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/nmethod.hpp"
28 #include "compiler/compileBroker.hpp"
29 #include "memory/resourceArea.hpp"
30 #include "oops/methodOop.hpp"
31 #include "runtime/atomic.hpp"
32 #include "runtime/compilationPolicy.hpp"
33 #include "runtime/mutexLocker.hpp"
34 #include "runtime/os.hpp"
35 #include "runtime/sweeper.hpp"
36 #include "runtime/vm_operations.hpp"
37 #include "utilities/events.hpp"
38 #include "utilities/xmlstream.hpp"
39
40 #ifdef ASSERT
41
42 #define SWEEP(nm) record_sweep(nm, __LINE__)
43 // Sweeper logging code
44 class SweeperRecord {
45 public:
46 int traversal;
47 int invocation;
48 int compile_id;
49 long traversal_mark;
50 int state;
51 const char* kind;
52 address vep;
53 address uep;
54 int line;
55
56 void print() {
57 tty->print_cr("traversal = %d invocation = %d compile_id = %d %s uep = " PTR_FORMAT " vep = "
58 PTR_FORMAT " state = %d traversal_mark %d line = %d",
59 traversal,
60 invocation,
61 compile_id,
62 kind == NULL ? "" : kind,
63 uep,
64 vep,
65 state,
66 traversal_mark,
67 line);
68 }
69 };
70
71 static int _sweep_index = 0;
72 static SweeperRecord* _records = NULL;
73
74 void NMethodSweeper::report_events(int id, address entry) {
75 if (_records != NULL) {
76 for (int i = _sweep_index; i < SweeperLogEntries; i++) {
77 if (_records[i].uep == entry ||
78 _records[i].vep == entry ||
79 _records[i].compile_id == id) {
80 _records[i].print();
81 }
82 }
83 for (int i = 0; i < _sweep_index; i++) {
84 if (_records[i].uep == entry ||
85 _records[i].vep == entry ||
86 _records[i].compile_id == id) {
87 _records[i].print();
88 }
89 }
90 }
91 }
92
93 void NMethodSweeper::report_events() {
94 if (_records != NULL) {
95 for (int i = _sweep_index; i < SweeperLogEntries; i++) {
96 // skip empty records
97 if (_records[i].vep == NULL) continue;
98 _records[i].print();
99 }
100 for (int i = 0; i < _sweep_index; i++) {
101 // skip empty records
102 if (_records[i].vep == NULL) continue;
103 _records[i].print();
104 }
105 }
106 }
107
108 void NMethodSweeper::record_sweep(nmethod* nm, int line) {
109 if (_records != NULL) {
110 _records[_sweep_index].traversal = _traversals;
111 _records[_sweep_index].traversal_mark = nm->_stack_traversal_mark;
112 _records[_sweep_index].invocation = _invocations;
113 _records[_sweep_index].compile_id = nm->compile_id();
114 _records[_sweep_index].kind = nm->compile_kind();
115 _records[_sweep_index].state = nm->_state;
116 _records[_sweep_index].vep = nm->verified_entry_point();
117 _records[_sweep_index].uep = nm->entry_point();
118 _records[_sweep_index].line = line;
119
120 _sweep_index = (_sweep_index + 1) % SweeperLogEntries;
121 }
122 }
123 #else
124 #define SWEEP(nm)
125 #endif
126
127
128 long NMethodSweeper::_traversals = 0; // No. of stack traversals performed
129 nmethod* NMethodSweeper::_current = NULL; // Current nmethod
130 int NMethodSweeper::_seen = 0 ; // No. of nmethods we have currently processed in current pass of CodeCache
131
132 volatile int NMethodSweeper::_invocations = 0; // No. of invocations left until we are completed with this pass
133 volatile int NMethodSweeper::_sweep_started = 0; // Whether a sweep is in progress.
