Add docs on how to profile with samply and perfmaps (#6720)

* Add docs on how to profile with samply and perfmaps

* add summary entry for samply and specify building from source

docs/SUMMARY.md

@@ -10,6 +10,7 @@
   - [Profiling WebAssembly](./examples-profiling.md)
     - [Profiling with Perf](./examples-profiling-perf.md)
     - [Profiling with VTune](./examples-profiling-vtune.md)
+    - [Profiling with samply](./examples-profiling-samply.md)
     - [Cross-platform Profiling](./examples-profiling-guest.md)
   - [Embedding in Rust](./examples-rust-embed.md)
     - [Hello, world!](./examples-rust-hello-world.md)

docs/examples-profiling-samply.md

@@ -0,0 +1,40 @@
+# Using `samply` on Linux/macOS
+
+One profiler supported by Wasmtime is [`samply`](https://github.com/mstange/samply) for Linux and macOS. As of 17th July 2023, the
+latest version of samply (on crates.io) is 0.11.0 which does not seem to support perfmaps. To use this, you either need a
+newer version of samply, if by the time you read this, a newer version has been released, or you can build samply from source.
+
+## Profiling with `perfmap`
+
+Simple profiling support with `samply` generates a "perfmap" file that the `samply` CLI will
+automatically look for, when running into unresolved symbols. This requires runtime support from
+Wasmtime itself, so you will need to manually change a few things to enable profiling support in
+your application. Enabling runtime support depends on how you're using Wasmtime:
+
+* **Rust API** - you'll want to call the [`Config::profiler`] method with
+  `ProfilingStrategy::PerfMap` to enable profiling of your wasm modules.
+
+* **C API** - you'll want to call the `wasmtime_config_profiler_set` API with a
+  `WASMTIME_PROFILING_STRATEGY_PERFMAP` value.
+
+* **Command Line** - you'll want to pass the `--profile=perfmap` flag on the command
+  line.
+
+Once perfmap support is enabled, you'll use `samply record` like usual to record
+your application's performance.
+
+For example if you're using the CLI, you'll execute:
+
+```sh
+$ samply record wasmtime --profile=perfmap foo.wasm
+```
+
+This will record your application's performance and open the Firefox profiler UI to view the
+results. It will also dump its own profile data to a json file (called `profile.json`) in the current directory.
+
+Note that support for perfmap is still relatively new in Wasmtime, so if you
+have any problems, please don't hesitate to [file an issue]!
+
+[file an issue]: https://github.com/bytecodealliance/wasmtime/issues/new
+
+