Re: Userspace file systems & MKs (Re: silent semantic changes with reiser4)

Jeff Garzik
2004-08-31T05:57:01Z

Bill Huey (hui) wrote:
> DragonFly BSD, the only remotely functional open source BSD project on this
> planet, has plans in place to push certain kernel components like their VFS
> layer into userspace for easier debugging, testing and other things that go

That violates Jeff's First Rule, put the fast path stuff in the kernel.

> with developing file systems easily. If they back it with something like C++
> for doing constructor style type conversion on top of overloaded operators
> to back VFS data structure translation, could easily import stuff like most
> Linux file systems without major restructuring, say, if they had their
> translation library written. In this case, userspace kernel systems have
> some serious programming advantages over traditional kernels.

Sounds like security would be a pain in the ass :)

> They're also pushing an async syscall model to support a non-1:1 threading
> system for userspace unlike what Linux has done with futexes. It'll allow

messaging passing is also known as "really slow C function calls"

My PCI bus passes messages all the time. A message is in the eye of the
beholder.

Jeff