1 /*
2 * Copyright (C) 2009, Christian Halstrick <christian.halstrick@sap.com>
3 * and other copyright owners as documented in the project's IP log.
4 *
5 * This program and the accompanying materials are made available
6 * under the terms of the Eclipse Distribution License v1.0 which
7 * accompanies this distribution, is reproduced below, and is
8 * available at http://www.eclipse.org/org/documents/edl-v10.php
9 *
10 * All rights reserved.
11 *
12 * Redistribution and use in source and binary forms, with or
13 * without modification, are permitted provided that the following
14 * conditions are met:
15 *
16 * - Redistributions of source code must retain the above copyright
17 * notice, this list of conditions and the following disclaimer.
18 *
19 * - Redistributions in binary form must reproduce the above
20 * copyright notice, this list of conditions and the following
21 * disclaimer in the documentation and/or other materials provided
22 * with the distribution.
23 *
24 * - Neither the name of the Eclipse Foundation, Inc. nor the
25 * names of its contributors may be used to endorse or promote
26 * products derived from this software without specific prior
27 * written permission.
28 *
29 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
30 * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
31 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
32 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
33 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
34 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
35 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
36 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
37 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
38 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
39 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
40 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
41 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
42 */
43
44 package org.eclipse.jgit.util;
45
46 import java.lang.management.ManagementFactory;
47 import java.lang.management.ThreadMXBean;
48
49 /**
50 * A simple stopwatch which measures elapsed CPU time of the current thread. CPU
51 * time is the time spent on executing your own code plus the time spent on
52 * executing operating system calls triggered by your application.
53 * <p>
54 * This stopwatch needs a VM which supports getting CPU Time information for the
55 * current thread. The static method createInstance() will take care to return
56 * only a new instance of this class if the VM is capable of returning CPU time.
57 */
58 public class CPUTimeStopWatch {
59 private long start;
60
61 private static ThreadMXBean mxBean=ManagementFactory.getThreadMXBean();
62
63 /**
64 * use this method instead of the constructor to be sure that the underlying
65 * VM provides all features needed by this class.
66 *
67 * @return a new instance of {@link #CPUTimeStopWatch()} or
68 * <code>null</code> if the VM does not support getting CPU time
69 * information
70 */
71 public static CPUTimeStopWatch createInstance() {
72 return mxBean.isCurrentThreadCpuTimeSupported() ? new CPUTimeStopWatch()
73 : null;
74 }
75
76 /**
77 * Starts the stopwatch. If the stopwatch is already started this will
78 * restart the stopwatch.
79 */
80 public void start() {
81 start = mxBean.getCurrentThreadCpuTime();
82 }
83
84 /**
85 * Stops the stopwatch and return the elapsed CPU time in nanoseconds.
86 * Should be called only on started stopwatches.
87 *
88 * @return the elapsed CPU time in nanoseconds. When called on non-started
89 * stopwatches (either because {@link #start()} was never called or
90 * {@link #stop()} was called after the last call to
91 * {@link #start()}) this method will return 0.
92 */
93 public long stop() {
94 long cpuTime = readout();
95 start = 0;
96 return cpuTime;
97 }
98
99 /**
100 * Return the elapsed CPU time in nanoseconds. In contrast to
101 * {@link #stop()} the stopwatch will continue to run after this call.
102 *
103 * @return the elapsed CPU time in nanoseconds. When called on non-started
104 * stopwatches (either because {@link #start()} was never called or
105 * {@link #stop()} was called after the last call to
106 * {@link #start()}) this method will return 0.
107 */
108 public long readout() {
109 return (start == 0) ? 0 : mxBean.getCurrentThreadCpuTime() - start;
110 }
111 }