 <p>My suspicion is that your Linux VM may be thrashing to swap space.</p> <p>Virtual machines are often limited in their allotted RAM. Have you checked whether it's run out? The 'top' command is useful for this. </p> <p>If you're not familiar with 'top', the upper part of its screen shows general memory and CPU use statistics, which may immediately answer your problem. The worst CPU hogs will be at the head of the processes list that takes up the rest of the screen.</p> <p>If you hit '?' whilst it's running, it'll show you the options to sort the process list: you may want to sort it by memory use (either virtual or hard).</p>