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_NMT_DETAIL_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.");
89 _tracking_level = NMT_summary;
90 }
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
389 void MemTracker::sync() {
390 assert(_tracking_level > NMT_off, "NMT is not enabled");
391 assert(SafepointSynchronize::is_at_safepoint(), "Safepoint required");
392
393 // Some GC tests hit large number of safepoints in short period of time
394 // without meaningful activities. We should prevent going to
395 // sync point in these cases, which can potentially exhaust generation buffer.
396 // Here is the factots to determine if we should go into sync point:
397 // 1. not to overflow sequence number
398 // 2. if we are in danger to overflow generation buffer
399 // 3. how many safepoints we already skipped sync point
400 if (_state == NMT_started) {
401 // worker thread is not ready, no one can manage generation
402 // buffer, so skip this safepoint
403 if (_worker_thread == NULL) return;
404
405 if (_sync_point_skip_count < MAX_SAFEPOINTS_TO_SKIP) {
406 int per_seq_in_use = SequenceGenerator::peek() * 100 / max_jint;
407 int per_gen_in_use = _worker_thread->generations_in_use() * 100 / MAX_GENERATIONS;
408 if (per_seq_in_use < SAFE_SEQUENCE_THRESHOLD && per_gen_in_use >= HIGH_GENERATION_THRESHOLD) {
409 _sync_point_skip_count ++;
410 return;
411 }
412 }
413 {
414 // This method is running at safepoint, with ThreadCritical lock,
415 // it should guarantee that NMT is fully sync-ed.
416 ThreadCritical tc;
417
418 // We can NOT execute NMT sync-point if there are pending tracking ops.
419 if (_pending_op_count == 0) {
420 SequenceGenerator::reset();
421 _sync_point_skip_count = 0;
422
423 // walk all JavaThreads to collect recorders
424 SyncThreadRecorderClosure stc;
425 Threads::threads_do(&stc);
426
427 _thread_count = stc.get_thread_count();
428 MemRecorder* pending_recorders = get_pending_recorders();
429
430 if (_global_recorder != NULL) {
431 _global_recorder->set_next(pending_recorders);
432 pending_recorders = _global_recorder;
433 _global_recorder = NULL;
434 }
435
436 // see if NMT has too many outstanding recorder instances, it usually
437 // means that worker thread is lagging behind in processing them.
438 if (!AutoShutdownNMT) {
439 _slowdown_calling_thread = (MemRecorder::_instance_count > MAX_RECORDER_THREAD_RATIO * _thread_count);
440 }
441
442 // check _worker_thread with lock to avoid racing condition
443 if (_worker_thread != NULL) {
444 _worker_thread->at_sync_point(pending_recorders, InstanceKlass::number_of_instance_classes());
445 }
446 assert(SequenceGenerator::peek() == 1, "Should not have memory activities during sync-point");
447 } else {
448 _sync_point_skip_count ++;
449 }
450 }
451 }
452
453 // now, it is the time to shut whole things off
454 if (_state == NMT_final_shutdown) {
455 // walk all JavaThreads to delete all recorders
456 SyncThreadRecorderClosure stc;
457 Threads::threads_do(&stc);
458 // delete global recorder
459 {
460 ThreadCritical tc;
461 if (_global_recorder != NULL) {
462 delete _global_recorder;
463 _global_recorder = NULL;
464 }
465 }
466 MemRecorder* pending_recorders = get_pending_recorders();
467 if (pending_recorders != NULL) {
468 delete pending_recorders;
469 }
470 // try at a later sync point to ensure MemRecorder instance drops to zero to
471 // completely shutdown NMT
472 if (MemRecorder::_instance_count == 0) {
473 _state = NMT_shutdown;
474 _tracking_level = NMT_off;
475 }
476 }
477 }
478
479 /*
480 * Start worker thread.
