1 /*
2 * Copyright (c) 2017, Google and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26
27 #include "gc/shared/collectedHeap.hpp"
28 #include "memory/universe.hpp"
29 #include "runtime/heapMonitoring.hpp"
30 #include "runtime/vframe.hpp"
31
32 const int MaxStackDepth = 1024;
33
34 // Internal data structure representing traces.
35 struct StackTraceData : CHeapObj<mtInternal> {
36 jvmtiStackTrace *trace;
37 oop obj;
38 int references;
39
40 StackTraceData(jvmtiStackTrace *t, oop o) : trace(t), obj(o), references(0) {}
41
42 StackTraceData() : trace(NULL), obj(NULL), references(0) {}
43
44 // StackTraceDatas are shared around the board between various lists. So
45 // handle this by hand instead of having this in the destructor. There are
46 // cases where the struct is on the stack but holding heap data not to be
47 // freed.
48 static void free_data(StackTraceData *data) {
49 if (data->trace != NULL) {
50 FREE_C_HEAP_ARRAY(jvmtiFrameInfo, data->trace->frames);
51 FREE_C_HEAP_OBJ(data->trace);
52 }
53 delete data;
54 }
55 };
56
57 // Fixed size buffer for holding garbage traces.
58 class GarbageTracesBuffer : public CHeapObj<mtInternal> {
59 public:
60 GarbageTracesBuffer(uint32_t size) : _size(size) {
61 _garbage_traces = NEW_C_HEAP_ARRAY(StackTraceData*,
62 size,
63 mtInternal);
64 memset(_garbage_traces, 0, sizeof(StackTraceData*) * size);
65 }
66
67 virtual ~GarbageTracesBuffer() {
68 FREE_C_HEAP_ARRAY(StackTraceData*, _garbage_traces);
69 }
70
71 StackTraceData** get_traces() const {
72 return _garbage_traces;
73 }
74
75 bool store_trace(StackTraceData *trace) {
76 uint32_t index;
77 if (!select_replacement(&index)) {
78 return false;
79 }
80
81 StackTraceData *old_data = _garbage_traces[index];
82
83 if (old_data != NULL) {
84 old_data->references--;
85
86 if (old_data->references == 0) {
87 StackTraceData::free_data(old_data);
88 }
89 }
90
91 trace->references++;
92 _garbage_traces[index] = trace;
93 return true;
94 }
95
96 uint32_t size() const {
97 return _size;
98 }
99
100 protected:
101 // Subclasses select the trace to replace. Returns false if no replacement
102 // is to happen, otherwise stores the index of the trace to replace in
103 // *index.
104 virtual bool select_replacement(uint32_t *index) = 0;
105
106 const uint32_t _size;
107
108 private:
109 // The current garbage traces. A fixed-size ring buffer.
110 StackTraceData **_garbage_traces;
111 };
112
113 // Keep statistical sample of traces over the lifetime of the server.
114 // When the buffer is full, replace a random entry with probability
115 // 1/samples_seen. This strategy tends towards preserving the most frequently
116 // occuring traces over time.
117 class FrequentGarbageTraces : public GarbageTracesBuffer {
118 public:
119 FrequentGarbageTraces(int size)
120 : GarbageTracesBuffer(size),
121 _garbage_traces_pos(0),
122 _samples_seen(0) {
123 }
124
125 virtual ~FrequentGarbageTraces() {
126 }
127
128 virtual bool select_replacement(uint32_t* index) {
129 ++_samples_seen;
130
131 if (_garbage_traces_pos < _size) {
132 *index = _garbage_traces_pos++;
133 return true;
134 }
135
136 uint64_t random_uint64 =
137 (static_cast<uint64_t>(::random()) << 32) | ::random();
138
139 uint32_t random_index = random_uint64 % _samples_seen;
140 if (random_index < _size) {
141 *index = random_index;
142 return true;
143 }
144
145 return false;
146 }
147
148 private:
149 // The current position in the buffer as we initially fill it.
150 uint32_t _garbage_traces_pos;
151
152 uint64_t _samples_seen;
153 };
154
155 // Store most recent garbage traces.
