Q: sched_clock() vs. clocksource, how to implement correctly

[Daniel Walker]

On Fri, 2010-04-23 at 18:29 +0200, Martin Schwidefsky wrote:
> > Questions:
> > 
> > - Isn't sched_clock() supposed to be extended to 64bit so
> >   that it practically never wraps?
> >   (old implementations use cnt32_to_63())
> 
> Yes, sched_clock() is supposed to return a monotonic timestamp.
>  
> > - What would be the effect on scheduling when sched_clock() wraps?
> 
> It would confuse the process accounting and the scheduling I guess.
> 

Are you sure about this? I'm pretty sure I've seen Ingo say multiple
times that sched_clock can wrap, and can be unstable. For instance
sched_clock is (was?) directly connected to the TSC on x86 ..

If it really can't wrap there must bunches of architectures that would
need to be fixed up.

Daniel