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Windows 8.1 pro hyper-v memory usage

    Question

  • Hello,

    I'm running windows 8.1 pro on a laptop with 8gb of ram. When running hyper-v i noticed that windows never seems to use more then 85% of the system memory (something that never happened in 8).

    Take a look at the following screenshot:

    Image

    Windows says 1247mb available, 120mb free and 1127mb standby! 

    Is this normal? is there any reason why windows refuses to use the standby memory for the VM needs?
    Thanks. 

    Best regards, Johnny Tordgeman.
    My Blog

    Wednesday, September 25, 2013 8:50 AM

Answers

  • Do you have Dynamic Memory enabled for your VM?

    If so, it only uses what it really needs, no more.

    And, I have a curious question, what are you running that you are at 85% RAM usage?  That actually seems pretty high for most modern applications.


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

    Wednesday, September 25, 2013 2:57 PM
    Moderator
  • So, compare what the hypervisor is allocating to the VM vs. what the VM is consuming.

    They are two different ways of looking at similar (but not equal) things.  In the VM it is the virtual memory manager, outside the VM it is the hypervisor and the physical RAM constraints.

    With Dynamic Memory there is a buffer that is given to the VM but never consumed, as when it is it gets added to.  So there is always a state of the VM running with a little extra, and never consuming all the RAM until the physical RAM resource is consumed and the physical limit is reached.

    If your VM is at its maximum that can be assigned using Dynamic Memory, then your applications within the VM could consume it all, as there would be no more allocated to the buffer for the VM.


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

    Wednesday, September 25, 2013 3:19 PM
    Moderator
  • Hi Johnny,

    this is a normal behaviour.

    To explain it simply: The "Standby" Memory is not free, but Windows is pre-loading files of applications which you access often into the memory in order to be able to start them faster. 

    In case another application needs this memory, it will be released. The actual free memory is only the 120MB.

    Best Regards,
    Jens


    jensit.wordpress.com

    Wednesday, September 25, 2013 5:23 PM
  • No, there is no way to do this. But as I said, in case it's needed, it will be made available by the system automatically.

    Best Regards,
    Jens


    jensit.wordpress.com

    Thursday, September 26, 2013 8:01 AM

All replies

  • Do you have Dynamic Memory enabled for your VM?

    If so, it only uses what it really needs, no more.

    And, I have a curious question, what are you running that you are at 85% RAM usage?  That actually seems pretty high for most modern applications.


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

    Wednesday, September 25, 2013 2:57 PM
    Moderator
  • Hey Brian,

    Thanks for your answer.

    As for Dynamic Memory - yes i use it, and i can clearly see that while the machine needs 4+gb ram (which should be available according to the graph) it only uses 3.5gb,

    As for what im running - 2 vms of win 2008 r2 + chrome (5 tabs open) + outlook 2003...

    Johnny.


    Best regards, Johnny Tordgeman.
    My Blog

    Wednesday, September 25, 2013 3:07 PM
  • So, compare what the hypervisor is allocating to the VM vs. what the VM is consuming.

    They are two different ways of looking at similar (but not equal) things.  In the VM it is the virtual memory manager, outside the VM it is the hypervisor and the physical RAM constraints.

    With Dynamic Memory there is a buffer that is given to the VM but never consumed, as when it is it gets added to.  So there is always a state of the VM running with a little extra, and never consuming all the RAM until the physical RAM resource is consumed and the physical limit is reached.

    If your VM is at its maximum that can be assigned using Dynamic Memory, then your applications within the VM could consume it all, as there would be no more allocated to the buffer for the VM.


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

    Wednesday, September 25, 2013 3:19 PM
    Moderator
  • Hi Johnny,

    this is a normal behaviour.

    To explain it simply: The "Standby" Memory is not free, but Windows is pre-loading files of applications which you access often into the memory in order to be able to start them faster. 

    In case another application needs this memory, it will be released. The actual free memory is only the 120MB.

    Best Regards,
    Jens


    jensit.wordpress.com

    Wednesday, September 25, 2013 5:23 PM
  • Hey Jens,

    Is there a way to limit that 'standby' memory?


    Best regards, Johnny Tordgeman.
    My Blog

    Wednesday, September 25, 2013 6:47 PM
  • No, there is no way to do this. But as I said, in case it's needed, it will be made available by the system automatically.

    Best Regards,
    Jens


    jensit.wordpress.com

    Thursday, September 26, 2013 8:01 AM
  • But the standby memory WITHIN a VM blocks it being used by another VM, right?
    Wednesday, March 19, 2014 9:36 PM