Re: time patches by Roman Zippel

[Roman Zippel <zippel@linux-m68k.org>]

Hi,

On Wed, 15 Feb 2006, Ulrich Windl wrote:

> > > Assuming 1024Hz interrupt frequency:
> > > (1µs * 1000) / 1024 == 0ns; 0 * 1024 == 0µs, not 1µs
> > > (2µs * 1000) / 1024 == 1ns; 1 * 1024 == 1.024µs, not 2µs
> > 
> > Ok, I didn't put much effort into optimizing it for uncommon HZ values. 
> > Why is it so important? It's currently unused on any Linux machine 
> > synchronized via NTP.
> 
> Roman,
> 
> how do you know? When using "disable kernel", NTP relies on adjtime() to adjust 
> the time. Some people even prefer that, because the algorithms do floating point 
> math in user space instead of fixed-point maths in kernel space.

This still requires they choose an uncommon HZ value, which is not really 
likely. Anyway, it's not really difficult to add the remainder to 
time_adj_curr. Since the adjtime() has only a usec resolution and this 
rounding error is only 1 usec, I didn't consider it to be that important.

bye, Roman