I am looking for some tips for getting a FTB Ultimate server server up to speed. I constantly get the "Can't Keep Up" messages.

I am running a FTB ultimate 1.1.2 server on Windows 2008 R2, with an AMD FX 4170 Quad-Core @ 4.20 GHZ and 8 GB of RAM. The server itself is running on a dedicated WD Black SATA 3 drive. This drive is currently only in use by the FTB server.

There are only two of us on the server at the moment, and I am on the same local network. Both of us experience jerkiness and general lag. Lately my friend has been experiencing upwards of one minute just to open the crafting table.

There have been no changes to the FTB server aside from general changes to the GregTech and Advanced solar panel configs. The lag was happening before that as well.

I have noticed that at times the Minecraft server has worlds listed as having 5000+ chunks cached, or close to 2 GB of RAM allocated. The server generally is at 60-70% CPU usage.

My startup config is pretty basic, but is allowing a max of 5GB:

"C:\Program Files\Java\jre7\bin\java" -Xms512M -Xmx5G -jar ftbserver.jar

I am currently running Java 64-bit, version 7 Update 25

  • Something on your server is eating processor cycles. 2GB is way, way too much for 2 users. Any complex redstone? Chunkloaders near mob grinders? Do you use Linkbooks a lot? Anything in general that is constantly running? Jul 30 '13 at 0:26
  • Oh! Also, definitely reduce your 5GB down to 3GB or 2GB. That's way too much. Windows wants to keep about 4GB to itself, so Java reserving 5GB = 9GB. That means lots of your memory is unnecessarily going through a disk-based pagefile cache. Jul 30 '13 at 0:28
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    I run a server for 10 users on 2G max (and it's never needed it all). Whatever the problem is, giving it more RAM is just hiding the problem and reducing it to more normal amount is still advisable. Jul 30 '13 at 3:35
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    Sounds like you should have enough resources. Have you tried creating a brand new map on the server, and seeing if the CPU usage declines? If so, then something in your map is causing minecraft to use a lot of CPU, you can remove your chunk loaders one at a time and unload the chunks to find the cause.
    – Daryl
    Jul 30 '13 at 15:41
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    I'm voting to close this question as off-topic because it's for modded minecraft tech support and we can only help with vanilla minecraft crashes.
    – Virusbomb
    Jul 8 '19 at 18:22

Found a thread on the FTB forum, and while some of the info may be contradictory or misinformation, i did see they were using a special startup config. While I am not entirely postive of what this does....what I can (hopefully) deduce from it is that it is enabling the FTB server to use SS4 cpu instructions and modifying how garbage collection is ran. After running the server with this config, within minutes the "tick lag" on the server disappeared, everything moved very smoothly.... and best of all, CPU usage went from 70% to 14% even with several chunk loaders and a quarry.

Thread found: http://forum.feed-the-beast.com/threads/how-to-make-an-efficient-server.5525/

Startup config used:

"C:\Program Files\Java\jre7\bin\java" -server -Xincgc -Xmx3072M -Xms1024M -Xmn512M -XX:NewRatio=2 -XX:CMSFullGCsBeforeCompaction=1 -XX:SoftRefLRUPolicyMSPerMB=2048 -XX:+CMSParallelRemarkEnabled -XX:+UseParNewGC -XX:+UseAdaptiveSizePolicy -XX:+DisableExplicitGC -Xnoclassgc -oss4M -ss4M -XX:+UseFastAccessorMethods -XX:CMSInitiatingOccupancyFraction=90 -XX:+UseConcMarkSweepGC -XX:UseSSE=4 -XX:+UseCMSCompactAtFullCollection -XX:ParallelGCThreads=4 -XX:+AggressiveOpts -cp "ftbserver.jar" -jar "ftbserver.jar"


Try this one (similar to the one I made for use on my server. But I run 16GB so I allocate 6GB to my minecraft server. I've set yours to 4GB as that should be plenty for 2-16 players.. maybe even more)

java -server -DJINTEGRA_NATIVE_MODE -XX:ThreadPriorityPolicy=42 -XX:+TieredCompilation -XX:UseSSE=3 -Xmn2G -Xms4G -Xmx4G -XX:SurvivorRatio=4 -XX:+UseParNewGC -XX:ParallelGCThreads=2 -XX:+DisableExplicitGC -jar ftbserver.jar -nogui
  • Minecraft is not coded to take advantage of the extra abilities of SSE 4 this is software coding dependent. pointless to use. Oct 29 '13 at 17:21

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