libcontainer/cgroups/fs: remove todo since strings.Fields performs well

libcontainer/cgroups/fs/cpuacct.go

@@ -91,7 +91,7 @@ func getCpuUsageBreakdown(path string) (uint64, uint64, error) {
 	if err != nil {
 		return 0, 0, err
 	}
-	// TODO: use strings.SplitN instead.
+
 	fields := strings.Fields(data)
 	if len(fields) < 4 || fields[0] != userField || fields[2] != systemField {
 		return 0, 0, malformedLine(path, file, data)

libcontainer/cgroups/fs/cpuacct_test.go

@@ -95,3 +95,17 @@ func TestCpuacctStatsWithoutUsageAll(t *testing.T) {
 			expectedStats, actualStats.CpuStats.CpuUsage)
 	}
 }
+
+func BenchmarkGetCpuUsageBreakdown(b *testing.B) {
+	path := tempDir(b, "cpuacct")
+	writeFileContents(b, path, map[string]string{
+		"cpuacct.stat": cpuAcctStatContents,
+	})
+
+	for i := 0; i < b.N; i++ {
+		_, _, err := getCpuUsageBreakdown(path)
+		if err != nil {
+			b.Fatal(err)
+		}
+	}
+}

libcontainer/cgroups/fs/util_test.go

@@ -18,7 +18,7 @@ func init() {
 }
 
 // tempDir creates a new test directory for the specified subsystem.
-func tempDir(t *testing.T, subsystem string) string {
+func tempDir(t testing.TB, subsystem string) string {
 	path := filepath.Join(t.TempDir(), subsystem)
 	// Ensure the full mock cgroup path exists.
 	if err := os.Mkdir(path, 0o755); err != nil {
@@ -29,7 +29,7 @@ func tempDir(t *testing.T, subsystem string) string {
 
 // writeFileContents writes the specified contents on the mock of the specified
 // cgroup files.
-func writeFileContents(t *testing.T, path string, fileContents map[string]string) {
+func writeFileContents(t testing.TB, path string, fileContents map[string]string) {
 	for file, contents := range fileContents {
 		err := cgroups.WriteFile(path, file, contents)
 		if err != nil {