Instructions

Instructions

To generate the hotspot.log file used by JITWatch run your program with the following JVM switches.

-XX:+UnlockDiagnosticVMOptions
-Xlog:class+load=info
-XX:+LogCompilation

The hotspot.log file is generated in the program execution directory. From Java 8 onwards the filename will include the process ID of the Java process, e.g. hotspot_pid860.log

If you want to specify the HotSpot log filename use the VM switch

-XX:LogFile=mylogfile.log

If you want to HotSpot to output the disassembled native code then add the JVM switch
-XX:+PrintAssembly

Along with this parameter is highly recommended to add -XX:+DebugNonSafepoints to gain additional output.

This requires you to use a debug JVM build or have built the hsdis (HotSpot disassembler) binary. The source for hsdis is part of OpenJDK and instructions for building it are here: Building hsdis

-Xlog:class+load=info is required for JITWatch to build its class model; for Java 8 and older use -XX:+TraceClassLoading instead.

Running JITWatch

Requirements for running JITWatch are:

• Oracle JDK or OpenJDK version 7 or higher (a JDK is needed as tools.jar is required)
• JavaFX or OpenJFX for the user interface

You can run JITWatch with Maven, Gradle or the provided shell scripts.

Run with Maven

Create the following Maven file (pom.xml):

<project xmlns="http://maven.apache.org/POM/4.0.0" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>jitwatch</groupId>
    <artifactId>jitwatch-run</artifactId>
    <version>1.3.0</version>
    <build>
        <pluginManagement>
            <plugins>
                <plugin>
                    <groupId>org.codehaus.mojo</groupId>
                    <artifactId>exec-maven-plugin</artifactId>
                    <version>LATEST</version>
                    <executions>
                        <execution>
                            <goals>
                                <goal>java</goal>
                            </goals>
                        </execution>
                    </executions>
                    <configuration>
                        <mainClass>org.adoptopenjdk.jitwatch.launch.LaunchUI</mainClass>                   
                    </configuration>
                </plugin>
            </plugins>
        </pluginManagement>
    </build>

    <dependencies>
        <dependency>
            <groupId>com.chrisnewland</groupId>
            <artifactId>jitwatch</artifactId>
            <version>1.0.0</version>
        </dependency>
    </dependencies>
</project>      

Type the command:

mvn exec:java

Run with Gradle

Create the following Gradle file (build.gradle):

plugins {
    id 'application'
}

mainClassName = 'org.adoptopenjdk.jitwatch.launch.LaunchUI'

repositories {
    jcenter()
}

dependencies {
    runtime 'com.chrisnewland:jitwatch:1.0.0'
}

Type the command:

gradle run

If you already have a build.gradle file, you can call this file something else, like jitWatch.gradle, and then use the following command instead:

gradle -b jitWatch.gradle run

Run with shell scripts

You can also use the startup scripts provided, launchUI.sh for Linux/Mac and launchUI.bat for Windows.