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/xmlstream.hpp"
42
43 #ifdef ASSERT
44
45 #define SWEEP(nm) record_sweep(nm, __LINE__)
46 // Sweeper logging code
47 class SweeperRecord {
48 public:
49 int traversal;
50 int invocation;
51 int compile_id;
52 long traversal_mark;
53 int state;
54 const char* kind;
55 address vep;
56 address uep;
57 int line;
58
59 void print() {
60 tty->print_cr("traversal = %d invocation = %d compile_id = %d %s uep = " PTR_FORMAT " vep = "
61 PTR_FORMAT " state = %d traversal_mark %d line = %d",
62 traversal,
63 invocation,
64 compile_id,
65 kind == NULL ? "" : kind,
66 uep,
67 vep,
68 state,
69 traversal_mark,
70 line);
71 }
72 };
73
74 static int _sweep_index = 0;
75 static SweeperRecord* _records = NULL;
76
77 void NMethodSweeper::report_events(int id, address entry) {
78 if (_records != NULL) {
79 for (int i = _sweep_index; i < SweeperLogEntries; i++) {
80 if (_records[i].uep == entry ||
81 _records[i].vep == entry ||
82 _records[i].compile_id == id) {
83 _records[i].print();
84 }
85 }
86 for (int i = 0; i < _sweep_index; i++) {
87 if (_records[i].uep == entry ||
88 _records[i].vep == entry ||
89 _records[i].compile_id == id) {
90 _records[i].print();
91 }
92 }
93 }
94 }
95
96 void NMethodSweeper::report_events() {
97 if (_records != NULL) {
98 for (int i = _sweep_index; i < SweeperLogEntries; i++) {
99 // skip empty records
100 if (_records[i].vep == NULL) continue;
101 _records[i].print();
102 }
103 for (int i = 0; i < _sweep_index; i++) {
104 // skip empty records
105 if (_records[i].vep == NULL) continue;
106 _records[i].print();
107 }
108 }
109 }
110
111 void NMethodSweeper::record_sweep(nmethod* nm, int line) {
112 if (_records != NULL) {
113 _records[_sweep_index].traversal = _traversals;
114 _records[_sweep_index].traversal_mark = nm->_stack_traversal_mark;
115 _records[_sweep_index].invocation = _invocations;
116 _records[_sweep_index].compile_id = nm->compile_id();
117 _records[_sweep_index].kind = nm->compile_kind();
118 _records[_sweep_index].state = nm->_state;
119 _records[_sweep_index].vep = nm->verified_entry_point();
120 _records[_sweep_index].uep = nm->entry_point();
121 _records[_sweep_index].line = line;
122
123 _sweep_index = (_sweep_index + 1) % SweeperLogEntries;
124 }
125 }
126 #else
127 #define SWEEP(nm)
128 #endif
129
130 nmethod* NMethodSweeper::_current = NULL; // Current nmethod
131 long NMethodSweeper::_traversals = 0; // Nof. stack traversals performed
132 int NMethodSweeper::_seen = 0; // Nof. nmethods we have currently processed in current pass of CodeCache
133 int NMethodSweeper::_flushed_count = 0; // Nof. nmethods flushed in current sweep
134 int NMethodSweeper::_zombified_count = 0; // Nof. nmethods made zombie in current sweep
135 int NMethodSweeper::_marked_count = 0; // Nof. nmethods marked for reclaim in current sweep
136
137 volatile int NMethodSweeper::_invocations = 0; // Nof. invocations left until we are completed with this pass
138 volatile int NMethodSweeper::_sweep_started = 0; // Whether a sweep is in progress.
139
140 jint NMethodSweeper::_locked_seen = 0;
141 jint NMethodSweeper::_not_entrant_seen_on_stack = 0;
142 bool NMethodSweeper::_request_mark_phase = false;
143
144 int NMethodSweeper::_total_nof_methods_reclaimed = 0;
145 jlong NMethodSweeper::_total_time_sweeping = 0;
146 jlong NMethodSweeper::_total_time_this_sweep = 0;
147 jlong NMethodSweeper::_peak_sweep_time = 0;
148 jlong NMethodSweeper::_peak_sweep_fraction_time = 0;
149 int NMethodSweeper::_hotness_counter_reset_val = 0;
150
151
152 class MarkActivationClosure: public CodeBlobClosure {
153 public:
154 virtual void do_code_blob(CodeBlob* cb) {
155 if (cb->is_nmethod()) {
156 nmethod* nm = (nmethod*)cb;
157 nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val());
158 // If we see an activation belonging to a non_entrant nmethod, we mark it.
