Messages in this thread | | | Date | Mon, 29 Sep 2003 11:13:21 +0200 | From | Mikael Pettersson <> | Subject | Re: 2nd proc not seen |
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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[].
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