1 /*
2 * Copyright (c) 1997, 2012, 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 "utilities/events.hpp"
40 #include "utilities/xmlstream.hpp"
41
42 #ifdef ASSERT
43
44 #define SWEEP(nm) record_sweep(nm, __LINE__)
45 // Sweeper logging code
46 class SweeperRecord {
47 public:
48 int traversal;
49 int invocation;
50 int compile_id;
51 long traversal_mark;
52 int state;
53 const char* kind;
54 address vep;
55 address uep;
56 int line;
57
58 void print() {
59 tty->print_cr("traversal = %d invocation = %d compile_id = %d %s uep = " PTR_FORMAT " vep = "
60 PTR_FORMAT " state = %d traversal_mark %d line = %d",
61 traversal,
62 invocation,
63 compile_id,
64 kind == NULL ? "" : kind,
65 uep,
66 vep,
67 state,
68 traversal_mark,
69 line);
70 }
71 };
72
73 static int _sweep_index = 0;
74 static SweeperRecord* _records = NULL;
75
76 void NMethodSweeper::report_events(int id, address entry) {
77 if (_records != NULL) {
78 for (int i = _sweep_index; i < SweeperLogEntries; i++) {
79 if (_records[i].uep == entry ||
80 _records[i].vep == entry ||
81 _records[i].compile_id == id) {
82 _records[i].print();
83 }
84 }
85 for (int i = 0; i < _sweep_index; 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 }
93 }
94
95 void NMethodSweeper::report_events() {
96 if (_records != NULL) {
97 for (int i = _sweep_index; i < SweeperLogEntries; i++) {
98 // skip empty records
99 if (_records[i].vep == NULL) continue;
100 _records[i].print();
101 }
102 for (int i = 0; i < _sweep_index; i++) {
103 // skip empty records
104 if (_records[i].vep == NULL) continue;
105 _records[i].print();
106 }
107 }
108 }
109
110 void NMethodSweeper::record_sweep(nmethod* nm, int line) {
111 if (_records != NULL) {
112 _records[_sweep_index].traversal = _traversals;
113 _records[_sweep_index].traversal_mark = nm->_stack_traversal_mark;
114 _records[_sweep_index].invocation = _invocations;
115 _records[_sweep_index].compile_id = nm->compile_id();
116 _records[_sweep_index].kind = nm->compile_kind();
117 _records[_sweep_index].state = nm->_state;
118 _records[_sweep_index].vep = nm->verified_entry_point();
119 _records[_sweep_index].uep = nm->entry_point();
120 _records[_sweep_index].line = line;
121
122 _sweep_index = (_sweep_index + 1) % SweeperLogEntries;
123 }
124 }
125 #else
126 #define SWEEP(nm)
127 #endif
128
129
130 long NMethodSweeper::_traversals = 0; // No. of stack traversals performed
131 nmethod* NMethodSweeper::_current = NULL; // Current nmethod
132 int NMethodSweeper::_seen = 0 ; // No. of nmethods we have currently processed in current pass of CodeCache
133
134 volatile int NMethodSweeper::_invocations = 0; // No. of invocations left until we are completed with this pass
135 volatile int NMethodSweeper::_sweep_started = 0; // Whether a sweep is in progress.
136
137 jint NMethodSweeper::_locked_seen = 0;
138 jint NMethodSweeper::_not_entrant_seen_on_stack = 0;
139 bool NMethodSweeper::_resweep = false;
140 jint NMethodSweeper::_flush_token = 0;
141 jlong NMethodSweeper::_last_full_flush_time = 0;
142 int NMethodSweeper::_highest_marked = 0;
143 int NMethodSweeper::_dead_compile_ids = 0;
144 long NMethodSweeper::_last_flush_traversal_id = 0;
145
146 class MarkActivationClosure: public CodeBlobClosure {
147 public:
148 virtual void do_code_blob(CodeBlob* cb) {
149 // If we see an activation belonging to a non_entrant nmethod, we mark it.
150 if (cb->is_nmethod() && ((nmethod*)cb)->is_not_entrant()) {
151 ((nmethod*)cb)->mark_as_seen_on_stack();
152 }
153 }
154 };
155 static MarkActivationClosure mark_activation_closure;
156
157 bool NMethodSweeper::sweep_in_progress() {
158 return (_current != NULL);
159 }
160
161 void NMethodSweeper::scan_stacks() {
162 assert(SafepointSynchronize::is_at_safepoint(), "must be executed at a safepoint");
163 if (!MethodFlushing) return;
164
165 // No need to synchronize access, since this is always executed at a
166 // safepoint.
