🚀 go-pugleaf

In article <32382@winchester.mips.COM> mash@mips.COM (John Mashey) writes:
> How about getting this off the sociology track [because most of it came
> down to "I know good compcenters" vs "I don't], and consider some of
> the interesting system architectural issues, like:
> 
> 1) How much load do X-window terminals put on a a host?
> 2) How much load do diskless nodes put on a host?
> 3) If the people are doing the same kind of work, does the host do more
> or less disk I/O in cases 1) or 2)?  How does the Ethernet traffic differ?
> 4) Experiences with X-window terminals: how many can be served, doing what
> kind of work, from what kind of host?
> 5) How do you characterize the kinds of work that people do in any of
> these environments?
> -john mashey	DISCLAIMER: <generic disclaimer, I speak for me only, etc>
> UUCP: 	{ames,decwrl,prls,pyramid}!mips!mash  OR  mash@mips.com
> DDD:  	408-991-0253 or 408-720-1700, x253
> USPS: 	MIPS Computer Systems, 930 E. Arques, Sunnyvale, CA 94086

We have been doing quite a bit of evaluation of X-terminals as an
alternative to workstations for undergraduate computing laboratories.
The testing that we did was on a Mips M120-5, with 16Mb of memory, with
9 NCD16's, 1 NCD19 and a Visual X-19.
We place 10 pgrads/hons/tutors/programmers in front of these
terminals (one ncd16 was locked in an office!), and performed
sufficient brain surgery to make them behave like second and
third year computer science students (you can guess whether
the surgery involved removal or addition of tissue!).
1. CPU load is hard to quantify, the machine stopped working
2. All our competent sun users run their applications on the fastest
   machines, this means or sun servers or (more likely) our 4 M120s.
   Distributed computing has just meant that our users just move from
   one cpu to another whenever a faster one comes along ...
   Measuring load on a sun.
   When we didn't have the M120's the sun servers were at their limit
   with the 10-12 diskless/dataless clients that they served.
3. On the basis of ethernet traffic, the analysis showed that a user
   with 5 xterms, running vi, and with an xclock running was doing about
   2-3k worth of I/O on the ethernet, this is our expected typical student
   load (we don't actually expect to use vi!).
   A sun 3/50 running suntools was generating ~20k ethernet traffic for
   the same sort of task (fast editting of pascal source and running).
   On the basis of this we concluded that the x-terms were no problem on
   the ethernet if they were just used as text-based windowing systems.
   Running a program like xmaze or other graphically oriented X applications
   caused ~30kb of traffic on the ether.
4. The X-terms need ~3Mb to be as usefull as suns (~18 xterms, fast response,
   able to store overlaid windows in the backing store etc).
   They work very well, when served on a lightly loaded, well configured
   machine, they can be very fast (some reminders of blit performance
   on a single user vax), mainly from fast window creation/deletion,
   this is especially true for the NCD19(68020 processor).
   I'd expect between 15-20 can be served by a 48Mb M120. This should be
   true for our expected student loads. We were supporting 10 once we
   grabbed some boards out of our other machines and made the test
   machine a 32Mb beast.
5. X-terminals are a very good answer for people who want a windowed
   environment for mainly textual work, or program development.
   They will last longer than the server that they are connected to, and
   will therefore end up as a much cheaper solution than workstations
   that need to be replaced or seriously upgraded every few years because
   of the insatiable memory demands of commercial Unix systems.
   Most (90%) of our users fit into this category of users, the most popular
   "graphical" program run on our suns is a home grown troff proofing
   program, this sort of activity should suit Xterminals perfectly.
   People requiring "real graphics" should have their own
   dedicated workstation, but then again that machine should have at least
   24 bit planes, 32Mb ram, and some serious disks, and > 10 mips in the
   engine room. Right now I don't think we can afford to give this to each
   of our users, so we compromise!
6. The above 5 questions should have been asked in something that
   approximates reverse order.

Notes: Each "student" load was consuming ~2-3Mb of the CPU servers' memory.
This is what cause the initial hiccup during testing. 48Mb should mean
no swapping during normal use (20 users), although 32M was showing a small
amount of swapping during the testing (10 users).
There seems to be a large amount of swap fragmentation which caused some
of the initial slow down, this could be an artifact of the way NTEXTs
are treated in RISCOS?

It is expected that the students will be using a windowing editor
(Rob Pike's sam) and Killian's debugger (pi), which should be great
win over vi and dbx. Xterminals will give us the ability to give a
windowing environment to all our users, while fitting into our
shrinking budgets (we are open to donations!!!), and allowing us to
administer the machines with the few technical staff that we have, it should
almost be like ascii terminals connected to some central machines.

Ray Loyzaga,
Basser Department of Computer Science
Sydney University
yar@cs.su.oz.au