daemon/logs: lower allocations in loop

Docker-DCO-1.1-Signed-off-by: Cristian Staretu <cristian.staretu@gmail.com> (github: unclejack)

daemon/logs.go

@@ -88,9 +88,8 @@ func (daemon *Daemon) ContainerLogs(job *engine.Job) engine.Status {
 				cLog = tmp
 			}
 			dec := json.NewDecoder(cLog)
+			l := &jsonlog.JSONLog{}
 			for {
-				l := &jsonlog.JSONLog{}
-
 				if err := dec.Decode(l); err == io.EOF {
 					break
 				} else if err != nil {
@@ -102,11 +101,12 @@ func (daemon *Daemon) ContainerLogs(job *engine.Job) engine.Status {
 					logLine = fmt.Sprintf("%s %s", l.Created.Format(format), logLine)
 				}
 				if l.Stream == "stdout" && stdout {
-					fmt.Fprintf(job.Stdout, "%s", logLine)
+					io.WriteString(job.Stdout, logLine)
 				}
 				if l.Stream == "stderr" && stderr {
-					fmt.Fprintf(job.Stderr, "%s", logLine)
+					io.WriteString(job.Stderr, logLine)
 				}
+				l.Reset()
 			}
 		}
 	}