What is InnoDB Reading and Writing when It's Idle?

[Authorized User]

We ran the Sysbench tool to prepare a server to be benchmarked. Some time after the preparation completed, we observed that MySQL is still reading and writing. What is it doing and why does it take so long to quiet down?

Total DISK READ : 0.00 B/s | Total DISK WRITE : 2.97 M/s
Actual DISK READ: 0.00 B/s | Actual DISK WRITE: 7.69 M/s
TID PRIO USER DISK READ DISK WRITE> SWAPIN IO COMMAND
3016195 be/4 mysql 0.00 B/s 487.08 K/s 0.00 % 0.00 % mysqld
3016203 be/4 mysql 0.00 B/s 365.31 K/s 0.00 % 0.00 % mysqld
3016198 be/4 mysql 0.00 B/s 350.09 K/s 0.00 % 0.00 % mysqld
3016196 be/4 mysql 0.00 B/s 304.43 K/s 0.00 % 0.00 % mysqld
3016204 be/4 mysql 0.00 B/s 304.43 K/s 0.00 % 0.00 % mysqld
3016200 be/4 mysql 0.00 B/s 289.21 K/s 0.00 % 0.00 % mysqld
3016202 be/4 mysql 0.00 B/s 273.98 K/s 0.00 % 0.00 % mysqld
3016197 be/4 mysql 0.00 B/s 258.76 K/s 0.00 % 0.00 % mysqld
3016199 be/4 mysql 0.00 B/s 243.54 K/s 0.00 % 0.00 % mysqld
3016201 be/4 mysql 0.00 B/s 167.43 K/s 0.00 % 0.00 % mysqld

According to sysdig, it is still reading/writing files that sysbench created during its preparation, but the prep finished like 5-10 minutes ago, and binlogs are disabled.

Bytes Filename
--------------------------------------------------------------------------------
3.12M /zpool0/sysbench/data/sysbench/stock5.ibd
562B /dev/ptmx
512B /zpool0/sysbench/log/ib_logfile0
176B /proc/2392022/stat
176B /proc/2391981/stat
176B /proc/2391995/stat
176B /proc/2391990/stat
176B /proc/2392041/stat
176B /proc/2391984/stat
176B /proc/2391998/stat