134
135 jint NMethodSweeper::_locked_seen = 0;
136 jint NMethodSweeper::_not_entrant_seen_on_stack = 0;
137 bool NMethodSweeper::_rescan = false;
138 bool NMethodSweeper::_do_sweep = false;
139 bool NMethodSweeper::_was_full = false;
140 jint NMethodSweeper::_advise_to_sweep = 0;
141 jlong NMethodSweeper::_last_was_full = 0;
142 uint NMethodSweeper::_highest_marked = 0;
143 long NMethodSweeper::_was_full_traversal = 0;
144
145 class MarkActivationClosure: public CodeBlobClosure {
146 public:
147 virtual void do_code_blob(CodeBlob* cb) {
148 // If we see an activation belonging to a non_entrant nmethod, we mark it.
149 if (cb->is_nmethod() && ((nmethod*)cb)->is_not_entrant()) {
150 ((nmethod*)cb)->mark_as_seen_on_stack();
151 }
152 }
153 };
154 static MarkActivationClosure mark_activation_closure;
155
156 void NMethodSweeper::scan_stacks() {
157 assert(SafepointSynchronize::is_at_safepoint(), "must be executed at a safepoint");
158 if (!MethodFlushing) return;
159 _do_sweep = true;
160
161 // No need to synchronize access, since this is always executed at a
162 // safepoint. If we aren't in the middle of scan and a rescan
163 // hasn't been requested then just return. If UseCodeCacheFlushing is on and
164 // code cache flushing is in progress, don't skip sweeping to help make progress
165 // clearing space in the code cache.
166 if ((_current == NULL && !_rescan) && !(UseCodeCacheFlushing && !CompileBroker::should_compile_new_jobs())) {
167 _do_sweep = false;
168 return;
169 }
170
171 // Make sure CompiledIC_lock in unlocked, since we might update some
172 // inline caches. If it is, we just bail-out and try later.
173 if (CompiledIC_lock->is_locked() || Patching_lock->is_locked()) return;
174
175 // Check for restart
176 assert(CodeCache::find_blob_unsafe(_current) == _current, "Sweeper nmethod cached state invalid");
177 if (_current == NULL) {
178 _seen = 0;
179 _invocations = NmethodSweepFraction;
180 _current = CodeCache::first_nmethod();
181 _traversals += 1;
182 if (PrintMethodFlushing) {
183 tty->print_cr("### Sweep: stack traversal %d", _traversals);
184 }
185 Threads::nmethods_do(&mark_activation_closure);
186
187 // reset the flags since we started a scan from the beginning.
188 _rescan = false;
189 _locked_seen = 0;
190 _not_entrant_seen_on_stack = 0;
191 }
192
193 if (UseCodeCacheFlushing) {
194 if (!CodeCache::needs_flushing()) {
195 // scan_stacks() runs during a safepoint, no race with setters
196 _advise_to_sweep = 0;
197 }
198
199 if (was_full()) {
200 // There was some progress so attempt to restart the compiler
201 jlong now = os::javaTimeMillis();
202 jlong max_interval = (jlong)MinCodeCacheFlushingInterval * (jlong)1000;
203 jlong curr_interval = now - _last_was_full;
204 if ((!CodeCache::needs_flushing()) && (curr_interval > max_interval)) {
205 CompileBroker::set_should_compile_new_jobs(CompileBroker::run_compilation);
206 set_was_full(false);
207
208 // Update the _last_was_full time so we can tell how fast the
209 // code cache is filling up
210 _last_was_full = os::javaTimeMillis();
211
212 log_sweep("restart_compiler");
213 }
214 }
215 }
216 }
217
218 void NMethodSweeper::possibly_sweep() {
219 assert(JavaThread::current()->thread_state() == _thread_in_vm, "must run in vm mode");
220 if ((!MethodFlushing) || (!_do_sweep)) return;
221
222 if (_invocations > 0) {
223 // Only one thread at a time will sweep
224 jint old = Atomic::cmpxchg( 1, &_sweep_started, 0 );
225 if (old != 0) {
226 return;
227 }
228 #ifdef ASSERT
229 if (LogSweeper && _records == NULL) {
230 // Create the ring buffer for the logging code
231 _records = NEW_C_HEAP_ARRAY(SweeperRecord, SweeperLogEntries);
232 memset(_records, 0, sizeof(SweeperRecord) * SweeperLogEntries);
233 }
234 #endif
235 if (_invocations > 0) {
236 sweep_code_cache();
237 _invocations--;
238 }
239 _sweep_started = 0;
240 }
241 }
242
243 void NMethodSweeper::sweep_code_cache() {
244 #ifdef ASSERT
245 jlong sweep_start;
246 if (PrintMethodFlushing) {
247 sweep_start = os::javaTimeMillis();
248 }
249 #endif
250 if (PrintMethodFlushing && Verbose) {
251 tty->print_cr("### Sweep at %d out of %d. Invocations left: %d", _seen, CodeCache::nof_nmethods(), _invocations);
252 }
253
254 // We want to visit all nmethods after NmethodSweepFraction
255 // invocations so divide the remaining number of nmethods by the
256 // remaining number of invocations. This is only an estimate since
257 // the number of nmethods changes during the sweep so the final
258 // stage must iterate until it there are no more nmethods.
