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Subject: Re: time drift and fb comsole activity
From: Brad Douglas <brad@neruo.com>
To: Andrew Morton <morton@nortelnetworks.com>
Cc: ebuddington@wesleyan.edu, linux-kernel@vger.kernel.org
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	<3A9D8BC4.45009947@asiapacificm01.nt.com>
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Date: 28 Feb 2001 16:43:49 -0800
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On 28 Feb 2001 23:37:40 +0000, Andrew Morton wrote:
> Eric Buddington wrote:
> > 
> > I know this has been reported on the list recently, but I think I can
> > provide better detail. I'm running 2.4.2 with atyfb on a K6-2/266
> > running at 250. This system has no history of clock problems.
> > 
> > adjtimex-1.12 --compare gives me "2nd diff" readings of -0.01 in quiescent
> > conditions.
> > 
> > flipping consoles rapidly cboosts this number to -3 or -4.
> > 
> > catting the full documentation to ntpd (seemed appropriate) gives me
> > "2nd diff" numbers a little over 34. If I read the numbers correctly,
> > 47 seconds of CMOS time passed while the system clock only passed 13
> > seconds.
> > 
> > The processor and the CMOS clock were moving at zero velocity relative
> > to each other, and were both in normal Earth gravity.
> 
> The kernel blocks interrupts during console output.  fbdev
> consoles are slow.  Net result: many lost timer interrupts.
> 
> I'm working on it.  Slowly.  Should have something next week.

You may want to check out the linuxconsole project on Sourceforge.  I
believe one of their goals is to remove/minimize the console lock...

Brad Douglas
brad@neruo.com
http://www.linux-fbdev.org


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