Motivation

Demonstrate that FastAggregateVerify is the most expensive call in ethereum beacon light client, though in #13031 Parity team has wrapped some low level host functions for bls-12381 but adding a high level host function specific for it is super helpful.

Benchmark

We add several benchmarks here as following to demonstrate bls_fast_aggregate_verify is the main bottleneck. Test data here is real from goerli network which contains 512 public keys from sync committee.

sync_committee_period_update

Base line benchmark for extrinsic sync_committee_period_update

bls_fast_aggregate_verify

Subfunction of extrinsic sync_committee_period_update which does what FastAggregateVerify requires.

bls_aggregate_pubkey

Subfunction of bls_fast_aggregate_verify which decompress and instantiate G1 pubkeys only.

bls_verify_message

Subfunction of bls_fast_aggregate_verify which verify the prepared signature only.

Result

hardware spec

Run benchmark in a EC2 instance

cargo run --release --bin polkadot-parachain --features runtime-benchmarks -- benchmark machine --base-path /mnt/scratch/benchmark

+----------+----------------+-------------+-------------+-------------------+
| Category | Function       | Score       | Minimum     | Result            |
+===========================================================================+
| CPU      | BLAKE2-256     | 1.08 GiBs   | 1.00 GiBs   | ✅ Pass (107.5 %) |
|----------+----------------+-------------+-------------+-------------------|
| CPU      | SR25519-Verify | 568.87 KiBs | 666.00 KiBs | ❌ Fail ( 85.4 %) |
|----------+----------------+-------------+-------------+-------------------|
| Memory   | Copy           | 13.67 GiBs  | 14.32 GiBs  | ✅ Pass ( 95.4 %) |
|----------+----------------+-------------+-------------+-------------------|
| Disk     | Seq Write      | 334.35 MiBs | 450.00 MiBs | ❌ Fail ( 74.3 %) |
|----------+----------------+-------------+-------------+-------------------|
| Disk     | Rnd Write      | 143.59 MiBs | 200.00 MiBs | ❌ Fail ( 71.8 %) |
+----------+----------------+-------------+-------------+-------------------+

benchmark

cargo run --release --bin polkadot-parachain \
--features runtime-benchmarks \
-- \
benchmark pallet \
--base-path /mnt/scratch/benchmark \
--chain=bridge-hub-rococo-dev \
--pallet=snowbridge_pallet_ethereum_client \
--extrinsic="*" \
--execution=wasm --wasm-execution=compiled \
--steps 50 --repeat 20 \
--output ./parachains/runtimes/bridge-hubs/bridge-hub-rococo/src/weights/snowbridge_pallet_ethereum_client.rs

Weights

extrinsic	minimum execution time benchmarked(us)
sync_committee_period_update	123_126
bls_fast_aggregate_verify	121_083
bls_aggregate_pubkey	90_306
bls_verify_message	28_000

bls_fast_aggregate_verify consumes 98% execution time of sync_committee_period_update
bls_aggregate_pubkey consumes 75% execution time of bls_fast_aggregate_verify
bls_verify_message consumes 23% execution time of bls_fast_aggregate_verify

Conclusion

A high level host function specific for bls_fast_aggregate_verify is super helpful.