Skip to content

node-resources.md

Latest commit

 

History

History
46 lines (40 loc) · 2.49 KB

node-resources.md

File metadata and controls

46 lines (40 loc) · 2.49 KB
Raw

Node resources

On startup, vk-cocoon probes the host for real CPU, memory, hugepages, and disk capacity and registers them as the virtual node's Capacity and Allocatable in the Kubernetes API. This replaces hardcoded defaults with values the scheduler can trust.

  • Capacity = raw host resources (runtime.NumCPU, /proc/meminfo MemTotal, statfs total, and hugepages-<size> where the page size is read from /proc/meminfo so a 1Gi-default node is advertised under the right key; a VK_NODE_HUGEPAGES override always advertises under hugepages-2Mi).
  • Allocatable = Capacity minus a reserve fraction (default 20%, override via VK_RESERVE_PERCENT), applied to every resource except pods, which is passed through unreduced. The reserve is accounting only; pair it with cocoon's cgroup_cpus fence to make it physical — the fence keeps VM threads (vCPU, virtio, io_uring workers) off the reserved cores, which then serve vk-cocoon's own probe loops, clone/wake execution, and snapshot transfers.
  • Storage allocatable uses statfs available bytes (Bavail) instead of total — base images, existing COW overlays, and snapshots are naturally excluded from the budget. VK_NODE_STORAGE overrides total and available alike, so the reserve fraction is all that separates them.
  • Values are read once at startup and do not update while vk-cocoon is running; a restart refreshes them (idempotent).
  • Individual resources can be force-overridden via VK_NODE_CPU, VK_NODE_MEM, VK_NODE_STORAGE, VK_NODE_HUGEPAGES, VK_NODE_PODS (see Configuration).

Node labels

vk-cocoon stamps the virtual node with:

Label Source Meaning
cocoonstack.io/pool VK_NODE_POOL (default default) The cocoon node pool CocoonSets select with spec.nodePool
cocoonstack.io/snapshot-cpu-class VK_SNAPSHOT_CPU_CLASS (unset = absent) The guest-visible CPU ABI this node can resume memory snapshots for; see Snapshot CPU compatibility
node-role.kubernetes.io/cocoon-vm always Marks the node as VM-backed

The labels are re-asserted on every process start, on the node template at registration and again on the live node object afterwards — virtual-kubelet only patches the status subresource once the node exists, so a re-stamped or cleared class would otherwise never reach an existing node. Editing the env and restarting is therefore the supported way to reclassify a node.