JVM default maxheap setting

I was working with some Java projects with Eclipse, Gradle, Spring Cloud and Microservices architecture, and trying to execute the complete environment setup on my laptop with 8 gigs of ram. It became very hot and noisy with the fan at maximum. The system was very slow and unresponsive and I thought WTF a quad core with 8 gigs is so slow running a bunch of java applications? After going deeper into the problem, I discovered that the default JVM settings for the max heap is a 1/4 of the system RAM!

Set a lower default Max Heap settings for your Java processes in Eclipse

Execute the following command to verify how much is the default setting for the parameter MaxHeapSize

java -XX:+PrintFlagsFinal -version | grep MaxHeapSize

On my machine the output is the following:

uintx MaxHeapSize	:= 2147483648	{product}

That is 2GB of Ram for every process!

Then I decided to configure the default behaviour of eclipse to execute processes with lesser value of “MaxHeapSize”:

1. Go to Eclipse -> Preferences -> Java -> Installed JREs

2. Select your JRE and click Edit

3. Add this command to the Default VM Argument field: -Xmx32m

It stands for maximum 32MB heap size.

I suggest to keep this value low and override it only if needed in Run/Debug configurations. This way you are doing a very elementary memory requirement analysis for your services without spending too much effort. Better than nothing ;)

Adjust gradle daemon Max Heap default in Eclipse Buildship

Working with the gradle plugin for Eclipse (Buildship) I discovered that it also starts a gradle Daemon with Max Heap settings 1024m for each wrapper version of your opened projects. To reduce the max occupied memory, I suggest the following procedure:

1. If possible use only one version of the gradle wrapper so that eclipse will start only one version of the daemon:
   • delete the folder .gradle
   • update gradleVersion in build.gradle

task wrapper(type: Wrapper) {
	gradleVersion = '2.6'
}

1. create a file in every root project directory named gradle.properties with the following content:

org.gradle.jvmargs=-Xms32m -Xmx32m

This way you are telling the daemon to use at maximum 32MB of Ram for the heap.

You can check the memory occupied by the java processes running jconsole from the command line.

Bye, Dino.