82 lines
2.6 KiB
C++
82 lines
2.6 KiB
C++
/*
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* Copyright (c) 2015, 2019, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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#include "precompiled.hpp"
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#include "gc/z/zMetronome.hpp"
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#include "runtime/mutexLocker.hpp"
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#include "runtime/timer.hpp"
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#include "utilities/ticks.hpp"
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ZMetronome::ZMetronome(uint64_t hz) :
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_monitor(Monitor::leaf, "ZMetronome", false, Monitor::_safepoint_check_never),
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_interval_ms(MILLIUNITS / hz),
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_start_ms(0),
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_nticks(0),
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_stopped(false) {}
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bool ZMetronome::wait_for_tick() {
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if (_nticks++ == 0) {
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// First tick, set start time
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const Ticks now = Ticks::now();
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_start_ms = TimeHelper::counter_to_millis(now.value());
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}
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MonitorLocker ml(&_monitor, Monitor::_no_safepoint_check_flag);
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while (!_stopped) {
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// We might wake up spuriously from wait, so always recalculate
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// the timeout after a wakeup to see if we need to wait again.
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const Ticks now = Ticks::now();
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const uint64_t now_ms = TimeHelper::counter_to_millis(now.value());
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const uint64_t next_ms = _start_ms + (_interval_ms * _nticks);
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const int64_t timeout_ms = next_ms - now_ms;
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if (timeout_ms > 0) {
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// Wait
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ml.wait(timeout_ms);
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} else {
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// Tick
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if (timeout_ms < 0) {
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const uint64_t overslept = -timeout_ms;
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if (overslept > _interval_ms) {
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// Missed one or more ticks. Bump _nticks accordingly to
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// avoid firing a string of immediate ticks to make up
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// for the ones we missed.
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_nticks += overslept / _interval_ms;
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}
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}
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return true;
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}
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}
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// Stopped
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return false;
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}
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void ZMetronome::stop() {
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MonitorLocker ml(&_monitor, Monitor::_no_safepoint_check_flag);
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_stopped = true;
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ml.notify();
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}
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