open file GameServer_loop.sh with some text editor and change this -Xms1024m -Xmx1024m
on line
java -Djava.util.logging.manager=com.l2jserver.util.L2LogManager -Xms1024m -Xmx1024m -cp ./../libs/*:l2jserver.jar com.l2jserver.gameserver.GameServer > log/stdout.log 2>&1
you can use
-Xms1024m -Xmx1024m >>>> 1GB RAM
-Xms2024m -Xmx2024m >>>> 2GB RAM
-Xms3024m -Xmx3024m >>>> 3GB RAM
-Xms4024m -Xmx4024m >>>> 4GB RAM
-Xms5024m -Xmx5024m >>>> 5GB RAM
-Xms6024m -Xmx6024m >>>> 6GB RAM
or
-Xms1g -Xmx1g >>>> 1GB RAM
-Xms2g -Xmx2g >>>> 2GB RAM
-Xms3g -Xmx3g >>>> 3GB RAM
-Xms4g -Xmx4g >>>> 4GB RAM
-Xms5g -Xmx5g >>>> 5GB RAM
-Xms6g -Xmx6g >>>> 6GB RAM