Enable huge pages on a active instance in Openstack
Environment
- Red Hat OpenStack Platform 16
Issue
Instance was created without huge pages and setting the property hw:mem_page_size
of the server don't have effect, even after a hard reboot.
Resolution
Create a new flavor (with huge pages), resize the instance and reboot it as below:
(overcloud) [stack@director ~]$ openstack flavor create --ram <size-mb> --disk <size-gb> --vcpus <no_reserved_vcpus> huge_pages_flavor
(overcloud) [stack@director ~]$ openstack flavor set huge_pages_flavor --property hw:mem_page_size=large
(overcloud) [stack@director ~]$ openstack server resize --wait --flavor huge_pages_flavor <instance>
(overcloud) [stack@director ~]$ openstack server resize --confirm <instance>
(overcloud) [stack@director ~]$ openstack server reboot --hard --wait <instance>
Root Cause
Huge pages cannot be added directly to the instance after it was created. This feature need to be enabled in flavor.
Diagnostic Steps
It's possible to check the configuration by the commands below:
[heat-admin@compute0 ~]# sudo grep Huge /proc/meminfo
[heat-admin@compute0 ~]# sudo numastat -m
(overcloud) [stack@director ~]$ openstack flavor show <flavor>
(overcloud) [stack@director ~]$ openstack server show <instance>
[heat-admin@compute0]# sudo podman exec -it nova_libvirt virsh dumpxml instance-00000001
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