[Ukfreebsd] Disabling hyperthreading on Intel CPUs

Robert N. M. Watson rwatson at FreeBSD.org
Wed Jan 26 12:47:23 GMT 2011


On 26 Jan 2011, at 11:16, Robert N. M. Watson wrote:

> FreeBSD treats threads as CPU cores, so you should be able to disable them in device.hints using lines like:
> 
>  hint.apic.0.disabled="1"


Actually, I think this is incorrect -- it should be:

	hint.lapic.X.disabled="1"

Where X is the CPU number.

However: I can't help but wondering if a better model using to use the cpuset(1) facility to run your jobs under specific subsets of available CPUs. You could create a cpuset representing "only the first thread on every core" -- the kernel will still use other cores for its own work, but for userspace-intensive workloads, the results would be similar to disabling the threads.

Robert


More information about the Ukfreebsd mailing list