Re: [PATCH] i386: Selectable Frequency of the Timer Interrupt

Vojtech Pavlik
2005-07-13T22:09:21Z

On Wed, Jul 13, 2005 at 10:24:10AM -0700, David Lang wrote:

> >How serious is the 1/HZ = sane problem, and more to the point how many
> >programs get the HZ value with a system call as opposed to including a
> >header or building it in? I know some of my older programs use header
> >files, that was part of the planning for the future even before 2.5
> >started. At the time I didn't expect to have to use the system call.
>
> in binary 1/100 or 1/1000 are not sane values to start with so I don't
> think that that this is likly to be that critical (remembering that the
> kernel doesn't do floating point math)

No, but 1/1000Hz = 1000000ns, while 1/864Hz = 1157407.407ns. If you have
a counter that counts the ticks in nanoseconds (xtime ...), the first
will be exact, the second will be accumulating an error.

It's a tradeoff.

--
Vojtech Pavlik
SuSE Labs, SuSE CR