[parisc-linux] Generic light-weight syscall.

Grant Grundler grundler@parisc-linux.org
Tue, 29 Jul 2003 12:51:30 -0600

On Mon, Jul 28, 2003 at 06:45:51PM +0100, Matthew Wilcox wrote:
> > It might be too costly to do the sync'ing all the time, and too costly
> > for a fast gettimeofday to do a sync at the polling point.

If they all use the same clock source they won't drift.

> > gettimeofday. Do we even have such a fast clock on PA? What is the
> > fastest clock across the most boxes?


> You know, you don't even need kernel help for this.  According to page
> 2-5 of the Kane book, the Interval Timer is accessible by non-privileged
> instructions.

One needs kernel help in determining the difference between CPUs
and handling CR16 rollover (mostly a problem for 32-bit machines).
But then user space can read CR16 and "normalize" the time.