slow screen updates on laptop console (i386)

[Rick Macklem]

Alexander Kabaev wrote:
> On Mon, 7 Dec 2015 09:02:35 -0500 (EST)
> Rick Macklem <rmacklem at uoguelph.ca> wrote:
> 
> > Hi,
> > 
> > When running FreeBSD-current on an old i386 laptop, the console
> > screen is intermittently slow to display output. The hesitations
> > can be several seconds.
> > Sometimes it shows up when I'm typing such that it takes seconds
> > for the characters to echo.
> > I think it is the display/output side, since I've seen it happen when
> > doing "more <file>", where the screen is stuck half way through
> > displaying the page for a few seconds.
> > 
> > I don't see any problem when going into the machine remotely and
> > I don't see the problem on the other laptop I have running
> > FreeBSD/amd64.
> > 
> > It has been happening for a while. It occurs on the oldest kernel
> > I have lying around (r287930, Sep. 17, 2015).
> > 
> > I've tried the old "sc" driver and it seems to happen less with it,
> > but it still occurs.
> > 
> > I'll admit I have no idea what drives doing output for the display
> > screen.
> > 
> > Anyone have ideas w.r.t. this?
> > 
> > Thanks in advance, rick
> 
> Hi,
> 
> maybe a stretch, but I would try selecting different eventtimer, if
> available. Say, I had to select HPET on my old i7 920 to make timeouts
> run reliably.
> 
> sysctl kern.eventtimer.timer=HPET
>  
Great guess! Actually this old laptop doesn't have HPET, but switching it
from LAPIC->RTC seems to have fixed the problem.
(I had a hunch it was something timer/interrupt related, but I don't know
 that part of the system.)
--> Just fyi, my other laptop that works fine defaulted to HPET. It looks
    like HPET rates higher than LAPIC.

Thanks a lot, rick

> --
> Alexander Kabaev
>