On Sat, 13 Mar 2021 at 08:48, Prentice Bisbal <pbis...@pppl.gov> wrote:
> * UoM notice: External email. Be cautious of links, attachments, or > impersonation attempts * > ------------------------------ > > It sounds like your confusing job steps and tasks. For an MPI program, > tasks and MPI ranks are the same thing. A slurm job has multiple steps. A > single job step could have only 1 task, while another step in the same job > can use 1,000 tasks. When looking at the amount of memory for a job, the > important number is the largest value of MaxRSS for all the job steps. Why > this important? Because if you don't request at least this much with your > --mem specification, your job may fail. > > Based on your definition, of aveRSS (I didn't go back and check the > documentation myself), it sounds like you're doing unnecessary math, since > I'm sure Slurm sums up the individual task max. RSS values for each task to > get MaxRSS, and then divides that by the number of tasks to get the AveRSS. > This is incorrect. MaxRSS is the maximum amount of RAM the task that used the most amount of RAM used. That is why there is then a MaxRSSNode and MaxRSSTask value. MaxRSSNode is the node the task that used the most amount of RAM was on, and MaxRSSTask is the task ID of the task that used the most amount of RAM. If you are trying to work out the RAM that the job as a whole used, use TRESUsageInTot For a job on our cluster: # sacct -j 24207294 -o JobID,Node,AveRSS,MaxRSS,MaxRSSTask,MaxRSSNode,TRESUsageInTot -p JobID|NodeList|AveRSS|MaxRSS|MaxRSSTask|MaxRSSNode|TRESUsageInTot| 24207294.0|spartan-bm[055-056,058-059,061-062,085,091-093,096,098-099,104,108,112-117,120-124]|927811665|962245K|3|spartan-bm058|cpu=4784-18:38:23,energy=0,fs/disk=3555263283,mem=217455859K,pages=2438,vmem=434981656K| This shows that AveRSS was 884MB, MaxRSS was task 3 running on spartan-bm058, which used 939MB, and all tasks in total used 212359MB Also remember that --mem is a per node memory request. It is not a per job or a per task memory request. Sean On 3/9/21 3:41 AM, xiaojingh...@163.com wrote: > > Hi guys, > I would like to calculate the CPU efficiency and Memory efficiency of slurm > jobs. > > I am having difficulty calculating the real “memory” a job use. > According to slurm, “maxRSS” means "Maximum resident set size of all tasks in > job”. If so, how can I get the memory used by a single job? As far as I am > concerned, if I need to know the memory used by a single job/jobstep, I need > to sum up the memory used for each task. So I think I should use the > “aveRSS” field which gives the "average resident set size of all tasks in > job”. If I multiply the “aveRSS” with “task”, I should get the real memory a > job/jobstep used. > > But I studied the code of the “seff” command and it claims to be equivalent > to "sacct -P -n -a --format > JobID,User,Group,State,Cluster,AllocCPUS,REQMEM,TotalCPU,Elapsed,MaxRSS,ExitCode,NNodes,NTasks > -j <job_id>”, which means I should use “maxRSS”. > > Can anyone give me some explanation on that? > > Very grateful for any help. > Thank you! > > Regards, > Xiaojing > > >
