Subject: Re: Floating point in the kernel
To: Chris G. Demetriou <>
From: John F. Woods <>
List: tech-kern
Date: 09/18/1998 13:52:22
> I believe that the notion was that one day that might be 'fixed.'
> But, because there are lots of them and they may switch often, you
> really want kernel thread switching ot be as lightweight as
> possible...  So i still think it's unlikely.

And (as I was going to point out in a message eaten by a PPP line crash)
once you *have* kernel threads, you find that they're the answer to just
about every kernel programming problem, so (as you said) you want them to
be as lightweight as possible.

But I hope that threads (user threads, anyway) will not be made *too*
lightweight:  if the kernel is aware of user threads and schedules them
(as opposed to threads existing as figments of user processes' imaginations),
then (a) you get non-blocking I/O for "free" (one thread blocking in I/O
doesn't block other threads in that process), and (b) different threads of
a process can make use of multiple CPUs (OK, so that's more interesting on
a 256 processor KSR machine than in is on a dual-Pentium... ;-) ).  That
makes threads heavier-weight than one might like (and, worse, leads to
people searching for new terms like "fibers" for threads that exist as 
figments of a thread's imagination... ;-) ), but it makes threads just so
much more useful.