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DateTue, 4 Oct 2005 07:51:11 +0200
FromIngo Molnar <>
SubjectRe: [PATCH] ktimers subsystem 2.6.14-rc2-kt5
* George Anzinger <george@mvista.com> wrote:

> > yeah, and that's an assumption that simplifies things on SMP 
> > significantly. PIT on SMP systems for HRT is so gross that it's not 
> > funny. If anyone wants to revive that notion, please do a separate 
> > patch and make the case convincing enough ...
>
> Lets not talk about PIT, but, a lot of SMP platforms do NOT have per 
> cpu timers.  For those, it would seem having per cpu lists to handle 
> the timer is not really reasonable.

frankly, such systems are rare, and are an afterthought at most. Think 
about it: 8 CPUs and only one hres timer source? It cannot work nor 
scale well.

i agree that they might eventually be handled (although i think we 
shouldnt bother, all sane SMP designs have per-CPU timers), but we 
definite wont design for them. What such an architecture has to do is to 
provide the proper do_hr_timer_int() and arch_hrtimer_reprogram() 
semantics, via locking around that timer source (naturally), and via 
cross-CPU calls - as if they were per-CPU timers.

	Ingo
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