Re: gettimeofday() moving backwards

[Dominik Brodowski <linux-JhLEnvuH02M@public.gmane.org>]

On Wed, Dec 18, 2002 at 01:23:57PM -0800, Grover, Andrew wrote:
> > From: Paul Richards [mailto:p.a.richards-Y3tGgqFSo3OFxr2TtlUqVg@public.gmane.org] 
> > I am using linux kernel v2.4.20 with ACPI patch dated 2002-12-05.
> > 
> > I have noticed that if my processor changes state (800Mhz up 
> > to 1200Mhz say)
> > then gettimeofday() behaves weirdly.  It runs smoothly but 
> > every now and again
> > (on the order of 10 times a second) it makes a correction.  
> > If I have gone from
> > 800Mhz to 1200Mhz then the correction is backwards, otherwise 
> > it makes a forward
> > jump..
> 
> Hmm, can you mention this on the cpufreq mailing list?
> cpufreq-1walMZg8u8rXmaaqVzeoHQ@public.gmane.org .

In kernel 2.5.5x, gettimeofday() should work fine: ACPI uses the cpufreq
infrastructure, which adds -among other things- a hunk in
arch/i386/timer/tsc.c which updates some values on frequency transitions.
(see http://www.brodo.de/cpufreq/ for details on cpufreq).

As cpufreq isn't included in 2.4. kernels, and likely never will, the 2.4.
gettimeofday() call does cause strange results in 2.4.

	Dominik




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