bug#58950: [PATCH] * lisp/subr.el (buffer-match-p): Optimise performance

[Philip Kaludercic <philipk@posteo.net>]

Philip Kaludercic <philipk@posteo.net> writes:

> Tags: patch
>
>
> The below patch is based on a tangent discussion in bug#58839, the below
> patch was written in collaboration with João Távora.  It involves an
> optimisation to `buffer-match-p' that dramatically speeds the execution
> of the function.  This is important for the very least as
> `buffer-match-p' is used for displaying buffer.
>
> Running (benchmark-run 1000 (match-buffers "\\*.+\\*")) I previously got
> (22.822269875 178 15.524474267999977), and with the patch applied
> (0.27100275 2 0.1730835160000197).
>
> There are a few points that can be discussed:
>
> 1. Style.  I wrap the defun in a let (or rather letrec) block to avoid
>    littering the global namespace.  It isn't necessary, and one could
>    argue it makes debugging more difficult.
>
> 2. Caching policy.  Caching is critical to this optimisation.  Just
>    using byte-compilation would cause the above test to slow down to
>    (76.323692627 656 57.088315405).  The question is if the hash map
>    will collect too much garbage over time, and if there is a better
>    approach that could be taken?
>
> In GNU Emacs 29.0.50 (build 3, x86_64-pc-linux-gnu, GTK+ Version
>  3.24.30, cairo version 1.16.0) of 2022-10-31 built on heron
> Repository revision: 462a66e79edcc34ecbeef7cc1604765adfdc038e
> Repository branch: feature/package+vc
> System Description: Guix System
>
> Configured using:
>  'configure --with-pgtk --with-imagemagick
>  PKG_CONFIG_PATH=/gnu/store/ssg343s6ldqdwh30136pnawhbgd0cb6i-profile/lib/pkgconfig:/gnu/store/ssg343s6ldqdwh30136pnawhbgd0cb6i-profile/share/pkgconfig'

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