AIX Disk I/O Perfstat Test Code

Test code for investigating wierd constant read stats on AIX.

Example from PowerVS AIX 7.3

# ./test
hdisk0 => reads [ blocks:    1207502, bytes  618241024, diff        0 ], writes [ blocks:      93033, bytes:   47632896, diff:        0 ]
hdisk0 => reads [ blocks:    1211712, bytes  620396544, diff  2155520 ], writes [ blocks:      93105, bytes:   47669760, diff:    36864 ]
hdisk0 => reads [ blocks:    1215922, bytes  622552064, diff  2155520 ], writes [ blocks:      93185, bytes:   47710720, diff:    40960 ]
hdisk0 => reads [ blocks:    1220132, bytes  624707584, diff  2155520 ], writes [ blocks:      93625, bytes:   47936000, diff:   225280 ]
hdisk0 => reads [ blocks:    1224342, bytes  626863104, diff  2155520 ], writes [ blocks:      93697, bytes:   47972864, diff:    36864 ]
hdisk0 => reads [ blocks:    1228560, bytes  629022720, diff  2159616 ], writes [ blocks:      93777, bytes:   48013824, diff:    40960 ]
hdisk0 => reads [ blocks:    1232770, bytes  631178240, diff  2155520 ], writes [ blocks:      93849, bytes:   48050688, diff:    36864 ]
hdisk0 => reads [ blocks:    1236980, bytes  633333760, diff  2155520 ], writes [ blocks:      93921, bytes:   48087552, diff:    36864 ]