1 /*
   2  * Copyright (c) 2012, 2018, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "jfr/jfrEvents.hpp"
  27 #include "jfr/recorder/jfrRecorder.hpp"
  28 #include "jfr/periodic/sampling/jfrCallTrace.hpp"
  29 #include "jfr/periodic/sampling/jfrThreadSampler.hpp"
  30 #include "jfr/recorder/service/jfrOptionSet.hpp"
  31 #include "jfr/recorder/stacktrace/jfrStackTraceRepository.hpp"
  32 #include "jfr/support/jfrThreadId.hpp"
  33 #include "jfr/utilities/jfrTime.hpp"
  34 #include "logging/log.hpp"
  35 #include "runtime/frame.inline.hpp"
  36 #include "runtime/os.hpp"
  37 #include "runtime/semaphore.hpp"
  38 #include "runtime/thread.inline.hpp"
  39 #include "runtime/threadSMR.hpp"
  40 
  41 enum JfrSampleType {
  42   NO_SAMPLE = 0,
  43   JAVA_SAMPLE = 1,
  44   NATIVE_SAMPLE = 2
  45 };
  46 
  47 static bool thread_state_in_java(JavaThread* thread) {
  48   assert(thread != NULL, "invariant");
  49   switch(thread->thread_state()) {
  50     case _thread_new:
  51     case _thread_uninitialized:
  52     case _thread_new_trans:
  53     case _thread_in_vm_trans:
  54     case _thread_blocked_trans:
  55     case _thread_in_native_trans:
  56     case _thread_blocked:
  57     case _thread_in_vm:
  58     case _thread_in_native:
  59     case _thread_in_Java_trans:
  60       break;
  61     case _thread_in_Java:
  62       return true;
  63     default:
  64       ShouldNotReachHere();
  65       break;
  66   }
  67   return false;
  68 }
  69 
  70 static bool thread_state_in_native(JavaThread* thread) {
  71   assert(thread != NULL, "invariant");
  72   switch(thread->thread_state()) {
  73     case _thread_new:
  74     case _thread_uninitialized:
  75     case _thread_new_trans:
  76     case _thread_blocked_trans:
  77     case _thread_blocked:
  78     case _thread_in_vm:
  79     case _thread_in_vm_trans:
  80     case _thread_in_Java_trans:
  81     case _thread_in_Java:
  82     case _thread_in_native_trans:
  83       break;
  84     case _thread_in_native:
  85       return true;
  86     default:
  87       ShouldNotReachHere();
  88       break;
  89   }
  90   return false;
  91 }
  92 
  93 class JfrThreadSampleClosure {
  94  public:
  95   JfrThreadSampleClosure(EventExecutionSample* events, EventNativeMethodSample* events_native);
  96   ~JfrThreadSampleClosure() {}
  97   EventExecutionSample* next_event() { return &_events[_added_java++]; }
  98   EventNativeMethodSample* next_event_native() { return &_events_native[_added_native++]; }
  99   void commit_events(JfrSampleType type);
 100   bool do_sample_thread(JavaThread* thread, JfrStackFrame* frames, u4 max_frames, JfrSampleType type);
 101   uint java_entries() { return _added_java; }
 102   uint native_entries() { return _added_native; }
 103 
 104  private:
 105   bool sample_thread_in_java(JavaThread* thread, JfrStackFrame* frames, u4 max_frames);
 106   bool sample_thread_in_native(JavaThread* thread, JfrStackFrame* frames, u4 max_frames);
 107   EventExecutionSample* _events;
 108   EventNativeMethodSample* _events_native;
 109   Thread* _self;
 110   uint _added_java;
 111   uint _added_native;
 112 };
 113 
 114 class OSThreadSampler : public os::SuspendedThreadTask {
 115  public:
 116   OSThreadSampler(JavaThread* thread,
 117                   JfrThreadSampleClosure& closure,
 118                   JfrStackFrame *frames,
 119                   u4 max_frames) : os::SuspendedThreadTask((Thread*)thread),
 120     _success(false),
 121     _stacktrace(frames, max_frames),
 122     _closure(closure),
 123     _suspend_time() {}
 124 
 125   void take_sample();
 126   void do_task(const os::SuspendedThreadTaskContext& context);
