Re: Reliable after-change-functions (via: Using incremental parsing in Emacs)

[Dmitry Gutov]

On 04.04.2020 16:02, Eli Zaretskii wrote:
> I don't believe these results.  It's night impossible for a -O2
> optimized program to be 5 times faster than a -Og optimized.  And
> benchmark.el doesn't seem to be so different from time-it, modulo the
> function call.  Moreover, Alan's method does time redisplay, whereas
> Dmitry's method does not.

Unfortunately I can confirm the difference.

When Emacs is recompiled with the default optimizations,

  (benchmark 1 '(progn (find-file "src/xdisp.c")))

reports ~0.13s when FS cache is warm (compared to ~0.78 with the most 
recent -Og build here).

And

  (benchmark 1 '(progn (find-file "src/xdisp.c")
                       (goto-char (point-max))
                       (sit-for 0)))

reports ~0.29s.

Maybe CC Mode exercises some primitives that are hit especially hard by 
the lack of optimization.

Emacs looks snappier overall (e.g. during startup, loading my custom 
configuration with all its packages), but probably within the bounds of 
50-70% difference.