jstat

Introduction

You can run the jstat command to view the usage of each part of the heap memory and the number of loaded classes.

Installation Mode

Use OpenJDK to install this tool. For Bisheng JDK, it is a built-in tool.

Usage

• If a Java environment is configured, you can directly run the jstat command.
• If no Java environment is not configured, run the ps -ef | grep java command to find the Java process. Then, switch to the JDK bin directory and run the ./jstat command.

  Syntax:

  jstat -gcutil $pid 1000

  

  1000 indicates that statistics are output every 1000 ms.

  Common parameters are as follows:

  Parameter	Description
  -gc	Displays garbage collection statistics (value).
  -gcutil	Displays garbage collection statistics (percentage).
  -class	Displays class loading statistics.
  -compiler	Displays compilation statistics.
  -gccapacity	Displays the capacity and space usage of three generation objects in the VM memory.
  -gcnew	Displays information about young-generation objects.
  -gcnewcapacity	Displays information about young-generation objects and their space usage.
  -gcold	Displays information about old-generation objects.
  -gcoldcapacity	Displays information about old-generation objects and their space usage.
  -printcompilation	Displays execution information about the current VM.