that is not the full argument for GC, and dont put xmx and xms with the same GB, let minecraft consume what it need
-Xms512M -Xmn768m -XX:+DisableExplicitGC -XX:+UseConcMarkSweepGC -XX:+UseParNewGC -XX:+UseNUMA -XX:+CMSParallelRemarkEnabled -XX:MaxTenuringThreshold=15 -XX:MaxGCPauseMillis=30...