Messages in this thread | | | Subject | Re: [ANNOUNCE] Linux 2.6 Real Time Kernel | From | Lee Revell <> | Date | Sat, 09 Oct 2004 16:25:13 -0400 |
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On Sat, 2004-10-09 at 16:20, Robert Love wrote: > On Sat, 2004-10-09 at 15:47 -0400, Lee Revell wrote: > > > Yes. The upper bound on the response time of an RT task is a function > > of the longest non-preemptible code path in the kernel. Currently this > > is the processing of a single packet by netif_receive_skb. > > > > AIUI hard realtime is about bounded response times. How does this not > > qualify? > > I am actually in agreement with you, favoring this soft real-time > approach, but this is not bounded response time or determinism. There > are no guarantees, no measurements conducted with all possible inputs, > sizes, errors, and so on. This soft real-time approach gives great > average case--but the worst case is only a measurement on a specific > machine in a specific workload.
I did not mean to say that VP approach alone can do hard realtime, that was just an example. But, when combined the MontaVista approach of turning all but ~20 spinlocks into mutexes, it seems like the amount of non-preemptible code is small enough that you could analyze it all and start to make hard RT guarantees.
Lee
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