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)
