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I am running on a Dual-Proc Server (2.4 GHz P4 Xeon(s)) and when I run the following command 'cat /proc/cpuinfo' it lists my processors on the command line. My question ...
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  1. #1
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    CPUINFO


    I am running on a Dual-Proc Server (2.4 GHz P4 Xeon(s)) and when I run the following command 'cat /proc/cpuinfo' it lists my processors on the command line. My question is, when I have two, why would it list four....does a Linux host see a hyper-threaded processor as two separate? I just find it a little odd that Processor 0 and 1 have the same physical ID of 0 and Processor 2 and 3 have the same physical ID of 3. Anybody else have an explanation to this?
    [root@holley mnt]# cat /proc/cpuinfo
    processor : 0
    vendor_id : GenuineIntel
    cpu family : 15
    model : 2
    model name : Intel(R) Xeon(TM) CPU 2.40GHz
    stepping : 9
    cpu MHz : 2400.627
    cache size : 512 KB
    physical id : 0
    siblings : 2
    fdiv_bug : no
    hlt_bug : no
    f00f_bug : no
    coma_bug : no
    fpu : yes
    fpu_exception : yes
    cpuid level : 2
    wp : yes
    flags : fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe cid xtpr
    bogomips : 4734.97

    processor : 1
    vendor_id : GenuineIntel
    cpu family : 15
    model : 2
    model name : Intel(R) Xeon(TM) CPU 2.40GHz
    stepping : 9
    cpu MHz : 2400.627
    cache size : 512 KB
    physical id : 0
    siblings : 2
    fdiv_bug : no
    hlt_bug : no
    f00f_bug : no
    coma_bug : no
    fpu : yes
    fpu_exception : yes
    cpuid level : 2
    wp : yes
    flags : fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe cid xtpr
    bogomips : 4784.12

    processor : 2
    vendor_id : GenuineIntel
    cpu family : 15
    model : 2
    model name : Intel(R) Xeon(TM) CPU 2.40GHz
    stepping : 9
    cpu MHz : 2400.627
    cache size : 512 KB
    physical id : 3
    siblings : 2
    fdiv_bug : no
    hlt_bug : no
    f00f_bug : no
    coma_bug : no
    fpu : yes
    fpu_exception : yes
    cpuid level : 2
    wp : yes
    flags : fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe cid xtpr
    bogomips : 4784.12

    processor : 3
    vendor_id : GenuineIntel
    cpu family : 15
    model : 2
    model name : Intel(R) Xeon(TM) CPU 2.40GHz
    stepping : 9
    cpu MHz : 2400.627
    cache size : 512 KB
    physical id : 3
    siblings : 2
    fdiv_bug : no
    hlt_bug : no
    f00f_bug : no
    coma_bug : no
    fpu : yes
    fpu_exception : yes
    cpuid level : 2
    wp : yes
    flags : fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe cid xtpr
    bogomips : 4784.12

  2. #2
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    Re: CPUINFO

    Quote Originally Posted by Petros Koutoupis
    I am running on a Dual-Proc Server (2.4 GHz P4 Xeon(s)) and when I run the following command 'cat /proc/cpuinfo' it lists my processors on the command line. My question is, when I have two, why would it list four....does a Linux host see a hyper-threaded processor as two separate? I just find it a little odd that Processor 0 and 1 have the same physical ID of 0 and Processor 2 and 3 have the same physical ID of 3. Anybody else have an explanation to this?
    [root@holley mnt]# cat /proc/cpuinfo
    processor : 0
    vendor_id : GenuineIntel
    cpu family : 15
    model : 2
    model name : Intel(R) Xeon(TM) CPU 2.40GHz
    stepping : 9
    cpu MHz : 2400.627
    cache size : 512 KB
    physical id : 0
    siblings : 2
    fdiv_bug : no
    hlt_bug : no
    f00f_bug : no
    coma_bug : no
    fpu : yes
    fpu_exception : yes
    cpuid level : 2
    wp : yes
    flags : fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe cid xtpr
    bogomips : 4734.97

    processor : 1
    vendor_id : GenuineIntel
    cpu family : 15
    model : 2
    model name : Intel(R) Xeon(TM) CPU 2.40GHz
    stepping : 9
    cpu MHz : 2400.627
    cache size : 512 KB
    physical id : 0
    siblings : 2
    fdiv_bug : no
    hlt_bug : no
    f00f_bug : no
    coma_bug : no
    fpu : yes
    fpu_exception : yes
    cpuid level : 2
    wp : yes
    flags : fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe cid xtpr
    bogomips : 4784.12

    processor : 2
    vendor_id : GenuineIntel
    cpu family : 15
    model : 2
    model name : Intel(R) Xeon(TM) CPU 2.40GHz
    stepping : 9
    cpu MHz : 2400.627
    cache size : 512 KB
    physical id : 3
    siblings : 2
    fdiv_bug : no
    hlt_bug : no
    f00f_bug : no
    coma_bug : no
    fpu : yes
    fpu_exception : yes
    cpuid level : 2
    wp : yes
    flags : fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe cid xtpr
    bogomips : 4784.12

    processor : 3
    vendor_id : GenuineIntel
    cpu family : 15
    model : 2
    model name : Intel(R) Xeon(TM) CPU 2.40GHz
    stepping : 9
    cpu MHz : 2400.627
    cache size : 512 KB
    physical id : 3
    siblings : 2
    fdiv_bug : no
    hlt_bug : no
    f00f_bug : no
    coma_bug : no
    fpu : yes
    fpu_exception : yes
    cpuid level : 2
    wp : yes
    flags : fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe cid xtpr
    bogomips : 4784.12
    Yes, HT CPU's are seen as two seperate ones. SMP works by sending on thread to each CPU, as HT allows two threads to be run in one core, it must be seen as two. So two P4-HT's = 4 P4's.
    Nothing is worse than ten penguins fighting over which is better, vi or emacs.
    Registered Linux User #404402
    Finally I'm back on LF after a long while.

  3. #3
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    I thought so...thank you very much!

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  5. #4
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    How about when you have dual core with hyperthreading

    We have a system with Intel Dual-core, hyperthreaded cpus. It has a total of 4 cores and /proc/cpuinfo shows the siblings to be 4. We also have another server with the same specs except has total of 8 cores. The siblings is set to 2 in this case. Any ideas why? The 8 core server is using redhat 2.6.9-34.ELlargesmp kernel whereas teh 4 core is running 2.6.9-34 Elsmp kernel.

    Any ideas?

    Thanks
    - Ravi

  6. #5
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    Quote Originally Posted by kosaraju
    We have a system with Intel Dual-core, hyperthreaded cpus. It has a total of 4 cores and /proc/cpuinfo shows the siblings to be 4. We also have another server with the same specs except has total of 8 cores. The siblings is set to 2 in this case. Any ideas why? The 8 core server is using redhat 2.6.9-34.ELlargesmp kernel whereas teh 4 core is running 2.6.9-34 Elsmp kernel.

    Any ideas?

    Thanks
    - Ravi
    Actually, we figured it out (based on another post: http://kerneltrap.org/node/6284), looks like the kernel has acpi switch to disabled. In the grub.conf, after setting acpi=ht, the system comes up with 4 siblings in /proc/cpuinfo.

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