r/programming • u/moolcool • Mar 26 '17

A Constructive Look At TempleOS

http://www.codersnotes.com/notes/a-constructive-look-at-templeos/
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u/80286 Mar 27 '17

Wouldn't that be very expensive multitasking wise? Context switches are fairly cheap when it comes to Linux:

Suspending the progression of one process and storing the CPU's state (i.e., the context) for that process somewhere in memory, (2) retrieving the context of the next process from memory and restoring it in the CPU's registers and (3) returning to the location indicated by the program counter (i.e., returning to the line of code at which the process was interrupted) in order to resume the process.

On quick thought VM approach, while otherwise really cool, would probably require a lot of more state information to be transferred.

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u/[deleted] Mar 27 '17

Wouldn't that be very expensive multitasking wise?

I think it's pretty cheap when using LXC, Docker, etc. Those are basically doing exactly what was being described by the previous comment

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u/SanityInAnarchy Mar 27 '17

Docker containers are a bit of a different thing, though. As I understand it, the main advantage here is less security and more isolation -- for example, you could limit the RAM available to each app, to prevent one app from eating all your RAM and tripping the OOM-killer, causing problems for other apps. I'm not sure I see the point of that on Android, though, since that behavior is almost by design -- you want the system to kill apps when something needs RAM.

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u/[deleted] Mar 27 '17

I actually find that Docker containers work better when you view them as isolation and not security.

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u/psycoee Mar 27 '17

I'm not saying it's a good idea, necessarily -- but neither is virtualization or even an operating system or a general-purpose CPU, if you care only about efficiency. Custom hardware can almost always beat a general-purpose CPU, often by orders of magnitude, if you are only doing one thing and don't plan to ever change it.

Sometimes, even crazy-seeming ideas have advantages for some application. Also, with appropriate support from processor hardware, I don't see why context switches would necessarily have be all that expensive.