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

[Chris Hanson]

When using "xscheme.el" to start and interact with MIT/GNU Scheme in a
subprocess, the performance significantly degraded in Emacs 29.1.  It
worked well in older releases.

Here is a recipe:

    emacs -Q
    M-x load-library RET xscheme RET
    M-x run-scheme RET

    and see how slowly the process output is printed as Scheme starts.
    Compare this to Emacs 28.2 or earlier.

I've played around quite a bit to figure out what's going on, and found
that changing xscheme-start-process so that start-process used a pty
instead of a pipe eliminated the performance regression.  That isn't
really a solution since there's some complicated interrupt stuff going
on that crashes the subprocess when a pty is used.  I'm trying to track
that down and fix it but have not succeeded so far.


In GNU Emacs 29.1 (build 2, x86_64-pc-linux-gnu, X toolkit, cairo
 version 1.16.0, Xaw3d scroll bars) of 2023-08-03 built on kleph
Windowing system distributor 'The X.Org Foundation', version 11.0.12101004
System Description: Ubuntu 22.04.3 LTS

Configured using:
 'configure --with-x-toolkit=athena --with-tree-sitter
 --with-native-compilation'

Configured features:
CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GSETTINGS HARFBUZZ JPEG
LIBSELINUX LIBXML2 MODULES NATIVE_COMP NOTIFY INOTIFY PDUMPER PNG RSVG
SECCOMP SOUND THREADS TIFF TOOLKIT_SCROLL_BARS TREE_SITTER X11 XAW3D
XDBE XIM XINPUT2 XPM LUCID ZLIB

Important settings:
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix

Major mode: Scheme Interaction

Minor modes in effect:
  diff-auto-refine-mode: t
  windmove-mode: t
  which-function-mode: t
  which-key-mode: t
  savehist-mode: t
  global-git-commit-mode: t
  shell-dirtrack-mode: t
  server-mode: t
  global-edit-server-edit-mode: t
  desktop-save-mode: t
  global-auto-revert-mode: t
  override-global-mode: t
  global-eldoc-mode: t
  show-paren-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  line-number-mode: t
  transient-mark-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t

Load-path shadows:
/home/cph/.emacs.d/elpa/transient-20230919.2146/transient hides 
/usr/local/share/emacs/29.1/lisp/transient
/home/cph/.emacs.d/elpa/use-package-20230426.2324/use-package hides 
/usr/local/share/emacs/29.1/lisp/use-package/use-package
/home/cph/.emacs.d/elpa/use-package-20230426.2324/use-package-jump hides 
/usr/local/share/emacs/29.1/lisp/use-package/use-package-jump
/home/cph/.emacs.d/elpa/bind-key-20230203.2004/bind-key hides 
/usr/local/share/emacs/29.1/lisp/use-package/bind-key
/home/cph/.emacs.d/elpa/use-package-20230426.2324/use-package-bind-key 
hides /usr/local/share/emacs/29.1/lisp/use-package/use-package-bind-key
/home/cph/.emacs.d/elpa/use-package-20230426.2324/use-package-delight 
hides /usr/local/share/emacs/29.1/lisp/use-package/use-package-delight
/home/cph/.emacs.d/elpa/use-package-20230426.2324/use-package-lint hides 
/usr/local/share/emacs/29.1/lisp/use-package/use-package-lint
/home/cph/.emacs.d/elpa/use-package-20230426.2324/use-package-core hides 
/usr/local/share/emacs/29.1/lisp/use-package/use-package-core
/home/cph/.emacs.d/elpa/use-package-20230426.2324/use-package-diminish 
hides /usr/local/share/emacs/29.1/lisp/use-package/use-package-diminish
/home/cph/.emacs.d/elpa/use-package-20230426.2324/use-package-ensure 
hides /usr/local/share/emacs/29.1/lisp/use-package/use-package-ensure
/home/cph/elisp/xscheme hides 
/usr/local/share/emacs/29.1/lisp/progmodes/xscheme
/home/cph/.emacs.d/elpa/flim-20230808.1153/sasl hides 
/usr/local/share/emacs/29.1/lisp/net/sasl
/home/cph/.emacs.d/elpa/seq-2.24/seq hides 
/usr/local/share/emacs/29.1/lisp/emacs-lisp/seq

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threads dbusbind inotify dynamic-setting system-font-setting
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Memory information:
((conses 16 1000671 332582)
 (symbols 48 42644 63)
 (strings 32 178355 25408)
 (string-bytes 1 6621053)
 (vectors 16 113786)
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