Re: replace a legacy proprietary RTOS (Real-Time executive) with NetBSD!

[Thor Lancelot Simon <tls%rek.tjls.com@localhost>]

On Mon, Jan 12, 2009 at 07:55:34PM +0200, Antti Kantee wrote:
> > space to control/configure the device.
> 
> What kind of drivers do you have in mind?  I have been thinking
> about making it possible to run the same device driver code in user-
> or kernelspace for quite a while now, but I haven't had any motivation
> apart from "would be nice" so far.  Your goal seems to be a special case
> of my goal.

Context-switching to userspace is going to _murder_ performance for
interrupt driven devices.  The NetBSD kernel is really, really not
designed to do this with reasonable performance.

It will be far worse than using a kernel thread as a device interrupt
handler, which is bad already.  It will probably also perform much
worse than running many entire applications using separate Xen virtuals,
with individual virtuals used to provide VM isolation for specific
device drivers.

Thor