167
168 // Make sure CompiledIC_lock in unlocked, since we might update some
169 // inline caches. If it is, we just bail-out and try later.
170 if (CompiledIC_lock->is_locked() || Patching_lock->is_locked()) return;
171
172 // Check for restart
173 assert(CodeCache::find_blob_unsafe(_current) == _current, "Sweeper nmethod cached state invalid");
174 if (!sweep_in_progress() && _resweep) {
175 _seen = 0;
176 _invocations = NmethodSweepFraction;
177 _current = CodeCache::first_nmethod();
178 _traversals += 1;
179 if (PrintMethodFlushing) {
180 tty->print_cr("### Sweep: stack traversal %d", _traversals);
181 }
182 Threads::nmethods_do(&mark_activation_closure);
183
184 // reset the flags since we started a scan from the beginning.
185 _resweep = false;
186 _locked_seen = 0;
187 _not_entrant_seen_on_stack = 0;
188 }
189
190 if (UseCodeCacheFlushing) {
191 // only allow new flushes after the interval is complete.
192 jlong now = os::javaTimeMillis();
193 jlong max_interval = (jlong)MinCodeCacheFlushingInterval * (jlong)1000;
194 jlong curr_interval = now - _last_full_flush_time;
195 if (curr_interval > max_interval) {
196 _flush_token = 0;
197 }
198
199 if (!CodeCache::needs_flushing() && !CompileBroker::should_compile_new_jobs()) {
200 CompileBroker::set_should_compile_new_jobs(CompileBroker::run_compilation);
201 log_sweep("restart_compiler");
202 }
203 }
204 }
205
206 void NMethodSweeper::possibly_sweep() {
207 assert(JavaThread::current()->thread_state() == _thread_in_vm, "must run in vm mode");
208 if (!MethodFlushing || !sweep_in_progress()) return;
209
210 if (_invocations > 0) {
211 // Only one thread at a time will sweep
212 jint old = Atomic::cmpxchg( 1, &_sweep_started, 0 );
213 if (old != 0) {
214 return;
215 }
216 #ifdef ASSERT
217 if (LogSweeper && _records == NULL) {
218 // Create the ring buffer for the logging code
219 _records = NEW_C_HEAP_ARRAY(SweeperRecord, SweeperLogEntries, mtGC);
220 memset(_records, 0, sizeof(SweeperRecord) * SweeperLogEntries);
221 }
222 #endif
223 if (_invocations > 0) {
224 sweep_code_cache();
225 _invocations--;
226 }
227 _sweep_started = 0;
228 }
229 }
230
231 void NMethodSweeper::sweep_code_cache() {
232 #ifdef ASSERT
233 jlong sweep_start;
234 if (PrintMethodFlushing) {
235 sweep_start = os::javaTimeMillis();
236 }
237 #endif
238 if (PrintMethodFlushing && Verbose) {
239 tty->print_cr("### Sweep at %d out of %d. Invocations left: %d", _seen, CodeCache::nof_nmethods(), _invocations);
240 }
241
242 if (!CompileBroker::should_compile_new_jobs()) {
243 // If we have turned off compilations we might as well do full sweeps
244 // in order to reach the clean state faster. Otherwise the sleeping compiler
245 // threads will slow down sweeping. After a few iterations the cache
246 // will be clean and sweeping stops (_resweep will not be set)
247 _invocations = 1;
248 }
249
250 // We want to visit all nmethods after NmethodSweepFraction
251 // invocations so divide the remaining number of nmethods by the
252 // remaining number of invocations. This is only an estimate since
253 // the number of nmethods changes during the sweep so the final
254 // stage must iterate until it there are no more nmethods.
