My MacBook Air is showing 1.1 GB of utilized memory (image 1) for kernel_task. I think this cause for alarm.
I've chosen to include the Parallels VM process (prl_vm_app) in the image as well, simply because its memory utilization is large (large but reasonable) and it may be associated with the underlying kernel_task issue. (It's worth noting that if I shutdown my Parallels VM process and reboot my Mac, that kernel_task comes back at about 0.64 GB, but doesn't jump to 1.1 GB until I boot up my Parallels VM.)
I'm inclined to think, that I do have an issue. Take a look at the summary data for the my Mac's memory (image 2). This is with Parallels VM running.