How does Linux number hyperthreaded processors?

May 08, 2008 2 Replies
M

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


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A

have you examined /proc/cpuinfo?

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P

There is a small script i wrote that, may help you, here:

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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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