perf: add synthetic benchmark (#7189)

* perf: add synthetic benchmark

Signed-off-by: Javier Chávarri <[email protected]>

.github/workflows/melange-bench.yml → .github/workflows/bench.yml

@@ -1,10 +1,11 @@
-name: Melange demo app build time benchmark
+name: Build time benchmarks
 
 # Do not run this workflow on pull request since this workflow has permission to modify contents.
 on:
   push:
     branches:
       - main
+      - bench/add-synthetic-benchmark
 
 permissions:
   # deployments permission to deploy GitHub pages website
@@ -65,7 +66,7 @@ jobs:
 
       - name: Run pupilfirst benchmark
         working-directory: pupilfirst
-        run: ../bench/gen-melange-benchmark.sh 'opam exec -- ../_boot/dune.exe build --root=. @main' 'opam exec -- ../_boot/dune.exe clean --root=.' 'pupilfirst build time (${{ runner.os }})' > melange-benchmark-result.json
+        run: ../bench/gen-benchmark.sh 'opam exec -- ../_boot/dune.exe build --root=. @main' 'opam exec -- ../_boot/dune.exe clean --root=.' 'pupilfirst build time (${{ runner.os }})' > melange-benchmark-result.json
 
       - name: Print pupilfirst benchmark results
         working-directory: pupilfirst
@@ -82,7 +83,38 @@ jobs:
           github-token: ${{ secrets.GITHUB_TOKEN }}
           auto-push: true
           # Ratio indicating how worse the current benchmark result is.
-          # 150% means if last build took 40s and current takes 50s, it will trigger an alert
+          # 150% means if last build took 40s and current takes >60s, it will trigger an alert
+          alert-threshold: "150%"
+          fail-on-alert: true
+          # Enable alert commit comment
+          comment-on-alert: true
+          # Mention @jchavarri in the commit comment
+          alert-comment-cc-users: '@jchavarri'
+
+      - name: Create synthetic benchmark
+        working-directory: bench
+        run: opam exec -- ../_boot/dune.exe exec ./gen_synthetic.exe -- -n 2000 synthetic
+
+      - name: Run synthetic benchmark
+        working-directory: bench/synthetic
+        run: ../gen-benchmark.sh 'opam exec -- ../../_boot/dune.exe build @all' 'opam exec -- ../../_boot/dune.exe clean' 'synthetic build time (${{ runner.os }})' > synthetic-benchmark-result.json
+
+      - name: Print synthetic benchmark results
+        working-directory: bench/synthetic
+        run: |
+          cat bench.json
+          cat synthetic-benchmark-result.json
+
+      - name: Store synthetic benchmark result
+        uses: benchmark-action/github-action-benchmark@v1
+        with:
+          name: Synthetic Benchmark
+          tool: "customSmallerIsBetter"
+          output-file-path: bench/synthetic/synthetic-benchmark-result.json
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+          auto-push: true
+          # Ratio indicating how worse the current benchmark result is.
+          # 150% means if last build took 40s and current takes >60s, it will trigger an alert
           alert-threshold: "150%"
           fail-on-alert: true
           # Enable alert commit comment

bench/dune

@@ -1,8 +1,14 @@
 (executable
  (name bench)
+ (modules bench)
  (libraries dune_stats chrome_trace stdune fiber dune_engine dune_util))
 
 (rule
  (alias bench)
  (action
   (run ./bench.exe %{bin:dune})))
+
+(executable
+ (modules gen_synthetic)
+ (libraries unix)
+ (name gen_synthetic))

bench/gen_synthetic.ml

@@ -0,0 +1,33 @@
+open Printf
+
+let write_modules basedir num_modules =
+  for current_mod = 1 to num_modules do
+    let modname = sprintf "%s/m_%d" basedir current_mod in
+    let f = open_out (sprintf "%s.ml" modname) in
+    close_out f
+  done
+
+let dune = {|
+(library
+ (name test))
+|}
+
+let write basedir =
+  let () = Unix.mkdir basedir 0o777 in
+  let f = open_out (Filename.concat basedir "dune") in
+  output_string f dune;
+  let () = close_out f in
+  write_modules basedir
+
+let () =
+  let basedir = ref "." in
+  let num_modules = ref 0 in
+  Arg.parse
+    [ ( "-n"
+      , Arg.Int (fun n -> num_modules := n)
+      , "<n>  number of modules to include in the synthetic library" )
+    ]
+    (fun d -> basedir := d)
+    (sprintf "usage: %s [basedir]" (Filename.basename Sys.argv.(0)));
+
+  write !basedir !num_modules