weights-benchmarking.md

How to benchmarks weights of a Call/Hook/Pallet

1. Create the benchmarking tests, see commit 31057e37 for a complete real example.
2. Run the benchmark test on your local machine: cargo test -p <pallet> --features runtime-benchmarks
3. If the benchmark tests compiles and pass, compile the binary with benchmarks on your local machine: cargo build --release --features runtime-benchmarks
4. Run the benchmarks on your local machine (to test if it work mith a real runtime). The command is: duniter benchmark pallet --chain=CURRENCY-dev --steps=50 --repeat=20 --pallet=pallet_universal_dividend --extrinsic=* --execution=wasm --wasm-execution=compiled --heap-pages=4096 --header=./file_header.txt --output=.
5. If it work, use the generated file content to create or update the WeightInfo trait and the () dummy implementation. Then use the WeightInfo tarit in the real code of the pallet. See 79e0fd4b for a complete real example.
6. Redo steps 3. and 4. on the reference machine.
7. Put the generated file on runtime/common/src/weights and use it in the runtimes configuration. See cee7c3b2 for a complete real example.

Note 1: You Must replace CURRENCY by the currency type, or for ĞDev use directly --chain=dev.

Note2. If the reference machine not support wasmtime, you should replace --wasm-execution=compiled by --wasm-execution=interpreted-i-know-what-i-do.

What the reference machine is?

For now (06/2022), it's a Raspberry Pi 4 Model B - 4GB with an SSD connected via USB3.

To cross-compile the benchmarks binary for armv7:

./scripts/cross-build-arm.sh --features runtime-benchmarks

The cross compiled binary is generated here: target/armv7-unknown-linux-gnueabihf/release/duniter