159 if (nm->is_not_entrant()) {
160 nm->mark_as_seen_on_stack();
161 }
162 }
163 }
164 };
165 static MarkActivationClosure mark_activation_closure;
166
167 class SetHotnessClosure: public CodeBlobClosure {
168 public:
169 virtual void do_code_blob(CodeBlob* cb) {
170 if (cb->is_nmethod()) {
171 nmethod* nm = (nmethod*)cb;
172 nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val());
173 }
174 }
175 };
176 static SetHotnessClosure set_hotness_closure;
177
178
179 int NMethodSweeper::hotness_counter_reset_val() {
180 if (_hotness_counter_reset_val == 0) {
181 _hotness_counter_reset_val = (ReservedCodeCacheSize < M) ? 1 : (ReservedCodeCacheSize / M) * 2;
182 }
183 return _hotness_counter_reset_val;
184 }
185 bool NMethodSweeper::sweep_in_progress() {
186 return (_current != NULL);
187 }
188
189 // Scans the stacks of all Java threads and marks activations of not-entrant methods.
190 // No need to synchronize access, since 'mark_active_nmethods' is always executed at a
191 // safepoint.
192 void NMethodSweeper::mark_active_nmethods() {
193 assert(SafepointSynchronize::is_at_safepoint(), "must be executed at a safepoint");
194 // If we do not want to reclaim not-entrant or zombie methods there is no need
195 // to scan stacks
196 if (!MethodFlushing) {
197 return;
198 }
199
200 // Check for restart
201 assert(CodeCache::find_blob_unsafe(_current) == _current, "Sweeper nmethod cached state invalid");
202 if (!sweep_in_progress() && need_marking_phase()) {
203 _seen = 0;
204 _invocations = NmethodSweepFraction;
205 _current = CodeCache::first_nmethod();
206 _traversals += 1;
207 _total_time_this_sweep = 0;
208
209 if (PrintMethodFlushing) {
210 tty->print_cr("### Sweep: stack traversal %d", _traversals);
211 }
212 Threads::nmethods_do(&mark_activation_closure);
213
214 // reset the flags since we started a scan from the beginning.
215 reset_nmethod_marking();
216 _locked_seen = 0;
217 _not_entrant_seen_on_stack = 0;
218 } else {
219 // Only set hotness counter
220 Threads::nmethods_do(&set_hotness_closure);
221 }
222
223 OrderAccess::storestore();
224 }
225
226 void NMethodSweeper::possibly_sweep() {
227 assert(JavaThread::current()->thread_state() == _thread_in_vm, "must run in vm mode");
228 if (!MethodFlushing || !sweep_in_progress()) {
229 return;
230 }
231
232 if (_invocations > 0) {
233 // Only one thread at a time will sweep
234 jint old = Atomic::cmpxchg( 1, &_sweep_started, 0 );
235 if (old != 0) {
236 return;
237 }
238 #ifdef ASSERT
239 if (LogSweeper && _records == NULL) {
240 // Create the ring buffer for the logging code
241 _records = NEW_C_HEAP_ARRAY(SweeperRecord, SweeperLogEntries, mtGC);
242 memset(_records, 0, sizeof(SweeperRecord) * SweeperLogEntries);
243 }
244 #endif
245 if (_invocations > 0) {
246 sweep_code_cache();
247 _invocations--;
248 }
249 _sweep_started = 0;
250 }
251 }
252
253 void NMethodSweeper::sweep_code_cache() {
254
255 jlong sweep_start_counter = os::elapsed_counter();
256
257 _flushed_count = 0;
258 _zombified_count = 0;
259 _marked_count = 0;
260
261 if (PrintMethodFlushing && Verbose) {
262 tty->print_cr("### Sweep at %d out of %d. Invocations left: %d", _seen, CodeCache::nof_nmethods(), _invocations);
263 }
264
265 if (!CompileBroker::should_compile_new_jobs()) {
266 // If we have turned off compilations we might as well do full sweeps
267 // in order to reach the clean state faster. Otherwise the sleeping compiler
268 // threads will slow down sweeping.
