JVM命令-jmap

逃离我推掉我的手 2023-02-28 15:23 18阅读 0赞

## 一、命令概述 ##

jmap 用于生成堆 dump文件，查看堆内对象统计信息、classloader 信息、 finalizer 队列

Usage:
        jmap [option] <pid>
            (to connect to running process)
        jmap [option] <executable <core>
            (to connect to a core file)
        jmap [option] [server_id@]<remote server IP or hostname>
            (to connect to remote debug server)
    
    where <option> is one of:
        <none>               to print same info as Solaris pmap
        -heap                to print java heap summary
        -histo[:live]        to print histogram of java object heap; if the "live"
                             suboption is specified, only count live objects
        -clstats             to print class loader statistics
        -finalizerinfo       to print information on objects awaiting finalization
        -dump:<dump-options> to dump java heap in hprof binary format
                             dump-options:
                               live         dump only live objects; if not specified,
                                            all objects in the heap are dumped.
                               format=b     binary format
                               file=<file>  dump heap to <file>
                             Example: jmap -dump:live,format=b,file=heap.bin <pid>
        -F                   force. Use with -dump:<dump-options> <pid> or -histo
                             to force a heap dump or histogram when <pid> does not
                             respond. The "live" suboption is not supported
                             in this mode.
        -h | -help           to print this help message
        -J<flag>             to pass <flag> directly to the runtime system

## 二、示例 ##

**1、查看进程的内存映像信息**

jmap 28025

**2、显示 Java 堆详细信息**

jmap -heap 28025

**3、显示堆中对象的统计信息（各对象占用大小）**  
**注：最好导出堆快照，用MAT或者Jprofile分析大对象引用。**

jmap -histo:live 28025

**4、生成堆 dump 文件**  
**注：dump内存快照时，会对服务造成一定影响，线上慎用。**

jmap -dump:format=b,file=heapdump.hprof 28025

本文转载自：http://mousycoder.com/thinking-in-jvm/46/