Track I/O latency

/proc/diskstats interface

The /proc/diskstats interface in Alibaba Cloud Linux 2 allows you to query the I/O information on a disk and the amount of time consumed by read, write, and discard operations on a device.

Run the following command to query the /proc/diskstats interface:

cat /proc/diskstats

The following command output is returned:

254       0 vda 6328 3156 565378 2223 1610 424 25160 4366 0 1358 5332 0 0 0 0 2205 3347 0

In the command output, the last three fields are new fields in Alibaba Cloud Linux 2. The following table describes all fields.

Install and use the BCC toolset

Alibaba Cloud Linux 2 provides the BCC toolset to track I/O latency.

1. Run the following command to download the BCC toolset:

   yum install -y bcc-tools

2. Run one of the following commands to query the description of the BCC toolset:

   • Run the following command to query the description of the BCC toolset:

     /usr/share/bcc/tools/alibiolatency -h

     Sample description:

     usage: alibiolatency [-h] [-d DEVICE] [-i [DIS_INTERVAL]]
                          [-t [AVG_THRESHOLD_TIME]] [-T [THRESHOLD_TIME]] [-r]
     
     Summarize block device I/O latency
     
     optional arguments:
       -h, --help            show this help message and exit
       -d DEVICE, --device DEVICE
                             inspect specified device
       -i [DIS_INTERVAL], --dis_interval [DIS_INTERVAL]
                             specify display interval
       -t [AVG_THRESHOLD_TIME], --avg_threshold_time [AVG_THRESHOLD_TIME]
                             display only when average request process time is
                             greater than this value
       -T [THRESHOLD_TIME], --threshold_time [THRESHOLD_TIME]
                             dump request life cycle when single request process
                             time is greater than this value
       -r, --dump_raw        dump every io request life cycle
     
     examples:
         ./alibiolatency          # summarize block I/O latency(default display interval is 2s)
         ./alibiolatency -d sda3  # inspect specified device /dev/sda3
         ./alibiolatency -i 2     # specify display interval, 2s
         ./alibiolatency -t 10    # display only when average request process time is greater than 10ms
         ./alibiolatency -T 20    # dump request life cycle when single request process time is greater than 20ms
         ./alibiolatency -r       # dump every io request life cycle

   • Run the man command to query the description of the BCC toolset.

     man bcc-alibiolatency