Messages in this thread | | | Date | Tue, 31 May 2005 11:22:05 +1000 | From | Nick Piggin <> | Subject | Re: RT patch acceptance |
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James Bruce wrote: > Nick Piggin wrote: > >> Sorry James, we were talking about hard realtime. Read the thread. > > > hard realtime = mathematically provable maximum latency > > Yes, you'll want a nanokernel for that, you're right. That's because > one has to analyze every line of code, and protect against introduced > regressions, which is almost impossible given the pace that Linux-proper
Thank you, James. Now please tell that to Bill. It would seem that I haven't written enough "RT media apps" for him to take me seriously ;)
> > If you look at your first two messages in this thread however, you seem > to be offering a nanokernel approach (in particular RTAI as suggested by > Cristoph) as an alternative to the RT-patch. This is sort of confused > by the fact that Ingo called it "hard realtime" because he measured a > maximum latency during a stress test. Unfortunately that's not really > hard realtime if you are just measuring it; Rather its "really damn good > soft realtime". An analysis of code paths could be done to determine if > something really does satisfy hard-RT constraints, but to my knowledge > that's not on the table at this point. So you're discussing soft > realtime if you're dicussing the RT patch. >
No, I clarified the point that the direction the RT people want to go in is hard-realtime in the Linux kernel.
I'm very well aware of what the actual current PREEMPT_RT patch is, and I was never talking about that particular patch.
> So its really just a misunderstanding; Nanokernels certainly still have > a place for some applications even with the RT patches applied (Ingo has > said as much). However expecting audio applications such as Jack to > have to use RTAI is kind of silly, and would end up annoying the authors > of both (I'm sure the RTAI people have better things to do than support > ALSA drivers in RT mode). >
Yes, Jack is more of a soft realtime application, and in that case Linux supports it already today (although perhaps not very well - something the RT patch aims to improve).
[snip rest]
> > I really hope we understand each other now, but if not I guess it wasn't > to be. Hopefully someone got something out of reading this discussion, > but I won't be posting on this branch of the thread anymore either. >
It seems that you do understand my position now, yes. I'll try to refrain from posting further, too.
Nick
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