'ssh node "ls -lR"': consumes all memory on the client!

This issue is with a volume exported from the server, when accessed
indirectly via SSH from the server, i.e. not logging into the node:

ssh node "ls -lR /files/export > /dev/null"

The command takes up all available memory (near 4Gb) on the node,
while generating hundreds of thousand of slabs (nfs_inode_cache and
dentry_cache) as seen with slabtop. The system is rather plain Ubuntu:
2.6.15-26-amd64-k8 kernel.

/etc/exports on the server:
/files/export
10.68.0.0/255.255.0.0(sync,no_wdelay,rw,no_root_squash)

/etc/fstab entry on the client node:
home:/files/export /files/export nfs
rw,nosuid,rsize=32768,wsize=32768,tcp 0 0

I'd very much appreciate any pointers on how to treat this problem.

Zoli