1 /*
2 * Copyright (c) 1997, 2013, 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.hpp"
34 #include "runtime/compilationPolicy.hpp"
35 #include "runtime/mutexLocker.hpp"
36 #include "runtime/os.hpp"
37 #include "runtime/sweeper.hpp"
38 #include "runtime/vm_operations.hpp"
39 #include "trace/tracing.hpp"
40 #include "utilities/events.hpp"
41 #include "utilities/ticks.inline.hpp"
42 #include "utilities/xmlstream.hpp"
43
44 #ifdef ASSERT
45
46 #define SWEEP(nm) record_sweep(nm, __LINE__)
47 // Sweeper logging code
48 class SweeperRecord {
49 public:
50 int traversal;
51 int invocation;
52 int compile_id;
53 long traversal_mark;
54 int state;
55 const char* kind;
56 address vep;
57 address uep;
58 int line;
59
60 void print() {
61 tty->print_cr("traversal = %d invocation = %d compile_id = %d %s uep = " PTR_FORMAT " vep = "
62 PTR_FORMAT " state = %d traversal_mark %d line = %d",
63 traversal,
64 invocation,
65 compile_id,
66 kind == NULL ? "" : kind,
67 uep,
68 vep,
69 state,
70 traversal_mark,
71 line);
72 }
73 };
74
75 static int _sweep_index = 0;
76 static SweeperRecord* _records = NULL;
77
78 void NMethodSweeper::report_events(int id, address entry) {
79 if (_records != NULL) {
80 for (int i = _sweep_index; i < SweeperLogEntries; i++) {
81 if (_records[i].uep == entry ||
82 _records[i].vep == entry ||
83 _records[i].compile_id == id) {
84 _records[i].print();
85 }
86 }
87 for (int i = 0; i < _sweep_index; i++) {
88 if (_records[i].uep == entry ||
89 _records[i].vep == entry ||
90 _records[i].compile_id == id) {
91 _records[i].print();
92 }
93 }
94 }
95 }
96
97 void NMethodSweeper::report_events() {
98 if (_records != NULL) {
99 for (int i = _sweep_index; i < SweeperLogEntries; i++) {
100 // skip empty records
101 if (_records[i].vep == NULL) continue;
102 _records[i].print();
103 }
104 for (int i = 0; i < _sweep_index; i++) {
105 // skip empty records
106 if (_records[i].vep == NULL) continue;
107 _records[i].print();
108 }
109 }
110 }
111
112 void NMethodSweeper::record_sweep(nmethod* nm, int line) {
113 if (_records != NULL) {
114 _records[_sweep_index].traversal = _traversals;
115 _records[_sweep_index].traversal_mark = nm->_stack_traversal_mark;
116 _records[_sweep_index].invocation = _sweep_fractions_left;
117 _records[_sweep_index].compile_id = nm->compile_id();
118 _records[_sweep_index].kind = nm->compile_kind();
119 _records[_sweep_index].state = nm->_state;
120 _records[_sweep_index].vep = nm->verified_entry_point();
121 _records[_sweep_index].uep = nm->entry_point();
122 _records[_sweep_index].line = line;
123 _sweep_index = (_sweep_index + 1) % SweeperLogEntries;
124 }
125 }
126 #else
127 #define SWEEP(nm)
128 #endif
129
130 nmethod* NMethodSweeper::_current_nmethod = NULL; // Current nmethod
131 int NMethodSweeper::_current_type = 0; // Current CodeBlobType
132 long NMethodSweeper::_traversals = 0; // Stack scan count, also sweep ID.
