[TUHS] Code bloat (was: How Unix brings people together, or it's a small...)

Nick Downing downing.nick at gmail.com
Wed Feb 8 21:21:36 AEST 2017


Yes, NetBSD and 386BSD are interesting. They could well form a good
basis for a minimal but fully functional OS for a modern platform. One
reservation I have though, is as follows: When 386BSD and its
derivatives like OpenBSD, NetBSD, FreeBSD came out, Unix was still
encumbered and thus they had to be based on 4.4BSD Lite (not even
NET/2 was safe). Nobody made an unencumbered version of say 4.3BSD or
even NET/2, even though it was theoretically possible, by examining
what had to be taken out/added to produce 4.4BSD Lite.

Given that Unix is now unencumbered I believe there is no point
adopting 4.4, or even 4.3Reno, because the main thing done in those
releases as far as I know, is to add partial POSIX compliance. But if
you want POSIX compliance you will not achieve minimality. As an
example consider the BSD sigvec() routine. POSIX calls this
sigaction(), the old SV_ONSTACK flag becomes SA_ONSTACK, the old
integer mask becomes a sigset_t and so on... and in any reasonable
POSIX compliant BSD the two calls are gonna have to coexist, etc.

As to 32V, I appreciate your idea, as I was having some similar
thoughts myself. However I personally wouldn't use 32V as a basis for
any serious porting work, because I would assume V7 and 4.3 are much
more stable and well tested, since they ran in a lot of installations
over a long time. That's not to denigrate the huge achievement in
porting V7 to the VAX and producing 32V, but it probably has some
rough edges that were smoothed out over time to produce the 4BSDs. The
situation is a bit different for kernel/toolchain/other userspace.

As to the kernel I have been trying to make a detailed comparison
between 32V and the BSDs, but have been a bit put off by the fact that
all files moved around and may have been renamed, I will figure it all
out eventually though. As to the toolchain I have compared it quite
carefully with 4.3BSD, and I conclude you should use the later
toolchain as there is no disadvantage and some advantages to doing so.
As to the rest of the userspace, I BELIEVE that it's stock V7 with any
32-bit issues fixed, but I suspect somewhat hastily and superficially.

Producing a 32V-like kernel from 4.3BSD sources would probably be
quite difficult, it would be relatively easy to disable added system
calls, but harder to disable things like setpgrp() or the associated
support in the TTY drivers. More seriously the memory management would
have to change, I am planning however to make virtual memory optional
in the 4.3BSD kernel, by maybe putting the 32V code back in, protected
by #ifndef VM or some such (somewhat like Steven Schultz has done in
porting 4.3BSD to PDP-11 to produce 2.11BSD).

On the other hand producing a 32V-like userland from the 4.3BSD
sources would be pretty easy, I think just delete the sources for any
executables that weren't distributed with 32V and possibly, if any of
the tools seem particularly bloated, comment out any command line
switches or features that weren't in 32V. Going to this level of
effort would likely be pointless though. Another option would be
taking V7 and re-porting it (except the toolchain) over to a 32-bit
environment and kernel. I have developed over the past months, tools
that make this relatively straightforward, and in the process would
rediscover any 32-bit issues that were fixed in creating 32V. So I
wouldn't use 32V.

On a slightly different tack, I also have been for some time
investigating the idea of an Apple II port of Unix, there are massive
technical issues to be solved, but I think I got a bit closer the
other night when I decided to collect all information and resources I
could find about Mini-Unix and LSX (LSI Unix). Both are
self-supporting V6-based environments, the compiler can only compile
small programs but it is nonetheless possible for each Unix to
recomple itself. LSX I believe could run from floppies (dunno about
140K floppies) in less than 64K.

So, you know, true minimality is a relative term. We want something
LSX-like for an Apple II, something 2.11BSD-like for an IBM PC/XT or
286 (as Peter Jeremy noted, it's a good fit, and I'd be interested to
know more), something 4.3BSD-like for a VAX or 386... something a bit
more fully featured for a modern 64-bit multi-gigabyte system... but
just not as bloated as what we currently rely on. Hmm well it's hard.
What I do know, is that I have a lot of old hardware with <16M RAM and
Linux won't run on it anymore, and this annoys me very greatly.

In talking about FreeBSD/Linux bloat I forgot to mention the packet
filter, iptables (Linux) or pf (FreeBSD). I have a bit of experience
with this, since I regularly used to put 2 Ethernet cards in my home
server and make it Internet facing through one of them and share the
connection using NAT through the other card. But I've come to the
conclusion this is stupid, and moreover, that putting a complete
mini-language into the kernel just for this purpose is utterly stupid.
Programming the thing from userspace is incredibly intricate, and all
this complexity serves no purpose.

