Why GNU grep is fast

This is a repost promoting content originally published elsewhere. See more things Dan's reposted.

I am the original author of GNU grep.  I am also a FreeBSD user,
although I live on -stable (and older) and rarely pay attention
to -current.

However, while searching the -current mailing list for an unrelated
reason, I stumbled across some flamage regarding BSD grep vs GNU grep
performance.  You may have noticed that discussion too...