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