 127   void protected_task(const os::SuspendedThreadTaskContext& context);
 128   bool success() const { return _success; }
 129   const JfrStackTrace& stacktrace() const { return _stacktrace; }
 130 
 131  private:
 132   bool _success;
 133   JfrStackTrace _stacktrace;
 134   JfrThreadSampleClosure& _closure;
 135   JfrTicks _suspend_time;
 136 };
 137 
 138 class OSThreadSamplerCallback : public os::CrashProtectionCallback {
 139  public:
 140   OSThreadSamplerCallback(OSThreadSampler& sampler, const os::SuspendedThreadTaskContext &context) :
 141     _sampler(sampler), _context(context) {
 142   }
 143   virtual void call() {
 144     _sampler.protected_task(_context);
 145   }
 146  private:
 147   OSThreadSampler& _sampler;
 148   const os::SuspendedThreadTaskContext& _context;
 149 };
 150 
 151 void OSThreadSampler::do_task(const os::SuspendedThreadTaskContext& context) {
 152 #ifndef ASSERT
 153   guarantee(JfrOptionSet::sample_protection(), "Sample Protection should be on in product builds");
 154 #endif
 155   assert(_suspend_time.value() == 0, "already timestamped!");
 156   _suspend_time = JfrTicks::now();
 157 
 158   if (JfrOptionSet::sample_protection()) {
 159     OSThreadSamplerCallback cb(*this, context);
 160     os::ThreadCrashProtection crash_protection;
 161     if (!crash_protection.call(cb)) {
 162       log_error(jfr)("Thread method sampler crashed");
 163     }
 164   } else {
 165     protected_task(context);
 166   }
 167 }
 168 
 169 /*
 170 * From this method and down the call tree we attempt to protect against crashes
 171 * using a signal handler / __try block. Don't take locks, rely on destructors or
 172 * leave memory (in case of signal / exception) in an inconsistent state. */
 173 void OSThreadSampler::protected_task(const os::SuspendedThreadTaskContext& context) {
 174   JavaThread* jth = (JavaThread*)context.thread();
 175   // Skip sample if we signaled a thread that moved to other state
 176   if (!thread_state_in_java(jth)) {
 177     return;
 178   }
 179   JfrGetCallTrace trace(true, jth);
 180   frame topframe;
 181   if (trace.get_topframe(context.ucontext(), topframe)) {
 182     if (_stacktrace.record_thread(*jth, topframe)) {
 183       /* If we managed to get a topframe and a stacktrace, create an event
 184       * and put it into our array. We can't call Jfr::_stacktraces.add()
 185       * here since it would allocate memory using malloc. Doing so while
 186       * the stopped thread is inside malloc would deadlock. */
 187       _success = true;
 188       EventExecutionSample *ev = _closure.next_event();
 189       ev->set_starttime(_suspend_time);
 190       ev->set_endtime(_suspend_time); // fake to not take an end time
 191       ev->set_sampledThread(JFR_THREAD_ID(jth));
 192       ev->set_state(java_lang_Thread::get_thread_status(jth->threadObj()));
 193     }
 194   }
 195 }
 196 
 197 void OSThreadSampler::take_sample() {
 198   run();
 199 }
 200 
 201 class JfrNativeSamplerCallback : public os::CrashProtectionCallback {
 202  public:
 203   JfrNativeSamplerCallback(JfrThreadSampleClosure& closure, JavaThread* jt, JfrStackFrame* frames, u4 max_frames) :
 204     _closure(closure), _jt(jt), _stacktrace(frames, max_frames), _success(false) {
 205   }
 206   virtual void call();
 207   bool success() { return _success; }
 208   JfrStackTrace& stacktrace() { return _stacktrace; }
 209 
 210  private:
 211   JfrThreadSampleClosure& _closure;
 212   JavaThread* _jt;
 213   JfrStackTrace _stacktrace;
 214   bool _success;
 215 };
 216 
 217 static void write_native_event(JfrThreadSampleClosure& closure, JavaThread* jt) {
