GoKawiilBomfather cuts eBPF security agent's kernel CPU usage by 90% via inode-level policy caching
The team behind the open-source Bomfather eBPF security agent found that the costliest part of their file-access enforcement wasn't applying allow/deny decisions, but repeatedly walking parent directories to determine which path-based policy applied to a given file. By caching the resolved policy per inode instead of recalculating it on every file open, they cut kernel-side CPU overhead by roughly 90%, particularly benefiting workloads like databases that repeatedly access the same file paths.
GoKawiil's interpretation of the reporting above, not reported fact.
Security monitoring tools built on eBPF are prized for low overhead, but naive path-resolution logic can quietly become a performance bottleneck under high-churn workloads like databases. This memoization technique shows a broadly applicable pattern for eBPF developers: cache expensive per-object lookups (like policy resolution) at the kernel level rather than recomputing them on every syscall, which can make security enforcement viable for latency-sensitive production systems.
- Bomfather's eBPF agent was spending most CPU cycles walking directory trees to match file-access policies, not enforcing them.
- Caching policy decisions by inode reduced kernel CPU cost by about 90% for repeated file accesses.
- The full implementation is open source on GitHub, offering a reusable pattern for optimizing eBPF-based security tools.
Source: nathannaveen.dev, 2026-09-14
Published there as: “Dropping eBPF CPU Cost by About 90% with Memoization (Not AI Gen)”
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