156 class MostRecentGarbageTraces : public GarbageTracesBuffer {
157 public:
158 MostRecentGarbageTraces(int size)
159 : GarbageTracesBuffer(size),
160 _garbage_traces_pos(0) {
161 }
162
163 virtual ~MostRecentGarbageTraces() {
164 }
165
166 virtual bool select_replacement(uint32_t* index) {
167 *index = _garbage_traces_pos;
168
169 _garbage_traces_pos =
170 (_garbage_traces_pos + 1) % _size;
171
172 return true;
173 }
174
175 private:
176 // The current position in the buffer.
177 uint32_t _garbage_traces_pos;
178 };
179
180 // Each object that we profile is stored as trace with the thread_id.
181 class StackTraceStorage : public CHeapObj<mtInternal> {
182 public:
183 // The function that gets called to add a trace to the list of
184 // traces we are maintaining.
185 void add_trace(jvmtiStackTrace *trace, oop o);
186
187 // The function that gets called by the client to retrieve the list
188 // of stack traces. Passes a jvmtiStackTraces which will get mutated.
189 void get_all_stack_traces(jvmtiStackTraces *traces);
190
191 // The function that gets called by the client to retrieve the list
192 // of stack traces. Passes a jvmtiStackTraces which will get mutated.
193 void get_garbage_stack_traces(jvmtiStackTraces *traces);
194
195 // The function that gets called by the client to retrieve the list
196 // of stack traces. Passes a jvmtiStackTraces which will get mutated.
197 void get_frequent_garbage_stack_traces(jvmtiStackTraces *traces);
198
199 // Executes whenever weak references are traversed. is_alive tells
200 // you if the given oop is still reachable and live.
201 size_t weak_oops_do(BoolObjectClosure* is_alive, OopClosure *f);
202
203 ~StackTraceStorage();
204 StackTraceStorage();
205
206 static StackTraceStorage* storage() {
207 if (internal_storage == NULL) {
208 internal_storage = new StackTraceStorage();
209 }
210 return internal_storage;
211 }
212
213 static void reset_stack_trace_storage() {
214 delete internal_storage;
215 internal_storage = NULL;
216 }
217
218 bool is_initialized() {
219 return _initialized;
220 }
221
222 const jvmtiHeapSamplingStats& get_heap_sampling_stats() const {
223 return _stats;
224 }
225
226 // Static method to set the storage in place at initialization.
227 static void initialize_stack_trace_storage(int max_storage) {
228 reset_stack_trace_storage();
229 StackTraceStorage *storage = StackTraceStorage::storage();
230 storage->initialize_storage(max_storage);
231 }
232
233 void accumulate_sample_rate(size_t rate) {
234 _stats.sample_rate_accumulation += rate;
235 _stats.sample_rate_count++;
236 }
237
238 bool initialized() { return _initialized; }
239 volatile bool *initialized_address() { return &_initialized; }
240
241 private:
242 // The traces currently sampled.
243 GrowableArray<StackTraceData> *_allocated_traces;
244
245 // Recent garbage traces.
246 MostRecentGarbageTraces *_recent_garbage_traces;
247
248 // Frequent garbage traces.
249 FrequentGarbageTraces *_frequent_garbage_traces;
250
251 // Heap Sampling statistics.
252 jvmtiHeapSamplingStats _stats;
253
254 // Maximum amount of storage provided by the JVMTI call initialize_profiling.
255 int _max_gc_storage;
256
257 static StackTraceStorage* internal_storage;
258 volatile bool _initialized;
259
260 // Support functions and classes for copying data to the external
261 // world.
262 class StackTraceDataCopier {
263 public:
264 virtual int size() const = 0;
265 virtual const StackTraceData *get(uint32_t i) const = 0;
266 };
267
268 class LiveStackTraceDataCopier : public StackTraceDataCopier {
269 public:
270 LiveStackTraceDataCopier(GrowableArray<StackTraceData> *data) :
271 _data(data) {}
272 int size() const { return _data ? _data->length() : 0; }
273 const StackTraceData *get(uint32_t i) const { return _data->adr_at(i); }
274
275 private:
276 GrowableArray<StackTraceData> *_data;
277 };
278
279 class GarbageStackTraceDataCopier : public StackTraceDataCopier {
280 public:
281 GarbageStackTraceDataCopier(StackTraceData **data, int size) :
282 _data(data), _size(size) {}
283 int size() const { return _size; }
284 const StackTraceData *get(uint32_t i) const { return _data[i]; }
285
286 private:
287 StackTraceData **_data;
288 int _size;
289 };
290
291 // Instance initialization.
