BFQ is a proportional-share storage-I/O scheduler that also supports hierarchical scheduling with a cgroups interface. Here are the main nice features of BFQ.
- Low latency for interactive applications
to our results, whatever the background load
is, for interactive tasks the
storage device is virtually as responsive as if it was idle. For example, even
if one or more of the following background workloads are being
served in parallel:
- one or more large files are being read or written,
- a tree of source files is being compiled,
- one or more virtual machines are performing I/O,
- a software update is in progress,
- indexing daemons are scanning the filesystems and updating their databases,
- Low latency for soft real-time applications
- Also soft real-time applications, such as audio and video players or audio audio- and video-streaming applications, enjoy about the same latencies regardless of the device load. As a consequence, these applications do not suffer from almost any glitch due to the background workload.
- High throughput
- BFQ achieves up to 30% higher throughput than CFQ on hard disks with most parallel workloads, and about the same throughput with the rest of the workloads we have considered. BFQ achieves the same throughput as CFQ, NOOP, DEADLINE and SIO on SSDs.
- Strong fairness guarantees
- As for long-term guarantees, BFQ distributes the throughput as desired to I/O-bound applications (and not just the device time), with any workload and independently of the device parameters..
Systems adopting BFQ
BFQ is the default I/O scheduler in Sabayon, as well as in the Zen Kernel, the pf-kernel and several kernels for smartphones. BFQ is instead optionally available in Arch Linux and Gentoo Linux. We record a few tens of downloads per day from people using other distributions as well. So far, the users that gave us feedback confirmed the expected latency drop and throughput boost in everyday use.
Content of this site
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 (plus links to various technical reports). You can download the sources, and see some of the results we have obtained using an ad hoc benchmark suite. Finally, there is a comparison with other production and research schedulers, including a thorough performance evaluation, carried out using an old implementation of BFQ.
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