ceph-common: calculate vm.min_free_kbytes

based on the os memory we calculate the value for vm.min_free_kbytes

Signed-off-by: Sébastien Han <seb@redhat.com>

roles/ceph-common/defaults/main.yml

@@ -295,7 +295,7 @@ os_tuning_params:
   - { name: fs.file-max, value: 26234859 }
   - { name: vm.zone_reclaim_mode, value: 0 }
   - { name: vm.vfs_cache_pressure, value: 50 }
-  - { name: vm.min_free_kbytes, value: 4194303 }
+  - { name: vm.min_free_kbytes, value: "{{ vm_min_free_kbytes }}" }
 
 
 ##########

roles/ceph-common/tasks/misc/system_tuning.yml

@@ -16,6 +16,10 @@
   failed_when: false
   when: disable_swap
 
+- name: calculate vm.min_free_kbytes
+  set_fact:
+    vm_min_free_kbytes: "{{ 4194303 if ansible_memtotal_mb >= 49152 else (ansible_memtotal_mb * 1024 / 100)|int }}"
+
 - name: apply operating system tuning
   sysctl:
     name: "{{ item.name }}"