[process io][linux] add ReadChars and WriteChars to IOCounterStat, collected from /proc/${pid}/io rchar and wchar

process/process.go

@@ -70,6 +70,8 @@ type IOCountersStat struct {
 	WriteCount uint64 `json:"writeCount"`
 	ReadBytes  uint64 `json:"readBytes"`
 	WriteBytes uint64 `json:"writeBytes"`
+	ReadChars  uint64 `json:"readChars"`
+	WriteChars uint64 `json:"writeChars"`
 }
 
 type NumCtxSwitchesStat struct {

process/process_linux.go

@@ -950,6 +950,10 @@ func (p *Process) fillFromIOWithContext(ctx context.Context) (*IOCountersStat, e
 			ret.ReadBytes = t
 		case "write_bytes":
 			ret.WriteBytes = t
+		case "rchar":
+			ret.ReadChars = t
+		case "wchar":
+			ret.WriteChars = t
 		}
 	}