133 long NMethodSweeper::_total_nof_code_cache_sweeps = 0; // Total number of full sweeps of the code cache
134 long NMethodSweeper::_time_counter = 0; // Virtual time used to periodically invoke sweeper
135 long NMethodSweeper::_last_sweep = 0; // Value of _time_counter when the last sweep happened
136 int NMethodSweeper::_seen = 0; // Nof. nmethod we have currently processed in current pass of CodeCache
137 int NMethodSweeper::_flushed_count = 0; // Nof. nmethods flushed in current sweep
138 int NMethodSweeper::_zombified_count = 0; // Nof. nmethods made zombie in current sweep
139 int NMethodSweeper::_marked_for_reclamation_count = 0; // Nof. nmethods marked for reclaim in current sweep
140
141 volatile bool NMethodSweeper::_should_sweep = true; // Indicates if we should invoke the sweeper
142 volatile int NMethodSweeper::_sweep_fractions_left = 0; // Nof. invocations left until we are completed with this pass
143 volatile int NMethodSweeper::_sweep_started = 0; // Flag to control conc sweeper
144 volatile int NMethodSweeper::_bytes_changed = 0; // Counts the total nmethod size if the nmethod changed from:
145 // 1) alive -> not_entrant
146 // 2) not_entrant -> zombie
147 // 3) zombie -> marked_for_reclamation
148 int NMethodSweeper::_hotness_counter_reset_val = 0;
149
150 long NMethodSweeper::_total_nof_methods_reclaimed = 0; // Accumulated nof methods flushed
151 long NMethodSweeper::_total_nof_c2_methods_reclaimed = 0; // Accumulated nof methods flushed
152 size_t NMethodSweeper::_total_flushed_size = 0; // Total number of bytes flushed from the code cache
153 Tickspan NMethodSweeper::_total_time_sweeping; // Accumulated time sweeping
154 Tickspan NMethodSweeper::_total_time_this_sweep; // Total time this sweep
155 Tickspan NMethodSweeper::_peak_sweep_time; // Peak time for a full sweep
156 Tickspan NMethodSweeper::_peak_sweep_fraction_time; // Peak time sweeping one fraction
157
158
159 class MarkActivationClosure: public CodeBlobClosure {
160 public:
161 virtual void do_code_blob(CodeBlob* cb) {
162 assert(cb->is_nmethod(), "CodeBlob should be nmethod");
163 nmethod* nm = (nmethod*)cb;
164 nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val());
165 // If we see an activation belonging to a non_entrant nmethod, we mark it.
166 if (nm->is_not_entrant()) {
167 nm->mark_as_seen_on_stack();
168 }
169 }
170 };
171 static MarkActivationClosure mark_activation_closure;
172
173 class SetHotnessClosure: public CodeBlobClosure {
174 public:
175 virtual void do_code_blob(CodeBlob* cb) {
176 assert(cb->is_nmethod(), "CodeBlob should be nmethod");
177 nmethod* nm = (nmethod*)cb;
178 nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val());
179 }
180 };
181 static SetHotnessClosure set_hotness_closure;
182
183
184 int NMethodSweeper::hotness_counter_reset_val() {
185 if (_hotness_counter_reset_val == 0) {
186 _hotness_counter_reset_val = (ReservedCodeCacheSize < M) ? 1 : (ReservedCodeCacheSize / M) * 2;
187 }
188 return _hotness_counter_reset_val;
189 }
190 bool NMethodSweeper::sweep_in_progress() {
191 return (_current_nmethod != NULL);
192 }
193
194 // Scans the stacks of all Java threads and marks activations of not-entrant methods.
195 // No need to synchronize access, since 'mark_active_nmethods' is always executed at a
196 // safepoint.
197 void NMethodSweeper::mark_active_nmethods() {
198 assert(SafepointSynchronize::is_at_safepoint(), "must be executed at a safepoint");
199 // If we do not want to reclaim not-entrant or zombie methods there is no need
200 // to scan stacks
201 if (!MethodFlushing) {
202 return;
203 }
204
205 // Increase time so that we can estimate when to invoke the sweeper again.
