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Sometimes I want to call malloc, just as a treat (lemmy.world)

submitted 9 months ago by verysuchaccount@lemmy.world to c/programmer_humor@programming.dev

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[-] bus_factor@lemmy.world 28 points 9 months ago

Using a file system is much less bad than dynamically allocating memory, at least as long as you keep a predefined set of files.

[-] troyunrau@lemmy.ca 36 points 9 months ago

I hate to alarm you but... What is a file system except dynamically allocated memory. ;)

[-] Redkey@programming.dev 30 points 9 months ago

It's a persistent dynamic memory allocation that's accessed by multiple processes! :)

[-] bort@feddit.de 45 points 9 months ago* (last edited 9 months ago)

multiple processes?!

[-] noli@programming.dev 8 points 9 months ago

FreeRTOS tasks are basically processes, IIRC other rtoses have similar mechanics too

[-] owenfromcanada@lemmy.world 4 points 9 months ago

If you want to get really freaky, try accessing the same flash or RAM from multiple instances of FreeRTOS running on a hypervisor.

[-] noli@programming.dev 3 points 9 months ago

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

[-] owenfromcanada@lemmy.world 3 points 9 months ago

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.