[docs] update notes about dotnet-trace and dotnet-gcdump (#8713)

Context: dotnet/diagnostics#4337

Update `Documentation/guides/tracing.md` to be up-to-date for .NET 8.

Documentation/guides/tracing.md

@@ -1,91 +1,138 @@
-# Using a device connected via USB
+# Tracing .NET Android Applications
 
-## Startup profiling
-### Set up reverse port forwarding:
+Attaching `dotnet-trace` to a .NET Android application, allows you to
+get profiling information in formats like `.nettrace` and
+`.speedscope`. These give you CPU sampling information about the time
+spent in each method in your application. This is quite useful for
+finding *where* time is spent in the startup or general performance of
+your .NET applications.
 
-Note that you can skip this step if the Android application is running on an
-Android emulator; it is only required for physical Android devices.
+To use `dotnet-trace` on Android, the following tools/components work
+together to make this happen:
 
-```sh
-$ adb reverse tcp:9000 tcp:9001
-```
-This will forward port 9000 on device to port 9001.
+* [`dotnet-trace`][dotnet-trace] itself is a .NET global tool.
 
-_Alternatively:_
-```sh
-$ adb reverse tcp:0 tcp:9001
-43399
-```
-This will allocate a random port on remote and forward it to port 9001 on the host. The forwarded port is printed by adb
+* [`dotnet-dsrouter`][dotnet-dsrouter] is a .NET global tool that
+  forwards a connection from a remote Android or iOS device or
+  emulator to a local port on your development machine.
 
-### Configure the device so that the profiled app suspends until tracing utility connects
+* [`dotnet-gcdump`][dotnet-gcdump] is a .NET global tool that can be
+  used to collect memory dumps of .NET applications.
 
-```sh
-$ adb shell setprop debug.mono.profile '127.0.0.1:9000,suspend'
-```
+* The Mono Diagnostic component, `libmono-component-diagnostics_tracing.so`,
+  is included in the application and is used to collect the trace data.
+
+See the [`dotnet-trace` documentation][dotnet-trace] for further details about its usage.
 
-### Install `dotnet-dsrouter`
+[dotnet-trace]: https://learn.microsoft.com/dotnet/core/diagnostics/dotnet-trace
+[dotnet-dsrouter]: https://learn.microsoft.com/dotnet/core/diagnostics/dotnet-dsrouter
+[dotnet-gcdump]: https://learn.microsoft.com/dotnet/core/diagnostics/dotnet-gcdump
 
-Generally, you can use a stable `dotnet-dsrouter` from NuGet:
+## Install .NET Global Tools
+
+Generally, you can install the required tooling such as:
 
 ```sh
+$ dotnet tool install -g dotnet-trace
+You can invoke the tool using the following command: dotnet-trace
+Tool 'dotnet-trace' was successfully installed.
 $ dotnet tool install -g dotnet-dsrouter
 You can invoke the tool using the following command: dotnet-dsrouter
 Tool 'dotnet-dsrouter' was successfully installed.
+$ dotnet tool install -g dotnet-gcdump
+You can invoke the tool using the following command: dotnet-gcdump
+Tool 'dotnet-gcdump' was successfully installed.
 ```
 
-Or use a build from the nightly feed `https://aka.ms/dotnet-tools/index.json`:
+You can also install prerelease builds from the nightly feed
+`https://aka.ms/dotnet-tools/index.json`:
 
 ```sh
 $ dotnet tool install -g dotnet-dsrouter --add-source=https://aka.ms/dotnet-tools/index.json --prerelease
+You can invoke the tool using the following command: dotnet-dsrouter
+Tool 'dotnet-dsrouter' was successfully installed.
 ```
 
-### Start the tracing router/proxy on host
+## Configuration & Setup
 
-For profiling an Android application running on an Android emulator:
-```sh
-$ dotnet-dsrouter android-emu --verbose debug
-WARNING: dotnet-dsrouter is a development tool not intended for production environments.
+### Running `dotnet-dsrouter` on the Host
+
+For profiling an Android application running on an Android *emulator*:
 
