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/u/BallsInDeepFryer
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[SOLVED] VM performance issues — virtualization + Host CPU fixed it
Server is running perfectly now. The issue was the CPU type. If you’re having performance problems: enable virtualization in your BIOS and set your VM’s CPU type to Host. Thanks everyone!
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Hey everyone,
I built a small home server out of old PC parts and I’m running into a weird performance issue with Minecraft.
Hardware:
- Intel i5‑11600K
- 32GB DDR4‑3200 (2×16GB G.Skill Trident)
- Dark Rock 4 Pro
- Samsung 750 EVO SSD
Setup:
- Proxmox host
- VM with Ubuntu 26.04
- 4 vCPUs
- 16GB RAM
- 100GB storage
- Minecraft Fabric 26.2 server
The problem:
As soon as players join, the VM spikes to 100% CPU usage, Spark also reports 100% load, and the server starts spamming “Can’t keep up! 40–100 TPS behind”.
I find this strange because the i5‑11600K should be more than capable of running a Minecraft server. The CPU boosts normally to 4.9GHz, temps are fine, no throttling, no MCE errors. Stress‑ng and Prime95 both pass without issues.
Is Minecraft really this demanding now, or is there something wrong with my VM configuration?
Any insight would be appreciated.
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Update + Additional Information
Playing Minecraft Vanilla only.
I also tested Purpur 26.1.2 using the recommended Aikar’s JVM flags:
java -Xms10G -Xmx10G -XX:+UseG1GC -XX:+ParallelRefProcEnabled -XX:MaxGCPauseMillis=200 \ -XX:+UnlockExperimentalVMOptions -XX:+DisableExplicitGC -XX:+AlwaysPreTouch \ -XX:G1NewSizePercent=30 -XX:G1MaxNewSizePercent=40 -XX:G1HeapRegionSize=8M \ -XX:G1ReservePercent=20 -XX:G1HeapWastePercent=5 -XX:G1MixedGCCountTarget=4 \ -XX:InitiatingHeapOccupancyPercent=15 -XX:G1MixedGCLiveThresholdPercent=90 \ -XX:G1RSetUpdatingPauseTimePercent=5 -XX:SurvivorRatio=32 -XX:+PerfDisableSharedMem \ -XX:MaxTenuringThreshold=1 -Dusing.aikars.flags=https://mcflags.emc.gs \ -Daikars.new.flags=true -jar paper.jar --nogui With these flags, the server stops spamming “overloaded”, but the world loads extremely slowly and players can fall into unloaded void areas. The server also takes much longer to boot the world than expected.
I originally ran Java 26 because of the 26.2 server build, but switched to Java 25 to test stability. After switching, the server crashed once with:
SIGILL (0x4) - fatal error in OpenJDK 25.0.3 Problematic frame: ConcurrentChainedLong2ReferenceHashTable.getAtIndexAcquire() On the second startup, Java 25 actually booted normally, but the same gameplay issues remain. chunks still fail to load, world generation hangs, and players can walk into completely unloaded void areas. So Java 25 doesn’t crash anymore, but it also doesn’t fix the world‑loading problem.
submitted by /u/BallsInDeepFryer
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