1 /*
2 * Copyright (c) 2012, 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 #include "precompiled.hpp"
25
26 #include "oops/instanceKlass.hpp"
27 #include "runtime/atomic.hpp"
28 #include "runtime/interfaceSupport.hpp"
29 #include "runtime/mutexLocker.hpp"
30 #include "runtime/safepoint.hpp"
31 #include "runtime/threadCritical.hpp"
32 #include "runtime/vm_operations.hpp"
33 #include "services/memPtr.hpp"
34 #include "services/memReporter.hpp"
35 #include "services/memTracker.hpp"
36 #include "utilities/decoder.hpp"
37 #include "utilities/defaultStream.hpp"
38 #include "utilities/globalDefinitions.hpp"
39
40 bool NMT_track_callsite = false;
41
42 // walk all 'known' threads at NMT sync point, and collect their recorders
43 void SyncThreadRecorderClosure::do_thread(Thread* thread) {
44 assert(SafepointSynchronize::is_at_safepoint(), "Safepoint required");
45 if (thread->is_Java_thread()) {
46 JavaThread* javaThread = (JavaThread*)thread;
47 MemRecorder* recorder = javaThread->get_recorder();
48 if (recorder != NULL) {
49 MemTracker::enqueue_pending_recorder(recorder);
50 javaThread->set_recorder(NULL);
51 }
52 }
53 _thread_count ++;
54 }
55
56
57 MemRecorder* volatile MemTracker::_global_recorder = NULL;
58 MemSnapshot* MemTracker::_snapshot = NULL;
59 MemBaseline MemTracker::_baseline;
60 Mutex* MemTracker::_query_lock = NULL;
61 MemRecorder* volatile MemTracker::_merge_pending_queue = NULL;
62 MemRecorder* volatile MemTracker::_pooled_recorders = NULL;
63 MemTrackWorker* MemTracker::_worker_thread = NULL;
64 int MemTracker::_sync_point_skip_count = 0;
65 MemTracker::NMTLevel MemTracker::_tracking_level = MemTracker::NMT_off;
66 volatile MemTracker::NMTStates MemTracker::_state = NMT_uninited;
67 MemTracker::ShutdownReason MemTracker::_reason = NMT_shutdown_none;
68 int MemTracker::_thread_count = 255;
69 volatile jint MemTracker::_pooled_recorder_count = 0;
70 volatile unsigned long MemTracker::_processing_generation = 0;
71 volatile bool MemTracker::_worker_thread_idle = false;
72 volatile jint MemTracker::_pending_op_count = 0;
73 volatile bool MemTracker::_slowdown_calling_thread = false;
74 debug_only(intx MemTracker::_main_thread_tid = 0;)
75 NOT_PRODUCT(volatile jint MemTracker::_pending_recorder_count = 0;)
76
77 void MemTracker::init_tracking_options(const char* option_line) {
78 _tracking_level = NMT_off;
79 if (strcmp(option_line, "=summary") == 0) {
80 _tracking_level = NMT_summary;
81 } else if (strcmp(option_line, "=detail") == 0) {
82 // detail relies on a stack-walking ability that may not
83 // be available depending on platform and/or compiler flags
84 #if PLATFORM_NATIVE_STACK_WALKING_SUPPORTED
85 _tracking_level = NMT_detail;
86 #else
87 jio_fprintf(defaultStream::error_stream(),
88 "NMT detail is not supported on this platform. Using NMT summary instead.\n");
89 _tracking_level = NMT_summary;
90 #endif
91 } else if (strcmp(option_line, "=off") != 0) {
92 vm_exit_during_initialization("Syntax error, expecting -XX:NativeMemoryTracking=[off|summary|detail]", NULL);
93 }
94 }
95
96 // first phase of bootstrapping, when VM is still in single-threaded mode.
97 void MemTracker::bootstrap_single_thread() {
98 if (_tracking_level > NMT_off) {
99 assert(_state == NMT_uninited, "wrong state");
100
101 // NMT is not supported with UseMallocOnly is on. NMT can NOT
102 // handle the amount of malloc data without significantly impacting
103 // runtime performance when this flag is on.
