1/23/2024 0 Comments Hard coded value java meaning![]() Based on this setting, JVM is allocating Max heap size to be 494.9MB (approximately half of 1GB). Here you can see when docker container’s memory is set to ‘-m 1GB’ and ‘-XX:MaxRAMPercentage=50’. # docker run -m 1GB openjdk:10 java -XX:MaxRAMPercentage=50 -XshowSettings:vm -version 1/2 of 1GB) will be allocated to your Java heap size. Say you have allocated 1 GB of memory to your container, then if you configure -XX:MaxRAMPercentage=50, then approximately 512GB (i.e. So, if you are running on older JDK versions, you can’t use this JVM argument. ‘-XX:MaxRAMPercentage’, ‘-XX: MinRAMPercentage’ JVM arguments are supported from Java 8 update 191 and above. XX:MaxRAMPercentage, -XX: MinRAMPercentage Supported Version It is only supported from Java 8 update 131 to Java 8 update 190. This argument has been deprecated in modern Java versions. Say suppose if your application requires 1GB heap size for optimal performance and if container is configured to run with memory size that is less than 1GB then your application will still run but it will suffer from poor performance characteristics.Ĭ. In this option your Java application’s heap size will be derived from the container’s memory size (because it is fraction basis). Improperly specified VM option 'MaxRAMFraction=2.5'Įrror: Could not create the Java Virtual Machine.Įrror: A fatal exception has occurred. # docker run -m 1GB openjdk:8u131 java -XX:+UnlockExperimentalVMOptions -XX:+UseCGroupMemoryLimitForHeap -XX:MaxRAMFraction=2.5 -XshowSettings:vm -version VM See the below example where JVM is failing to start. It is because ‘-XX:MaxRAMFraction’ can take only integer values and not decimal values. When you pass 2.5 as the value, JVM will not start. Say if you want to configure 40% of the docker’s memory size, then we must set ‘-XX:MaxRAMFraction=2.5’. ![]() To learn more about their difference read this article. This name makes us think, ‘-XX:MinRAMFraction’ argument is used to configure minimum heap size. JDK development team could have given a better name than ‘-XX:MinRAMFraction’. Note: Both ‘-XX:MaxRAMFraction’ and ‘-XX:MinRAMFraction’ are used to determine the maximum Java heap size. Based on this setting, JVM is allocating Max heap size to be 494.9MB (approximately half the size of 1GB). Here you can see when the docker container’s memory is set to ‘1GB’ (i.e., -m 1GB) and ‘-XX:MaxRAMFraction=2. # docker run -m 1GB openjdk:8u131 java -XX:+UnlockExperimentalVMOptions -XX:+UseCGroupMemoryLimitForHeap -XX:MaxRAMFraction=2 -XshowSettings:vm -version VM settings: Only if you pass these two JVM arguments then JVM will derive the heap size value from the container’s memory size, otherwise, it will derive the heap size value from the underlying host’s memory size. ![]() If you are going to use ‘-XX:MaxRAMFraction’ JVM argument, make sure to pass these two additional JVM arguments as well ‘-XX:+UnlockExperimentalVMOptions -XX:+UseCGroupMemoryLimitForHeap’. Say you have allocated 1 GB of memory to your container, then if you configure -XX:MaxRAMFraction=2, then approximately ~512GB (i.e. So, if you are using any other version of JDK, you cannot use this option. ‘-XX:MaxRAMFraction’, ‘-XX:MinRAMFraction’ JVM arguments are supported from only Java 8 update 131 to Java 8 update 190. ![]() XX:MaxRAMFraction, -XX:MinRAMFraction Supported Version Let us discuss these JVM arguments, their merits, and shortcomings. There are 3 different options to specify the maximum Java heap size in containers. ![]() If you are porting your application to Containers, you might be wondering how to configure Java heap size in the container’s world? Are there any best practices? In this article, we will discuss the possible JVM arguments that can be used to specify the Java heap size and the best option to choose. When you are running your Java application in physical servers, you would have been using ‘-Xmx’ JVM argument to specify the Java heap size. ![]()
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