Well subinterface do not show all things which you expect..like crc,input/output traffic etc. For that you have to look
into main interface.
But if you want to see traffic input/output you can apply qos or simply rate-limit and see traffic via.
If qos is applied: sh policy-map interface interface-name
If rate-limit is applied: sh interface interface-name rate-limit
if you have gig port with 50mb of bw you can apply rate milit like
rate-limit input 51200000 9600000 19200000 conform-action transmit exceed-action drop
rate-limit output 51200000 9600000 19200000 conform-action transmit exceed-action drop
Hope this is helpful