-Start an application on android emulator with one of the following environment variables set:
+```sh
+$ dotnet-dsrouter android-emu
+How to connect current dotnet-dsrouter pid=1234 with android emulator and diagnostics tooling.
+Start an application on android emulator with ONE of the following environment variables set:
+[Default Tracing]
 DOTNET_DiagnosticPorts=10.0.2.2:9000,nosuspend,connect
+[Startup Tracing]
 DOTNET_DiagnosticPorts=10.0.2.2:9000,suspend,connect
+Run diagnotic tool connecting application on android emulator through dotnet-dsrouter pid=1234:
+dotnet-trace collect -p 1234
+See https://learn.microsoft.com/dotnet/core/diagnostics/dotnet-dsrouter for additional details and examples.
+
+info: dotnet-dsrouter-1234[0]
+      Starting dotnet-dsrouter using pid=1234
+info: dotnet-dsrouter-1234[0]
+      Starting IPC server (dotnet-diagnostic-dsrouter-1234) <--> TCP server (127.0.0.1:9000) router.
+```
 
-info: dotnet-dsrouter[0]
-      Starting dotnet-dsrouter using pid=21352
-dbug: dotnet-dsrouter[0]
-      Using default IPC server path, dotnet-diagnostic-dsrouter-21352.
-dbug: dotnet-dsrouter[0]
-      Attach to default dotnet-dsrouter IPC server using --process-id 21352 diagnostic tooling argument.
-info: dotnet-dsrouter[0]
-      Starting IPC server (dotnet-diagnostic-dsrouter-21352) <--> TCP server (127.0.0.1:9000) router.
-dbug: dotnet-dsrouter[0]
-      Trying to create new router instance.
-dbug: dotnet-dsrouter[0]
-      Waiting for a new TCP connection at endpoint "127.0.0.1:9000".
-dbug: dotnet-dsrouter[0]
-      Waiting for new ipc connection at endpoint "dotnet-diagnostic-dsrouter-21352".
+For profiling an Android application running on an Android *device*:
+
+```sh
+# `adb reverse` is required when using hardware devices
+$ adb reverse tcp:9000 tcp:9001
+$ dotnet-dsrouter android
+How to connect current dotnet-dsrouter pid=1234 with android device and diagnostics tooling.
+Start an application on android device with ONE of the following environment variables set:
+[Default Tracing]
+DOTNET_DiagnosticPorts=127.0.0.1:9000,nosuspend,connect
+[Startup Tracing]
+DOTNET_DiagnosticPorts=127.0.0.1:9000,suspend,connect
+Run diagnotic tool connecting application on android device through dotnet-dsrouter pid=1234:
+dotnet-trace collect -p 1234
+...
 ```
 
-### For Android devices
+### Android System Properties
 
-For profiling an Android application running on an Android device:
+Note the log message that `dotnet-dsrouter` prints that mentions
+`$DOTNET_DiagnosticPorts`. `$DOTNET_DiagnosticPorts` is an environment
+variable that could be defined in an `@(AndroidEnvironment)` file, but
+it is simpler to use the `debug.mono.profile` Android system property.
+Android system properties can be used without rebuilding the app.
 
+For emulators, `$DOTNET_DiagnosticPorts` should specify an IP address
+of 10.0.2.2:
+
+```sh
+$ adb shell setprop debug.mono.profile '10.0.2.2:9000,suspend,connect'
 ```
-$ dotnet-dsrouter server-server -tcps 127.0.0.1:9001 --verbose debug
+
+For devices, `$DOTNET_DiagnosticPorts` should specify an IP address of
+127.0.0.1, and the port number should be the [port used used with adb
+reverse](#start-the-tracing-routerproxy-on-host), e.g:
+
+```sh
+# `adb reverse` is required when using hardware devices
+$ adb reverse tcp:9000 tcp:9001
+$ adb shell setprop debug.mono.profile '127.0.0.1:9000,suspend,connect'
 ```
 
-Eventually, we will be able to simply do `dotnet-dsrouter android` when
-[dotnet/diagnostics#4337][4337] is resolved. `adb reverse tcp:9000 tcp:9001` is
-also currently required as mentioned above.
+`suspend` is useful as it blocks application startup, so you can
+actually `dotnet-trace` startup times of the application.
+
+If you are wanting to collect a `gcdump` or just get things working,
+try `nosuspend` instead. See the [`dotnet-dsrouter`
+documentation][nosuspend] for further information.
 
-[4337]: https://github.com/dotnet/diagnostics/issues/4337
+[nosuspend]: https://learn.microsoft.com/dotnet/core/diagnostics/dotnet-dsrouter#collect-a-trace-using-dotnet-trace-from-a-net-application-running-on-android
 
-### Start the tracing client
+### Running `dotnet-trace` on the Host
 
 First, run `dotnet-trace ps` to find a list of processes:
 
-```
+```sh
 > dotnet-trace ps
  38604  dotnet-dsrouter  C:\Users\myuser\.dotnet\tools\dotnet-dsrouter.exe  "C:\Users\myuser\.dotnet\tools\dotnet-dsrouter.exe" android-emu --verbose debug
 ```
@@ -95,7 +142,7 @@ connect *through it* appropriately.
 
