fsperf

fsperf is a performance testing framework built around fio. The goal is to provide a simple to run framework for file system developers to be able to check their patches and make sure they do not regress in performance. In addition to fio tests, fsperf supports basic timing tests and dbench tests.

Requirements

The following python packages are required:

• alembic
• SQLAlchemy
• sqlalchemy-migrate
• texttable
• psutil
• jinja2
• matplotlib
• numpy

For fragmentation analysis (-F), rust is required. Run cargo build -r in src/frag/ and it will pull the necessary dependencies. In addition, btrd is required to be installed on PATH to collect btrfs bg/extent data.

Configuration

In order to configure the suite you need to create a local.cfg file in the base of the fsperf directory. This file takes the format normal INI files. You must specify a [main] section with the following required options

• directory - the directory to run the performance jobs in.
• cpugovernor - the cpu governor to use for the run.

Then subsequently you must specify configs, which whatever name you wish to use. These take the following optional options

• mkfs - if specified this will be run between every test. This is the full mkfs command needed for your test environment.
• mount - the command to mount the fs. If specified the fs will be unmounted between each test.
• device - the device that will be used for this section.
• iosched - Must match one of the options in /sys/block/{device}/queue/scheduler.

[main]
directory=/mnt/test

[btrfs]
device=/dev/nvme0n1
mkfs=mkfs.btrfs -f
mount=mount -o noatime

You can specify multiple configurations per file, and switch between them with the -c option for fsperf.

How to run

Once you've setup your local.cfg you simply run

./fsperf

and wait for the suite to finish. This will run the tests found under the tests/ directory and store the results. The blank invocation is meant for continuous performance testing.

A/B testing

If you wish to do A/B testing you can do the following

./fsperf -p "myabtest"
<make changes>
./fsperf -p "myabtest" -t
./fsperf-clean-results myabtest

This will store the base results under a specific heading, "myabtest", so it doesn't muddy any other unrelated performance results. Then using the -t option it will run the tests, and spit out a comparison table between the baseline and the current run, and then discard the current run's results in order to not pollute the baseline results.

The comparison compares all of the saved results, so things like fio's max latencies may be a little noisy. In order to reduce the noise of these sort of metrics you can do something like the following

./fsperf -p "myabtest" -n 5
<make changes>
./fsperf -p "myabtest" -n 5 -t
./fsperf-clean-results myabtest

This will run each test 5 times, which means the baseline and new results will be averaged, and then the averages will be compared against eachother.

Finally the fsperf-clean-results script will delete anything that matches your special results, so you can re-use the label in the future.

Understanding the comparisons

We only compare the last run of the given test with the given configuration. So if you have multiple sections in your configuration file, such as the following

[btrfs]
device=/dev/nvme0n1
mkfs=mkfs.btrfs -f
mount=mount -o noatime

[xfs]
device=/dev/nvme0n1
iosched=none
mkfs=mkfs.xfs -f
mount=mount -o noatime

Only tests in the same configuration will be compared against each other. Future work will include the ability to compare with other configurations, but currently you can just change your local.cfg if you wish to compare runs of different configurations.

Disabling tests

Sometimes you may need to disable a test, so simply add the test name to it's own line in the disabled-tests file in the root of the project directory.

Fragmentation tests

A second set of tests which challenge the btrfs block_group/extent allocator are found in frag_tests/. Running fsperf with -F will add them to the list of eligible tests to run.