Comment by bcg1 | Hacker News Reader

Comment by bcg1 | Hacker News Reader

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This is definitely a developing trend... seems to be catching on that most server applications are more or less single programs that just use the OS as an emulation layer so that applications don't need to come with their own low level drivers. Quite overkill if you're just trying to run java, node, ruby, whatever

We're probably not too far off from java-as-the-os, node-as-the-os, etc. Substituting a hypervisor for Linux or whatever other OS you're using as the emulation layer seems to the be the architecture of choice for this type of work right now... I guess because you'd just have to implement a handful of drivers... in addition to other OS bits like scheduling and memory of course, but I suspect those things are fairly straightforward for many applications especially if you can assume that there are no other "processes" running... essentially those just become implementation details of the application that can be swapped in and out like any other library/framework

The term I've seen for this sort of architecture is a "unikernel"

This OSv project looks nice, definitely something to keep on the radar

I wouldn't really call OSv a unikernel. The main distinction is that in unikernel operating systems, the application IS the kernel. The OS is not an emulation layer, but the application itself. Application code is linked directly with the kernel to produce an operating system whose purpose is to execute a single application. One example is Mirage[0].

The big difference is that while OSv may be targeting the same use case, it's still more similar to a general purpose OS. Some of the kernel APIs it provides seem to be blurring the line though.

[0] http://openmirage.org/

OSv is not a general purpose OS although it does support a subset of the Linux ABI for compatibility. Both application and OSv share the same address space and application code is linked directly to the kernel at start-up (there's an embedded ELF linker). The design is wildly different from MirageOS but I don't really see why you would not call it an unikernel.

It seems like I didn't call it a unikernel because I misunderstood the design. The design you described sounds like a unikernel to me.

I'm kind of infatuated with the unikernel / libraryOS concepts. I think they're really on to something, especially when you consider how many systems are devoted purely to a single configuration and set of processes for large periods of time.

Some time ago, I listened to a talk given by one of the OpenMirage devs where he described substantial memory & complexity reductions and subsequent efficiency gains they were able to achieve compared to a comparable existing Unix System.

Moreover, after thinking about this for a while (and having a lot of experience working on embedded systems) I'm fairly confident there are still more opportunities for optimisation by removing ubiquitous but now actually unneeded layers of abstraction.

Fair enough, I agree your definition of a unikernel and OSv isn't that exactly.

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