5 ms·

> By the way, you wouldn't find any routers running a meger 512KB of RAM. This is not true in general, although true for modern devices. There are older router

> By the way, you wouldn't find any routers running a meger 512KB of RAM. This is not true in general, although true for modern devices. There are older router models that cannot run linux. A few years back I unsuccessfully tried to flash a very minimal <1 MiB linux on an old TP link router. I was able to flash the rom but I couldn't boot, because there was not enough memory available, it wasn't 512KB but only a few MiB IIRC, still not enough. > We are just pointing out that you massively misunderstand how micro kernels work If someone points out, that linux kernel can be reduced in size and that there are some big microkernels, then I do agree and there is no misunderstanding, as far as I can see. Same holds true for the performance argument. > As the GP said, micro kernels have a performance overhead swapping data between rings. I agree that performance will be problematic, but this does not render microkernels useless in general for constrained devices. See for example: https://technik.community/2014/07/micro-kernel-the-best-choice-for-embedded-systems/ https://technik.community/2014/07/micro-kernel-the-best-choi... https://www.scirp.org/html/3-9301550_27477.htm https://www.scirp.org/html/3-9301550_27477.htm

hnlmorg 6y ago
> This is not true in general. There are older models that which cannot run linux. A few years back I uncessfully tried to flash a very minimal <1 MiB linux on an old TP link router. I was able to flash the rom but I couldn't boot, because there was not enough memory available. How long ago was "a few years ago"? What model number was that? DD-WRT has been ported to the Archer series but if you're talking a ZyNOS based router then you're probably out of luck. Those ZyNOS devices are the real bottom end of the market though. Even the ISP routers here in the UK are generally a step up from those. Particularly these days now that households have an expectation to have kids playing online games, streaming Netflix and such like (even before COVID-19 hit ISPs have been banging on for ages about how their routers allow you to do more concurrently). And with TP-Link, the Archer series are all Linux based or Linux compatible and they start from ~£50. So you'd be really scraping the barrel to find something that wasn't these days. > I agree that perfromance will be problematic, but this does not render microkernels useless in general for constrained devices. Any OS designed around kernels, memory safety etc would be useless in general for constrained devices. This isn't an exclusively Linux problem. On such systems the whole design of how software is written and executes is fundamentally different. You don't have an OS that manages processes nor hardware, you write your code for the hardware and the whole thing runs bare metal as only one monolithic blob (or calls out to other discrete devices running their own discrete firmware like a circuit). That's how the N64 works, it's how embedded devices work. It's not how modern routers work. In 2020 it's hard to think of a time before operating systems but really that is the way how the N64 works. Anything you run on there will eat up a massive chunk of resources if it's expected to stay in memory. So you might as well go with a tiny monolithic kernel and thus shave a few instructions from memory protection and symbol loading (not to mention the marginally smaller binary sizes due to any file system metadata, binary file format overhead and other pre-logic initialisation overhead (such as you get when compiling software rather than writing it in assembly). If you're going to those lengths though laumars point kicks in: you're better off just writing a "bootloader" menu screen rather than a resident OS.
- tutfbhuf 6y ago
  > How long ago was "a few years ago"? What model number was that? DD-WRT has been ported to the Archer series but if you're talking a ZyNOS based router then you're probably out of luck. Those ZyNOS devices are the real bottom end of the market though. This brings back memories :) http://www.ixo.de/info/zyxel_uclinux/ http://www.ixo.de/info/zyxel_uclinux/ Sure, we are talking about low-end (real bottom) devices and date models here. I cannot recall the model number, but I think we both agree that routers that cannot run linux exist, although not very common (anymore). > Any OS designed around kernels, memory safety etc would be useless in general for constrained devices. How about QNX then? "QNX is a commercial Unix-like real-time operating system, aimed primarily at the embedded systems market. QNX was one of the first commercially successful microkernel operating systems. As of 2020, it is used in a variety of devices including cars and mobile phones." - https://en.wikipedia.org/wiki/QNX https://en.wikipedia.org/wiki/QNX They are "aimed primarily at the embedded systems market", their latest release is from "7.1 / July 2020; 5 months ago" and they are operating their business model since 1982.
  - hnlmorg 6y ago
    > This brings back memories :) http://www.ixo.de/info/zyxel_uclinux/ http://www.ixo.de/info/zyxel_uclinux/ Sure, we are talking about low-end (real bottom) devices here. So not just low-end, but a decade old device that was already low-end upon it's release. That's hardly a fair argument to bring to the discussion. > How about QNX then? QNX wouldn't run on something with <1MB RAM. Nothing POSIX compliant would* . The published minimum requirements for Neutrino 6.5 (which is already 10 years old) was 512MB. Double that if you want the recommended hardware specification. Sure, if you want to strip out graphics libraries and all the other stuff and just run it as a hypervisor for your own code you could get those hardware requirements right down. But then you're not left with something POSIX compliant, not even useful for the N64. And frankly you could still get a smaller footprint by rolling your own. The selling point of QNX is a RT kernel, security by design and a common base for a variety of industry hardware. But if you're writing something for the N64 then none of those concerns are relevant (and my earlier point about a resident OS for the N64 being redundant is still equally valid for QNX). Also smart phones are neither embedded nor "constrained" devices. I have no idea what the computing hardware is like in your average car but I'd wager it varies massively by manufacturer and model. I'd also wager QNX isn't installed on every make and model of car either. * I should caveat that by saying, yes it's possible to write something partially POSIX compliant which could target really small devices. There might even be a "UNIX" for the C64. But it's a technical exercise, like this N64 port of Linux. It's not a practical usable OS. Which is the real crux of what we're getting at.
deleted 6y ago
[deleted]

