Problem FTB Ultimate 1.1.2 - High server load

[Kerel]

Ubuntu 12.04.2 LTS -> Hosted at my friends house (100Mbit Down, 5Mbit Up)
Ultimate 1.1.2 -> No mods added

Specs

*-cpu
description: CPU
product: AMD Phenom(tm) II X4 955 Processor
vendor: Hynix Semiconductor (Hyundai Electronics)
physical id: 4
bus info: cpu@0
version: AMD Phenom(tm) II X4 955 Processor
serial: To Be Filled By O.E.M.
slot: CPUSocket
size: 800MHz
capacity: 3200MHz
width: 64 bits
clock: 200MHz
capabilities: x86-64 fpu fpu_exception wp vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt pdpe1gb rdtscp 3dnowext 3dnow constant_tsc rep_good nopl nonstop_tsc extd_apicid pni monitor cx16 popcnt lahf_lm cmp_legacy svm extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw ibs skinit wdt npt lbrv svm_lock nrip_save cpufreq
configuration: cores=4 enabledcores=4

description: L1 cache
physical id: 5
slot: L1-Cache
size: 512KiB
capacity: 512KiB
capabilities: pipeline-burst internal varies data
*-cache:1
description: L2 cache
physical id: 6
slot: L2-Cache
size: 2MiB
capacity: 2MiB
capabilities: pipeline-burst internal varies unified
*-cache:2
description: L3 cache
physical id: 7
slot: L3-Cache
size: 6MiB
capacity: 6MiB
capabilities: pipeline-burst internal varies unified
*-memory
description: System Memory
physical id: 13
slot: System board or motherboard
size: 4GiB
*-bank:0
description: [empty]
product: ModulePartNumber00
vendor: Manufacturer00
physical id: 0
serial: SerNum00
slot: DIMM0
*-bank:1
description: [empty]
product: ModulePartNumber01
vendor: Manufacturer01
physical id: 1
serial: SerNum01
slot: DIMM1
*-bank:2
description: DIMM Synchronous 667 MHz (1.5 ns)
product: 9905403-153.A00LF
vendor: Kingston
physical id: 2
serial: 7A842453
slot: DIMM2
size: 2GiB
width: 64 bits
clock: 667MHz (1.5ns)
*-bank:3
description: DIMM Synchronous 667 MHz (1.5 ns)
product: 9905403-153.A00LF
vendor: Kingston
physical id: 3
serial: 7A7E2453
slot: DIMM3
size: 2GiB
width: 64 bits
clock: 667MHz (1.5ns)

Java Version

...@Minecraft:~$ java -version
java version "1.7.0_25"
Java(TM) SE Runtime Environment (build 1.7.0_25-b15)
Java HotSpot(TM) 64-Bit Server VM (build 23.25-b01, mixed mode)

Detailed description

Lately the server load has been going through the roof, yet I found no cause for this in the server logs. I've also tried different parameters to the java startup script. This attempt failed, because I do not know how to optimize it to match my system. We play with 4-5 people at a time, using 3-4 chunkloaders each. We also have a repower "bore" frame and a few spawners. We really did not have any problems until a few days ago. Changing java from openjdk to oracle didn't help much. In fact, it slowed down the system. (Too early to tell)

Did we overload the server?
Theoretically, could the server run FTB with these items and amount of players?

java -server -Xmx4G -Xms3G -Xmn2G -cp /home/feedthebeast/ftbserver.jar -jar /home/feedthebeast/ftbserver.jar nogui

Here is the error I can't get a grasp on...

