[INTERNAL] Document the UI5 Tooling benchmarking process

PRs where this process was already used:
* SAP/ui5-builder#488
* SAP/ui5-builder#390

JIRA: CPOUI5FOUNDATION-261

docs/pages/Troubleshooting.md

@@ -8,3 +8,152 @@ You need to delete the HSTS mapping in [chrome://net-internals/#hsts](chrome://n
 
 ## Issues Not Listed Here
 Please follow our [Contribution Guidelines](https://github.com/SAP/ui5-tooling/blob/master/CONTRIBUTING.md#report-an-issue) on how to report an issue.
+
+## Benchmarking UI5 Tooling
+
+For benchmarking UI5 Tooling we typically make use of the open source tool [hyperfine](https://github.com/sharkdp/hyperfine).
+
+In general we only benchmark calls to the UI5 CLI. However, we might add scripted benchmarks for some components in the future.
+
+The following is a walk-through on how to compare the performance impact of an imaginary change in UI5 Builder project.
+
+### Setup
+
+1. Install [hyperfine](https://github.com/sharkdp/hyperfine#installation)
+1. Prepare the UI5 Tooling projects you want to measure *(optional if your development environment already reflects this)*:
+    1. Start in an empty directory
+        ```sh
+        mkdir ui5-tooling-benchmark && cd ui5-tooling-benchmark/
+        ```
+    1. Clone [UI5 CLI](https://github.com/SAP/ui5-cli)
+        ```sh
+        git clone git@github.com:SAP/ui5-cli.git
+        ```
+    1. Clone [UI5 Builder](https://github.com/SAP/ui5-builder) (or your fork!)
+        ```sh
+        git clone git@github.com:SAP/ui5-builder.git
+        ```
+        Make sure you checkout the `master` branch since we will perform the baseline test first
+    1. Install npm dependencies in both directories
+        ```sh
+        (cd ui5-cli && npm install)
+        (cd ui5-builder && npm install)
+        ```
+    1. Create global npm links for both projects
+        ```sh
+        (cd ui5-cli && npm link)
+        (cd ui5-builder && npm link)
+        ```
+    1. Link UI5 Builder into UI5 CLI
+        ```sh
+        (cd ui5-cli && npm link @ui5/builder)
+        ```
+    1. Verify your setup
+        ```sh
+        ui5 --version
+        ```
+        This should output the version and location of the UI5 CLI you just cloned.
+
+        For example:
+        ```
+        2.6.6 (from /my/home/ui5-tooling-benchmark/ui5-cli/bin/ui5.js)
+        ```
+
+1. Prepare your test project (we chose the [openui5-sample-app](https://github.com/SAP/openui5-sample-app))
+    1. Clone the project
+        ```sh
+        git clone git@github.com:SAP/openui5-sample-app.git
+        ```
+    1. Navigate into the project
+        ```sh
+        cd openui5-sample-app
+        ```
+    1. Install any required npm dependencies
+        ```sh
+        npm install
+        ```
+        Note: We will not link UI5 CLI into the but call the global install directly
+    1. Verify that the previously installed UI5 CLI can be called with the following command
+        ```sh
+        UI5_CLI_NO_LOCAL=X node /my/home/ui5-tooling-benchmark/ui5-cli/bin/ui5.js --version
+        ```
+        On Windows:
+        ```sh
+        set UI5_CLI_NO_LOCAL=X node /my/home/ui5-tooling-benchmark/ui5-cli/bin/ui5.js --version
+        ```
+        *(Replace the path to ui5.js with the one shown in the previous `ui5 --version` output)*
+
+### Benchmark
+
+1. Depending on how reliable you want the measurements, consider preparing your system:
+    1. Connect your computer to a power supply
+    1. Make sure no updates or anti virus scans are taking place
+    1. Close all applications. This includes your IDE since it might start indexing any new files created during the build, thus impacting I/O
+    1. Don't interact with your system wile the benchmark is running
+
+1. Perform the baseline measurement
+    1. In the project, start your first benchmark
+        ```sh
+        hyperfine --warmup 1 \
+        'UI5_CLI_NO_LOCAL=X node /my/home/ui5-tooling-benchmark/ui5-cli/bin/ui5.js build' \
+        --export-markdown ./baseline.md
+        ```
+        On Windows:
+        ```sh
+        hyperfine --warmup 1 \
+        'set UI5_CLI_NO_LOCAL=X node /my/home/ui5-tooling-benchmark/ui5-cli/bin/ui5.js build' \
+        --export-markdown ./baseline.md
+        ```
+    1. Your baseline benchmark is now stored in `baseline.md` and should look similar to this:
+
+        | Command | Mean [s] | Min [s] | Max [s] | Relative |
+        |:---|---:|---:|---:|---:|
+        | `UI5_CLI_NO_LOCAL=X node /my/home/ui5-tooling-benchmark/ui5-cli/bin/ui5.js build` | 1.439 ± 0.036 | 1.400 | 1.507 | 1.00 |
+
+1. Prepare your change
+    1. Switch to the branch that contains your change
+        ```sh
+        (cd ../ui5-builder && git checkout my-change)
+        ```
+    1. If your change requires different npm dependencies, reinstall them
+        ```sh
+        (cd ../ui5-builder && npm install)
+        ```
+    1. The link from UI5 CLI is still in place. However, if you have changes in **multiple** UI5 Tooling modules, you might need to `npm link` those again
+
+1. Perform the change measurement
+    1. In the project, start your second benchmark
+        ```sh
+        hyperfine --warmup 1 \
+        'UI5_CLI_NO_LOCAL=X node /my/home/ui5-tooling-benchmark/ui5-cli/bin/ui5.js build' \
+        --export-markdown ./my_change.md
+        ```
+        On Windows:
+        ```sh
+        hyperfine --warmup 1 \
+        'set UI5_CLI_NO_LOCAL=X node /my/home/ui5-tooling-benchmark/ui5-cli/bin/ui5.js build' \
+        --export-markdown ./my_change.md
+        ```
+    1. Your change's benchmark is now stored in `my_change.md`
+
+### Compile Results
+
+1. Merge both measurements into one markdown
+    1. Either remove the `Relative` column or calculate the relative difference yourself.
+    1. You should end up with a markdown like this:
+        ```md
+        | Command | Mean [s] | Min [s] | Max [s] |
+        |:---|---:|---:|---:|
+        | `UI5_CLI_NO_LOCAL=X node /my/home/ui5-tooling-benchmark/ui5-cli/bin/ui5.js build` | 1.439 ± 0.036 | 1.400 | 1.507 |
+        | `UI5_CLI_NO_LOCAL=X node /my/home/ui5-tooling-benchmark/ui5-cli/bin/ui5.js build` | 1.584 ± 0.074 | 1.477 | 1.680 |
+        ```
+        Rendering like this:
+
+        | Command | Mean [s] | Min [s] | Max [s] |
+        |:---|---:|---:|---:|
+        | `UI5_CLI_NO_LOCAL=X node /my/home/ui5-tooling-benchmark/ui5-cli/bin/ui5.js build` | 1.439 ± 0.036 | 1.400 | 1.507 |
+        | `UI5_CLI_NO_LOCAL=X node /my/home/ui5-tooling-benchmark/ui5-cli/bin/ui5.js build` | 1.584 ± 0.074 | 1.477 | 1.680 |
+
+1. You can now share these results on GitHub or wherever you might need them!
+
+**Happy benchmarking! 🏎**