Re: 2nd proc not seen

Mikael Pettersson
2003-09-29T09:13:34Z

J.A. Magallon writes:
>
> On 09.29, Frank Cusack wrote:
> > On Thu, Sep 04, 2003 at 09:14:37AM -0700, Frank Cusack wrote:
> > > On Thu, Sep 04, 2003 at 02:11:13AM -0700, Frank Cusack wrote:
> > > > I think I've seen some recent talk about this problem. I have an HPAQ
> > > > xw6000 w/ 2xP4 CPUs. A RH kernel finds both CPUs (4 if I enable HT). A
> > > > kernel.org kernel only finds 1 (2 if I enable HT).
> >
> > This turned out to be a CPU numbering issue. The HPAQ machine numbers
> > the cpus #0 and #6. I had NR_CPUS set to 2. That only works if the CPUs
> > are physically numbered 0 and 1.
> >
> > So NR_CPUS is a little misleading. I could suggest a Config.help change
> > if you like.
> >
>
> This is a little weird. This forces you to have all the SMP structures sized
> 8 just to use 2 members.
>
> Was not there a physical-logical map ? Or that was in -aa kernel and 2.6 ?

Problem #1 is that physical CPU numbering isn't dense. This is not a bug.
Problem #2 is that the kernel's internal dense-logical-to-sparse-physical
numbering was deleted in 2.5.23 or thereabouts.

Hence NR_CPUS is basically impossible to use reliably in 2.6 unless we
reintroduce cpu_logical_map[].

/Mikael