uvm replaced the machvm in netbsd. 

For a time, Chuck set it up to run in parallel with the existing VM. You could start a process and pick which vm it used. For a while, it defaulted to the existing one. Then, at some point, it defaulted to uvm. Then, at some point, the old one was removed.

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uvm replaces machvm netbsd

chuck was a long time contributor to netbsd IIRC, but last time we talked, he was using Linux.

ron