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I have a system running a financial trading application at a remote facility. I do not have access to the ILO/DRAC, but need to disable hyperthreading. The system runs Intel Nehalem 3.33GHz X5680 hex-core CPUs. I can reboot, but want to make sure that the system does not enable hyperthreading due to performance problems. Is there a clean way to do this from within Linux?

Edit: The noht directive added to the kernel boot command line did not work. Same for RHEL.

See: https://bugzilla.redhat.com/show_bug.cgi?id=440321#c9

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Yes. Append the noht parameter to the kernel on boot.

From http://www.faqs.org/docs/Linux-HOWTO/BootPrompt-HOWTO.html :

The `noht' Argument

This will disable hyper-threading on intel processors that have this feature.

If using lilo edit you /etc/lilo.conf (and run lilo afterwards) or if using grub then edit your /boot/grub/menu.lst .

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Is this functionally equivalent to disabling HT in the BIOS? – ewwhite Feb 15 '11 at 18:26
I don't know that for sure, but yes, I would expect noht to be equivalent to disabling it on the BIOS. – rems Feb 15 '11 at 18:52
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This is a Gentoo system. I tried the noht entry in the grub kernel command line. The system did not honor the noht command. Same for RHEL. See: bugzilla.redhat.com/show_bug.cgi?id=440321#c9 – ewwhite Feb 15 '11 at 19:41
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I had to wait until I could get into the ILO/Drac. The kernel boot parameters do not work on current Linux distributions.

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