bench: Improve usage description.

1 files changed, 34 insertions, 4 deletions

diff --git a/openpgp/benches/README.md b/openpgp/benches/README.md
index 38418da7..eb04543d 100644
--- a/openpgp/benches/README.md
+++ b/openpgp/benches/README.md
@@ -6,22 +6,52 @@ We use [`criterion`](https://crates.io/crates/criterion) as a benchmark framewor
 * produces nice plots
 * and is compatible with stable Rust.
 
-To run the benchmarks, run
+### Usage
+
+To compare your work to `main`:
+
+```
+git switch main
+cargo bench -- --save-baseline main
+git switch branchname
+cargo bench --baseline main
+```
+The html report can then be found at `sequoia/target/criterion/report/index.html`.
+
+You can also create a report for two stored baselines without running the
+benchmarks again:
+```
+cargo bench --load-baseline my_baseline --baseline main
+```
+#### Critmp
+
+Criterion can only include up to two baselines in one report.
+If you'd like to compare more than two stored baselines, or see a report on the
+command line, use [`critcmp`], e.g.
+```
+critcmp my_baseline my_other_baseline main
+```
+
+[`critcmp`]: https://crates.io/crates/critcmp
+
+#### Useful commands
+
+To run the benchmarks:
 ```
 cargo bench
 ```
 
-To run a specific benchmark, run
+To run a specific benchmark:
 ```
 cargo bench -- benchmark_name
 ```
 
-To test the benchmarks, run
+To test the benchmarks:
 ```
 cargo test --benches
 ```
 
-To test a specific benchmark
+To test a specific benchmark:
 ```
 cargo test --benches -- benchmark_name
 ```