An immutable operating system
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An immutable operating system
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Re: An immutable operating system
#2I don't really know how feasible this is without pretty significant performance impact (esp. memory usage), but as a research project, it sounds fascinating. Go for it.
Re: An immutable operating system
#3I gave an un-conference talk at Clojure days Amsterdam called "Purely Functional OS" on this exact topic and we had an incredibly interesting discussion about the topic.
The conclusion we kept coming back to is that it's technically not all that difficult to implement, but that to make it usable in the real world would mean that computers would have to get a lot more cautious about source vs. derived data.
The main thing is that on the one hand it seems pretty feasible to store all meaningful data a user generates over the course of using a computer and building an immutable persistent OS on top of that.
On the other hand though, when you think about doing this in the context of an actual computer as in use today you will very quickly run out of storage space.
What is separating these two scenarios is that a lot of data is (deterministically) derived from source inputs, but in the current state of technology it's impossible to determine what is derived data which can be easily recomputed and what is essential data without which the current state could not be reached.
I happened to just be reading this article on unikernels which coincidentally is something that would help get us a bit further along in that direction: http://queue.acm.org/detail.cfm?id=2566628
P.S. When thinking about this one key concept is to realize that you could can do things like implement a 'torrent file system' where a file is just a torrent hash which can be requested and signal when (parts of it) become available.
Re: An immutable operating system
#4I'm not sure how this would look very different from current pure functional languages. Think about programming in Haskell. Everything is immutable but you can compile down to machine level binaries. So at some point the programmer is presented with an abstract immutable model and under the hood some runtime does real pointer arithmetic and all. Even garbage collectors could be optimized already for knowing that the programmer has no knowledge of memory locations.
If this kind of OS encourages hardware changes, that's one thing. But aside from performance, it probably won't look too different from current FP languages.
Re: An immutable operating system
#5I gave an un-conference talk at Clojure days Amsterdam called "Purely Functional OS" on this exact topic and we had an incredibly interesting discussion about the topic. The conclusion we kept coming back to is that it's technically not all that difficult to implement, but that to make it usable in the real world would mean that computers would have to get a lot more cautious about source vs. derived data. The main t…
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Re: An immutable operating system
#6An operating system whose main goal is not performance is forever going to be a toy of professors. Linux is a mess compared to the beautiful code that would comprise this OS, but it's a mess that runs fast on real hardware and let's people get stuff done. That matters.
Re: An immutable operating system
#7A garbage collector that knows that all values are immutable will be rather interesting, I think. Typically, a garbage collector will stop the world (i.e. halt execution) to do heap defragmentation of the old generation. When all values are immutable, though, you can defragment the heap by copying a value to another fragment and just swap the internal pointer to the value.
This might actually have significant performance benefits. When everything is immutable, GC can also be inherently incremental. You just do your defrag copy faster than new object creation. Then you cam limit your stop-the-world to a small "catch-up" so your copy-from can become a copy-to. Incremental GC nirvana!
Re: An immutable operating system
#8An operating system whose main goal is not performance is forever going to be a toy of professors. Linux is a mess compared to the beautiful code that would comprise this OS, but it's a mess that runs fast on real hardware and let's people get stuff done. That matters.
That doesn't really matter if the idea is to experiment.
Re: An immutable operating system
#9You mention that one of the benefits would be that memory can be shared across processes without any defensive copying or protection semantics, but isn't the entire idea that immutable values are a special type of defensive copying and protection semantic?
I imagine that this would be useful if doing many calculations on readonly values, but would take a performance hit for readwrite operations.
I'm not one for purely functional programming, but this seems like an interesting concept. I'm interested to see where it goes
Re: An immutable operating system
#10An operating system whose main goal is not performance is forever going to be a toy of professors. Linux is a mess compared to the beautiful code that would comprise this OS, but it's a mess that runs fast on real hardware and let's people get stuff done. That matters.
As I mentioned elsewhere, such an OS could have important performance benefits. GC could be made to be incremental at a fundamentally new level. In fact, incremental GC could be nothing more than a series of defrag copies that proceed at a rate just faster than new object creation. Such a system would rock for writing real-time systems.