259 int todo = (CodeCache::nof_nmethods() - _seen) / _invocations;
260
261 assert(!SafepointSynchronize::is_at_safepoint(), "should not be in safepoint when we get here");
262 assert(!CodeCache_lock->owned_by_self(), "just checking");
263
264 {
265 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
266
267 // The last invocation iterates until there are no more nmethods
268 for (int i = 0; (i < todo || _invocations == 1) && _current != NULL; i++) {
269 if (SafepointSynchronize::is_synchronizing()) { // Safepoint request
270 if (PrintMethodFlushing && Verbose) {
271 tty->print_cr("### Sweep at %d out of %d, aborting due to safepoint request", CodeCache::nof_nmethods(), _invocations);
272 }
273 _invocations++; // Restart this iteration later
274 break; // Bail out
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 (_current == NULL && !_rescan && (_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
317 class NMethodMarker: public StackObj {
318 private:
319 CompilerThread* _thread;
320 public:
321 NMethodMarker(nmethod* nm) {
322 _thread = CompilerThread::current();
323 _thread->set_scanned_nmethod(nm);
324 }
325 ~NMethodMarker() {
326 _thread->set_scanned_nmethod(NULL);
327 }
328 };
329
330
331 void NMethodSweeper::process_nmethod(nmethod *nm) {
332 assert(!CodeCache_lock->owned_by_self(), "just checking");
333
334 // Make sure this nmethod doesn't get unloaded during the scan,
335 // since the locks acquired below might safepoint.
336 NMethodMarker nmm(nm);
337
338 SWEEP(nm);
339
340 // Skip methods that are currently referenced by the VM
341 if (nm->is_locked_by_vm()) {
342 // But still remember to clean-up inline caches for alive nmethods
343 if (nm->is_alive()) {
344 // Clean-up all inline caches that points to zombie/non-reentrant methods
345 MutexLocker cl(CompiledIC_lock);
346 nm->cleanup_inline_caches();
347 SWEEP(nm);
348 } else {
349 _locked_seen++;
350 SWEEP(nm);
351 }
352 return;
353 }
354
355 if (nm->is_zombie()) {
356 // If it is first time, we see nmethod then we mark it. Otherwise,
357 // we reclame it. When we have seen a zombie method twice, we know that
358 // there are no inline caches that refer to it.
359 if (nm->is_marked_for_reclamation()) {
360 assert(!nm->is_locked_by_vm(), "must not flush locked nmethods");
361 if (PrintMethodFlushing && Verbose) {
362 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (marked for reclamation) being flushed", nm->compile_id(), nm);
363 }
364 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
365 nm->flush();
366 } else {
367 if (PrintMethodFlushing && Verbose) {
368 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (zombie) being marked for reclamation", nm->compile_id(), nm);
369 }
370 nm->mark_for_reclamation();
371 _rescan = true;
372 SWEEP(nm);
373 }
374 } else if (nm->is_not_entrant()) {
375 // If there is no current activations of this method on the
376 // stack we can safely convert it to a zombie method
377 if (nm->can_not_entrant_be_converted()) {
378 if (PrintMethodFlushing && Verbose) {
379 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (not entrant) being made zombie", nm->compile_id(), nm);
380 }
381 nm->make_zombie();
382 _rescan = true;
383 SWEEP(nm);
384 } else {
385 // Still alive, clean up its inline caches
386 MutexLocker cl(CompiledIC_lock);
387 nm->cleanup_inline_caches();
388 // we coudn't transition this nmethod so don't immediately
389 // request a rescan. If this method stays on the stack for a
390 // long time we don't want to keep rescanning the code cache.
