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Logical Processor in Hyper-v Technology RRS feed

  • Question

  • What is logical processor in Hyper-v technology.I could not understand.

    Virtual Processor I understand that its means we can run number of Virtual Machine in hyper-v environment. 


    hassan hanif

    Tuesday, January 15, 2013 1:13 PM

Answers

  • Hi!

    Logical processors are what's presented to the Hyper-V host as CPU's. While there is a difference between a physical CPU and a CPU core, Logical Processors are used to describe the amount of CPU a Hyper-V host can make use of, which are usually CPU cores, but hyperthreaded cores will show up as logical processors as well.



    This is further explained in this article: http://social.technet.microsoft.com/wiki/contents/articles/1234.hyper-v-concepts-vcpu.aspx
    • Edited by Mike_Andrews Tuesday, January 15, 2013 1:24 PM
    • Marked as answer by Lawrence, Tuesday, January 22, 2013 7:53 AM
    Tuesday, January 15, 2013 1:21 PM
  • MSFT has actually stopped using the term 'logical processors' in the virtualization documentation a couple years ago because it became too confusing.

    At one time a logical processor = a vCPU.  But that is no longer the case and is further muddied by hyperthreading.  Logical Processors is a concept that better relates to applications running within an OS.  And, as processors have gotten faster Logical Processors no longer correlates directly to VM vCPU density - it is better served by evaluating your workloads.


    Brian Ehlert
    http://ITProctology.blogspot.com
    Learn. Apply. Repeat.
    Disclaimer: Attempting change is of your own free will.

    • Proposed as answer by Ted Archer [MSFT] Wednesday, January 16, 2013 5:14 AM
    • Marked as answer by Lawrence, Tuesday, January 22, 2013 7:53 AM
    Tuesday, January 15, 2013 4:07 PM

All replies

  • Hi!

    Logical processors are what's presented to the Hyper-V host as CPU's. While there is a difference between a physical CPU and a CPU core, Logical Processors are used to describe the amount of CPU a Hyper-V host can make use of, which are usually CPU cores, but hyperthreaded cores will show up as logical processors as well.



    This is further explained in this article: http://social.technet.microsoft.com/wiki/contents/articles/1234.hyper-v-concepts-vcpu.aspx
    • Edited by Mike_Andrews Tuesday, January 15, 2013 1:24 PM
    • Marked as answer by Lawrence, Tuesday, January 22, 2013 7:53 AM
    Tuesday, January 15, 2013 1:21 PM
  • MSFT has actually stopped using the term 'logical processors' in the virtualization documentation a couple years ago because it became too confusing.

    At one time a logical processor = a vCPU.  But that is no longer the case and is further muddied by hyperthreading.  Logical Processors is a concept that better relates to applications running within an OS.  And, as processors have gotten faster Logical Processors no longer correlates directly to VM vCPU density - it is better served by evaluating your workloads.


    Brian Ehlert
    http://ITProctology.blogspot.com
    Learn. Apply. Repeat.
    Disclaimer: Attempting change is of your own free will.

    • Proposed as answer by Ted Archer [MSFT] Wednesday, January 16, 2013 5:14 AM
    • Marked as answer by Lawrence, Tuesday, January 22, 2013 7:53 AM
    Tuesday, January 15, 2013 4:07 PM
  • From what I understand "logical processor" isn't a term thats spesific to hyper-v.

    Logical processors is Intel terminology, and refer to the "extra" processors you gain from enabling Hyperthreading. But Microsoft seems to have adopted this terminology with its own dialect. check out this blog post (see paragraph 2) http://www.aidanfinn.com/?p=11193

    so it can be confusing, either you have 16 logical CPUs (2x4 core with hyper-threading) which isn't really 16 CPUs. or you have 2x8 core AMD with a total of 16 cores (no HT) which also is refered to as 16 logical CPUs but they are all physical no hokus pokus.

    hope i didn't confuse you even more =p

    Tuesday, January 15, 2013 4:46 PM