1 /*
2 * Copyright (c) 1997, 2011, 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 uint _sweep_index = 0;
72 static SweeperRecord* _records = NULL;
73
74 void NMethodSweeper::report_events(int id, address entry) {
75 if (_records != NULL) {
76 for (uint 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 (uint 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 (uint i = _sweep_index; i < SweeperLogEntries; i++) {
96 // skip empty records
97 if (_records[i].vep == NULL) continue;
98 _records[i].print();
99 }
100 for (uint 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
270 // Since we will give up the CodeCache_lock, always skip ahead
271 // to the next nmethod. Other blobs can be deleted by other
272 // threads but nmethods are only reclaimed by the sweeper.
273 nmethod* next = CodeCache::next_nmethod(_current);
274
275 // Now ready to process nmethod and give up CodeCache_lock
276 {
277 MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
278 process_nmethod(_current);
279 }
280 _seen++;
281 _current = next;
282 }
283 }
284
285 assert(_invocations > 1 || _current == NULL, "must have scanned the whole cache");
286
287 if (_current == NULL && !_rescan && (_locked_seen || _not_entrant_seen_on_stack)) {
288 // we've completed a scan without making progress but there were
289 // nmethods we were unable to process either because they were
290 // locked or were still on stack. We don't have to aggresively
291 // clean them up so just stop scanning. We could scan once more
292 // but that complicates the control logic and it's unlikely to
293 // matter much.
294 if (PrintMethodFlushing) {
295 tty->print_cr("### Couldn't make progress on some nmethods so stopping sweep");
296 }
297 }
298
299 #ifdef ASSERT
300 if(PrintMethodFlushing) {
301 jlong sweep_end = os::javaTimeMillis();
302 tty->print_cr("### sweeper: sweep time(%d): " INT64_FORMAT, _invocations, sweep_end - sweep_start);
303 }
304 #endif
305
306 if (_invocations == 1) {
307 log_sweep("finished");
308 }
309 }
310
311 class NMethodMarker: public StackObj {
312 private:
313 CompilerThread* _thread;
314 public:
315 NMethodMarker(nmethod* nm) {
316 _thread = CompilerThread::current();
317 _thread->set_scanned_nmethod(nm);
318 }
319 ~NMethodMarker() {
320 _thread->set_scanned_nmethod(NULL);
321 }
322 };
323
324
325 void NMethodSweeper::process_nmethod(nmethod *nm) {
326 assert(!CodeCache_lock->owned_by_self(), "just checking");
327
328 // Make sure this nmethod doesn't get unloaded during the scan,
329 // since the locks acquired below might safepoint.
330 NMethodMarker nmm(nm);
331
332 SWEEP(nm);
333
334 // Skip methods that are currently referenced by the VM
335 if (nm->is_locked_by_vm()) {
336 // But still remember to clean-up inline caches for alive nmethods
337 if (nm->is_alive()) {
338 // Clean-up all inline caches that points to zombie/non-reentrant methods
339 MutexLocker cl(CompiledIC_lock);
340 nm->cleanup_inline_caches();
341 SWEEP(nm);
342 } else {
343 _locked_seen++;
344 SWEEP(nm);
345 }
346 return;
347 }
348
349 if (nm->is_zombie()) {
350 // If it is first time, we see nmethod then we mark it. Otherwise,
351 // we reclame it. When we have seen a zombie method twice, we know that
352 // there are no inline caches that refer to it.
