Java garbage collection working properly. Docker not.

[ivory wraith]

Running into an issue where the container's RAM usage will increase over time but never decrease as Java executes garbage collection (Image #1). Server will crash (Image #2) and need to be Killed once the RAM cap is reached. Is there a fix for this using JVM arguments or something else?

java -Xms128M -XX:MaxRAMPercentage=85.0 -verbose:gc -Dterminal.jline=false -Dterminal.ansi=true $( [[ ! -f unix_args.txt ]] && printf %s "-jar server.jar" || printf %s "@unix_args.txt" )

[tame gorge]

i believe this is just a java thing, not in any way related to docker/pterodactyl. reduce the max ram percentage to something like 80 or 75

[jovial tundra]

Do you see "alwaysPreTouch" inside unix_args.txt?

[ivory wraith]

That line does not exist in unix_args.txt in /container/ or in /container/libraries/net/minecraftforge/forge/1.20.1-47.2.6/

[ivory wraith]

This may just be a Java thing as you say but I never see Java's actual usage meet or exceed the 8GB container cap with the JVM arguments set right. By default max ram percentage is 95%. Changing it to 85% should cap my usage to 6.8GB but ptero still says I am exceeding that amount.

[tame gorge]

yeah java is a bit finicky when in memory constrained environments

some of my servers are like 100mib away from the limit but are at 75% max memory amount

[ivory wraith]

I know that people are able to run successful MC servers using ptero. All I need to know is how.

[ivory wraith]

I will try setting it lower

[tame gorge]

this specific server is running at 75% max memory percentage

[ivory wraith]

75% of 8 should be 6GB

What is your uptime on that one?

And active player count/frequency?

[tame gorge]

3d 21h, though it will typically shoot up to that immediately as players join

22 players online right now with that

[ivory wraith]

Do you ever see the number go back down or does it stay at 7.57?

[tame gorge]

typically hovers around the maximum it reaches

if you're really that picky about java GCs memory usage, you can try shenandoah gc on compact mode

[ivory wraith]

Not picky hahaha, I just don't want the server to crash after a couple hours

[tame gorge]

well you can try it either way

this is in compact mode

though this is a lobby server

[ivory wraith]

You're running with Java 17 right?

[tame gorge]

some servers are running java 21, but yeah mostly 17

[ivory wraith]

I'll steal your JVM args 🤣

[tame gorge]

no problem, these are my args for my lobby

java -Xms128M -XX:MaxRAMPercentage=80 -XX:+UnlockDiagnosticVMOptions -XX:+UnlockExperimentalVMOptions -XX:+DebugNonSafepoints -XX:+UseShenandoahGC -XX:ShenandoahGCHeuristics=compact -XX:ShenandoahAllocationThreshold=60 -XX:+UseNUMA -XX:+AlwaysPreTouch -XX:+UseLargePages -XX:+UseTransparentHugePages -Dterminal.jline=false -Dterminal.ansi=true -jar server.jar

[timid smelt]

Do not use the AlwaysPreTouch Aikar flag as it will preallocate all the memory and starve the container causing it to freeze or crash. Aikar's website warns of this.

Remove the flag or lower the Xmx to have overhead for the container, for example, with -Xmx$(({{SERVER_MEMORY}}-512))M

[tame gorge]

its ok support bot i know what im doing

[ivory wraith]

hahhaa you tell it

I'll try out your arg, thank you!

[tame gorge]

you may want to raise or lower ShenandoahAllocationThreshold depending on your servers allocation rate

if you've got a vanilla smp or modded server, i'd decrease it a bit

[ivory wraith]

modded on TerraFirmaGreg 1.20.1

[tame gorge]

beware that shenandoah will use more CPU usage than the default garbage collector

example in the lobby server

[ivory wraith]

Oh that's not too bad... We'll see how it performs on modded