292 void initialize_storage(int max_storage);
293
294 // Copies from StackTraceData to jvmtiStackTrace.
295 bool deep_copy(jvmtiStackTrace *to, const StackTraceData *from);
296
297 // Creates a deep copy of the list of StackTraceData.
298 void copy_stack_traces(const StackTraceDataCopier &copier,
299 jvmtiStackTraces *traces);
300
301 void store_garbage_trace(const StackTraceData &trace);
302
303 void free_garbage();
304 };
305
306 StackTraceStorage* StackTraceStorage::internal_storage;
307
308 // Statics for Sampler
309 double HeapMonitoring::_log_table[1 << FastLogNumBits];
310 bool HeapMonitoring::_enabled;
311 AlwaysTrueClosure HeapMonitoring::_always_true;
312 jint HeapMonitoring::_monitoring_rate;
313
314 // Cheap random number generator
315 uint64_t HeapMonitoring::_rnd;
316
317 StackTraceStorage::StackTraceStorage() :
318 _allocated_traces(NULL),
319 _recent_garbage_traces(NULL),
320 _frequent_garbage_traces(NULL),
321 _max_gc_storage(0),
322 _initialized(false) {
323 memset(&_stats, 0, sizeof(_stats));
324 }
325
326 void StackTraceStorage::free_garbage() {
327 StackTraceData **recent_garbage = NULL;
328 uint32_t recent_size = 0;
329
330 StackTraceData **frequent_garbage = NULL;
331 uint32_t frequent_size = 0;
332
333 if (_recent_garbage_traces != NULL) {
334 recent_garbage = _recent_garbage_traces->get_traces();
335 recent_size = _recent_garbage_traces->size();
336 }
337
338 if (_frequent_garbage_traces != NULL) {
339 frequent_garbage = _frequent_garbage_traces->get_traces();
340 frequent_size = _frequent_garbage_traces->size();
341 }
342
343 // Simple solution since this happens at exit.
344 // Go through the recent and remove any that only are referenced there.
345 for (uint32_t i = 0; i < recent_size; i++) {
346 StackTraceData *trace = recent_garbage[i];
347 if (trace != NULL) {
348 trace->references--;
349
350 if (trace->references == 0) {
351 StackTraceData::free_data(trace);
352 }
353 }
354 }
355
356 // Then go through the frequent and remove those that are now only there.
357 for (uint32_t i = 0; i < frequent_size; i++) {
358 StackTraceData *trace = frequent_garbage[i];
359 if (trace != NULL) {
360 trace->references--;
361
362 if (trace->references == 0) {
363 StackTraceData::free_data(trace);
364 }
365 }
366 }
367 }
368
369 StackTraceStorage::~StackTraceStorage() {
370 delete _allocated_traces;
371
372 free_garbage();
373 delete _recent_garbage_traces;
374 delete _frequent_garbage_traces;
375 _initialized = false;
376 }
377
378 void StackTraceStorage::initialize_storage(int max_gc_storage) {
379 // In case multiple threads got locked and then 1 by 1 got through.
380 if (_initialized) {
381 return;
382 }
383
384 _allocated_traces = new (ResourceObj::C_HEAP, mtInternal)
385 GrowableArray<StackTraceData>(128, true);
386
387 _recent_garbage_traces = new MostRecentGarbageTraces(max_gc_storage);
388 _frequent_garbage_traces = new FrequentGarbageTraces(max_gc_storage);
389
390 _max_gc_storage = max_gc_storage;
391 _initialized = true;
392 }
393
394 void StackTraceStorage::add_trace(jvmtiStackTrace *trace, oop o) {
395 StackTraceData new_data(trace, o);
396 _stats.sample_count++;
397 _stats.stack_depth_accumulation += trace->frame_count;
398 _allocated_traces->append(new_data);
399 }
400
401 size_t StackTraceStorage::weak_oops_do(BoolObjectClosure *is_alive,
402 OopClosure *f) {
403 size_t count = 0;
404 if (is_initialized()) {
405 int len = _allocated_traces->length();
406
407 // Compact the oop traces. Moves the live oops to the beginning of the
408 // growable array, potentially overwriting the dead ones.
