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_nmethod = NULL; // Current nmethod
131 int NMethodSweeper::_current_type = 0; // Current CodeBlobType
132 long NMethodSweeper::_traversals = 0; // Nof. stack traversals performed
133 int NMethodSweeper::_seen = 0; // Nof. nmethods we have currently processed in current pass of CodeCache
134 int NMethodSweeper::_flushed_count = 0; // Nof. nmethods flushed in current sweep
135 int NMethodSweeper::_zombified_count = 0; // Nof. nmethods made zombie in current sweep
136 int NMethodSweeper::_marked_count = 0; // Nof. nmethods marked for reclaim in current sweep
137
138 volatile int NMethodSweeper::_invocations = 0; // Nof. invocations left until we are completed with this pass
139 volatile int NMethodSweeper::_sweep_started = 0; // Whether a sweep is in progress.
140
141 jint NMethodSweeper::_locked_seen = 0;
142 jint NMethodSweeper::_not_entrant_seen_on_stack = 0;
143 bool NMethodSweeper::_request_mark_phase = false;
144
145 int NMethodSweeper::_total_nof_methods_reclaimed = 0;
146 jlong NMethodSweeper::_total_time_sweeping = 0;
147 jlong NMethodSweeper::_total_time_this_sweep = 0;
148 jlong NMethodSweeper::_peak_sweep_time = 0;
149 jlong NMethodSweeper::_peak_sweep_fraction_time = 0;
150 int NMethodSweeper::_hotness_counter_reset_val = 0;
151
152
153 class MarkActivationClosure: public CodeBlobClosure {
154 public:
155 virtual void do_code_blob(CodeBlob* cb) {
156 if (cb->is_nmethod()) {
157 nmethod* nm = (nmethod*)cb;
158 nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val());
159 // If we see an activation belonging to a non_entrant nmethod, we mark it.
160 if (nm->is_not_entrant()) {
161 nm->mark_as_seen_on_stack();
162 }
163 }
164 }
165 };
166 static MarkActivationClosure mark_activation_closure;
167
168 class SetHotnessClosure: public CodeBlobClosure {
169 public:
170 virtual void do_code_blob(CodeBlob* cb) {
171 if (cb->is_nmethod()) {
172 nmethod* nm = (nmethod*)cb;
173 nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val());
174 }
175 }
176 };
177 static SetHotnessClosure set_hotness_closure;
178
179
180 int NMethodSweeper::hotness_counter_reset_val() {
181 if (_hotness_counter_reset_val == 0) {
182 _hotness_counter_reset_val = (ReservedCodeCacheSize < M) ? 1 : (ReservedCodeCacheSize / M) * 2;
183 }
184 return _hotness_counter_reset_val;
185 }
186 bool NMethodSweeper::sweep_in_progress() {
187 return (_current_nmethod != NULL);
188 }
189
190 // Scans the stacks of all Java threads and marks activations of not-entrant methods.
191 // No need to synchronize access, since 'mark_active_nmethods' is always executed at a
192 // safepoint.
193 void NMethodSweeper::mark_active_nmethods() {
194 assert(SafepointSynchronize::is_at_safepoint(), "must be executed at a safepoint");
195 // If we do not want to reclaim not-entrant or zombie methods there is no need
196 // to scan stacks
197 if (!MethodFlushing) {
198 return;
199 }
200
201 // Check for restart
202 assert(CodeCache::find_blob_unsafe(_current_nmethod) == _current_nmethod, "Sweeper nmethod cached state invalid");
203 if (!sweep_in_progress() && need_marking_phase()) {
204 _seen = 0;
205 _invocations = NmethodSweepFraction;
206 _current_nmethod = (nmethod*)CodeCache::first_blob(CodeBlobType::MethodNonProfiled);
207 _current_type = CodeBlobType::MethodNonProfiled;
208 _traversals += 1;
209 _total_time_this_sweep = 0;
210
211 if (PrintMethodFlushing) {
212 tty->print_cr("### Sweep: stack traversal %d", _traversals);
213 }
214 Threads::nmethods_do(&mark_activation_closure);
215
216 // reset the flags since we started a scan from the beginning.
