I restarted my Mac Pro for the first time today and noticed something weird in my Activity Monitor. Process ID 0 kernel_task was using 25% of my CPU, or one whole core. This lasted about 10-15 minutes and then went down to 1% of overall CPU usage. I wondered what is happening, is this a behind the scenes 'tidying up' of drives? Cuts my processing power by a 1/4 if it were to happen on a regular basis. Anybody have any idea what this is?