tips'n'tricks for ram usage

hey there,
i'm planning to run a new minecraft server soon and i figured that it would make sense to ask you guys if you have any tips and/or tricks for my server's ram usage because i feel like something weird is going on at the moment

i am using the latest purpur 1.21.4 build with the aikar's flags and no plugins, and it was at 2.1 gib ram usage when it was idle after restarting it, but once a player joins it shoots up to like 6.2 gib, even though there is a single player on. once the player leaves it just stays on that amount of usage

yes i know that java will use the ram it gets but on my old server that i used to have, the ram usage would drop again once a player has left the server, which is not the case here.

so once again, please let me know if you have any suggestions or anything to optimise my server's ram usage so it doesn't become a problem later on once i set up the server with plugins

here's my startup command and the before and after a player joins the server after a restart:

java -Xms16384M -Xmx16384M -XX:+DisableExplicitGC -XX:+ParallelRefProcEnabled -XX:+PerfDisableSharedMem -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC -XX:G1HeapRegionSize=8M -XX:G1HeapWastePercent=5 -XX:G1MaxNewSizePercent=40 -XX:G1MixedGCCountTarget=4 -XX:G1MixedGCLiveThresholdPercent=90 -XX:G1NewSizePercent=30 -XX:G1RSetUpdatingPauseTimePercent=5 -XX:G1ReservePercent=20 -XX:InitiatingHeapOccupancyPercent=15 -XX:MaxGCPauseMillis=200 -XX:MaxTenuringThreshold=1 -XX:SurvivorRatio=32 -Dusing.aikars.flags=https://mcflags.emc.gs -Daikars.new.flags=true -jar server.jar nogui