On Saturday 30 July 2005 12:10 pm, Christoph Lameter wrote: > On Sat, 30 Jul 2005, Alex Williamson wrote: > > > On Fri, 2005-07-29 at 16:31 -0700, Christoph Lameter wrote: > > > What you are dealing with is a machine that is using ITC as a time bases. > > > That is a special case. > > > > The default time source for ia64 systems is a "special case"? 4 > > socket and smaller boxes typically do not have any other time source. > > It is a special case because we typically use other time sources.
Maybe you==SGI typically use other time sources, but most other ia64 boxes have synchronized ITCs. There's no reason such machines should have to use the slower and lower precision HPET. > If it is really synchronized then you can run with "nojitter" without any > issue. Then you wont have to deal with the cmpxchg and everything is fine. > But I suspect that the ITC are NOT truly synchronized (it has an > "offset" that may be nonzero right?) otherwise you would have used nojitter. And why should everyday users have to be concerned with "nojitter"? > Extra timer hardware is necessary to fix the ITC deficiency. You are at > the source of the problem. Fix the damn hardware to provide a standardized > synchronized clock or provide a truly synchronized ITC. The "ITC deficiency" is a platform design issue. Most small SMP platforms *do* synchronize the clocks of all processors. Obviously that's difficult on large boxes, and then you may need extra timers in the platform. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
