Add PGO

.gitattributes

@@ -0,0 +1,3 @@
+# git config merge.theirs.name "Always accept theirs"
+# git config merge.theirs.driver "cp %B %A"
+default.pgo binary merge=theirs

main.go

@@ -14,6 +14,23 @@ import (
 )
 
 func main() {
+	// this runs profiling server. To enable it, build with prof tag
+	//   $ go build -tags prof
+	//
+	// Then you can pass a port using MTG_PROF_PORT environment variable.
+	// Default is 6000
+	//   $ MTG_PROF_PORT=6000 mtg run config.toml
+	//
+	// It will run a webserver with profiling data on
+	// localhost:${MTG_PROF_PORT:-6000}.
+	//
+	// To collect PGO do following:
+	//   $ curl -o default.pgo 'http://localhost:6000/debug/pprof/profile?seconds=300'
+	//
+	// See also https://pkg.go.dev/net/http/pprof
+	//          https://go.dev/blog/pprof
+	runProfile()
+
 	cli := &cli.CLI{}
 	ctx := kong.Parse(cli, kong.Vars{
 		"version": getVersion(),

run_profile.go

@@ -0,0 +1,7 @@
+//go:build !prof
+
+package main
+
+func runProfile() {
+
+}

run_profile_tag_prof.go

@@ -0,0 +1,27 @@
+//go:build prof
+
+package main
+
+import (
+	"fmt"
+	"net"
+	"net/http"
+	_ "net/http/pprof" //nolint: gosec
+	"os"
+)
+
+const DefaultProfPort = "6000"
+
+func runProfile() {
+	port := os.Getenv("MTG_PROF_PORT")
+	if port == "" {
+		port = DefaultProfPort
+	}
+
+	listener, err := net.Listen("tcp", net.JoinHostPort("127.0.0.1", port))
+	if err != nil {
+		panic(err)
+	}
+
+	go http.Serve(listener, nil)
+}