Is UseCGroupMemoryLimitForHeap enabled?

[alvarlagerlof]

I'm having trouble correctly setting memory limits, I believe should be done at the Docker level, and not JVM only. Is the JDK you're using in
the image using UseCGroupMemoryLimitForHeap? Also, why that version in particular. Why not OpenJDK?

I'm seeing a default max and min of 1G. Can I disable this?

[itzg]

All of the base image JVMs are using container-aware memory support (the flag is UseContainerSupport BTW):

> docker run --rm --entrypoint bash itzg/minecraft-server -c "java -XX:+PrintFlagsFinal -version|grep -i container"
openjdk version "16.0.2" 2021-07-20
OpenJDK Runtime Environment Temurin-16.0.2+7 (build 16.0.2+7)
OpenJDK 64-Bit Server VM Temurin-16.0.2+7 (build 16.0.2+7, mixed mode, sharing)
     bool PreferContainerQuotaForCPUCount          = true                                      {product} {default}
     bool UseContainerSupport                      = true                                      {product} {default}

> docker run --rm --entrypoint bash itzg/minecraft-server:java8-multiarch -c "java -XX:+PrintFlagsFinal -version|grep -i container"
openjdk version "1.8.0_302"
OpenJDK Runtime Environment (Temurin)(build 1.8.0_302-b08)
OpenJDK 64-Bit Server VM (Temurin)(build 25.302-b08, mixed mode)
     bool PreferContainerQuotaForCPUCount           = true                                {product}
     bool UseContainerSupport                       = true                                {product}

however, what you have noticed is the ultimate problem. I need to adjust the scripts to allow MEMORY to be unset and leave the JVM to calculate from the container limits.

I'll finally get started on #742

[itzg]

I added an example to https://github.com/itzg/docker-minecraft-server#memory-limit

[alvarlagerlof]

Thanks for the quick reponses!

[alvarlagerlof]

I'm seeing this (free is host, not container) followed by it attempting to use more memory than it has. Am I missing something?

[alvarlagerlof]

Considering those default parameters, podman run --rm -m 128M -e DEBUG_MEMORY=true -e EULA=TRUE itzg/minecraft-server seems to output the wrong thing for me. (low mem to demonstrate)

[itzg]

It's using free -m, which yeah apparently isn't container/cgroup aware. Maybe there's an argument I can add there to tell it to do so.