Messages in this thread | | | Date | Tue, 25 Feb 2003 06:59:12 -0800 | Subject | Re: Minutes from Feb 21 LSE Call | From | Bill Huey (Hui) <> |
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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: http://linuxdevices.com/articles/AT6476691775.html
A paper I've take interest in recently from the top-level link: http://www.linuxdevices.com/articles/AT6078481804.html
People I originally talked to that influence my view on this: http://www-2.cs.cmu.edu/~rajkumar/linux-rk.html
> 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.
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