Re:Arm Announces Cortex-R82: First 64-Bit Real Time Processor
by AnimalMuppet on Monday September 07, 2020 @11:32PM
(#24404974)
> realtime OS won't do much preemption, probably would rather stick to cooperative scheduling.
I've seen realtime OSes that were very preemptive, at least between priorities. Tasks/processes had priorities, and a higher-priority task that became active would preempt anything lower-priority that was running. vxWorks ran this way, IIRC, and it wasn't alone.
A realtime OS won't do much preemption, probably would rather stick to cooperative scheduling.
On the hardware side, explicit cache controls are big in realtime chips. Your programmers know exactly which data is in cache and what isn't, and therefore can accurately plan how long tasks take.
The MMU traditionally wasn't realtime. I wonder how they managed to get realtime controls with virtual memory. (They must have some kind of guarantee on TLB lookups or something)