481 */
482 bool MemTracker::start_worker(MemSnapshot* snapshot) {
483 assert(_worker_thread == NULL && _snapshot != NULL, "Just Check");
484 _worker_thread = new (std::nothrow) MemTrackWorker(snapshot);
485 if (_worker_thread == NULL) {
486 return false;
487 } else if (_worker_thread->has_error()) {
488 delete _worker_thread;
489 _worker_thread = NULL;
490 return false;
491 }
492 _worker_thread->start();
493 return true;
494 }
495
496 /*
497 * We need to collect a JavaThread's per-thread recorder
498 * before it exits.
499 */
500 void MemTracker::thread_exiting(JavaThread* thread) {
501 if (is_on()) {
502 MemRecorder* rec = thread->get_recorder();
503 if (rec != NULL) {
504 enqueue_pending_recorder(rec);
505 thread->set_recorder(NULL);
506 }
507 }
508 }
509
510 // baseline current memory snapshot
511 bool MemTracker::baseline() {
512 MutexLocker lock(_query_lock);
513 MemSnapshot* snapshot = get_snapshot();
514 if (snapshot != NULL) {
515 return _baseline.baseline(*snapshot, false);
516 }
517 return false;
518 }
519
520 // print memory usage from current snapshot
521 bool MemTracker::print_memory_usage(BaselineOutputer& out, size_t unit, bool summary_only) {
522 MemBaseline baseline;
523 MutexLocker lock(_query_lock);
524 MemSnapshot* snapshot = get_snapshot();
525 if (snapshot != NULL && baseline.baseline(*snapshot, summary_only)) {
526 BaselineReporter reporter(out, unit);
527 reporter.report_baseline(baseline, summary_only);
528 return true;
529 }
530 return false;
531 }
532
533 // Whitebox API for blocking until the current generation of NMT data has been merged
534 bool MemTracker::wbtest_wait_for_data_merge() {
535 // NMT can't be shutdown while we're holding _query_lock
536 MutexLocker lock(_query_lock);
537 assert(_worker_thread != NULL, "Invalid query");
538 // the generation at query time, so NMT will spin till this generation is processed
539 unsigned long generation_at_query_time = SequenceGenerator::current_generation();
540 unsigned long current_processing_generation = _processing_generation;
541 // if generation counter overflown
542 bool generation_overflown = (generation_at_query_time < current_processing_generation);
543 long generations_to_wrap = MAX_UNSIGNED_LONG - current_processing_generation;
544 // spin
545 while (!shutdown_in_progress()) {
546 if (!generation_overflown) {
547 if (current_processing_generation > generation_at_query_time) {
548 return true;
549 }
550 } else {
551 assert(generations_to_wrap >= 0, "Sanity check");
552 long current_generations_to_wrap = MAX_UNSIGNED_LONG - current_processing_generation;
553 assert(current_generations_to_wrap >= 0, "Sanity check");
554 // to overflow an unsigned long should take long time, so to_wrap check should be sufficient
555 if (current_generations_to_wrap > generations_to_wrap &&
556 current_processing_generation > generation_at_query_time) {
557 return true;
558 }
559 }
560
561 // if worker thread is idle, but generation is not advancing, that means
562 // there is not safepoint to let NMT advance generation, force one.