206 _time_counter++;
207
208 // Check for restart
209 assert(CodeCache::find_blob_unsafe(_current_nmethod) == _current_nmethod, "Sweeper nmethod cached state invalid");
210 if (!sweep_in_progress()) {
211 _seen = 0;
212 _sweep_fractions_left = NmethodSweepFraction;
213 _current_nmethod = (nmethod*)CodeCache::first_blob(CodeBlobType::MethodNonProfiled);
214 _current_type = CodeBlobType::MethodNonProfiled;
215 _traversals += 1;
216 _total_time_this_sweep = Tickspan();
217
218 if (PrintMethodFlushing) {
219 tty->print_cr("### Sweep: stack traversal %d", _traversals);
220 }
221 Threads::nmethods_do(&mark_activation_closure);
222
223 } else {
224 // Only set hotness counter
225 Threads::nmethods_do(&set_hotness_closure);
226 }
227
228 OrderAccess::storestore();
229 }
230 /**
231 * This function invokes the sweeper if at least one of the three conditions is met:
232 * (1) The code cache is getting full
233 * (2) There are sufficient state changes in/since the last sweep.
234 * (3) We have not been sweeping for 'some time'
235 */
236 void NMethodSweeper::possibly_sweep() {
237 assert(JavaThread::current()->thread_state() == _thread_in_vm, "must run in vm mode");
238 // Only compiler threads are allowed to sweep
239 if (!MethodFlushing || !sweep_in_progress() || !Thread::current()->is_Compiler_thread()) {
240 return;
241 }
242
243 // If there was no state change while nmethod sweeping, 'should_sweep' will be false.
244 // This is one of the two places where should_sweep can be set to true. The general
245 // idea is as follows: If there is enough free space in the code cache, there is no
246 // need to invoke the sweeper. The following formula (which determines whether to invoke
247 // the sweeper or not) depends on the assumption that for larger ReservedCodeCacheSizes
248 // we need less frequent sweeps than for smaller ReservedCodecCacheSizes. Furthermore,
249 // the formula considers how much space in the code cache is currently used. Here are
250 // some examples that will (hopefully) help in understanding.
251 //
252 // Small ReservedCodeCacheSizes: (e.g., < 16M) We invoke the sweeper every time, since
253 // the result of the division is 0. This
254 // keeps the used code cache size small
255 // (important for embedded Java)
256 // Large ReservedCodeCacheSize : (e.g., 256M + code cache is 10% full). The formula
257 // computes: (256 / 16) - 1 = 15
258 // As a result, we invoke the sweeper after
259 // 15 invocations of 'mark_active_nmethods.
260 // Large ReservedCodeCacheSize: (e.g., 256M + code Cache is 90% full). The formula
261 // computes: (256 / 16) - 10 = 6.
262 if (!_should_sweep) {
263 const int time_since_last_sweep = _time_counter - _last_sweep;
264 // ReservedCodeCacheSize has an 'unsigned' type. We need a 'signed' type for max_wait_time,
265 // since 'time_since_last_sweep' can be larger than 'max_wait_time'. If that happens using
266 // an unsigned type would cause an underflow (wait_until_next_sweep becomes a large positive
267 // value) that disables the intended periodic sweeps.
268 const int max_wait_time = ReservedCodeCacheSize / (16 * M);
269 // Use only signed types
270 double wait_until_next_sweep = max_wait_time - time_since_last_sweep -
271 MAX2(CodeCache::reverse_free_ratio(CodeBlobType::MethodProfiled),
272 CodeCache::reverse_free_ratio(CodeBlobType::MethodNonProfiled));
273 assert(wait_until_next_sweep <= (double)max_wait_time, "Calculation of code cache sweeper interval is incorrect");
274
275 if ((wait_until_next_sweep <= 0.0) || !CompileBroker::should_compile_new_jobs()) {
276 _should_sweep = true;
277 }
278 }
279
280 if (_should_sweep && _sweep_fractions_left > 0) {
281 // Only one thread at a time will sweep
282 jint old = Atomic::cmpxchg( 1, &_sweep_started, 0 );
283 if (old != 0) {
284 return;
285 }
286 #ifdef ASSERT
287 if (LogSweeper && _records == NULL) {
288 // Create the ring buffer for the logging code
289 _records = NEW_C_HEAP_ARRAY(SweeperRecord, SweeperLogEntries, mtGC);
290 memset(_records, 0, sizeof(SweeperRecord) * SweeperLogEntries);
291 }
292 #endif
293
294 if (_sweep_fractions_left > 0) {
295 sweep_code_cache();
296 _sweep_fractions_left--;
297 }
298
299 // We are done with sweeping the code cache once.