269 _invocations = 1;
270 }
271
272 // We want to visit all nmethods after NmethodSweepFraction
273 // invocations so divide the remaining number of nmethods by the
274 // remaining number of invocations. This is only an estimate since
275 // the number of nmethods changes during the sweep so the final
276 // stage must iterate until it there are no more nmethods.
277 int todo = (CodeCache::nof_nmethods() - _seen) / _invocations;
278 int swept_count = 0;
279
280
281 assert(!SafepointSynchronize::is_at_safepoint(), "should not be in safepoint when we get here");
282 assert(!CodeCache_lock->owned_by_self(), "just checking");
283
284 int freed_memory = 0;
285 {
286 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
287
288 // The last invocation iterates until there are no more nmethods
289 for (int i = 0; (i < todo || _invocations == 1) && _current != NULL; i++) {
290 swept_count++;
291 if (SafepointSynchronize::is_synchronizing()) { // Safepoint request
292 if (PrintMethodFlushing && Verbose) {
293 tty->print_cr("### Sweep at %d out of %d, invocation: %d, yielding to safepoint", _seen, CodeCache::nof_nmethods(), _invocations);
294 }
295 MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
296
297 assert(Thread::current()->is_Java_thread(), "should be java thread");
298 JavaThread* thread = (JavaThread*)Thread::current();
299 ThreadBlockInVM tbivm(thread);
300 thread->java_suspend_self();
301 }
302 // Since we will give up the CodeCache_lock, always skip ahead
303 // to the next nmethod. Other blobs can be deleted by other
304 // threads but nmethods are only reclaimed by the sweeper.
305 nmethod* next = CodeCache::next_nmethod(_current);
306
307 // Now ready to process nmethod and give up CodeCache_lock
308 {
309 MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
310 freed_memory += process_nmethod(_current);
311 }
312 _seen++;
313 _current = next;
314 }
315 }
316
317 assert(_invocations > 1 || _current == NULL, "must have scanned the whole cache");
318
319 if (!sweep_in_progress() && !need_marking_phase() && (_locked_seen || _not_entrant_seen_on_stack)) {
320 // we've completed a scan without making progress but there were
321 // nmethods we were unable to process either because they were
322 // locked or were still on stack. We don't have to aggressively
323 // clean them up so just stop scanning. We could scan once more
324 // but that complicates the control logic and it's unlikely to
325 // matter much.
326 if (PrintMethodFlushing) {
327 tty->print_cr("### Couldn't make progress on some nmethods so stopping sweep");
328 }
329 }
330
331 jlong sweep_end_counter = os::elapsed_counter();
332 jlong sweep_time = sweep_end_counter - sweep_start_counter;
333 _total_time_sweeping += sweep_time;
334 _total_time_this_sweep += sweep_time;
335 _peak_sweep_fraction_time = MAX2(sweep_time, _peak_sweep_fraction_time);
336 _total_nof_methods_reclaimed += _flushed_count;
337
338 EventSweepCodeCache event(UNTIMED);
339 if (event.should_commit()) {
340 event.set_starttime(sweep_start_counter);
341 event.set_endtime(sweep_end_counter);
342 event.set_sweepIndex(_traversals);
343 event.set_sweepFractionIndex(NmethodSweepFraction - _invocations + 1);
344 event.set_sweptCount(swept_count);
345 event.set_flushedCount(_flushed_count);
346 event.set_markedCount(_marked_count);
347 event.set_zombifiedCount(_zombified_count);
348 event.commit();
349 }
350
351 #ifdef ASSERT
352 if(PrintMethodFlushing) {
353 tty->print_cr("### sweeper: sweep time(%d): " INT64_FORMAT, _invocations, (jlong)sweep_time);
354 }
355 #endif
356
357 if (_invocations == 1) {
358 _peak_sweep_time = MAX2(_peak_sweep_time, _total_time_this_sweep);
359 log_sweep("finished");
360 }
361
362 // Sweeper is the only case where memory is released, check here if it
363 // is time to restart the compiler. Only checking if there is a certain
364 // amount of free memory in the code cache might lead to re-enabling
365 // compilation although no memory has been released. For example, there are
366 // cases when compilation was disabled although there is 4MB (or more) free
367 // memory in the code cache. The reason is code cache fragmentation. Therefore,
368 // it only makes sense to re-enable compilation if we have actually freed memory.
