To fine tune performance in Apache, consider using RedirectMatch instead of Rewrite rules. Here are some tips!
Part of mod_alias is something called RedirectMatch. This is a better way to do 301 redirects or other types of redirects than using mod_rewrite for better performance.
One example is, say you wish to redirect non-www to www for your domain. Here is how you do it with mod_alias and RedirectMatch:
RedirectMatch (.*) http://www.example.com$1
You can have Apache issue HTTP 301 as follows:
RedirectMatch 301 (.*) http://www.example.com$1