I recently found out about SLIRP (userspace packet rewriting) and I
think this would be a good way to implement NAT on servers or routers
that actually need to do NAT -- just make a userspace process that
runs something SLIRP-like and has a raw socket to the second Ethernet
card, and Bob's your uncle.

But this got me thinking along pretty productive lines in terms of the
tiny Apple II port -- I have been wanting to put the 2.11BSD network
stack into an Apple II for a long time, but I've now realized this is
not necessary. A much better approach for those Mini-Unix or LSX or
even V7 systems, would be to have a userspace library that does SLIP
and contains its own TCP, UDP, IP drivers, resolver and so on. Then if
you run a userspace program like say, ftp, which is linked to the
userspace TCP library, it would basically just open /dev/ttyXX, bring
up the SLIP link itself, do any necessary downloads etc, then close
the TTY and stop responding to any IP stuff coming over the SLIP link
whilst you quit to the prompt, until another program reopens it.

cheers, Nick

On Wed, Feb 8, 2017 at 2:56 PM, Jason Stevens
<jsteve at superglobalmegacorp.com> wrote:
> What about NetBSD 1.1 or even 386BSD?
>
> There never was a 4.2 or 4.3 for i386 was there?
>
> I'd guess the 32v userland could be built on early 4.4BSD Lite/NET2 greatly
> reducing its footprint.
>
>
>
>
> On February 8, 2017 11:47:03 AM GMT+08:00, Nick Downing
> <downing.nick at gmail.com> wrote:
>>
>> This is an issue that interests me quite a bit, since I was running
>> FreeBSD in an effort to get around Linux bloat problems discussed.
>> Well not that I really mind Linux as a user interface / runtime
>> environment / main development machine, but I think it probably
>> shouldn't be used as a "least common denominator" for development
>> since you end up introducing unwanted dependencies on a whole lot of
>> stuff.
>>
>> So I was running FreeBSD as a more minimal *nix. I did quite a lot of
>> interesting stuff with FreeBSD such as setting up diskless
>> workstations in my home, etc. I spent a lot of time tinkering around
>> in the kernel code. I was planning to do some serious development on
>> 4.4BSDLite or FreeBSD to create an operating system more to my liking.
>> So, I was looking carefully at differences since ancient *nixes.
>>
>> And, I can say that FreeBSD is pretty bloated. Umm well they've added
>> SMP, at the time it was using the Giant Lock although that could be
>> fixed by now. They've added VFS and NFS of course. They've added an
>> entire subsystem for block devices IIRC that handles partitioning and
>> possibly some other sophisticated stuff, which I believe is their own
>> design. Umm the kqueues and I believe they have their own
>> implementation of kernel threading or lightweight processes including
>> some sort of idle daemon. The network stack is heavily upgraded, to
>> the extent I looked into it, the added features are things you would
>> want (syncookies = DOS protection, etc) but also could not possibly be
>> called minimal, and would preclude running it on other than a
>> multi-megabyte machine. They have multiple ABIs so the kernel can
>> accept Linux or BSD syscalls or whatever else (I used it to run
>> Acrobat Reader Linux on my FreeBSD desktop). Umm I am pretty sure they
>> have kernel modules ala Linux. Lots and lots and lots of stuff... and
>> that's only considering the kernel. If you look in the ports
>> collection you see they have incredible amounts of bloat there too...
>> for instance GNOME, Libreoffice, LATEX, gcc, python... not that I'm
>> denigrating these tools, since they do invaluable work and I use them
>> every day, but the point is, you CANNOT call them minimal.
>>
>> The quest for a clean minimal system goes on ->. FreeBSD is not the
>> answer. In fact I believe 4.3BSD-Reno and 4.4 go strongly offtrack.
>>
>> cheers, Nick
>>
>> On Wed, Feb 8, 2017 at 1:55 PM, Greg 'groggy' Lehey <grog at lemis.com>
>> wrote:
>>>
>>>  On Tuesday,  7 February 2017 at 15:38:40 -0800, Steve Johnson wrote:
>>>>
>>>>  Looking back, the social dynamics of the Unix group helped a lot in
>>>>  keeping the bloat small.   The rule was, whoever touches something
>>>>  last becomes its owner.  Of course, we were all free to complain
>>>>  about things, and did, but the amalgamation of tinkerings that
>>>>  characterizes most of the Linux commands just didn't happen.
>>>
>>>
>>>  Out of interest: where do you (or others) consider that the current
>>>  BSD projects it in this comparison?
>>>
>>>  Greg
>>>  --
>>>  Sent from my desktop computer.
>>>  Finger grog at lemis.com for PGP public key.
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>
>
> --
> Sent from my Android device with K-9 Mail. Please excuse my brevity.


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