563 if (_worker_thread_idle) {
564 VM_ForceSafepoint vfs;
565 VMThread::execute(&vfs);
566 }
567 MemSnapshot* snapshot = get_snapshot();
568 if (snapshot == NULL) {
569 return false;
570 }
571 snapshot->wait(1000);
572 current_processing_generation = _processing_generation;
573 }
574 // We end up here if NMT is shutting down before our data has been merged
575 return false;
576 }
577
578 // compare memory usage between current snapshot and baseline
579 bool MemTracker::compare_memory_usage(BaselineOutputer& out, size_t unit, bool summary_only) {
580 MutexLocker lock(_query_lock);
581 if (_baseline.baselined()) {
582 MemBaseline baseline;
583 MemSnapshot* snapshot = get_snapshot();
584 if (snapshot != NULL && baseline.baseline(*snapshot, summary_only)) {
585 BaselineReporter reporter(out, unit);
586 reporter.diff_baselines(baseline, _baseline, summary_only);
587 return true;
588 }
589 }
590 return false;
591 }
592
593 #ifndef PRODUCT
594 void MemTracker::walk_stack(int toSkip, char* buf, int len) {
595 int cur_len = 0;
596 char tmp[1024];
597 address pc;
598
599 while (cur_len < len) {
600 pc = os::get_caller_pc(toSkip + 1);
601 if (pc != NULL && os::dll_address_to_function_name(pc, tmp, sizeof(tmp), NULL)) {
602 jio_snprintf(&buf[cur_len], (len - cur_len), "%s\n", tmp);
603 cur_len = (int)strlen(buf);
604 } else {
605 buf[cur_len] = '\0';
606 break;
607 }
608 toSkip ++;
609 }
610 }
611
612 void MemTracker::print_tracker_stats(outputStream* st) {
613 st->print_cr("\nMemory Tracker Stats:");
614 st->print_cr("\tMax sequence number = %d", SequenceGenerator::max_seq_num());
615 st->print_cr("\tthead count = %d", _thread_count);
616 st->print_cr("\tArena instance = %d", Arena::_instance_count);
617 st->print_cr("\tpooled recorder count = %d", _pooled_recorder_count);
618 st->print_cr("\tqueued recorder count = %d", _pending_recorder_count);
619 st->print_cr("\tmemory recorder instance count = %d", MemRecorder::_instance_count);
620 if (_worker_thread != NULL) {
621 st->print_cr("\tWorker thread:");
622 st->print_cr("\t\tSync point count = %d", _worker_thread->_sync_point_count);
623 st->print_cr("\t\tpending recorder count = %d", _worker_thread->count_pending_recorders());
624 st->print_cr("\t\tmerge count = %d", _worker_thread->_merge_count);
625 } else {
626 st->print_cr("\tWorker thread is not started");
627 }
628 st->print_cr(" ");
629
630 if (_snapshot != NULL) {
631 _snapshot->print_snapshot_stats(st);
632 } else {
633 st->print_cr("No snapshot");
634 }
635 }
636 #endif
637
638
639 // Tracker Implementation
640
641 /*
642 * Create a tracker.
643 * This is a fairly complicated constructor, as it has to make two important decisions:
644 * 1) Does it need to take ThreadCritical lock to write tracking record
645 * 2) Does it need to pre-reserve a sequence number for the tracking record
646 *
647 * The rules to determine if ThreadCritical is needed:
648 * 1. When nmt is in single-threaded bootstrapping mode, no lock is needed as VM
649 * still in single thread mode.
650 * 2. For all threads other than JavaThread, ThreadCritical is needed
651 * to write to recorders to global recorder.
652 * 3. For JavaThreads that are no longer visible by safepoint, also
653 * need to take ThreadCritical and records are written to global
654 * recorders, since these threads are NOT walked by Threads.do_thread().
655 * 4. JavaThreads that are running in safepoint-safe states do not stop
656 * for safepoints, ThreadCritical lock should be taken to write
657 * memory records.
658 * 5. JavaThreads that are running in VM state do not need any lock and
659 * records are written to per-thread recorders.
660 * 6. For a thread has yet to attach VM 'Thread', they need to take
661 * ThreadCritical to write to global recorder.
662 *
663 * The memory operations that need pre-reserve sequence numbers:
664 * The memory operations that "release" memory blocks and the
665 * operations can fail, need to pre-reserve sequence number. They
666 * are realloc, uncommit and release.
667 *
668 * The reason for pre-reserve sequence number, is to prevent race condition:
669 * Thread 1 Thread 2
670 * <release>
671 * <allocate>
672 * <write allocate record>
673 * <write release record>
674 * if Thread 2 happens to obtain the memory address Thread 1 just released,
675 * then NMT can mistakenly report the memory is free.
676 *
677 * Noticeably, free() does not need pre-reserve sequence number, because the call
678 * does not fail, so we can alway write "release" record before the memory is actaully
679 * freed.
