IMPORTANT:
THIS MOD IS NOT FOR EVERYONE!
Only use this if you are experiencing lag caused by high RAM usage (Which usually happens on very large modpacks) or experiencing crashes caused by OutOfMemoryError.
Otherwise this mod will negatively affect your game experience, because explicit gc takes time and it brings no benefit if your RAM is abundant.
For best experience I recommend using the suggested JVM arguments, see below.
CLIENT ONLY MOD
This mod automatically calls System.gc() to free up your memory. Due to the fact that explicit gc can freeze your game for a short period, the mod watches the player movement and starts to clean up your RAM after the player stays idle for a while.
The memory cleaning process also starts when your RAM usage goes above a certain percent (configurable) or after a long period if none of the above conditions are met (also configurable).
Also you can use the /cleanmemory command to free up your RAM immediately.
More options can be seen in the in-game mod settings.
Note that do NOT include -XX:+DisableExplicitGC in your JVM arguments because the mod will not function at all with it.
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 -XX:ParallelGCThreads=4 -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.