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Comment by cosinetau | Hacker News Reader

This was a very interesting point. It sounds like there are some serious architectural limitations on Windows, and this makes me believe the same might be true for the NT kernel, and that MS might not be interested in doing heavy refactoring of it.

I'm not a frequent Windows user, or a Windows dev at all. Does anyone know of any consequences that MS's decision might mean, if this hypothesis is true?

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The NT kernel is surprisingly small and well-factored to begin with - it is a lot closer to a 'pure' philosophy (e.g. Microkernel) than something like Linux to begin with.

If you have a problem with Windows being overcomplicated or in need of refactor it is almost certainly something to do with not-the-kernel.

If you look at something like the Linux kernel its actually much larger than Windows. It needs to have every device driver known to man (except that one WiFi/GPU/Ethernet/Bluetooth driver you need) because internally the architecture is not cleanly defined and kernel changes also involve fixing all the broken drivers.

Yes! Windows Kernel is a much more "modern" microkernel architecture than any of the circa-1969 Unix-like architectures popular today. We use Windows 10 / Windows Serve for everything at our company, and we have millions of simultaneously connected users on single boxes. No problems and easy to manage.

Could you please share a link to NT kernel sources so that I take a look?

It is not true that internal architecture of Linux drivers is not clearly defined. It is just a practical approach to maintenance of drivers (as an author of one Linux hardware driver I'm pretty sure the best possible). Reasoning is outlined in famous "Stable API nonsense" document http://elixir.free-electrons.com/linux/latest/source/Documen...

I don't think Windows approach is worth praising here. It results in a lot of drivers stopping working after few major Windows release upgrades. In Linux, available drivers can be maintained forever.

If you are sufficiently motivated, NT 4 leaked many years ago and you could find it; it even has interesting things like DEC Alpha support & various subsystems still included IIRC. Perhaps you could find a newer version like 5.2 on GitHub or another site, but beware, as a Linux dev/contributor, you probably don't want to have access to that.

FWIW, I've stumbled upon both of those things in my personal research while I had legitimate access to the 5.2 sources as a student. It turns out Bing will link you directly to the Windows source code if you search for <arcane MASM directive here>.

Yes, I'm in the process of reporting this to Microsoft and cleansing myself of that poison apple.

Small and well-factored the core kernel may be, but if you're parsing fonts in kernel mode, you ain't a microkernel.

( https://googleprojectzero.blogspot.com.au/2015/07/one-font-v... )

For sure, and Windows is not a microkernel, but it does have separated kernel-in-kernel and executive layers; it would approach being a microkernel architecture if the executive was moved into userland. This is similar to how macOS would be a microkernel, if everything wasn't run in kernel mode (mach, on which it is partially based, is a microkernel).

Of course the issue here is that after NT 4, GDI has been in kernel mode; this is necessary for performance reasons. Prior to that it was a part of the user mode Windows subsystem.

I'd be curious to see if GDI moved back to userland would be acceptable with modern hardware, but I suspect MS is not interested in that level of churn for minimal gain.

It seems presumptive to say that "If you can't use multiple repos, your architecture must be bad". I could just as easily counter with, "If you're using multiple repos, it must mean you have an unnecessarily complex and fragile microservice architecture"

I'm sorry that was implied. I simply want better insight into the kernel from people who have experience developing large kernels, and the decisions that are made as a consequence of architectural choices.

I feel like that those questions are valid, and are important in this field, not just kernel development. As someone who desires to continue learning, I will not yield to your counter.

Google also uses a single giant repo...

And Facebook.

Why is that a "good reason" to do it?

Not really :) and I am not the OP. This article [1] provides a very good overview of the repository organization Google has and the reasons behind it.

I think the reason that this works for well Google is the amount of test automation that is in place which seems to be very good at flagging any errors due to dependency changes before it gets deployed. Not sure how many organizations have invested and have an automated test infrastructure like Google has built.

1. https://cacm.acm.org/magazines/2016/7/204032-why-google-stor...

I think this is like the "your data isn't big enough for HDFS" argument earlier this week. The point I take away is that at some stage of your growth, this will be a logical decision. I don't think it implies that the same model works for your organization.

It radically simplifies everything. Every commit is reproducible across the entire tool chain and ecosystem.

It makes the entire system kind of pure-functional and stateless/predictable. Everything from computing which tests you need to run, to who to blame when something breaks, to caching build artifacts, or even sharing workspaces with co-workers.

While this could be implemented with multiple repros underneath, it would add much complexity.

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