In embedded design, what is the actual overhead of using a linux os vs programming directly against the cpu? [closed]

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I understand that the answer to this question, like most, is "it depends", but what I am looking for is not so much an answer as much as a rationale for the different things affecting the decision.

My use case is that I have an ARM Cortex A8 (TI AM335x) running an embedded device. My options are to use some embedded linux to take advantage of some prebuilt drivers and other things to make development faster, but my biggest concern for this project is the speed of the device. Memory and disk space are not much of a concern. I think it is a safe assumption that programming directly against the mpu and not using a full OS would certainly make the application faster, but gaining a 1 or 2 percent speedup is not worth the extra development time.

I imagine that the largest slowdowns are going to come from the kernel context switching and memory mapping but I do not have the knowledge to correctly assess or gauge the extent of those slowdowns. Any guidance would be greatly appreciated!

Answer 1

Your concerns are reasonable. Going bare metal can/will improve performance but it may only be a few percent improvement..."it depends".

Going bare metal for something that has fully functional drivers in linux but no fully functional drivers bare metal, will cost you development and possibly maintenance time, is it worth that to get the performance gain?

You have to ask yourself as well am I using the right platform, and/or am I using the right approach for whatever it is you want to do on that processor that you think or know is too slow. Are you sure you know where the bottleneck is? Are you sure your optimization is in the right place?

You have not provided any info that would give us a gut feel, so you have to go on your gut feel as to what path to take. A different embedded platform (pros and cons), bare metal or operating system. Linux or rtos or other. One programming language vs another, one peripheral vs another, and so on and so on. You wont actually know until you try each of these paths, but that can be and likely is cost and time prohibitive...

As far as the generic title question of os vs bare metal, the answer is "it depends". The differences can swing widely, from almost the same to hundreds to thousands of times faster on bare metal. But for any particular application/task/algorithm...it depends.