OSX Mavericks using way too much RAM

So I found the same thing with my iMac: Mavericks seemed to be chewing through a lot more RAM than Lion or Mountain Lion.

I found a solution though that doesn't require a reboot: “Using the Purge Command in OS X Mavericks”

Simply run sudo purge (it’ll ask you for your password) and it purges the unused memory the OS is hanging onto.

I freed up over 5GB this way without any hitches although the system appears to hang for a moment or two while it’s doing this purge.

I experienced kernel_task ballooning up to 20GB of RAM and saturating (but not releasing) all available RAM, which essentially froze all of my running apps. Through trial and error I found that it was a runaway R process, as after I quit the R application, the kernel_task went back down to a reasonable 1GB (the R.app did not require more than 1GB of memory at that time).

So the specific fix for my scenario was to restart the R.app application. You might try quitting all running apps one-by-one to systematically figure out which one might be interacting with kernel_task and causing the issue.