Ok, let me summarize:
a) you're using a 200 Mhz CPU. This is sufficient, but barely above the 100
Mhz minimum requirements.
b) you're experiencing high CPU utilization, but can't tell which process is
the cause (gnunetd does not show up in top)
c) you're using an encrypted partition to store the GNUnet data
Well, c) causes the kernel (!) to perform encryption/decryption on any IO
operation. That's where your CPU is going, and since the kernel has no PID,
this is also why it does not show up for any process in b). Also, c) is a
bad idea -- GNUnet already (!) encrypts all of the data that is being stored
in the database, encrypting it again gives you very little additional
security. Worse, it seems to me that it kills your CPU (at the IO-rate that
GNUnet has -- remember, on many machines GNUnet can be IO-bound; on yours it
is likely CPU bound to start with, and by putting encryption on the disk you
make it worse).