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