217 reset_nmethod_marking();
218 _locked_seen = 0;
219 _not_entrant_seen_on_stack = 0;
220 } else {
221 // Only set hotness counter
222 Threads::nmethods_do(&set_hotness_closure);
223 }
224
225 OrderAccess::storestore();
226 }
227
228 void NMethodSweeper::possibly_sweep() {
229 assert(JavaThread::current()->thread_state() == _thread_in_vm, "must run in vm mode");
230 if (!MethodFlushing || !sweep_in_progress()) {
231 return;
232 }
233
234 if (_invocations > 0) {
235 // Only one thread at a time will sweep
236 jint old = Atomic::cmpxchg( 1, &_sweep_started, 0 );
237 if (old != 0) {
238 return;
239 }
240 #ifdef ASSERT
241 if (LogSweeper && _records == NULL) {
242 // Create the ring buffer for the logging code
243 _records = NEW_C_HEAP_ARRAY(SweeperRecord, SweeperLogEntries, mtGC);
244 memset(_records, 0, sizeof(SweeperRecord) * SweeperLogEntries);
245 }
246 #endif
247 if (_invocations > 0) {
248 sweep_code_cache();
249 _invocations--;
250 }
251 _sweep_started = 0;
252 }
253 }
254
255 void NMethodSweeper::sweep_code_cache() {
256 jlong sweep_start_counter = os::elapsed_counter();
257
258 _flushed_count = 0;
259 _zombified_count = 0;
260 _marked_count = 0;
261
262 if (PrintMethodFlushing && Verbose) {
263 tty->print_cr("### Sweep at %d out of %d. Invocations left: %d", _seen, CodeCache::nof_nmethods(), _invocations);
264 }
265
266 if (!CompileBroker::should_compile_new_jobs()) {
267 // If we have turned off compilations we might as well do full sweeps
268 // in order to reach the clean state faster. Otherwise the sleeping compiler
269 // threads will slow down sweeping.
270 _invocations = 1;
271 }
272
273 // We want to visit all nmethods after NmethodSweepFraction
274 // invocations so divide the remaining number of nmethods by the
275 // remaining number of invocations. This is only an estimate since
276 // the number of nmethods changes during the sweep so the final
277 // stage must iterate until it there are no more nmethods.
278 int todo = (CodeCache::nof_nmethods() - _seen) / _invocations;
279 int swept_count = 0;
280
281
282 assert(!SafepointSynchronize::is_at_safepoint(), "should not be in safepoint when we get here");
283 assert(!CodeCache_lock->owned_by_self(), "just checking");
284
285 int freed_memory = 0;
286 {
287 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
288
289 // The last invocation iterates until there are no more nmethods
290 while ((swept_count < todo || _invocations == 1) && _current_nmethod != NULL) {
291 swept_count++;
292 if (SafepointSynchronize::is_synchronizing()) { // Safepoint request
293 if (PrintMethodFlushing && Verbose) {
294 tty->print_cr("### Sweep at %d out of %d, invocation: %d, yielding to safepoint", _seen, CodeCache::nof_nmethods(), _invocations);
295 }
296 MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
297
298 assert(Thread::current()->is_Java_thread(), "should be java thread");
299 JavaThread* thread = (JavaThread*)Thread::current();
300 ThreadBlockInVM tbivm(thread);
301 thread->java_suspend_self();
302 }
303 // Since we will give up the CodeCache_lock, always skip ahead
304 // to the next nmethod. Other blobs can be deleted by other
305 // threads but nmethods are only reclaimed by the sweeper.
306 nmethod* next = (nmethod*)CodeCache::next_blob(_current_nmethod, _current_type);
307
308 // Now ready to process nmethod and give up CodeCache_lock
309 {
310 MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
311 freed_memory += process_nmethod(_current_nmethod, _current_type);
312 }
313 _seen++;
314
315 while (next == NULL && _current_type < CodeBlobType::MethodProfiled) {
316 // We reached the last method of the type
317 // Go to next type that has methods available
318 _current_type++;
319 next = (nmethod*)CodeCache::first_blob(_current_type);
320 }
321 _current_nmethod = next;
322 }
323 }
324
325 assert(_invocations > 1 || _current_nmethod == NULL, "must have scanned the whole cache");
326
327 if (!sweep_in_progress() && !need_marking_phase() && (_locked_seen || _not_entrant_seen_on_stack)) {
328 // we've completed a scan without making progress but there were
329 // nmethods we were unable to process either because they were
330 // locked or were still on stack. We don't have to aggressively
331 // clean them up so just stop scanning. We could scan once more
332 // but that complicates the control logic and it's unlikely to
333 // matter much.
