Add 'SwapCached' to the VirtualMemoryStat informations on linux

mem/mem.go

@@ -57,6 +57,7 @@ type VirtualMemoryStat struct {
 	Shared       uint64 `json:"shared"`
 	Slab         uint64 `json:"slab"`
 	PageTables   uint64 `json:"pagetables"`
+	SwapCached   uint64 `json:"swapcached"`
 }
 
 type SwapMemoryStat struct {

mem/mem_linux.go

@@ -58,6 +58,8 @@ func VirtualMemory() (*VirtualMemoryStat, error) {
 			ret.Slab = t * 1024
 		case "PageTables":
 			ret.PageTables = t * 1024
+		case "SwapCached":
+			ret.SwapCached = t * 1024
 		}
 	}
 	if !memavail {

mem/mem_test.go

@@ -52,7 +52,7 @@ func TestVirtualMemoryStat_String(t *testing.T) {
 		UsedPercent: 30.1,
 		Free:        40,
 	}
-	e := `{"total":10,"available":20,"used":30,"usedPercent":30.1,"free":40,"active":0,"inactive":0,"wired":0,"buffers":0,"cached":0,"writeback":0,"dirty":0,"writebacktmp":0,"shared":0,"slab":0,"pagetables":0}`
+	e := `{"total":10,"available":20,"used":30,"usedPercent":30.1,"free":40,"active":0,"inactive":0,"wired":0,"buffers":0,"cached":0,"writeback":0,"dirty":0,"writebacktmp":0,"shared":0,"slab":0,"pagetables":0,"swapcached":0}`
 	if e != fmt.Sprintf("%v", v) {
 		t.Errorf("VirtualMemoryStat string is invalid: %v", v)
 	}