Re: Redisplay slower in Emacs 28 than Emacs 27

[Alan Third]

On Mon, Dec 07, 2020 at 06:49:22PM +0000, Gregory Heytings via Emacs 
development discussions. wrote:
> 
> > > That being said, it seems to me that this slowdown is avoidable.
> > > Lars considers that the minor modification he made should not have
> > > changed anything.
> > 
> > Would it be possible for you to run the benchmarks on the current trunk,
> > with and without that "!"?  Because I just don't understand why
> > disabling the image cache would make Emacs slower.
> > 
> 
> Sure, I'll do that.

Could you also try with this patch:

@@ -2351,7 +2356,7 @@ lookup_image (struct frame *f, Lisp_Object spec, int 
face_id)
 
   /* Look up SPEC in the hash table of the image cache.  */
   hash = sxhash (spec);
-  img = search_image_cache (f, spec, hash, foreground, background, true);
+  img = search_image_cache (f, spec, hash, foreground, background, false);
   if (img && img->load_failed_p)
     {
       free_image (f, img);

It's a definite mistake on my part and may affect the caching of
images, although I can't see any way that it would slow anything down.
-- 
Alan Third