part_round_stats(9) centos man page | unix.com

PART_ROUND_STATS(9)						   Block Devices					       PART_ROUND_STATS(9)

NAME
       part_round_stats - Round off the performance stats on a struct disk_stats.

SYNOPSIS
       void part_round_stats(int cpu, struct hd_struct * part);

ARGUMENTS
       cpu
	   cpu number for stats access

       part
	   target partition

DESCRIPTION
       The average IO queue length and utilisation statistics are maintained by observing the current state of the queue length and the amount of
       time it has been in this state for.

       Normally, that accounting is done on IO completion, but that can result in more than a second's worth of IO being accounted for within any
       one second, leading to >100% utilisation. To deal with that, we call this function to do a round-off before returning the results when
       reading /proc/diskstats. This accounts immediately for all queue usage up to the current jiffies and restarts the counters again.

COPYRIGHT
Kernel Hackers Manual 3.10					     June 2014						       PART_ROUND_STATS(9)