Server forge issues (1.12.2) (probably java?)

[Narworx]

Hi, 

This week, my and a friend began to play minecraft with some mods (in 1.12.2) on a forge server (which is located on my pc). Then, two days ago we decided to add more mods, and the server console said it needed more ram. So i tried to put 4G. But he said "invalid initial heap size  :  -Xmx4G". With some research i found out i used a old version of java. I changed it and it worked. The server work, but every entity is laggy as hell. They teleport. We thought it was a new mod, so we tested every one of them but it's stay laggy (only for mobs, we can destroy and construct without issues). So i tried to only launch the server with the old mods (the one who were working) and the problem is still here. I have tried every thing i found on internet. (3 version of java as 8u241 and 8u25), tested every mod... Please, you're my last hope. If someone can help me. Thx.

(I'm not english so i'm sorry if there is grammaticals errors)

[Narworx]

The problem is about the lag but this is the log of the first problem if it can help :

 

Picked up _JAVA_OPTIONS: -Xmx512M

Error occurred during initialization of VM

Initial heap size set to a larger value than the maximum heap size

Press any key to continue . . .

[DaemonUmbra]

1.12 is no longer supported on this forum.

Please update to a modern version of Minecraft to receive support.