AKTS: Sub-Microsecond Kernel Policy Switching for Language-Model Agents

GPU-backed LLM servers multiplex interactive requests with background batch work on the same CPUs; a fixed kernel policy serves one objective and loses the other, so agentic OS control needs to switch scheduler behavior as the workload changes. The hard part is applying the switch safely and fast enough for the kernel: scheduler events occur every 1-10 $\mu$s, and any code running there must satisfy the eBPF verifier. Scalar knobs are fast but limited, while generating eBPF policy code puts compilation, verification and possible rejection on the runtime path. We present AKTS, which verifies a policy library once, at load time, and reduces the agent's runtime action to writing an integer index into an in-kernel array of preverified policies, resolved by a tail call. Because the agent emits an index rather than code, verifier failure is not a runtime outcome. On Linux 6.14, AKTS applies a policy switch in 920 ns (p50); makes an invalid index inert across 60,217 invocations on an attached scheduler; and switches policies in a vLLM workload to capture 97% of a throughput policy's batch work while matching a latency policy's burst response.