Re: [PATCH RFC] block, bfq: set default slice_idle to zero for non-rotational devices

[Holger HoffstÃtte]

On 11/01/18 18:43, Konstantin Khlebnikov wrote:
> With default 8ms idle slice BFQ is up to 10 times slower than CFQ
> for massive random read workloads for common SATA SSD.
>
> For now zero idle slice gives better out of box experience.
> CFQ employs this since commit 41c0126b3f22 ("block: Make CFQ default
> to IOPS mode on SSDs")

Well, that's interesting because 3 years ago I made the same suggestion
and was told that BFQ's heuristics automagically make it not idle when
rotational=0. Did you actually benchmark this? I just tried and don't
get a noticeable performance difference with slice_idle=0 compared to
deadline.

Discussion link:
https://groups.google.com/forum/#!msg/bfq-iosched/iRMw2n3kYLY/6l9cIm3TBgAJ

curious..

Holger