Re: ido-switch-buffer is slow with many buffers; others are fast

[sbaugh]

> With current processing power, I find it strange that filtering with
> a single regexp on a 1000-element list should take a whole second.
> IOW, I suspect that there's more to it than that (e.g. an
> inefficient regexp, or some other cost somewhere).

Ah, you're right. After more investigation, it seems to be that
string-match is extremely inefficient for me for some
reason. Specifically, if case-fold-search is buffer-local or set with
let, (string-match "" "") is about 2000x slower (not exaggeration) than
if case-fold-search is global. (Doesn't matter what case-fold-search is
set to.)

That is,

(setq-default case-fold-search t) (benchmark-run 1000 (string-match "" ""))

is about 2000x faster than

(benchmark-run 1000 (let ((case-fold-search t)) (string-match "" "")))

It seems this isn't (directly) related to my configuration, because a
fresh Emacs doesn't have the issue. Instead, it's something about my
running, 1000-buffer Emacs... not sure what would cause this or how to
fix it.