What:		/proc/diskstats
Date:		February 2008
Contact:	Jerome Marchand <jmarchan@redhat.com>
Description:
		The /proc/diskstats file displays the I/O statistics
		of block devices. Each line contains the following 14
		fields:

		 1 - major number
		 2 - minor mumber
		 3 - device name
		 4 - reads completed successfully
		 5 - reads merged
		 6 - sectors read
		 7 - time spent reading (ms)
		 8 - writes completed
		 9 - writes merged
		10 - sectors written
		11 - time spent writing (ms)
		12 - I/Os currently in progress
		13 - time spent doing I/Os (ms)
		14 - weighted time spent doing I/Os (ms)

		Kernel 4.18+ appends four more fields for discard
		tracking putting the total at 18:

		15 - discards completed successfully
		16 - discards merged
		17 - sectors discarded
		18 - time spent discarding

		Kernel 5.5+ appends two more fields for flush requests:

		19 - flush requests completed successfully
		20 - time spent flushing

		For more details refer to Documentation/admin-guide/iostats.rst