255 int todo = (CodeCache::nof_nmethods() - _seen) / _invocations;
256
257 assert(!SafepointSynchronize::is_at_safepoint(), "should not be in safepoint when we get here");
258 assert(!CodeCache_lock->owned_by_self(), "just checking");
259
260 {
261 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
262
263 // The last invocation iterates until there are no more nmethods
264 for (int i = 0; (i < todo || _invocations == 1) && _current != NULL; i++) {
265 if (SafepointSynchronize::is_synchronizing()) { // Safepoint request
266 if (PrintMethodFlushing && Verbose) {
267 tty->print_cr("### Sweep at %d out of %d, invocation: %d, yielding to safepoint", _seen, CodeCache::nof_nmethods(), _invocations);
268 }
269 MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
270
271 assert(Thread::current()->is_Java_thread(), "should be java thread");
272 JavaThread* thread = (JavaThread*)Thread::current();
273 ThreadBlockInVM tbivm(thread);
274 thread->java_suspend_self();
275 }
276 // Since we will give up the CodeCache_lock, always skip ahead
277 // to the next nmethod. Other blobs can be deleted by other
278 // threads but nmethods are only reclaimed by the sweeper.
279 nmethod* next = CodeCache::next_nmethod(_current);
280
281 // Now ready to process nmethod and give up CodeCache_lock
282 {
283 MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
284 process_nmethod(_current);
285 }
286 _seen++;
287 _current = next;
288 }
289 }
290
291 assert(_invocations > 1 || _current == NULL, "must have scanned the whole cache");
292
293 if (!sweep_in_progress() && !_resweep && (_locked_seen || _not_entrant_seen_on_stack)) {
294 // we've completed a scan without making progress but there were
295 // nmethods we were unable to process either because they were
296 // locked or were still on stack. We don't have to aggresively
297 // clean them up so just stop scanning. We could scan once more
298 // but that complicates the control logic and it's unlikely to
299 // matter much.
300 if (PrintMethodFlushing) {
301 tty->print_cr("### Couldn't make progress on some nmethods so stopping sweep");
302 }
303 }
304
305 #ifdef ASSERT
306 if(PrintMethodFlushing) {
307 jlong sweep_end = os::javaTimeMillis();
308 tty->print_cr("### sweeper: sweep time(%d): " INT64_FORMAT, _invocations, sweep_end - sweep_start);
309 }
310 #endif
311
312 if (_invocations == 1) {
313 log_sweep("finished");
314 }
315
316 // Sweeper is the only case where memory is released,
317 // check here if it is time to restart the compiler.
318 if (UseCodeCacheFlushing && !CompileBroker::should_compile_new_jobs() && !CodeCache::needs_flushing()) {
319 CompileBroker::set_should_compile_new_jobs(CompileBroker::run_compilation);
320 log_sweep("restart_compiler");
321 }
322 }
323
324 class NMethodMarker: public StackObj {
325 private:
326 CompilerThread* _thread;
327 public:
328 NMethodMarker(nmethod* nm) {
329 _thread = CompilerThread::current();
330 if (!nm->is_zombie() && !nm->is_unloaded()) {
331 // Only expose live nmethods for scanning
332 _thread->set_scanned_nmethod(nm);
333 }
334 }
335 ~NMethodMarker() {
336 _thread->set_scanned_nmethod(NULL);
337 }
338 };
339
340 void NMethodSweeper::release_nmethod(nmethod *nm) {
341 // Clean up any CompiledICHolders
342 {
343 ResourceMark rm;
344 MutexLocker ml_patch(CompiledIC_lock);
345 RelocIterator iter(nm);
346 while (iter.next()) {
347 if (iter.type() == relocInfo::virtual_call_type) {
348 CompiledIC::cleanup_call_site(iter.virtual_call_reloc());
349 }
350 }
351 }
352
353 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
354 nm->flush();
355 }
356
357 void NMethodSweeper::process_nmethod(nmethod *nm) {
358 assert(!CodeCache_lock->owned_by_self(), "just checking");
359
360 // Make sure this nmethod doesn't get unloaded during the scan,
361 // since the locks acquired below might safepoint.
362 NMethodMarker nmm(nm);
363
364 SWEEP(nm);
365
366 // Skip methods that are currently referenced by the VM
367 if (nm->is_locked_by_vm()) {
368 // But still remember to clean-up inline caches for alive nmethods
369 if (nm->is_alive()) {
370 // Clean-up all inline caches that points to zombie/non-reentrant methods
371 MutexLocker cl(CompiledIC_lock);
372 nm->cleanup_inline_caches();
373 SWEEP(nm);
374 } else {
375 _locked_seen++;
376 SWEEP(nm);
377 }
378 return;
379 }
380
381 if (nm->is_zombie()) {
382 // If it is first time, we see nmethod then we mark it. Otherwise,
383 // we reclame it. When we have seen a zombie method twice, we know that
384 // there are no inline caches that refer to it.
