Useful details: Core2Duo mid 2010 Macbook Air, 128Gb SSD, 2Gb RAM.

Since I upgraded to Mountain Lion I've had this occur a few times. I'll be running my system and it'll completely freeze, no response to keyboard or trackpad other than the ability to hard power off.

In general it's when I have VirtualBox, Safari, Sublime Text 2, Terminal and Spotify running, but it'll be fine up until some unknown point and then thats it. Occasionally it'll unfreeze and I'll have messages about UI updates being suspended by (insert app here), but most of the time it forces the fans on high and starts trying to crunch on something.

Mountain Lion seems a bit snappier than Snow Leopard was for me on this machine, but it seems to be a large chunk worse for memory management, has anyone run across similar issues? Starting points for me to try optimise?

  • 2GB is quite low to be running virtual machines next to your regular workflow. How much memory have you assigned to your VMs? Also, did you check Activity Monitor for some more insights in whats going on?
    – Gerry
    Oct 12, 2012 at 18:08
  • Not much, about 700mb or so. It's always been fine about having VM's run up until Mountain Lion, even to the point of having multiple VMs running. I check into Console when it happens but it's pretty useless in most cases. Oct 12, 2012 at 18:52
  • 700MB more than a third of all your available memory. Are you running just one VM at a time?
    – Gerry
    Oct 12, 2012 at 19:02
  • Just the one VM, and yes whilst that is a third it never caused system freezes like this under Snow Leopard, in fact I've never seen system freezes with this level of regularity under OS X. Oct 12, 2012 at 19:58
  • The next time the machine gets slow or freezes, press this whale of a "shortcut": shift + control + option + command + period. That executes the sysdiagnose command which will snap all running processes and memory usage in detail. You can run this before you experience troubles from the terminal as well to have a good report to compare with the problematic one.
    – bmike
    Oct 12, 2012 at 20:00

1 Answer 1


Since re-install Mountain Lion my system freezing very often (randomly). It seems like disk freeze for 15-30sec. I suspect some bug. But after huge effort to investigate problem I found that in my case the solution is to delete sysem logs. In terminal:

sudo rm /var/log/*

I don't know what was wrong (it was clean install of ML) but it work for me (two days until now) and looks stable.

  • How much space is left on your disk? Maybe cleaning out /var/log was enough to get below a critical limit.
    – nohillside
    Oct 31, 2012 at 13:16
  • It is not hard disk space case - it is almost clean install with few application installed. Logs size was only 16MB so it is even not file size issue. I can confirm that mac still works stable. Nov 1, 2012 at 8:18

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