heater's Introduction

heater

Just a small Java program which loads an image over and over again until an OutOfMemory is reached.

The goal is to test the upper limit of the Java heap, combined with cgroup limits inside an container.

To print the configured values in the JVM add: -XX:+PrintFlagsFinal.

The Docker container can be be pulled from: ninckblokje/heater. For Kubernetes pod.yaml is included.

Notes:

The JVM is JDK 17
All the output is in KB
The JVM will take about 25% of the RAM as heap per default
A JVM requires memory for heap, non heap and other thins like sockets
Container is build using jib-maven-plugin

Documentation:

No limits

Command:

docker run ninckblokje/heater

Output:

Picked up JAVA_TOOL_OPTIONS: -XX:+UnlockExperimentalVMOptions -XX:+UseCGroupMemoryLimitForHeap
-- 1
free memory: 29812304
total memory: 30408704
max memory: 421527552
-- 2
free memory: 24655952
total memory: 30408704
max memory: 421527552

400 MB limit

Command:

docker run -m 400m ninckblokje/heater

Output:

Picked up JAVA_TOOL_OPTIONS: -XX:+UnlockExperimentalVMOptions -XX:+UseCGroupMemoryLimitForHeap
-- 1
free memory: 7781584
total memory: 8257536
max memory: 127729664
-- 2
free memory: 2793024
total memory: 8257536
max memory: 12772966

50% memory limit

Command:

docker run -m 1g -e 'JAVA_TOOL_OPTIONS=-XX:MaxRAMPercentage=50.0 -XX:+UnlockExperimentalVMOptions -XX:+UseCGroupMemoryLimitForHeap' ninckblokje/heater

Output:

Picked up JAVA_TOOL_OPTIONS: -XX:MaxRAMPercentage=50.0 -XX:+UnlockExperimentalVMOptions -XX:+UseCGroupMemoryLimitForHeap
-- 1
free memory: 15797952
total memory: 16318464
max memory: 518979584
-- 2
free memory: 10809392
total memory: 16318464
max memory: 518979584