Performance issues with long lines in shell mode

Performance issues with long lines in shell mode

[David Karr]

I'm using Cygwin Emacs v26.3.

I use shell buffers in Emacs very often. Some of the command lines I run
end up producing output with a large number of lines, and sometimes with
very long lines. If the output is a large number of lines, it doesn't
present any particular problem.  However, if it ends up producing very long
lines (equivalent of a hundred lines or more), I find that it gets very
slow. I generally don't even keep my cursor at the end of the output, so
it's adding output that I'm not even seeing. However, I can still tell that
it's running slowly. If I occasionally jump to the end of the output, I see
it sending characters in bursts, but much less than a line at a time.

If I know that what I'm about to run will create long lines, I generally
try to remember to pipe it directly to a file and then open that file. That
goes much faster than letting it output to the shell.

Is there some mitigation I can configure that will help with this?

Re: Performance issues with long lines in shell mode

[Eli Zaretskii]

> From: David Karr <davidmichaelkarr@gmail.com>
> Date: Thu, 7 May 2020 09:40:55 -0700
> 
> If I know that what I'm about to run will create long lines, I generally
> try to remember to pipe it directly to a file and then open that file. That
> goes much faster than letting it output to the shell.
> 
> Is there some mitigation I can configure that will help with this?

Try "M-x toggle-truncate-lines RET".  It doesn't always help, but it's
worth trying.

Re: Performance issues with long lines in shell mode

[Andreas Röhler]

On 07.05.20 18:40, David Karr wrote:
> I'm using Cygwin Emacs v26.3.
>
> I use shell buffers in Emacs very often. Some of the command lines I run
> end up producing output with a large number of lines, and sometimes with
> very long lines. If the output is a large number of lines, it doesn't
> present any particular problem.  However, if it ends up producing very long
> lines (equivalent of a hundred lines or more), I find that it gets very
> slow. I generally don't even keep my cursor at the end of the output, so
> it's adding output that I'm not even seeing. However, I can still tell that
> it's running slowly. If I occasionally jump to the end of the output, I see
> it sending characters in bursts, but much less than a line at a time.
>
> If I know that what I'm about to run will create long lines, I generally
> try to remember to pipe it directly to a file and then open that file. That
> goes much faster than letting it output to the shell.
>
> Is there some mitigation I can configure that will help with this?

AFAIU there might be a solution avoiding interactive use of shell, 
sending stuff to some shell-process buffer instead while not displaying 
the latter.

Considering the display-engine possibly causing the slowness.

May you provide  an example-case  suitable for benchmarking?

Best,

Andreas