104 if (UseMallocOnly) {
105 shutdown(NMT_use_malloc_only);
106 return;
107 }
108
109 _query_lock = new (std::nothrow) Mutex(Monitor::max_nonleaf, "NMT_queryLock");
110 if (_query_lock == NULL) {
111 shutdown(NMT_out_of_memory);
112 return;
113 }
114
115 debug_only(_main_thread_tid = os::current_thread_id();)
116 _state = NMT_bootstrapping_single_thread;
117 NMT_track_callsite = (_tracking_level == NMT_detail && can_walk_stack());
118 }
119 }
120
121 // second phase of bootstrapping, when VM is about to or already entered multi-theaded mode.
122 void MemTracker::bootstrap_multi_thread() {
123 if (_tracking_level > NMT_off && _state == NMT_bootstrapping_single_thread) {
124 // create nmt lock for multi-thread execution
125 assert(_main_thread_tid == os::current_thread_id(), "wrong thread");
126 _state = NMT_bootstrapping_multi_thread;
127 NMT_track_callsite = (_tracking_level == NMT_detail && can_walk_stack());
128 }
129 }
130
131 // fully start nmt
132 void MemTracker::start() {
133 // Native memory tracking is off from command line option
134 if (_tracking_level == NMT_off || shutdown_in_progress()) return;
135
136 assert(_main_thread_tid == os::current_thread_id(), "wrong thread");
137 assert(_state == NMT_bootstrapping_multi_thread, "wrong state");
138
139 _snapshot = new (std::nothrow)MemSnapshot();
140 if (_snapshot != NULL) {
141 if (!_snapshot->out_of_memory() && start_worker(_snapshot)) {
142 _state = NMT_started;
143 NMT_track_callsite = (_tracking_level == NMT_detail && can_walk_stack());
144 return;
145 }
146
147 delete _snapshot;
148 _snapshot = NULL;
149 }
150
151 // fail to start native memory tracking, shut it down
152 shutdown(NMT_initialization);
153 }
154
155 /**
156 * Shutting down native memory tracking.
157 * We can not shutdown native memory tracking immediately, so we just
158 * setup shutdown pending flag, every native memory tracking component
159 * should orderly shut itself down.
160 *
161 * The shutdown sequences:
162 * 1. MemTracker::shutdown() sets MemTracker to shutdown pending state
163 * 2. Worker thread calls MemTracker::final_shutdown(), which transites
164 * MemTracker to final shutdown state.
165 * 3. At sync point, MemTracker does final cleanup, before sets memory
166 * tracking level to off to complete shutdown.
167 */
168 void MemTracker::shutdown(ShutdownReason reason) {
169 if (_tracking_level == NMT_off) return;
170
171 if (_state <= NMT_bootstrapping_single_thread) {
172 // we still in single thread mode, there is not contention
173 _state = NMT_shutdown_pending;
174 _reason = reason;
175 } else {
176 // we want to know who initialized shutdown
177 if ((jint)NMT_started == Atomic::cmpxchg((jint)NMT_shutdown_pending,
178 (jint*)&_state, (jint)NMT_started)) {
179 _reason = reason;
180 }
181 }
182 }
183
184 // final phase of shutdown
185 void MemTracker::final_shutdown() {
186 // delete all pending recorders and pooled recorders
187 delete_all_pending_recorders();
188 delete_all_pooled_recorders();
189
190 {
191 // shared baseline and snapshot are the only objects needed to
192 // create query results
193 MutexLockerEx locker(_query_lock, true);
194 // cleanup baseline data and snapshot
195 _baseline.clear();
196 delete _snapshot;
197 _snapshot = NULL;
198 }
199
200 // shutdown shared decoder instance, since it is only
201 // used by native memory tracking so far.
202 Decoder::shutdown();
203
204 MemTrackWorker* worker = NULL;
205 {
206 ThreadCritical tc;
207 // can not delete worker inside the thread critical
208 if (_worker_thread != NULL && Thread::current() == _worker_thread) {
209 worker = _worker_thread;
210 _worker_thread = NULL;
211 }
212 }
213 if (worker != NULL) {
214 delete worker;
215 }
216 _state = NMT_final_shutdown;
217 }
218
219 // delete all pooled recorders
220 void MemTracker::delete_all_pooled_recorders() {
221 // free all pooled recorders
222 MemRecorder* volatile cur_head = _pooled_recorders;
223 if (cur_head != NULL) {
224 MemRecorder* null_ptr = NULL;
225 while (cur_head != NULL && (void*)cur_head != Atomic::cmpxchg_ptr((void*)null_ptr,
226 (void*)&_pooled_recorders, (void*)cur_head)) {
227 cur_head = _pooled_recorders;
228 }
229 if (cur_head != NULL) {
230 delete cur_head;
231 _pooled_recorder_count = 0;
232 }
233 }
234 }
235
236 // delete all recorders in pending queue
237 void MemTracker::delete_all_pending_recorders() {
238 // free all pending recorders
239 MemRecorder* pending_head = get_pending_recorders();
240 if (pending_head != NULL) {
241 delete pending_head;
242 }
243 }
244
245 /*
246 * retrieve per-thread recorder of specified thread.
