Guide JDK Mission Control - Performance-Analysis Tool

Trance · January 25, 2023

Description

This is not something new, this tool has been used for several years and yet when I ask for a JFR file, many people do not know what it is. The purpose of this topic is to guide you on the correct way for L2J server administrators or developers to find server performance issues through the JMC software. You can improve stability and performance by finding and fixing memory leaks, CPU overloads, deadlocks; garbage collection performance, synchronization performance, I/O performance, and code execution performance. For example, you can record the Game Server when your players are at Baium; mass PvP-ing.

Requirements

Oracle JDK 11 and later.

JDK Mission Control (JMC)

JDK Mission Control (JMC) is a production-time profiling and diagnostics tool. It includes tools to monitor and manage your Java application with very small performance overhead.

Java Management console (JMX) connects to a running JVM and collects and displays key characteristics in real time. It is a tool for monitoring and managing a running JVM instance. The tool presents live data about memory and CPU usage, garbage collections, thread activity, and so on. It also includes a fully featured JMX MBean browser that you can use to monitor and manage MBeans in the JVM and in your Java application.

Flight Recorder (JFR) is a profiling and event collection framework built into the JDK. Flight Recorder allows Java administrators and developers to gather detailed low-level information about how a JVM and Java applications are behaving. You can use JMC, with a plug-in, to visualize the data collected by JFR. Flight Recorder and JMC together create a complete toolchain to continuously collect low-level and detailed runtime information enabling after-the-fact incident analysis.

How-To Do A Flight Record

Windows

If your server is running on Windows, you can use JDK Mission Control (JMC) directly on your VPS/dedicated server for real-time monitoring or recording.

Linux

The best way is to capture a java process (like Game Server) using its ID:

jcmd 21089 JFR.start duration=1800s filename=baium_fight.jfr

21089 is the process ID. You can list your processes by filtering them with the keyword "java".

ps aux | grep java

Output example:

centos   21089  1.7 31.4 9032320 2454828 ?     Sl   03:48  16:36 java -server -Dfile.encoding=UTF-8 -Xmx16G -cp config:./* gold.lineage2.GameServer
centos   26017  0.0  0.0 112812   980 pts/2    S+   19:28   0:00 grep --color=auto java
root     29448  0.5  1.9 3024556 155820 ?      Sl    2022 239:19 java -server -Dfile.encoding=UTF-8 -Xmx256m -cp config:./* gold.lineage2.LoginServer