Date: Tue, 10 Oct 2006 13:11:15 -0500 From: Brooks Davis <brooks@one-eyed-alien.net> To: Garance A Drosihn <drosih@rpi.edu> Cc: freebsd-smp@freebsd.org Subject: Re: Hyperthreading Issues (on Athlon64?) Message-ID: <20061010181115.GB75278@lor.one-eyed-alien.net> In-Reply-To: <p06230904c1518ddcf554@[128.113.24.47]> References: <20061009114520.1355.qmail@web8608.mail.in.yahoo.com> <452AE62B.4000000@nokia.com> <p06230904c1518ddcf554@[128.113.24.47]>
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--IiVenqGWf+H9Y6IX Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable 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 > >> =20 > >> =20 > >> How do i Find if the CPU is Hyperthreading enabled or not? I have=20 > >>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 =3D "GenuineIntel" Id =3D 0xf27 Stepping =3D 7 > > > >Features=3D0xbfebfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,P= GE,MCA,CMOV,PAT,PSE36,CLFLUSH,DTS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE> > > Features2=3D0x4400<CNTX-ID,<b14>> > > Hyperthreading: 2 logical CPUs > >real memory =3D 2147483648 (2048 MB) > >avail memory =3D 2100936704 (2003 MB) >=20 > Huh. > I just got a dual-core Athlon64 machine, and the features list for > it says: >=20 > Features=3D0x178bfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP, > MTRR,PGE,MCA,CMOV,PAT,PSE36,CLFLUSH,MMX,FXSR,SSE,SSE2, > HTT> > --- >=20 > 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. -- Brooks --IiVenqGWf+H9Y6IX Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.5 (FreeBSD) iD4DBQFFK+JCXY6L6fI4GtQRAkyRAJilrOFwvKRAN8PBQwlUY8ZD7fyLAKCrdb5e SsOFlagCl3wquQ7/3Yz1Dg== =VReY -----END PGP SIGNATURE----- --IiVenqGWf+H9Y6IX--
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