247 * if thread == NULL, it means global recorder
248 */
249 MemRecorder* MemTracker::get_thread_recorder(JavaThread* thread) {
250 if (shutdown_in_progress()) return NULL;
251
252 MemRecorder* rc;
253 if (thread == NULL) {
254 rc = _global_recorder;
255 } else {
256 rc = thread->get_recorder();
257 }
258
259 if (rc != NULL && rc->is_full()) {
260 enqueue_pending_recorder(rc);
261 rc = NULL;
262 }
263
264 if (rc == NULL) {
265 rc = get_new_or_pooled_instance();
266 if (thread == NULL) {
267 _global_recorder = rc;
268 } else {
269 thread->set_recorder(rc);
270 }
271 }
272 return rc;
273 }
274
275 /*
276 * get a per-thread recorder from pool, or create a new one if
277 * there is not one available.
278 */
279 MemRecorder* MemTracker::get_new_or_pooled_instance() {
280 MemRecorder* cur_head = const_cast<MemRecorder*> (_pooled_recorders);
281 if (cur_head == NULL) {
282 MemRecorder* rec = new (std::nothrow)MemRecorder();
283 if (rec == NULL || rec->out_of_memory()) {
284 shutdown(NMT_out_of_memory);
285 if (rec != NULL) {
286 delete rec;
287 rec = NULL;
288 }
289 }
290 return rec;
291 } else {
292 MemRecorder* next_head = cur_head->next();
293 if ((void*)cur_head != Atomic::cmpxchg_ptr((void*)next_head, (void*)&_pooled_recorders,
294 (void*)cur_head)) {
295 return get_new_or_pooled_instance();
296 }
297 cur_head->set_next(NULL);
298 Atomic::dec(&_pooled_recorder_count);
299 cur_head->set_generation();
300 return cur_head;
301 }
302 }
303
304 /*
305 * retrieve all recorders in pending queue, and empty the queue
306 */
307 MemRecorder* MemTracker::get_pending_recorders() {
308 MemRecorder* cur_head = const_cast<MemRecorder*>(_merge_pending_queue);
309 MemRecorder* null_ptr = NULL;
310 while ((void*)cur_head != Atomic::cmpxchg_ptr((void*)null_ptr, (void*)&_merge_pending_queue,
311 (void*)cur_head)) {
312 cur_head = const_cast<MemRecorder*>(_merge_pending_queue);
313 }
314 NOT_PRODUCT(Atomic::store(0, &_pending_recorder_count));
315 return cur_head;
316 }
317
318 /*
319 * release a recorder to recorder pool.
320 */
321 void MemTracker::release_thread_recorder(MemRecorder* rec) {
322 assert(rec != NULL, "null recorder");
323 // we don't want to pool too many recorders
324 rec->set_next(NULL);
325 if (shutdown_in_progress() || _pooled_recorder_count > _thread_count * 2) {
326 delete rec;
327 return;
328 }
329
330 rec->clear();
331 MemRecorder* cur_head = const_cast<MemRecorder*>(_pooled_recorders);
332 rec->set_next(cur_head);
333 while ((void*)cur_head != Atomic::cmpxchg_ptr((void*)rec, (void*)&_pooled_recorders,
334 (void*)cur_head)) {
335 cur_head = const_cast<MemRecorder*>(_pooled_recorders);
336 rec->set_next(cur_head);
337 }
338 Atomic::inc(&_pooled_recorder_count);
339 }
340
341 // write a record to proper recorder. No lock can be taken from this method
342 // down.
