HyperThreading CPU's
Vivek Khera
vivek at khera.org
Mon Mar 15 12:58:32 PST 2004
On Mar 15, 2004, at 3:38 PM, Marius M. Rex MARIUS wrote:
> In my fairly recent version of the UPDATING file for 4.9-stable it
> states
> that I have to use sysctl to modify the value of
> 'machdep.hlt_logical_cpus' to
> '0' to get all of my logical CPU's enabled under hyperthreading.
>
> Is this change still necessary? sysctl spits that oid out as unknown
> when I try to look at it. I do have similar oids but nothing that
> matches that
> value precisely:
The OID only shows up if your CPU reports the "HTT" feature. Look at
/var/run/dmesg.boot and look for the line "Features=" under the CPU
information right near the top of the kernel boot messages. One of the
features should be "HTT".
If you disable hyperthreading in your bios, then it will not be there,
and the OID will not be there either. later in the kernel boot
messages it should show the APIC configuration/reprogramming and
indicate multiple processors are present. I'm not sure if you need to
enable multiple CPU support for HTT, since both of my HTT machines have
two physical processors in them. I have never tried it on a single cpu
box.
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Vivek Khera, Ph.D. Khera Communications, Inc.
Internet: khera at kciLink.com Rockville, MD +1-301-869-4449 x806
AIM: vivekkhera Y!: vivek_khera http://www.khera.org/~vivek/
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