Re: Incorrect CLOCK_TICK_RATE in 2.6 kernel

[George Anzinger]

john stultz wrote:
> On Wed, 2005-08-24 at 17:24 -0700, George Anzinger wrote:
>
> > CLOCK_TICK_RATE	is used by the kernel to compute LATCH, TICK_NSEC and 
> > tick_nsec.  This latter is used to update xtime each tick.  TICK_NSEC is 
> > then used to compute (at compile time) the conversion constants needed 
> > to convert to/from jiffies from/to timespec and timeval (and others).
> >
> > The problem is that, if the timer being used is either Cyclone or HPET, 
> > the wrong CLOCK_TICK_RATE is used.
>
>
> Err, the Cyclone does not generate interrupts. So this issue does not
> affect those systems.
>
> As for the HPET, it sets its own interrupt frequency based off of
> KERNEL_TICK_USEC (which you're right, isn't quite what is used in the
> jiffies conversions).  Would it be easier to just adjust that value to
> use ACTHZ or CLOCK_TICK_RATE?

If you want to take that approach you would want the HPET to interrupt 
every TICK_NSEC nanoseconds, that being what xtime is pushed by each tick.

--
George Anzinger   george@xxxxxxxxxx
HRT (High-res-timers):  http://sourceforge.net/projects/high-res-timers/
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/