disable the hyper threading ON Linux

[Davis_Phillips at Dell.com]

"noexec=off" is the intel XD bit. The processor on the PE 2650 would not
have this particular option.
 
But at the place where the "noexec=off" the "noht" flag could be added
instead. 
 


________________________________

From: linux-poweredge-bounces at dell.com
[mailto:linux-poweredge-bounces at dell.com] On Behalf Of Santhosh kumar
Sent: Thursday, November 29, 2007 6:48 AM
To: Aaron
Cc: David Chait; linux-poweredge-Lists
Subject: Re: disable the hyper threading ON Linux


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> 
	> <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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