343 void MemTracker::write_tracking_record(address addr, MEMFLAGS flags,
344 size_t size, jint seq, address pc, JavaThread* thread) {
345
346 MemRecorder* rc = get_thread_recorder(thread);
347 if (rc != NULL) {
348 rc->record(addr, flags, size, seq, pc);
349 }
350 }
351
352 /**
353 * enqueue a recorder to pending queue
354 */
355 void MemTracker::enqueue_pending_recorder(MemRecorder* rec) {
356 assert(rec != NULL, "null recorder");
357
358 // we are shutting down, so just delete it
359 if (shutdown_in_progress()) {
360 rec->set_next(NULL);
361 delete rec;
362 return;
363 }
364
365 MemRecorder* cur_head = const_cast<MemRecorder*>(_merge_pending_queue);
366 rec->set_next(cur_head);
367 while ((void*)cur_head != Atomic::cmpxchg_ptr((void*)rec, (void*)&_merge_pending_queue,
368 (void*)cur_head)) {
369 cur_head = const_cast<MemRecorder*>(_merge_pending_queue);
370 rec->set_next(cur_head);
371 }
372 NOT_PRODUCT(Atomic::inc(&_pending_recorder_count);)
373 }
374
375 /*
376 * The method is called at global safepoint
377 * during it synchronization process.
378 * 1. enqueue all JavaThreads' per-thread recorders
379 * 2. enqueue global recorder
380 * 3. retrieve all pending recorders
381 * 4. reset global sequence number generator
382 * 5. call worker's sync
383 */
384 #define MAX_SAFEPOINTS_TO_SKIP 128
385 #define SAFE_SEQUENCE_THRESHOLD 30
386 #define HIGH_GENERATION_THRESHOLD 60
387 #define MAX_RECORDER_THREAD_RATIO 30
388 #define MAX_RECORDER_PER_THREAD 100
389
390 void MemTracker::sync() {
391 assert(_tracking_level > NMT_off, "NMT is not enabled");
392 assert(SafepointSynchronize::is_at_safepoint(), "Safepoint required");
393
394 // Some GC tests hit large number of safepoints in short period of time
395 // without meaningful activities. We should prevent going to
396 // sync point in these cases, which can potentially exhaust generation buffer.
397 // Here is the factots to determine if we should go into sync point:
398 // 1. not to overflow sequence number
399 // 2. if we are in danger to overflow generation buffer
400 // 3. how many safepoints we already skipped sync point
401 if (_state == NMT_started) {
402 // worker thread is not ready, no one can manage generation
403 // buffer, so skip this safepoint
404 if (_worker_thread == NULL) return;
405
406 if (_sync_point_skip_count < MAX_SAFEPOINTS_TO_SKIP) {
407 int per_seq_in_use = SequenceGenerator::peek() * 100 / max_jint;
408 int per_gen_in_use = _worker_thread->generations_in_use() * 100 / MAX_GENERATIONS;
409 if (per_seq_in_use < SAFE_SEQUENCE_THRESHOLD && per_gen_in_use >= HIGH_GENERATION_THRESHOLD) {
410 _sync_point_skip_count ++;
411 return;
412 }
413 }
414 {
415 // This method is running at safepoint, with ThreadCritical lock,
416 // it should guarantee that NMT is fully sync-ed.
417 ThreadCritical tc;
418
419 // We can NOT execute NMT sync-point if there are pending tracking ops.
420 if (_pending_op_count == 0) {
421 SequenceGenerator::reset();
422 _sync_point_skip_count = 0;
423
424 // walk all JavaThreads to collect recorders
425 SyncThreadRecorderClosure stc;
426 Threads::threads_do(&stc);
427
428 _thread_count = stc.get_thread_count();
429 MemRecorder* pending_recorders = get_pending_recorders();
430
431 if (_global_recorder != NULL) {
432 _global_recorder->set_next(pending_recorders);
433 pending_recorders = _global_recorder;
434 _global_recorder = NULL;
435 }
436
437 // see if NMT has too many outstanding recorder instances, it usually
438 // means that worker thread is lagging behind in processing them.