2013-06-27 02:09:02 [INFO] [STDERR] java.util.ConcurrentModificationException
2013-06-27 02:09:02 [INFO] [STDERR]at java.util.HashMap$HashIterator.nextEntry(HashMap.java:894)
2013-06-27 02:09:02 [INFO] [STDERR]at java.util.HashMap$ValueIterator.next(HashMap.java:922)
2013-06-27 02:09:02 [INFO] [STDERR]at bq.a(SourceFile:24)
2013-06-27 02:09:02 [INFO] [STDERR]at cd.a(SourceFile:114)
2013-06-27 02:09:02 [INFO] [STDERR]at bq.a(SourceFile:25)
2013-06-27 02:09:02 [INFO] [STDERR]at cd.a(SourceFile:114)
2013-06-27 02:09:02 [INFO] [STDERR]at bq.a(SourceFile:25)
2013-06-27 02:09:02 [INFO] [STDERR]at by.a(SourceFile:26)
2013-06-27 02:09:02 [INFO] [STDERR]at cd.a(SourceFile:114)
2013-06-27 02:09:02 [INFO] [STDERR]at bq.a(SourceFile:25)
2013-06-27 02:09:02 [INFO] [STDERR]at cd.a(SourceFile:114)
2013-06-27 02:09:02 [INFO] [STDERR]at bq.a(SourceFile:25)
2013-06-27 02:09:02 [INFO] [STDERR]at cd.a(SourceFile:114)
2013-06-27 02:09:02 [INFO] [STDERR]at ca.a(CompressedStreamTools.java:140)
2013-06-27 02:09:02 [INFO] [STDERR]at aam.a(AnvilChunkLoader.java:198)
2013-06-27 02:09:02 [INFO] [STDERR]at aam.c(AnvilChunkLoader.java:184)
2013-06-27 02:09:02 [INFO] [STDERR]at aiw.b(SourceFile:29)
2013-06-27 02:09:02 [INFO] [STDERR]at aiw.run(SourceFile:22)
2013-06-27 02:09:02 [INFO] [STDERR] at java.lang.Thread.run(Thread.java:724)

Hope this is enough information, let me know if you need more and thanks in advance guys !

 

[cjm721]

If it was working before it is probably something one of you built. I would try deloading areas until you see the cpu usage drop.

 

[Kerel]

Well, it was working with a cpu load of 80% constantly. We had lagspikes up to 130%, I replaced the java back to openjdk and that seemed to solve most of our problems. But we still need to optimise our java for our hardware, don't know how to do that.

We also cheated in the Link Modifier last night so you can port inter-dimension, this also reduces the lagg while traveling/loading.

Deloading with TickThreading or you mean by disabling chunkloaders and testing server load?

 

[cjm721]

I meant by removing chunkloaders and letting the chunks unload. If you have tickthreading it shows you what is causing problems.

 

[sgtdeus]

Anyone know what is causing the error he posted, I am getting the same one on my 1.4.7 FTB ultimate server.

 

[cjm721]

The Concurrent modification is from mods not behaving correctly with each-other.

 

[Kerel]

We only recently installed Greg's Lightning (1.7.1). And we've had that error since the beginning of the server, so any known ftb mods that might be causing this? How do I even start bugtesting something like that?

 

[cjm721]

Don't worry about it is really all you can do. The versions on ultimate are so far back there is not really much bugtesting you can do.

 

[TheChristensen]

Of what I can tell, your server has 4gb of ram installed, right? and you set the parameters 3gb-4gb. Try decreasing this to say something like 2/2.5gb - 3gb and while you're at it... copy all the world data, and reinstall the modpack server. Sometimes things get corrupted and you need start fresh. (But do note: Always back up the current modpack server, if something goes wrong, you still have access to the original files)

 

[Kerel]

Don't worry about it is really all you can do. The versions on ultimate are so far back there is not really much bugtesting you can do.

A bit hard when things get added to the world and the problem gets bigger xD

Of what I can tell, your server has 4gb of ram installed, right? and you set the parameters 3gb-4gb. Try decreasing this to say something like 2/2.5gb - 3gb and while you're at it... copy all the world data, and reinstall the modpack server. Sometimes things get corrupted and you need start fresh. (But do note: Always back up the current modpack server, if something goes wrong, you still have access to the original files)

Trying the mem change out now, will do a fresh reinstall tomorrow, thx for the advice
U2 btw cjm721

 

[Kerel]

No changes at all, any suggestions on avoiding lag? Typical builds?

 

[TheChristensen]

java -Xmx2G -Xms2G -jar /home/feedthebeast/ftbserver.jar nogui

Here try this one next. One thing i've learned is that start from the bottom, go simple then build your way back up, that way you find the problem.

 

[cjm721]

Well TickThreading does help with TPS and can help with finding what is causing issues. Also from TT he has a start script that is as far as from quite a few of us that use it has a very positive effect.

/usr/lib/jvm/java-7-openjdk-amd64/jre/bin/java -server -Xmx16G -XX:UseSSE=4 -XX:+UseConcMarkSweepGC -XX:+UseCMSCompactAtFullCollection -XX:+UseParNewGC -XX:+DisableExplicitGC -XX:+AggressiveOpts -XX:-OmitStackTraceInFastThrow -jar ultimate.jar nogui

Now your going to have to change "/usr/lib/jvm/java-7-openjdk-amd64/jre/bin/java to what your java path is and change the -Xmx16G to what you want to dedicate to your server. Also the ultimate.jar you will need to change to the name of your jar file.