Cannot enforce memory limits in SLURM

Question

I am using Slurm on a single node (control and compute) and I cannot seem to correctly limit memory. The script seems to call SBATCH with small memory values (3G), but I see values in top that exceed 25G. Sacct gives me the correct values:

squeue -o "%C %m"
CPUS MIN_MEMORY
2 3G

This is my slurm.conf:

#
SlurmctldHost=schopenhauer
#
#DisableRootJobs=NO
#EnforcePartLimits=NO
#Epilog=
#EpilogSlurmctld=
#FirstJobId=1
#MaxJobId=999999
#GresTypes=
#GroupUpdateForce=0
#GroupUpdateTime=600
#JobFileAppend=0
#JobRequeue=1
#JobSubmitPlugins=1
#KillOnBadExit=0
#LaunchType=launch/slurm
#Licenses=foo*4,bar
#MailProg=/bin/mail
#MaxJobCount=5000
#MaxStepCount=40000
#MaxTasksPerNode=128
MpiDefault=none
#MpiParams=ports=#-#
#PluginDir=
#PlugStackConfig=
#PrivateData=jobs
#ProctrackType=proctrack/cgroup
ProctrackType=proctrack/linuxproc
#Prolog=
#PrologFlags=
#PrologSlurmctld=
#PropagatePrioProcess=0
#PropagateResourceLimits=
#PropagateResourceLimitsExcept=
#RebootProgram=
ReturnToService=1
#SallocDefaultCommand=
SlurmctldPidFile=/var/run/slurmctld.pid
SlurmctldPort=6817
SlurmdPidFile=/var/run/slurmd.pid
SlurmdPort=6818
SlurmdSpoolDir=/var/spool/slurmd
SlurmUser=slurm
#SlurmdUser=root
#SrunEpilog=
#SrunProlog=
StateSaveLocation=/var/spool/slurmd
SwitchType=switch/none
#TaskEpilog=
TaskPlugin=task/affinity
TaskPluginParam=Sched
#TaskProlog=
#TopologyPlugin=topology/tree
#TmpFS=/tmp
#TrackWCKey=no
#TreeWidth=
#UnkillableStepProgram=
#UsePAM=0
#
#
# TIMERS
#BatchStartTimeout=10
#CompleteWait=0
#EpilogMsgTime=2000
#GetEnvTimeout=2
#HealthCheckInterval=0
#HealthCheckProgram=
InactiveLimit=0
KillWait=30
#MessageTimeout=10
#ResvOverRun=0
MinJobAge=300000
#OverTimeLimit=0
SlurmctldTimeout=120
SlurmdTimeout=300
#UnkillableStepTimeout=60
#VSizeFactor=0
Waittime=0
#
#
# SCHEDULING
#DefMemPerCPU=0
#MaxMemPerCPU=0
#SchedulerTimeSlice=30
SchedulerType=sched/backfill
SelectType=select/cons_tres
SelectTypeParameters=CR_Core
#
#
# JOB PRIORITY
#PriorityFlags=
#PriorityType=priority/basic
#PriorityDecayHalfLife=
#PriorityCalcPeriod=
#PriorityFavorSmall=
#PriorityMaxAge=
#PriorityUsageResetPeriod=
#PriorityWeightAge=
#PriorityWeightFairshare=
#PriorityWeightJobSize=
#PriorityWeightPartition=
#PriorityWeightQOS=
#
#
# LOGGING AND ACCOUNTING
#AccountingStorageEnforce=0
#AccountingStorageHost=
AccountingStorageLoc=/var/log/slurm/slurm_jobacct.log
#AccountingStoragePass=
#AccountingStoragePort=
AccountingStorageType=accounting_storage/filetxt
#AccountingStorageUser=
AccountingStoreJobComment=YES
ClusterName=cluster
#DebugFlags=
#JobCompHost=
JobCompLoc=/var/log/slurm/slurm_jobcomp.log
#JobCompPass=
#JobCompPort=
JobCompType=jobcomp/filetxt
#JobCompUser=
#JobContainerType=job_container/none
JobAcctGatherFrequency=30
JobAcctGatherType=jobacct_gather/linux
SlurmctldDebug=info
SlurmctldLogFile=/var/log/slurm/slurmctld.log
SlurmdDebug=debug5
SlurmdLogFile=/var/log/slurm/slurmd.log
#SlurmSchedLogFile=
#SlurmSchedLogLevel=
#
#
# POWER SAVE SUPPORT FOR IDLE NODES (optional)
#SuspendProgram=
#ResumeProgram=
#SuspendTimeout=
#ResumeTimeout=
#ResumeRate=
#SuspendExcNodes=
#SuspendExcParts=
#SuspendRate=
#SuspendTime=
#
#
# COMPUTE NODES
NodeName=schopenhauer CPUs=128 Boards=1 SocketsPerBoard=2 CoresPerSocket=32 ThreadsPerCore=2 RealMemory=500000 State=UNKNOWN
PartitionName=short Nodes=schopenhauer Default=YES MaxTime=INFINITE State=UP

Did I misunderstand something? Why does it say minimum memory when I want to make that minimum and maximum as well?

EDIT: I just noticed by setting required memory to a larger one that this doesn't work as a minimum either i.e. many tasks were started even though there was enough RAM for only 12 of them (I requested 40G and I have 500G). Is this the same problem?

Answer 1

Slurm controls memory through the Linux cgroup functionality. You need to set TaskPlugin=task/cgroup in slurm.conf (Cf. https://slurm.schedmd.com/cgroups.html) and ConstrainRAMSpace=yes in cgroup.conf (Cf. https://slurm.schedmd.com/cgroup.conf.html). Then the memory requested by jobs with --mem or --mem-per-cpu becomes effectively a hard limit in addition to being a resource request.

The -m option of gives the memory requested by the job. As a request, it is considered a minimum requirement. But if you configure cgroup it effectively also becomes the maximum.

Answer 2

I don't think slurm enforces memory or cpu usage. It's just there as indication what you think your job's usage will be. To set binding memory you could use ulimit, something like ulimit -v 3G at the beginning of your script.

Just know that this will likely cause problems with your program as it actually requires the amount of memory it requests, so it won't finish succesfully.