334 if (PrintMethodFlushing) {
335 tty->print_cr("### Couldn't make progress on some nmethods so stopping sweep");
336 }
337 }
338
339 jlong sweep_end_counter = os::elapsed_counter();
340 jlong sweep_time = sweep_end_counter - sweep_start_counter;
341 _total_time_sweeping += sweep_time;
342 _total_time_this_sweep += sweep_time;
343 _peak_sweep_fraction_time = MAX2(sweep_time, _peak_sweep_fraction_time);
344 _total_nof_methods_reclaimed += _flushed_count;
345
346 EventSweepCodeCache event(UNTIMED);
347 if (event.should_commit()) {
348 event.set_starttime(sweep_start_counter);
349 event.set_endtime(sweep_end_counter);
350 event.set_sweepIndex(_traversals);
351 event.set_sweepFractionIndex(NmethodSweepFraction - _invocations + 1);
352 event.set_sweptCount(swept_count);
353 event.set_flushedCount(_flushed_count);
354 event.set_markedCount(_marked_count);
355 event.set_zombifiedCount(_zombified_count);
356 event.commit();
357 }
358
359 #ifdef ASSERT
360 if(PrintMethodFlushing) {
361 tty->print_cr("### sweeper: sweep time(%d): " INT64_FORMAT, _invocations, (jlong)sweep_time);
362 }
363 #endif
364
365 if (_invocations == 1) {
366 _peak_sweep_time = MAX2(_peak_sweep_time, _total_time_this_sweep);
367 log_sweep("finished");
368 }
369
370 // Sweeper is the only case where memory is released, check here if it
371 // is time to restart the compiler. Only checking if there is a certain
372 // amount of free memory in the code cache might lead to re-enabling
373 // compilation although no memory has been released. For example, there are
374 // cases when compilation was disabled although there is 4MB (or more) free
375 // memory in the code cache. The reason is code cache fragmentation. Therefore,
376 // it only makes sense to re-enable compilation if we have actually freed memory.
377 // Note that typically several kB are released for sweeping 16MB of the code
378 // cache. As a result, 'freed_memory' > 0 to restart the compiler.
379 if (UseCodeCacheFlushing && (!CompileBroker::should_compile_new_jobs() && (freed_memory > 0))) {
380 CompileBroker::set_should_compile_new_jobs(CompileBroker::run_compilation);
381 log_sweep("restart_compiler");
382 }
383 }
384
385 class NMethodMarker: public StackObj {
386 private:
387 CompilerThread* _thread;
388 public:
389 NMethodMarker(nmethod* nm) {
390 _thread = CompilerThread::current();
391 if (!nm->is_zombie() && !nm->is_unloaded()) {
392 // Only expose live nmethods for scanning
393 _thread->set_scanned_nmethod(nm);
394 }
395 }
396 ~NMethodMarker() {
397 _thread->set_scanned_nmethod(NULL);
398 }
399 };
400
401 void NMethodSweeper::release_nmethod(nmethod *nm) {
402 // Clean up any CompiledICHolders
403 {
404 ResourceMark rm;
405 MutexLocker ml_patch(CompiledIC_lock);
406 RelocIterator iter(nm);
407 while (iter.next()) {
408 if (iter.type() == relocInfo::virtual_call_type) {
409 CompiledIC::cleanup_call_site(iter.virtual_call_reloc());
410 }
411 }
412 }
413
414 MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
415 nm->flush();
416 }
417
418 int NMethodSweeper::process_nmethod(nmethod *nm, int code_blob_type) {
419 assert(!CodeCache_lock->owned_by_self(), "just checking");
420
421 int freed_memory = 0;
422 // Make sure this nmethod doesn't get unloaded during the scan,
423 // since safepoints may happen during acquired below locks.
424 NMethodMarker nmm(nm);
425 SWEEP(nm);
426
427 // Skip methods that are currently referenced by the VM
428 if (nm->is_locked_by_vm()) {
429 // But still remember to clean-up inline caches for alive nmethods
430 if (nm->is_alive()) {
431 // Clean inline caches that point to zombie/non-entrant methods
432 MutexLocker cl(CompiledIC_lock);
433 nm->cleanup_inline_caches();
434 SWEEP(nm);
435 } else {
436 _locked_seen++;
437 SWEEP(nm);
438 }
439 return freed_memory;
440 }
441
442 if (nm->is_zombie()) {
443 // If it is the first time we see nmethod then we mark it. Otherwise,
444 // we reclaim it. When we have seen a zombie method twice, we know that
445 // there are no inline caches that refer to it.