hnlmorg 6y ago

> This is not true in general. There are older models that which cannot run linux. A few years back I uncessfully tried to flash a very minimal <1 MiB linux on an old TP link router. I was able to flash the rom but I couldn't boot, because there was not enough memory available. How long ago was "a few years ago"? What model number was that? DD-WRT has been ported to the Archer series but if you're talking a ZyNOS based router then you're probably out of luck. Those ZyNOS devices are the real bottom end of the market though. Even the ISP routers here in the UK are generally a step up from those. Particularly these days now that households have an expectation to have kids playing online games, streaming Netflix and such like (even before COVID-19 hit ISPs have been banging on for ages about how their routers allow you to do more concurrently). And with TP-Link, the Archer series are all Linux based or Linux compatible and they start from ~£50. So you'd be really scraping the barrel to find something that wasn't these days. > I agree that perfromance will be problematic, but this does not render microkernels useless in general for constrained devices. Any OS designed around kernels, memory safety etc would be useless in general for constrained devices. This isn't an exclusively Linux problem. On such systems the whole design of how software is written and executes is fundamentally different. You don't have an OS that manages processes nor hardware, you write your code for the hardware and the whole thing runs bare metal as only one monolithic blob (or calls out to other discrete devices running their own discrete firmware like a circuit). That's how the N64 works, it's how embedded devices work. It's not how modern routers work. In 2020 it's hard to think of a time before operating systems but really that is the way how the N64 works. Anything you run on there will eat up a massive chunk of resources if it's expected to stay in memory. So you might as well go with a tiny monolithic kernel and thus shave a few instructions from memory protection and symbol loading (not to mention the marginally smaller binary sizes due to any file system metadata, binary file format overhead and other pre-logic initialisation overhead (such as you get when compiling software rather than writing it in assembly). If you're going to those lengths though laumars point kicks in: you're better off just writing a "bootloader" menu screen rather than a resident OS.

tutfbhuf 6y ago
> How long ago was "a few years ago"? What model number was that? DD-WRT has been ported to the Archer series but if you're talking a ZyNOS based router then you're probably out of luck. Those ZyNOS devices are the real bottom end of the market though. This brings back memories :) http://www.ixo.de/info/zyxel_uclinux/ http://www.ixo.de/info/zyxel_uclinux/ Sure, we are talking about low-end (real bottom) devices and date models here. I cannot recall the model number, but I think we both agree that routers that cannot run linux exist, although not very common (anymore). > Any OS designed around kernels, memory safety etc would be useless in general for constrained devices. How about QNX then? "QNX is a commercial Unix-like real-time operating system, aimed primarily at the embedded systems market. QNX was one of the first commercially successful microkernel operating systems. As of 2020, it is used in a variety of devices including cars and mobile phones." - https://en.wikipedia.org/wiki/QNX https://en.wikipedia.org/wiki/QNX They are "aimed primarily at the embedded systems market", their latest release is from "7.1 / July 2020; 5 months ago" and they are operating their business model since 1982.
- hnlmorg 6y ago
  > This brings back memories :) http://www.ixo.de/info/zyxel_uclinux/ http://www.ixo.de/info/zyxel_uclinux/ Sure, we are talking about low-end (real bottom) devices here. So not just low-end, but a decade old device that was already low-end upon it's release. That's hardly a fair argument to bring to the discussion. > How about QNX then? QNX wouldn't run on something with <1MB RAM. Nothing POSIX compliant would* . The published minimum requirements for Neutrino 6.5 (which is already 10 years old) was 512MB. Double that if you want the recommended hardware specification. Sure, if you want to strip out graphics libraries and all the other stuff and just run it as a hypervisor for your own code you could get those hardware requirements right down. But then you're not left with something POSIX compliant, not even useful for the N64. And frankly you could still get a smaller footprint by rolling your own. The selling point of QNX is a RT kernel, security by design and a common base for a variety of industry hardware. But if you're writing something for the N64 then none of those concerns are relevant (and my earlier point about a resident OS for the N64 being redundant is still equally valid for QNX). Also smart phones are neither embedded nor "constrained" devices. I have no idea what the computing hardware is like in your average car but I'd wager it varies massively by manufacturer and model. I'd also wager QNX isn't installed on every make and model of car either. * I should caveat that by saying, yes it's possible to write something partially POSIX compliant which could target really small devices. There might even be a "UNIX" for the C64. But it's a technical exercise, like this N64 port of Linux. It's not a practical usable OS. Which is the real crux of what we're getting at.

deleted 6y ago

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