DragonFly kernel List (threaded) for 2006-01
Re: cowloop technology
A devfs is not going to impact performance. That isn't the problem
with it. There are three problems with it.
First, the dynamic nature of a devfs means that set permissions
and ownership for devices are not 'sticky' across reboots unless you
add hacks to adjust them on boot.
Second, devfs does not solve the basic incorrectness of relying on the
device namespace to list all available devices (e.g. all slices, all
partitions, all ttys, all ptys, and so forth) when what you really want
is simply a namespace interpretation that routes a device name to the
proper device code.
Third, one of the reasons a devfs is created is to get rid of the
major/minor number paradigm. I think this is a grand idea, and FreeBSD
has done it, but I don't think you need a devfs to accomplish this
feat. I think all you need is to have base names in a special
filesystem or filesystem overlay and a VFS layer which parses the name
out and accesses the correct device with the correct parameters.