| /* |
| * Copyright (C) 2009, Christian Halstrick <christian.halstrick@sap.com> and others |
| * |
| * This program and the accompanying materials are made available under the |
| * terms of the Eclipse Distribution License v. 1.0 which is available at |
| * https://www.eclipse.org/org/documents/edl-v10.php. |
| * |
| * SPDX-License-Identifier: BSD-3-Clause |
| */ |
| |
| package org.eclipse.jgit.util; |
| |
| import java.lang.management.ManagementFactory; |
| import java.lang.management.ThreadMXBean; |
| |
| /** |
| * A simple stopwatch which measures elapsed CPU time of the current thread. CPU |
| * time is the time spent on executing your own code plus the time spent on |
| * executing operating system calls triggered by your application. |
| * <p> |
| * This stopwatch needs a VM which supports getting CPU Time information for the |
| * current thread. The static method createInstance() will take care to return |
| * only a new instance of this class if the VM is capable of returning CPU time. |
| */ |
| public class CPUTimeStopWatch { |
| private long start; |
| |
| private static ThreadMXBean mxBean=ManagementFactory.getThreadMXBean(); |
| |
| /** |
| * use this method instead of the constructor to be sure that the underlying |
| * VM provides all features needed by this class. |
| * |
| * @return a new instance of {@link #CPUTimeStopWatch()} or |
| * <code>null</code> if the VM does not support getting CPU time |
| * information |
| */ |
| public static CPUTimeStopWatch createInstance() { |
| return mxBean.isCurrentThreadCpuTimeSupported() ? new CPUTimeStopWatch() |
| : null; |
| } |
| |
| /** |
| * Starts the stopwatch. If the stopwatch is already started this will |
| * restart the stopwatch. |
| */ |
| public void start() { |
| start = mxBean.getCurrentThreadCpuTime(); |
| } |
| |
| /** |
| * Stops the stopwatch and return the elapsed CPU time in nanoseconds. |
| * Should be called only on started stopwatches. |
| * |
| * @return the elapsed CPU time in nanoseconds. When called on non-started |
| * stopwatches (either because {@link #start()} was never called or |
| * {@link #stop()} was called after the last call to |
| * {@link #start()}) this method will return 0. |
| */ |
| public long stop() { |
| long cpuTime = readout(); |
| start = 0; |
| return cpuTime; |
| } |
| |
| /** |
| * Return the elapsed CPU time in nanoseconds. In contrast to |
| * {@link #stop()} the stopwatch will continue to run after this call. |
| * |
| * @return the elapsed CPU time in nanoseconds. When called on non-started |
| * stopwatches (either because {@link #start()} was never called or |
| * {@link #stop()} was called after the last call to |
| * {@link #start()}) this method will return 0. |
| */ |
| public long readout() { |
| return (start == 0) ? 0 : mxBean.getCurrentThreadCpuTime() - start; |
| } |
| } |