Re: [PATCH 00/14] introduce the BFQ-v0 I/O scheduler as an extra scheduler

[Christoph Hellwig]

On Wed, Oct 26, 2016 at 05:13:07PM +0200, Arnd Bergmann wrote:
> The question to ask first is whether to actually have pluggable
> schedulers on blk-mq at all, or just have one that is meant to
> do the right thing in every case (and possibly can be bypassed
> completely).

That would be my preference.  Have a BFQ-variant for blk-mq as an
option (default to off unless opted in by the driver or user), and
not other scheduler for blk-mq.  Don't bother with bfq for non
blk-mq.  It's not like there is any advantage in the legacy-request
device even for slow devices, except for the option of having I/O
scheduling.