disable the hyper threading ON Linux

[Santhosh kumar]

All ,

Adding noexec=off in /boot/grub/grub.conf will help?



Here is my /boot/grub/grub.conf



# grub.conf generated by anaconda

#

# Note that you do not have to rerun grub after making changes to this file

# NOTICE:  You have a /boot partition.  This means that

#          all kernel and initrd paths are relative to /boot/, eg.

#          root (hd0,0)

#          kernel /vmlinuz-version ro root=/dev/vg00/lv00

#          initrd /initrd-version.img

#boot=/dev/sda

default=1

timeout=50

splashimage=(hd0,0)/grub/splash.xpm.gz

title Red Hat Enterprise Linux AS (2.4.21-37.ELsmp)noexec=off

        root (hd0,0)

        kernel /vmlinuz-2.4.21-37.ELsmp ro root=/dev/vg00/lv00 noexec=off

        initrd /initrd-2.4.21-37.ELsmp.img

title Red Hat Enterprise Linux AS-up (2.4.21-37.EL)

        root (hd0,0)

        kernel /vmlinuz-2.4.21-37.EL ro root=/dev/vg00/lv00

        initrd /initrd-2.4.21-37.EL.img



Thanks
Santhosh


On 11/29/07, Aaron <dell at microchp.org> wrote:
>
> Dan Stromberg wrote:
> >
> > Whether hyperthreading is faster or slower probably depends on your
> > workload.
> >
> > Granted, hyperthreading allows more of the CPU to be engaged at any
> > given moment, but it may also halve your Ln cache size.
> >
> > On Nov 28, 2007 11:06 AM, vadim <vadim at ovguide.com
> > <mailto:vadim at ovguide.com>> wrote:
> >
> >     Same here - BIOS is the only way to disable it. On a personal note,
> an
> >     HT CPU performs faster than non HT CPU - tried that a few years
> back.
> >     -V
> >
> >     David Chait wrote:
> >     > I'm fairly certain that this is only done via the machine Bios,
> >     not the OS.
> >     >
> >     > -David
> >     >
> >     >
> >     > Santhosh kumar wrote:
> >     >> Some one guide me how to disable the hyper threading on Dell
> >     2650? I
> >     >> am running rhel 3 update 6. Is there any way I can do this
> >     >> modification from the OS level.
> >     >>
> >     >>
> >     >>
> >     >> Thanks in advance
> >     >> Santhosh
> >     >>
> >     >>
> >     >>
> >
> ------------------------------------------------------------------------
> >     >>
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>
>
>
> That is correct.  Depending on what you are doing will determine the
> performance gain or loss.  Compression, decompression,
> encoding/transcoding, decryption, Oracle, MySQL all seem to benefit from
> HT when they have multiple threads or daemons.  I disable it on servers
> that have one or two heavy IO processes.  With other applications your
> milage may vary and you should perform your own benchmark testing.  I
> have found that one some weblogic/Jboss server deployments, I get more
> performance with it off.
>
> If you are going to disable it, I would suggesting using the BIOS to
> control that.  Turning it off in the kernel just further cripples your
> performance, as the other logical processor is technically still on in
> the hardware, you just are not utilizing it.  That is almost akin to
> using UP kernel on SMP machines, sortof.
>
>
> --Aaron
>
>
>
>
>
>


-- 
Best regards,
Santhosh
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