Use of the Jmap command (Java Memory Map)

Jmap can be used for reference:

Official Document Http://docs.oracle.com/javase/6/docs/technotes/tools/share/jmap.html

and this blog http://blog.csdn.net/fenglibing/article/details/6411953

This article mainly introduces several parameters commonly used by Jmap as their own memos. Note that if you are using a 64-bit JVM, you need to add-j-d64 when using Jmap

1. Print the number of instances per class, memory consumption, class full name information. Live sub-parameters, counting only the number of live objects.

> Jmap-histo:live 6824

Num     #instances         #bytes  class name----------------------------------------------   1:          1232         238144  [C   2:           414          48184  <constMethodKlass>   3:          32712  [B   4 :           414          29864  <methodKlass>   5:          29512  <constantPoolKlass>   6:          1084          26016  java.lang.String

2, print the permanent generation of ClassLoader related information

>jmap-permstat 6824

Class_loader    Classes bytes   Parent_loader   alive?  type<bootstrap>     382     1684072   null          live    <internal>0x2a3a7fe0      0       0         Null          live    sun/misc/[email protected]0x2a3aa748      6       51592   0x2a3a7fe0      Live    sun/ Misc/[email protected]

3, showing the allocation and use of memory, for understanding the JVM memory allocation is very useful,displays information about the memory of the young generation, the old age, and the permanent generation.

>jmap-heap 6824

Using Thread-local object allocation. Mark Sweep Compact gcheap Configuration:   minheapfreeratio = 40

4, the most commonly used to get memory dump

can refer to http://blog.csdn.net/aitangyong/article/details/24012535 this blog

Use of the Jmap command (Java Memory Map)