xfs_fsr problem

[Icewind <icewind_cst@xxxxxxx>]

Hi all,
         I have used xfs_fsr to defrag the harddisk partitions.I found that 
when there are some big files (such as a file is big than 4GB) and the 
partition is almost full (40G total , 13% free),the xfs_fsr will be crashed , 
and the computer has no response.
        I use "-d -v" options to view what's wrong with that ,but there is no 
any userful information. I find that only 1-2M memory free in 64M RAM. Anyone 
can help me find out what problem about these?