[slurm-dev] Re: Scheduling weirdness

Fri, 16 Jun 2017 04:21:26 -0700 


On 16-06-17 11:42, TO_Webmaster wrote:

What are the values of bf_window and bf_resolution in your configuration?


> From the documentation of bf_window: "The default value is 1440
> minutes (one day). A value at least as long as the highest allowed
> time limit is generally advisable to prevent job starvation."

SchedulerType=sched/backfill
SchedulerParameters=bf_window=7-0,defer
SelectType=select/cons_res
SelectTypeParameters=CR_CORE_MEMORY

bf_resolution should be the default (60s).
Our maximum time-limit is 7-0. Any ideas on what would be the optimal bf_window value for this?
In relation to the problem: most running jobs had a time limit of 6-21, and the highest priority job was scheduled to start within the 7-0 bf_window. Does that rule out the bf_window as a factor in the problem, or not?
In the schedule iteration at 2017-06-15T23:22:10, the highest priority job was scheduled to start at 2017-06-22T18:29:17, 6-19:07:07 ahead, so I don't understand why in the same iteration the lower priority job with a longer 6-21 time limit was immediately started on the same node?
Using defer was an attempt to get more optimal scheduling, but unfortunately it didn't change anything for this problem. 

Robbert


2017-06-16 1:16 GMT+02:00 Robbert Eggermont <[email protected]>:


Hello,

In our Slurm setup (now 17.02.4) I've noticed several times now that
backfilled jobs push back the start time of the highest priority job.
I'm not sure if this is due to a configuration error or an scheduler error,
and since I'm having a hard time diagnosing what's happening, I was hoping
for some insightful tips.

What happens is that when the highest priority pending job needs a lot of
resources (CPUs, ...), slurm will backfill lower priority jobs with less
requirements but with a higher timelimit than the currently running jobs.

For example, the highest priority job needs a full node, and the first node
will become available in 6 days; our slurm will happily backfill all pending
lower priority 2-CPU 7-day jobs on every possible node in the cluster, thus
pushing back the highest priority job 1 day.

Looking into the scheduler debugging info, I noticed some things I can't
explain:
1) the highest priority job ("A") is not always scheduled to start on the
first node ("1") that will become available;
2) in the same iteration, the backfill logic will start another, lower
priority, smaller job with a timelimit longer than the expected start time
of job "A" on the same node "1";
3) when "A" is scheduled to start on another node, the scheduled starting
time remains the same (i.e. it is not updated to the time that the new node
becomes available).
4) the scheduled starting time of the highest priority job ("A") is
sometimes later than the time that the node becomes available;

See below for some log entries for these events.

Does anybody have an idea what's going on here, and how we can fix it?

Robbert


1)
JobID=1315558 has a scheduled start time on node maxwell of
2017-06-22T19:11:16; forcing it to another node (by draining maxwell)
reduces the start time to 2017-06-22T16:47:43.2017-06-15T23:22:10
(But slurm is consistent: when maxwell is resumed, the job is scheduled
there again, with the later start time.)


[2017-06-15T22:11:26.688] backfill: beginning
[2017-06-15T22:11:26.693] backfill test for JobID=1315558 Prio=22703485
Partition=general
[2017-06-15T22:11:26.694] Job 1315558 to start at 2017-06-22T19:11:16, end
at 2017-06-27T07:11:00 on maxwell
[2017-06-15T22:11:26.694] backfill: reached end of job queue
[2017-06-15T22:11:52.223] update_node: node maxwell state set to DRAINING
[2017-06-15T22:11:56.695] backfill: beginning
[2017-06-15T22:11:56.701] backfill test for JobID=1315558 Prio=22703485
Partition=general
[2017-06-15T22:11:56.703] Job 1315558 to start at 2017-06-22T16:47:43, end
at 2017-06-27T04:47:00 on parzen
[2017-06-15T22:11:56.703] backfill: reached end of job queue


...