369 // Note that typically several kB are released for sweeping 16MB of the code
370 // cache. As a result, 'freed_memory' > 0 to restart the compiler.
371 if (UseCodeCacheFlushing && (!CompileBroker::should_compile_new_jobs() && (freed_memory > 0))) {
372 CompileBroker::set_should_compile_new_jobs(CompileBroker::run_compilation);
373 log_sweep("restart_compiler");
374 }
375 }
376
377 class NMethodMarker: public StackObj {
378 private:
379 CompilerThread* _thread;
380 public:
381 NMethodMarker(nmethod* nm) {
382 _thread = CompilerThread::current();
383 if (!nm->is_zombie() && !nm->is_unloaded()) {
384 // Only expose live nmethods for scanning
385 _thread->set_scanned_nmethod(nm);
386 }
387 }
388 ~NMethodMarker() {
389 _thread->set_scanned_nmethod(NULL);
390 }
391 };
392
393 void NMethodSweeper::release_nmethod(nmethod *nm) {
394 // Clean up any CompiledICHolders
395 {
396 ResourceMark rm;
397 MutexLocker ml_patch(CompiledIC_lock);
398 RelocIterator iter(nm);
399 while (iter.next()) {
400 if (iter.type() == relocInfo::virtual_call_type) {
401 CompiledIC::cleanup_call_site(iter.virtual_call_reloc());
402 }
403 }
404 }
405
406 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
407 nm->flush();
408 }
409
410 int NMethodSweeper::process_nmethod(nmethod *nm) {
411 assert(!CodeCache_lock->owned_by_self(), "just checking");
412
413 int freed_memory = 0;
414 // Make sure this nmethod doesn't get unloaded during the scan,
415 // since safepoints may happen during acquired below locks.
416 NMethodMarker nmm(nm);
417 SWEEP(nm);
418
419 // Skip methods that are currently referenced by the VM
420 if (nm->is_locked_by_vm()) {
421 // But still remember to clean-up inline caches for alive nmethods
422 if (nm->is_alive()) {
423 // Clean inline caches that point to zombie/non-entrant methods
424 MutexLocker cl(CompiledIC_lock);
425 nm->cleanup_inline_caches();
426 SWEEP(nm);
427 } else {
428 _locked_seen++;
429 SWEEP(nm);
430 }
431 return freed_memory;
432 }
433
434 if (nm->is_zombie()) {
435 // If it is the first time we see nmethod then we mark it. Otherwise,
436 // we reclaim it. When we have seen a zombie method twice, we know that
437 // there are no inline caches that refer to it.
438 if (nm->is_marked_for_reclamation()) {
439 assert(!nm->is_locked_by_vm(), "must not flush locked nmethods");
440 if (PrintMethodFlushing && Verbose) {
441 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (marked for reclamation) being flushed", nm->compile_id(), nm);
442 }
443 freed_memory = nm->total_size();
444 release_nmethod(nm);
445 _flushed_count++;
446 } else {
447 if (PrintMethodFlushing && Verbose) {
448 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (zombie) being marked for reclamation", nm->compile_id(), nm);
449 }
450 nm->mark_for_reclamation();
451 request_nmethod_marking();
452 _marked_count++;
453 SWEEP(nm);
454 }
455 } else if (nm->is_not_entrant()) {
456 // If there are no current activations of this method on the
457 // stack we can safely convert it to a zombie method
458 if (nm->can_not_entrant_be_converted()) {
459 if (PrintMethodFlushing && Verbose) {
460 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (not entrant) being made zombie", nm->compile_id(), nm);
461 }
462 nm->make_zombie();
463 request_nmethod_marking();
464 _zombified_count++;
465 SWEEP(nm);
466 } else {
467 // Still alive, clean up its inline caches
468 MutexLocker cl(CompiledIC_lock);
469 nm->cleanup_inline_caches();
470 // we coudn't transition this nmethod so don't immediately
471 // request a rescan. If this method stays on the stack for a
472 // long time we don't want to keep rescanning the code cache.
