bug#66117: 30.0.50; `find-buffer-visiting' is slow when opening large number of buffers

[Ihor Radchenko]

Ihor Radchenko <yantar92@posteo.net> writes:

> The main contributor is set_default_internal. I _suspect_ (because we
> have non-linear scaling with the number of buffers - 3x increase in the
> number of files lead to ~6x increase in the run time) that the main
> contributor here is let-binding `case-fold-search' - special per-buffer
> variable with no default value.

My suspicion appears to be correct - removing let-binding for
case-fold-search from `abbreviate-file-name' and
`inhibit-local-variables-p' made them disappear from the top of the
reverse call tree.

Then, considering the ubiquity of let-binding case-fold-search across
Elisp code, speeding up let-binding of special per-buffer variables may
give us performance boost across Emacs.

-- 
Ihor Radchenko // yantar92,
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