[2017-06-15T22:34:46.036] backfill: beginning
[2017-06-15T22:34:46.039] =========================================
[2017-06-15T22:34:46.039] Begin:2017-06-15T22:34:46
End:2017-06-15T22:41:462017-06-15T23:22:10
Nodes:100plus,gauss,hopper,markov,neumann,parzen,sanger,viterbi,watson
[2017-06-15T22:34:46.039] =========================================
[2017-06-15T22:34:46.040] backfill test for JobID=1315558 Prio=22776428
Partition=general
[2017-06-15T22:34:46.040] Test job 1315558 at 2017-06-15T22:34:46 on
hopper,parzen,viterbi
[2017-06-15T22:34:46.040] Job 1315558 to start at 2017-06-22T16:47:43, end
at 2017-06-27T04:47:00 on parzen
[2017-06-15T22:34:46.040] backfill: reached end of job queue
[2017-06-15T22:34:55.236] update_node: node maxwell state set to ALLOCATED
[2017-06-15T22:35:16.041] backfill: beginning
[2017-06-15T22:35:16.045] =========================================
[2017-06-15T22:35:16.045] Begin:2017-06-15T22:35:16
End:2017-06-15T22:42:16
Nodes:100plus,gauss,hopper,markov,maxwell,neumann,parzen,sanger,viterbi,watson
[2017-06-15T22:35:16.045] =========================================
[2017-06-15T22:35:16.045] backfill test for JobID=1315558 Prio=22776428
Partition=general
[2017-06-15T22:35:16.045] Test job 1315558 at 2017-06-15T22:35:16 on
hopper,maxwell,parzen,viterbi
[2017-06-15T22:35:16.046] Job 1315558 to start at 2017-06-22T19:11:16, end
at 2017-06-27T07:11:00 on maxwell
[2017-06-15T22:35:16.046] backfill: reached end of job queue



2)
Our highest prio job is now scheduled to start on maxwell at
2017-06-22T18:29:17, but then another job is backfilled on maxwell with
EndTime=2017-06-22T21:02:10??


[2017-06-15T23:22:10.227] backfill: beginning
[2017-06-15T23:22:10.231] =========================================
[2017-06-15T23:22:10.231] Begin:2017-06-15T23:22:10
End:2017-06-15T23:29:10
Nodes:100plus,gauss,hopper,markov,maxwell,neumann,parzen,sanger,viterbi,watson
[2017-06-15T23:22:10.231] =========================================
[2017-06-15T23:22:10.231] backfill test for JobID=1315558 Prio=22938897
Partition=general
[2017-06-15T23:22:10.231] Test job 1315558 at 2017-06-15T23:22:10 on
hopper,maxwell,parzen,viterbi
[2017-06-15T23:22:10.232] Job 1315558 to start at 2017-06-22T18:29:17, end
at 2017-06-27T06:29:00 on maxwell
[2017-06-15T23:22:10.232] backfill test for JobID=1314524 Prio=10000002
Partition=general
[2017-06-15T23:22:10.233] Test job 1314524 at 2017-06-15T23:22:10 on
gauss,hopper,markov,maxwell,neumann,parzen,sanger,viterbi,watson
[2017-06-15T23:22:10.233] backfill: Started JobId=1314524 in general on
maxwell
[2017-06-15T23:22:10.237] backfill: reached end of job queue



3 and 4)
Our job is immediately scheduled on another node, however the scheduled
starting time 2017-06-22T18:29:17 remains the same, although the current
longest jobs on parzen has EndTime=2017-06-22T15:27:08.
Almost an hour later the start time is updated (note: the job complete
should be unrelated since the job ran on maxwell, right?).
Then 40 minutes later the start time is updated again, pushed back (while no
new jobs were started on parzen in the mean time, and we don't suspend;
there was however another job complete on maxwell?).


[2017-06-15T23:22:40.237] backfill: beginning
[2017-06-15T23:22:40.241] =========================================
[2017-06-15T23:22:40.242] Begin:2017-06-15T23:22:40
End:2017-06-15T23:29:40
Nodes:100plus,gauss,hopper,markov,maxwell,neumann,parzen,sanger,viterbi,watson
[2017-06-15T23:22:40.242] =========================================
[2017-06-15T23:22:40.242] backfill test for JobID=1315558 Prio=22938897
Partition=general
[2017-06-15T23:22:40.242] Test job 1315558 at 2017-06-15T23:22:40 on
hopper,maxwell,parzen,viterbi
[2017-06-15T23:22:40.243] Job 1315558 to start at 2017-06-22T18:29:17, end
at 2017-06-27T06:29:00 on parzen
[2017-06-15T23:22:40.243] backfill: reached end of job queue


...


