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

Christoph Lameter
2005-05-16T19:35:30Z

On Mon, 16 May 2005, john stultz wrote:

> In pseudo code, all you would need to do is something like:
>
> arch_update_vsyscall_gtod(wall_time, offset_base, timesource, ntp_adj):
>
> fastcall_data.wall = wall_time
> fastcall_data.base = offset_base
> fastcall_data.ts = timesource
> fastcall_data.ntpadj = ntp_adj

Ahh. Thanks.

> > Clock jitter can affect multiple clock sources that may fluctuate
> > in a minor way due to a variety of influences. Jitter compensation may
> > help in these situations.
>
> Forgive me as I'm just not aware of these, and am thus hesitant to
> change the core code for two known cases that can be cleanly dealt with
> in the timesource driver code.

I am happy to leave the situation as is since it does not affect SGI.
We have a memory mapped timer that does not need this jitter compensation.

Other IA64 vendors will see that their timer performance drops
significantly after the new timer subsystem is in. IBM no longer
has IA64 systems that rely on ITC?