开发者的自测利器-Hprof命令（寻找cpu热点）

1. 测试代码：
   

    1 public class HProfTest {
    2     public void slowMethod() {
    3         try {
    4             Thread.sleep(1000);
    5         } catch (Exception e) {
    6             e.printStackTrace();
    7         }
    8     }
    9 
   10     public void slowerMethod() {
   11         try {
   12             Thread.sleep(10000);
   13         } catch (Exception e) {
   14             e.printStackTrace();
   15         }
   16     }
   17 
   18     public static void main(String[] args) {
   19         HProfTest test = new HProfTest();
   20         test.slowerMethod();
   21         test.slowMethod();
   22     }
   23 }

   
2. 影响性能点分析：
   1. 类中有两个方法，slowMethod（睡眠1秒，可以理解成该方法执行需要1秒）和slowerMethod(睡眠10秒，可以理解成该方法执行需要10秒)。
   2. 在程序中的方法执行的时间越长越影响性能，那么slowerMethod就是我们预期影响性能的方法，HProf命令究竟以什么形式展示这个影响性能的方法，请往下阅读。

3. hprof命令以及其参数介绍：

   

   /* 
       times：java函数的执行时间
       hprof=cpu是针对cpu统计时间
       interval=10 采样10次 
   */
   -agentlib:hprof=cpu=times,interval=10

   
4. 使用方式：
   1. 点击run-->run configurations-->Java Application-->HProfTest-->选择Arguments选项卡-->在VM arguments框中填入参数
   2. 运行HProfTest
5. 运行结果（会产生新文件java.hprof.txt）：

