This version (2022/06/22 16:53) was approved by msiegel.The Previously approved version (2021/05/14 13:52) is available.This is an old revision of the document!
# Monitoring Processes & Threads
## CPU Load
There are several ways to monitor the threads CPU load distribution of your job, either live directly on the compute node, or by modifying the job script, or the application code.
### Live
So we assume your program runs, but could it be faster? SLURM gives you a `Job ID`, type `squeue –job myjobid` to find out on which node your job runs; say n372-007. Type `ssh n372-007`, to connect to the given node. Type `top` to start a simple task manager:
``` [myuser@l32]$ sbatch job.sh [myuser@l32]$ squeue -u myuser JOBID PARTITION NAME USER ST TIME NODES NODELIST(REASON) 1098917 mem_0096 gmx_mpi myuser R 0:02 1 n372-007 [myuser@l32]$ ssh n372-007 [myuser@n372-007]$ top ```
Within `top`, hit the following keys (case sensitive): `H t 1`. Now you should be able to see the load on all the available CPUs, as an example:
``` top - 16:31:51 up 181 days, 1:04, 3 users, load average: 1.67, 3.39, 3.61 Threads: 239 total, 2 running, 237 sleeping, 0 stopped, 0 zombie %Cpu0 : 69.8/29.2 99[|||||||||||||||||||||||||||||||||||||||||||||||| ] %Cpu1 : 97.0/2.3 99[|||||||||||||||||||||||||||||||||||||||||||||||| ] %Cpu2 : 98.7/0.7 99[|||||||||||||||||||||||||||||||||||||||||||||||| ] %Cpu3 : 95.7/4.0 100[|||||||||||||||||||||||||||||||||||||||||||||||| ] %Cpu4 : 99.0/0.3 99[|||||||||||||||||||||||||||||||||||||||||||||||| ] %Cpu5 : 98.7/0.3 99[|||||||||||||||||||||||||||||||||||||||||||||||| ] %Cpu6 : 99.3/0.0 99[|||||||||||||||||||||||||||||||||||||||||||||||||] %Cpu7 : 99.0/0.0 99[|||||||||||||||||||||||||||||||||||||||||||||||| ] KiB Mem : 65861076 total, 60442504 free, 1039244 used, 4379328 buff/cache KiB Swap: 0 total, 0 free, 0 used. 62613824 avail Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
18876 myuser 20 0 9950.2m 303908 156512 S 99.3 0.5 0:11.14 gmx_mpi 18856 myuser 20 0 9950.2m 303908 156512 S 99.0 0.5 0:12.28 gmx_mpi 18870 myuser 20 0 9950.2m 303908 156512 R 99.0 0.5 0:11.20 gmx_mpi 18874 myuser 20 0 9950.2m 303908 156512 S 99.0 0.5 0:11.25 gmx_mpi 18872 myuser 20 0 9950.2m 303908 156512 S 98.7 0.5 0:11.19 gmx_mpi 18873 myuser 20 0 9950.2m 303908 156512 S 98.7 0.5 0:11.15 gmx_mpi 18871 myuser 20 0 9950.2m 303908 156512 S 96.3 0.5 0:11.09 gmx_mpi 18875 myuser 20 0 9950.2m 303908 156512 S 95.7 0.5 0:11.02 gmx_mpi 18810 root 20 0 0 0 0 S 6.6 0.0 0:00.70 nv_queue … ```
In our example all 8 threads are utilised; which is good. The opposite is not true however, sometimes the best case still only uses 40% on most CPUs!
The columns `VIRT` and `RES` indicate the *virtual*, respective *resident* memory usage of each process (unless noted otherwise in kB). The column `COMMAND` lists the name of the command or application.
In the following screenshot we can see stats for all 32 threads of a compute node running `VASP`:
### Job Script
If you are using `Intel-MPI` you might include this option in your batch script: ``` I_MPI_DEBUG=4 ```
### Application Code
If your application code is in `C`, information about the locality of processes and threads can be obtained via library functions using either of the following libraries:
#### mpi.h ``` #include “mpi.h” … MPI_Get_processor_name(processor_name, &namelen); ```
#### sched.h (scheduling parameters) ``` #include <sched.h> … CPU_ID = sched_getcpu(); ```
#### hwloc.h (Hardware locality) ``` #include <hwloc.h> …
hwloc_topology_t topology; hwloc_cpuset_t cpuset; hwloc_obj_t obj; hwloc_topology_init ( &topology); hwloc_topology_load ( topology); hwloc_bitmap_t set = hwloc_bitmap_alloc(); hwloc_obj_t pu; err = hwloc_get_proc_cpubind(topology, getpid(), set, HWLOC_CPUBIND_PROCESS); pu = hwloc_get_pu_obj_by_os_index(topology, hwloc_bitmap_first(set)); int my_coreid = hwloc_bitmap_first(set); hwloc_bitmap_free(set); hwloc_topology_destroy(topology);
compile: mpiicc -qopenmp -o ompMpiCoreIds ompMpiCoreIds.c -lhwloc ```