bug#66288: 29.1; Performance regression using pipe for subprocess

[Chris Hanson]

On 10/3/23 13:24, Eli Zaretskii wrote:
> None of the above is needed anymore, as they don't seem to be
> relevant.
>
> The Lisp profiler seems to point to redisplay as the culprit:
> redisplay_internal seems to take most of the time in these recipes.

Detailed examination of the Lisp profiler output shows that most of the 
redisplay  time is spent in fontification. I don't know if that helps.

> > I think at this point, since none of the initial guesses seems to be
> > correct, running your recipe under perf and looking at the differences
> > would be our best bet?  That, and bisecting the Git repository.
>
> This would still be useful.  I'm trying to see what has changed
> between Emacs 28 and Emacs 29 in this regard that causes such a
> massive slowdown, but bisecting and/or perf data could provide
> valuable inputs to guide the search.

I've not used the perf-tools before. There seem to be quite a few of 
them, and it's not obvious to me what you want me to run. Any suggestions?