IMPORTANT:

• Computing on the login nodes is discouraged. Please use the compute nodes!
• Compiling, coding and result viewing can be done on login nodes, but will be faster on a compute node!
• Using too many resources for any kind of task on a login node will trigger automated and manual responses from us, resulting in your work being lost!
• This limitation is actively enforced. We reserve the right to terminate any process on the login nodes to maintain a good quality of service for all other users.
• You may also receive a verbal and written warning!

Technical Details

This limits apply only to the login-nodes, unless specified otherwise.

If you need a graphical session without these limits, please submit an interactive batchjob with X11 forwarding to the compute nodes.

If you need a console session without these limits, please submit an normal salloc job to the compute nodes.

CPU

We use cgroups on the login nodes to configure all user processes and enforce limits. 

Within a login node, we limit all processes of a user to a maximum of four (4) cores. We may also kill processes that use more than 20 minutes of CPU time, especially when a system becomes overloaded.

Real physical memory (RAM)

We limit the total amount of physical memory  (+swap) to 25% (of the total) that any user can use across all of their running processes. The following command displays the current memory quota usage:

memquota

Unfortunately, if a user hits this memory limit, the login-node may be unresponsive for a few seconds while the limits are enforced. As all users are affected by this, it is considerate and take this memory limits into account from the beginning.

Virtual memory

We do not enforce the amount of virtual memory you can use or allocate, but if your programs start  reaching to physical memory, the physical memory limit will be enforced!

Network and Disk

We enforce network and disk limits manually to guarantee a good quality of service for other users.

Please use one of the dedicated systems copy, copy18-1 or copy18-2 for applications that transfer data or need high network bandwidth, e.g. copy processes.