Re: Incorrect CLOCK_TICK_RATE in 2.6 kernel

[George Anzinger <george@mvista.com>]

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/