385 if (nm->is_marked_for_reclamation()) {
386 assert(!nm->is_locked_by_vm(), "must not flush locked nmethods");
387 if (PrintMethodFlushing && Verbose) {
388 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (marked for reclamation) being flushed", nm->compile_id(), nm);
389 }
390 release_nmethod(nm);
391 } else {
392 if (PrintMethodFlushing && Verbose) {
393 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (zombie) being marked for reclamation", nm->compile_id(), nm);
394 }
395 nm->mark_for_reclamation();
396 _resweep = true;
397 SWEEP(nm);
398 }
399 } else if (nm->is_not_entrant()) {
400 // If there is no current activations of this method on the
401 // stack we can safely convert it to a zombie method
402 if (nm->can_not_entrant_be_converted()) {
403 if (PrintMethodFlushing && Verbose) {
404 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (not entrant) being made zombie", nm->compile_id(), nm);
405 }
406 nm->make_zombie();
407 _resweep = true;
408 SWEEP(nm);
409 } else {
410 // Still alive, clean up its inline caches
411 MutexLocker cl(CompiledIC_lock);
412 nm->cleanup_inline_caches();
413 // we coudn't transition this nmethod so don't immediately
414 // request a rescan. If this method stays on the stack for a
415 // long time we don't want to keep rescanning the code cache.
416 _not_entrant_seen_on_stack++;
417 SWEEP(nm);
418 }
419 } else if (nm->is_unloaded()) {
420 // Unloaded code, just make it a zombie
421 if (PrintMethodFlushing && Verbose)
422 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (unloaded) being made zombie", nm->compile_id(), nm);
423 if (nm->is_osr_method()) {
424 SWEEP(nm);
425 // No inline caches will ever point to osr methods, so we can just remove it
426 release_nmethod(nm);
427 } else {
428 nm->make_zombie();
429 _resweep = true;
430 SWEEP(nm);
431 }
432 } else {
433 assert(nm->is_alive(), "should be alive");
434
435 if (UseCodeCacheFlushing) {
436 if (nm->is_speculatively_disconnected() && !nm->is_locked_by_vm() && !nm->is_osr_method() &&
437 (_traversals > _last_flush_traversal_id + 2) && (nm->compile_id() < _highest_marked)) {
438 // This method has not been called since the forced cleanup happened
439 nm->make_not_entrant();
440 }
441 }
442
443 // Clean-up all inline caches that points to zombie/non-reentrant methods
444 MutexLocker cl(CompiledIC_lock);
445 nm->cleanup_inline_caches();
446 SWEEP(nm);
447 }
448 }
449
450 // Code cache unloading: when compilers notice the code cache is getting full,
451 // they will call a vm op that comes here. This code attempts to speculatively
452 // unload the oldest half of the nmethods (based on the compile job id) by
453 // saving the old code in a list in the CodeCache. Then
454 // execution resumes. If a method so marked is not called by the second sweeper
455 // stack traversal after the current one, the nmethod will be marked non-entrant and
456 // got rid of by normal sweeping. If the method is called, the Method*'s
457 // _code field is restored and the Method*/nmethod
458 // go back to their normal state.
459 void NMethodSweeper::handle_full_code_cache(bool is_full) {
460
461 if (is_full) {
462 // Since code cache is full, immediately stop new compiles
463 if (CompileBroker::set_should_compile_new_jobs(CompileBroker::stop_compilation)) {
464 log_sweep("disable_compiler");
465 }
466 }
467
468 // Make sure only one thread can flush
469 // The token is reset after CodeCacheMinimumFlushInterval in scan stacks,
470 // no need to check the timeout here.
