[$] Improving the performance of the BFQ I/O scheduler

BFQ
is a proportional-share I/O scheduler available for block
devices since the 4.12 kernel release. It associates each process or group
of processes with a weight, and
grants a fraction of the available I/O bandwidth
proportional
to that weight. BFQ also tries
to maximize system responsiveness and to minimize latency for
time-sensitive applications. Finally, BFQ aims at boosting
throughput and at running efficiently. A new set of changes has improved
BFQ’s performance with respect to all of these criteria. In
particular, they increase the throughput that BFQ reaches
while handling the most challenging workloads for this I/O scheduler. A
notable example is DBENCH
workloads, for which BFQ now provides 150% more throughput. These
changes also improve BFQ’s I/O control — applications start about 80% more
quickly under load — and BFQ itself now runs about 10% faster.