XFS just like EXT4 (I wrote a post about it last year) supports online defragmentation, to manage those volumes on CentOS and Fedora xfsprogs package is needed.
Fragmentation level of XFS volumes can be checked with the command:

[root@CentOS ~]$ xfs_db -c frag -r /dev/sdb1
actual 4491, ideal 4006, fragmentation factor 10.80%

To perform online defragmentation of XFS volumes run the following command:

[root@CentOS ~]$ xfs_fsr -v /dev/sdb1 
/mnt/data1 start inode=0
ino=205: file busy
ino=201 already fully defragmented.

The defragmentation process can take a very long time, if performed on a remote machine I strongly suggest to use screen or a similar tool to prevent accidental disconnections which would probably result in files corruption.