JDK14/Java14源码在线阅读

/*
 * Copyright (c) 2017, 2019, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 *
 */

#include "precompiled.hpp"
#include "jfr/jfrEvents.hpp"
#include "jfr/leakprofiler/sampling/objectSample.hpp"
#include "jfr/leakprofiler/sampling/objectSampler.hpp"
#include "jfr/leakprofiler/sampling/sampleList.hpp"
#include "jfr/leakprofiler/sampling/samplePriorityQueue.hpp"
#include "jfr/recorder/jfrEventSetting.inline.hpp"
#include "jfr/recorder/checkpoint/jfrCheckpointManager.hpp"
#include "jfr/recorder/stacktrace/jfrStackTraceRepository.hpp"
#include "jfr/support/jfrThreadLocal.hpp"
#include "jfr/utilities/jfrTryLock.hpp"
#include "logging/log.hpp"
#include "memory/universe.hpp"
#include "oops/oop.inline.hpp"
#include "runtime/atomic.hpp"
#include "runtime/orderAccess.hpp"
#include "runtime/safepoint.hpp"
#include "runtime/thread.hpp"

static ObjectSampler* _instance = NULL;

static ObjectSampler& instance() {
  assert(_instance != NULL, "invariant");
  return *_instance;
}

ObjectSampler::ObjectSampler(size_t size) :
  _priority_queue(new SamplePriorityQueue(size)),
  _list(new SampleList(size)),
  _last_sweep(JfrTicks::now()),
  _total_allocated(0),
  _threshold(0),
  _size(size),
  _dead_samples(false) {}

ObjectSampler::~ObjectSampler() {
  delete _priority_queue;
  _priority_queue = NULL;
  delete _list;
  _list = NULL;
}

bool ObjectSampler::create(size_t size) {
  assert(SafepointSynchronize::is_at_safepoint(), "invariant");
  assert(_instance == NULL, "invariant");
  _instance = new ObjectSampler(size);
  return _instance != NULL;
}

bool ObjectSampler::is_created() {
  return _instance != NULL;
}

ObjectSampler* ObjectSampler::sampler() {
  assert(is_created(), "invariant");
  return _instance;
}

void ObjectSampler::destroy() {
  assert(SafepointSynchronize::is_at_safepoint(), "invariant");
  if (_instance != NULL) {
    ObjectSampler* const sampler = _instance;
    _instance = NULL;
    delete sampler;
  }
}

static volatile int _lock = 0;

ObjectSampler* ObjectSampler::acquire() {
  assert(is_created(), "invariant");
  while (Atomic::cmpxchg(&_lock, 0, 1) == 1) {}
  return _instance;
}

void ObjectSampler::release() {
  assert(is_created(), "invariant");
  OrderAccess::fence();
  _lock = 0;
}

static traceid get_thread_id(JavaThread* thread) {
  assert(thread != NULL, "invariant");
  if (thread->threadObj() == NULL) {
    return 0;
  }
  const JfrThreadLocal* const tl = thread->jfr_thread_local();
  assert(tl != NULL, "invariant");
  if (tl->is_excluded()) {
    return 0;
  }
  if (!tl->has_thread_blob()) {
    JfrCheckpointManager::create_thread_blob(thread);
  }
  assert(tl->has_thread_blob(), "invariant");
  return tl->thread_id();
}

static void record_stacktrace(JavaThread* thread) {
  assert(thread != NULL, "invariant");
  if (JfrEventSetting::has_stacktrace(EventOldObjectSample::eventId)) {
    JfrStackTraceRepository::record_and_cache(thread);
  }
}

void ObjectSampler::sample(HeapWord* obj, size_t allocated, JavaThread* thread) {
  assert(thread != NULL, "invariant");
  assert(is_created(), "invariant");
  const traceid thread_id = get_thread_id(thread);
  if (thread_id == 0) {
    return;
  }
  record_stacktrace(thread);
  // try enter critical section
  JfrTryLock tryLock(&_lock);
  if (!tryLock.has_lock()) {
    log_trace(jfr, oldobject, sampling)("Skipping old object sample due to lock contention");
    return;
  }
  instance().add(obj, allocated, thread_id, thread);
}

void ObjectSampler::add(HeapWord* obj, size_t allocated, traceid thread_id, JavaThread* thread) {
  assert(obj != NULL, "invariant");
  assert(thread_id != 0, "invariant");
  assert(thread != NULL, "invariant");
  assert(thread->jfr_thread_local()->has_thread_blob(), "invariant");

  if (_dead_samples) {
    scavenge();
    assert(!_dead_samples, "invariant");
  }

  _total_allocated += allocated;
  const size_t span = _total_allocated - _priority_queue->total();
  ObjectSample* sample;
  if ((size_t)_priority_queue->count() == _size) {
    assert(_list->count() == _size, "invariant");
    const ObjectSample* peek = _priority_queue->peek();
    if (peek->span() > span) {
      // quick reject, will not fit
      return;
    }
    sample = _list->reuse(_priority_queue->pop());
  } else {
    sample = _list->get();
  }

  assert(sample != NULL, "invariant");
  sample->set_thread_id(thread_id);

  const JfrThreadLocal* const tl = thread->jfr_thread_local();
  sample->set_thread(tl->thread_blob());

  const unsigned int stacktrace_hash = tl->cached_stack_trace_hash();
  if (stacktrace_hash != 0) {
    sample->set_stack_trace_id(tl->cached_stack_trace_id());
    sample->set_stack_trace_hash(stacktrace_hash);
  }

  sample->set_span(allocated);
  sample->set_object((oop)obj);
  sample->set_allocated(allocated);
  sample->set_allocation_time(JfrTicks::now());
  sample->set_heap_used_at_last_gc(Universe::get_heap_used_at_last_gc());
  _priority_queue->push(sample);
}

void ObjectSampler::scavenge() {
  ObjectSample* current = _list->last();
  while (current != NULL) {
    ObjectSample* next = current->next();
    if (current->is_dead()) {
      remove_dead(current);
    }
    current = next;
  }
  _dead_samples = false;
}

void ObjectSampler::remove_dead(ObjectSample* sample) {
  assert(sample != NULL, "invariant");
  assert(sample->is_dead(), "invariant");
  ObjectSample* const previous = sample->prev();
  // push span onto previous
  if (previous != NULL) {
    _priority_queue->remove(previous);
    previous->add_span(sample->span());
    _priority_queue->push(previous);
  }
  _priority_queue->remove(sample);
  _list->release(sample);
}

void ObjectSampler::weak_oops_do(BoolObjectClosure* is_alive, OopClosure* f) {
  assert(is_created(), "invariant");
  assert(SafepointSynchronize::is_at_safepoint(), "invariant");
  ObjectSampler& sampler = instance();
  ObjectSample* current = sampler._list->last();
  while (current != NULL) {
    if (current->_object != NULL) {
      if (is_alive->do_object_b(current->object())) {
        // The weakly referenced object is alive, update pointer
        f->do_oop(const_cast<oop*>(current->object_addr()));
      } else {
        // clear existing field to assist GC barriers
        current->_object = NULL;
        sampler._dead_samples = true;
      }
    }
    current = current->next();
  }

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