[openstack-dev] [openstack-dev[[nova] Simple question about sorting CPU topologies

Chris Friesen chris.friesen at windriver.com
Tue Jun 20 16:53:20 UTC 2017

On 06/20/2017 06:29 AM, Jay Pipes wrote:
> On 06/19/2017 10:45 PM, Zhenyu Zheng wrote:
>> Sorry, The mail sent accidentally by mis-typing ...
>> My question is, what is the benefit of the above preference?
> Hi Kevin!
> I believe the benefit is so that the compute node prefers CPU topologies that do
> not have hardware threads over CPU topologies that do include hardware threads.
> I'm not sure exactly of the reason for this preference, but perhaps it is due to
> assumptions that on some hardware, threads will compete for the same cache
> resources as other siblings on a core whereas cores may have their own caches
> (again, on some specific hardware).

Isn't the definition of hardware threads basically the fact that the sibling 
threads share the resources of a single core?

Are there architectures that OpenStack runs on where hardware threads don't 
compete for cache/TLB/execution units?  (And if there are, then why are they 
called threads and not cores?)


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