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SubjectRe: Incorrect CLOCK_TICK_RATE in 2.6 kernel
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@mvista.com
HRT (High-res-timers): http://sourceforge.net/projects/high-res-timers/
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