About

This is a kernel-based IO benchmark.

KIO is similar (in spirit) to fio but runs entierly in the kernel. This removes any user space and queuing overhead, and measures just the device driver + hardware.

This code is provided under the GPLv2 license.

TL;DR

Quick run:

$ make
$ ./kio.py --num-threads 1 \
        --runtime 5 \
        --block-size 4096 \
        --offset-stride 4096 \
        --queue-depth 10 \
        --offset-random 1 \
        --read-mix-percent 100 \
        --offset-high $((0xFFFFFFFF)) \
        --read-burst 100 \
        --read-mix-percent 100
...
-   bw_MBps: 299.211
    clat_usec: 129.876
    completed: 373186
    iops: 73049.0
    lat_usec: 133.03
    slat_usec: 3.154
...

Usage

Build

To build the system must have a compiler tools and kernel headers.

$ ./dependencies.sh
$ make

Running kio.py

This is a helper script that manages configuration files and generates reports.

$ ./kio.py --num-threads 2 \
        --runtime 5 \
        --block-size 4096 \
        --queue-depth 10 \
        --offset-random 1 \
        --read-mix-percent 100 \
        --offset-high $((0xFFFFFFFF)) \
        --read-burst 100 \
        --read-mix-percent 100
...
-   bw_MBps: 159.743
    clat_usec: 250.313
    completed: 398666
    iops: 19499.0
    lat_usec: 253.18
    slat_usec: 2.867
-   0:
        bw_MBps: 159.734
        clat_usec: 249.932
        completed: 199319
        iops: 38997.0
        lat_usec: 252.695
        slat_usec: 2.763
    1:
        bw_MBps: 159.752
        clat_usec: 250.695
        completed: 199347
        iops: 39002.0
        lat_usec: 253.666
        slat_usec: 2.971

It is also possible to generate a config, edit it, and then run from the config.

$ ./kio.py --num-threads 2 --runtime 5 --generate-config kio.conf
$ vim kio.conf
$ ./kio.py --config kio.conf

kio.py can generate reports in YAML format:

$ ./kio.py --config kio.conf --output-yaml report.yaml

Lastly, kio.py can be made to append to the same CVS file:

$ ./kio.py --config kio.conf --read-mix-percent 100 --output-csv report.yaml
$ ./kio.py --config kio.conf --read-mix-percent 50 --output-csv report.yaml
$ ./kio.py --config kio.conf --read-mix-percent 0 --output-csv report.yaml

Running manually

The configuration allows for setting various attributes through sysfs. See test.sh for an example.

You can have multiple threads, but you must configure each separately.

A few settings have restrictions. See Limitations at the bottom.

Results

A result (in dmesg) may look like this:

[4930136.204979] kio: thread[0]: completed=382413 lat=133.130(2.729+130.401) iops=73640 MB/s=301.633
[4930136.205920] kio: summary: completed=382413 lat=133.130(2.729+130.401) iops=73640 MB/s=301.633

Latencies, IOPS, and bandwidth are reported as averages.

Latency is reported in microseconds (usec), and is split into submission latency and completion latency.

Limitations

• only tested on Ubuntu 18.04 kernel 4.15.0
• num_threads can only be set once; must reload driver to change it.
• block_size only 4096 is currently supported.