Optimize disabled logging

README.md

@@ -16,7 +16,7 @@ All operations are allocation free (those numbers *include* JSON encoding):
 
 ```
 BenchmarkLogEmpty-8            50000000      22 ns/op       0 B/op      0 allocs/op
-BenchmarkDisabled-8           100000000      10 ns/op       0 B/op      0 allocs/op
+BenchmarkDisabled-8           100000000       9 ns/op       0 B/op      0 allocs/op
 BenchmarkInfo-8                10000000     210 ns/op       0 B/op      0 allocs/op
 BenchmarkContextFields-8       10000000     254 ns/op       0 B/op      0 allocs/op
 BenchmarkLogFields-8            5000000     377 ns/op       0 B/op      0 allocs/op

log.go

@@ -69,6 +69,7 @@ package zerolog
 
 import (
 	"io"
+	"io/ioutil"
 	"os"
 	"sync/atomic"
 )
@@ -124,6 +125,8 @@ const (
 	Rarely = 1000
 )
 
+var disabledEvent = newEvent(levelWriterAdapter{ioutil.Discard}, 0, false)
+
 // A Logger represents an active logging object that generates lines
 // of JSON output to an io.Writer. Each logging operation makes a single
 // call to the Writer's Write method. There is no guaranty on access
@@ -248,11 +251,15 @@ func (l Logger) Log() Event {
 }
 
 func (l Logger) newEvent(level Level, addLevelField bool, done func(string)) Event {
+	enabled := l.should(level)
+	if !enabled {
+		return disabledEvent
+	}
 	lvl := InfoLevel
 	if addLevelField {
 		lvl = level
 	}
-	e := newEvent(l.w, lvl, l.should(level))
+	e := newEvent(l.w, lvl, enabled)
 	if addLevelField {
 		e.Str(LevelFieldName, level.String())
 	}