I was in a single player world. Having a solar evaporation plant from mekanism for my reactor and other things. I decided to chunk load the area with dimensional anchors. Problem is, the log starts spamming with server overloaded warnings and breaking blocks takes AGES when I WASN'T inside the RFTools dimension. I typed "/cofh tps" to see which dimension is having lag issues and it is exactly the flat desert world that I created. It dropped down to 4.16 tick/s (Normally should be 20 tick/s). I don't know what caused it though.

1.5GB ram is really very low for modded MC. Not much that can be done about this from RFTools point of view.

Can you see if this also happens with other chunkloaders?

I just tired with MFR's chunk loader. Nope. I think last time I logged off inside a RFTools dimenion and when I came back, the game dropped to 0 fps and I have no clue what happened. Absolute insane lag. I was forced to MCEdit myself back to the overworld. Then, this issue happened. I will try to make another dimension and see if this issue is still happening.

I think I messed up that RFTools dimension beacuse of that crash. It amazingly chunk load ITSELF without a chunk loader in the world.

That doesn't seem possible. How do you know that it is chunkloading itself?

I am not 100% sure that it is chunk loading, but here's what the "/cofh tps" output as.

Overall: 0.92 TPS/1084.22MS (4%)
Overworld [0]: 20.00 TPS/11.88MS (100%)
Nether [-1]: 20.00 TPS/0.05MS (100%)
Underdark [-100]: 20.00 TPS/0.08MS (100%)
Spirit World [-37]: 20.00 TPS/0.03MS (100%)
Torment [-38]: 20.00 TPS/0.03MS (100%)
Mirror [-39]: 20.00 TPS/0.02MS (100%)
rftools dimension [11]: 0.97 TPS/1028.87MS (4%)
The Last Millenium [-112]: 20.00 TPS/0.23MS (100%)
Twilight Forest [7]: 20.00 TPS/0.04MS (100%)
Mining World [6]: 20.00 TPS/49.11MS (100%)

I got 5 RFTools (id 11-15) dimensions and only id 11 is on the list, but that was just my assmption.
Should I delete all the data inside that dimension and see if that solves it?

Hmm perhaps. What exaclty is in that dimension?

That was just a desert flat world full of marble from chisel. With 15 solar evaporation towers, 64 solar neutron activators, 64 electric pumps and more (All from Mekanism) running under sunlight
EDIT: Also, I just created another desert flat world but with cobblestone. It worked perfectly (20 TPS, and it disappears from the list when I was in the overworld). So it is definately a messed up RFTools world. However, does deleting the data on a RFTools dimension corrupts the level?

That was just a desert flat world full of marble from chisel

It might also be a compatability issue with Chisel as well

it disappears from the list when I was in the overworld

All that means is that (more then likely) the RFTools dimension you created just got unloaded - which is good server wise. But if you build all of those Mekanism devices and structures you will need to keep those areas chunk loaded. I suggest ChickenChunks to just test

The thing is. Whenever I tried to dial my transmitter to that RFTools dimension. Forge(I think) automatically chunk load(probably it chunk loaded a bad chunk?) that dimension. I have removed all chunk loaders(I originally used dimensional anchors to chunk load a 5x5 chunk area) in that area. When I leave the dimension, the dimension did not unload itself correctly, causing the server thread overloading. I'm gonna just adbandon that glitched dimension and make a new one, but using cobblestone as the material.

Whats the CPU speed (and cores), and the amount of ram you have allocated to the forge server instance?

Low TPS (usually) means not enough server resources assigned.

I am pretty sure that was not lag. I abandoned the world and it has no lag at all. But here are the specs.
Intel i3-2130 3.30 GHz
1.5 GB RAM allocated (I only got 4 GB in my computer. That is the maxmium I can put)
Using the lastest version of Java 7.