top helps to see what is eating up system resources.  Untarring a large archive
is probably causing your system to hit Swap which impacts the systems
performance due to I/O limitations of hard drives compared to memory or cache.

> My system seems to slow drag really bad just after untarring a large archive.
> It seems that the directory database needs to be updated just after the
> untarring of the archive - this is a guess - maybe it is an ext 2 filesystem
> problem.  I have been plagued with this for many years, and I am sure that I
> am not alone.  Is there some way to eliminate this problem?
> 
> Using:
> Slack 8.1 (But, it was always a problem on any distro that I have used).
> 400 MHZ w/ 384MB RAM