Re: [gembud] Limitations of centrally served gempak?

Hi Brendon,

I think the # of msg queues by default in CentOS is only 16.

You can up it by editing /etc/sysctl.conf. On our similarly-powered server, we added these lines to that file:

< # Controls the maximum number of message queues
< kernel.msgmni = 256
< kernel.shmall = 4294967296

Then type "sysctl -p" and that should make 256 message queues available to you without needing to reboot.

Note though that I've had issues with failed connections to the x server when multiple clients attempt to access the same x server, causing xw and gf processes to fail. This happens randomly.


Kevin Tyle, Systems Administrator               **********************
Dept. of Atmospheric & Environmental Sciences   ktyle@xxxxxxxxxxxxxxxx
University at Albany, ES-235                    518-442-4578 (voice)
1400 Washington Avenue                          518-442-5825 (fax)
Albany, NY 12222                                **********************

On Mon, 15 Nov 2010, Brendon Hoch wrote:


I'm running Gempak 5.11.4 under 64 bit Centos 5.5 on a server with 16 GB of memory and 8 x Intel Xeon 5450 @ 3.00GHz processors, standard out of the box kernel, things have been stable for a while.

Historically, I have taught a small class (4-5) where students log in to a central server via putty and run gempak command line programs (sfmap,gdplot3, etc.) while piping xwindows to their local screen (using Xming for Xwindow emulation)

This year, my class size is 11. When I get to about 6 instances of sfmap running, any additional sfmap attempts gets messages like this:

$ sfmap
Error in message send = 22
itype, ichan, nwords,1,-1,2
Creating process: gplt for queue -1
Error in message send = 22
itype, ichan, nwords,1,-1,3
[GEMPLT -1]  NMBRER - Mailbox read.

Interestingly, I do not have this problem with GUI programs like nmap2 or nwx, I have been able to run ~20 simultaneous instances without incident.

I've looked for renegade gplt processes and ipcs and found nothing out of the ordinary. System load & memory usage are both reasonable. Is there a limitation that I am not aware of? Does running in 64 bit have anything to do with it? Are there kernel options or gempak compilation options that can be set somewhere to get around this? '

Any advice is greatly appreciated.


Brendon Hoch
Technology Manager
Judd Gregg Meteorology Institute
MSC 48, Boyd Hall 321A
Plymouth State University
Plymouth, NH 03264
(603)535-2818 Fax: (603)535-2723

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