446 if (nm->is_marked_for_reclamation()) {
447 assert(!nm->is_locked_by_vm(), "must not flush locked nmethods");
448 if (PrintMethodFlushing && Verbose) {
449 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (marked for reclamation) being flushed", nm->compile_id(), nm);
450 }
451 freed_memory = nm->total_size();
452 release_nmethod(nm);
453 _flushed_count++;
454 } else {
455 if (PrintMethodFlushing && Verbose) {
456 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (zombie) being marked for reclamation", nm->compile_id(), nm);
457 }
458 nm->mark_for_reclamation();
459 request_nmethod_marking();
460 _marked_count++;
461 SWEEP(nm);
462 }
463 } else if (nm->is_not_entrant()) {
464 // If there are no current activations of this method on the
465 // stack we can safely convert it to a zombie method
466 if (nm->can_not_entrant_be_converted()) {
467 if (PrintMethodFlushing && Verbose) {
468 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (not entrant) being made zombie", nm->compile_id(), nm);
469 }
470 nm->make_zombie();
471 request_nmethod_marking();
472 _zombified_count++;
473 SWEEP(nm);
474 } else {
475 // Still alive, clean up its inline caches
476 MutexLocker cl(CompiledIC_lock);
477 nm->cleanup_inline_caches();
478 // we coudn't transition this nmethod so don't immediately
479 // request a rescan. If this method stays on the stack for a
480 // long time we don't want to keep rescanning the code cache.
481 _not_entrant_seen_on_stack++;
482 SWEEP(nm);
483 }
484 } else if (nm->is_unloaded()) {
485 // Unloaded code, just make it a zombie
486 if (PrintMethodFlushing && Verbose) {
487 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (unloaded) being made zombie", nm->compile_id(), nm);
488 }
489 if (nm->is_osr_method()) {
490 SWEEP(nm);
491 // No inline caches will ever point to osr methods, so we can just remove it
492 freed_memory = nm->total_size();
493 release_nmethod(nm);
494 _flushed_count++;
495 } else {
496 nm->make_zombie();
497 request_nmethod_marking();
498 _zombified_count++;
499 SWEEP(nm);
500 }
501 } else {
502 if (UseCodeCacheFlushing) {
503 if (!nm->is_locked_by_vm() && !nm->is_osr_method() && !nm->is_native_method()) {
504 // Do not make native methods and OSR-methods not-entrant
505 nm->dec_hotness_counter();
506 // Get the initial value of the hotness counter. This value depends on the
507 // ReservedCodeCacheSize
508 int reset_val = hotness_counter_reset_val();
509 int time_since_reset = reset_val - nm->hotness_counter();
510 double threshold = -reset_val + (CodeCache::reverse_free_ratio(code_blob_type) * NmethodSweepActivity);
511 // The less free space in the code cache we have - the bigger reverse_free_ratio() is.
512 // I.e., 'threshold' increases with lower available space in the code cache and a higher
513 // NmethodSweepActivity. If the current hotness counter - which decreases from its initial
514 // value until it is reset by stack walking - is smaller than the computed threshold, the
515 // corresponding nmethod is considered for removal.
516 if ((NmethodSweepActivity > 0) && (nm->hotness_counter() < threshold) && (time_since_reset > 10)) {
517 // A method is marked as not-entrant if the method is
518 // 1) 'old enough': nm->hotness_counter() < threshold
519 // 2) The method was in_use for a minimum amount of time: (time_since_reset > 10)
520 // The second condition is necessary if we are dealing with very small code cache
521 // sizes (e.g., <10m) and the code cache size is too small to hold all hot methods.
522 // The second condition ensures that methods are not immediately made not-entrant
523 // after compilation.
524 nm->make_not_entrant();
525 request_nmethod_marking();
526 }
527 }
528 }
529 // Clean-up all inline caches that point to zombie/non-reentrant methods
530 MutexLocker cl(CompiledIC_lock);
531 nm->cleanup_inline_caches();
532 SWEEP(nm);
533 }
534 return freed_memory;
535 }
536
537 // Print out some state information about the current sweep and the
538 // state of the code cache if it's requested.
539 void NMethodSweeper::log_sweep(const char* msg, const char* format, ...) {
540 if (PrintMethodFlushing) {
541 stringStream s;
542 // Dump code cache state into a buffer before locking the tty,
543 // because log_state() will use locks causing lock conflicts.
544 CodeCache::log_state(&s);
545
546 ttyLocker ttyl;
547 tty->print("### sweeper: %s ", msg);
548 if (format != NULL) {
549 va_list ap;
550 va_start(ap, format);
551 tty->vprint(format, ap);
552 va_end(ap);
553 }
554 tty->print_cr(s.as_string());
555 }
556
557 if (LogCompilation && (xtty != NULL)) {
558 stringStream s;
559 // Dump code cache state into a buffer before locking the tty,
560 // because log_state() will use locks causing lock conflicts.
561 CodeCache::log_state(&s);
562
563 ttyLocker ttyl;
564 xtty->begin_elem("sweeper state='%s' traversals='" INTX_FORMAT "' ", msg, (intx)traversal_count());
565 if (format != NULL) {
566 va_list ap;
567 va_start(ap, format);
568 xtty->vprint(format, ap);
569 va_end(ap);
570 }
571 xtty->print(s.as_string());
572 xtty->stamp();
573 xtty->end_elem();
574 }
575 }