I have been using Hudson in master/salve setup, running a large matrix style
project. There are several slaves running in a virtualized environment (VMware)
on the same physical machine as the Hudson server.

Building on several slaves at the same time consumes a large amount of resources
and causes the builds to fail (due to timeouts, etc).

It would be nice to be able to specify that several different slaves share the
same physical hardware. The total number of executors running should be limited
to a user defined value. This would allow the user to build on a large number
of slaves without consuming all the resources.