bug#59641: term is very slow

[Eli Zaretskii]

> Date: Mon, 28 Nov 2022 02:00:29 +0600
> From:  Akib Azmain Turja via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> 
> Term mode is very slow.  On my computer, Coterm is 2-3x faster than
> term, and my own terminal emulator, Eat, is 4-5x faster.
> 
> I tried to profile Term.  Steps:
> 
> 1. emacs -Q (+ -nw, environment variable DISPLAY was unset)
> 2. M-x profiler-start RET cpu+mem RET
> 3. M-x term
> 4. Run the following stupid command:
>    timeout 1 bash -c 'i=0 ; while true ; do echo $i ; i=$((i+1)) ; done'
>    Note I also run emacs -nw in before this command.
> 5. Wait for finishing.
> 6. M-x profiler-stop
> 7. M-x profiler-report
> 
> Here are the reports (attached), but don't seem to be human readable:

Copy them from the display shown by profiler-report, after you expand it
completely.

And the "cpu" profile is enough; the "mem" one doesn't add anything useful.