FreeRTOS for Epiphany?

FreeRTOS for Epiphany?

Postby aolofsson » Tue Jan 08, 2013 11:16 am

We thought about an Epiphany port of FreeRTOS, but there were always other things that got in the way. Anyone interested in giving it a shot?
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Re: FreeRTOS for Epiphany?

Postby ed2k » Tue Jan 15, 2013 6:13 am

took a look at the website, wiki. seems it is featuring thread, mutex, semaphore, timers.
do we really want to run multi-task on the core? to me, a single run-to-complete model plus an interrupt handler is enough.
the big problem would be how to make use of the 1G cpu, while there is only 32K space.
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Re: FreeRTOS for Epiphany?

Postby piotr5 » Tue Jan 15, 2013 7:56 pm

what we need is some sort of re-location that can move code between on-core memory and the more general (slower) memory. i.e. we must simulate what in hardware is usually done by a processor-cache. I guess this means a program must be split into 32kb or better 16kb portions that get written onto the core's memory. imho that's the main purpose of an os, working together with the compiler to implement dynamic memory (as in swap-partition), but much more fine-grained than at a whole library-scale. such libraries like gmp must be split into modules that work independendly, each module under 16kb, and the main program must try to split its work-load so that it uses only one module at a time. ideally those modules would be only virtually split so that different modules can re-use the same code (which needs to be altered and otherwise prepared at runtime by such an os). same design-problem as with precompiled headers, which still noone managed to implement correctly...

however, once that is done, I suspect the os will still need multi-threading and such, somehow this is a similar problem as the scheduling involved in making sure the right modules are in memory at the right time.
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