471 jint old = Atomic::cmpxchg( 1, &_flush_token, 0 );
472 if (old != 0) {
473 return;
474 }
475
476 VM_HandleFullCodeCache op(is_full);
477 VMThread::execute(&op);
478
479 // resweep again as soon as possible
480 _resweep = true;
481 }
482
483 void NMethodSweeper::speculative_disconnect_nmethods(bool is_full) {
484 // If there was a race in detecting full code cache, only run
485 // one vm op for it or keep the compiler shut off
486
487 debug_only(jlong start = os::javaTimeMillis();)
488
489 // Traverse the code cache trying to dump the oldest nmethods
490 int curr_max_comp_id = CompileBroker::get_compilation_id();
491 int flush_target = ((curr_max_comp_id - _dead_compile_ids) / CodeCacheFlushingFraction) + _dead_compile_ids;
492
493 log_sweep("start_cleaning");
494
495 nmethod* nm = CodeCache::alive_nmethod(CodeCache::first());
496 jint disconnected = 0;
497 jint made_not_entrant = 0;
498 jint nmethod_count = 0;
499
500 while ((nm != NULL)){
501 int curr_comp_id = nm->compile_id();
502
503 // OSR methods cannot be flushed like this. Also, don't flush native methods
504 // since they are part of the JDK in most cases
505 if (!nm->is_osr_method() && !nm->is_locked_by_vm() && !nm->is_native_method()) {
506
507 // only count methods that can be speculatively disconnected
508 nmethod_count++;
509
510 if (nm->is_in_use() && (curr_comp_id < flush_target)) {
511 if ((nm->method()->code() == nm)) {
512 // This method has not been previously considered for
513 // unloading or it was restored already
514 CodeCache::speculatively_disconnect(nm);
515 disconnected++;
516 } else if (nm->is_speculatively_disconnected()) {
517 // This method was previously considered for preemptive unloading and was not called since then
518 CompilationPolicy::policy()->delay_compilation(nm->method());
519 nm->make_not_entrant();
520 made_not_entrant++;
521 }
522
523 if (curr_comp_id > _highest_marked) {
524 _highest_marked = curr_comp_id;
525 }
526 }
527 }
528 nm = CodeCache::alive_nmethod(CodeCache::next(nm));
529 }
530
531 // remember how many compile_ids wheren't seen last flush.
532 _dead_compile_ids = curr_max_comp_id - nmethod_count;
533
534 log_sweep("stop_cleaning",
535 "disconnected='" UINT32_FORMAT "' made_not_entrant='" UINT32_FORMAT "'",
536 disconnected, made_not_entrant);
537
538 // Shut off compiler. Sweeper will start over with a new stack scan and
539 // traversal cycle and turn it back on if it clears enough space.
540 if (is_full) {
541 _last_full_flush_time = os::javaTimeMillis();
542 }
543
544 // After two more traversals the sweeper will get rid of unrestored nmethods
545 _last_flush_traversal_id = _traversals;
546 _resweep = true;
547 #ifdef ASSERT
548 jlong end = os::javaTimeMillis();
549 if(PrintMethodFlushing && Verbose) {
550 tty->print_cr("### sweeper: unload time: " INT64_FORMAT, end-start);
551 }
552 #endif
553 }
554
555
556 // Print out some state information about the current sweep and the
557 // state of the code cache if it's requested.
558 void NMethodSweeper::log_sweep(const char* msg, const char* format, ...) {
559 if (PrintMethodFlushing) {
560 stringStream s;
561 // Dump code cache state into a buffer before locking the tty,
562 // because log_state() will use locks causing lock conflicts.
563 CodeCache::log_state(&s);
564
565 ttyLocker ttyl;
566 tty->print("### sweeper: %s ", msg);
567 if (format != NULL) {
568 va_list ap;
569 va_start(ap, format);
570 tty->vprint(format, ap);
571 va_end(ap);
572 }
573 tty->print_cr(s.as_string());
574 }
575
576 if (LogCompilation && (xtty != NULL)) {
577 stringStream s;
578 // Dump code cache state into a buffer before locking the tty,
579 // because log_state() will use locks causing lock conflicts.
580 CodeCache::log_state(&s);
581
582 ttyLocker ttyl;
583 xtty->begin_elem("sweeper state='%s' traversals='" INTX_FORMAT "' ", msg, (intx)traversal_count());
584 if (format != NULL) {
585 va_list ap;
586 va_start(ap, format);
587 xtty->vprint(format, ap);
588 va_end(ap);
589 }
590 xtty->print(s.as_string());
591 xtty->stamp();
592 xtty->end_elem();
593 }
594 }