lkml.org 
[lkml]   [2001]   [Feb]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [OT] Major Clock Drift
From
On Sun, Feb 11, 2001 at 12:06:14PM +0100, Pavel Machek wrote:
>
> > > > > >I've discovered that heavy use of vesafb can be a major source of clock
> > > > > >drift on my system, especially if I don't specify "ypan" or "ywrap". On my
> > > > >
> > > > > This is extremely interesting. What version of ntp are you using?
> > > >
> > > > Is vesafb one of the drivers which blocks interrupts for (many) tens
> > > > of milliseconds?
> > >
> > > Vesafb is happy to block interrupts for half a second.
> >
> > And has this been observed to cause clock drift?
>
> YEs. I've seen time running 3 times slower. Just do cat /etc/termcap
> with loaded PCI bus. Yesterday I lost 20 minutes during 2 hours -- I
> have been using USB (load PCI) and framebuffer.
> Pavel

Is it not possible to save/check TSC in timer interrupt to correct for
dropped interrupts ? (obviously only on machines that have a TSC ...)

P.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 13:13    [W:0.051 / U:24.068 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site