/*

 * Copyright (c) 2017, 2018, 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 "logging/log.hpp"

#include "jfr/jfrEvents.hpp"

#include "jfr/periodic/jfrThreadCPULoadEvent.hpp"

#include "jfr/support/jfrThreadId.hpp"

#include "jfr/support/jfrThreadLocal.hpp"

#include "jfr/utilities/jfrTime.hpp"

#include "utilities/globalDefinitions.hpp"

#include "runtime/os.hpp"

#include "runtime/thread.inline.hpp"

#include "runtime/threadSMR.inline.hpp"

jlong JfrThreadCPULoadEvent::get_wallclock_time() {

  return os::javaTimeNanos();

}

int JfrThreadCPULoadEvent::_last_active_processor_count = 0;

int JfrThreadCPULoadEvent::get_processor_count() {

  int cur_processor_count = os::active_processor_count();

  int last_processor_count = _last_active_processor_count;

  _last_active_processor_count = cur_processor_count;

  // If the number of processors decreases, we don't know at what point during

  // the sample interval this happened, so use the largest number to try

  // to avoid percentages above 100%

  return MAX2(cur_processor_count, last_processor_count);

}

// Returns false if the thread has not been scheduled since the last call to updateEvent

// (i.e. the delta for both system and user time is 0 milliseconds)

bool JfrThreadCPULoadEvent::update_event(EventThreadCPULoad& event, JavaThread* thread, jlong cur_wallclock_time, int processor_count) {

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

  jlong cur_cpu_time = os::thread_cpu_time(thread, true);

  jlong prev_cpu_time = tl->get_cpu_time();

  jlong prev_wallclock_time = tl->get_wallclock_time();

  tl->set_wallclock_time(cur_wallclock_time);

  // Threshold of 1 ms

  if (cur_cpu_time - prev_cpu_time < 1 * NANOSECS_PER_MILLISEC) {

    return false;

  }

  jlong cur_user_time = os::thread_cpu_time(thread, false);

  jlong prev_user_time = tl->get_user_time();

  jlong cur_system_time = cur_cpu_time - cur_user_time;

  jlong prev_system_time = prev_cpu_time - prev_user_time;

  // The user and total cpu usage clocks can have different resolutions, which can

  // make us see decreasing system time. Ensure time doesn't go backwards.

  if (prev_system_time > cur_system_time) {

    cur_cpu_time += prev_system_time - cur_system_time;

    cur_system_time = prev_system_time;

  }

  jlong user_time = cur_user_time - prev_user_time;

  jlong system_time = cur_system_time - prev_system_time;

  jlong wallclock_time = cur_wallclock_time - prev_wallclock_time;

  jlong total_available_time = wallclock_time * processor_count;

  // Avoid reporting percentages above the theoretical max

  if (user_time + system_time > wallclock_time) {

    jlong excess = user_time + system_time - wallclock_time;

    if (user_time > excess) {

      user_time -= excess;

      cur_user_time -= excess;

      cur_cpu_time -= excess;

    } else {

      cur_cpu_time -= excess;

      excess -= user_time;

      user_time = 0;

      cur_user_time = 0;

      system_time -= excess;

    }

  }

  event.set_user(total_available_time > 0 ? (double)user_time / total_available_time : 0);

  event.set_system(total_available_time > 0 ? (double)system_time / total_available_time : 0);

  tl->set_user_time(cur_user_time);

  tl->set_cpu_time(cur_cpu_time);

  return true;

}

void JfrThreadCPULoadEvent::send_events() {

  Thread* periodic_thread = Thread::current();

  JfrThreadLocal* const periodic_thread_tl = periodic_thread->jfr_thread_local();

  traceid periodic_thread_id = periodic_thread_tl->thread_id();

  const int processor_count = JfrThreadCPULoadEvent::get_processor_count();

  JfrTicks event_time = JfrTicks::now();

  jlong cur_wallclock_time = JfrThreadCPULoadEvent::get_wallclock_time();

  JavaThreadIteratorWithHandle jtiwh;

  while (JavaThread* jt = jtiwh.next()) {

    EventThreadCPULoad event(UNTIMED);

    if (JfrThreadCPULoadEvent::update_event(event, jt, cur_wallclock_time, processor_count)) {

      event.set_starttime(event_time);

      if (jt != periodic_thread) {

        // Commit reads the thread id from this thread's trace data, so put it there temporarily

        periodic_thread_tl->set_thread_id(JFR_THREAD_ID(jt));

      } else {

        periodic_thread_tl->set_thread_id(periodic_thread_id);

      }

      event.commit();

    }

  }

  log_trace(jfr)("Measured CPU usage for %d threads in %.3f milliseconds", jtiwh.length(),

    (double)(JfrTicks::now() - event_time).milliseconds());

  // Restore this thread's thread id

  periodic_thread_tl->set_thread_id(periodic_thread_id);

}

void JfrThreadCPULoadEvent::send_event_for_thread(JavaThread* jt) {

  EventThreadCPULoad event;

  if (event.should_commit()) {

    if (update_event(event, jt, get_wallclock_time(), get_processor_count())) {

      event.commit();

    }

  }

}