Re: [TUHS] Lions book

[Warner Losh <imp@bsdimp.com>]

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On Fri, Jan 17, 2020 at 8:24 AM Larry McVoy <lm@mcvoy.com> wrote:

> On Fri, Jan 17, 2020 at 09:50:24AM -0500, Clem Cole wrote:
> > 6th Edition is clear and if you want to understand what it takes and how
> it
> > works, John's commentary it difficult to beat.
>
> It's a good starting point but it's pretty outdated.  I like to go on and
> on about how much I love the SunOS 4.x kernel but it is outdated as well.
>
> I wish there was a v6/SunOS like kernel that was as clean but had good
> support for SMP and NUMA and TCP offload (and probably a long list of
> other useful stuff I've forgotten).
>
> Teaching kids how a single threaded kernel works is cool but it's
> also misleading, the world has gotten a lot more complex.  And while
> the kernels of decades ago were clean and simple, I don't know of
> a kernel to point people to that has the clean code that SunOS had.
> Solaris isn't it, though it has some bright spots.  Linux is meh, it's
> better than nothing by a lot but I would not point to it as "read this,
> kid, you'll see the architecture".  It's not clear there is a good
> answer.
>

It's but the first step on the road to understanding. I'd been working on
the FreeBSD kernel for years when I re-read the Lions book. The stark
simplicity of the v6 kernel helped everything suddenly 'click' into place
in the code I was reading in the FreeBSD kernel, even with 30ish years of
changes to the v6 code base that lead to the FreeBSD kernel...

Newer systems are a lot more complicated. And they need to be to get the
full performance out of the system. Yet understanding the basics without
the extra clutter has great value.

Warner

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