I/O scheduling for single-queue devices

Block I/O performance can be one of the determining factors for the performance of a system as a whole, especially on systems with slower drives. The need to optimize I/O patterns has led to the development of a long series of I/O schedulers over the years; one of the most recent of those is BFQ, which was merged during the 4.12 development cycle. BFQ incorporates an impressive set of heuristics designed to improve interactive performance, but it has, thus far, seen relatively little uptake in deployed systems. An attempt to make BFQ the default I/O scheduler for some types of storage devices has raised some interesting questions, though, on how such decisions should be made.

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