On Wed, 2018-10-03 at 08:29 +0200, Paolo Valente wrote:

[1] https://lkml.org/lkml/2017/2/21/791
[2] http://algo.ing.unimo.it/people/paolo/disk_sched/results.php
[3] https://lwn.net/Articles/763603/

From [2]: "BFQ loses about 18% with only random readers, because the number

of IOPS becomes so high that the execution time and parallel efficiency of
the schedulers becomes relevant." Since the number of I/O patterns for which
results are available on [2] is limited and since the number of devices for
which test results are available on [2] is limited (e.g. RAID is missing),
there might be other cases in which configuring BFQ as the default would
introduce a regression.

I agree with Jens that it's best to leave it to the Linux distributors to
select a default I/O scheduler.

Bart.