/*

 * 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(1, &_lock, 0) == 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->has_thread_checkpoint()) {

    JfrCheckpointManager::create_thread_checkpoint(thread);

  }

  assert(tl->has_thread_checkpoint(), "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_checkpoint(), "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_checkpoint(tl->thread_checkpoint());

  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 on to 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::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) {

    ObjectSample* next = current->next();

    if (!current->is_dead()) {

      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 {

        current->set_dead();

        sampler._dead_samples = true;

      }

    }

    current = next;

  }

  sampler._last_sweep = JfrTicks::now();

}

ObjectSample* ObjectSampler::last() const {

  return _list->last();

}

const ObjectSample* ObjectSampler::first() const {

  return _list->first();

}

const ObjectSample* ObjectSampler::last_resolved() const {

  return _list->last_resolved();

}

void ObjectSampler::set_last_resolved(const ObjectSample* sample) {

  _list->set_last_resolved(sample);

}

int ObjectSampler::item_count() const {

  return _priority_queue->count();

}

const ObjectSample* ObjectSampler::item_at(int index) const {

  return _priority_queue->item_at(index);

}

ObjectSample* ObjectSampler::item_at(int index) {

  return const_cast<ObjectSample*>(

    const_cast<const ObjectSampler*>(this)->item_at(index)

                                  );

}

const JfrTicks& ObjectSampler::last_sweep() const {

  return _last_sweep;

}