On 3/12/21 6:37 PM, Sean Crosby wrote:
On Sat, 13 Mar 2021 at 08:48, Prentice Bisbal <pbis...@pppl.gov
<mailto:pbis...@pppl.gov>> wrote:
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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.
Thanks for the correction. That's what I originally thought, and then
read the definition he provided, which is exactly the same as in the
documentation, and completely misinterpreted it. When I look at the
sacct documentation and see that same definition in the context of all
the all the other MaxRSS values, it's clear I screwed up. Sorry!
SchedMD should reword that so even out of context it's clear what it
represents.
When I read "Maximum resident set size of all tasks in job" I
automatically thought "Maximum of the *sum* of the RSSes of each task.
Prentice
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
<mailto: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
