Managing node labeling for obsolete CPU models - Node maintenance | OpenShift Virtualization

Understanding node labeling for obsolete CPU models
Configuring a config map for obsolete CPU models

You can schedule a virtual machine (VM) on a node where the CPU model and policy attribute of the VM are compatible with the CPU models and policy attributes that the node supports. By specifying a list of obsolete CPU models in a config map, you can exclude them from the list of labels created for CPU models.

Understanding node labeling for obsolete CPU models

To ensure that a node supports only valid CPU models for scheduled VMs, create a config map with a list of obsolete CPU models. When the node-labeller obtains the list of obsolete CPU models, it eliminates those CPU models and creates labels for valid CPU models.

If you do not configure a config map with a list of obsolete CPU models, all CPU models are evaluated for labels, including obsolete CPU models that are not present in your environment.

Through the process of iteration, the list of base CPU features in the minimum CPU model are eliminated from the list of labels generated for the node. For example, an environment might have two supported CPU models: Penryn and Haswell.

If Penryn is specified as the CPU model for minCPU, the node-labeller evaluates each base CPU feature for Penryn and compares it with each CPU feature supported by Haswell. If the CPU feature is supported by both Penryn and Haswell, the node-labeller eliminates that feature from the list of CPU features for creating labels. If a CPU feature is supported only by Haswell and not by Penryn, that CPU feature is included in the list of generated labels. The node-labeller follows this iterative process to eliminate base CPU features that are present in the minimum CPU model and create labels.

The following example shows the complete list of CPU features for Penryn which is specified as the CPU model for minCPU:

Example of CPU features for Penryn

apic
clflush
cmov
cx16
cx8
de
fpu
fxsr
lahf_lm
lm
mca
mce
mmx
msr
mtrr
nx
pae
pat
pge
pni
pse
pse36
sep
sse
sse2
sse4.1
ssse3
syscall
tsc

The following example shows the complete list of CPU features for Haswell:

Example of CPU features for Haswell

aes
apic
avx
avx2
bmi1
bmi2
clflush
cmov
cx16
cx8
de
erms
fma
fpu
fsgsbase
fxsr
hle
invpcid
lahf_lm
lm
mca
mce
mmx
movbe
msr
mtrr
nx
pae
pat
pcid
pclmuldq
pge
pni
popcnt
pse
pse36
rdtscp
rtm
sep
smep
sse
sse2
sse4.1
sse4.2
ssse3
syscall
tsc
tsc-deadline
x2apic
xsave

The following example shows the list of node labels generated by the node-labeller after iterating and comparing the CPU features for Penryn with the CPU features for Haswell:

Example of node labels after iteration

aes
avx
avx2
bmi1
bmi2
erms
fma
fsgsbase
hle
invpcid
movbe
pcid
pclmuldq
popcnt
rdtscp
rtm
sse4.2
tsc-deadline
x2apic
xsave

Configuring a config map for obsolete CPU models

Use this procedure to configure a config map for obsolete CPU models.

Procedure

Create a configmap object, specifying the obsolete CPU models in the obsoleteCPUs array. For example:

apiVersion: v1
kind: configmap
metadata:
  name: cpu-plugin-configmap (1)
data: (2)
  cpu-plugin-configmap:
    obsoleteCPUs: (3)
      - "486"
      - "pentium"
      - "pentium2"
      - "pentium3"
      - "pentiumpro"
    minCPU: "Penryn" (4)

1	Name of the config map.
2	Configuration data.
3	List of obsolete CPU models.
4	Minimum CPU model that is used for basic CPU features.