Balloons Policy

The Balloons policy groups containers into CPU pools called balloons. A container runs on the CPUs of its balloon, optionally on free CPUs outside balloons, but never on CPUs of other balloons. Each balloon can be tuned on its own: how many CPUs, at what frequency, which C-states, how they are scheduled, and which devices they sit close to.

Reach for Balloons when you need explicit control over how groups of workloads share a node. For automatic alignment with no per-workload setup, see Topology-aware instead.

A balloon can hold containers of any QoS class: BestEffort, Burstable, or Guaranteed. Its tuning (frequency, C-states, Priority Core Turbo (PCT), IRQ affinity, scheduling) applies to all of them. This is a key difference from Topology-aware, whose CPU tuning, PCT, and IRQ affinity apply only to Guaranteed containers with exclusive CPUs.

What it solves

Each item below is a common host-level tuning task and where Balloons handles it in Kubernetes. Follow the links for the configuration.

• Isolate a latency-critical workload. Give it dedicated CPUs, stop it sharing L2 cache with other workloads, and disable deep C-states so cores do not sleep. See the upstream latency-critical recipe.

• Run hot serial threads at top turbo. Put them on Priority Core Turbo high-priority cores while the rest of the node stays at base frequency. See the PCT guide for the hardware side and the upstream PCT quick start for the Kubernetes side.

• Get more memory bandwidth. Spread a balloon’s CPUs across NUMA nodes or sockets to use more memory channels, or keep it local for lowest latency. See the upstream memory bandwidth recipe and the NUMA guide.

• Let bursty workloads use idle CPUs safely. A balloon can borrow otherwise idle CPUs within a core, L2 domain, NUMA node, or package, and you control which workload types share a physical core. See the upstream hyper-thread sharing recipe.

• Set frequency, governor, EPP, and C-states per group. The host-wide knobs in the common recommendations become per-balloon CPU classes. See the upstream CPU tuning options.

• Apply real-time scheduling and I/O priority. Assign a balloon a scheduling class such as SCHED_FIFO with a priority, plus an I/O class and priority. Useful for control loops and other real-time work. See the upstream CPU tuning options.

• Steer IRQs off critical cores. Move device interrupts away from the CPUs running a latency-critical balloon.

• Keep CPUs close to a device. Place a balloon on the CPUs nearest a GPU, NIC, or accelerator to cut access latency. Useful for AI inference and packet processing.

Try it

The upstream PCT quick start is the fastest hands-on path and shows a measurable difference between tuned and untuned pods. For a local isolation example, see the quick start in this section.

Reference

Full configuration, all balloon and CPU-class fields, and more recipes are in the upstream Balloons documentation.