Ram Cleaner Pro

The RAM cleaner plugin is open source. It cleans the memory using System.gc(); during the cleaning process, your game may experience slight stuttering. It also clears the server's RAM during players' logins and logouts, if there is an error,
please let me know, you can report it here or write it in the comments.

If you don't want your game to freeze when cleaning memory, you should try these JVM arguments: (-Xmx and -Xms values are omitted)

-XX:+AggressiveOpts -XX:+UseConcMarkSweepGC -XX:+UseParNewGC -XX:+CMSConcurrentMTEnabled -Dsun.rmi.dgc.server.gcInterval=1800000 -XX:+UnlockExperimentalVMOptions -XX:+ExplicitGCInvokesConcurrent -XX:MaxGCPauseMillis=50 -XX:+AlwaysPreTouch -XX:+UseStringDeduplication -Dfml.ignorePatchDiscrepancies=true -Dfml.ignoreInvalidMinecraftCertificates=true -XX:-OmitStackTraceInFastThrow -XX:+OptimizeStringConcat -XX:+UseAdaptiveGCBoundary -XX:NewRatio=3 -Dfml.readTimeout=90 -XX:+UseFastAccessorMethods

This enables concurrent explicit gc so that your game will not freeze during memory cleanings. The JVM arguments options should be found in your Minecraft launcher.
Have a good day.

Commands and Permissions:
/ramclean - permissions: ramcleaner.ramclean
/ramstatus - permissions: ramcleaner.ramstatus