All news with #lpm trie tag

Deep Dive: BPF LPM Trie Performance and Optimization

🔍 Cloudflare investigated a production soft lockup traced to the Linux BPF LPM trie, a core data structure for IP and IP+Port longest-prefix matching. Benchmarks on 96-core AMD EPYC hardware showed lookups remain relatively fast at modest sizes, but updates, deletes and especially freeing maps degrade severely at scale, causing multi-second CPU stalls and customer packet loss. The post refreshes trie basics, presents measured results (lookups, updates, deletes, free costs), and diagnoses kernel implementation limits — notably binary child pointers, absent level compression, and allocator-induced cache and dTLB pressure — then outlines plans to upstream benchmarks and refactor toward a level-compressed multibit trie to reduce traversal height, cache/TLB misses, and freeing overhead.