I see lots of those on my production server, they come and go and take up lots of CPU time
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
17 root RT 0 0 0 0 S 1661 0.0 4728:03 migration/3
29 root RT 0 0 0 0 S 1508 0.0 4728:03 migration/6