ls: document flamegraph

src/uu/ls/BENCHMARKING.md

@@ -32,3 +32,19 @@ This can also be used to compare with version of ls built before your changes to
 
 - Another thing to look at would be system calls count using strace (on linux) or equivalent on other operating systems.
 - Example: `strace -c target/release/coreutils ls -al -R tree`
+
+## Cargo Flamegraph
+
+With Cargo Flamegraph you can easily make a flamegraph of `ls`:
+```bash
+cargo flamegraph --cmd coreutils -- ls [additional parameters]
+```
+
+However, if the `-R` option is given, the output becomes pretty much useless due to recursion. We can fix this by merging all the direct recursive calls with `uniq`, below is a `bash` script that does this.
+```bash
+#!/bin/bash
+
+cargo build --release --no-default-features --features ls
+perf record target/release/coreutils ls "$@"
+perf script | uniq | inferno-collapse-perf | inferno-flamegraph > flamegraph.svg 
+```