473 _not_entrant_seen_on_stack++;
474 SWEEP(nm);
475 }
476 } else if (nm->is_unloaded()) {
477 // Unloaded code, just make it a zombie
478 if (PrintMethodFlushing && Verbose) {
479 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (unloaded) being made zombie", nm->compile_id(), nm);
480 }
481 if (nm->is_osr_method()) {
482 SWEEP(nm);
483 // No inline caches will ever point to osr methods, so we can just remove it
484 freed_memory = nm->total_size();
485 release_nmethod(nm);
486 _flushed_count++;
487 } else {
488 nm->make_zombie();
489 request_nmethod_marking();
490 _zombified_count++;
491 SWEEP(nm);
492 }
493 } else {
494 if (UseCodeCacheFlushing) {
495 if (!nm->is_locked_by_vm() && !nm->is_osr_method() && !nm->is_native_method()) {
496 // Do not make native methods and OSR-methods not-entrant
497 nm->dec_hotness_counter();
498 // Get the initial value of the hotness counter. This value depends on the
499 // ReservedCodeCacheSize
500 int reset_val = hotness_counter_reset_val();
501 int time_since_reset = reset_val - nm->hotness_counter();
502 double threshold = -reset_val + (CodeCache::reverse_free_ratio() * NmethodSweepActivity);
503 // The less free space in the code cache we have - the bigger reverse_free_ratio() is.
504 // I.e., 'threshold' increases with lower available space in the code cache and a higher
505 // NmethodSweepActivity. If the current hotness counter - which decreases from its initial
506 // value until it is reset by stack walking - is smaller than the computed threshold, the
507 // corresponding nmethod is considered for removal.
508 if ((NmethodSweepActivity > 0) && (nm->hotness_counter() < threshold) && (time_since_reset > 10)) {
509 // A method is marked as not-entrant if the method is
510 // 1) 'old enough': nm->hotness_counter() < threshold
511 // 2) The method was in_use for a minimum amount of time: (time_since_reset > 10)
512 // The second condition is necessary if we are dealing with very small code cache
513 // sizes (e.g., <10m) and the code cache size is too small to hold all hot methods.
514 // The second condition ensures that methods are not immediately made not-entrant
515 // after compilation.
516 nm->make_not_entrant();
517 request_nmethod_marking();
518 }
519 }
520 }
521 // Clean-up all inline caches that point to zombie/non-reentrant methods
522 MutexLocker cl(CompiledIC_lock);
523 nm->cleanup_inline_caches();
524 SWEEP(nm);
525 }
526 return freed_memory;
527 }
528
529 // Print out some state information about the current sweep and the
530 // state of the code cache if it's requested.
531 void NMethodSweeper::log_sweep(const char* msg, const char* format, ...) {
532 if (PrintMethodFlushing) {
533 stringStream s;
534 // Dump code cache state into a buffer before locking the tty,
535 // because log_state() will use locks causing lock conflicts.
536 CodeCache::log_state(&s);
537
538 ttyLocker ttyl;
539 tty->print("### sweeper: %s ", msg);
540 if (format != NULL) {
541 va_list ap;
542 va_start(ap, format);
543 tty->vprint(format, ap);
544 va_end(ap);
545 }
546 tty->print_cr(s.as_string());
547 }
548
549 if (LogCompilation && (xtty != NULL)) {
550 stringStream s;
551 // Dump code cache state into a buffer before locking the tty,
552 // because log_state() will use locks causing lock conflicts.
553 CodeCache::log_state(&s);
554
555 ttyLocker ttyl;
556 xtty->begin_elem("sweeper state='%s' traversals='" INTX_FORMAT "' ", msg, (intx)traversal_count());
557 if (format != NULL) {
558 va_list ap;
559 va_start(ap, format);
560 xtty->vprint(format, ap);
561 va_end(ap);
562 }
563 xtty->print(s.as_string());
564 xtty->stamp();
565 xtty->end_elem();
566 }
567 }