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-- BTW.: what are the cons to _always_ using the realtime extensions ?
With realtime, if you have realtimer threads running always, other standard threads will never run and you will have the impress that your system is frozen if you interact with him with normal program. In fact not..
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I understand that this is true with a standard system, independent of the Kernel configuration, as well: If you start a process or thread and assign a realtime Prioridy (SCHED_FIFO or SCHED_RR) to it, and this process or thread never goes to sleep on it's own, all "normal" user process will hang. forever.
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One I have loaded my system with "stress -i 20 -c 20" (40 process), the max latency is about 800 µs.
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This does sound very good. But did you find that the overall Kernel performance (for time shared work) significantly degrades (with no realtime process running) ?
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For atomic operations, interrupts are disabled (it is done in the same manner with processor without atomic instructions). Just a cost in terms of latency.
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I see. With the actual NIOS "hardware" there seems not to be another way to go. :( unfortunately this will not be possible with a future SMP implementation :( .
-Michael
Honored Contributor