680 *
681 * For realloc, uncommit and release, following coding pattern should be used:
682 *
683 * MemTracker::Tracker tkr = MemTracker::get_realloc_tracker();
684 * ptr = ::realloc(...);
685 * if (ptr == NULL) {
686 * tkr.record(...)
687 * } else {
688 * tkr.discard();
689 * }
690 *
691 * MemTracker::Tracker tkr = MemTracker::get_virtual_memory_uncommit_tracker();
692 * if (uncommit(...)) {
693 * tkr.record(...);
694 * } else {
695 * tkr.discard();
696 * }
697 *
698 * MemTracker::Tracker tkr = MemTracker::get_virtual_memory_release_tracker();
699 * if (release(...)) {
700 * tkr.record(...);
701 * } else {
702 * tkr.discard();
703 * }
704 *
705 * Since pre-reserved sequence number is only good for the generation that it is acquired,
706 * when there is pending Tracker that reserved sequence number, NMT sync-point has
707 * to be skipped to prevent from advancing generation. This is done by inc and dec
708 * MemTracker::_pending_op_count, when MemTracker::_pending_op_count > 0, NMT sync-point is skipped.
709 * Not all pre-reservation of sequence number will increment pending op count. For JavaThreads
710 * that honor safepoints, safepoint can not occur during the memory operations, so the
711 * pre-reserved sequence number won't cross the generation boundry.
712 */
713 MemTracker::Tracker::Tracker(MemoryOperation op, Thread* thr) {
714 _op = NoOp;
715 _seq = 0;
716 if (MemTracker::is_on()) {
717 _java_thread = NULL;
718 _op = op;
719
720 // figure out if ThreadCritical lock is needed to write this operation
721 // to MemTracker
722 if (MemTracker::is_single_threaded_bootstrap()) {
723 thr = NULL;
724 } else if (thr == NULL) {
725 // don't use Thread::current(), since it is possible that
726 // the calling thread has yet to attach to VM 'Thread',
727 // which will result assertion failure
728 thr = ThreadLocalStorage::thread();
729 }
730
731 if (thr != NULL) {
732 // Check NMT load
733 MemTracker::check_NMT_load(thr);
734
735 if (thr->is_Java_thread() && ((JavaThread*)thr)->is_safepoint_visible()) {
736 _java_thread = (JavaThread*)thr;
737 JavaThreadState state = _java_thread->thread_state();
738 // JavaThreads that are safepoint safe, can run through safepoint,
739 // so ThreadCritical is needed to ensure no threads at safepoint create
740 // new records while the records are being gathered and the sequence number is changing
741 _need_thread_critical_lock =
742 SafepointSynchronize::safepoint_safe(_java_thread, state);
743 } else {
744 _need_thread_critical_lock = true;
745 }
746 } else {
747 _need_thread_critical_lock
748 = !MemTracker::is_single_threaded_bootstrap();
749 }
750
751 // see if we need to pre-reserve sequence number for this operation
752 if (_op == Realloc || _op == Uncommit || _op == Release) {
753 if (_need_thread_critical_lock) {
754 ThreadCritical tc;
755 MemTracker::inc_pending_op_count();
756 _seq = SequenceGenerator::next();
757 } else {
758 // for the threads that honor safepoints, no safepoint can occur
759 // during the lifespan of tracker, so we don't need to increase
760 // pending op count.