   1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173

   JAVA PROFILE 1.0.1, created Sat Sep 24 08:01:10 2016   Copyright (c) 2003, 2005, Oracle and/or its affiliates. All rights reserved.   Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:     - Redistributions of source code must retain the above copyright     notice, this list of conditions and the following disclaimer.     - Redistributions in binary form must reproduce the above copyright     notice, this list of conditions and the following disclaimer in the     documentation and/or other materials provided with the distribution.     - Neither the name of Oracle nor the names of its     contributors may be used to endorse or promote products derived     from this software without specific prior written permission.   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.     Header for -agentlib:hprof (or -Xrunhprof) ASCII Output (JDK 5.0 JVMTI based)   WARNING!  This file format is under development, and is subject to change without notice.   This file contains the following types of records:   THREAD START THREAD END      mark the lifetime of Java threads   TRACE           represents a Java stack trace.  Each trace consists                 of a series of stack frames.  Other records refer to                 TRACEs to identify (1) where object allocations have                 taken place, (2) the frames in which GC roots were                 found, and (3) frequently executed methods.   HEAP DUMP       is a complete snapshot of all live objects in the Java                 heap.  Following distinctions are made:                   ROOT    root set as determined by GC                 CLS     classes                 OBJ     instances                 ARR     arrays   SITES           is a sorted list of allocation sites.  This identifies                 the most heavily allocated object types, and the TRACE                 at which those allocations occurred.   CPU SAMPLES     is a statistical profile of program execution.  The VM                 periodically samples all running threads, and assigns                 a quantum to active TRACEs in those threads.  Entries                 in this record are TRACEs ranked by the percentage of                 total quanta they consumed; top-ranked TRACEs are                 typically hot spots in the program.   CPU TIME        is a profile of program execution obtained by measuring                 the time spent in individual methods (excluding the time                 spent in callees), as well as by counting the number of                 times each method is called. Entries in this record are                 TRACEs ranked by the percentage of total CPU time. The                 "count" field indicates the number of times each TRACE                 is invoked.   MONITOR TIME    is a profile of monitor contention obtained by measuring                 the time spent by a thread waiting to enter a monitor.                 Entries in this record are TRACEs ranked by the percentage                 of total monitor contention time and a brief description                 of the monitor.  The "count" field indicates the number of                 times the monitor was contended at that TRACE.   MONITOR DUMP    is a complete snapshot of all the monitors and threads in                 the System.   HEAP DUMP, SITES, CPU SAMPLES|TIME and MONITOR DUMP|TIME records are generated at program exit.  They can also be obtained during program execution by typing Ctrl-\ (on Solaris) or by typing Ctrl-Break (on Win32).   --------   THREAD START (obj=50000191, id = 200002, name="HPROF gc_finish watcher", group="system") THREAD START (obj=50000191, id = 200001, name="main", group="main") THREAD END (id = 200001) THREAD START (obj=50000191, id = 200003, name="DestroyJavaVM", group="main") THREAD END (id = 200003) TRACE 301758:     HProfTest.slowerMethod(HProfTest.java:Unknown line)     HProfTest.main(HProfTest.java:Unknown line) TRACE 301759:     HProfTest.slowMethod(HProfTest.java:Unknown line)     HProfTest.main(HProfTest.java:Unknown line) TRACE 301012:     java.lang.AbstractStringBuilder.append(<Unknown Source>:Unknown line)     java.lang.StringBuffer.append(<Unknown Source>:Unknown line)     java.io.WinNTFileSystem.normalize(<Unknown Source>:Unknown line)     java.io.WinNTFileSystem.normalize(<Unknown Source>:Unknown line) TRACE 300936:     java.lang.AbstractStringBuilder.append(<Unknown Source>:Unknown line)     java.lang.StringBuilder.append(<Unknown Source>:Unknown line)     sun.net.www.ParseUtil.decode(<Unknown Source>:Unknown line)     sun.misc.URLClassPath$JarLoader.<init>(<Unknown Source>:Unknown line) TRACE 301032:     java.lang.CharacterDataLatin1.toLowerCase(<Unknown Source>:Unknown line)     java.lang.Character.toLowerCase(<Unknown Source>:Unknown line)     java.lang.String.toLowerCase(<Unknown Source>:Unknown line)     java.io.WinNTFileSystem.hashCode(<Unknown Source>:Unknown line) TRACE 300937:     java.lang.StringBuilder.append(<Unknown Source>:Unknown line)     sun.net.www.ParseUtil.decode(<Unknown Source>:Unknown line)     sun.misc.URLClassPath$JarLoader.<init>(<Unknown Source>:Unknown line)     sun.misc.URLClassPath$3.run(<Unknown Source>:Unknown line) TRACE 300997:     sun.net.www.ParseUtil.decode(<Unknown Source>:Unknown line)     sun.misc.URLClassPath$JarLoader.<init>(<Unknown Source>:Unknown line)     sun.misc.URLClassPath$3.run(<Unknown Source>:Unknown line)     sun.misc.URLClassPath$3.run(<Unknown Source>:Unknown line) TRACE 300356:     java.lang.Character.toUpperCase(<Unknown Source>:Unknown line)     java.lang.Character.toUpperCase(<Unknown Source>:Unknown line)     java.lang.ProcessEnvironment$NameComparator.compare(<Unknown Source>:Unknown line)     java.lang.ProcessEnvironment$NameComparator.compare(<Unknown Source>:Unknown line) TRACE 300370:     java.lang.ProcessEnvironment.<clinit>(<Unknown Source>:Unknown line)     java.lang.System.getenv(<Unknown Source>:Unknown line)     sun.usagetracker.UsageTrackerClient$2.run(<Unknown Source>:Unknown line)     sun.usagetracker.UsageTrackerClient$2.run(<Unknown Source>:Unknown line) TRACE 300357:     java.lang.Character.toUpperCase(<Unknown Source>:Unknown line)     java.lang.ProcessEnvironment$NameComparator.compare(<Unknown Source>:Unknown line)     java.lang.ProcessEnvironment$NameComparator.compare(<Unknown Source>:Unknown line)     java.util.TreeMap.put(<Unknown Source>:Unknown line) TRACE 300338:     java.lang.ProcessEnvironment$CheckedEntry.getKey(<Unknown Source>:Unknown line)     java.util.AbstractMap.putAll(<Unknown Source>:Unknown line)     java.util.TreeMap.putAll(<Unknown Source>:Unknown line)     java.lang.ProcessEnvironment.<clinit>(<Unknown Source>:Unknown line) TRACE 301036:     java.lang.String.toLowerCase(<Unknown Source>:Unknown line)     java.io.WinNTFileSystem.hashCode(<Unknown Source>:Unknown line)     java.io.File.hashCode(<Unknown Source>:Unknown line)     java.util.HashMap.hash(<Unknown Source>:Unknown line) TRACE 301082:     sun.misc.URLClassPath.getLoader(<Unknown Source>:Unknown line)     sun.misc.URLClassPath.getNextLoader(<Unknown Source>:Unknown line)     sun.misc.URLClassPath.getResource(<Unknown Source>:Unknown line)     java.net.URLClassLoader$1.run(<Unknown Source>:Unknown line) CPU TIME (ms) BEGIN (total = 11076) Sat Sep 24 08:01:21 2016 rank   self  accum   count trace method    1 90.29% 90.29%       1 301758 HProfTest.slowerMethod    2  9.03% 99.32%       1 301759 HProfTest.slowMethod    3  0.04% 99.36%     783 301012 java.lang.AbstractStringBuilder.append    4  0.03% 99.39%     665 300936 java.lang.AbstractStringBuilder.append    5  0.03% 99.41%     665 301032 java.lang.CharacterDataLatin1.toLowerCase    6  0.02% 99.43%     665 300937 java.lang.StringBuilder.append    7  0.02% 99.45%      12 300997 sun.net.www.ParseUtil.decode    8  0.02% 99.47%     398 300356 java.lang.Character.toUpperCase    9  0.02% 99.49%       1 300370 java.lang.ProcessEnvironment.<clinit>   10  0.02% 99.50%     388 300357 java.lang.Character.toUpperCase   11  0.02% 99.52%      42 300338 java.lang.ProcessEnvironment$CheckedEntry.getKey   12  0.02% 99.54%      12 301036 java.lang.String.toLowerCase   13  0.02% 99.56%      14 301082 sun.misc.URLClassPath.getLoader CPU TIME (ms) END

6. 结果分析：

　　

 

http://www.cnblogs.com/aaronL/p/5902386.html