Add how to run load test comparisons

crates/l2/docs/README.md

@@ -17,12 +17,62 @@ Configuration is done through env vars. A detailed list is available in each par
 
 ## Testing
 
-Load tests are available via L2 CLI. The test take a list of private keys and send a bunch of transactions from each of them to some address. To run them, use the following command:
+Load tests are available via L2 CLI. The test take a list of private keys and send a bunch of transactions from each of them to some address. To run them, use the following command on the root of this repo:
 
 ```bash
-cargo run --bin ethrex_l2 -- test load --path <path-to-pks>
+l2 test load --path ./test_data/private_keys.txt -i 1000 -v  --value 1
 ```
 
-The path should point to a plain text file containing a list of private keys, one per line. Those account must be funded on the L2 network. Use `--help` to see more available options.
+The command will, for each private key in the `private_keys.txt` file, send 1000 transactions with a value of `1` to a random account. If you want to send all transfers to the same account, pass
 
-In the `test_data/` directory, you can find a list of private keys that are funded by the genesis.
+```
+--to <account_address>
+```
+
+The `private_keys.txt` file contains the private key of every account we use for load tests.
+
+Use `--help` to see more available options.
+
+## Load test comparison against Reth
+
+To run a load test on Reth, clone the repo, then run
+
+```
+cargo run --release -- node --chain <path_to_genesis-load-test.json> --dev --dev.block-time 5000ms --http.port 1729
+```
+
+to spin up a reth node in `dev` mode that will produce a block every 5 seconds.
+
+Reth has a default mempool size of 10k transactions. If the load test goes too fast it will reach the limit; if you want to increase mempool limits pass the following flags:
+
+```
+--txpool.max-pending-txns 100000000 --txpool.max-new-txns 1000000000 --txpool.pending-max-count 100000000 --txpool.pending-max-size 10000000000 --txpool.basefee-max-count 100000000000 --txpool.basefee-max-size 1000000000000 --txpool.queued-max-count 1000000000
+```
+
+### Changing block gas limit
+
+By default the block gas limit is the one Ethereum mainnet uses, i.e. 30 million gas. If you wish to change it, just edit the `gasLimit` field in the genesis file (in the case of `ethrex` it's `genesis-l2.json`, in the case of `reth` it's `genesis-load-test.json`). Note that the number has to be passed as a hextstring.
+
+## Flamegraphs
+
+To analyze performance during load tests (both `ethrex` and `reth`) you can use `cargo flamegraph` to generate a flamegraph of the node.
+
+For `ethrex`, you can run the server with:
+
+```
+sudo -E CARGO_PROFILE_RELEASE_DEBUG=true cargo flamegraph --bin ethrex --features dev  --  --network test_data/genesis-l2.json --http.port 1729
+```
+
+For `reth`:
+
+```
+sudo cargo flamegraph --profile profiling -- node --chain <path_to_genesis-load-test.json> --dev --dev.block-time 5000ms --http.port 1729
+```
+
+### Samply
+
+To run with samply, run
+
+```
+samply record ./target/profiling/reth node --chain ../ethrex/test_data/genesis-load-test.json --dev --dev.block-time 5000ms --http.port 1729
+```