Detection of HyperThreading

Detection of HyperThreading

[Pieter De Wit]

Hello Guys,

I found something quite weird over the weekend. I have a few machines that 
claim they have HT (using cat /proc/cpuinfo). These machines doesn't 
really support HT (both with the number of threads and Intel's website)

I was wondering:

a) Is this the right list to send to (Sorry if not)

and

b) How is the HT flag detected ?

CPU's like the Core2 Duo E6300 doesn't have HT, but yet the flag is 
displayed ? See http://ark.intel.com/Product.aspx?id=27248 for info. I can 
send a dump of /proc/cpuinfo later from home.

Thanks,

Pieter

Re: Detection of HyperThreading

[Dave Jones]

On Mon, May 02, 2011 at 03:47:30PM +1200, Pieter De Wit wrote:
 > Hello Guys,
 > 
 > I found something quite weird over the weekend. I have a few machines that 
 > claim they have HT (using cat /proc/cpuinfo). These machines doesn't 
 > really support HT (both with the number of threads and Intel's website)
 > 
 > I was wondering:
 > 
 > a) Is this the right list to send to (Sorry if not)

no, this list is for cpu frequency scaling. linux-kernel would have been
more appropriate. 

 > and
 > 
 > b) How is the HT flag detected ?
 > 
 > CPU's like the Core2 Duo E6300 doesn't have HT, but yet the flag is 
 > displayed ? See http://ark.intel.com/Product.aspx?id=27248 for info. I can 
 > send a dump of /proc/cpuinfo later from home.
 
the 'ht' flag in /proc/cpuinfo means "this cpu knows how to report how
many siblings it has".  On a CPU which doesn't have hyperthreading, that
number will be 0.

	Dave