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My virtual machine is extremely slow and consumes about 100% of the Mac CPU resources

  • Parallels Desktop for Mac Standard Edition
  • Parallels Desktop 11 for Mac Pro Edition

Important: If you experience a performance degradation after upgrading your Mac® to OS X® 10.10 Yosemite, please see KB 122767.


My virtual machine is extremely slow; it takes a long time to boot the guest operating system (Windows®, Linux or Mac OS X), and the overall performance of the virtual machine is very poor. My virtual machine's process (prl_vm_app or Parallels VM) in the Activity Monitor consumes about 100% of the Mac CPU right from the start and even if the virtual machine is idle.


There can be several reasons your virtual machine is acting this way:

  1. Virtual Machine misconfiguration
  2. Parallels Desktop misconfiguration
  3. Device conflicts in Mac OS X


  1. Start Parallels Desktop, but do not start your virtual machine.
  2. In Finder, go to Applications > Utilities. Locate and start the Activity Monitor.
  3. In the Activity Monitor, arrange all processes by % CPU.
  4. Launch your virtual machine and check how much CPU is used by the prl_vm_app or Parallels VM process. (Both are names for virtual machine processes in different versions of Parallels Desktop.)

If Parallels VM (prl_vm_app) is taking about 100% CPU right after you start the virtual machine and then continues to consume a high percentage of CPU (close to 100%), please perform the following test:

  • Stop your currently running virtual machine.
  • In Parallels Desktop 10, right-click on the Parallels Desktop icon in the Dock and select New.

    In previous versions of Parallels Desktop, click on File from the Parallels Desktop menu at the top of the screen and select New.

    Choose Install Windows or another OS from DVD or image file > Continue.

    In Parallels Desktop 10, if the wizard is trying to locate an operating system automatically, click Locate manually, then select Continue without a source and click Continue:


    In previous versions of Parallels Deskrtop, select Continue without disk > Continue:

    Leave the default Windows 7 OS and click OK.

  • Choose Like a PC > Continue > type in the new virtual machine's name (for example, "test"), and click Continue. Your new virtual machine will start.
  • Wait until the virtual machine reports that "No boot device is available."
  • Switch to the Activity Monitor and check how much CPU is now consumed by the new virtual machine..

    a. If the new test virtual machine consumes the same high percentage of CPU (cllse to 100%), then please do the following:

    • Disconnect all USB devices from the Mac (including USB printers, flash drives, external drives, etc.).
    • Reboot your Mac.
    • Uninstall Parallels Desktop as per KB 122653 for Parallels Desktop 10, KB 116992 for Patallels Desktop 9, or KB 114624 for Parallels Desktop 8.
    • Reboot your Mac.
    • Install Parallels Desktop again following KB 122647 for Parallels Desktop 10, KB 116993 for Parallels Desktop 9 or KB 114623 for Parallels Desktop 8.
    • Start your virtual machine (the original one or the test one) and check the CPU consumption in the Activity Monitor. The issue should be fixed now.

    b. If the new test virtual machine consumes a low percentage of CPU (between 0,5 and 20%):

    • Stop both virtual machines (the original one and the test one) if they are running.
    • Go to the Window menu > Control Center in Parallels Desktop 10 or Virtual machines List in previous versions > right-click on the test virtual machine and choose Configure > Hardware > Hard Disk 1 > Source: Choose an image file.

    • Navigate to the original virtual machine's hard disk file. (By default it is located in Macintosh HD > Users > username > Documents > Parallels > original Virtual machine name.pvm > Virtual machine name.hdd > Virtual machine name.hdd.)
    • Click Open.
    • Start the test virtual machine and see if the issue persists. The issue should be fixed now.
    • If the issue is fixed, you can go to the test virtual machine's Configuration > General and change its name to the desired name.
    • Then open the Control Center or Virtual machines List one more time, locate your original virtual machine, right-click on it, and choose Remove > Keep files.

    You can also simply move the original virtual machine's Hard Disk bundle (.hdd) into a new virtual machine .pvm bundle. Afterward, you will have to correct the Hard Disk 1 Source in a new virtual machine Configuration > Hardware > by pointing it to a moved .hdd.

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