kernel_task and softwareupdate constantly hogging .5 GB of RAM each
kernel_task is, in effect, 'the operating system'.
Every process hangs from it, it's at the top of the entire tree of what processes are running on your machine.

Run Activity Monitor [Applications > Utilities]
From the View menu select 'All Processes, Hierarchically'
Switch to the memory tab
Click the Memory column until the arrow points down

You can now see the 'tree' of processes, which are running inside another, &amp; how much memory each is actually using. Note, for things like web browsers, that each page uses memory in addition to the overall usage for the browser itself.

It has to be said that 6GB RAM isn't much, these days - &amp; using 2GB of that for a VM is not really leaving you with a lot to play with.