 218   EventNativeMethodSample *ev = closure.next_event_native();
 219   ev->set_starttime(JfrTicks::now());
 220   ev->set_sampledThread(JFR_THREAD_ID(jt));
 221   ev->set_state(java_lang_Thread::get_thread_status(jt->threadObj()));
 222 }
 223 
 224 void JfrNativeSamplerCallback::call() {
 225   // When a thread is only attach it will be native without a last java frame
 226   if (!_jt->has_last_Java_frame()) {
 227     return;
 228   }
 229 
 230   frame topframe = _jt->last_frame();
 231   frame first_java_frame;
 232   Method* method = NULL;
 233   JfrGetCallTrace gct(false, _jt);
 234   if (!gct.find_top_frame(topframe, &method, first_java_frame)) {
 235     return;
 236   }
 237   if (method == NULL) {
 238     return;
 239   }
 240   topframe = first_java_frame;
 241   _success = _stacktrace.record_thread(*_jt, topframe);
 242   if (_success) {
 243     write_native_event(_closure, _jt);
 244   }
 245 }
 246 
 247 bool JfrThreadSampleClosure::sample_thread_in_java(JavaThread* thread, JfrStackFrame* frames, u4 max_frames) {
 248   OSThreadSampler sampler(thread, *this, frames, max_frames);
 249   sampler.take_sample();
 250   /* We don't want to allocate any memory using malloc/etc while the thread
 251   * is stopped, so everything is stored in stack allocated memory until this
 252   * point where the thread has been resumed again, if the sampling was a success
 253   * we need to store the stacktrace in the stacktrace repository and update
 254   * the event with the id that was returned. */
 255   if (!sampler.success()) {
 256     return false;
 257   }
 258   EventExecutionSample *event = &_events[_added_java - 1];
 259   traceid id = JfrStackTraceRepository::add(sampler.stacktrace());
 260   assert(id != 0, "Stacktrace id should not be 0");
 261   event->set_stackTrace(id);
 262   return true;
 263 }
 264 
 265 bool JfrThreadSampleClosure::sample_thread_in_native(JavaThread* thread, JfrStackFrame* frames, u4 max_frames) {
 266   JfrNativeSamplerCallback cb(*this, thread, frames, max_frames);
 267   if (JfrOptionSet::sample_protection()) {
 268     os::ThreadCrashProtection crash_protection;
 269     if (!crash_protection.call(cb)) {
 270       log_error(jfr)("Thread method sampler crashed for native");
 271     }
 272   } else {
 273     cb.call();
 274   }
 275   if (!cb.success()) {
 276     return false;
 277   }
 278   EventNativeMethodSample *event = &_events_native[_added_native - 1];
 279   traceid id = JfrStackTraceRepository::add(cb.stacktrace());
 280   assert(id != 0, "Stacktrace id should not be 0");
 281   event->set_stackTrace(id);
 282   return true;
 283 }
 284 
 285 static const uint MAX_NR_OF_JAVA_SAMPLES = 5;
 286 static const uint MAX_NR_OF_NATIVE_SAMPLES = 1;
 287 
 288 void JfrThreadSampleClosure::commit_events(JfrSampleType type) {
 289   if (JAVA_SAMPLE == type) {
 290     assert(_added_java > 0 && _added_java <= MAX_NR_OF_JAVA_SAMPLES, "invariant");
 291     for (uint i = 0; i < _added_java; ++i) {
 292       _events[i].commit();
 293     }
 294   } else {
 295     assert(NATIVE_SAMPLE == type, "invariant");
 296     assert(_added_native > 0 && _added_native <= MAX_NR_OF_NATIVE_SAMPLES, "invariant");
 297     for (uint i = 0; i < _added_native; ++i) {
 298       _events_native[i].commit();
 299     }
 300   }
 301 }
 302 
 303 JfrThreadSampleClosure::JfrThreadSampleClosure(EventExecutionSample* events, EventNativeMethodSample* events_native) :
 304   _events(events),
 305   _events_native(events_native),
 306   _self(Thread::current()),
 307   _added_java(0),
 308   _added_native(0) {
 309 }
 310 
 311 class JfrThreadSampler : public NonJavaThread {
