4.4. Submitting interactive jobs

Submitting interactive jobs

Sometimes users need more computational power to run commands from the command line. As a general rule, it is NOT a good idea to launch these commands from the login node, because the login node is a server designed to manage user sessions, it has limited resources and it does not behave well with CPU extensive sessions. Additionally, intensive CPU usage on the login node could reduce session speed and performance for the rest of the users. 

To solve this need, users can request an interactive job on a computing node with the qrsh command. Interactive jobs are only allowed on a single queue. qrsh behaves the same way as the rest of the scheduler commands: it inherits values from the queue where the job runs, but also user options can be specified.

Fig 1. inter.q values

Item Limit  Comment
Queue type             Interactive    User interaction managed by the scheduler.
Wall time 4 hours Every user can user can have up to 4 hours of interactive session in the node.
CPU time  64 hours Every user can user can have up to 64 CPU hours of interactive session in the node.
Architectures AMD/INTEL Node 11 for AMD architecture, Node 12 for INTEL architecture. 6 slots for each host.
Minimum slots available   12 cores

In case of heavy cluster usage, 16 processors are always reserved for this queue.

Maximum user allocatable slots 4 cores A single user cal allocate up to 4 processors on a single interactive session.
Maximum research group allocatable slots  8 Researchers on the same research group can allocate up to 576 processors on this queue. 
 
ijimenez@login:~$ qrsh< Linux node09 3.2.0-4-amd64 #1 SMP Debian 3.2.51-1 x86_64   The programs included with the Debian GNU/Linux system are free software; the exact distribution terms for each program are described in the individual files in /usr/share/doc/*/copyright.   Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent permitted by applicable law. Last login: Fri Dec 13 13:31:31 2013 from 192.168.7.6 ijimenez@node09:~$ 

The following command allows us to use an specific node: qrsh -l h='node11' -now no

This way, I request an interactive job inheriting the inter.q parameters and limits. As long as the session is, internally, a job registered on a queue, the qstat command will show a running job:

ijimenez@node10:~$ qstat 
job-ID prior name user state submit/start at queue slots ja-task-ID 
----------------------------------------------------------------------------------------------------------------- 
153890 0.47500 QRLOGIN ijimenez r 12/27/2013 09:31:40 inter.q@node10 1 
ijimenez@node10:~

The common qsub modifiers can be used when calling qrsh. Additionally, if the connection to the login node was configured to handle X graphics, the qrsh command on the nodes will also forward the graphical commands. Most common usage is to call Matlab within a node to take advantage of the higher amount of memory available: