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Re: [K12OSN] Poor performance woes



On 09/20/2011 04:36 PM, Gideon Romm wrote:
Try enabling NBD_SWAP.  If the clients have insufficient RAM, the best
you can do is add swap space and hope the OS will swap out something
else.

Thanks. I've already got that enabled as best I can tell. Here's a snippet from chkconfig --list:

xinetd based services:
  [snip]
        nbdrootd:       on
        nbdswapd:       on

Maybe that's where the 21MiB/sec is coming from.

As soon as I can get back to the school, I'll run top on the TC and see what's going on.

Would it be possible (or advisable) to run swap on the TC from a local HD instead of over the network?


-Gadi

On Tue, Sep 20, 2011 at 3:18 PM, Jomegat<jomegat jomegat com>  wrote:
I have a K12Linux setup based on EL6-64.  The TC's are ancient i686's with
256M RAM and 10/100 nics.  The TS has a gigE NIC, and between the TS&  TCs
is a managed switch with 2 gigE ports and 24 10/100 ports.  The TS is
connected via one of the gigE's.

We have a student who is having real performance problems when he loads a
page.  I went in today to be there while he was experiencing woe, and ran
the system monitor applet.

When he loads the web page - with no flash in it that I can find - the
network maxes out at 12MiB/sec, and it takes an eternity for the page to
load.  He reports that sometimes this particular page will cause the TC to
crash (black screen with text followed by login screen), but he was not able
to reproduce that while I was there.  I suspect there is some user error
involved in the crash scenario, but it will be difficult to prove.

I had tried running firefox as a local app last month, but the school needs
flash, and it requires 512M.  Performance on these TC's was substantially
worse when running FF as a local app, so I backed off of that.

The page he was trying to load is password protected, but I had him ctrl-U
while he had it open, and save the source to a file which I can share if
need be.  It is filled with javascript, but I'm not sure that's the culprit
(though it seems the most likely suspect).  I found no .flv, FLV, .swf, or
.SWF in the file anywhere.

As an experiment, I connected a monitor, keybd, and mouse directly to the
server and had him login there.  The page loads just fine that way.  That
might be a possible solution, but for some reason, the display is incredibly
blurry.  If I make that permanent, I'd have to run some cable through the
wall (they're pinched in the door right now, and barely reach).

Before they called me in to look at this, he had been bringing his mom's
laptop to school so he could do his work (it's an online course).  If it
crashes while he is taking a quiz, he loses a test attempt or gets a bad
grade, so this has to be reliable.

His mom is on the school board, and she is pushing the school to abandon
LTSP in favor of a Windows solution.  They think that if they install some
flavor of windows on the TC's they will get better performance, but I
believe they won't, as flash will need 512M no matter the OS.  I think they
will need all new PC's if they go that route.

I am on the cusp of losing my network to Windows, at which point I will
resign my post as unpaid volunteer sysadmin, so if I sound a little
desperate, now you know why.

Any help here would be greatly appreciated.

--
Jim Thomas            Principal Applications Engineer  Bittware, Inc
jthomas bittware com  http://www.bittware.com    (603) 226-0404 x536
The problem with the future is that it keeps turning into the present -
Hobbes

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--
Jim Thomas            Principal Applications Engineer  Bittware, Inc
jthomas bittware com  http://www.bittware.com    (603) 226-0404 x536
The problem with the future is that it keeps turning into the present - Hobbes


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