I completely agree. Studying and >>learning<< from V6 allows you to
consider the basics of what any good OS, no just a UNIX-like system, has to
do provide simple but complete services. Examining V6 not most of the
things you find today removes a lot of the noise, like threading, parallel
execution, vm, networking, which are fine topics for later, but Warner is
right - get a solid understanding first. It also helps to understand what
makes 'UNIX-ness' and why it was different from anything before it came on
BTW: It' why I still like Pascal (Delphi) over C or C++ as a first language
(I admit, I'm leaning towards Go these days, but Go lacks a good teaching
text). This is what I heard Doug saying. IMO: Lion's book and the V6,
can be considered 'old' by contemporary standards, but they are still 100%
appropriate and because the book and code is so simple, the teacher and the
student can focus on what really matters (*i.e.* learning to walk carefully
in a directed manner and get to your destination before you are forced to
run with the bulls and avoid getting run over).
On Fri, Jan 17, 2020 at 11:01 AM Warner Losh <imp(a)bsdimp.com> wrote:
On Fri, Jan 17, 2020 at 8:24 AM Larry McVoy <lm(a)mcvoy.com> wrote:
On Fri, Jan 17, 2020 at 09:50:24AM -0500, Clem
6th Edition is clear and if you want to
understand what it takes and
works, John's commentary it difficult to
It's a good starting point but it's pretty outdated.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on about how much I love the SunOS 4.x kernel but it is outdated as well.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
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.