 Using the process ID from the previous step, run `dotnet-trace collect`:
 
-```
+```sh
 $ dotnet-trace collect -p 38604 --format speedscope
 No profile or providers specified, defaulting to trace profile 'cpu-sampling'
 
@@ -107,15 +154,23 @@ Waiting for connection on /tmp/maui-app
 Start an application with the following environment variable: DOTNET_DiagnosticPorts=/tmp/maui-app
 ```
 
-The `--format` argument is optional and it defaults to `nettrace`. However, `nettrace` files can be viewed only with
-Perfview on Windows, while the speedscope JSON files can be viewed "on" Unix by uploading them to https://speedscope.app
+The `--format` argument is optional and it defaults to `nettrace`.
+However, `nettrace` files can be viewed only with Perfview or Visual
+Studio on Windows, while the speedscope JSON files can be viewed "on"
+Unix by uploading them to [https://speedscope.app/][speedscope].
 
-### Compile and run the application
+[speedscope]: https://speedscope.app/
 
-```
+### Running the .NET Android Application
+
+`$(AndroidEnableProfiler)` must be set to `true` as it includes the
+Mono diagnostic component in the application. This component is the
+`libmono-component-diagnostics_tracing.so` native library.
+
+```sh
 $ dotnet build -f net8.0-android -t:Run -c Release -p:AndroidEnableProfiler=true
 ```
-_NOTE: `-f net8.0-android` is only needed for projects with multiple `$(TargetFrameworks)`._
+*NOTE: `-f net8.0-android` is only needed for projects with multiple `$(TargetFrameworks)`.*
 
 Once the application is installed and started, `dotnet-trace` should show something similar to:
 
@@ -141,14 +196,8 @@ directory.
 
 ## How to get GC memory dumps?
 
-If running on desktop, you can use the `dotnet-gcdump` global tool.
-This can be installed via:
-
-```dotnetcli
-$ dotnet tool install --global dotnet-gcdump
-```
-
-To use it, for example:
+If running on desktop, you can use the `dotnet-gcdump` global tool for
+local processes. For example:
 
 ```sh
 # `hw-readline` is a standard Hello World, with a `Console.ReadLine()` at the end
@@ -167,6 +216,7 @@ $ dotnet-gcdump collect -p 33972
 Writing gcdump to '.../hw-readline/20230314_113922_33972.gcdump'...
 	Finished writing 5624131 bytes.
 ```
+
 See the [`dotnet-gcdump` documentation][dotnet-gcdump]
 for further details about its usage.
 
@@ -188,6 +238,9 @@ $ dotnet-gcdump collect -p 38604
 
 This will create a `*.gcdump` file in the current directory.
 
+Note that using `nosuspend` in the `debug.mono.profile` property is
+useful, as it won't block application startup.
+
 ## Memory Dumps for Android in .NET 7
 
 In .NET 7, we have to use th older, more complicated method for collecting
@@ -228,12 +281,11 @@ This saves a `foo.gcdump` that you can open in Visual Studio.
 See the [dotnet/runtime documentation][gc-dumps-on-mono] for
 additional details.
 
-[dotnet-gcdump]: https://learn.microsoft.com/dotnet/core/diagnostics/dotnet-gcdump
 [mono-events]: https://github.com/dotnet/runtime/blob/c887c92d8af4ce65b19962b777f96ae8eb997a42/src/coreclr/vm/ClrEtwAll.man#L7433-L7468
 [dotnet-trace-help]: https://github.com/dotnet/diagnostics/blob/6d755e8b5435b1380c118e9d81e075654b0330c9/documentation/dotnet-trace-instructions.md#dotnet-trace-help
 [gc-dumps-on-mono]: https://github.com/dotnet/runtime/blob/728fd85bc7ad04f5a0ea2ad0d4d8afe371ff9b64/docs/design/mono/diagnostics-tracing.md#collect-gc-dumps-on-monovm
 
-## How to `dotnet trace` our build?
+## How to `dotnet trace` a Build?
 
 Setting this up is easy, the main issue is there end up being
 potentially *a lot* of threads (30-40) depending on the build.