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  JDK comes with tools jinfo
  Add Date : 2017-08-31      
  Jinfo is JDK comes with Java configuration tool. Located under the java bin directory, jinfo the role of real-time view and adjust the parameters of the virtual machine, although the use of the -v parameter Jps command can view the virtual machine starts to display the specified parameter list. But if you want to know it is not clear that the system defaults, you need to use jinfo.

Jinfo is also possible to modify the operation can be adjusted during a portion of the virtual machine parameters.

1, Jinfo command format

jinfo [option] pid

2, commonly used parameters


    jinfo < option> < pid>

      (To connect to a running process)

where < option> is one of:

    -flag < name> to print the value of the named VMflag

    -flag [+ | -] < name> to enable or disable the named VM flag

    -flag < name> = < value> to set thenamed VM flag to the given value

    -h | -help to print this help message

3, the source code

package com.jdkTools;

import java.util.ArrayList;

import java.util.Random;

/ **

 * Simple application, a large number of cycles and create objects for test use JDK comes jinfo

 * Parameters: -Xms30m -Xmx60m


 * /

public class EasyJinfo {

    public byte [] placeHolder = newbyte [1 * 1024]; // placeholder

    public static void main (String [] args) throws Exception {

        while (true) {

            Random random = newRandom ();

            int loops = random.nextInt (10000);

            EasyJinfo jstat = newEasyJinfo ();

            System.out.println ( "...... is building an object:" + loops + "(a)");

            jstat.getLoop (loops); // multiple cycles, resulting in a large number of objects

            Thread.sleep (100);



    public void getLoop (int size) {

        ArrayList < EasyJinfo> list = new ArrayList < EasyJinfo> ();

        for (int i = 0; i < size; i ++) {

            EasyJinfo jstat = newEasyJinfo ();

            list.add (jstat);




4, the operating parameters

* Parameters: -Xms30m -Xmx60m, this parameter is used to start the JVM virtual machine

5, the results (jinfo view, adjust the JVM parameters)

First use JPS find out the process ID

C: \ Program Files \ Java \ jdk1.6.0_25 \ bin> jps -v

5340 Jps -Dapplication.home = C: \ ProgramFiles \ Java \ jdk1.6.0_25 -Xms8m

1768 EasyJinfo -Xms30m -Xmx60m -Dfile.encoding = GBK

2856 -Xms256m-Xmx768m -XX: MaxPermSize = 256m -XX: ReservedCodeCacheSize = 64m-Dosgi.nls.warnings = ignore

Then execute jinfo

C: \ Program Files \ Java \ jdk1.6.0_25 \ bin> jinfo -flagSurvivorRatio 1768

-XX: SurvivorRatio = 8

Note: Many operating parameters can not be adjusted, if this exception can not be adjusted description:

Exception in thread "main" java.io.IOException: Command failed in target VM
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