BFQ is a proportional-share disk scheduling algorithm that also supports hierarchical scheduling with a cgroups interface. One of the nice features of BFQ is that, according to our results on rotational disks, whatever the load is, the disk is virtually as responsive as if it was idle. For example, even if one ore more large files are being read or written, starting a command/application takes about the same time as if the disk was idle. Similarly, audio and video playing/streaming does not suffer from any glitch. At the same time, BFQ achieves up to 30% higher throughput than CFQ with most workloads. As for long-term guarantees, it distributes the disk throughput as desired to disk-bound applications, with any workload and independently of the disk parameters.
BFQ can be found in distributions as Arch Linux, Gentoo Linux and Sabayon. I have also recorded downloads from people using other distributions as, e.g., Ubuntu, Mandriva and ArchLinux. Besides, BFQ is used in the Zen Kernel as the default disk scheduler. Finally, the CyanogenMod distribution of Android switched to BFQ too. In the end, BFQ should be exposed to a userbase in the order of 200-300K users. So far, the users that gave us feedback confirmed the expected latency drop and throughput boost in daily usage.
In these pages you can find a brief description of the properties of BFQ and of how it works, together with the scheduler interface, the available tunables and the TODO list. You can download the sources, and see some benchmark results. Finally, there is a comparison with other production and research schedulers, including a thorough performance evaluation, carried out using an older implementation of BFQ.
Note
I work on BFQ in my spare time and with personal resources. In this way it
is very hard to thoroughly test it on a wide range of devices, and to keep the
pace with new hardware, new features (constantly) added to CFQ, and
new kernel versions. So, any proposal, information or suggestion on how to
find resources is welcome (interested organizations, research projects,
...).
Or, if you have enjoyed the benefits of BFQ and want to contribute to this free
project, you can help by donating through PayPal:
