Java memory overflow analysis tool: actual use of jmap

Jmap is used to solve the problem of system tomcat always holding the memory to the header and then crashing.
1. Use commands
If the environment is linux + jdk1.5 or above, this tool comes with the path under JDK_HOME/bin /.
Jmap-histo pid> a. log

2. output result summary
Size Count Class description
-------------------------------------------------------
353371288 9652324 char []
230711112 9612963 java. lang. String
139347160 114865 byte []
76128096 3172004 java. util. Hashtable $ Entry
75782280 3157595 com. test. util. IPSeeker $ IPLocation
25724272 9115 java. util. Hashtable $ Entry []
9319968 org. apache. tomcat. util. buf. MessageBytes
8533856 32889 int []

A large number of strings and custom object com. test. util. IPSeeker $ IPLocation exist. Check the program and find that memory overflow exists here. After the modified program goes online, it uses jmap to capture memory data again: www.2cto.com

146881712 207163 byte []
98976352 354285 char []
42595272 53558 int []
11515632 479818 java. util. HashMap $ Entry
9521896 59808 java. util. HashMap $ Entry []
8887392 370308 com. test. bean. UnionIPEntry
8704808 org. apache. tomcat. util. buf. MessageBytes
8066880 336120 java. lang. String

Eliminate memory overflow.
Note: When using this jmap, the jvm is in a suspended state and can only be used to solve the problem when the service is paralyzed. Otherwise, service interruption may occur.