machdep.hlt_logical_cpus missing in 4.9-Release?

John Baldwin jhb at
Thu Jan 15 10:42:29 PST 2004

On Thursday 15 January 2004 05:48 am, Hall J D (ISeLS) wrote:
> I've recently installed 4.9-Release (from the ISOs) on a twin Xeon system
> and compiled a generic SMP kernel (GENERIC with SMP and APIC_IO enabled).
> The problem I'm having is the system is using the logical HyperThreading
> CPUs even though I don't want it to.
> The errata for 4.9-Release says that the logical CPUs are prevented from
> executing user processes by default, they are not on my system. It also
> says you can control this behaviour by change the value of the
> machdep.hlt_logical_cpus sysctl(8) variable. My sysctl doesn't seem to know
> about this variable.
> I've checked the archives and someone else had this problem back in
> November but I can't see any replies other than "machdep.hlt_logical_cpus
> should be there".
> Can anyone offer some advise please.

Well, you can do 'sysctl machdep.hlt_cpus=10 to get the same effect to turn 
off CPU's 1and 3.  I am not sure why you are not getting the sysctls.  Are 
you familiar with C?

John Baldwin <jhb at>  <><
"Power Users Use the Power to Serve"  =

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