compiled_by_c1())) {
673 MethodCounters* mc = nm->method()->get_method_counters(Thread::current());
674 if (mc != NULL) {
675 // Snapshot the value as it's changed concurrently
676 int age = mc->nmethod_age();
677 if (MethodCounters::is_nmethod_hot(age)) {
678 // The method has gone through flushing, and it became relatively hot that it deopted
679 // before we could take a look at it. Give it more time to appear in the stack traces,
680 // proportional to the number of deopts.
681 MethodData* md = nm->method()->method_data();
682 if (md != NULL && time_since_reset > (int)(MinPassesBeforeFlush * (md->tenure_traps() + 1))) {
683 // It's been long enough, we still haven't seen it on stack.
684 // Try to flush it, but enable counters the next time.
685 mc->reset_nmethod_age();
686 } else {
687 make_not_entrant = false;
688 }
689 } else if (MethodCounters::is_nmethod_warm(age)) {
690 // Method has counters enabled, and the method was used within
691 // previous MinPassesBeforeFlush sweeps. Reset the counter. Stay in the existing
692 // compiled state.
693 mc->reset_nmethod_age();
694 // delay the next check
695 nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val());
696 make_not_entrant = false;
697 } else if (MethodCounters::is_nmethod_age_unset(age)) {
698 // No counters were used before. Set the counters to the detection
699 // limit value. If the method is going to be used again it will be compiled
700 // with counters that we're going to use for analysis the the next time.
701 mc->reset_nmethod_age();
702 } else {
703 // Method was totally idle for 10 sweeps
704 // The counter already has the initial value, flush it and may be recompile
705 // later with counters
706 }
707 }
708 }
709
710 if (make_not_entrant) {
711 nm->make_not_entrant();
712
713 // Code cache state change is tracked in make_not_entrant()
714 if (PrintMethodFlushing && Verbose) {
715 tty->print_cr("### Nmethod %d/" PTR_FORMAT "made not-entrant: hotness counter %d/%d threshold %f",
716 nm->compile_id(), nm, nm->hotness_counter(), reset_val, threshold);
717 }
718 }
719 }
720 }
721 }
722
723 // Print out some state information about the current sweep and the
724 // state of the code cache if it's requested.
725 void NMethodSweeper::log_sweep(const char* msg, const char* format, ...) {
726 if (PrintMethodFlushing) {
727 stringStream s;
728 // Dump code cache state into a buffer before locking the tty,
729 // because log_state() will use locks causing lock conflicts.
730 CodeCache::log_state(&s);
731
732 ttyLocker ttyl;
733 tty->print("### sweeper: %s ", msg);
734 if (format != NULL) {
735 va_list ap;
736 va_start(ap, format);
737 tty->vprint(format, ap);
738 va_end(ap);
739 }
740 tty->print_cr("%s", s.as_string());
741 }
742
743 if (LogCompilation && (xtty != NULL)) {
744 stringStream s;
745 // Dump code cache state into a buffer before locking the tty,
746 // because log_state() will use locks causing lock conflicts.
747 CodeCache::log_state(&s);
748
749 ttyLocker ttyl;
750 xtty->begin_elem("sweeper state='%s' traversals='" INTX_FORMAT "' ", msg, (intx)traversal_count());
751 if (format != NULL) {
752 va_list ap;
753 va_start(ap, format);
754 xtty->vprint(format, ap);
755 va_end(ap);
756 }
757 xtty->print("%s", s.as_string());
758 xtty->stamp();
759 xtty->end_elem();
760 }
761 }
762
763 void NMethodSweeper::print() {
764 ttyLocker ttyl;
765 tty->print_cr("Code cache sweeper statistics:");
766 tty->print_cr(" Total sweep time: %1.0lfms", (double)_total_time_sweeping.value()/1000000);
767 tty->print_cr(" Total number of full sweeps: %ld", _total_nof_code_cache_sweeps);
768 tty->print_cr(" Total number of flushed methods: %ld(%ld C2 methods)", _total_nof_methods_reclaimed,
769 _total_nof_c2_methods_reclaimed);
770 tty->print_cr(" Total size of flushed methods: " SIZE_FORMAT "kB", _total_flushed_size/K);
771 }