only one logical CPU used in Xeon

won.derick at yahoo.com won.derick at yahoo.com
Thu Mar 12 07:28:16 PDT 2009


--- On Thu, 3/12/09, John Baldwin <jhb at freebsd.org> wrote:
> 
> -----Inline Attachment Follows-----
> 
> On Wednesday 11 March 2009 11:01:51
> am Oliver Fromme wrote:
> > Here's how you can see the details in the demsg
> output:
> > The older machine:
> > 
> >  > Features = 0xbfebfbff <...,HTT,...>
> > 
> > The "HTT" bit in the features bitmask indicates that
> the
> > processor supports hyperthreading.
> 
> No, that flag just means it supports a register where you
> can ask for the 
> total number of threads/cores per package.  Multi-core
> CPUs that don't have 
> hyperthreads have 'HTT' set, but when you read the
> registers properly you see 
> that they have 1 thread per core.
> 

Does this mean that the # of logical CPUs per core is not enough to determine whether the machine supports hyperthreading or not? You've said earlier that the newer machine is not hyperthreaded, so I'm assuming that there is another part in the dmesg output that says so. more guidance pls.



      



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