439 if (!AutoShutdownNMT) {
440 _slowdown_calling_thread = (MemRecorder::_instance_count > MAX_RECORDER_THREAD_RATIO * _thread_count);
441 } else {
442 // If auto shutdown is on, enforce MAX_RECORDER_PER_THREAD threshold to prevent OOM
443 if (MemRecorder::_instance_count >= _thread_count * MAX_RECORDER_PER_THREAD) {
444 shutdown(NMT_out_of_memory);
445 }
446 }
447
448 // check _worker_thread with lock to avoid racing condition
449 if (_worker_thread != NULL) {
450 _worker_thread->at_sync_point(pending_recorders, InstanceKlass::number_of_instance_classes());
451 }
452 assert(SequenceGenerator::peek() == 1, "Should not have memory activities during sync-point");
453 } else {
454 _sync_point_skip_count ++;
455 }
456 }
457 }
458
459 // now, it is the time to shut whole things off
460 if (_state == NMT_final_shutdown) {
461 // walk all JavaThreads to delete all recorders
462 SyncThreadRecorderClosure stc;
463 Threads::threads_do(&stc);
464 // delete global recorder
465 {
466 ThreadCritical tc;
467 if (_global_recorder != NULL) {
468 delete _global_recorder;
469 _global_recorder = NULL;
470 }
471 }
472 MemRecorder* pending_recorders = get_pending_recorders();
473 if (pending_recorders != NULL) {
474 delete pending_recorders;
475 }
476 // try at a later sync point to ensure MemRecorder instance drops to zero to
477 // completely shutdown NMT
478 if (MemRecorder::_instance_count == 0) {
479 _state = NMT_shutdown;
480 _tracking_level = NMT_off;
481 }
482 }
483 }
484
485 /*
486 * Start worker thread.
487 */
488 bool MemTracker::start_worker(MemSnapshot* snapshot) {
489 assert(_worker_thread == NULL && _snapshot != NULL, "Just Check");
490 _worker_thread = new (std::nothrow) MemTrackWorker(snapshot);
491 if (_worker_thread == NULL) {
492 return false;
493 } else if (_worker_thread->has_error()) {
494 delete _worker_thread;
495 _worker_thread = NULL;
496 return false;
497 }
498 _worker_thread->start();
499 return true;
500 }
501
502 /*
503 * We need to collect a JavaThread's per-thread recorder
504 * before it exits.
505 */
506 void MemTracker::thread_exiting(JavaThread* thread) {
507 if (is_on()) {
508 MemRecorder* rec = thread->get_recorder();
509 if (rec != NULL) {
510 enqueue_pending_recorder(rec);
511 thread->set_recorder(NULL);
512 }
513 }
514 }
515
516 // baseline current memory snapshot
517 bool MemTracker::baseline() {
518 MutexLocker lock(_query_lock);
519 MemSnapshot* snapshot = get_snapshot();
520 if (snapshot != NULL) {
521 return _baseline.baseline(*snapshot, false);
522 }
523 return false;
524 }
525
526 // print memory usage from current snapshot
527 bool MemTracker::print_memory_usage(BaselineOutputer& out, size_t unit, bool summary_only) {
528 MemBaseline baseline;
529 MutexLocker lock(_query_lock);
530 MemSnapshot* snapshot = get_snapshot();
531 if (snapshot != NULL && baseline.baseline(*snapshot, summary_only)) {
532 BaselineReporter reporter(out, unit);
533 reporter.report_baseline(baseline, summary_only);
534 return true;
535 }
536 return false;
537 }
538
539 // Whitebox API for blocking until the current generation of NMT data has been merged
540 bool MemTracker::wbtest_wait_for_data_merge() {
541 // NMT can't be shutdown while we're holding _query_lock
542 MutexLocker lock(_query_lock);
543 assert(_worker_thread != NULL, "Invalid query");
544 // the generation at query time, so NMT will spin till this generation is processed
545 unsigned long generation_at_query_time = SequenceGenerator::current_generation();
546 unsigned long current_processing_generation = _processing_generation;
547 // if generation counter overflown
548 bool generation_overflown = (generation_at_query_time < current_processing_generation);
549 long generations_to_wrap = MAX_UNSIGNED_LONG - current_processing_generation;
550 // spin
551 while (!shutdown_in_progress()) {
552 if (!generation_overflown) {
553 if (current_processing_generation > generation_at_query_time) {
554 return true;
555 }
556 } else {
557 assert(generations_to_wrap >= 0, "Sanity check");
558 long current_generations_to_wrap = MAX_UNSIGNED_LONG - current_processing_generation;
559 assert(current_generations_to_wrap >= 0, "Sanity check");
560 // to overflow an unsigned long should take long time, so to_wrap check should be sufficient
561 if (current_generations_to_wrap > generations_to_wrap &&
562 current_processing_generation > generation_at_query_time) {
563 return true;
564 }
565 }
566
567 // if worker thread is idle, but generation is not advancing, that means
568 // there is not safepoint to let NMT advance generation, force one.