391 _not_entrant_seen_on_stack++;
392 SWEEP(nm);
393 }
394 } else if (nm->is_unloaded()) {
395 // Unloaded code, just make it a zombie
396 if (PrintMethodFlushing && Verbose)
397 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (unloaded) being made zombie", nm->compile_id(), nm);
398 if (nm->is_osr_method()) {
399 // No inline caches will ever point to osr methods, so we can just remove it
400 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
401 SWEEP(nm);
402 nm->flush();
403 } else {
404 nm->make_zombie();
405 _rescan = true;
406 SWEEP(nm);
407 }
408 } else {
409 assert(nm->is_alive(), "should be alive");
410
411 if (UseCodeCacheFlushing) {
412 if ((nm->method()->code() != nm) && !(nm->is_locked_by_vm()) && !(nm->is_osr_method()) &&
413 (_traversals > _was_full_traversal+2) && (((uint)nm->compile_id()) < _highest_marked) &&
414 CodeCache::needs_flushing()) {
415 // This method has not been called since the forced cleanup happened
416 nm->make_not_entrant();
417 }
418 }
419
420 // Clean-up all inline caches that points to zombie/non-reentrant methods
421 MutexLocker cl(CompiledIC_lock);
422 nm->cleanup_inline_caches();
423 SWEEP(nm);
424 }
425 }
426
427 // Code cache unloading: when compilers notice the code cache is getting full,
428 // they will call a vm op that comes here. This code attempts to speculatively
429 // unload the oldest half of the nmethods (based on the compile job id) by
430 // saving the old code in a list in the CodeCache. Then
431 // execution resumes. If a method so marked is not called by the second sweeper
432 // stack traversal after the current one, the nmethod will be marked non-entrant and
433 // got rid of by normal sweeping. If the method is called, the methodOop's
434 // _code field is restored and the methodOop/nmethod
435 // go back to their normal state.
436 void NMethodSweeper::handle_full_code_cache(bool is_full) {
437 // Only the first one to notice can advise us to start early cleaning
438 if (!is_full){
439 jint old = Atomic::cmpxchg( 1, &_advise_to_sweep, 0 );
440 if (old != 0) {
441 return;
442 }
443 }
444
445 if (is_full) {
446 // Since code cache is full, immediately stop new compiles
447 bool did_set = CompileBroker::set_should_compile_new_jobs(CompileBroker::stop_compilation);
448 if (!did_set) {
449 // only the first to notice can start the cleaning,
450 // others will go back and block
451 return;
452 }
453 set_was_full(true);
454
455 // If we run out within MinCodeCacheFlushingInterval of the last unload time, give up
456 jlong now = os::javaTimeMillis();
457 jlong max_interval = (jlong)MinCodeCacheFlushingInterval * (jlong)1000;
458 jlong curr_interval = now - _last_was_full;
459 if (curr_interval < max_interval) {
460 _rescan = true;
461 log_sweep("disable_compiler", "flushing_interval='" UINT64_FORMAT "'",
462 curr_interval/1000);
463 return;
464 }
465 }
466
467 VM_HandleFullCodeCache op(is_full);
468 VMThread::execute(&op);
469
470 // rescan again as soon as possible
471 _rescan = true;
472 }
473
474 void NMethodSweeper::speculative_disconnect_nmethods(bool is_full) {
475 // If there was a race in detecting full code cache, only run
476 // one vm op for it or keep the compiler shut off
477
478 debug_only(jlong start = os::javaTimeMillis();)
479
480 if ((!was_full()) && (is_full)) {
481 if (!CodeCache::needs_flushing()) {
482 log_sweep("restart_compiler");
483 CompileBroker::set_should_compile_new_jobs(CompileBroker::run_compilation);
