Re: 2nd proc not seen

[Mikael Pettersson]

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
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