409 int curr_pos = 0;
410 for (int i = 0; i < len; i++) {
411 StackTraceData &trace = _allocated_traces->at(i);
412 oop value = trace.obj;
413 if (Universe::heap()->is_in_reserved(value)
414 && is_alive->do_object_b(value)) {
415 // Update the oop to point to the new object if it is still alive.
416 f->do_oop(&(trace.obj));
417
418 // Copy the old trace, if it is still live.
419 _allocated_traces->at_put(curr_pos++, trace);
420
421 count++;
422 } else {
423 // If the old trace is no longer live, add it to the list of
424 // recently collected garbage.
425 store_garbage_trace(trace);
426 }
427 }
428
429 // Zero out remaining array elements. Even though the call to trunc_to
430 // below truncates these values, zeroing them out is good practice.
431 StackTraceData zero_trace;
432 for (int i = curr_pos; i < len; i++) {
433 _allocated_traces->at_put(i, zero_trace);
434 }
435
436 // Set the array's length to the number of live elements.
437 _allocated_traces->trunc_to(curr_pos);
438 }
439
440 return count;
441 }
442
443 bool StackTraceStorage::deep_copy(jvmtiStackTrace *to,
444 const StackTraceData *from) {
445 const jvmtiStackTrace *src = from->trace;
446 *to = *src;
447
448 to->frames =
449 NEW_C_HEAP_ARRAY(jvmtiFrameInfo, src->frame_count, mtInternal);
450
451 if (to->frames == NULL) {
452 return false;
453 }
454
455 memcpy(to->frames,
456 src->frames,
457 sizeof(jvmtiFrameInfo) * src->frame_count);
458 return true;
459 }
460
461 // Called by the outside world; returns a copy of the stack traces
462 // (because we could be replacing them as the user handles them).
463 // The array is secretly null-terminated (to make it easier to reclaim).
464 void StackTraceStorage::get_all_stack_traces(jvmtiStackTraces *traces) {
465 LiveStackTraceDataCopier copier(_allocated_traces);
466 copy_stack_traces(copier, traces);
467 }
468
469 // See comment on get_all_stack_traces
470 void StackTraceStorage::get_garbage_stack_traces(jvmtiStackTraces *traces) {
471 GarbageStackTraceDataCopier copier(_recent_garbage_traces->get_traces(),
472 _recent_garbage_traces->size());
473 copy_stack_traces(copier, traces);
474 }
475
476 // See comment on get_all_stack_traces
477 void StackTraceStorage::get_frequent_garbage_stack_traces(
478 jvmtiStackTraces *traces) {
479 GarbageStackTraceDataCopier copier(_frequent_garbage_traces->get_traces(),
480 _frequent_garbage_traces->size());
481 copy_stack_traces(copier, traces);
482 }
483
484
485 void StackTraceStorage::copy_stack_traces(const StackTraceDataCopier &copier,
486 jvmtiStackTraces *traces) {
487 int len = copier.size();
488
489 // Create a new array to store the StackTraceData objects.
490 // + 1 for a NULL at the end.
491 jvmtiStackTrace *t =
492 NEW_C_HEAP_ARRAY(jvmtiStackTrace, len + 1, mtInternal);
493 if (t == NULL) {
494 traces->stack_traces = NULL;
495 traces->trace_count = 0;
496 return;
497 }
498 // +1 to have a NULL at the end of the array.
499 memset(t, 0, (len + 1) * sizeof(*t));
500
501 // Copy the StackTraceData objects into the new array.
