magicdev-0.2.7-5 takes too much CPU time (typically 18 percent) without any device activity. This happens on a dual CPU machine with two (idle, empty) CD-ROM drives (on hdc and hdd), one of which is attached via ide-scsi driver. This 18 percent load is excessive, something under 5 percent would be more acceptable, and less than 1 percent would be ideal.
magicdev periodically checks the devices for new media. The indicated CPU load is primarily a function of hardware - e.g. IDE will consume more CPU time than SCSI. There's really nothing that can be done on the magicdev end to reduce the indicated CPU load, but you can take consolation in the ability to turn magicdev off if it is causing real problems, and ignore it if it is not.
The root-cause might be related to https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=179573, but there is not enough data above to be sure.