 312   friend class JfrThreadSampling;
 313  private:
 314   Semaphore _sample;
 315   Thread* _sampler_thread;
 316   JfrStackFrame* const _frames;
 317   JavaThread* _last_thread_java;
 318   JavaThread* _last_thread_native;
 319   size_t _interval_java;
 320   size_t _interval_native;
 321   int _cur_index;
 322   const u4 _max_frames;
 323   volatile bool _disenrolled;
 324 
 325   JavaThread* next_thread(ThreadsList* t_list, JavaThread* first_sampled, JavaThread* current);
 326   void task_stacktrace(JfrSampleType type, JavaThread** last_thread);
 327   JfrThreadSampler(size_t interval_java, size_t interval_native, u4 max_frames);
 328   ~JfrThreadSampler();
 329 
 330   void start_thread();
 331 
 332   void enroll();
 333   void disenroll();
 334   void set_java_interval(size_t interval) { _interval_java = interval; };
 335   void set_native_interval(size_t interval) { _interval_native = interval; };
 336   size_t get_java_interval() { return _interval_java; };
 337   size_t get_native_interval() { return _interval_native; };
 338 
 339  public:
 340   void run();
 341   static Monitor* transition_block() { return JfrThreadSampler_lock; }
 342   static void on_javathread_suspend(JavaThread* thread);
 343 };
 344 
 345 static void clear_transition_block(JavaThread* jt) {
 346   jt->clear_trace_flag();
 347   JfrThreadLocal* const tl = jt->jfr_thread_local();
 348   if (tl->is_trace_block()) {
 349     MutexLockerEx ml(JfrThreadSampler::transition_block(), Mutex::_no_safepoint_check_flag);
 350     JfrThreadSampler::transition_block()->notify_all();
 351   }
 352 }
 353 
 354 bool JfrThreadSampleClosure::do_sample_thread(JavaThread* thread, JfrStackFrame* frames, u4 max_frames, JfrSampleType type) {
 355   assert(Threads_lock->owned_by_self(), "Holding the thread table lock.");
 356   if (thread->is_hidden_from_external_view() || thread->in_deopt_handler()) {
 357     return false;
 358   }
 359 
 360   bool ret = false;
 361   thread->set_trace_flag();
 362   if (JAVA_SAMPLE == type) {
 363     if (thread_state_in_java(thread)) {
 364       ret = sample_thread_in_java(thread, frames, max_frames);
 365     }
 366   } else {
 367     assert(NATIVE_SAMPLE == type, "invariant");
 368     if (thread_state_in_native(thread)) {
 369       ret = sample_thread_in_native(thread, frames, max_frames);
 370     }
 371   }
 372   clear_transition_block(thread);
 373   return ret;
 374 }
 375 
 376 JfrThreadSampler::JfrThreadSampler(size_t interval_java, size_t interval_native, u4 max_frames) :
 377   _sample(),
 378   _sampler_thread(NULL),
 379   _frames(JfrCHeapObj::new_array<JfrStackFrame>(max_frames)),
 380   _last_thread_java(NULL),
 381   _last_thread_native(NULL),
 382   _interval_java(interval_java),
 383   _interval_native(interval_native),
 384   _cur_index(-1),
 385   _max_frames(max_frames),
 386   _disenrolled(true) {
 387 }
 388 
 389 JfrThreadSampler::~JfrThreadSampler() {
 390   JfrCHeapObj::free(_frames, sizeof(JfrStackFrame) * _max_frames);
 391 }
 392 
 393 void JfrThreadSampler::on_javathread_suspend(JavaThread* thread) {
 394   JfrThreadLocal* const tl = thread->jfr_thread_local();
 395   tl->set_trace_block();
 396   {
 397     MutexLockerEx ml(transition_block(), Mutex::_no_safepoint_check_flag);
 398     while (thread->is_trace_suspend()) {
 399       transition_block()->wait(true);
 400     }
 401     tl->clear_trace_block();
 402   }
 403 }
 404 
 405 JavaThread* JfrThreadSampler::next_thread(ThreadsList* t_list, JavaThread* first_sampled, JavaThread* current) {
 406   assert(t_list != NULL, "invariant");
