[sf-lug] GNU Denemo chokes a dual core 2 GB server at the school

jim stockford jim at well.com
Mon Sep 24 16:59:03 PDT 2007

here's how i understand attacking the problem:
* watch network traffic to see if the network is overloaded.
* watch workstations/chubby-clients to see where the CPU is working
* watch the server to see where the CPU is working

On Sep 24, 2007, at 4:09 PM, Christian Einfeldt wrote:

> hi
> 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.  My question is fairly long to explain, but 
> simple to summarize:  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 stations. 
> 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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