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>From ncrgw1!cse.psu.edu!9fans Wed Apr  5 08:20 EDT 1995 remote from ncrhub4
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From:	forsyth@plan9.cs.york.ac.uk
Date:	Wed, 5 Apr 1995 06:15:10 -0400
To:	9fans@cse.psu.edu
subject: plan 9 and linux
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>>How is it compared to Linux?

apples and galaxies.

they do different things.  linux is a self-contained operating
system that can attach to a network.  plan 9 really is a distributed system.

Linux now seems to attempt to track Posix closely, with all that that entails.  
by contrast, although plan 9 has useful ansi/posix emulation environments --
and that's certainly convenient when importing or exporting Unix programs --
it's definitely not the most sensible way of using plan 9.
it isn't a `leaner unix'.  indeed, if you approach it that way,
you will probably be disappointed.

plan 9 provides a number of components that can be put together on a network to form
one (secure, distributed) computing system;  even an apparently `standalone'
plan 9 system at home can link itself smoothly to the name space --
and thus processors, devices and network interfaces -- of a bigger system.

although linux does very well -- the leanest and most effective
unix-like system on a PC -- in my experience, plan 9 easily is less demanding of hardware than
other general purpose operating systems on any given platform.

for instance, at work my terminal is a 386sx/16 with 4mbytes
with an ET4000 ISA graphics card and NE2000 card.  i have a small slow
seagate IDE disc for booting & paging, but it doesn't page much.
at the moment this pathetic machine is running 30 processes
including the window system 8B=, seemail, `cpu' to the cpu server
samterm (to remote sam on the CPU server), a local 8B= window for commands,
dossrv (makes DOS file systems on disc & floppy visible in the plan 9 name space),
and supporting commands (eg, kernel protocol processes, exportfs exporting
the terminal's name space to the cpu server).  (by the way, i can access
the terminal's diskette device and/or DOS file system transparently
from the cpu server, just as i access the terminal's keyboard, mouse and screen.)

here is a ps:

forsyth       1    0:00   0:00    40K Wait     init
bootes        2    0:00   0:00     0K Wakeme   alarm
bootes        3    0:06   0:00     0K Wakeme   ether0kproc
bootes        4    0:00   0:00     0K Wakeme   tcpack
bootes        5    0:00   0:00     0K Wakeme   tcpflow
bootes        7    0:00   0:00     0K Wakeme   ilack
forsyth       8    0:00   0:00     0K Idle     pager
forsyth       9    0:08   0:25   352K Read     8B=
forsyth      13    0:01   0:02    48K Read     cs
forsyth      17    0:00   0:00     0K Wakeme   floppy
forsyth      23    0:00   0:00   704K Read     dossrv
forsyth      26    0:00   0:00    40K Read     arpd
forsyth      28    0:00   0:00     0K Wakeme   uart0
forsyth      36    0:00   0:01   196K Read     8B=
forsyth      38    0:00   0:01   196K Read     8B=
forsyth      47    0:00   0:00   132K Read     samterm
forsyth      49    0:00   0:00    20K Read     rx
forsyth      52    0:00   0:00   124K Read     samterm
forsyth      53    0:00   0:01   124K Read     samterm
forsyth      54    0:00   0:00   124K Read     samterm
forsyth      55    0:00   0:00   124K Read     samterm
forsyth      58    0:00   0:00    20K Read     rx
forsyth      59    0:00   0:00   108K Read     seemail
forsyth      65    0:00   0:00    28K Wait     cpu
forsyth      66    0:00   0:01   332K Read     exportfs
forsyth      67    0:00   0:00   332K Rendez   exportfs
forsyth      68    0:00   0:00   332K Read     exportfs
forsyth      70    0:00   0:00   104K Wait     rc
forsyth      75    0:00   0:00    32K Read     ps

is it paging frantically?

term% cat /dev/swap
374/416 memory 92/4000 swap

no: in fact the pager is currently idle.  presumably it has turfed out
most of dossrv since i'm not using it.  (the memory sizes above
can't just be added up: there's a lot of shared text & data there.)

now, you definitely don't want to compile much on this thing -- for one
thing it hasn't got a floating-point unit -- and it's certainly not
as snappy as a bigger 486 at home with more memory and a reasonable graphics card.
nevertheless: try getting an X server to run on a similar configuration
with several xterms, rlogins (inadequate substitute for `cpu'), a mail monitoring
window, and samterm.  it's certainly true that you'll stand the best
chance of doing it with linux, though, compared (say) to solaris/486.

although i haven't made a complete study of linux,
i'd say the system interfaces in the plan 9 cpu/terminal kernel are simpler yet more general than
those in Linux; perhaps more importantly, the plan 9 kernel was
intended to be portable, and support multiprocessors from the start.

aside: there's currently a lot of ignorant hype in the media
about the brilliance of having a Hardware Abstraction Layer in making a certain
o/s portable, but it's really no big deal.  like older portable operating systems,
plan 9's portability interface is a small collection of functions and
data structures.  no fuss.

outside the kernel, linux -- reasonably enough for
a unix/posix clone -- simply uses all the freely available software
for Unix-like systems that anyone can be bothered to port.  a lot
of that is Big and Complicated.  by contrast,  although many of the
older Unix commands are in Plan 9 at least in name,
Plan 9's commands are freshly written.  (the few things left from the ancien
rC)gime -- notably `troff' -- have at least had a facelift.)
a lot of crufty crud has been left behind.  after all, as andrew hume once put it:
``crud that isn't paged in is still crud''.

still, that's old stuff; worthy but dull.
the really interesting bits are the new things, including:

	the protocol 9P that binds everything together
	the file server, and its `dump' file system
	per-process name space
	union mounts
	Unicode
	user-level file servers
	shared memory multiprocess servers, using lean (threadbare?) processes
	cpu
	the window system 8B=
	Acme (is that named after the Acme Construction Co. in the Roadrunner cartoons?)
	FAST C compilers; simpler C library interface, and
		every compiler is a cross compiler
	simple support for multiple target architectures
	the concurrent programming language Alef
	acid
	for the administrator: a coherent approach to describing a network,
		and best of all from my point of view, it hasn't got BIND.

if you want a fairly conventional X11/Unix environment on your PC, Linux
is a reasonable choice.  Plan 9 has different aims.