484 return;
485 }
486 }
487
488 // Traverse the code cache trying to dump the oldest nmethods
489 uint curr_max_comp_id = CompileBroker::get_compilation_id();
490 uint flush_target = ((curr_max_comp_id - _highest_marked) >> 1) + _highest_marked;
491 log_sweep("start_cleaning");
492
493 nmethod* nm = CodeCache::alive_nmethod(CodeCache::first());
494 jint disconnected = 0;
495 jint made_not_entrant = 0;
496 while ((nm != NULL)){
497 uint curr_comp_id = nm->compile_id();
498
499 // OSR methods cannot be flushed like this. Also, don't flush native methods
500 // since they are part of the JDK in most cases
501 if (nm->is_in_use() && (!nm->is_osr_method()) && (!nm->is_locked_by_vm()) &&
502 (!nm->is_native_method()) && ((curr_comp_id < flush_target))) {
503
504 if ((nm->method()->code() == nm)) {
505 // This method has not been previously considered for
506 // unloading or it was restored already
507 CodeCache::speculatively_disconnect(nm);
508 disconnected++;
509 } else if (nm->is_speculatively_disconnected()) {
510 // This method was previously considered for preemptive unloading and was not called since then
511 CompilationPolicy::policy()->delay_compilation(nm->method());
512 nm->make_not_entrant();
513 made_not_entrant++;
514 }
515
516 if (curr_comp_id > _highest_marked) {
517 _highest_marked = curr_comp_id;
518 }
519 }
520 nm = CodeCache::alive_nmethod(CodeCache::next(nm));
521 }
522
523 log_sweep("stop_cleaning",
524 "disconnected='" UINT32_FORMAT "' made_not_entrant='" UINT32_FORMAT "'",
525 disconnected, made_not_entrant);
526
527 // Shut off compiler. Sweeper will start over with a new stack scan and
528 // traversal cycle and turn it back on if it clears enough space.
529 if (was_full()) {
530 _last_was_full = os::javaTimeMillis();
531 CompileBroker::set_should_compile_new_jobs(CompileBroker::stop_compilation);
532 }
533
534 // After two more traversals the sweeper will get rid of unrestored nmethods
535 _was_full_traversal = _traversals;
536 #ifdef ASSERT
537 jlong end = os::javaTimeMillis();
538 if(PrintMethodFlushing && Verbose) {
539 tty->print_cr("### sweeper: unload time: " INT64_FORMAT, end-start);
540 }
541 #endif
542 }
543
544
545 // Print out some state information about the current sweep and the
546 // state of the code cache if it's requested.
547 void NMethodSweeper::log_sweep(const char* msg, const char* format, ...) {
548 if (PrintMethodFlushing) {
549 stringStream s;
550 // Dump code cache state into a buffer before locking the tty,
551 // because log_state() will use locks causing lock conflicts.
552 CodeCache::log_state(&s);
553
554 ttyLocker ttyl;
555 tty->print("### sweeper: %s ", msg);
556 if (format != NULL) {
557 va_list ap;
558 va_start(ap, format);
559 tty->vprint(format, ap);
560 va_end(ap);
561 }
562 tty->print_cr(s.as_string());
563 }
564
565 if (LogCompilation && (xtty != NULL)) {
566 stringStream s;
567 // Dump code cache state into a buffer before locking the tty,
568 // because log_state() will use locks causing lock conflicts.
569 CodeCache::log_state(&s);
570
571 ttyLocker ttyl;
572 xtty->begin_elem("sweeper state='%s' traversals='" INTX_FORMAT "' ", msg, (intx)traversal_count());
573 if (format != NULL) {
574 va_list ap;
575 va_start(ap, format);
576 xtty->vprint(format, ap);
577 va_end(ap);
578 }
579 xtty->print(s.as_string());
580 xtty->stamp();
581 xtty->end_elem();
582 }
583 }