761 _seq = SequenceGenerator::next();
762 }
763 }
764 }
765 }
766
767 void MemTracker::Tracker::discard() {
768 if (MemTracker::is_on() && _seq != 0) {
769 if (_need_thread_critical_lock) {
770 ThreadCritical tc;
771 MemTracker::dec_pending_op_count();
772 }
773 _seq = 0;
774 }
775 }
776
777
778 void MemTracker::Tracker::record(address old_addr, address new_addr, size_t size,
779 MEMFLAGS flags, address pc) {
780 assert(old_addr != NULL && new_addr != NULL, "Sanity check");
781 assert(_op == Realloc || _op == NoOp, "Wrong call");
782 if (MemTracker::is_on() && NMT_CAN_TRACK(flags) && _op != NoOp) {
783 assert(_seq > 0, "Need pre-reserve sequence number");
784 if (_need_thread_critical_lock) {
785 ThreadCritical tc;
786 // free old address, use pre-reserved sequence number
787 MemTracker::write_tracking_record(old_addr, MemPointerRecord::free_tag(),
788 0, _seq, pc, _java_thread);
789 MemTracker::write_tracking_record(new_addr, flags | MemPointerRecord::malloc_tag(),
790 size, SequenceGenerator::next(), pc, _java_thread);
791 // decrement MemTracker pending_op_count
792 MemTracker::dec_pending_op_count();
793 } else {
794 // free old address, use pre-reserved sequence number
795 MemTracker::write_tracking_record(old_addr, MemPointerRecord::free_tag(),
796 0, _seq, pc, _java_thread);
797 MemTracker::write_tracking_record(new_addr, flags | MemPointerRecord::malloc_tag(),
798 size, SequenceGenerator::next(), pc, _java_thread);
799 }
800 _seq = 0;
801 }
802 }
803
804 void MemTracker::Tracker::record(address addr, size_t size, MEMFLAGS flags, address pc) {
805 // OOM already?
806 if (addr == NULL) return;
807
808 if (MemTracker::is_on() && NMT_CAN_TRACK(flags) && _op != NoOp) {
809 bool pre_reserved_seq = (_seq != 0);
810 address pc = CALLER_CALLER_PC;
811 MEMFLAGS orig_flags = flags;
812
813 // or the tagging flags
814 switch(_op) {
815 case Malloc:
816 flags |= MemPointerRecord::malloc_tag();
817 break;
818 case Free:
819 flags = MemPointerRecord::free_tag();
820 break;
821 case Realloc:
822 fatal("Use the other Tracker::record()");
823 break;
824 case Reserve:
825 case ReserveAndCommit:
826 flags |= MemPointerRecord::virtual_memory_reserve_tag();
827 break;
828 case Commit:
829 flags = MemPointerRecord::virtual_memory_commit_tag();
830 break;
831 case Type:
832 flags |= MemPointerRecord::virtual_memory_type_tag();
833 break;
834 case Uncommit:
835 assert(pre_reserved_seq, "Need pre-reserve sequence number");
836 flags = MemPointerRecord::virtual_memory_uncommit_tag();
837 break;
838 case Release:
839 assert(pre_reserved_seq, "Need pre-reserve sequence number");
840 flags = MemPointerRecord::virtual_memory_release_tag();
841 break;
842 case ArenaSize:
843 // a bit of hack here, add a small postive offset to arena
844 // address for its size record, so the size record is sorted
845 // right after arena record.
846 flags = MemPointerRecord::arena_size_tag();
847 addr += sizeof(void*);
848 break;
849 case StackRelease:
850 flags = MemPointerRecord::virtual_memory_release_tag();
851 break;
852 default:
853 ShouldNotReachHere();
854 }
855
856 // write memory tracking record
857 if (_need_thread_critical_lock) {
858 ThreadCritical tc;
859 if (_seq == 0) _seq = SequenceGenerator::next();
860 MemTracker::write_tracking_record(addr, flags, size, _seq, pc, _java_thread);
861 if (_op == ReserveAndCommit) {
862 MemTracker::write_tracking_record(addr, orig_flags | MemPointerRecord::virtual_memory_commit_tag(),
863 size, SequenceGenerator::next(), pc, _java_thread);
864 }
865 if (pre_reserved_seq) MemTracker::dec_pending_op_count();
866 } else {
867 if (_seq == 0) _seq = SequenceGenerator::next();
868 MemTracker::write_tracking_record(addr, flags, size, _seq, pc, _java_thread);
869 if (_op == ReserveAndCommit) {
870 MemTracker::write_tracking_record(addr, orig_flags | MemPointerRecord::virtual_memory_commit_tag(),
871 size, SequenceGenerator::next(), pc, _java_thread);
872 }
873 }
874 _seq = 0;
875 }
876 }
877