Re: 2.6 vs 2.4, ssh terminal slowdown

[Con Kolivas]

On Wed, 8 Feb 2006 01:55 pm, Grant Coady wrote:
> On Wed, 8 Feb 2006 13:35:18 +1100, Con Kolivas <kernel@xxxxxxxxxxx> wrote:
> >On Wed, 8 Feb 2006 01:11 pm, Grant Coady wrote:
> >> Hi there,
> >>
> >> grant@deltree:~$ uname -r
> >> 2.6.15.3a
> >> grant@deltree:~$ time grep -v 192\.168\. /var/log/apache/access_log| cut
> >> -c-95 ...
> >> 2006-02-08 12:38:13 +1100: bugsplatter.mine.nu 193.196.182.215 "GET
> >> /test/linux-2.6/tosh/ HTTP/
> >>
> >> real    0m8.537s
> >> user    0m0.970s
> >> sys     0m1.100s
> >>
> >> --> reboot to 2.4.32-hf32.2
> >>
> >> grant@deltree:~$ uname -r
> >> 2.4.32-hf32.2
> >> grant@deltree:~$ time grep -v 192\.168\. /var/log/apache/access_log| cut
> >> -c-95 ...
> >> 2006-02-08 12:38:13 +1100: bugsplatter.mine.nu 193.196.182.215 "GET
> >> /test/linux-2.6/tosh/ HTTP/
> >>
> >> real    0m2.271s
> >> user    0m0.730s
> >> sys     0m0.540s
> >>
> >> Still a 4:1 slowdown, machine .config and dmesg info:
> >>   http://bugsplatter.mine.nu/test/boxen/deltree/
> >
> >What happens if you add "| cat" on the end of your command?
>
> It gets faster with 2.4.32-hf32.2 by a little bit (I forgot to copy)
>
> reboot to 2.6.15.3a, without...
>
> real    0m8.737s
> user    0m1.030s
> sys     0m1.200s
>
> with...  oh shit / surprise!!
>
> real    0m1.861s
> user    0m0.560s
> sys     0m0.370s
>
> What is that telling me / you / us?

Heh.

This is the terminal's fault. xterm et al use an algorithm to determine how 
fast your machine is and decide whether to jump scroll or smooth scroll. This 
algorithm is basically broken with the 2.6 scheduler and it decides to mostly 
smooth scroll.

Cheers,
Con
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