[slurm-users] Cgroups and swap with 18.08.1?

[Bill Broadley]

Greetings,

I'm using ubuntu-18.04 and slurm-18.08.1 compiled from source.

I followed the directions on:
https://slurm.schedmd.com/cgroups.html

And:
https://slurm.schedmd.com/cgroup.conf.html

That resulted in:
$ cat slurm.conf | egrep -i "cgroup|CR_"
ProctrackType=proctrack/cgroup
TaskPlugin=task/cgroup
SelectTypeParameters=CR_CPU_MEMORY
JobAcctGatherType=jobacct_gather/cgroup

$ cat /etc/default/grub  | grep GRUB_CMDLINE_LINUX=
GRUB_CMDLINE_LINUX='cgroup_enable=memory swapaccount=1 console=tty0
transparent_hugepage=madvise console=ttyS0,57600'

$ cat cgroup.conf
CgroupAutomount=yes
ConstrainCores=yes
ConstrainDevices=yes
ConstrainRAMSpace=yes
ConstrainSwapSpace=yes
MaxSwapPercent=0
AllowedSwapSpace=0

So I expect jobs to not use swap.  Turns out if I run a 3GB ram process with
sbatch --mem=1000 I just get a process that uses 1GB ram and 2GB of swap.

So a 3GB process with --mem=1000:
  $ ps acux
  USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
  bill     17698 11.1  1.5 2817020 1015392 ?     D    20:40   0:13 stream\

  $ smem
  User     Count     Swap      USS      PSS      RSS
  bill         1  1795552  1017048  1017076  1018492

With --mem=3000 zero swap is used and the job consumes 100% of a CPU.