Howdy, found some useful information on the Runescape Wiki which can help improve your performance in Runescape. I've tried these out myself and as of right now there have been no problems. I'm seeing an immediate benefit in loading times and opening the world. Opening the world map literally takes a second to open!
Increasing maximum heap usage
You can increase the amount of maximum heap the RuneScape client uses and it is often a recommended step in troubleshooting on the official Forum. To do this:
• Open %USERPROFILE%\jagexcache\jagexlauncher\runescape\runescape.prm in Notepad/wordpad.
• Change every instance of -Xmx384m to a higher value; -Xmx512m is recommended
• Save and close the file
Allocating too much memory to the heap can cause game instability. If, after increasing the amount of maximum heap, your client begins to crash to desktop, decrease the maximum heap size and try again.
Using a different garbage collector
You can optionally choose a different garbage collector for the Runescape client to use. This will potentially improve map loading times, and decrease lag caused by garbage collection.
To make the changes to your Client's configuration file:
• Open %USERPROFILE%\jagexcache\jagexlauncher\runescape\runescape.prm in Notepad/wordpad.
• Remove every instance of the following flags
-XX:CompileThreshold=1500
-Xincgc
-XX:+UseConcMarkSweepGC
-XX:+UseParNewGC
• Add the following flags:
-XX:+DisableExplicitGC
-XX:+AggressiveOpts
-XX:+UseAdaptiveGCBoundary
-XX:MaxGCPauseMillis=500
-XX:SurvivorRatio=16
-XX:+UseParallelGC
• Save and close the file
I hope this can help improve your game experience, it's well worth a shot if you ask me! If anything is to go wrong you can always modify