How does Linux number hyperthreaded processors? - Embedded

This is a discussion on How does Linux number hyperthreaded processors? - Embedded ; I have a dual Zeon processor that Linux lists as 4 processors (there are two physical ones and each has two hyperthread units. I am assigning threads to individual processors and I want them on different physical processors. Are processor ...

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Thread: How does Linux number hyperthreaded processors?

  1. How does Linux number hyperthreaded processors?

    I have a dual Zeon processor that Linux lists as 4 processors (there are two
    physical ones and each has two hyperthread units. I am assigning threads to
    individual processors and I want them on different physical processors. Are
    processor 0 and 1 on the same physical processor and 2 and 3 on the other
    processor or are 0 and 1 on two different physical processors and 3 and 4
    their hyperthread pairs?

    I am upgrading my system from a dual Pentium 3 where this was not an issue.
    If worse comes to worse I can disable hyperthreading, but I would like to
    clarify this if possible.

    Thanks in advance,

    Marco
    ________________________
    Marc Reinig
    UCO/Lick Observatory
    Laboratory for Adaptive Optics



  2. Re: How does Linux number hyperthreaded processors?

    On Thu, 8 May 2008 07:57:14 -0700, Marc Reinig wrote:
    >I have a dual Zeon processor that Linux lists as 4 processors (there are two
    >physical ones and each has two hyperthread units. I am assigning threads to
    >individual processors and I want them on different physical processors. Are
    >processor 0 and 1 on the same physical processor and 2 and 3 on the other
    >processor or are 0 and 1 on two different physical processors and 3 and 4
    >their hyperthread pairs?


    >I am upgrading my system from a dual Pentium 3 where this was not an issue.
    >If worse comes to worse I can disable hyperthreading, but I would like to
    >clarify this if possible.


    have you examined /proc/cpuinfo?

  3. Re: How does Linux number hyperthreaded processors?

    On May 8, 3:57 pm, "Marc Reinig" wrote:
    > I have a dual Zeon processor that Linux lists as 4 processors (there are two
    > physical ones and each has two hyperthread units. I am assigning threads to
    > individual processors and I want them on different physical processors. Are
    > processor 0 and 1 on the same physical processor and 2 and 3 on the other
    > processor or are 0 and 1 on two different physical processors and 3 and 4
    > their hyperthread pairs?
    >
    > I am upgrading my system from a dual Pentium 3 where this was not an issue.
    > If worse comes to worse I can disable hyperthreading, but I would like to
    > clarify this if possible.
    >
    > Thanks in advance,
    >
    > Marco
    > ________________________
    > Marc Reinig
    > UCO/Lick Observatory
    > Laboratory for Adaptive Optics


    There is a small script i wrote that, may help you, here:
    http://projects.ninet.org/index.php/CPUInfo

    It only detects if the CPU can hyperthread atm, as I wrote it to check
    my servers, I cant reboot the servers to test the differences with HT
    on and off. If you use it and can see the differences. then feel free
    to update the script. I would appraciate any changes making their way
    back to my site.

    If you have an intel machine that has ht and you post the /proc/
    cpuinfo contents with it on and off then we maybe can tell you the
    differences..

    The key lies in the combination of physical id and logical id iirc.


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