Re: [patch] Real-Time Preemption, -RT-2.6.10-rc1-mm3-V0.7.23

From: Mark_H_Johnson
Date: Wed Nov 10 2004 - 12:39:00 EST

>you have to build another kernel for them. irqs-off and preempt-off
>timing can be mixed freely (and both can be enabled in the same kernel),
>but wakeup timing deserves its own .config space and since it's not
>mixable with the other two methods i didnt see much point in enabling
>all 3 at once with strange dependencies between them. Is this a big
>issue? Normally i think the wakeup timing is more than enough to get a
>feel of latencies, and if something specific is suspected the other ones
>can be turned on.

Just that it takes an hour or so to rebuild the kernel plus the
disk storage to keep two kernels instead of one.

The wakeup latencies I am seeing are all quite small, but the overhead
I am seeing at the application level have been quite high. Only 40 wakeup
latencies > 50 usec in a half hour of testing. I guess I'll build a
.24 without wakeup timing to see what kind of problems I'm having.
I can send you the wakeup timing traces if you are interested but
they are all really short (< 100 usec) or appear to indicate a hardware
contention problem (one step at 100 usec or so).


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