300 if (_sweep_fractions_left == 0) {
301 _total_nof_code_cache_sweeps++;
302 _last_sweep = _time_counter;
303 // Reset flag; temporarily disables sweeper
304 _should_sweep = false;
305 // If there was enough state change, 'possibly_enable_sweeper()'
306 // sets '_should_sweep' to true
307 possibly_enable_sweeper();
308 // Reset _bytes_changed only if there was enough state change. _bytes_changed
309 // can further increase by calls to 'report_state_change'.
310 if (_should_sweep) {
311 _bytes_changed = 0;
312 }
313 }
314 // Release work, because another compiler thread could continue.
315 OrderAccess::release_store((int*)&_sweep_started, 0);
316 }
317 }
318
319 void NMethodSweeper::sweep_code_cache() {
320 Ticks sweep_start_counter = Ticks::now();
321
322 _flushed_count = 0;
323 _zombified_count = 0;
324 _marked_for_reclamation_count = 0;
325
326 if (PrintMethodFlushing && Verbose) {
327 tty->print_cr("### Sweep at %d out of %d. Invocations left: %d", _seen, CodeCache::nof_nmethods(), _sweep_fractions_left);
328 }
329
330 if (!CompileBroker::should_compile_new_jobs()) {
331 // If we have turned off compilations we might as well do full sweeps
332 // in order to reach the clean state faster. Otherwise the sleeping compiler
333 // threads will slow down sweeping.
334 _sweep_fractions_left = 1;
335 }
336
337 // We want to visit all nmethods after NmethodSweepFraction
338 // invocations so divide the remaining number of nmethods by the
339 // remaining number of invocations. This is only an estimate since
340 // the number of nmethods changes during the sweep so the final
341 // stage must iterate until it there are no more nmethods.
342 int todo = (CodeCache::nof_nmethods() - _seen) / _sweep_fractions_left;
343 int swept_count = 0;
344
345
346 assert(!SafepointSynchronize::is_at_safepoint(), "should not be in safepoint when we get here");
347 assert(!CodeCache_lock->owned_by_self(), "just checking");
348
349 int freed_memory = 0;
350 {
351 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
352
353 // The last invocation iterates until there are no more nmethods
354 while ((swept_count < todo || _sweep_fractions_left == 1) && _current_nmethod != NULL) {
355 swept_count++;
356 if (SafepointSynchronize::is_synchronizing()) { // Safepoint request
357 if (PrintMethodFlushing && Verbose) {
358 tty->print_cr("### Sweep at %d out of %d, invocation: %d, yielding to safepoint", _seen, CodeCache::nof_nmethods(), _sweep_fractions_left);
359 }
360 MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
361
362 assert(Thread::current()->is_Java_thread(), "should be java thread");
363 JavaThread* thread = (JavaThread*)Thread::current();
364 ThreadBlockInVM tbivm(thread);
365 thread->java_suspend_self();
366 }
367 // Since we will give up the CodeCache_lock, always skip ahead
368 // to the next nmethod. Other blobs can be deleted by other
369 // threads but nmethods are only reclaimed by the sweeper.
