1 /*
   2  * Copyright (c) 2015, 2017, 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 #include "precompiled.hpp"
  25 #include "gc/z/zMetronome.hpp"
  26 #include "runtime/mutexLocker.hpp"
  27 #include "runtime/timer.hpp"
  28 #include "utilities/ticks.hpp"
  29 
  30 ZMetronome::ZMetronome(uint64_t hz) :
  31     _monitor(Monitor::leaf, "ZMetronome", false, Monitor::_safepoint_check_never),
  32     _interval_ms(MILLIUNITS / hz),
  33     _start_ms(0),
  34     _nticks(0),
  35     _stopped(false) {}
  36 
  37 uint64_t ZMetronome::nticks() const {
  38   return _nticks;
  39 }
  40 
  41 bool ZMetronome::wait_for_tick() {
  42   if (_nticks++ == 0) {
  43     // First tick, set start time
  44     const Ticks now = Ticks::now();
  45     _start_ms = TimeHelper::counter_to_millis(now.value());
  46   }
  47 
  48   for (;;) {
  49     // We might wake up spuriously from wait, so always recalculate
  50     // the timeout after a wakeup to see if we need to wait again.
  51     const Ticks now = Ticks::now();
  52     const uint64_t now_ms = TimeHelper::counter_to_millis(now.value());
  53     const uint64_t next_ms = _start_ms + (_interval_ms * _nticks);
  54     const int64_t timeout_ms = next_ms - now_ms;
  55 
  56     MonitorLockerEx ml(&_monitor, Monitor::_no_safepoint_check_flag);
  57     if (!_stopped && timeout_ms > 0) {
  58       // Wait
  59       ml.wait(Monitor::_no_safepoint_check_flag, timeout_ms);
  60     } else {
  61       // Tick
  62       return !_stopped;
  63     }
  64   }
  65 }
  66 
  67 void ZMetronome::stop() {
  68   MonitorLockerEx ml(&_monitor, Monitor::_no_safepoint_check_flag);
  69   _stopped = true;
  70   ml.notify();
  71 }