Container Service for Kubernetes:Compare runC and Sandboxed-Container (runV)

Pod overhead in runV

Each runV pod incurs memory overhead for the lightweight VM and guest components.

Formula: pod overhead memory = 64 MiB + pod memory request × 2%, capped at 512 MiB and floored at 64 MiB.

Total visible memory = pod memory request + pod overhead, minus a small system reservation. The CPU count also differs from the host.

Limitations of runV

runV does not support the following features:

• RootFS I/O throttling: cgroup-based throttling is unavailable for rootfs.

• Disk mounting: Persistent disks cannot be mounted directly.

• Direct log collection: Logtail cannot collect logs directly from the node. Use Logtail Sidecar.

Prerequisites

• Connected to the cluster using kubectl

Create the pod

1. Create a pod that uses runC:

   Note

   Setting runtimeClassName: runc is optional. runC is the default runtime.

   cat <<EOF | kubectl create -f -
   apiVersion: v1
   kind: Pod
   metadata:
     name: busybox-runc
     labels:
       app: busybox-runc
   spec:
     containers:
     - name: busybox
       image: registry.cn-hangzhou.aliyuncs.com/acs/busybox:v1.29.2
       command:
       - tail
       - -f
       - /dev/null
       resources:
         limits:
           cpu: 1000m
           memory: 512Mi
         requests:
           cpu: 1000m
           memory: 512Mi
   EOF

Prerequisites

• Connected to the cluster using kubectl

Create the pod

1. (Optional) Verify the runv RuntimeClass exists in the cluster:

   kubectl get runtimeclass runv -o yaml

   Note

   A runv RuntimeClass is automatically created in ACK clusters with Sandboxed-Container.

2. Create a pod that uses runV:

   Important

   The nodeSelector field is required for Kubernetes versions earlier than 1.16, and optional for 1.16 and later.

   cat <<EOF | kubectl create -f -
   apiVersion: v1
   kind: Pod
   metadata:
     name: busybox-runv
     labels:
       app: busybox-runv
   spec:
     runtimeClassName: runv
     nodeSelector:
       alibabacloud.com/container-runtime: Sandboxed-Container.runv
     containers:
     - name: busybox
       image: registry.cn-hangzhou.aliyuncs.com/acs/busybox:v1.29.2
       command:
       - tail
       - -f
       - /dev/null
       resources:
         limits:
           cpu: 1000m
           memory: 512Mi
         requests:
           cpu: 1000m
           memory: 512Mi
   EOF

3. Verify that the pod is running in a sandbox:

   kubectl get pod busybox-runv -o jsonpath={.spec.runtimeClassName}

   If the output shows runv, the pod runs in a sandbox.

4. Log in to the pod to check CPU and memory:

   kubectl exec -ti pod busybox-runv /bin/sh
   / # cat /proc/meminfo | head -n1
   MemTotal:        1130692 kB
   / # cat /proc/cpuinfo | grep processor
   processor    : 0

   The CPU count differs from the host. Total memory = pod memory + overhead, minus system usage.