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packages/udp-core/benches/ban_service_benchmark.rs
packages/udp-core/src/services/banning.rs
docs/issues/closed/2114-consider-removing-bloom-filter/ISSUE.md

UDP Ban Service Benchmarking

Purpose

This benchmark measures the exact-map BanService implementation. Its pre-removal baseline compared the former two-level implementation with an exact-map reference that preserves the production threshold rule: an address is banned only when its exact error count is greater than the configured limit.

The comparison established that the Bloom filter provided no measured CPU benefit. The retained benchmark protects the exact-map counter from future performance regressions. It measures only counter operations; it does not measure UDP socket I/O, Tokio lock contention, event handling, metrics, or end-to-end tracker throughput.

Run The Benchmark

From the repository root, run:

cargo bench -p torrust-tracker-udp-core --bench ban_service_benchmark

Criterion prints 95% confidence intervals and writes detailed HTML reports and raw samples to target/criterion/. These build outputs are intentionally not version-controlled.

For a before-and-after comparison, run the command on a clean checkout of each revision on the same machine. Close unnecessary background workloads, keep the same power and CPU-scaling policy, retain the raw Criterion output, and compare the reported confidence intervals rather than a single run's point estimate.

Workloads

The benchmark source is benches/ban_service_benchmark.rs. It uses the following deterministic workload matrix:

  • Counter limit: 10 errors.
  • Repeated updates: 10,000 increments for one address per measured batch.
  • Distinct updates: 10,000 unique addresses per measured batch.
  • Address families: IPv4 and IPv6.
  • Lookup states: below threshold (9), at threshold (10), and above threshold (11) errors.
  • Lookup cardinalities: 10, 1,000, and 10,000 exact-map entries.

BanService uses HashMap<IpAddr, u32> with the existing strictly-greater-than threshold rule.

Baseline Results

This initial baseline was collected on 2026-08-29 with:

  • OS: Linux 7.0.0-30-generic x86_64 GNU/Linux.
  • CPU: AMD Ryzen 9 7950X 16-Core Processor, 32 logical CPUs.
  • Compiler: rustc 1.98.0 (88d9e12ae 2026-08-18), LLVM 22.1.8.
  • Benchmark framework: Criterion 0.5.1.

Criterion reported these 95% confidence intervals. Each increment result covers the complete 10,000-request batch.

Operation Address family Current two-level service Exact-map reference Relative result
Repeated increase_counter IPv4 860.38-864.08 us 97.553-97.758 us Exact map about 8.8x faster
Repeated increase_counter IPv6 795.16-797.68 us 125.22-125.38 us Exact map about 6.4x faster
Distinct increase_counter IPv4 1.1150-1.1185 ms 279.58-280.66 us Exact map about 4.0x faster
Distinct increase_counter IPv6 1.1365-1.1375 ms 329.81-330.77 us Exact map about 3.4x faster
is_banned IPv4, all states/cardinalities 73.530-87.815 ns 9.2101-9.3379 ns Exact map about 7.9-9.5x faster
is_banned IPv6, all states/cardinalities 64.640-78.360 ns 11.194-11.502 ns Exact map about 5.7-7.0x faster

The exact-map lookup time remained effectively stable over the tested cardinalities. The current path was slower even below and at the threshold, where its Bloom estimate avoids the exact-map lookup.

Pre-removal Conclusion

The benchmark provides no performance reason to retain the Bloom filter. The exact-map reference was faster in every measured counter operation, including the sub-threshold lookup path that the filter was intended to optimize.

The approved decision removes bloom and retains the exact map. The map was already unbounded before this change because the former implementation inserted every invalid source into it. A bounded-memory admission-control or rate-limit design remains deferred to a future issue if operational evidence requires it. See ../adrs/20260829204258_use_exact_ip_counters_for_udp_banning.md.