Improve Cinder volume performance with tmpfs for image conversion

This change implements the use of tmpfs for Cinder's image conversion
and encryption processes. Key improvements include:

- Performs image conversion and encryption in memory using tmpfs
  (use from root disk to memory of /var/lib/cinder/conversion volume)
- Reduces IO load on the cinder Docker volume
- Enhances performance for large (virtual size) images
- Improves efficiency of image format conversion and encryption

This optimization is effective when sufficient memory is available on
the cinder-volume host.

Closes-Bug: #2089345
Change-Id: Idea788fdf12f0ae51041b368802b7c958952a847

cinder/Chart.yaml

@@ -14,7 +14,7 @@ apiVersion: v1
 appVersion: v1.0.0
 description: OpenStack-Helm Cinder
 name: cinder
-version: 0.3.26
+version: 0.3.27
 home: https://docs.openstack.org/cinder/latest/
 icon: https://www.openstack.org/themes/openstack/images/project-mascots/Cinder/OpenStack_Project_Cinder_vertical.png
 sources:

cinder/templates/deployment-volume.yaml

@@ -302,7 +302,13 @@ spec:
         - name: pod-shared
           emptyDir: {}
         - name: cinder-conversion
-          emptyDir: {}
+          emptyDir:
+            {{- if .Values.conf.enable_conversion_tmpfs }}
+            medium: Memory
+            sizeLimit: {{ .Values.conf.conversion_tmpfs_size }}
+            {{- else }}
+            {}
+            {{- end }}
         {{- if eq "true" (include "cinder.utils.has_ceph_backend" $envAll) }}
         - name: etcceph
           emptyDir: {}

cinder/values.yaml

@@ -1011,6 +1011,8 @@ conf:
       - volume_type
     volume_type: []
   enable_iscsi: false
+  enable_conversion_tmpfs: false
+  conversion_tmpfs_size: "10Gi"
   cinder_api_uwsgi:
     uwsgi:
       add-header: "Connection: close"

releasenotes/notes/cinder.yaml

@@ -76,4 +76,5 @@ cinder:
   - 0.3.24 Fix volume type create to allow encrypt volume type
   - 0.3.25 Add 2024.2 Ubuntu Jammy overrides
   - 0.3.26 Mount /run/cryptsetup in cinder-volume container
+  - 0.3.27 Add support for using a tmpfs for cinder image conversion
 ...