502 int trace_count = 0;
503 for (int i = 0; i < len; i++) {
504 const StackTraceData *stack_trace = copier.get(i);
505 if (stack_trace != NULL) {
506 jvmtiStackTrace *to = &t[trace_count];
507 if (!deep_copy(to, stack_trace)) {
508 continue;
509 }
510 trace_count++;
511 }
512 }
513
514 traces->stack_traces = t;
515 traces->trace_count = trace_count;
516 }
517
518 void StackTraceStorage::store_garbage_trace(const StackTraceData &trace) {
519 StackTraceData *new_trace = new StackTraceData();
520 *new_trace = trace;
521
522 bool accepted = _recent_garbage_traces->store_trace(new_trace);
523
524 // Accepted is on the right of the boolean to force the store_trace to happen.
525 accepted = _frequent_garbage_traces->store_trace(new_trace) || accepted;
526
527 if (!accepted) {
528 // No one wanted to use it.
529 delete new_trace;
530 }
531
532 _stats.garbage_collected_samples++;
533 }
534
535 // Delegate the initialization question to the underlying storage system.
536 bool HeapMonitoring::initialized() {
537 return StackTraceStorage::storage()->initialized();
538 }
539
540 // Delegate the initialization question to the underlying storage system.
541 bool *HeapMonitoring::initialized_address() {
542 return
543 const_cast<bool*>(StackTraceStorage::storage()->initialized_address());
544 }
545
546 void HeapMonitoring::get_live_traces(jvmtiStackTraces *traces) {
547 StackTraceStorage::storage()->get_all_stack_traces(traces);
548 }
549
550 void HeapMonitoring::get_sampling_statistics(jvmtiHeapSamplingStats *stats) {
551 const jvmtiHeapSamplingStats& internal_stats =
552 StackTraceStorage::storage()->get_heap_sampling_stats();
553 *stats = internal_stats;
554 }
555
556 void HeapMonitoring::get_frequent_garbage_traces(jvmtiStackTraces *traces) {
557 StackTraceStorage::storage()->get_frequent_garbage_stack_traces(traces);
558 }
559
560 void HeapMonitoring::get_garbage_traces(jvmtiStackTraces *traces) {
561 StackTraceStorage::storage()->get_garbage_stack_traces(traces);
562 }
563
564 void HeapMonitoring::release_traces(jvmtiStackTraces *traces) {
565 jint trace_count = traces->trace_count;
566 jvmtiStackTrace *stack_traces = traces->stack_traces;
567
568 for (jint i = 0; i < trace_count; i++) {
569 jvmtiStackTrace *current_trace = stack_traces + i;
570 FREE_C_HEAP_ARRAY(jvmtiFrameInfo, current_trace->frames);
571 }
572
573 FREE_C_HEAP_ARRAY(jvmtiStackTrace, traces->stack_traces);
574 traces->trace_count = 0;
575 traces->stack_traces = NULL;
576 }
577
578 // Invoked by the GC to clean up old stack traces and remove old arrays
579 // of instrumentation that are still lying around.
580 size_t HeapMonitoring::weak_oops_do(BoolObjectClosure* is_alive,
581 OopClosure *f) {
582 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
583 return StackTraceStorage::storage()->weak_oops_do(is_alive, f);
584 }
585
586 void HeapMonitoring::initialize_profiling(jint monitoring_rate,
587 jint max_gc_storage) {
588 // Ignore if already enabled.
589 if (_enabled) {
590 return;
591 }
592
593 _monitoring_rate = monitoring_rate;
594
595 // Initalize and reset.
596 StackTraceStorage::initialize_stack_trace_storage(max_gc_storage);
597
598 // Populate the lookup table for fast_log2.
599 // This approximates the log2 curve with a step function.
600 // Steps have height equal to log2 of the mid-point of the step.
601 for (int i = 0; i < (1 << FastLogNumBits); i++) {
602 double half_way = static_cast<double>(i + 0.5);
603 _log_table[i] = (log(1.0 + half_way / (1 << FastLogNumBits)) / log(2.0));
604 }
605
606 JavaThread *t = static_cast<JavaThread *>(Thread::current());
607 _rnd = static_cast<uint32_t>(reinterpret_cast<uintptr_t>(t));
608 if (_rnd == 0) {
609 _rnd = 1;
610 }
611 _enabled = true;
612 }
613
614 void HeapMonitoring::stop_profiling() {
615 _enabled = false;
616 }
617
618 // Generates a geometric variable with the specified mean (512K by default).
