[lkml]   [2003]   [Feb]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: Minutes from Feb 21 LSE Call
On Tue, Feb 25, 2003 at 03:30:59PM +0000, Alan Cox wrote:
> Nothing is conceptually obvious. Thats the difference between 'science'
> and engineering. Our bridges have to stay up.

Yes, I absolutely agree with this. It shouldn't be the case where one is
over the other, they should have a complementary relationship.

> > It's about getting relationship inside the kernel to respect and be
> > controllable by the scheduler in some formal manner, not some random
> > not-so-well-though-out hack of the day.
> Prove it, compute the bounded RT worst case. You can't do it. Linux, NT,
> VMS and so on are all basically "armwaved real time". Now for a lot of
> things armwaved realtime is ok, one 'click' an hour on a phone call
> from a DSP load miss isnt a big deal. Just don't try the same with
> precision heavy machinery.
> Its not a lack of competence, we genuinely don't yet have the understanding
> in computing to solve some of the problems people are content to armwave
> about.
> If I need extremely high provable precision, Victor's approach is right, if
> I want armwaved realtimeish behaviour with a more convenient way of working
> then Victor's approach may not be the best.

I spoke to some folks related to CMU's RTOS group about a year ago and was
influenced by their preemption design in that they claimed to get tight RT
latency characteristics by what seems like some mild changes to the Linux
kernel. I recently start to investigate their stuff, took a clue from them
and became convince that this approach was very neat and elegant. MontaVista
apparently uses this approach over other groups that run Linux as a thread
in another RT kernel. Whether this, static analysis tools doing rate{deadline}-monotonic
analysis and scheduler "reservations" (born from that RT theory I believe)
are unclear to me at this moment. I just find this particular track neat
and reminiscent of some FreeBSD ideals that I'd like to see fully working in
an open source kernel.

Top level link to many papers:

A paper I've take interest in recently from the top-level link:

People I originally talked to that influence my view on this:

> Its called engineering. There are multiple ways to build most things, each
> with different advantages, there are multiple ways to model it each with
> more accuracy in some areas. Knowing how to use the right tool is a lot
> more important than having some religion about it.

Yes, I agree. I'm not trying to make a religious assertion and I don't
function that way. I just want things to work smoother and explore some
interesting ideas that I think eventually will be highly relevant to a
very broad embedded arena.


To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

 \ /
  Last update: 2005-03-22 13:33    [W:0.130 / U:0.796 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site