Limit parallel jobs to 1 / use in-memeory pch storage

ls/ls.go

@@ -77,6 +77,7 @@ type Config struct {
 	EnableLogging                   bool
 	SkipLibrariesDiscoveryOnRebuild bool
 	DisableRealTimeDiagnostics      bool
+	Jobs                            int
 }
 
 var yellow = color.New(color.FgHiYellow)

ls/lsp_client_clangd.go

@@ -51,8 +51,17 @@ func newClangdLSPClient(logger jsonrpc.FunctionLogger, dataFolder *paths.Path, l
 	args := []string{
 		ls.config.ClangdPath.String(),
 		"-log=verbose",
+		"--pch-storage=memory",
 		fmt.Sprintf(`--compile-commands-dir=%s`, ls.buildPath),
 	}
+	if jobs := ls.config.Jobs; jobs == -1 {
+		// default: limit parallel build jobs to 1
+		args = append(args, "-j", "1")
+	} else if jobs == 0 {
+		// no args: clangd will max out the available cores
+	} else {
+		args = append(args, "-j", fmt.Sprintf("%d", jobs))
+	}
 	if dataFolder != nil {
 		args = append(args, fmt.Sprintf("-query-driver=%s", dataFolder.Join("packages", "**").Canonical()))
 	}

main.go

@@ -56,6 +56,7 @@ func main() {
 	noRealTimeDiagnostics := flag.Bool(
 		"no-real-time-diagnostics", false,
 		"Disable real time diagnostics")
+	jobs := flag.Int("jobs", -1, "Max number of parallel jobs. Default is 1. Use 0 to match the number of available CPU cores.")
 	flag.Parse()
 
 	if *loggingBasePath != "" {
@@ -127,6 +128,7 @@ func main() {
 		CliInstanceNumber:               *cliDaemonInstanceNumber,
 		SkipLibrariesDiscoveryOnRebuild: *skipLibrariesDiscoveryOnRebuild,
 		DisableRealTimeDiagnostics:      *noRealTimeDiagnostics,
+		Jobs:                            *jobs,
 	}
 
 	stdio := streams.NewReadWriteCloser(os.Stdin, os.Stdout)