测试跑的Q4 还是无法模拟出 I/O 性能瓶颈，依然是要加了 --device-write-iops --device-read-iops 限制后才可以。

[root@centos-7 ~]# docker run --privileged --name=app -itd feisky/app:iowait /app -d /dev/sda -s 67108864 -c 20
e7a7deddba3d2845030515fbbe25785382306d3c600c474a22de54d543a2cf53
[root@centos-7 ~]# docker logs app
Reading data from disk /dev/sdb with buffer size 67108864 and count 20

# 内核cpu时间sy，软中断cpu时间si升高明显
top - 00:15:15 up 12 min, 2 users, load average: 23.50, 7.07, 2.49
Tasks: 148 total, 43 running, 104 sleeping, 1 stopped, 0 zombie
%Cpu0 : 21.1 us, 54.9 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 24.0 si, 0.0 st
%Cpu1 : 21.8 us, 76.8 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 1.4 si, 0.0 st
KiB Mem : 3880792 total, 737592 free, 2880084 used, 263116 buff/cache
KiB Swap: 0 total, 0 free, 0 used. 764308 avail Mem

# docker run --privileged --name=app -itd --device-write-iops /dev/sda:3 --device-read-iops /dev/sda:3 feisky/app:iowait /app -d /dev/sda -s 67108864 -c

As a default, percentages for these individual categories are displayed. Where two labels are shown below, those for more recent kernel versions are shown first.
           us, user : time running un-niced user processes
           sy, system : time running kernel processes
           ni, nice : time running niced user processes
           id, idle : time spent in the kernel idle handler
           wa, IO-wait : time waiting for I/O completion
           hi : time spent servicing hardware interrupts
           si : time spent servicing software interrupts
           st : time stolen from this vm by the hypervisor