Hello.
A weird problem here, and I'm looking for help in
an attempt to solve it.
Ever since KMS went into kernel and I tried turning
it on, the scrolling speed on the resulting "text"
console (with kms it works in one of graphics modes
hence "text" in quotes) become really _awful_.
For example, running `dmesg' (which has ~2000 lines)
on the console takes about 2.5 _minutes_ (!) to
complete, -- which means the speed is about 10 lines
per second. On an old notebook I have, with some also
nvidia card, the same operation completes in about
0.8 sec.
The lines goes up in a slow motion, I can watch every
new line appearing and scrolling.
It was this way for a long time, and I almost gave up --
in X everything works ok, and in order to speed up
booting again I just added "quiet" option to the kernel
command line, to avoid scrolling of kernel messages.
But yesterday I noticed something else entirely, which
make me hope the problem actually _can_ be solved.
The thing is: that same scrolling becomes much faster
when I "do something" else while it scrolls up. First
I noticed this when I wanted to switch to another vt
while it were scrolling -- I held down Ctrl key on my
keyboard, and out of the sudden the scroll speed up
dramatically.
It turned out I can speed the thing to about 10 times
by generating some load: hit and hold a key on the
keyboard (generates interrupts?), run kernel compile
in the background (generates disk interrupts?), move
mouse...
While doing "something", the same scrolling completes
in about 8 seconds instead of 2m30s. Dramatic improvement.
Now, when I hold a key or move mouse, the scrolling
is "jumpy" - sometimes it slows down back to original
"slow" form for a bit, and sometimes it jumps a few
lines in one go.
I tried to disable cpufreq (selecting "performance"
governor) - this changes exactly nothing.
Next someone suggested the "perf" tool. And this one
is even more interesting: while `perf top' is running
(on another console or ...
