[process]: Introduce DiskReadBytes on process which shows Disk IO only.

process/process.go

@@ -103,10 +103,18 @@ type RlimitStat struct {
 }
 
 type IOCountersStat struct {
-	ReadCount  uint64 `json:"readCount"`
+	// ReadCount is a number of read I/O operations such as syscalls.
+	ReadCount uint64 `json:"readCount"`
+	// WriteCount is a number of read I/O operations such as syscalls.
 	WriteCount uint64 `json:"writeCount"`
-	ReadBytes  uint64 `json:"readBytes"`
+	// ReadBytes is a number of all I/O read in bytes. This includes disk I/O on Linux and Windows.
+	ReadBytes uint64 `json:"readBytes"`
+	// WriteBytes is a number of all I/O write in bytes. This includes disk I/O on Linux and Windows.
 	WriteBytes uint64 `json:"writeBytes"`
+	// DiskReadBytes is a number of disk I/O write in bytes. Currently only Linux has this value.
+	DiskReadBytes uint64 `json:"diskReadBytes"`
+	// DiskWriteBytes is a number of disk I/O read in bytes.  Currently only Linux has this value.
+	DiskWriteBytes uint64 `json:"diskWriteBytes"`
 }
 
 type NumCtxSwitchesStat struct {

process/process_linux.go

@@ -727,8 +727,12 @@ func (p *Process) fillFromIOWithContext(ctx context.Context) (*IOCountersStat, e
 		case "syscw":
 			ret.WriteCount = t
 		case "read_bytes":
-			ret.ReadBytes = t
+			ret.DiskReadBytes = t
 		case "write_bytes":
+			ret.DiskWriteBytes = t
+		case "rchar":
+			ret.ReadBytes = t
+		case "wchar":
 			ret.WriteBytes = t
 		}
 	}