On Tue, 2007-04-24 at 22:13 +0200, Bert Wesarg wrote:
>
> Li-Ta Lo wrote:
> > On Tue, 2007-04-24 at 21:49 +0200, Bert Wesarg wrote:
> >> Hi,
> >>
> >> Li-Ta Lo wrote:
> >>> Hi,
> >>>
> >>> My dual Xeon desktop with SMT (1 core, 2 threads) is reported by the
> >>> kernel in a very strange way. The kernel thinks the first physical
> >>> processor as socket 0 but the second physical processor as socket
> >>> 3. There is no socket 1 or 2 either reported by /proc/cpuinfo or
> >>> /sys. This breaks the for loop code counting max sockets in
> >>> load_cache() as it assumes the sockets # are consecutive (and
> >>> allocating memory for non-existence sockets). As a consequence,
> >>> the total number of socket is incorrect neither.
> >>>
> >>> I don't know if we are going to see nonconsecutive processor
> >>> id, core id or thread id reported by kernel in reality.
> >>>
> >>> I attached the /proc/cpuinfo and /sys for your reference.
> >> Hmm, but the /proc/cpuinfo shows for the physical id 0 for first two cpus
> >> and 3 for the last two. I don't know why.
> >>
> >> processor : 0
> >> physical id : 0
> >> processor : 1
> >> physical id : 0
> >> processor : 2
> >> physical id : 3
> >> processor : 3
> >> physical id : 3
> >>
> >
> > This is exactly what I am talking about. Process 2 and 3 are considered
> > on physical id (socket?) 3. In this case, the max_socket !=
> > number_of_sockets.
> Yeah, but nobody talked ever about number of sockets, only max number of
> socket id, and this is totally correct here. At my first look over the
> code, I thought the whole time: "why do they only return max_core, and not
> max_core + 1", but here you have the reason.
>
Then we got some "unpopulated" sockets. This confuses the rest of the
code a lot.
> >
> > Oh, I think this may actually be how it is reported by the BIOS via ACPI
> > tables.
> Just curious, what kernel version run on this machine? Maybe they have
> fixed it.
>
[ollie_at_exponential ~]$ uname -a
Linux exponential.lanl.gov 2.6.19 #1 SMP PREEMPT Tue Dec 5 13:15:01 MST
2006 i686 i686 i386 GNU/Linux
This one should be reasonably new.
This is what kernel found from ACPI table.
ACPI: LAPIC (acpi_id[0x01] lapic_id[0x00] enabled)
Processor #0 15:2 APIC version 20
ACPI: LAPIC (acpi_id[0x02] lapic_id[0x06] enabled)
Processor #6 15:2 APIC version 20
ACPI: LAPIC (acpi_id[0x03] lapic_id[0x01] enabled)
Processor #1 15:2 APIC version 20
ACPI: LAPIC (acpi_id[0x04] lapic_id[0x07] enabled)
Processor #7 15:2 APIC version 20
Ollie
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