this post was submitted on 14 Feb 2024
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Using a file system is much less bad than dynamically allocating memory, at least as long as you keep a predefined set of files.
I hate to alarm you but... What is a file system except dynamically allocated memory. ;)
It's a persistent dynamic memory allocation that's accessed by multiple processes! :)
multiple processes?!
FreeRTOS tasks are basically processes, IIRC other rtoses have similar mechanics too
If you want to get really freaky, try accessing the same flash or RAM from multiple instances of FreeRTOS running on a hypervisor.
Is that just like the shared memory model of parallel computing or are there any added complications? Have you done this before? Please do share your experiences if so cause now I'm interested :p
It's similar, but the general idea of a hypervisor is to separate resources and avoid this exact situation (it's nuanced and there are some exceptions, but that's the general use case).
The added complication would be that when you compile a binary for one virtual machine, the compiler may optimize things, blissfully unaware that there are other players possibly affecting memory. In a typical multithreaded environment, the compiler has a better picture of how shared resources are being used across threads, but that has to be declared manually for a hypervisor. So if you configure your hypervisor to share resources, you have to be even more vigilant in configuring the individual compilers to play nice.
I don't have a ton of experience with embedded hypervisors, though. And it's worth noting that there are lots of "hypervisors" out there, and some work very differently from others.
Lots of microcontrollers have multiple cores now.
And indeed, with memory mapped files the distinction almost disappears completely.
...with predefined sizes located in predefined regions of storage.
Yeah, that's what I was implying, just didn't want to write a whole novel about it.