A few days ago I was tweaking my Emacs configuration and I decided to bump the
smex-history-length variable really high to 4096. Everything was fine for
about a week, and then in the last couple of days I noticed that the
was taking a really long time to respond. So I was really scratching my head for
a few hours, trying to figure out why it wouldn't respond promptly and also why
I would sometimes get this really weird error from
(wrong-type-argument number-or-marker-p nil).
Eventually, it occurred to me that the reason for the slowness and the error is
that I had set that history variable to a really insane value. The problem was
not apparent immediately because it took a little while to build that
history list. But once it was big enough,
smex spent a ton of time ranking the
list every time I hit the
M-x chord on the keyboard. I bumped it back down to
16 now and the problems immediately went away. Beware!