370 nmethod* next = (nmethod*)CodeCache::next_blob(_current_nmethod, _current_type);
371
372 // Now ready to process nmethod and give up CodeCache_lock
373 {
374 MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
375 freed_memory += process_nmethod(_current_nmethod, _current_type);
376 }
377 _seen++;
378
379 while (next == NULL && _current_type < CodeBlobType::MethodProfiled) {
380 // We reached the last method of the type
381 // Go to next type that has methods available
382 _current_type++;
383 next = (nmethod*)CodeCache::first_blob(_current_type);
384 }
385 _current_nmethod = next;
386 }
387 }
388
389 assert(_sweep_fractions_left > 1 || _current_nmethod == NULL, "must have scanned the whole cache");
390
391 const Ticks sweep_end_counter = Ticks::now();
392 const Tickspan sweep_time = sweep_end_counter - sweep_start_counter;
393 _total_time_sweeping += sweep_time;
394 _total_time_this_sweep += sweep_time;
395 _peak_sweep_fraction_time = MAX2(sweep_time, _peak_sweep_fraction_time);
396 _total_flushed_size += freed_memory;
397 _total_nof_methods_reclaimed += _flushed_count;
398
399 EventSweepCodeCache event(UNTIMED);
400 if (event.should_commit()) {
401 event.set_starttime(sweep_start_counter);
402 event.set_endtime(sweep_end_counter);
403 event.set_sweepIndex(_traversals);
404 event.set_sweepFractionIndex(NmethodSweepFraction - _sweep_fractions_left + 1);
405 event.set_sweptCount(swept_count);
406 event.set_flushedCount(_flushed_count);
407 event.set_markedCount(_marked_for_reclamation_count);
408 event.set_zombifiedCount(_zombified_count);
409 event.commit();
410 }
411
412 #ifdef ASSERT
413 if(PrintMethodFlushing) {
414 tty->print_cr("### sweeper: sweep time(%d): "
415 INT64_FORMAT, _sweep_fractions_left, (jlong)sweep_time.value());
416 }
417 #endif
418
419 if (_sweep_fractions_left == 1) {
420 _peak_sweep_time = MAX2(_peak_sweep_time, _total_time_this_sweep);
421 log_sweep("finished");
422 }
423
424 // Sweeper is the only case where memory is released, check here if it
425 // is time to restart the compiler. Only checking if there is a certain
426 // amount of free memory in the code cache might lead to re-enabling
427 // compilation although no memory has been released. For example, there are
428 // cases when compilation was disabled although there is 4MB (or more) free
429 // memory in the code cache. The reason is code cache fragmentation. Therefore,
430 // it only makes sense to re-enable compilation if we have actually freed memory.
431 // Note that typically several kB are released for sweeping 16MB of the code
432 // cache. As a result, 'freed_memory' > 0 to restart the compiler.
433 if (!CompileBroker::should_compile_new_jobs() && (freed_memory > 0)) {
434 CompileBroker::set_should_compile_new_jobs(CompileBroker::run_compilation);
435 log_sweep("restart_compiler");
436 }
437 }
438
439 /**
440 * This function updates the sweeper statistics that keep track of nmethods
441 * state changes. If there is 'enough' state change, the sweeper is invoked
442 * as soon as possible. There can be data races on _bytes_changed. The data
443 * races are benign, since it does not matter if we loose a couple of bytes.
444 * In the worst case we call the sweeper a little later. Also, we are guaranteed
445 * to invoke the sweeper if the code cache gets full.
446 */
447 void NMethodSweeper::report_state_change(nmethod* nm) {
448 _bytes_changed += nm->total_size();
449 possibly_enable_sweeper();
450 }
451
452 /**
453 * Function determines if there was 'enough' state change in the code cache to invoke
454 * the sweeper again. Currently, we determine 'enough' as more than 1% state change in
455 * the code cache since the last sweep.
456 */
457 void NMethodSweeper::possibly_enable_sweeper() {
458 double percent_changed = ((double)_bytes_changed / (double)ReservedCodeCacheSize) * 100;
459 if (percent_changed > 1.0) {
460 _should_sweep = true;
461 }
462 }
463
464 class NMethodMarker: public StackObj {
465 private:
466 CompilerThread* _thread;
467 public:
468 NMethodMarker(nmethod* nm) {
469 _thread = CompilerThread::current();
470 if (!nm->is_zombie() && !nm->is_unloaded()) {
471 // Only expose live nmethods for scanning
472 _thread->set_scanned_nmethod(nm);
473 }
474 }
475 ~NMethodMarker() {
476 _thread->set_scanned_nmethod(NULL);
477 }
478 };
479
480 void NMethodSweeper::release_nmethod(nmethod *nm) {
481 // Clean up any CompiledICHolders
482 {
483 ResourceMark rm;
484 MutexLocker ml_patch(CompiledIC_lock);
485 RelocIterator iter(nm);
486 while (iter.next()) {
487 if (iter.type() == relocInfo::virtual_call_type) {
488 CompiledIC::cleanup_call_site(iter.virtual_call_reloc());
489 }
490 }
491 }
492
493 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
494 nm->flush();
495 }
496
497 int NMethodSweeper::process_nmethod(nmethod *nm, int code_blob_type) {
498 assert(!CodeCache_lock->owned_by_self(), "just checking");
499
500 int freed_memory = 0;
501 // Make sure this nmethod doesn't get unloaded during the scan,
502 // since safepoints may happen during acquired below locks.