 407   assert(Threads_lock->owned_by_self(), "Holding the thread table lock.");
 408   assert(_cur_index >= -1 && (uint)_cur_index + 1 <= t_list->length(), "invariant");
 409   assert((current == NULL && -1 == _cur_index) || (t_list->find_index_of_JavaThread(current) == _cur_index), "invariant");
 410   if ((uint)_cur_index + 1 == t_list->length()) {
 411     // wrap
 412     _cur_index = 0;
 413   } else {
 414     _cur_index++;
 415   }
 416   assert(_cur_index >= 0 && (uint)_cur_index < t_list->length(), "invariant");
 417   JavaThread* const next = t_list->thread_at(_cur_index);
 418   return next != first_sampled ? next : NULL;
 419 }
 420 
 421 void JfrThreadSampler::start_thread() {
 422   if (os::create_thread(this, os::os_thread)) {
 423     os::start_thread(this);
 424   } else {
 425     log_error(jfr)("Failed to create thread for thread sampling");
 426   }
 427 }
 428 
 429 void JfrThreadSampler::enroll() {
 430   if (_disenrolled) {
 431     log_info(jfr)("Enrolling thread sampler");
 432     _sample.signal();
 433     _disenrolled = false;
 434   }
 435 }
 436 
 437 void JfrThreadSampler::disenroll() {
 438   if (!_disenrolled) {
 439     _sample.wait();
 440     _disenrolled = true;
 441     log_info(jfr)("Disenrolling thread sampler");
 442   }
 443 }
 444 
 445 static jlong get_monotonic_ms() {
 446   return os::javaTimeNanos() / 1000000;
 447 }
 448 
 449 void JfrThreadSampler::run() {
 450   assert(_sampler_thread == NULL, "invariant");
 451 
 452   _sampler_thread = this;
 453 
 454   jlong last_java_ms = get_monotonic_ms();
 455   jlong last_native_ms = last_java_ms;
 456   while (true) {
 457     if (!_sample.trywait()) {
 458       // disenrolled
 459       _sample.wait();
 460       last_java_ms = get_monotonic_ms();
 461       last_native_ms = last_java_ms;
 462     }
 463     _sample.signal();
 464     jlong java_interval = _interval_java == 0 ? max_jlong : MAX2<jlong>(_interval_java, 10);
 465     jlong native_interval = _interval_native == 0 ? max_jlong : MAX2<jlong>(_interval_native, 10);
 466 
 467     jlong now_ms = get_monotonic_ms();
 468 
 469     jlong next_j = java_interval + last_java_ms - now_ms;
 470     jlong next_n = native_interval + last_native_ms - now_ms;
 471 
 472     jlong sleep_to_next = MIN2<jlong>(next_j, next_n);
 473 
 474     if (sleep_to_next > 0) {
 475       os::naked_short_sleep(sleep_to_next);
 476     }
 477 
 478     if ((next_j - sleep_to_next) <= 0) {
 479       task_stacktrace(JAVA_SAMPLE, &_last_thread_java);
 480       last_java_ms = get_monotonic_ms();
 481     }
 482     if ((next_n - sleep_to_next) <= 0) {
 483       task_stacktrace(NATIVE_SAMPLE, &_last_thread_native);
 484       last_native_ms = get_monotonic_ms();
 485     }
 486   }
 487   delete this;
 488 }
 489 
 490 
 491 void JfrThreadSampler::task_stacktrace(JfrSampleType type, JavaThread** last_thread) {
 492   ResourceMark rm;
 493   EventExecutionSample samples[MAX_NR_OF_JAVA_SAMPLES];
 494   EventNativeMethodSample samples_native[MAX_NR_OF_NATIVE_SAMPLES];
 495   JfrThreadSampleClosure sample_task(samples, samples_native);
 496 
 497   const uint sample_limit = JAVA_SAMPLE == type ? MAX_NR_OF_JAVA_SAMPLES : MAX_NR_OF_NATIVE_SAMPLES;
 498   uint num_samples = 0;
 499   JavaThread* start = NULL;
 500 
 501   {
 502     elapsedTimer sample_time;
 503     sample_time.start();
 504     {
 505       MonitorLockerEx tlock(Threads_lock, Mutex::_allow_vm_block_flag);
 506       ThreadsListHandle tlh;
 507       // Resolve a sample session relative start position index into the thread list array.
 508       // In cases where the last sampled thread is NULL or not-NULL but stale, find_index() returns -1.
