[Do Not Merge] POC for Mixed CPU Allocation

[pravk03]

POC for #103

This PR introduces Mixed Allocation Mode to the CPU DRA driver, enabling workloads to request both exclusive and shared CPUs.

Key Principles:

• Any request that goes in the standard container spec is considered as a request for shared CPUs.
• Any claim request is considered as a request for guaranteed exclusive CPUs.
• Relies on KEP-5517 to allow for correct scheduler accounting.

Flags:

• Added --mixed-allocation-mode flag to enable or disable mixed allocation mode.
• Added --disable-node-allocatable-mapping flag to toggle native KEP-5517 scheduler accounting.

DRA Hook:

• Adds a native NodeAllocatable resource mapping to published ResourceSlices. This allows kube-scheduler to track and subtract DRA based CPU requests directly from node allocatable capacity.

NRI Hook:

• Mixed Allocation Mode Implementation:
  • Configured the NRI plugin to inspect container CPU shares at runtime.
  • Containers with shares > 2 are automatically identified as running in mixed mode. Kubelet sets container shares to exactly 2 when standard CPU requests are omitted, as defined in helpers_linux.go.
  • Configures the CPU affinity mask of mixed containers to the union of their dedicated exclusive CPUs and the node's shared CPU pool.
  • Shrinks the shared CPU pool of other standard containers by subtracting exclusive CPUs.

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[ffromani]

/cc

I'm aware this it is a POC and about all the caveats, still very interested in this work! thanks for posting

[swatisehgal]

/cc

[Tal-or]

/cc

[AutuSnow]

/cc

[k8s-ci-robot]

PR needs rebase.

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[pravk03]

I will continue exploring this, but the progress is likely going to be slow as the v1.37 deadlines approach. Additionally, this work depends on KEP-5517 reaching Alpha 2 (hopefully in 1.37) so that Kubelet can set safe pod-level cgroup boundaries and container level limits to include DRA.