Improve Slurm cgroup.conf support (#195)

* Support defining custom cgroup.conf options

* Restart Slurm if cgroup.conf has changed

Author: priteau

README.md

@@ -107,7 +107,14 @@ partition configuration for each.
 [slurm.conf](https://slurm.schedmd.com/slurm.conf.html). Keys are slurm.conf
 parameter names and values are lists or strings as appropriate. This can be
 used to supplement or override the template defaults. Templated parameters can
-also be removed by setting the value to the literal string`'omit'` - note
+also be removed by setting the value to the literal string `'omit'` - note
+that this is *not the same* as the Ansible `omit` [special variable](https://docs.ansible.com/ansible/latest/reference_appendices/special_variables.html#term-omit).
+
+`openhpc_cgroup_config`: Optional. Mapping of additional parameters and values for
+[cgroup.conf](https://slurm.schedmd.com/cgroup.conf.html). Keys are cgroup.conf
+parameter names and values are lists or strings as appropriate. This can be
+used to supplement or override the template defaults. Templated parameters can
+also be removed by setting the value to the literal string `'omit'` - note
 that this is *not the same* as the Ansible `omit` [special variable](https://docs.ansible.com/ansible/latest/reference_appendices/special_variables.html#term-omit).
 
 `openhpc_ram_multiplier`: Optional, default `0.95`. Multiplier used in the calculation: `total_memory * openhpc_ram_multiplier` when setting `RealMemory` for the partition in slurm.conf. Can be overriden on a per partition basis using `openhpc_slurm_partitions.ram_multiplier`. Has no effect if `openhpc_slurm_partitions.ram_mb` is set.

defaults/main.yml

@@ -40,8 +40,14 @@ openhpc_default_config:
   PropagateResourceLimitsExcept: MEMLOCK
   Epilog: /etc/slurm/slurm.epilog.clean
   ReturnToService: 2
+openhpc_cgroup_default_config:
+  ConstrainCores: "yes"
+  ConstrainDevices: "yes"
+  ConstrainRAMSpace: "yes"
+  ConstrainSwapSpace: "yes"
 
 openhpc_config: {}
+openhpc_cgroup_config: {}
 openhpc_gres_template: gres.conf.j2
 openhpc_slurm_configless: "{{ 'enable_configless' in openhpc_config.get('SlurmctldParameters', []) }}"
 

tasks/runtime.yml

@@ -105,6 +105,10 @@
     owner: root
     group: root
   when: openhpc_enable.control | default(false) or not openhpc_slurm_configless | bool
+  notify:
+    - Restart slurmctld service
+  register: ohpc_cgroup_conf
+  # NB uses restart rather than reload as this is needed in some cases
 
 - name: Remove local tempfile for slurm.conf templating
   ansible.builtin.file:
@@ -139,7 +143,7 @@
   changed_when: true
   when:
     - openhpc_slurm_control_host in ansible_play_hosts
-    - hostvars[openhpc_slurm_control_host].ohpc_slurm_conf.changed or hostvars[openhpc_slurm_control_host].ohpc_gres_conf.changed # noqa no-handler
+    - hostvars[openhpc_slurm_control_host].ohpc_slurm_conf.changed or hostvars[openhpc_slurm_control_host].ohpc_cgroup_conf.changed or hostvars[openhpc_slurm_control_host].ohpc_gres_conf.changed # noqa no-handler
   notify:
     - Restart slurmd service
 

templates/cgroup.conf.j2

@@ -5,7 +5,8 @@
 # See man slurm.conf and man cgroup.conf for further
 # information on cgroup configuration parameters
 #--
-ConstrainCores=yes
-ConstrainDevices=yes
-ConstrainRAMSpace=yes
-ConstrainSwapSpace=yes
+{% for k, v in openhpc_cgroup_default_config | combine(openhpc_cgroup_config) | items %}
+{%  if v != "omit" %}{# allow removing items using setting key: null #}
+{{ k }}={{ v | join(',') if (v is sequence and v is not string) else v }}
+{%  endif %}
+{% endfor %}