 509       _cur_index = tlh.list()->find_index_of_JavaThread(*last_thread);
 510       JavaThread* current = _cur_index != -1 ? *last_thread : NULL;
 511 
 512       while (num_samples < sample_limit) {
 513         current = next_thread(tlh.list(), start, current);
 514         if (current == NULL) {
 515           break;
 516         }
 517         if (start == NULL) {
 518           start = current;  // remember the thread where we started to attempt sampling
 519         }
 520         if (current->is_Compiler_thread()) {
 521           continue;
 522         }
 523         if (sample_task.do_sample_thread(current, _frames, _max_frames, type)) {
 524           num_samples++;
 525         }
 526       }
 527       *last_thread = current;  // remember the thread we last attempted to sample
 528     }
 529     sample_time.stop();
 530     log_trace(jfr)("JFR thread sampling done in %3.7f secs with %d java %d native samples",
 531                    sample_time.seconds(), sample_task.java_entries(), sample_task.native_entries());
 532   }
 533   if (num_samples > 0) {
 534     sample_task.commit_events(type);
 535   }
 536 }
 537 
 538 static JfrThreadSampling* _instance = NULL;
 539 
 540 JfrThreadSampling& JfrThreadSampling::instance() {
 541   return *_instance;
 542 }
 543 
 544 JfrThreadSampling* JfrThreadSampling::create() {
 545   assert(_instance == NULL, "invariant");
 546   _instance = new JfrThreadSampling();
 547   return _instance;
 548 }
 549 
 550 void JfrThreadSampling::destroy() {
 551   if (_instance != NULL) {
 552     delete _instance;
 553     _instance = NULL;
 554   }
 555 }
 556 
 557 JfrThreadSampling::JfrThreadSampling() : _sampler(NULL) {}
 558 
 559 JfrThreadSampling::~JfrThreadSampling() {
 560   if (_sampler != NULL) {
 561     _sampler->disenroll();
 562   }
 563 }
 564 
 565 static void log(size_t interval_java, size_t interval_native) {
 566   log_info(jfr)("Updated thread sampler for java: " SIZE_FORMAT "  ms, native " SIZE_FORMAT " ms", interval_java, interval_native);
 567 }
 568 
 569 void JfrThreadSampling::start_sampler(size_t interval_java, size_t interval_native) {
 570   assert(_sampler == NULL, "invariant");
 571   log_info(jfr)("Enrolling thread sampler");
 572   _sampler = new JfrThreadSampler(interval_java, interval_native, JfrOptionSet::stackdepth());
 573   _sampler->start_thread();
 574   _sampler->enroll();
 575 }
 576 
 577 void JfrThreadSampling::set_sampling_interval(bool java_interval, size_t period) {
 578   size_t interval_java = 0;
 579   size_t interval_native = 0;
 580   if (_sampler != NULL) {
 581     interval_java = _sampler->get_java_interval();
 582     interval_native = _sampler->get_native_interval();
 583   }
 584   if (java_interval) {
 585     interval_java = period;
 586   } else {
 587     interval_native = period;
 588   }
 589   if (interval_java > 0 || interval_native > 0) {
 590     if (_sampler == NULL) {
 591       log_info(jfr)("Creating thread sampler for java:%zu ms, native %zu ms", interval_java, interval_native);
 592       start_sampler(interval_java, interval_native);
 593     } else {
 594       _sampler->set_java_interval(interval_java);
 595       _sampler->set_native_interval(interval_native);
 596       _sampler->enroll();
 597     }
 598     assert(_sampler != NULL, "invariant");
 599     log(interval_java, interval_native);
 600   } else if (_sampler != NULL) {
 601     _sampler->disenroll();
 602   }
 603 }
 604 
 605 void JfrThreadSampling::set_java_sample_interval(size_t period) {
 606   if (_instance == NULL && 0 == period) {
 607     return;
 608   }
 609   instance().set_sampling_interval(true, period);
 610 }
 611 
 612 void JfrThreadSampling::set_native_sample_interval(size_t period) {
 613   if (_instance == NULL && 0 == period) {
 614     return;
 615   }
 616   instance().set_sampling_interval(false, period);
 617 }
 618 
 619 void JfrThreadSampling::on_javathread_suspend(JavaThread* thread) {
 620   JfrThreadSampler::on_javathread_suspend(thread);
 621 }