[K12OSN] Poor performance woes

[Jomegat]

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