353 if (nm->is_marked_for_reclamation()) {
354 assert(!nm->is_locked_by_vm(), "must not flush locked nmethods");
355 if (PrintMethodFlushing && Verbose) {
356 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (marked for reclamation) being flushed", nm->compile_id(), nm);
357 }
358 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
359 nm->flush();
360 } else {
361 if (PrintMethodFlushing && Verbose) {
362 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (zombie) being marked for reclamation", nm->compile_id(), nm);
363 }
364 nm->mark_for_reclamation();
365 _rescan = true;
366 SWEEP(nm);
367 }
368 } else if (nm->is_not_entrant()) {
369 // If there is no current activations of this method on the
370 // stack we can safely convert it to a zombie method
371 if (nm->can_not_entrant_be_converted()) {
372 if (PrintMethodFlushing && Verbose) {
373 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (not entrant) being made zombie", nm->compile_id(), nm);
374 }
375 nm->make_zombie();
376 _rescan = true;
377 SWEEP(nm);
378 } else {
379 // Still alive, clean up its inline caches
380 MutexLocker cl(CompiledIC_lock);
381 nm->cleanup_inline_caches();
382 // we coudn't transition this nmethod so don't immediately
383 // request a rescan. If this method stays on the stack for a
384 // long time we don't want to keep rescanning the code cache.
385 _not_entrant_seen_on_stack++;
386 SWEEP(nm);
387 }
388 } else if (nm->is_unloaded()) {
389 // Unloaded code, just make it a zombie
390 if (PrintMethodFlushing && Verbose)
391 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (unloaded) being made zombie", nm->compile_id(), nm);
392 if (nm->is_osr_method()) {
393 // No inline caches will ever point to osr methods, so we can just remove it
394 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
395 SWEEP(nm);
396 nm->flush();
397 } else {
398 nm->make_zombie();
399 _rescan = true;
400 SWEEP(nm);
401 }
402 } else {
403 assert(nm->is_alive(), "should be alive");
404
405 if (UseCodeCacheFlushing) {
406 if ((nm->method()->code() != nm) && !(nm->is_locked_by_vm()) && !(nm->is_osr_method()) &&
407 (_traversals > _was_full_traversal+2) && (((uint)nm->compile_id()) < _highest_marked) &&
408 CodeCache::needs_flushing()) {
409 // This method has not been called since the forced cleanup happened
410 nm->make_not_entrant();
411 }
412 }
413
414 // Clean-up all inline caches that points to zombie/non-reentrant methods
415 MutexLocker cl(CompiledIC_lock);
416 nm->cleanup_inline_caches();
417 SWEEP(nm);
418 }
419 }
420
421 // Code cache unloading: when compilers notice the code cache is getting full,
422 // they will call a vm op that comes here. This code attempts to speculatively
423 // unload the oldest half of the nmethods (based on the compile job id) by
424 // saving the old code in a list in the CodeCache. Then
425 // execution resumes. If a method so marked is not called by the second sweeper
426 // stack traversal after the current one, the nmethod will be marked non-entrant and
427 // got rid of by normal sweeping. If the method is called, the methodOop's
428 // _code field is restored and the methodOop/nmethod
429 // go back to their normal state.
430 void NMethodSweeper::handle_full_code_cache(bool is_full) {
431 // Only the first one to notice can advise us to start early cleaning
432 if (!is_full){
433 jint old = Atomic::cmpxchg( 1, &_advise_to_sweep, 0 );
434 if (old != 0) {
435 return;
436 }
437 }
438
439 if (is_full) {
440 // Since code cache is full, immediately stop new compiles
441 bool did_set = CompileBroker::set_should_compile_new_jobs(CompileBroker::stop_compilation);
442 if (!did_set) {
443 // only the first to notice can start the cleaning,
444 // others will go back and block
445 return;
446 }
447 set_was_full(true);
448
449 // If we run out within MinCodeCacheFlushingInterval of the last unload time, give up
450 jlong now = os::javaTimeMillis();
451 jlong max_interval = (jlong)MinCodeCacheFlushingInterval * (jlong)1000;
452 jlong curr_interval = now - _last_was_full;
