Kubernetes v1.37 Promotes Memory QoS to Beta, Enabled by Default on Linux cgroup v2

Memory QoS Graduates to Beta

The Memory QoS feature has advanced to Beta status in Kubernetes v1.37 and is now enabled by default. This feature, first introduced as Alpha in v1.22 and expanded in v1.36 with tiered memory reservation, utilizes the memory controller on Linux nodes running cgroup v2 to provide the kernel with better guidance on how to manage container memory.

Default Configuration Changes

With the Beta promotion, the MemoryQoS feature gate is active by default in every v1.37 kubelet. However, the default kubelet configuration does not automatically enable memory throttling or reservation. Specifically, the memoryThrottlingFactor, which previously defaulted to 0.9 in Alpha releases, now defaults to null. This change ensures that upgrading to v1.37 does not alter runtime behavior for existing clusters by automatically throttling workloads that were not previously throttled.

Configuring Memory QoS

Cluster operators must explicitly configure specific behaviors for Memory QoS. To enable memory.high throttling on Burstable and BestEffort containers, operators need to set memoryThrottlingFactor (e.g., to 0.9). To enable tiered memory protection via memory.min and memory.low, memoryReservationPolicy must be set to TieredReservation. If an existing kubelet configuration file already contains an explicit memoryThrottlingFactor value, that value will be preserved during an upgrade.