[svlug] GNU Denemo chokes a dual core 2 GB server

Christian Einfeldt einfeldt at gmail.com
Mon Sep 24 16:11:12 PDT 2007


Here is the next issue for our public middle school project.  And it is
actually part of a recurring theme, it seems:  why is our linux lab lagging,
when most people think that it should be able to handle what we are throwing
at it.  More specifically, why are we experiencing delays in playing music
compositions using GNU Denemo under Edubuntu over a GB network that should
be performing better, and what can we do to solve the problem without
spending any money?

As most of you know from reading this list, I am a volunteer supporting a
public middle school with FOSS.  We have a brand new dual core server with 2
GB of RAM whose only purpose in life is to support 24 chubby clients running
edubuntu.  The thin clients have at least 256 MB of RAM, and most of them
have swap space on their hard drive also, although some of them are true
thin clients in that the hd has no swap and is basically a vestige.  I am
told that we have a gigabyte network.  The server feeds the signal to the
first 18 clients through one GB switch, and then that switch feeds another
identical switch with services about 6 more clients.

Our problem is that when we use GNU Denemo to play the short little
compositions that the students write in class, we can have only one student
play his / her composition at a time or the system is choked, meaning that
it lags.  More specifically, all of the students find that their GNOME
desktops are almost completely non-responsive to the mouse.  The mouse still
moves, but programs launch very slowly for about 5 mins, at which time the
choke point is presumably cleared, and then one student can again play his /
her composition.  It might be possible for, say, 2 students or maybe even
three students to play their music; but we don't know where that stress
point is.

And, in some ways, it doesn't even make sense to slowly add students and
have them play music, simply because some people who have heard of this
problem in passing furrow their brow and say that we shouldn't be having
these problems.

We are, of course, going to be trying to get more RAM in the clients; and
swap for all of the clients; and we have thought of running GNU Denomo
natively on each of the clients by booting them as stand alone work

For those of you who are familiar with the school, you can stop reading
here, because what follows is basic data about the school, and you probably
don't need to read it again.


This inner city school has absolutely no budget for a real tech support
person, and all of the teachers already are at work by 6:50 a.m., and they
usually stay until 6:30 p.m., and then each of the teachers is expected to
be available to field phone calls at home until 8 p.m.  All of this might
sound kind of drastic, but our students typically come to this school of 290
students under-performing their grade level by 2 grade levels, but leave the
school as 8th graders typically performing at or above grade level.
Seventy-five (75%) of our students come from households below the federal
poverty guidelines.  65% of our students are African American; 17% are
Latino; 10% are Asian; and 8% are Caucasian.  Despite the life challenges
facing our students, last year our students tested in first place (as a
student body) based on standardized testing.  So this school is succeeding
in many ways, but they are really struggling in terms of technology, and
that is all because of funding shortfalls.

Coincidentally, the students spend no time here on Windows boxes, except for
occasionally random Internet browsing on a teacher's Windows box.  But that
is the exception, because, as you can imagine, the teachers don't want the
students accessing their computers.  So when the students are not in the
lab, they are using PClinuxOS boxes in several of the classrooms to do their
Internet research.

Overall, this school is making miracles with no funding.  I am hoping to
move the whole school to FOSS eventually, but of course there is still a lot
of work to be done.  Thus far, the music teacher is fairly impressed with
the ability of students to compose music on GNU Denemo, but she would just
like to be able to have all of the students listen to their compositions at
the same time.  Typically, these compositions are no more than, say, 6 or 10
bars long, just enough to get the students familiar with the basics of
scales, rests, note duration, tempo, beat, etc.  Just the basics.

Thanks in advance for the help.

Christian Einfeldt,
Producer, The Digital Tipping
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