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I've been having an issue with VMware Fusion for some time now, where the VM (running Windows) runs fine initially, but will slow down to a grind after some time (best guess is a couple of hours). It's so slow that there's even a delay when typing.

The issue is not restricted to one VM: I have multiple Windows 7 VMs showing the same problem.

Any hints would be greatly appreciated in locating the source of this issue. Below are the configuration details and what I've attempted so far.


  • OS X 10.9.2
  • VMware Fusion 6.0.2
  • MacBook Pro (Mid 2012) Intel Core i7 2.3Ghz, 8GB RAM, Apple SSD
  • VM running Windows 7, 8 cores, 4GB RAM, SATA disk (not preallocated)
  • VM network: bridged

Changes (optimisations) performed so far

Windows (Guest):

  • Disabled all non-essential Windows services (e.g. Windows Search, Media, …)
  • Disabled NTFS access time modification
  • Disabled 8.3 filenames
  • Disabled Aero
  • Configured performance setting to Best performance

Mac (Host):

  • Disabled energy saving
  • Disabled automatic switching of display adapter


  • Moved the VM from external USB3 disk to internal SSD
  • VM compatibility set to VMware 6 (latest available)
  • Upgraded VM HD controller from SCSI or IDE to SATA
  • Set VM hard disk buffering to enabled
  • Disabled Troubleshooting (set to None)
  • Removed the appleListCache folder and replaced it with a dummy file


I created a support request with VMware to get to the bottom of this, and have received these two additional actions to try:

  • Reinstall the VMware tools
  • Exclude VMware from the AppNap feature in OSX by performing the following steps:

    1. Shutdown all Virtual Machines and quit Vmware Fusion.
    2. Go to Applications Folder and right click on VMware Fusion
    3. Select Get Info
    4. Select the option Prevent App Nap.
    5. Startup the Virtual Machine and recheck the issue.

Update 2:

In addition to the action above, VMware Support asked me to do the following:

  • Lower the number of CPU cores assigned to the VM — My MacBook Pro has 8 cores, of which VMware suggested only assigning 2 to a VM.
  • Lower the RAM assigned to the VM — I always assigned as much RAM as possible, leaving just enough for OSX. VMware suggested lowering this to 2GB.
  • Disable the shared folder feature — I normally share a few folders between the host and guest OS for easy file exchange.

While I didn't expect these changes to make any difference (esp. lowering the resources assigned to the guest OS), the VM's I've tried so far have all run stable and without any real hiccups, even when run from the USB3 external WD disk.

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I also have this problem with a similar setup to yours (OS X 10.9.2, Fusion 6.0.2). For me, the pattern is the vmware-vmx process uses more and more CPU (even if the VM isn't working) until it occupies an entire core. –  weiran Mar 14 at 12:19
@weiran Disabling AppNap and reinstalling VMware tools definitely helped (for my initial situation), although I'm having the same issue as you regarding the CPU load. Both kernel_taskand vmware-vmx are taxing the CPU while the VM itself is idling. I sent my findings to VMware support and await their response. –  Kristof Mar 17 at 11:57
any update from VMWare? –  weiran Apr 8 at 13:40
I'm also having the CPU load issue for vmware-vmx. Seems to get worse after the VMWare guest has been left running (but not used) in the background for a while. I'll try the AppNap thing you mentioned. My discrete GPU just failed. Wondering if the CPU heat was the cause :-\ ... –  bentayloruk Jul 2 at 10:32
Thanks a bunch for updating your question with info on how you solved your issues! –  Andreas Nilsson Jul 15 at 10:17

1 Answer 1

I had quite the same issue with my VM guests. (Also in VMWare 5.x on 10.8 by the way). What solved this issue for me was to disable the VM hard disk buffering. This seems to take all the available RAM of the system to buffer disk data (you can monitor this in activity monitor too). But giving back the RAM when needed by other system resources seems not to be one of the strong abilities of VMWare.

Since I disabled this I had no more issues with slowing down VM guests.

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