453 if (curr_interval < max_interval) {
454 _rescan = true;
455 log_sweep("disable_compiler", "flushing_interval='" UINT64_FORMAT "'",
456 curr_interval/1000);
457 return;
458 }
459 }
460
461 VM_HandleFullCodeCache op(is_full);
462 VMThread::execute(&op);
463
464 // rescan again as soon as possible
465 _rescan = true;
466 }
467
468 void NMethodSweeper::speculative_disconnect_nmethods(bool is_full) {
469 // If there was a race in detecting full code cache, only run
470 // one vm op for it or keep the compiler shut off
471
472 debug_only(jlong start = os::javaTimeMillis();)
473
474 if ((!was_full()) && (is_full)) {
475 if (!CodeCache::needs_flushing()) {
476 log_sweep("restart_compiler");
477 CompileBroker::set_should_compile_new_jobs(CompileBroker::run_compilation);
478 return;
479 }
480 }
481
482 // Traverse the code cache trying to dump the oldest nmethods
483 uint curr_max_comp_id = CompileBroker::get_compilation_id();
484 uint flush_target = ((curr_max_comp_id - _highest_marked) >> 1) + _highest_marked;
485 log_sweep("start_cleaning");
486
487 nmethod* nm = CodeCache::alive_nmethod(CodeCache::first());
488 jint disconnected = 0;
489 jint made_not_entrant = 0;
490 while ((nm != NULL)){
491 uint curr_comp_id = nm->compile_id();
492
493 // OSR methods cannot be flushed like this. Also, don't flush native methods
494 // since they are part of the JDK in most cases
495 if (nm->is_in_use() && (!nm->is_osr_method()) && (!nm->is_locked_by_vm()) &&
496 (!nm->is_native_method()) && ((curr_comp_id < flush_target))) {
497
498 if ((nm->method()->code() == nm)) {
499 // This method has not been previously considered for
500 // unloading or it was restored already
501 CodeCache::speculatively_disconnect(nm);
502 disconnected++;
503 } else if (nm->is_speculatively_disconnected()) {
504 // This method was previously considered for preemptive unloading and was not called since then
505 CompilationPolicy::policy()->delay_compilation(nm->method());
506 nm->make_not_entrant();
507 made_not_entrant++;
508 }
509
510 if (curr_comp_id > _highest_marked) {
511 _highest_marked = curr_comp_id;
512 }
513 }
514 nm = CodeCache::alive_nmethod(CodeCache::next(nm));
515 }
516
517 log_sweep("stop_cleaning",
518 "disconnected='" UINT32_FORMAT "' made_not_entrant='" UINT32_FORMAT "'",
519 disconnected, made_not_entrant);
520
521 // Shut off compiler. Sweeper will start over with a new stack scan and
522 // traversal cycle and turn it back on if it clears enough space.
523 if (was_full()) {
524 _last_was_full = os::javaTimeMillis();
525 CompileBroker::set_should_compile_new_jobs(CompileBroker::stop_compilation);
526 }
527
528 // After two more traversals the sweeper will get rid of unrestored nmethods
529 _was_full_traversal = _traversals;
530 #ifdef ASSERT
531 jlong end = os::javaTimeMillis();
532 if(PrintMethodFlushing && Verbose) {
533 tty->print_cr("### sweeper: unload time: " INT64_FORMAT, end-start);
534 }
535 #endif
536 }
537
538
539 // Print out some state information about the current sweep and the
540 // state of the code cache if it's requested.
541 void NMethodSweeper::log_sweep(const char* msg, const char* format, ...) {
542 if (PrintMethodFlushing) {
543 stringStream s;
544 // Dump code cache state into a buffer before locking the tty,
545 // because log_state() will use locks causing lock conflicts.
546 CodeCache::log_state(&s);
547
548 ttyLocker ttyl;
549 tty->print("### sweeper: %s ", msg);
550 if (format != NULL) {
551 va_list ap;
552 va_start(ap, format);
553 tty->vprint(format, ap);
554 va_end(ap);
555 }
556 tty->print_cr(s.as_string());
557 }
558
559 if (LogCompilation && (xtty != NULL)) {
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 xtty->begin_elem("sweeper state='%s' traversals='" INTX_FORMAT "' ", msg, (intx)traversal_count());
567 if (format != NULL) {
568 va_list ap;
569 va_start(ap, format);
570 xtty->vprint(format, ap);
571 va_end(ap);
572 }
573 xtty->print(s.as_string());
574 xtty->stamp();
575 xtty->end_elem();
576 }
577 }