569 if (_worker_thread_idle) {
570 VM_ForceSafepoint vfs;
571 VMThread::execute(&vfs);
572 }
573 MemSnapshot* snapshot = get_snapshot();
574 if (snapshot == NULL) {
575 return false;
576 }
577 snapshot->wait(1000);
578 current_processing_generation = _processing_generation;
579 }
580 // We end up here if NMT is shutting down before our data has been merged
581 return false;
582 }
583
584 // compare memory usage between current snapshot and baseline
585 bool MemTracker::compare_memory_usage(BaselineOutputer& out, size_t unit, bool summary_only) {
586 MutexLocker lock(_query_lock);
587 if (_baseline.baselined()) {
588 MemBaseline baseline;
589 MemSnapshot* snapshot = get_snapshot();
590 if (snapshot != NULL && baseline.baseline(*snapshot, summary_only)) {
591 BaselineReporter reporter(out, unit);
592 reporter.diff_baselines(baseline, _baseline, summary_only);
593 return true;
594 }
595 }
596 return false;
597 }
598
599 #ifndef PRODUCT
600 void MemTracker::walk_stack(int toSkip, char* buf, int len) {
601 int cur_len = 0;
602 char tmp[1024];
603 address pc;
604
605 while (cur_len < len) {
606 pc = os::get_caller_pc(toSkip + 1);
607 if (pc != NULL && os::dll_address_to_function_name(pc, tmp, sizeof(tmp), NULL)) {
608 jio_snprintf(&buf[cur_len], (len - cur_len), "%s\n", tmp);
609 cur_len = (int)strlen(buf);
610 } else {
611 buf[cur_len] = '\0';
612 break;
613 }
614 toSkip ++;
615 }
616 }
617
618 void MemTracker::print_tracker_stats(outputStream* st) {
619 st->print_cr("\nMemory Tracker Stats:");
620 st->print_cr("\tMax sequence number = %d", SequenceGenerator::max_seq_num());
621 st->print_cr("\tthead count = %d", _thread_count);
622 st->print_cr("\tArena instance = %d", Arena::_instance_count);
623 st->print_cr("\tpooled recorder count = %d", _pooled_recorder_count);
624 st->print_cr("\tqueued recorder count = %d", _pending_recorder_count);
625 st->print_cr("\tmemory recorder instance count = %d", MemRecorder::_instance_count);
626 if (_worker_thread != NULL) {
627 st->print_cr("\tWorker thread:");
628 st->print_cr("\t\tSync point count = %d", _worker_thread->_sync_point_count);
629 st->print_cr("\t\tpending recorder count = %d", _worker_thread->count_pending_recorders());
630 st->print_cr("\t\tmerge count = %d", _worker_thread->_merge_count);
631 } else {
632 st->print_cr("\tWorker thread is not started");
633 }
634 st->print_cr(" ");
635
636 if (_snapshot != NULL) {
637 _snapshot->print_snapshot_stats(st);
638 } else {
639 st->print_cr("No snapshot");
640 }
641 }
642 #endif
643
644
645 // Tracker Implementation
646
647 /*
648 * Create a tracker.
649 * This is a fairly complicated constructor, as it has to make two important decisions:
650 * 1) Does it need to take ThreadCritical lock to write tracking record
651 * 2) Does it need to pre-reserve a sequence number for the tracking record
652 *
653 * The rules to determine if ThreadCritical is needed:
654 * 1. When nmt is in single-threaded bootstrapping mode, no lock is needed as VM
655 * still in single thread mode.
656 * 2. For all threads other than JavaThread, ThreadCritical is needed
657 * to write to recorders to global recorder.
658 * 3. For JavaThreads that are no longer visible by safepoint, also
659 * need to take ThreadCritical and records are written to global
660 * recorders, since these threads are NOT walked by Threads.do_thread().
661 * 4. JavaThreads that are running in safepoint-safe states do not stop
662 * for safepoints, ThreadCritical lock should be taken to write
663 * memory records.
664 * 5. JavaThreads that are running in VM state do not need any lock and
665 * records are written to per-thread recorders.
666 * 6. For a thread has yet to attach VM 'Thread', they need to take
667 * ThreadCritical to write to global recorder.
668 *
669 * The memory operations that need pre-reserve sequence numbers:
670 * The memory operations that "release" memory blocks and the
671 * operations can fail, need to pre-reserve sequence number. They
672 * are realloc, uncommit and release.
