dual Xeon hyperthread system only showing up as 2 cpus

dual Xeon hyperthread system only showing up as 2 cpus

[Chris Friesen]

Hi all,

I've got a system that has two hyperthread-capable Xeons.  If I boot it 
with 2.6.10 it shows up as 4 cpus, but with 2.6.14 it only shows 2 cpus.

The relevent boot logs are:

2.6.10:

DMI 2.3 present.
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
Using ACPI for processor (LAPIC) configuration information
Intel MultiProcessor Specification v1.4
     Virtual Wire compatibility mode.
<snip>
Processors: 4


2.6.14:

DMI 2.3 present.
Intel MultiProcessor Specification v1.4
     Virtual Wire compatibility mode.
OEM ID: INTEL    Product ID: KingsCanyonC APIC at: 0xFEE00000
Processor #0 15:2 APIC version 20
Processor #6 15:2 APIC version 20
<snip>
Processors: 2


The 2.6.14 config file includes:
CONFIG_MPENTIUM4=y
CONFIG_X86_CMPXCHG=y
CONFIG_X86_XADD=y
CONFIG_X86_L1_CACHE_SHIFT=7
CONFIG_RWSEM_XCHGADD_ALGORITHM=y
CONFIG_GENERIC_CALIBRATE_DELAY=y
CONFIG_X86_WP_WORKS_OK=y
CONFIG_X86_INVLPG=y
CONFIG_X86_BSWAP=y
CONFIG_X86_POPAD_OK=y
CONFIG_X86_GOOD_APIC=y
CONFIG_X86_INTEL_USERCOPY=y
CONFIG_X86_USE_PPRO_CHECKSUM=y
# CONFIG_HPET_TIMER is not set
CONFIG_SMP=y
CONFIG_NR_CPUS=4
# CONFIG_SCHED_SMT is not set
CONFIG_PREEMPT_NONE=y
CONFIG_PREEMPT_BKL=y
CONFIG_X86_LOCAL_APIC=y
CONFIG_X86_IO_APIC=y
CONFIG_X86_TSC=y
CONFIG_X86_MCE=y
CONFIG_X86_MCE_NONFATAL=y
CONFIG_X86_MCE_P4THERMAL=y
CONFIG_MICROCODE=y
CONFIG_X86_MSR=y
CONFIG_X86_CPUID=y


Anyone have any ideas?

Chris

Re: dual Xeon hyperthread system only showing up as 2 cpus

[Robert Hancock]

Chris Friesen wrote:
> 
> Hi all,
> 
> I've got a system that has two hyperthread-capable Xeons.  If I boot it 
> with 2.6.10 it shows up as 4 cpus, but with 2.6.14 it only shows 2 cpus.
> 
> The relevent boot logs are:
> 
> 2.6.10:
> 
> DMI 2.3 present.
> 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
> Using ACPI for processor (LAPIC) configuration information
> Intel MultiProcessor Specification v1.4
>     Virtual Wire compatibility mode.
> <snip>
> Processors: 4
> 
> 
> 2.6.14:
> 
> DMI 2.3 present.
> Intel MultiProcessor Specification v1.4
>     Virtual Wire compatibility mode.
> OEM ID: INTEL    Product ID: KingsCanyonC APIC at: 0xFEE00000
> Processor #0 15:2 APIC version 20
> Processor #6 15:2 APIC version 20
> <snip>
> Processors: 2

You snipped the important part of the log. It's not using ACPI in 2.6.14 
for some reason, which you need for HT to be detected. Either you didn't 
configure it in or it's failed to enable somehow. Please post the entire 
dmesg.

-- 
Robert Hancock      Saskatoon, SK, Canada
To email, remove "nospam" from hancockr@nospamshaw.ca
Home Page: http://www.roberthancock.com/

Re: dual Xeon hyperthread system only showing up as 2 cpus

[Arjan van de Ven]

> 
> Anyone have any ideas?

you don't appear to have ACPI enabled... how does 2.6.22 or 2.6.23-rc
fare?

Re: dual Xeon hyperthread system only showing up as 2 cpus

[Chris Friesen]

Robert Hancock wrote:

> You snipped the important part of the log. It's not using ACPI in 2.6.14 
> for some reason, which you need for HT to be detected. Either you didn't 
> configure it in or it's failed to enable somehow. Please post the entire 
> dmesg.

Wacky.  In 2.6.10 CONFIG_ACPI is disabled, but somehow it has 
CONFIG_ACPI_BOOT=y and CONFIG_ACPI_BLACKLIST_YEAR=0.

In 2.6.14, turning on CONFIG_ACPI allows it to detect 4 cpus.

Thanks for the help.

Chris