3 files changed, 32 insertions, 13 deletions
diff --git a/libgo/go/log/log.go b/libgo/go/log/log.go
index 58b8788..587904b 100644
--- a/libgo/go/log/log.go
+++ b/libgo/go/log/log.go
@@ -72,7 +72,7 @@ func (l *Logger) SetOutput(w io.Writer) {
 
 var std = New(os.Stderr, "", LstdFlags)
 
-// Cheap integer to fixed-width decimal ASCII.  Give a negative width to avoid zero-padding.
+// Cheap integer to fixed-width decimal ASCII. Give a negative width to avoid zero-padding.
 func itoa(buf *[]byte, i int, wid int) {
 	// Assemble decimal in reverse order.
 	var b [20]byte
@@ -89,12 +89,16 @@ func itoa(buf *[]byte, i int, wid int) {
 	*buf = append(*buf, b[bp:]...)
 }
 
+// formatHeader writes log header to buf in following order:
+//   * l.prefix (if it's not blank),
+//   * date and/or time (if corresponding flags are provided),
+//   * file and line number (if corresponding flags are provided).
 func (l *Logger) formatHeader(buf *[]byte, t time.Time, file string, line int) {
 	*buf = append(*buf, l.prefix...)
-	if l.flag&LUTC != 0 {
-		t = t.UTC()
-	}
 	if l.flag&(Ldate|Ltime|Lmicroseconds) != 0 {
+		if l.flag&LUTC != 0 {
+			t = t.UTC()
+		}
 		if l.flag&Ldate != 0 {
 			year, month, day := t.Date()
 			itoa(buf, year, 4)
@@ -143,13 +147,17 @@ func (l *Logger) formatHeader(buf *[]byte, t time.Time, file string, line int) {
 // provided for generality, although at the moment on all pre-defined
 // paths it will be 2.
 func (l *Logger) Output(calldepth int, s string) error {
-	now := time.Now() // get this early.
+	// Get time early if we need it.
+	var now time.Time
+	if l.flag&(Ldate|Ltime|Lmicroseconds) != 0 {
+		now = time.Now()
+	}
 	var file string
 	var line int
 	l.mu.Lock()
 	defer l.mu.Unlock()
 	if l.flag&(Lshortfile|Llongfile) != 0 {
-		// release lock while getting caller info - it's expensive.
+		// Release lock while getting caller info - it's expensive.
 		l.mu.Unlock()
 		var ok bool
 		_, file, line, ok = runtime.Caller(calldepth)
diff --git a/libgo/go/log/log_test.go b/libgo/go/log/log_test.go
index dd16c9d..966fdf3 100644
--- a/libgo/go/log/log_test.go
+++ b/libgo/go/log/log_test.go
@@ -182,3 +182,13 @@ func BenchmarkPrintln(b *testing.B) {
 		l.Println(testString)
 	}
 }
+
+func BenchmarkPrintlnNoFlags(b *testing.B) {
+	const testString = "test"
+	var buf bytes.Buffer
+	l := New(&buf, "", 0)
+	for i := 0; i < b.N; i++ {
+		buf.Reset()
+		l.Println(testString)
+	}
+}
diff --git a/libgo/go/log/syslog/syslog.go b/libgo/go/log/syslog/syslog.go
index df9ffb8..dfd0028 100644
--- a/libgo/go/log/syslog/syslog.go
+++ b/libgo/go/log/syslog/syslog.go
@@ -102,15 +102,16 @@ type netConn struct {
 
 // New establishes a new connection to the system log daemon. Each
 // write to the returned writer sends a log message with the given
-// priority and prefix.
+// priority (a combination of the syslog facility and severity) and
+// prefix tag. If tag is empty, the os.Args[0] is used.
 func New(priority Priority, tag string) (*Writer, error) {
 	return Dial("", "", priority, tag)
 }
 
 // Dial establishes a connection to a log daemon by connecting to
 // address raddr on the specified network. Each write to the returned
-// writer sends a log message with the given facility, severity and
-// tag.
+// writer sends a log message with the facility and severity
+// (from priority) and tag. If tag is empty, the os.Args[0] is used.
 // If network is empty, Dial will connect to the local syslog server.
 // Otherwise, see the documentation for net.Dial for valid values
 // of network and raddr.
@@ -301,10 +302,10 @@ func (n *netConn) close() error {
 	return n.conn.Close()
 }
 
-// NewLogger creates a log.Logger whose output is written to
-// the system log service with the specified priority. The logFlag
-// argument is the flag set passed through to log.New to create
-// the Logger.
+// NewLogger creates a log.Logger whose output is written to the
+// system log service with the specified priority, a combination of
+// the syslog facility and severity. The logFlag argument is the flag
+// set passed through to log.New to create the Logger.
 func NewLogger(p Priority, logFlag int) (*log.Logger, error) {
 	s, err := New(p, "")
 	if err != nil {