Resource Limitation on Dialog Systems
Generally speaking, there are two types of relevant resource limitations on our dialog systems:
Per-process limits, obtained using the command:ulimit -a
- Per-user limits, realized with Linux cgroups, cf. https://www.kernel.org/doc/Documentation/cgroup-v1/cgroups.txt
By means of the cgroup cpu subsystem all processes that belong to the same user (UID) are configured to get the same amount of CPU cycles as all processes of every other user. E.g., if user A occupies a whole system with running processes, user B who starts one (single-threaded) process will nevertheless get 100% of one CPU.
There is currently no explicit per-process limit for CPU usage defined. Nevertheless, we may kill (with SIGXCPU) processes that have used more than 20 minutes of CPU time, especially when a system becomes overloaded.
If a session with more than 20 minutes CPU time is needed, an interactive batchjob with X11 forwarding can be submitted, using one of the compute nodes, to fulfill the needs.
There is a limit on the total amount of physical memory (+swap) that any user may use in all of his running processes. The following command displays the current memory quota usage:
Unfortunately, if a user hits its memory limit, the system as a whole may be unresponsive for a few seconds. Since all users are affected by this, it is considerate to take the memory limit from the beginning into account.
If a session with more memory is needed, an interactive batchjob with X11 forwarding can be submitted, using one of the compute nodes, to fulfill the needs.
There are no limits defined for virtual memory.
There are no resource limits on network usage in the strict sense. However, in order to avoid disturbing other users we suggest that you use one of the dedicated systems copy, copy18-1 or copy18-2 for applications that need high network bandwidth, e.g. copy processes.
Resource limitations on "X" dialog systems
On the dialog systems dedicated to start remote desktop sessions (login18-x-1, login18-x-2), the following limits per user apply:
- 16 GB physical memory
- 400% of all available CPU cycles (where 100% corresponds to one CPU core)