mitchellh/vagrant — pull request #1391 by canausa (2013-02-26 02:39:37+00:00)
Title: Forks off the entire vm.up command for each vm

Current Issues:
* The maximum number of concurrent forks allowed is currently hard coded to 2. It should probably be moved to a config variable.
* The .vagrant file is currently not be populated correctly. This is probably due to the forks clobbering the file because it is not longer a sequential operation. Will need to update the datastore to fix.
* The is currently a sleep. I am definitely running into issue with virtual box not liking when 2 different forks are trying to perform commands at the same time. I currently am using a sleep to help stagger the forks a little. But it may be best to add in locks so that only 1 fork is allowed to send a command to virtual box at a time, so I can remove the sleep.

With your feedback, I can resolve some of the issues above.