673 *
674 * The reason for pre-reserve sequence number, is to prevent race condition:
675 * Thread 1 Thread 2
676 * <release>
677 * <allocate>
678 * <write allocate record>
679 * <write release record>
680 * if Thread 2 happens to obtain the memory address Thread 1 just released,
681 * then NMT can mistakenly report the memory is free.
682 *
683 * Noticeably, free() does not need pre-reserve sequence number, because the call
684 * does not fail, so we can alway write "release" record before the memory is actaully
685 * freed.
686 *
687 * For realloc, uncommit and release, following coding pattern should be used:
688 *
689 * MemTracker::Tracker tkr = MemTracker::get_realloc_tracker();
690 * ptr = ::realloc(...);
691 * if (ptr == NULL) {
692 * tkr.record(...)
693 * } else {
694 * tkr.discard();
695 * }
696 *
697 * MemTracker::Tracker tkr = MemTracker::get_virtual_memory_uncommit_tracker();
698 * if (uncommit(...)) {
699 * tkr.record(...);
700 * } else {
701 * tkr.discard();
702 * }
703 *
704 * MemTracker::Tracker tkr = MemTracker::get_virtual_memory_release_tracker();
705 * if (release(...)) {
706 * tkr.record(...);
707 * } else {
708 * tkr.discard();
709 * }
710 *
711 * Since pre-reserved sequence number is only good for the generation that it is acquired,
712 * when there is pending Tracker that reserved sequence number, NMT sync-point has
713 * to be skipped to prevent from advancing generation. This is done by inc and dec
714 * MemTracker::_pending_op_count, when MemTracker::_pending_op_count > 0, NMT sync-point is skipped.
715 * Not all pre-reservation of sequence number will increment pending op count. For JavaThreads
716 * that honor safepoints, safepoint can not occur during the memory operations, so the
717 * pre-reserved sequence number won't cross the generation boundry.
718 */
719 MemTracker::Tracker::Tracker(MemoryOperation op, Thread* thr) {
720 _op = NoOp;
721 _seq = 0;
722 if (MemTracker::is_on()) {
723 _java_thread = NULL;
724 _op = op;
725
726 // figure out if ThreadCritical lock is needed to write this operation
727 // to MemTracker
728 if (MemTracker::is_single_threaded_bootstrap()) {
729 thr = NULL;
730 } else if (thr == NULL) {
731 // don't use Thread::current(), since it is possible that
732 // the calling thread has yet to attach to VM 'Thread',
733 // which will result assertion failure
734 thr = ThreadLocalStorage::thread();
735 }
736
737 if (thr != NULL) {
738 // Check NMT load
739 MemTracker::check_NMT_load(thr);
740
741 if (thr->is_Java_thread() && ((JavaThread*)thr)->is_safepoint_visible()) {
742 _java_thread = (JavaThread*)thr;
743 JavaThreadState state = _java_thread->thread_state();
744 // JavaThreads that are safepoint safe, can run through safepoint,
745 // so ThreadCritical is needed to ensure no threads at safepoint create
746 // new records while the records are being gathered and the sequence number is changing
747 _need_thread_critical_lock =
748 SafepointSynchronize::safepoint_safe(_java_thread, state);
749 } else {
750 _need_thread_critical_lock = true;
751 }
752 } else {
753 _need_thread_critical_lock
754 = !MemTracker::is_single_threaded_bootstrap();
755 }
756
757 // see if we need to pre-reserve sequence number for this operation
758 if (_op == Realloc || _op == Uncommit || _op == Release) {
759 if (_need_thread_critical_lock) {
760 ThreadCritical tc;
761 MemTracker::inc_pending_op_count();
762 _seq = SequenceGenerator::next();
763 } else {
764 // for the threads that honor safepoints, no safepoint can occur
765 // during the lifespan of tracker, so we don't need to increase
766 // pending op count.
