ZFS eats memory/L2ARC while doing nothing?

[Nagy, Attila]

Hi,

Yesterday I have created a server with stable/10 at r262152.
Made a zpool on it and left it running.

The whole file system had only some empty directories (needed to 
populate it later for storage) and some programs, which do some reads on 
it (stat'ing files for existence).

Today, I can see these graphs:
https://lh3.googleusercontent.com/-CY8hLr7s6DY/Ux8xgqolTuI/AAAAAAAAKec/5gR99PIhPYw/s800/zfs_mem-day.png
https://lh6.googleusercontent.com/-gbUzPy5U8ko/Ux8xeKOq_zI/AAAAAAAAKeU/ZFpZx3zE4I4/s800/memory-day.png
https://lh5.googleusercontent.com/-KT7DiptLwEA/Ux8xbMXZ9NI/AAAAAAAAKeM/x2ZbHUJVvug/s800/iopsstat-day.png

So it seems ZFS did an average of 5 write IOPS and that L2ARC's side 
constantly grew to a whopping 6.2 GiBs (again: the file system is empty, 
only 42*42 directories were created on it).

Is this normal? What causes this?