monitor: optimize cpu costs

unicode.IsSpace is expensive

tcpmon/cmd_ss.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"strings"
 	"time"
-	"unicode"
 
 	"github.com/cockroachdb/errors"
 	"github.com/go-cmd/cmd"
@@ -249,9 +248,7 @@ func ParseSSOutput(t *TcpMetric, out []string) {
 
 	s := &SocketMetric{}
 	for _, line := range out {
-		fields := strings.FieldsFunc(line, func(c rune) bool {
-			return unicode.IsSpace(c)
-		})
+		fields := strings.FieldsFunc(line, SplitSpace)
 
 		var exist bool
 		if len(fields) == 0 {

tcpmon/util.go

@@ -114,12 +114,10 @@ func FileExists(s string) (bool, error) {
 	return true, nil
 }
 
-var SplitSpace = SplitChar(' ')
-
-var SplitNewline = SplitChar('\n')
+func SplitNewline(c rune) bool {
+	return c == '\n'
+}
 
-func SplitChar(s rune) func(rune) bool {
-	return func(c rune) bool {
-		return c == s
-	}
+func SplitSpace(c rune) bool {
+	return c == '\n' || c == '\r' || c == '\t' || c == ' '
 }