Bug#697727: xserver-xorg-video-radeon: [radeon] Scrolling in xterm slow with KMS

Tilo Schwarz tilo at tilo-schwarz.de
Thu Jan 10 03:33:23 PST 2013

On Thu, 10 Jan 2013 10:34:07 +0100, Michel Dänzer <daenzer at debian.org>  

> On Don, 2013-01-10 at 10:14 +0100, Tilo Schwarz wrote:
>> On Thu, 10 Jan 2013 09:16:37 +0100, Michel Dänzer <daenzer at debian.org>
>> wrote:
>> > On Mit, 2013-01-09 at 20:01 +0100, Tilo Schwarz wrote:
>> >>
>> >> Indeed, using
>> >>
>> >> % grep ColorTiling /etc/X11/xorg.conf
>> >>          Option          "ColorTiling"   "off"
>> >>
>> >> the scrolling is twice as fast as without this option (from 12sec  
>> down
>> >> to
>> >> 6sec). That is still almost three times slower than without KMS, but
>> >> already much more usable!
>> >
>> > The better solution would be to configure your terminals to use
>> > fontconfig/Xft for text rendering.
>> Do you have a link to "the correct debian way" to enable fontconfig/Xft
>> for text rendering? (Me being no X11 expert ...)
> It's app/toolkit specific. E.g. with xterm you can enable it with -fa
> and related options.
>> Is it a fontcontig and Xft, or is it a either fontcontig or Xft?
> It's mainly about Xft. Most users of that also use fontconfig for
> selecting the fonts to use, but that's not required.
> Most apps/toolkits have used the modern text rendering infrastructure by
> default for a long time, but a lot of terminal emulators are still
> holding out for some reason.

Thanks a lot for your help! It lead me to a nice workaround (even if the  
original question KMS=0 vs. KMS=1 is not really solved by this).

The only thing I did (after reading about Xft and fontconfig) was to  
install rxvt-unicode, which has xft support.

Running "time seq 100000" with various terminal/font combinations gives:

xterm -fn 9x15:
real    0m50.001s
user    0m0.180s
sys     0m0.428s

xterm -fa 9x15:
real    0m7.785s
user    0m0.116s
sys     0m0.180s

real    0m11.707s
user    0m0.140s
sys     0m0.252s

real	0m0.994s
user	0m0.176s
sys	0m0.308s

So for some reason urxvt seems to use a font path, which is as fast as the  
speed having lenny installed. The Xresources for this test were:

% cat .Xresources
xterm*background: black
xterm*charClass: 33:48,37:48,45-47:48,38:48
xterm*font: 9x15
xterm*foreground: white
xterm*saveLines: 1024
xterm*scrollBar: false
xterm*visualBell: true
xterm*visualBellDelay: 100

rxvt*background: black
rxvt*charClass: 33:48,37:48,45-47:48,38:48
rxvt*font: 9x15
rxvt*foreground: white
rxvt*saveLines: 1024
rxvt*scrollBar: false
rxvt*visualBell: true
rxvt*visualBellDelay: 100

urxvt*background: black
urxvt*charClass: 33:48,37:48,45-47:48,38:48
urxvt*font: 9x15
urxvt*foreground: white
urxvt*saveLines: 1024
urxvt*scrollBar: false
urxvt*visualBell: true
urxvt*visualBellDelay: 100

Thanks again!


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