Probably small. However
1. It also does signal processing and rescheduling on the return path
(the latter is now a lot cheaper with current->need_resched on smp)
2. You often have woken a task but dont want it to leap into life instantly
> >From looking at the current Linux capabilities, it looks to me like we
> can indeed give hard-RT performance. Sure, it may mean not using
> broken 8390 drivers which globally disable interrupts while spending
> 1.6 ms reading a packet, but hey, we can live with that ;-)
I've been working on two things where hard real time is an important
matter. That is localtalk cards and dumb synchronous cards. The former
requires I hit 90uS or so worst case latency on receive, the latter to
do 2Mbits is even tighter.
> Being able to do all this with normal Linux without having to resort
> to RTLinux is a goal worthy of pursuit.
No argument ;)
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