503 NMethodMarker nmm(nm);
504 SWEEP(nm);
505
506 // Skip methods that are currently referenced by the VM
507 if (nm->is_locked_by_vm()) {
508 // But still remember to clean-up inline caches for alive nmethods
509 if (nm->is_alive()) {
510 // Clean inline caches that point to zombie/non-entrant methods
511 MutexLocker cl(CompiledIC_lock);
512 nm->cleanup_inline_caches();
513 SWEEP(nm);
514 }
515 return freed_memory;
516 }
517
518 if (nm->is_zombie()) {
519 // If it is the first time we see nmethod then we mark it. Otherwise,
520 // we reclaim it. When we have seen a zombie method twice, we know that
521 // there are no inline caches that refer to it.
522 if (nm->is_marked_for_reclamation()) {
523 assert(!nm->is_locked_by_vm(), "must not flush locked nmethods");
524 if (PrintMethodFlushing && Verbose) {
525 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (marked for reclamation) being flushed", nm->compile_id(), nm);
526 }
527 freed_memory = nm->total_size();
528 if (nm->is_compiled_by_c2()) {
529 _total_nof_c2_methods_reclaimed++;
530 }
531 release_nmethod(nm);
532 _flushed_count++;
533 } else {
534 if (PrintMethodFlushing && Verbose) {
535 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (zombie) being marked for reclamation", nm->compile_id(), nm);
536 }
537 nm->mark_for_reclamation();
538 // Keep track of code cache state change
539 _bytes_changed += nm->total_size();
540 _marked_for_reclamation_count++;
541 SWEEP(nm);
542 }
543 } else if (nm->is_not_entrant()) {
544 // If there are no current activations of this method on the
545 // stack we can safely convert it to a zombie method
546 if (nm->can_not_entrant_be_converted()) {
547 if (PrintMethodFlushing && Verbose) {
548 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (not entrant) being made zombie", nm->compile_id(), nm);
549 }
550 // Code cache state change is tracked in make_zombie()
551 nm->make_zombie();
552 _zombified_count++;
553 SWEEP(nm);
554 } else {
555 // Still alive, clean up its inline caches
556 MutexLocker cl(CompiledIC_lock);
557 nm->cleanup_inline_caches();
558 SWEEP(nm);
559 }
560 } else if (nm->is_unloaded()) {
561 // Unloaded code, just make it a zombie
562 if (PrintMethodFlushing && Verbose) {
563 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (unloaded) being made zombie", nm->compile_id(), nm);
564 }
565 if (nm->is_osr_method()) {
566 SWEEP(nm);
567 // No inline caches will ever point to osr methods, so we can just remove it
568 freed_memory = nm->total_size();
569 if (nm->is_compiled_by_c2()) {
570 _total_nof_c2_methods_reclaimed++;
571 }
572 release_nmethod(nm);
573 _flushed_count++;
574 } else {
575 // Code cache state change is tracked in make_zombie()
576 nm->make_zombie();
577 _zombified_count++;
578 SWEEP(nm);
579 }
580 } else {
581 if (UseCodeCacheFlushing) {
582 if (!nm->is_locked_by_vm() && !nm->is_osr_method() && !nm->is_native_method()) {
583 // Do not make native methods and OSR-methods not-entrant
584 nm->dec_hotness_counter();
585 // Get the initial value of the hotness counter. This value depends on the
586 // ReservedCodeCacheSize
587 int reset_val = hotness_counter_reset_val();
588 int time_since_reset = reset_val - nm->hotness_counter();
589 double threshold = -reset_val + (CodeCache::reverse_free_ratio(code_blob_type) * NmethodSweepActivity);
590 // The less free space in the code cache we have - the bigger reverse_free_ratio() is.