767 _seq = SequenceGenerator::next();
768 }
769 }
770 }
771 }
772
773 void MemTracker::Tracker::discard() {
774 if (MemTracker::is_on() && _seq != 0) {
775 if (_need_thread_critical_lock) {
776 ThreadCritical tc;
777 MemTracker::dec_pending_op_count();
778 }
779 _seq = 0;
780 }
781 }
782
783
784 void MemTracker::Tracker::record(address old_addr, address new_addr, size_t size,
785 MEMFLAGS flags, address pc) {
786 assert(old_addr != NULL && new_addr != NULL, "Sanity check");
787 assert(_op == Realloc || _op == NoOp, "Wrong call");
788 if (MemTracker::is_on() && NMT_CAN_TRACK(flags) && _op != NoOp && !MemTracker::shutdown_in_progress()) {
789 assert(_seq > 0, "Need pre-reserve sequence number");
790 if (_need_thread_critical_lock) {
791 ThreadCritical tc;
792 // free old address, use pre-reserved sequence number
793 MemTracker::write_tracking_record(old_addr, MemPointerRecord::free_tag(),
794 0, _seq, pc, _java_thread);
795 MemTracker::write_tracking_record(new_addr, flags | MemPointerRecord::malloc_tag(),
796 size, SequenceGenerator::next(), pc, _java_thread);
797 // decrement MemTracker pending_op_count
798 MemTracker::dec_pending_op_count();
799 } else {
800 // free old address, use pre-reserved sequence number
801 MemTracker::write_tracking_record(old_addr, MemPointerRecord::free_tag(),
802 0, _seq, pc, _java_thread);
803 MemTracker::write_tracking_record(new_addr, flags | MemPointerRecord::malloc_tag(),
804 size, SequenceGenerator::next(), pc, _java_thread);
805 }
806 _seq = 0;
807 }
808 }
809
810 void MemTracker::Tracker::record(address addr, size_t size, MEMFLAGS flags, address pc) {
811 // OOM already?
812 if (addr == NULL) return;
813
814 if (MemTracker::is_on() && NMT_CAN_TRACK(flags) && _op != NoOp && !MemTracker::shutdown_in_progress()) {
815 bool pre_reserved_seq = (_seq != 0);
816 address pc = CALLER_CALLER_PC;
817 MEMFLAGS orig_flags = flags;
818
819 // or the tagging flags
820 switch(_op) {
821 case Malloc:
822 flags |= MemPointerRecord::malloc_tag();
823 break;
824 case Free:
825 flags = MemPointerRecord::free_tag();
826 break;
827 case Realloc:
828 fatal("Use the other Tracker::record()");
829 break;
830 case Reserve:
831 case ReserveAndCommit:
832 flags |= MemPointerRecord::virtual_memory_reserve_tag();
833 break;
834 case Commit:
835 flags = MemPointerRecord::virtual_memory_commit_tag();
836 break;
837 case Type:
838 flags |= MemPointerRecord::virtual_memory_type_tag();
839 break;
840 case Uncommit:
841 assert(pre_reserved_seq, "Need pre-reserve sequence number");
842 flags = MemPointerRecord::virtual_memory_uncommit_tag();
843 break;
844 case Release:
845 assert(pre_reserved_seq, "Need pre-reserve sequence number");
846 flags = MemPointerRecord::virtual_memory_release_tag();
847 break;
848 case ArenaSize:
849 // a bit of hack here, add a small postive offset to arena
850 // address for its size record, so the size record is sorted
851 // right after arena record.
852 flags = MemPointerRecord::arena_size_tag();
853 addr += sizeof(void*);
854 break;
855 case StackRelease:
856 flags = MemPointerRecord::virtual_memory_release_tag();
857 break;
858 default:
859 ShouldNotReachHere();
860 }
861
862 // write memory tracking record
863 if (_need_thread_critical_lock) {
864 ThreadCritical tc;
865 if (_seq == 0) _seq = SequenceGenerator::next();
866 MemTracker::write_tracking_record(addr, flags, size, _seq, pc, _java_thread);
867 if (_op == ReserveAndCommit) {
868 MemTracker::write_tracking_record(addr, orig_flags | MemPointerRecord::virtual_memory_commit_tag(),
869 size, SequenceGenerator::next(), pc, _java_thread);
870 }
871 if (pre_reserved_seq) MemTracker::dec_pending_op_count();
872 } else {
873 if (_seq == 0) _seq = SequenceGenerator::next();
874 MemTracker::write_tracking_record(addr, flags, size, _seq, pc, _java_thread);
875 if (_op == ReserveAndCommit) {
876 MemTracker::write_tracking_record(addr, orig_flags | MemPointerRecord::virtual_memory_commit_tag(),
877 size, SequenceGenerator::next(), pc, _java_thread);
878 }
879 }
880 _seq = 0;
881 }
882 }
883