Re: IA64 implementation of timesource for new time of day subsystem

john stultz
2005-05-16T21:40:59Z

On Mon, 2005-05-16 at 13:58 -0700, David Mosberger wrote:
> >>>>> On Mon, 16 May 2005 13:53:44 -0700, john stultz <johnstul@us.ibm.com> said:
> John> You've only pointed out two timesources that could want this
> John> (ITC and TSC), so I think its reasonable to do your jitter
> John> handling in the timesource driver. If there are other arches
> John> that have non hardware synced per-cpu counters, then it would
> John> be something to consider.
>
> I think Christopher's point is that _all_ time-sources which require
> software syncing will need this since it is not possible to sync
> perfectly, even if there is no drift.

Yes, but to my knowledge it is only the ITC that does software syncing.
The TSC could use it as well, but doesn't. Other then that I haven't
heard of any other timesource that would use such functionality.

Since its possible to do jitter compensation within the itc timesource
driver (and within the fastcall code to preserve the existing
performance), would it be reasonable to deffer making the jitter
compensation code generic until another timesource needs it? It should
be a fairly simple change.

Or is this just something I'm being hard-headed about?

thanks
-john