591 // I.e., 'threshold' increases with lower available space in the code cache and a higher
592 // NmethodSweepActivity. If the current hotness counter - which decreases from its initial
593 // value until it is reset by stack walking - is smaller than the computed threshold, the
594 // corresponding nmethod is considered for removal.
595 if ((NmethodSweepActivity > 0) && (nm->hotness_counter() < threshold) && (time_since_reset > 10)) {
596 // A method is marked as not-entrant if the method is
597 // 1) 'old enough': nm->hotness_counter() < threshold
598 // 2) The method was in_use for a minimum amount of time: (time_since_reset > 10)
599 // The second condition is necessary if we are dealing with very small code cache
600 // sizes (e.g., <10m) and the code cache size is too small to hold all hot methods.
601 // The second condition ensures that methods are not immediately made not-entrant
602 // after compilation.
603 nm->make_not_entrant();
604 // Code cache state change is tracked in make_not_entrant()
605 if (PrintMethodFlushing && Verbose) {
606 tty->print_cr("### Nmethod %d/" PTR_FORMAT "made not-entrant: hotness counter %d/%d threshold %f",
607 nm->compile_id(), nm, nm->hotness_counter(), reset_val, threshold);
608 }
609 }
610 }
611 }
612 // Clean-up all inline caches that point to zombie/non-reentrant methods
613 MutexLocker cl(CompiledIC_lock);
614 nm->cleanup_inline_caches();
615 SWEEP(nm);
616 }
617 return freed_memory;
618 }
619
620 // Print out some state information about the current sweep and the
621 // state of the code cache if it's requested.
622 void NMethodSweeper::log_sweep(const char* msg, const char* format, ...) {
623 if (PrintMethodFlushing) {
624 stringStream s;
625 // Dump code cache state into a buffer before locking the tty,
626 // because log_state() will use locks causing lock conflicts.
627 CodeCache::log_state(&s);
628
629 ttyLocker ttyl;
630 tty->print("### sweeper: %s ", msg);
631 if (format != NULL) {
632 va_list ap;
633 va_start(ap, format);
634 tty->vprint(format, ap);
635 va_end(ap);
636 }
637 tty->print_cr(s.as_string());
638 }
639
640 if (LogCompilation && (xtty != NULL)) {
641 stringStream s;
642 // Dump code cache state into a buffer before locking the tty,
643 // because log_state() will use locks causing lock conflicts.
644 CodeCache::log_state(&s);
645
646 ttyLocker ttyl;
647 xtty->begin_elem("sweeper state='%s' traversals='" INTX_FORMAT "' ", msg, (intx)traversal_count());
648 if (format != NULL) {
649 va_list ap;
650 va_start(ap, format);
651 xtty->vprint(format, ap);
652 va_end(ap);
653 }
654 xtty->print(s.as_string());
655 xtty->stamp();
656 xtty->end_elem();
657 }
658 }
659
660 void NMethodSweeper::print() {
661 ttyLocker ttyl;
662 tty->print_cr("Code cache sweeper statistics:");
663 tty->print_cr(" Total sweep time: %1.0lfms", (double)_total_time_sweeping.value()/1000000);
664 tty->print_cr(" Total number of full sweeps: %ld", _total_nof_code_cache_sweeps);
665 tty->print_cr(" Total number of flushed methods: %ld(%ld C2 methods)", _total_nof_methods_reclaimed,
666 _total_nof_c2_methods_reclaimed);
667 tty->print_cr(" Total size of flushed methods: " SIZE_FORMAT "kB", _total_flushed_size/K);
668 }