Pressure feedback for LRU map types
summary
A production upgrade exposes packets dropped while a CT map reports CT map insertion failure even though the LRU should evict entries; investigation finds ~40–50k churn on a 250k-sized map and no API signal when updates implicitly evict. Proposed change adds an opt-in pressure feedback flag to the BPF map create path so map update calls can return eviction counts or counters (per-CPU), track shrink frequency and report when global free_target 128 pulls fail.
AI-written summary · about
chapters (11)
- 0:00Introduction to LRU pressure feedback
- 1:05Incident causing packet drops
- 3:55How LRU maps work in BPF
- 9:34LRU map structure deep dive
- 13:10Update mechanism in LRU maps
- 18:27Contention handling in LRU updates
- 22:38Measuring LRU map pressure
- 25:17User-defined statistics for LRU
- 26:37Fast path performance concerns
- 27:41Tracking update rates for LRU maps
- 30:30Wrap-up and future directions
related talks
10mTaming the BPF LRU: Eliminating TCP Resets in Cilium
27mBPF LSM - Updates and What next?
16mBPF Based Telemetry, Metrics, and Accounting on Android
29mcache_ext: Customizing the Page Cache with eBPF
22mTales from an eBPF Program’s Murder Mystery
34mWhat's new in the BPF world?
22mIntroducing PAGEMAP_SCAN IOCTL for Windows syscalls translation...
46mbpftrace internals