Can I disable HyperThreading in OS?

Bob Johnson fbsdlists at gmail.com
Fri Oct 7 06:52:01 PDT 2005


On 10/7/05, Andrew P. <infofarmer at gmail.com> wrote:
> On 10/7/05, hshh <hunreal at gmail.com> wrote:
> > My /boot/loader.conf,
> >    userconfig_script_load="YES"
> >    kern.ipc.nmbclusters="65536"
> >
> >  I sure there are only 2 physical processors inside the box.
> >  Attached dmesg infomation.
> >  -----------------------------------------
> >  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.
> >  FreeBSD 4.11-RELEASE-p12 #1: Fri Sep 30 17:05:26 CST 2005
> >      root at www.sa20.com:/usr/obj/usr/src/sys/www
> >  Timecounter "i8254"  frequency 1193182 Hz
> >  CPU: Intel(R) Xeon(TM) CPU 1.80GHz (1794.19-MHz 686-class CPU)
> >    Origin = "GenuineIntel"  Id = 0xf27  Stepping = 7
> >
> >
> Features=0xbfebfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CLFLUSH,DTS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE>
> >    Hyperthreading: 2 logical CPUs
> >  real memory  = 2146959360 (2096640K bytes)
> >  avail memory = 2087632896 (2038704K bytes)
> >  Programming 24 pins in IOAPIC #0
> >  IOAPIC #0 intpin 2 -> irq 0
> >  Programming 24 pins in IOAPIC #1
> >  Programming 24 pins in IOAPIC #2
> >  FreeBSD/SMP: Multiprocessor motherboard: 4 CPUs
> >   cpu0 (BSP): apic id:  0, version: 0x00050014, at 0xfee00000
> >   cpu1 (AP):  apic id:  1, version: 0x00050014, at 0xfee00000
> >   cpu2 (AP):  apic id:  6, version: 0x00050014, at 0xfee00000
> >   cpu3 (AP):  apic id:  7, version: 0x00050014, at 0xfee00000
> >   io0 (APIC): apic id:  2, version: 0x00178020, at 0xfec00000
> >   io1 (APIC): apic id:  3, version: 0x00178020, at 0xfec80000
> >   io2 (APIC): apic id:  4, version: 0x00178020, at 0xfec80400
> >  Preloaded elf kernel "kernel" at 0xc02e6000.
> >  ....
> >  SMP: AP CPU #1 Launched!
> >  SMP: AP CPU #3 Launched!
> >  SMP: AP CPU #2 Launched!
>
> Please, cc freebsd-questions and append your answers,
> don't prepend them.
>
> Post your kernel config as well please. I have very little
> experience with SMP systems, but someone from the
> list would probably like to look into your problem.

I read somewhere that some releases of FreeBSD by default enable HTT
for servicing interrupts but not for userland processes.  They
mentioned a sysctl for modifying this behavior.  I thought it was
described in /usr/src/UPDATING but I can't find it now.

- Bob


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