619 // This is done by generating a random number between 0 and 1 and applying
620 // the inverse cumulative distribution function for an exponential.
621 // Specifically: Let m be the inverse of the sample rate, then
622 // the probability distribution function is m*exp(-mx) so the CDF is
623 // p = 1 - exp(-mx), so
624 // q = 1 - p = exp(-mx)
625 // log_e(q) = -mx
626 // -log_e(q)/m = x
627 // log_2(q) * (-log_e(2) * 1/m) = x
628 // In the code, q is actually in the range 1 to 2**26, hence the -26 below
629 void HeapMonitoring::pick_next_sample(size_t *ptr) {
630 _rnd = next_random(_rnd);
631 // Take the top 26 bits as the random number
632 // (This plus a 1<<58 sampling bound gives a max possible step of
633 // 5194297183973780480 bytes. In this case,
634 // for sample_parameter = 1<<19, max possible step is
635 // 9448372 bytes (24 bits).
636 const uint64_t prng_mod_power = 48; // Number of bits in prng
637 // The uint32_t cast is to prevent a (hard-to-reproduce) NAN
638 // under piii debug for some binaries.
639 double q = static_cast<uint32_t>(_rnd >> (prng_mod_power - 26)) + 1.0;
640 // Put the computed p-value through the CDF of a geometric.
641 // For faster performance (save ~1/20th exec time), replace
642 // min(0.0, FastLog2(q) - 26) by (Fastlog2(q) - 26.000705)
643 // The value 26.000705 is used rather than 26 to compensate
644 // for inaccuracies in FastLog2 which otherwise result in a
645 // negative answer.
646 double log_val = (fast_log2(q) - 26);
647 size_t rate = static_cast<size_t>(
648 (0.0 < log_val ? 0.0 : log_val) * (-log(2.0) * (_monitoring_rate)) + 1);
649 *ptr = rate;
650
651 StackTraceStorage::storage()->accumulate_sample_rate(rate);
652 }
653
654 void HeapMonitoring::object_alloc_do_sample(Thread *t, oopDesc *o, intx byte_size) {
655 #if defined(X86) || defined(PPC)
656 JavaThread *thread = static_cast<JavaThread *>(t);
657 if (StackTraceStorage::storage()->is_initialized()) {
658 assert(t->is_Java_thread(), "non-Java thread passed to do_sample");
659 JavaThread *thread = static_cast<JavaThread *>(t);
660
661 jvmtiStackTrace *trace = NEW_C_HEAP_OBJ(jvmtiStackTrace, mtInternal);
662 if (trace == NULL) {
663 return;
664 }
665
666 jvmtiFrameInfo *frames =
667 NEW_C_HEAP_ARRAY(jvmtiFrameInfo, MaxStackDepth, mtInternal);
668
669 if (frames == NULL) {
670 FREE_C_HEAP_OBJ(trace);
671 return;
672 }
673
674 trace->frames = frames;
675 trace->thread_id = SharedRuntime::get_java_tid(thread);
676 trace->size = byte_size;
677 trace->frame_count = 0;
678
679 if (thread->has_last_Java_frame()) { // just to be safe
680 vframeStream vfst(thread, true);
681 int count = 0;
682 while (!vfst.at_end() && count < MaxStackDepth) {
683 Method* m = vfst.method();
684 frames[count].location = vfst.bci();
685 frames[count].method = m->jmethod_id();
686 count++;
687
688 vfst.next();
689 }
690 trace->frame_count = count;
691 }
692
693 if (trace->frame_count> 0) {
694 // Success!
695 StackTraceStorage::storage()->add_trace(trace, o);
696 return;
697 }
698
699 // Failure!
700 FREE_C_HEAP_ARRAY(jvmtiFrameInfo, trace->frames);
701 FREE_C_HEAP_OBJ(trace);
702 return;
703 } else {
704 // There is something like 64K worth of allocation before the VM
705 // initializes. This is just in the interests of not slowing down
706 // startup.
707 assert(t->is_Java_thread(), "non-Java thread passed to do_sample");
708 }
709 #else
710 Unimplemented();
711 #endif
712 }