Hyperthreading Issues (on Athlon64?)
brooks at one-eyed-alien.net
Tue Oct 10 11:11:29 PDT 2006
On Tue, Oct 10, 2006 at 01:59:39PM -0400, Garance A Drosihn wrote:
> At 10:15 AM +1000 10/10/06, Arthur Hartwig wrote:
> >ext kumaresh pandian wrote:
> >>Hi all
> >> How do i Find if the CPU is Hyperthreading enabled or not? I have
> >>tried using the mtables but i'm not able to figure it out.
> >Look for the HTT bit in the CPU features displayed when FreeBSD starts
> >up. Here's an example from one of my systems, HTT is third from the
> >right hand end of the CPU features list.
> >Copyright (c) 1992-2005 The FreeBSD Project.
> >Copyright (c) 1979, 1980, 1983, 1986, 1988, 1989, 1991, 1992, 1993, 1994
> > The Regents of the University of California. All rights reserved.
> >hartwig 1 10.09.2006-151040MPTable: <OEM ID PRODUCT ID >
> >Timecounter "i8254" frequency 1193182 Hz quality 0
> >CPU: Intel(R) Xeon(TM) CPU 2.80GHz (2794.59-MHz 686-class CPU)
> > Origin = "GenuineIntel" Id = 0xf27 Stepping = 7
> > Features2=0x4400<CNTX-ID,<b14>>
> > Hyperthreading: 2 logical CPUs
> >real memory = 2147483648 (2048 MB)
> >avail memory = 2100936704 (2003 MB)
> I just got a dual-core Athlon64 machine, and the features list for
> it says:
> My dmesg does not have the line about "Hyperthreading: 2 logical CPUs",
> though. But I had been pretty sure the Athlon64 chips didn't have any
> hyperthreading support. Why is the HTT there?
To trick license managers and schedulers that know HTT, but not true
multi-core. They report the physical cores a logical cores and then add
an additional flag saying that they are really physical.
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