Subject: Re: upcalls?
To: Bill Sommerfeld <>
From: Charles M. Hannum <>
List: tech-kern
Date: 12/08/1999 09:01:48
Bill Sommerfeld <> writes:

> > For scheduler activations, a way for the kernel to arrange to call a
> > specific userlevel function is needed, as well as passing it
> > arguments.
> Well, the way to go here is to spawn a new kernel thread for this
> purpose, and then have it return into a signal-trampoline-like piece
> of userspace code.

This is the absolute, complete antithesis of scheduler activations, as
it gives you an insane amount of overhead.  It would actually be
*cheaper* to just have one `kernel thread' per user thread.

Please read the papers.