[OpenAFS] accessing R/O volume becomes slow

[Hans-Werner Paulsen]

Hello,
this is on Linux 3.14.8 x86_64, and OpenAFS 1.6.9. The machine is 
running normally for several months, and then accessing a specific R/O 
volume (e.g. ls -lR <large_volume>) becomes slow. Accessing the R/W 
version of this volume works normally. Accessing other R/O volumes, 
which have the same size and number of files, works normally. Accessing 
the R/O version of the problem volume from other clients works normally.
The command "fs flushall" does not solve the problem. The (second) "ls 
-lR" command needs 10 seconds on the R/O, and 2 seconds on the R/W 
version of this volume.
Accessing the R/O version from other fileservers (using fs 
setserverprefs) does not change anything.
Checking the machine I see more than 5 million of afs_inode_cache slab 
entries. Is this normal? Any hint how to proceed?
Best regards,
HW