Re: Redisplay slower in Emacs 28 than Emacs 27

[Gregory Heytings]

> > I was surprised, too.  What I do know is that I observed this 10-15% 
> > slowdown consistently, on that particular revision, so it cannot be 
> > accidental.  As you see on the graphs, I tested about hundred different 
> > revisions, each of them ten times.
>
> I have no explanation for that -- but if you add the "!" back, you 
> disable the Emacs cache completely.  Try it, and load a large image with
>
> emacs -Q some-megapixel-image.jpg
>
> and Emacs will become unusable, because it'll re-decode the image for 
> each update.

I have no explanation either, and I did not write that the solution was to 
add the "!" back ;-)

What is also odd is that the benchmark does not load any image: it loads 
the "xdisp.c" file and scrolls down until EOF.