Re: 26.2; Strange slowness in some Info nodes

[Eli Zaretskii]

> Date: Fri, 2 Aug 2019 20:23:06 +0000 (GMT)
> From: ndame <emacsuser@freemail.hu>
> 
> Though I don't really get why repeated scrolling down is
> slow. I'd think the first one is slow when emacs finds the font
> for the character and then subsequent scroll downs should be
> quick, because then the font for the character is known. 

It is known, but that knowledge can be forgotten.

> It would be strange if the cached information were purged from
> memory right after it was found and emacs had to find the font
> again for the next scroll down.

It is purged during GC.  At the GC level, there's no information
available that could tell Emacs not to purge a font (the "right after"
part is perhaps evident to a human, but not to a program).  The basic
problem with this situation is that some very large fonts cause very
frequent GC, which evicts those large fonts, which then cause a lot of
consing when they are again loaded, which again causes GC soon, etc.