font, screen and window speeds

[Toby Kelsey]

FYI,

After I installed xfonts-terminus, I was a bit disappointed by the
continuing slowness of gnome-terminal (it can take several seconds to
page-down in 'less'), so I did some testing with various fonts and
terminals. The simple test was running 'time /bin/ls -FC' in a directory
(ext3 filesystem) containing many files.

> /bin/ls -FC | wc
wc: standard input:5808: Invalid or incomplete multibyte or wide character
wc: standard input:6448: Invalid or incomplete multibyte or wide character
  17702   18361  337455

Aside1: This is actually (arrogantly) single-column 'ls' format
Aside2: Is it 'ls' or 'wc' which doesn't understand LANG=en_GB.UTF-8?

All window tests were run with LINES=67 and COLUMNS=171. I usually run
screen inside gnome-terminal, so that is what I started with.  I used
'script' to record the output for all window tests.

table key:
  'screen1000' means screen with 1000 line history
  'screen0' means screen with a zero line history

    terminal                font         real       user      sys
gnome-terminal+screen1000  default     3m5.512s   0m1.449s  0m0.444s
gnome-terminal+screen1000  fixed-12    2m39.633s  0m1.423s  0m0.497s
gnome-terminal+screen1000  terminus-12 2m36.019s  0m1.485s  0m0.609s
gnome-terminal+screen0     terminus-12 2m39.099s  0m1.441s  0m0.430s
gnome-terminal only        default     0m33.006s  0m1.470s  0m0.432s
gnome-terminal only        terminus-12 0m26.408s  0m1.468s  0m0.447s
gnome-terminal only        terminus-12 0m22.170s  0m1.471s  0m0.554s
gnome-terminal only        terminus-12 0m23.776s  0m1.447s  0m0.459s
gnome-terminal only        fixed-12    0m26.170s  0m1.443s  0m0.504s
gnome-terminal only        fixed-12    0m22.601s  0m1.458s  0m0.439s
xterm only                 fixed-10?   0m17.485s  0m1.460s  0m0.598s
gnome-terminal only        fixed-10?   0m31.969s  0m1.501s  0m0.853s
gnome-terminal only        fixed-11    0m23.655s  0m1.483s  0m0.542s
gnome-terminal only        fixed-9     0m19.811s  0m1.434s  0m0.473s
console, no 'script'       default     0m58.178s  0m1.530s  0m55.741s

xterm note:
 The default xterm font looked like fixed-10, the window was smaller
than the default gnome-terminal. I couldnt be bothered to find the
correct font-description strings to test any other than the default font.

gnome-terminal notes:
 The font was set via Edit > Curent profile.  With gnome terminal,
fixed-10 looked wrong - bold and wider then size 12 fonts - in fact too
wide for the screen (1600x1200).
 fixed-11 was less wide than fixed-10 and was not bold.
 fixed-9 was much smaller, barely readable.

console note:
 The console output was single-column, other output was double-column

Running the test outside 'script' made no noticable change to the times.
There was some timing fluctuations (seen in the repeated entries) due to
other system activities.  Allow for a fuzz factor of several seconds.

Conclusions:
1) Screen is very slow displaying large amounts of data, the font choice
has a relatively small effect if you are using screen.
2) Having a large history (scrollback buffer) is not the problem.
3) Without screen Terminus is approximately as fast as the (ugly) fixed
font and faster than the default for gnome-terminal.
4) xterm seems slightly (20%?) faster than gnome-terminal.
5) The console (virtual terminal) is surprisingly slow.
6) Some font sizes are 'fudged' (fixed-10 and fixed-9).
7) Changing fonts while using vim confuses it completely.

HTH,
Toby