Add pages in/out/fault statistics (as read from vmstat)

mem/mem.go

@@ -84,6 +84,9 @@ type SwapMemoryStat struct {
 	UsedPercent float64 `json:"usedPercent"`
 	Sin         uint64  `json:"sin"`
 	Sout        uint64  `json:"sout"`
+	PgIn        uint64  `json:"pgin"`
+	PgOut       uint64  `json:"pgout"`
+	PgFault     uint64  `json:"pgfault"`
 }
 
 func (m VirtualMemoryStat) String() string {

mem/mem_linux.go

@@ -177,6 +177,24 @@ func SwapMemoryWithContext(ctx context.Context) (*SwapMemoryStat, error) {
 				continue
 			}
 			ret.Sout = value * 4 * 1024
+		case "pgpgin":
+			value, err := strconv.ParseUint(fields[1], 10, 64)
+			if err != nil {
+				continue
+			}
+			ret.PgIn = value * 4 * 1024
+		case "pgpgout":
+			value, err := strconv.ParseUint(fields[1], 10, 64)
+			if err != nil {
+				continue
+			}
+			ret.PgOut = value * 4 * 1024
+		case "pgfault":
+			value, err := strconv.ParseUint(fields[1], 10, 64)
+			if err != nil {
+				continue
+			}
+			ret.PgFault = value * 4 * 1024
 		}
 	}
 	return ret, nil

mem/mem_test.go

@@ -89,8 +89,13 @@ func TestSwapMemoryStat_String(t *testing.T) {
 		Used:        30,
 		Free:        40,
 		UsedPercent: 30.1,
+		Sin:         1,
+		Sout:        2,
+		PgIn:        3,
+		PgOut:       4,
+		PgFault:     5,
 	}
-	e := `{"total":10,"used":30,"free":40,"usedPercent":30.1,"sin":0,"sout":0}`
+	e := `{"total":10,"used":30,"free":40,"usedPercent":30.1,"sin":1,"sout":2,"pgin":3,"pgout":4,"pgfault":5}`
 	if e != fmt.Sprintf("%v", v) {
 		t.Errorf("SwapMemoryStat string is invalid: %v", v)
 	}