bug#51734: 29.0.50; got slow

[Eli Zaretskii <eliz@gnu.org>]

> Cc: 51734@debbugs.gnu.org
> Date: Wed, 10 Nov 2021 20:38:32 +0800
> From:  Po Lu via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> 
> > For instance, the cursor moves not smoothly while repeating `C-n's,
> > `C-s' takes a couple of seconds for the text searched to appear, etc.
> > It should have happened after my build on Thu 4 Nov 22:00 UTC
> > through the previous build on Mon 8 Nov 22:00 UTC.
> >
> > Thanks.
> 
> See below.
> 
> >  'configure 'CFLAGS=-O0 -g3' --verbose --with-x-toolkit=gtk3
> >  --with-imagemagick'
> 
> Did you notice the problem in the Emacs in which you ran
> `report-emacs-bug'?  `-O0 -g3' will normally slow down Emacs
> considerably, as it disables all compiler optimizations, and is used as
> a debugging aid.

Building Emacs with -O0 should never make Emacs so slow as described
by the OP.  Disabling optimizations generally makes Emacs about 2.5 to
3 times slower, but that's still a far cry from response time of a
second or two to C-s.

I use unoptimized builds of the development version all the time,
because optimized builds are very hard to debug.