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

[Dmitry Gutov]

On 12/12/2023 20:36, Eli Zaretskii wrote:
> > From: Ihor Radchenko<yantar92@posteo.net>
> > Cc:monnier@iro.umontreal.ca,dmitry@gutov.dev,66117@debbugs.gnu.org
> > Date: Tue, 12 Dec 2023 17:44:15 +0000
> >
> > Eli Zaretskii<eliz@gnu.org>  writes:
> >
> > > >    #define BVAR(buf, field) (buffer_overrides->field ## _ == UNSET ?\
> > > >                                (buf)->field ## _ :\
> > > >                               buffer_overrides->field ## _)
> > > >
> > > >    and replace the loop with simply setting buffer_overrides slot.
> > > So for starters, we make each BVAR more expensive, i.e. make Emacs
> > > uniformly slower (because we call BVAR all over the place).
> > Yes, although I do not believe that it will have large impact in
> > practice. It is just an extra == comparison.
> We've seen how similar extra comparisons slow down Emacs when we
> introduced symbols-with-location.  IMO, BVAR might be even more
> expensive, since it is used much more frequently and widely.

We also have dynamic variable bindings all over the place, so it might 
be worth a try (with measurements).