[2017-06-16T00:16:06.161] backfill: beginning
[2017-06-16T00:16:06.165] =========================================
[2017-06-16T00:16:06.165] Begin:2017-06-16T00:16:06
End:2017-06-16T00:23:06
Nodes:100plus,gauss,hopper,markov,maxwell,neumann,parzen,sanger,viterbi,watson
[2017-06-16T00:16:06.165] =========================================
[2017-06-16T00:16:06.165] backfill test for JobID=1315558 Prio=23087721
Partition=general
[2017-06-16T00:16:06.165] Test job 1315558 at 2017-06-16T00:16:06 on
hopper,maxwell,parzen,viterbi
[2017-06-16T00:16:06.166] Job 1315558 to start at 2017-06-22T18:29:17, end
at 2017-06-27T06:29:00 on parzen
[2017-06-16T00:16:06.167] backfill: reached end of job queue
[2017-06-16T00:16:12.763] job_complete: JobID=1316201 State=0x8003
NodeCnt=1 done
[2017-06-16T00:16:36.167] backfill: beginning
[2017-06-16T00:16:36.170] =========================================
[2017-06-16T00:16:36.170] Begin:2017-06-16T00:16:36
End:2017-06-16T00:23:36
Nodes:100plus,gauss,hopper,markov,maxwell,neumann,parzen,sanger,viterbi,watson
[2017-06-16T00:16:36.170] =========================================
[2017-06-16T00:16:36.170] backfill test for JobID=1315558 Prio=23101442
Partition=general
[2017-06-16T00:16:36.170] Test job 1315558 at 2017-06-16T00:16:36 on
hopper,maxwell,parzen,viterbi
[2017-06-16T00:16:36.171] Job 1315558 to start at 2017-06-22T16:41:17, end
at 2017-06-27T04:41:00 on parzen
[2017-06-16T00:16:36.171] backfill: reached end of job queue


...


[2017-06-16T00:55:41.642] backfill: beginning
[2017-06-16T00:55:41.646] =========================================
[2017-06-16T00:55:41.646] Begin:2017-06-16T00:55:41
End:2017-06-16T01:02:41
Nodes:100plus,gauss,hopper,markov,maxwell,neumann,parzen,sanger,viterbi,watson
[2017-06-16T00:55:41.646] =========================================
[2017-06-16T00:55:41.646] backfill test for JobID=1315558 Prio=23186871
Partition=general
[2017-06-16T00:55:41.646] Test job 1315558 at 2017-06-16T00:55:41 on
hopper,maxwell,parzen,viterbi
[2017-06-16T00:55:41.647] Job 1315558 to start at 2017-06-22T16:41:17, end
at 2017-06-27T04:41:00 on parzen
[2017-06-16T00:55:41.694] backfill: reached end of job queue
[2017-06-16T00:55:47.592] job_complete: JobID=1316353 State=0x1 NodeCnt=1
WEXITSTATUS 0
[2017-06-16T00:55:47.598] job_complete: JobID=1316353 State=0x8003
NodeCnt=1 done
[2017-06-16T00:56:11.695] backfill: beginning
[2017-06-16T00:56:11.701] =========================================
[2017-06-16T00:56:11.701] Begin:2017-06-16T00:56:11
End:2017-06-16T01:03:11
Nodes:100plus,gauss,hopper,markov,maxwell,neumann,parzen,sanger,viterbi,watson
[2017-06-16T00:56:11.701] =========================================
[2017-06-16T00:56:11.701] backfill test for JobID=1315558 Prio=23186871
Partition=general
[2017-06-16T00:56:11.701] Test job 1315558 at 2017-06-16T00:56:11 on
hopper,maxwell,parzen,viterbi
[2017-06-16T00:56:11.703] Job 1315558 to start at 2017-06-22T18:01:33, end
at 2017-06-27T06:01:00 on parzen
[2017-06-16T00:56:11.703] backfill: reached end of job queue



--
Robbert Eggermont                                  Intelligent Systems
[email protected]         Electr.Eng., Mathematics & Comp.Science
+31 15 27 83234                         Delft University of Technology

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