{{indexmenu_n>7}} ===== Checking job performance ===== Sometimes it is useful to take a closer look on the performance of jobs using the toolbox that Linux has. We will not describe the details of these tools but just mention a few. ==== Logging in to compute nodes ==== Using the ''ssh'' command line tool it is possible to login into nodes where one of your jobs is running. Please note that you can only login into these nodes. A connection to another node will be refused. Logging in can be done like this: ssh node34 After this you should obtain a command-line prompt on this node (if you have a job running on that node!). You can use ''squeue'' described earlier to see where your job is running. ==== Checking job performance ==== There are two tools that we will describe on this page. The first is ''top'', the second ''ps''. === top === The ''top'' tool will show an overview of running processes on the system. You can limit it to your own processes using the ''-u'' option. The tool will show the CPU utilization at ''%CPU'', the memory usage using ''VIRT'' for virtual (claimed) memory and ''RES'' for memory that is really used. The CPU usage should ideally be close to 100% for single core tasks and close to n*100% for multithreaded tasks where n is the number of threads. To see the individual threads of a multithreaded program you can press shift-H for uppercase H. The q key will exit top. === ps === Another useful tool is ''ps''. ''ps'' will show processes on the node. To see an extensive overview of the users processes you can use: ps -elf | egrep "UID|$USER" Please see the man page of ''ps'' for information about the meaning of the fields.