From: Peter Horton <pdh@colonel-panic.com>
To: Pavel Machek <pavel@suse.cz>
Cc: Andrew Morton <andrewm@uow.edu.au>, Hacksaw <hacksaw@hacksaw.org>,
Tom Eastep <teastep@seattlefirewall.dyndns.org>,
linux-kernel@vger.kernel.org
Subject: Re: [OT] Major Clock Drift
Date: Sun, 11 Feb 2001 12:14:39 +0000 [thread overview]
Message-ID: <20010211121439.A1039@colonel-panic.com> (raw)
In-Reply-To: <Pine.LNX.4.30.0102040908320.877-100000@wookie.seattlefirewall.dyndns.org> <200102041804.f14I4br22433@habitrail.home.fools-errant.com> <3A7EA9B3.3507DC8D@uow.edu.au>, <3A7EA9B3.3507DC8D@uow.edu.au>; <20010210225851.G7877@bug.ucw.cz> <3A8671FF.C390FDCC@uow.edu.au> <20010211120614.E23048@atrey.karlin.mff.cuni.cz>
In-Reply-To: <20010211120614.E23048@atrey.karlin.mff.cuni.cz>; from pavel@suse.cz on Sun, Feb 11, 2001 at 12:06:14PM +0100
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.
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next prev parent reply other threads:[~2001-02-11 12:21 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-02-04 4:32 [OT] Major Clock Drift Josh Myer
2001-02-04 4:42 ` Manfred Bartz
2001-02-04 12:56 ` Michael B. Trausch
2001-02-04 15:18 ` Steve Underwood
2001-02-04 15:31 ` Hacksaw
2001-02-04 23:46 ` Alan Chandler
2001-02-04 17:18 ` Tom Eastep
2001-02-04 18:04 ` Hacksaw
2001-02-04 18:07 ` Tom Eastep
2001-02-05 13:25 ` Andrew Morton
2001-02-10 21:58 ` Pavel Machek
2001-02-11 11:05 ` Andrew Morton
2001-02-11 11:06 ` Pavel Machek
2001-02-11 11:47 ` Andrew Morton
2001-02-11 12:14 ` Peter Horton [this message]
2001-02-11 13:52 ` Chris Wedgwood
2001-02-05 1:18 ` Michael B. Trausch
2001-02-13 3:00 ` george anzinger
2001-02-13 6:51 ` Josh Myer
2001-02-10 21:58 ` [OT] " Pavel Machek
2001-02-11 17:07 ` Alan Cox
2001-02-11 22:29 ` Andrew Morton
2001-02-12 9:48 ` Alan Cox
2001-02-12 10:05 ` Andi Kleen
2001-02-12 10:10 ` Alan Cox
2001-02-12 12:14 ` James Sutherland
2001-02-12 10:32 ` Pavel Machek
2001-02-12 10:36 ` Alan Cox
2001-02-12 11:38 ` Andrew Morton
2001-02-13 7:24 ` Abramo Bagnara
2001-02-10 21:55 ` Pavel Machek
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