Re-thinking termination guarantee of eBPF

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Virginia Tech


In the rapidly evolving landscape of BPF as kernel extensions, where the industry is deploying an increasing count of simultaneously running BPF programs, the need for accounting BPF- induced overhead on latency-sensitive kernel functions is becoming critical. We also find that eBPF's termination guarantee is insufficient to protect systems from BPF programs running extraordinarily long due to compute-heavy operations and runtime factors such as contention. Operators lack a crucial mechanism to identify and avoid installing long-running BPF programs while also requiring a mechanism to abort such BPF programs when found to be adding high latency overhead on performance-critical kernel functions. In this work, we propose a runtime estimator and a dynamic termination mechanism to solve these two issues, respectively. We use a hybrid of static and dynamic analysis to provide a runtime range that we demonstrate to encompass the actual runtime of the BPF program. For safe BPF termination, we propose a short-circuiting approach to skip all costly operations and quickly reach completion. We evaluate the proposed solutions to find the obtained performance estimate as too broad, but when paired with the dynamic termination, can be used by a BPF Orchestrator to impose policies on the overhead due to BPF programs in a call path. The proposed dynamic termination solution has zero overhead on BPF programs for no-termination cases while having a verification overhead proportional to the number of helper calls in a BPF program. In the future, we aim to make BPF execution atomic to guarantee that kernel objects modified within a BPF program are always left in a consistent state in the event of program termination.



eBPF, performance prediction, Linux, termination