I recently updated to OSX Mavericks, and it’s been completely painless except for a single issue. I use a fullscreen iTerm2 instance on my second monitor to output test results, but occasionally it would freeze and not update the output until I tabbed away from MacVim.

I suspect that this was because of App Nap, but actually I’m not sure because I accidentally changed two things at once:

Disabling App Nap for iTerm2

  1. Update to the newest iTerm2 (necessary to change the App Nap setting)
  2. Open Finder
  3. Navigate to Applications > iTerm.app
  4. Press Cmd-I (Get Info)
  5. Under General, tick “Prevent App Nap”

Get rid of menu bar on secondary monitor

  1. Open System Preferences
  2. Navigate to Mission Control
  3. Untick “Displays have seperate Spaces”

EDIT: As mentioned by George in the comments, it is now possible to disable App Nap directly in the iTerm preferences. Only available in the nightly build at the time of writing.