Server lagging at only 25% cpu utilization

I am running a skyfacotry (FTB) Minecraft server for my friends on a VM with MineOS. It is having frequent lag spikes but according to the WebUI the server is steady at .25%. What could be happening and how could I fix it?
If you need more info please tell me. I might need a little more help than usual because I am a newbie at this.

Is it a memory issue?

It shouldn’t be, the vm has 12 gigs allocated to it

But not 12GB to the VM out of a total 12GB right?

no, 12 out of 64 gigabytes of ram.

Skyfactory shouldn’t have any issues as far as lagging. I’m running both a skyfactory and stoneblock world without any issues. (I have like 8 different servers running at once with ~20 total pop)

What kind of system specs do you have? CPU, RAM speed, HDD or SSD.
Is it dual socket?
Are you running other VMs?
What do you have for your jvm args?

its a zenon 16 core, 2666 speed ram, ssd (its being run from a friends imac pro). there are no other vms, and I have not provided the server with any java args.

Well I know from experience on a mac with VMs as of late has issues.

You said that the vm has 12gb allocated to it. Give it 15 gigs and increase the core count to 8.

Under your Minecraft server in the java settings box, set both Xmx and Xms to 10240 and use this in the top jvm args text box

-XX:+UseG1GC -Dsun.rmi.dgc.server.gcInterval=2147483646 -XX:+UnlockExperimentalVMOptions -XX:G1NewSizePercent=20 -XX:G1ReservePercent=20 -XX:MaxGCPauseMillis=50 -XX:G1HeapRegionSize=32M -Dfml.readTimeout=180 -XX:UseSSE=4 -XX:+AlwaysPreTouch -XX:+ParallelRefProcEnabled -XX:+UseAES -XX:+UseAESIntrinsics

and put “nogui” in the bottom one.

Give this a try and report back if there’s a performance difference.

Also open up Activity Monitor on the mac to watch cpu performance after the server has started.
It “should” correlate to the graph on the front page of MineOS gui

I’m always wary to recommend these blanket solutions to problems that they inherently aren’t specifically targeting.

Like, I’m not sure how some of them are useful as troubleshooting, and sometimes wondering how they are useful at all:


Enables hardware-based AES intrinsics for Intel, AMD, and SPARC hardware. Intel Westmere (2010 and newer), AMD Bulldozer (2011 and newer), and SPARC (T4 and newer) are the supported hardware. UseAES is used in conjunction with UseAESIntrinsics.

Hardware intrinsics were added to use Advanced Encryption Standard (AES). The UseAES and UseAESIntrinsics flags are available to enable the hardware-based AES intrinsics for Intel hardware. The hardware must be 2010 or newer Westmere hardware.

Like, why would AES have anything to do with Minecraft?

The default garbage collection interval is once an hour.

This is changing it to once every 600 hours. Is there…a reason you’d want to do that?

At any rate, server lagging at 25% seems like there are things that can be looked at, but I’m again reluctant to think immediately and without profile/logging data that garbage collection is at fault.

I’m sorry, I forgot to edit those two args out.

And as far a garbage collecting, I found that it’s not needed for a world type like skyblock/stoneblock. I’ve been using that arg list for about a month as the servers been online and I haven’t gotten any complainants with lag/worldgen issues and the server is still running without issue.

What VM app are you using?

Thank you so much! i will try this right away!

That makes sense, i’ll leave that out for now

The vm I am using is vituralbox