Binding CPU Cores¶
By default, kubelet uses CFS quotas to enforce pod CPU limits. When the node runs many CPU-bound pods, the workload can move to different CPU cores depending on whether the pod is throttled and which CPU cores are available at scheduling time. Many workloads are not sensitive to this migration and thus work fine without any intervention. Some applications are CPU-sensitive. They are sensitive to:
CPU throttling
Context switching
Processor cache misses
Cross-socket memory access
Hyperthreads that are expected to run on the same physical CPU card
If your workloads are sensitive to any of these items and CPU cache affinity and scheduling latency significantly affect workload performance, kubelet allows alternative CPU management policies to determine some placement preferences on the node. The CPU manager preferentially allocates resources on a socket and full physical cores to avoid interference.
Binding CPU Cores to a Pod¶
Prerequisites:
The static core binding policy is enabled on the node. For details, see Enabling the CPU Management Policy.
Both requests and limits must be set in the pod definition and their values must be the same.
The value of requests must be an integer for the container.
For an init container, it is recommended that you set its requests to the same as that of the service container. Otherwise, the service container does not inherit the CPU allocation result of the init container, and the CPU manager reserves more CPU resources than supposed. For more information, see App Containers can't inherit Init Containers CPUs - CPU Manager Static Policy.
You can use Scheduling Policy (Affinity/Anti-affinity) to schedule the configured pods to the nodes where the static CPU policy is enabled. In this way, cores can be bound.
Enabling the CPU Management Policy¶
A CPU management policy is specified by the kubelet flag --cpu-manager-policy. The following policies are supported:
Disabled (none): the default policy. The none policy explicitly enables the existing default CPU affinity scheme, providing no affinity beyond what the OS scheduler does automatically.
Enabled (static): The static policy allows containers in Guaranteed pods with integer CPU requests to be granted increased CPU affinity and exclusivity on the node.
When creating a cluster, you can configure the CPU management policy in Advanced Settings, as shown in the following figure.
You can also configure the policy in a node pool. The configuration will change the kubelet flag --cpu-manager-policy on the node. Log in to the CCE console, click the cluster name, access the cluster details page, and choose Nodes in the navigation pane. On the page displayed, click the Node Pools tab. Choose More > Manage in the Operation column of the target node pool, and change the value of cpu-manager-policy to static.
Pod Configuration¶
For CPU, both requests and limits must be set to the same, and requests must be an integer.
kind: Deployment
apiVersion: apps/v1
metadata:
name: test
spec:
replicas: 1
selector:
matchLabels:
app: test
template:
metadata:
labels:
app: test
spec:
containers:
- name: container-1
image: nginx:alpine
resources:
requests:
cpu: 2 # The value must be an integer and must be the same as that in limits.
memory: 2048Mi
limits:
cpu: 2 # The value must be an integer and must be the same as that in requests.
memory: 2048Mi
imagePullSecrets:
- name: default-secret