tar x cpu bound

[Edgar Fuß <ef%math.uni-bonn.de@localhost>]

Is it expected that, when writing to SSDs, tar x of an archive containing 
relatively small files (11GB in 600k files) is completely cpu bound (system) 
with the discs nearly idle?

Up to what point exactly is the time spent in the kernel attribited to the 
tar process? File system  yes, I guess, but what about time spent in 
RAIDframe, scsipi and the actual device driver?